1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // InstructionCombining - Combine instructions to form fewer, simple
11 // instructions. This pass does not modify the CFG This pass is where algebraic
12 // simplification happens.
14 // This pass combines things like:
20 // This is a simple worklist driven algorithm.
22 // This pass guarantees that the following canonicalizations are performed on
24 // 1. If a binary operator has a constant operand, it is moved to the RHS
25 // 2. Bitwise operators with constant operands are always grouped so that
26 // shifts are performed first, then or's, then and's, then xor's.
27 // 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All cmp instructions on boolean values are replaced with logical ops
29 // 5. add X, X is represented as (X*2) => (X << 1)
30 // 6. Multiplies with a power-of-two constant argument are transformed into
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/IntrinsicInst.h"
39 #include "llvm/Pass.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/GlobalVariable.h"
42 #include "llvm/Analysis/ConstantFolding.h"
43 #include "llvm/Target/TargetData.h"
44 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 #include "llvm/Support/CallSite.h"
47 #include "llvm/Support/Debug.h"
48 #include "llvm/Support/GetElementPtrTypeIterator.h"
49 #include "llvm/Support/InstVisitor.h"
50 #include "llvm/Support/MathExtras.h"
51 #include "llvm/Support/PatternMatch.h"
52 #include "llvm/Support/Compiler.h"
53 #include "llvm/ADT/DenseMap.h"
54 #include "llvm/ADT/SmallVector.h"
55 #include "llvm/ADT/SmallPtrSet.h"
56 #include "llvm/ADT/Statistic.h"
57 #include "llvm/ADT/STLExtras.h"
61 using namespace llvm::PatternMatch;
63 STATISTIC(NumCombined , "Number of insts combined");
64 STATISTIC(NumConstProp, "Number of constant folds");
65 STATISTIC(NumDeadInst , "Number of dead inst eliminated");
66 STATISTIC(NumDeadStore, "Number of dead stores eliminated");
67 STATISTIC(NumSunkInst , "Number of instructions sunk");
70 class VISIBILITY_HIDDEN InstCombiner
71 : public FunctionPass,
72 public InstVisitor<InstCombiner, Instruction*> {
73 // Worklist of all of the instructions that need to be simplified.
74 std::vector<Instruction*> Worklist;
75 DenseMap<Instruction*, unsigned> WorklistMap;
77 bool MustPreserveLCSSA;
79 static char ID; // Pass identification, replacement for typeid
80 InstCombiner() : FunctionPass((intptr_t)&ID) {}
82 /// AddToWorkList - Add the specified instruction to the worklist if it
83 /// isn't already in it.
84 void AddToWorkList(Instruction *I) {
85 if (WorklistMap.insert(std::make_pair(I, Worklist.size())))
86 Worklist.push_back(I);
89 // RemoveFromWorkList - remove I from the worklist if it exists.
90 void RemoveFromWorkList(Instruction *I) {
91 DenseMap<Instruction*, unsigned>::iterator It = WorklistMap.find(I);
92 if (It == WorklistMap.end()) return; // Not in worklist.
94 // Don't bother moving everything down, just null out the slot.
95 Worklist[It->second] = 0;
97 WorklistMap.erase(It);
100 Instruction *RemoveOneFromWorkList() {
101 Instruction *I = Worklist.back();
103 WorklistMap.erase(I);
108 /// AddUsersToWorkList - When an instruction is simplified, add all users of
109 /// the instruction to the work lists because they might get more simplified
112 void AddUsersToWorkList(Value &I) {
113 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
115 AddToWorkList(cast<Instruction>(*UI));
118 /// AddUsesToWorkList - When an instruction is simplified, add operands to
119 /// the work lists because they might get more simplified now.
121 void AddUsesToWorkList(Instruction &I) {
122 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
123 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
127 /// AddSoonDeadInstToWorklist - The specified instruction is about to become
128 /// dead. Add all of its operands to the worklist, turning them into
129 /// undef's to reduce the number of uses of those instructions.
131 /// Return the specified operand before it is turned into an undef.
133 Value *AddSoonDeadInstToWorklist(Instruction &I, unsigned op) {
134 Value *R = I.getOperand(op);
136 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
137 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i))) {
139 // Set the operand to undef to drop the use.
140 I.setOperand(i, UndefValue::get(Op->getType()));
147 virtual bool runOnFunction(Function &F);
149 bool DoOneIteration(Function &F, unsigned ItNum);
151 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
152 AU.addRequired<TargetData>();
153 AU.addPreservedID(LCSSAID);
154 AU.setPreservesCFG();
157 TargetData &getTargetData() const { return *TD; }
159 // Visitation implementation - Implement instruction combining for different
160 // instruction types. The semantics are as follows:
162 // null - No change was made
163 // I - Change was made, I is still valid, I may be dead though
164 // otherwise - Change was made, replace I with returned instruction
166 Instruction *visitAdd(BinaryOperator &I);
167 Instruction *visitSub(BinaryOperator &I);
168 Instruction *visitMul(BinaryOperator &I);
169 Instruction *visitURem(BinaryOperator &I);
170 Instruction *visitSRem(BinaryOperator &I);
171 Instruction *visitFRem(BinaryOperator &I);
172 Instruction *commonRemTransforms(BinaryOperator &I);
173 Instruction *commonIRemTransforms(BinaryOperator &I);
174 Instruction *commonDivTransforms(BinaryOperator &I);
175 Instruction *commonIDivTransforms(BinaryOperator &I);
176 Instruction *visitUDiv(BinaryOperator &I);
177 Instruction *visitSDiv(BinaryOperator &I);
178 Instruction *visitFDiv(BinaryOperator &I);
179 Instruction *visitAnd(BinaryOperator &I);
180 Instruction *visitOr (BinaryOperator &I);
181 Instruction *visitXor(BinaryOperator &I);
182 Instruction *visitShl(BinaryOperator &I);
183 Instruction *visitAShr(BinaryOperator &I);
184 Instruction *visitLShr(BinaryOperator &I);
185 Instruction *commonShiftTransforms(BinaryOperator &I);
186 Instruction *visitFCmpInst(FCmpInst &I);
187 Instruction *visitICmpInst(ICmpInst &I);
188 Instruction *visitICmpInstWithCastAndCast(ICmpInst &ICI);
189 Instruction *visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
192 Instruction *FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
193 ConstantInt *DivRHS);
195 Instruction *FoldGEPICmp(User *GEPLHS, Value *RHS,
196 ICmpInst::Predicate Cond, Instruction &I);
197 Instruction *FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
199 Instruction *commonCastTransforms(CastInst &CI);
200 Instruction *commonIntCastTransforms(CastInst &CI);
201 Instruction *commonPointerCastTransforms(CastInst &CI);
202 Instruction *visitTrunc(TruncInst &CI);
203 Instruction *visitZExt(ZExtInst &CI);
204 Instruction *visitSExt(SExtInst &CI);
205 Instruction *visitFPTrunc(CastInst &CI);
206 Instruction *visitFPExt(CastInst &CI);
207 Instruction *visitFPToUI(CastInst &CI);
208 Instruction *visitFPToSI(CastInst &CI);
209 Instruction *visitUIToFP(CastInst &CI);
210 Instruction *visitSIToFP(CastInst &CI);
211 Instruction *visitPtrToInt(CastInst &CI);
212 Instruction *visitIntToPtr(CastInst &CI);
213 Instruction *visitBitCast(BitCastInst &CI);
214 Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
216 Instruction *visitSelectInst(SelectInst &CI);
217 Instruction *visitCallInst(CallInst &CI);
218 Instruction *visitInvokeInst(InvokeInst &II);
219 Instruction *visitPHINode(PHINode &PN);
220 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
221 Instruction *visitAllocationInst(AllocationInst &AI);
222 Instruction *visitFreeInst(FreeInst &FI);
223 Instruction *visitLoadInst(LoadInst &LI);
224 Instruction *visitStoreInst(StoreInst &SI);
225 Instruction *visitBranchInst(BranchInst &BI);
226 Instruction *visitSwitchInst(SwitchInst &SI);
227 Instruction *visitInsertElementInst(InsertElementInst &IE);
228 Instruction *visitExtractElementInst(ExtractElementInst &EI);
229 Instruction *visitShuffleVectorInst(ShuffleVectorInst &SVI);
231 // visitInstruction - Specify what to return for unhandled instructions...
232 Instruction *visitInstruction(Instruction &I) { return 0; }
235 Instruction *visitCallSite(CallSite CS);
236 bool transformConstExprCastCall(CallSite CS);
239 // InsertNewInstBefore - insert an instruction New before instruction Old
240 // in the program. Add the new instruction to the worklist.
242 Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
243 assert(New && New->getParent() == 0 &&
244 "New instruction already inserted into a basic block!");
245 BasicBlock *BB = Old.getParent();
246 BB->getInstList().insert(&Old, New); // Insert inst
251 /// InsertCastBefore - Insert a cast of V to TY before the instruction POS.
252 /// This also adds the cast to the worklist. Finally, this returns the
254 Value *InsertCastBefore(Instruction::CastOps opc, Value *V, const Type *Ty,
256 if (V->getType() == Ty) return V;
258 if (Constant *CV = dyn_cast<Constant>(V))
259 return ConstantExpr::getCast(opc, CV, Ty);
261 Instruction *C = CastInst::create(opc, V, Ty, V->getName(), &Pos);
266 // ReplaceInstUsesWith - This method is to be used when an instruction is
267 // found to be dead, replacable with another preexisting expression. Here
268 // we add all uses of I to the worklist, replace all uses of I with the new
269 // value, then return I, so that the inst combiner will know that I was
272 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
273 AddUsersToWorkList(I); // Add all modified instrs to worklist
275 I.replaceAllUsesWith(V);
278 // If we are replacing the instruction with itself, this must be in a
279 // segment of unreachable code, so just clobber the instruction.
280 I.replaceAllUsesWith(UndefValue::get(I.getType()));
285 // UpdateValueUsesWith - This method is to be used when an value is
286 // found to be replacable with another preexisting expression or was
287 // updated. Here we add all uses of I to the worklist, replace all uses of
288 // I with the new value (unless the instruction was just updated), then
289 // return true, so that the inst combiner will know that I was modified.
291 bool UpdateValueUsesWith(Value *Old, Value *New) {
292 AddUsersToWorkList(*Old); // Add all modified instrs to worklist
294 Old->replaceAllUsesWith(New);
295 if (Instruction *I = dyn_cast<Instruction>(Old))
297 if (Instruction *I = dyn_cast<Instruction>(New))
302 // EraseInstFromFunction - When dealing with an instruction that has side
303 // effects or produces a void value, we can't rely on DCE to delete the
304 // instruction. Instead, visit methods should return the value returned by
306 Instruction *EraseInstFromFunction(Instruction &I) {
307 assert(I.use_empty() && "Cannot erase instruction that is used!");
308 AddUsesToWorkList(I);
309 RemoveFromWorkList(&I);
311 return 0; // Don't do anything with FI
315 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
316 /// InsertBefore instruction. This is specialized a bit to avoid inserting
317 /// casts that are known to not do anything...
319 Value *InsertOperandCastBefore(Instruction::CastOps opcode,
320 Value *V, const Type *DestTy,
321 Instruction *InsertBefore);
323 /// SimplifyCommutative - This performs a few simplifications for
324 /// commutative operators.
325 bool SimplifyCommutative(BinaryOperator &I);
327 /// SimplifyCompare - This reorders the operands of a CmpInst to get them in
328 /// most-complex to least-complex order.
329 bool SimplifyCompare(CmpInst &I);
331 /// SimplifyDemandedBits - Attempts to replace V with a simpler value based
332 /// on the demanded bits.
333 bool SimplifyDemandedBits(Value *V, APInt DemandedMask,
334 APInt& KnownZero, APInt& KnownOne,
337 Value *SimplifyDemandedVectorElts(Value *V, uint64_t DemandedElts,
338 uint64_t &UndefElts, unsigned Depth = 0);
340 // FoldOpIntoPhi - Given a binary operator or cast instruction which has a
341 // PHI node as operand #0, see if we can fold the instruction into the PHI
342 // (which is only possible if all operands to the PHI are constants).
343 Instruction *FoldOpIntoPhi(Instruction &I);
345 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
346 // operator and they all are only used by the PHI, PHI together their
347 // inputs, and do the operation once, to the result of the PHI.
348 Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
349 Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
352 Instruction *OptAndOp(Instruction *Op, ConstantInt *OpRHS,
353 ConstantInt *AndRHS, BinaryOperator &TheAnd);
355 Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
356 bool isSub, Instruction &I);
357 Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
358 bool isSigned, bool Inside, Instruction &IB);
359 Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocationInst &AI);
360 Instruction *MatchBSwap(BinaryOperator &I);
361 bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
363 Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
366 char InstCombiner::ID = 0;
367 RegisterPass<InstCombiner> X("instcombine", "Combine redundant instructions");
370 // getComplexity: Assign a complexity or rank value to LLVM Values...
371 // 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
372 static unsigned getComplexity(Value *V) {
373 if (isa<Instruction>(V)) {
374 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
378 if (isa<Argument>(V)) return 3;
379 return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
382 // isOnlyUse - Return true if this instruction will be deleted if we stop using
384 static bool isOnlyUse(Value *V) {
385 return V->hasOneUse() || isa<Constant>(V);
388 // getPromotedType - Return the specified type promoted as it would be to pass
389 // though a va_arg area...
390 static const Type *getPromotedType(const Type *Ty) {
391 if (const IntegerType* ITy = dyn_cast<IntegerType>(Ty)) {
392 if (ITy->getBitWidth() < 32)
393 return Type::Int32Ty;
398 /// getBitCastOperand - If the specified operand is a CastInst or a constant
399 /// expression bitcast, return the operand value, otherwise return null.
400 static Value *getBitCastOperand(Value *V) {
401 if (BitCastInst *I = dyn_cast<BitCastInst>(V))
402 return I->getOperand(0);
403 else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
404 if (CE->getOpcode() == Instruction::BitCast)
405 return CE->getOperand(0);
409 /// This function is a wrapper around CastInst::isEliminableCastPair. It
410 /// simply extracts arguments and returns what that function returns.
411 static Instruction::CastOps
412 isEliminableCastPair(
413 const CastInst *CI, ///< The first cast instruction
414 unsigned opcode, ///< The opcode of the second cast instruction
415 const Type *DstTy, ///< The target type for the second cast instruction
416 TargetData *TD ///< The target data for pointer size
419 const Type *SrcTy = CI->getOperand(0)->getType(); // A from above
420 const Type *MidTy = CI->getType(); // B from above
422 // Get the opcodes of the two Cast instructions
423 Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode());
424 Instruction::CastOps secondOp = Instruction::CastOps(opcode);
426 return Instruction::CastOps(
427 CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy,
428 DstTy, TD->getIntPtrType()));
431 /// ValueRequiresCast - Return true if the cast from "V to Ty" actually results
432 /// in any code being generated. It does not require codegen if V is simple
433 /// enough or if the cast can be folded into other casts.
434 static bool ValueRequiresCast(Instruction::CastOps opcode, const Value *V,
435 const Type *Ty, TargetData *TD) {
436 if (V->getType() == Ty || isa<Constant>(V)) return false;
438 // If this is another cast that can be eliminated, it isn't codegen either.
439 if (const CastInst *CI = dyn_cast<CastInst>(V))
440 if (isEliminableCastPair(CI, opcode, Ty, TD))
445 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
446 /// InsertBefore instruction. This is specialized a bit to avoid inserting
447 /// casts that are known to not do anything...
449 Value *InstCombiner::InsertOperandCastBefore(Instruction::CastOps opcode,
450 Value *V, const Type *DestTy,
451 Instruction *InsertBefore) {
452 if (V->getType() == DestTy) return V;
453 if (Constant *C = dyn_cast<Constant>(V))
454 return ConstantExpr::getCast(opcode, C, DestTy);
456 return InsertCastBefore(opcode, V, DestTy, *InsertBefore);
459 // SimplifyCommutative - This performs a few simplifications for commutative
462 // 1. Order operands such that they are listed from right (least complex) to
463 // left (most complex). This puts constants before unary operators before
466 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
467 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
469 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
470 bool Changed = false;
471 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
472 Changed = !I.swapOperands();
474 if (!I.isAssociative()) return Changed;
475 Instruction::BinaryOps Opcode = I.getOpcode();
476 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
477 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
478 if (isa<Constant>(I.getOperand(1))) {
479 Constant *Folded = ConstantExpr::get(I.getOpcode(),
480 cast<Constant>(I.getOperand(1)),
481 cast<Constant>(Op->getOperand(1)));
482 I.setOperand(0, Op->getOperand(0));
483 I.setOperand(1, Folded);
485 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
486 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
487 isOnlyUse(Op) && isOnlyUse(Op1)) {
488 Constant *C1 = cast<Constant>(Op->getOperand(1));
489 Constant *C2 = cast<Constant>(Op1->getOperand(1));
491 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
492 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
493 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
497 I.setOperand(0, New);
498 I.setOperand(1, Folded);
505 /// SimplifyCompare - For a CmpInst this function just orders the operands
506 /// so that theyare listed from right (least complex) to left (most complex).
507 /// This puts constants before unary operators before binary operators.
508 bool InstCombiner::SimplifyCompare(CmpInst &I) {
509 if (getComplexity(I.getOperand(0)) >= getComplexity(I.getOperand(1)))
512 // Compare instructions are not associative so there's nothing else we can do.
516 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
517 // if the LHS is a constant zero (which is the 'negate' form).
519 static inline Value *dyn_castNegVal(Value *V) {
520 if (BinaryOperator::isNeg(V))
521 return BinaryOperator::getNegArgument(V);
523 // Constants can be considered to be negated values if they can be folded.
524 if (ConstantInt *C = dyn_cast<ConstantInt>(V))
525 return ConstantExpr::getNeg(C);
529 static inline Value *dyn_castNotVal(Value *V) {
530 if (BinaryOperator::isNot(V))
531 return BinaryOperator::getNotArgument(V);
533 // Constants can be considered to be not'ed values...
534 if (ConstantInt *C = dyn_cast<ConstantInt>(V))
535 return ConstantInt::get(~C->getValue());
539 // dyn_castFoldableMul - If this value is a multiply that can be folded into
540 // other computations (because it has a constant operand), return the
541 // non-constant operand of the multiply, and set CST to point to the multiplier.
542 // Otherwise, return null.
544 static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
545 if (V->hasOneUse() && V->getType()->isInteger())
546 if (Instruction *I = dyn_cast<Instruction>(V)) {
547 if (I->getOpcode() == Instruction::Mul)
548 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
549 return I->getOperand(0);
550 if (I->getOpcode() == Instruction::Shl)
551 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
552 // The multiplier is really 1 << CST.
553 uint32_t BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
554 uint32_t CSTVal = CST->getLimitedValue(BitWidth);
555 CST = ConstantInt::get(APInt(BitWidth, 1).shl(CSTVal));
556 return I->getOperand(0);
562 /// dyn_castGetElementPtr - If this is a getelementptr instruction or constant
563 /// expression, return it.
564 static User *dyn_castGetElementPtr(Value *V) {
565 if (isa<GetElementPtrInst>(V)) return cast<User>(V);
566 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
567 if (CE->getOpcode() == Instruction::GetElementPtr)
568 return cast<User>(V);
572 /// AddOne - Add one to a ConstantInt
573 static ConstantInt *AddOne(ConstantInt *C) {
574 APInt Val(C->getValue());
575 return ConstantInt::get(++Val);
577 /// SubOne - Subtract one from a ConstantInt
578 static ConstantInt *SubOne(ConstantInt *C) {
579 APInt Val(C->getValue());
580 return ConstantInt::get(--Val);
582 /// Add - Add two ConstantInts together
583 static ConstantInt *Add(ConstantInt *C1, ConstantInt *C2) {
584 return ConstantInt::get(C1->getValue() + C2->getValue());
586 /// And - Bitwise AND two ConstantInts together
587 static ConstantInt *And(ConstantInt *C1, ConstantInt *C2) {
588 return ConstantInt::get(C1->getValue() & C2->getValue());
590 /// Subtract - Subtract one ConstantInt from another
591 static ConstantInt *Subtract(ConstantInt *C1, ConstantInt *C2) {
592 return ConstantInt::get(C1->getValue() - C2->getValue());
594 /// Multiply - Multiply two ConstantInts together
595 static ConstantInt *Multiply(ConstantInt *C1, ConstantInt *C2) {
596 return ConstantInt::get(C1->getValue() * C2->getValue());
599 /// ComputeMaskedBits - Determine which of the bits specified in Mask are
600 /// known to be either zero or one and return them in the KnownZero/KnownOne
601 /// bit sets. This code only analyzes bits in Mask, in order to short-circuit
603 /// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
604 /// we cannot optimize based on the assumption that it is zero without changing
605 /// it to be an explicit zero. If we don't change it to zero, other code could
606 /// optimized based on the contradictory assumption that it is non-zero.
607 /// Because instcombine aggressively folds operations with undef args anyway,
608 /// this won't lose us code quality.
609 static void ComputeMaskedBits(Value *V, const APInt &Mask, APInt& KnownZero,
610 APInt& KnownOne, unsigned Depth = 0) {
611 assert(V && "No Value?");
612 assert(Depth <= 6 && "Limit Search Depth");
613 uint32_t BitWidth = Mask.getBitWidth();
614 assert(cast<IntegerType>(V->getType())->getBitWidth() == BitWidth &&
615 KnownZero.getBitWidth() == BitWidth &&
616 KnownOne.getBitWidth() == BitWidth &&
617 "V, Mask, KnownOne and KnownZero should have same BitWidth");
618 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
619 // We know all of the bits for a constant!
620 KnownOne = CI->getValue() & Mask;
621 KnownZero = ~KnownOne & Mask;
625 if (Depth == 6 || Mask == 0)
626 return; // Limit search depth.
628 Instruction *I = dyn_cast<Instruction>(V);
631 KnownZero.clear(); KnownOne.clear(); // Don't know anything.
632 APInt KnownZero2(KnownZero), KnownOne2(KnownOne);
634 switch (I->getOpcode()) {
635 case Instruction::And: {
636 // If either the LHS or the RHS are Zero, the result is zero.
637 ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
638 APInt Mask2(Mask & ~KnownZero);
639 ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
640 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
641 assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
643 // Output known-1 bits are only known if set in both the LHS & RHS.
644 KnownOne &= KnownOne2;
645 // Output known-0 are known to be clear if zero in either the LHS | RHS.
646 KnownZero |= KnownZero2;
649 case Instruction::Or: {
650 ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
651 APInt Mask2(Mask & ~KnownOne);
652 ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, Depth+1);
653 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
654 assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
656 // Output known-0 bits are only known if clear in both the LHS & RHS.
657 KnownZero &= KnownZero2;
658 // Output known-1 are known to be set if set in either the LHS | RHS.
659 KnownOne |= KnownOne2;
662 case Instruction::Xor: {
663 ComputeMaskedBits(I->getOperand(1), Mask, KnownZero, KnownOne, Depth+1);
664 ComputeMaskedBits(I->getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1);
665 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
666 assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
668 // Output known-0 bits are known if clear or set in both the LHS & RHS.
669 APInt KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2);
670 // Output known-1 are known to be set if set in only one of the LHS, RHS.
671 KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2);
672 KnownZero = KnownZeroOut;
675 case Instruction::Select:
676 ComputeMaskedBits(I->getOperand(2), Mask, KnownZero, KnownOne, Depth+1);
677 ComputeMaskedBits(I->getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1);
678 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
679 assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
681 // Only known if known in both the LHS and RHS.
682 KnownOne &= KnownOne2;
683 KnownZero &= KnownZero2;
685 case Instruction::FPTrunc:
686 case Instruction::FPExt:
687 case Instruction::FPToUI:
688 case Instruction::FPToSI:
689 case Instruction::SIToFP:
690 case Instruction::PtrToInt:
691 case Instruction::UIToFP:
692 case Instruction::IntToPtr:
693 return; // Can't work with floating point or pointers
694 case Instruction::Trunc: {
695 // All these have integer operands
696 uint32_t SrcBitWidth =
697 cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
699 MaskIn.zext(SrcBitWidth);
700 KnownZero.zext(SrcBitWidth);
701 KnownOne.zext(SrcBitWidth);
702 ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, Depth+1);
703 KnownZero.trunc(BitWidth);
704 KnownOne.trunc(BitWidth);
707 case Instruction::BitCast: {
708 const Type *SrcTy = I->getOperand(0)->getType();
709 if (SrcTy->isInteger()) {
710 ComputeMaskedBits(I->getOperand(0), Mask, KnownZero, KnownOne, Depth+1);
715 case Instruction::ZExt: {
716 // Compute the bits in the result that are not present in the input.
717 const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
718 uint32_t SrcBitWidth = SrcTy->getBitWidth();
721 MaskIn.trunc(SrcBitWidth);
722 KnownZero.trunc(SrcBitWidth);
723 KnownOne.trunc(SrcBitWidth);
724 ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, Depth+1);
725 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
726 // The top bits are known to be zero.
727 KnownZero.zext(BitWidth);
728 KnownOne.zext(BitWidth);
729 KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
732 case Instruction::SExt: {
733 // Compute the bits in the result that are not present in the input.
734 const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
735 uint32_t SrcBitWidth = SrcTy->getBitWidth();
738 MaskIn.trunc(SrcBitWidth);
739 KnownZero.trunc(SrcBitWidth);
740 KnownOne.trunc(SrcBitWidth);
741 ComputeMaskedBits(I->getOperand(0), MaskIn, KnownZero, KnownOne, Depth+1);
742 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
743 KnownZero.zext(BitWidth);
744 KnownOne.zext(BitWidth);
746 // If the sign bit of the input is known set or clear, then we know the
747 // top bits of the result.
748 if (KnownZero[SrcBitWidth-1]) // Input sign bit known zero
749 KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
750 else if (KnownOne[SrcBitWidth-1]) // Input sign bit known set
751 KnownOne |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
754 case Instruction::Shl:
755 // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
756 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
757 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
758 APInt Mask2(Mask.lshr(ShiftAmt));
759 ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero, KnownOne, Depth+1);
760 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
761 KnownZero <<= ShiftAmt;
762 KnownOne <<= ShiftAmt;
763 KnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt); // low bits known 0
767 case Instruction::LShr:
768 // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
769 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
770 // Compute the new bits that are at the top now.
771 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
773 // Unsigned shift right.
774 APInt Mask2(Mask.shl(ShiftAmt));
775 ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne,Depth+1);
776 assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
777 KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
778 KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
779 // high bits known zero.
780 KnownZero |= APInt::getHighBitsSet(BitWidth, ShiftAmt);
784 case Instruction::AShr:
785 // (ashr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
786 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
787 // Compute the new bits that are at the top now.
788 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
790 // Signed shift right.
791 APInt Mask2(Mask.shl(ShiftAmt));
792 ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero,KnownOne,Depth+1);
793 assert((KnownZero & KnownOne) == 0&&"Bits known to be one AND zero?");
794 KnownZero = APIntOps::lshr(KnownZero, ShiftAmt);
795 KnownOne = APIntOps::lshr(KnownOne, ShiftAmt);
797 APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
798 if (KnownZero[BitWidth-ShiftAmt-1]) // New bits are known zero.
799 KnownZero |= HighBits;
800 else if (KnownOne[BitWidth-ShiftAmt-1]) // New bits are known one.
801 KnownOne |= HighBits;
808 /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
809 /// this predicate to simplify operations downstream. Mask is known to be zero
810 /// for bits that V cannot have.
811 static bool MaskedValueIsZero(Value *V, const APInt& Mask, unsigned Depth = 0) {
812 APInt KnownZero(Mask.getBitWidth(), 0), KnownOne(Mask.getBitWidth(), 0);
813 ComputeMaskedBits(V, Mask, KnownZero, KnownOne, Depth);
814 assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
815 return (KnownZero & Mask) == Mask;
818 /// ShrinkDemandedConstant - Check to see if the specified operand of the
819 /// specified instruction is a constant integer. If so, check to see if there
820 /// are any bits set in the constant that are not demanded. If so, shrink the
821 /// constant and return true.
822 static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
824 assert(I && "No instruction?");
825 assert(OpNo < I->getNumOperands() && "Operand index too large");
827 // If the operand is not a constant integer, nothing to do.
828 ConstantInt *OpC = dyn_cast<ConstantInt>(I->getOperand(OpNo));
829 if (!OpC) return false;
831 // If there are no bits set that aren't demanded, nothing to do.
832 Demanded.zextOrTrunc(OpC->getValue().getBitWidth());
833 if ((~Demanded & OpC->getValue()) == 0)
836 // This instruction is producing bits that are not demanded. Shrink the RHS.
837 Demanded &= OpC->getValue();
838 I->setOperand(OpNo, ConstantInt::get(Demanded));
842 // ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
843 // set of known zero and one bits, compute the maximum and minimum values that
844 // could have the specified known zero and known one bits, returning them in
846 static void ComputeSignedMinMaxValuesFromKnownBits(const Type *Ty,
847 const APInt& KnownZero,
848 const APInt& KnownOne,
849 APInt& Min, APInt& Max) {
850 uint32_t BitWidth = cast<IntegerType>(Ty)->getBitWidth();
851 assert(KnownZero.getBitWidth() == BitWidth &&
852 KnownOne.getBitWidth() == BitWidth &&
853 Min.getBitWidth() == BitWidth && Max.getBitWidth() == BitWidth &&
854 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
855 APInt UnknownBits = ~(KnownZero|KnownOne);
857 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
858 // bit if it is unknown.
860 Max = KnownOne|UnknownBits;
862 if (UnknownBits[BitWidth-1]) { // Sign bit is unknown
864 Max.clear(BitWidth-1);
868 // ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and
869 // a set of known zero and one bits, compute the maximum and minimum values that
870 // could have the specified known zero and known one bits, returning them in
872 static void ComputeUnsignedMinMaxValuesFromKnownBits(const Type *Ty,
873 const APInt &KnownZero,
874 const APInt &KnownOne,
875 APInt &Min, APInt &Max) {
876 uint32_t BitWidth = cast<IntegerType>(Ty)->getBitWidth(); BitWidth = BitWidth;
877 assert(KnownZero.getBitWidth() == BitWidth &&
878 KnownOne.getBitWidth() == BitWidth &&
879 Min.getBitWidth() == BitWidth && Max.getBitWidth() &&
880 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
881 APInt UnknownBits = ~(KnownZero|KnownOne);
883 // The minimum value is when the unknown bits are all zeros.
885 // The maximum value is when the unknown bits are all ones.
886 Max = KnownOne|UnknownBits;
889 /// SimplifyDemandedBits - This function attempts to replace V with a simpler
890 /// value based on the demanded bits. When this function is called, it is known
891 /// that only the bits set in DemandedMask of the result of V are ever used
892 /// downstream. Consequently, depending on the mask and V, it may be possible
893 /// to replace V with a constant or one of its operands. In such cases, this
894 /// function does the replacement and returns true. In all other cases, it
895 /// returns false after analyzing the expression and setting KnownOne and known
896 /// to be one in the expression. KnownZero contains all the bits that are known
897 /// to be zero in the expression. These are provided to potentially allow the
898 /// caller (which might recursively be SimplifyDemandedBits itself) to simplify
899 /// the expression. KnownOne and KnownZero always follow the invariant that
900 /// KnownOne & KnownZero == 0. That is, a bit can't be both 1 and 0. Note that
901 /// the bits in KnownOne and KnownZero may only be accurate for those bits set
902 /// in DemandedMask. Note also that the bitwidth of V, DemandedMask, KnownZero
903 /// and KnownOne must all be the same.
904 bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
905 APInt& KnownZero, APInt& KnownOne,
907 assert(V != 0 && "Null pointer of Value???");
908 assert(Depth <= 6 && "Limit Search Depth");
909 uint32_t BitWidth = DemandedMask.getBitWidth();
910 const IntegerType *VTy = cast<IntegerType>(V->getType());
911 assert(VTy->getBitWidth() == BitWidth &&
912 KnownZero.getBitWidth() == BitWidth &&
913 KnownOne.getBitWidth() == BitWidth &&
914 "Value *V, DemandedMask, KnownZero and KnownOne \
915 must have same BitWidth");
916 if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
917 // We know all of the bits for a constant!
918 KnownOne = CI->getValue() & DemandedMask;
919 KnownZero = ~KnownOne & DemandedMask;
925 if (!V->hasOneUse()) { // Other users may use these bits.
926 if (Depth != 0) { // Not at the root.
927 // Just compute the KnownZero/KnownOne bits to simplify things downstream.
928 ComputeMaskedBits(V, DemandedMask, KnownZero, KnownOne, Depth);
931 // If this is the root being simplified, allow it to have multiple uses,
932 // just set the DemandedMask to all bits.
933 DemandedMask = APInt::getAllOnesValue(BitWidth);
934 } else if (DemandedMask == 0) { // Not demanding any bits from V.
935 if (V != UndefValue::get(VTy))
936 return UpdateValueUsesWith(V, UndefValue::get(VTy));
938 } else if (Depth == 6) { // Limit search depth.
942 Instruction *I = dyn_cast<Instruction>(V);
943 if (!I) return false; // Only analyze instructions.
945 APInt LHSKnownZero(BitWidth, 0), LHSKnownOne(BitWidth, 0);
946 APInt &RHSKnownZero = KnownZero, &RHSKnownOne = KnownOne;
947 switch (I->getOpcode()) {
949 case Instruction::And:
950 // If either the LHS or the RHS are Zero, the result is zero.
951 if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
952 RHSKnownZero, RHSKnownOne, Depth+1))
954 assert((RHSKnownZero & RHSKnownOne) == 0 &&
955 "Bits known to be one AND zero?");
957 // If something is known zero on the RHS, the bits aren't demanded on the
959 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~RHSKnownZero,
960 LHSKnownZero, LHSKnownOne, Depth+1))
962 assert((LHSKnownZero & LHSKnownOne) == 0 &&
963 "Bits known to be one AND zero?");
965 // If all of the demanded bits are known 1 on one side, return the other.
966 // These bits cannot contribute to the result of the 'and'.
967 if ((DemandedMask & ~LHSKnownZero & RHSKnownOne) ==
968 (DemandedMask & ~LHSKnownZero))
969 return UpdateValueUsesWith(I, I->getOperand(0));
970 if ((DemandedMask & ~RHSKnownZero & LHSKnownOne) ==
971 (DemandedMask & ~RHSKnownZero))
972 return UpdateValueUsesWith(I, I->getOperand(1));
974 // If all of the demanded bits in the inputs are known zeros, return zero.
975 if ((DemandedMask & (RHSKnownZero|LHSKnownZero)) == DemandedMask)
976 return UpdateValueUsesWith(I, Constant::getNullValue(VTy));
978 // If the RHS is a constant, see if we can simplify it.
979 if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnownZero))
980 return UpdateValueUsesWith(I, I);
982 // Output known-1 bits are only known if set in both the LHS & RHS.
983 RHSKnownOne &= LHSKnownOne;
984 // Output known-0 are known to be clear if zero in either the LHS | RHS.
985 RHSKnownZero |= LHSKnownZero;
987 case Instruction::Or:
988 // If either the LHS or the RHS are One, the result is One.
989 if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
990 RHSKnownZero, RHSKnownOne, Depth+1))
992 assert((RHSKnownZero & RHSKnownOne) == 0 &&
993 "Bits known to be one AND zero?");
994 // If something is known one on the RHS, the bits aren't demanded on the
996 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask & ~RHSKnownOne,
997 LHSKnownZero, LHSKnownOne, Depth+1))
999 assert((LHSKnownZero & LHSKnownOne) == 0 &&
1000 "Bits known to be one AND zero?");
1002 // If all of the demanded bits are known zero on one side, return the other.
1003 // These bits cannot contribute to the result of the 'or'.
1004 if ((DemandedMask & ~LHSKnownOne & RHSKnownZero) ==
1005 (DemandedMask & ~LHSKnownOne))
1006 return UpdateValueUsesWith(I, I->getOperand(0));
1007 if ((DemandedMask & ~RHSKnownOne & LHSKnownZero) ==
1008 (DemandedMask & ~RHSKnownOne))
1009 return UpdateValueUsesWith(I, I->getOperand(1));
1011 // If all of the potentially set bits on one side are known to be set on
1012 // the other side, just use the 'other' side.
1013 if ((DemandedMask & (~RHSKnownZero) & LHSKnownOne) ==
1014 (DemandedMask & (~RHSKnownZero)))
1015 return UpdateValueUsesWith(I, I->getOperand(0));
1016 if ((DemandedMask & (~LHSKnownZero) & RHSKnownOne) ==
1017 (DemandedMask & (~LHSKnownZero)))
1018 return UpdateValueUsesWith(I, I->getOperand(1));
1020 // If the RHS is a constant, see if we can simplify it.
1021 if (ShrinkDemandedConstant(I, 1, DemandedMask))
1022 return UpdateValueUsesWith(I, I);
1024 // Output known-0 bits are only known if clear in both the LHS & RHS.
1025 RHSKnownZero &= LHSKnownZero;
1026 // Output known-1 are known to be set if set in either the LHS | RHS.
1027 RHSKnownOne |= LHSKnownOne;
1029 case Instruction::Xor: {
1030 if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
1031 RHSKnownZero, RHSKnownOne, Depth+1))
1033 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1034 "Bits known to be one AND zero?");
1035 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
1036 LHSKnownZero, LHSKnownOne, Depth+1))
1038 assert((LHSKnownZero & LHSKnownOne) == 0 &&
1039 "Bits known to be one AND zero?");
1041 // If all of the demanded bits are known zero on one side, return the other.
1042 // These bits cannot contribute to the result of the 'xor'.
1043 if ((DemandedMask & RHSKnownZero) == DemandedMask)
1044 return UpdateValueUsesWith(I, I->getOperand(0));
1045 if ((DemandedMask & LHSKnownZero) == DemandedMask)
1046 return UpdateValueUsesWith(I, I->getOperand(1));
1048 // Output known-0 bits are known if clear or set in both the LHS & RHS.
1049 APInt KnownZeroOut = (RHSKnownZero & LHSKnownZero) |
1050 (RHSKnownOne & LHSKnownOne);
1051 // Output known-1 are known to be set if set in only one of the LHS, RHS.
1052 APInt KnownOneOut = (RHSKnownZero & LHSKnownOne) |
1053 (RHSKnownOne & LHSKnownZero);
1055 // If all of the demanded bits are known to be zero on one side or the
1056 // other, turn this into an *inclusive* or.
1057 // e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
1058 if ((DemandedMask & ~RHSKnownZero & ~LHSKnownZero) == 0) {
1060 BinaryOperator::createOr(I->getOperand(0), I->getOperand(1),
1062 InsertNewInstBefore(Or, *I);
1063 return UpdateValueUsesWith(I, Or);
1066 // If all of the demanded bits on one side are known, and all of the set
1067 // bits on that side are also known to be set on the other side, turn this
1068 // into an AND, as we know the bits will be cleared.
1069 // e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1070 if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask) {
1072 if ((RHSKnownOne & LHSKnownOne) == RHSKnownOne) {
1073 Constant *AndC = ConstantInt::get(~RHSKnownOne & DemandedMask);
1075 BinaryOperator::createAnd(I->getOperand(0), AndC, "tmp");
1076 InsertNewInstBefore(And, *I);
1077 return UpdateValueUsesWith(I, And);
1081 // If the RHS is a constant, see if we can simplify it.
1082 // FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
1083 if (ShrinkDemandedConstant(I, 1, DemandedMask))
1084 return UpdateValueUsesWith(I, I);
1086 RHSKnownZero = KnownZeroOut;
1087 RHSKnownOne = KnownOneOut;
1090 case Instruction::Select:
1091 if (SimplifyDemandedBits(I->getOperand(2), DemandedMask,
1092 RHSKnownZero, RHSKnownOne, Depth+1))
1094 if (SimplifyDemandedBits(I->getOperand(1), DemandedMask,
1095 LHSKnownZero, LHSKnownOne, Depth+1))
1097 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1098 "Bits known to be one AND zero?");
1099 assert((LHSKnownZero & LHSKnownOne) == 0 &&
1100 "Bits known to be one AND zero?");
1102 // If the operands are constants, see if we can simplify them.
1103 if (ShrinkDemandedConstant(I, 1, DemandedMask))
1104 return UpdateValueUsesWith(I, I);
1105 if (ShrinkDemandedConstant(I, 2, DemandedMask))
1106 return UpdateValueUsesWith(I, I);
1108 // Only known if known in both the LHS and RHS.
1109 RHSKnownOne &= LHSKnownOne;
1110 RHSKnownZero &= LHSKnownZero;
1112 case Instruction::Trunc: {
1114 cast<IntegerType>(I->getOperand(0)->getType())->getBitWidth();
1115 DemandedMask.zext(truncBf);
1116 RHSKnownZero.zext(truncBf);
1117 RHSKnownOne.zext(truncBf);
1118 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
1119 RHSKnownZero, RHSKnownOne, Depth+1))
1121 DemandedMask.trunc(BitWidth);
1122 RHSKnownZero.trunc(BitWidth);
1123 RHSKnownOne.trunc(BitWidth);
1124 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1125 "Bits known to be one AND zero?");
1128 case Instruction::BitCast:
1129 if (!I->getOperand(0)->getType()->isInteger())
1132 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
1133 RHSKnownZero, RHSKnownOne, Depth+1))
1135 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1136 "Bits known to be one AND zero?");
1138 case Instruction::ZExt: {
1139 // Compute the bits in the result that are not present in the input.
1140 const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
1141 uint32_t SrcBitWidth = SrcTy->getBitWidth();
1143 DemandedMask.trunc(SrcBitWidth);
1144 RHSKnownZero.trunc(SrcBitWidth);
1145 RHSKnownOne.trunc(SrcBitWidth);
1146 if (SimplifyDemandedBits(I->getOperand(0), DemandedMask,
1147 RHSKnownZero, RHSKnownOne, Depth+1))
1149 DemandedMask.zext(BitWidth);
1150 RHSKnownZero.zext(BitWidth);
1151 RHSKnownOne.zext(BitWidth);
1152 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1153 "Bits known to be one AND zero?");
1154 // The top bits are known to be zero.
1155 RHSKnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth);
1158 case Instruction::SExt: {
1159 // Compute the bits in the result that are not present in the input.
1160 const IntegerType *SrcTy = cast<IntegerType>(I->getOperand(0)->getType());
1161 uint32_t SrcBitWidth = SrcTy->getBitWidth();
1163 APInt InputDemandedBits = DemandedMask &
1164 APInt::getLowBitsSet(BitWidth, SrcBitWidth);
1166 APInt NewBits(APInt::getHighBitsSet(BitWidth, BitWidth - SrcBitWidth));
1167 // If any of the sign extended bits are demanded, we know that the sign
1169 if ((NewBits & DemandedMask) != 0)
1170 InputDemandedBits.set(SrcBitWidth-1);
1172 InputDemandedBits.trunc(SrcBitWidth);
1173 RHSKnownZero.trunc(SrcBitWidth);
1174 RHSKnownOne.trunc(SrcBitWidth);
1175 if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits,
1176 RHSKnownZero, RHSKnownOne, Depth+1))
1178 InputDemandedBits.zext(BitWidth);
1179 RHSKnownZero.zext(BitWidth);
1180 RHSKnownOne.zext(BitWidth);
1181 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1182 "Bits known to be one AND zero?");
1184 // If the sign bit of the input is known set or clear, then we know the
1185 // top bits of the result.
1187 // If the input sign bit is known zero, or if the NewBits are not demanded
1188 // convert this into a zero extension.
1189 if (RHSKnownZero[SrcBitWidth-1] || (NewBits & ~DemandedMask) == NewBits)
1191 // Convert to ZExt cast
1192 CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy, I->getName(), I);
1193 return UpdateValueUsesWith(I, NewCast);
1194 } else if (RHSKnownOne[SrcBitWidth-1]) { // Input sign bit known set
1195 RHSKnownOne |= NewBits;
1199 case Instruction::Add: {
1200 // Figure out what the input bits are. If the top bits of the and result
1201 // are not demanded, then the add doesn't demand them from its input
1203 uint32_t NLZ = DemandedMask.countLeadingZeros();
1205 // If there is a constant on the RHS, there are a variety of xformations
1207 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
1208 // If null, this should be simplified elsewhere. Some of the xforms here
1209 // won't work if the RHS is zero.
1213 // If the top bit of the output is demanded, demand everything from the
1214 // input. Otherwise, we demand all the input bits except NLZ top bits.
1215 APInt InDemandedBits(APInt::getLowBitsSet(BitWidth, BitWidth - NLZ));
1217 // Find information about known zero/one bits in the input.
1218 if (SimplifyDemandedBits(I->getOperand(0), InDemandedBits,
1219 LHSKnownZero, LHSKnownOne, Depth+1))
1222 // If the RHS of the add has bits set that can't affect the input, reduce
1224 if (ShrinkDemandedConstant(I, 1, InDemandedBits))
1225 return UpdateValueUsesWith(I, I);
1227 // Avoid excess work.
1228 if (LHSKnownZero == 0 && LHSKnownOne == 0)
1231 // Turn it into OR if input bits are zero.
1232 if ((LHSKnownZero & RHS->getValue()) == RHS->getValue()) {
1234 BinaryOperator::createOr(I->getOperand(0), I->getOperand(1),
1236 InsertNewInstBefore(Or, *I);
1237 return UpdateValueUsesWith(I, Or);
1240 // We can say something about the output known-zero and known-one bits,
1241 // depending on potential carries from the input constant and the
1242 // unknowns. For example if the LHS is known to have at most the 0x0F0F0
1243 // bits set and the RHS constant is 0x01001, then we know we have a known
1244 // one mask of 0x00001 and a known zero mask of 0xE0F0E.
1246 // To compute this, we first compute the potential carry bits. These are
1247 // the bits which may be modified. I'm not aware of a better way to do
1249 const APInt& RHSVal = RHS->getValue();
1250 APInt CarryBits((~LHSKnownZero + RHSVal) ^ (~LHSKnownZero ^ RHSVal));
1252 // Now that we know which bits have carries, compute the known-1/0 sets.
1254 // Bits are known one if they are known zero in one operand and one in the
1255 // other, and there is no input carry.
1256 RHSKnownOne = ((LHSKnownZero & RHSVal) |
1257 (LHSKnownOne & ~RHSVal)) & ~CarryBits;
1259 // Bits are known zero if they are known zero in both operands and there
1260 // is no input carry.
1261 RHSKnownZero = LHSKnownZero & ~RHSVal & ~CarryBits;
1263 // If the high-bits of this ADD are not demanded, then it does not demand
1264 // the high bits of its LHS or RHS.
1265 if (DemandedMask[BitWidth-1] == 0) {
1266 // Right fill the mask of bits for this ADD to demand the most
1267 // significant bit and all those below it.
1268 APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
1269 if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
1270 LHSKnownZero, LHSKnownOne, Depth+1))
1272 if (SimplifyDemandedBits(I->getOperand(1), DemandedFromOps,
1273 LHSKnownZero, LHSKnownOne, Depth+1))
1279 case Instruction::Sub:
1280 // If the high-bits of this SUB are not demanded, then it does not demand
1281 // the high bits of its LHS or RHS.
1282 if (DemandedMask[BitWidth-1] == 0) {
1283 // Right fill the mask of bits for this SUB to demand the most
1284 // significant bit and all those below it.
1285 uint32_t NLZ = DemandedMask.countLeadingZeros();
1286 APInt DemandedFromOps(APInt::getLowBitsSet(BitWidth, BitWidth-NLZ));
1287 if (SimplifyDemandedBits(I->getOperand(0), DemandedFromOps,
1288 LHSKnownZero, LHSKnownOne, Depth+1))
1290 if (SimplifyDemandedBits(I->getOperand(1), DemandedFromOps,
1291 LHSKnownZero, LHSKnownOne, Depth+1))
1295 case Instruction::Shl:
1296 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
1297 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
1298 APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
1299 if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
1300 RHSKnownZero, RHSKnownOne, Depth+1))
1302 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1303 "Bits known to be one AND zero?");
1304 RHSKnownZero <<= ShiftAmt;
1305 RHSKnownOne <<= ShiftAmt;
1306 // low bits known zero.
1308 RHSKnownZero |= APInt::getLowBitsSet(BitWidth, ShiftAmt);
1311 case Instruction::LShr:
1312 // For a logical shift right
1313 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
1314 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth);
1316 // Unsigned shift right.
1317 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
1318 if (SimplifyDemandedBits(I->getOperand(0), DemandedMaskIn,
1319 RHSKnownZero, RHSKnownOne, Depth+1))
1321 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1322 "Bits known to be one AND zero?");
1323 RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
1324 RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
1326 // Compute the new bits that are at the top now.
1327 APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
1328 RHSKnownZero |= HighBits; // high bits known zero.
1332 case Instruction::AShr:
1333 // If this is an arithmetic shift right and only the low-bit is set, we can
1334 // always convert this into a logical shr, even if the shift amount is
1335 // variable. The low bit of the shift cannot be an input sign bit unless
1336 // the shift amount is >= the size of the datatype, which is undefined.
1337 if (DemandedMask == 1) {
1338 // Perform the logical shift right.
1339 Value *NewVal = BinaryOperator::createLShr(
1340 I->getOperand(0), I->getOperand(1), I->getName());
1341 InsertNewInstBefore(cast<Instruction>(NewVal), *I);
1342 return UpdateValueUsesWith(I, NewVal);
1345 // If the sign bit is the only bit demanded by this ashr, then there is no
1346 // need to do it, the shift doesn't change the high bit.
1347 if (DemandedMask.isSignBit())
1348 return UpdateValueUsesWith(I, I->getOperand(0));
1350 if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) {
1351 uint32_t ShiftAmt = SA->getLimitedValue(BitWidth);
1353 // Signed shift right.
1354 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
1355 // If any of the "high bits" are demanded, we should set the sign bit as
1357 if (DemandedMask.countLeadingZeros() <= ShiftAmt)
1358 DemandedMaskIn.set(BitWidth-1);
1359 if (SimplifyDemandedBits(I->getOperand(0),
1361 RHSKnownZero, RHSKnownOne, Depth+1))
1363 assert((RHSKnownZero & RHSKnownOne) == 0 &&
1364 "Bits known to be one AND zero?");
1365 // Compute the new bits that are at the top now.
1366 APInt HighBits(APInt::getHighBitsSet(BitWidth, ShiftAmt));
1367 RHSKnownZero = APIntOps::lshr(RHSKnownZero, ShiftAmt);
1368 RHSKnownOne = APIntOps::lshr(RHSKnownOne, ShiftAmt);
1370 // Handle the sign bits.
1371 APInt SignBit(APInt::getSignBit(BitWidth));
1372 // Adjust to where it is now in the mask.
1373 SignBit = APIntOps::lshr(SignBit, ShiftAmt);
1375 // If the input sign bit is known to be zero, or if none of the top bits
1376 // are demanded, turn this into an unsigned shift right.
1377 if (RHSKnownZero[BitWidth-ShiftAmt-1] ||
1378 (HighBits & ~DemandedMask) == HighBits) {
1379 // Perform the logical shift right.
1380 Value *NewVal = BinaryOperator::createLShr(
1381 I->getOperand(0), SA, I->getName());
1382 InsertNewInstBefore(cast<Instruction>(NewVal), *I);
1383 return UpdateValueUsesWith(I, NewVal);
1384 } else if ((RHSKnownOne & SignBit) != 0) { // New bits are known one.
1385 RHSKnownOne |= HighBits;
1391 // If the client is only demanding bits that we know, return the known
1393 if ((DemandedMask & (RHSKnownZero|RHSKnownOne)) == DemandedMask)
1394 return UpdateValueUsesWith(I, ConstantInt::get(RHSKnownOne));
1399 /// SimplifyDemandedVectorElts - The specified value producecs a vector with
1400 /// 64 or fewer elements. DemandedElts contains the set of elements that are
1401 /// actually used by the caller. This method analyzes which elements of the
1402 /// operand are undef and returns that information in UndefElts.
1404 /// If the information about demanded elements can be used to simplify the
1405 /// operation, the operation is simplified, then the resultant value is
1406 /// returned. This returns null if no change was made.
1407 Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, uint64_t DemandedElts,
1408 uint64_t &UndefElts,
1410 unsigned VWidth = cast<VectorType>(V->getType())->getNumElements();
1411 assert(VWidth <= 64 && "Vector too wide to analyze!");
1412 uint64_t EltMask = ~0ULL >> (64-VWidth);
1413 assert(DemandedElts != EltMask && (DemandedElts & ~EltMask) == 0 &&
1414 "Invalid DemandedElts!");
1416 if (isa<UndefValue>(V)) {
1417 // If the entire vector is undefined, just return this info.
1418 UndefElts = EltMask;
1420 } else if (DemandedElts == 0) { // If nothing is demanded, provide undef.
1421 UndefElts = EltMask;
1422 return UndefValue::get(V->getType());
1426 if (ConstantVector *CP = dyn_cast<ConstantVector>(V)) {
1427 const Type *EltTy = cast<VectorType>(V->getType())->getElementType();
1428 Constant *Undef = UndefValue::get(EltTy);
1430 std::vector<Constant*> Elts;
1431 for (unsigned i = 0; i != VWidth; ++i)
1432 if (!(DemandedElts & (1ULL << i))) { // If not demanded, set to undef.
1433 Elts.push_back(Undef);
1434 UndefElts |= (1ULL << i);
1435 } else if (isa<UndefValue>(CP->getOperand(i))) { // Already undef.
1436 Elts.push_back(Undef);
1437 UndefElts |= (1ULL << i);
1438 } else { // Otherwise, defined.
1439 Elts.push_back(CP->getOperand(i));
1442 // If we changed the constant, return it.
1443 Constant *NewCP = ConstantVector::get(Elts);
1444 return NewCP != CP ? NewCP : 0;
1445 } else if (isa<ConstantAggregateZero>(V)) {
1446 // Simplify the CAZ to a ConstantVector where the non-demanded elements are
1448 const Type *EltTy = cast<VectorType>(V->getType())->getElementType();
1449 Constant *Zero = Constant::getNullValue(EltTy);
1450 Constant *Undef = UndefValue::get(EltTy);
1451 std::vector<Constant*> Elts;
1452 for (unsigned i = 0; i != VWidth; ++i)
1453 Elts.push_back((DemandedElts & (1ULL << i)) ? Zero : Undef);
1454 UndefElts = DemandedElts ^ EltMask;
1455 return ConstantVector::get(Elts);
1458 if (!V->hasOneUse()) { // Other users may use these bits.
1459 if (Depth != 0) { // Not at the root.
1460 // TODO: Just compute the UndefElts information recursively.
1464 } else if (Depth == 10) { // Limit search depth.
1468 Instruction *I = dyn_cast<Instruction>(V);
1469 if (!I) return false; // Only analyze instructions.
1471 bool MadeChange = false;
1472 uint64_t UndefElts2;
1474 switch (I->getOpcode()) {
1477 case Instruction::InsertElement: {
1478 // If this is a variable index, we don't know which element it overwrites.
1479 // demand exactly the same input as we produce.
1480 ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
1482 // Note that we can't propagate undef elt info, because we don't know
1483 // which elt is getting updated.
1484 TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
1485 UndefElts2, Depth+1);
1486 if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
1490 // If this is inserting an element that isn't demanded, remove this
1492 unsigned IdxNo = Idx->getZExtValue();
1493 if (IdxNo >= VWidth || (DemandedElts & (1ULL << IdxNo)) == 0)
1494 return AddSoonDeadInstToWorklist(*I, 0);
1496 // Otherwise, the element inserted overwrites whatever was there, so the
1497 // input demanded set is simpler than the output set.
1498 TmpV = SimplifyDemandedVectorElts(I->getOperand(0),
1499 DemandedElts & ~(1ULL << IdxNo),
1500 UndefElts, Depth+1);
1501 if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
1503 // The inserted element is defined.
1504 UndefElts |= 1ULL << IdxNo;
1507 case Instruction::BitCast: {
1508 // Vector->vector casts only.
1509 const VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());
1511 unsigned InVWidth = VTy->getNumElements();
1512 uint64_t InputDemandedElts = 0;
1515 if (VWidth == InVWidth) {
1516 // If we are converting from <4 x i32> -> <4 x f32>, we demand the same
1517 // elements as are demanded of us.
1519 InputDemandedElts = DemandedElts;
1520 } else if (VWidth > InVWidth) {
1524 // If there are more elements in the result than there are in the source,
1525 // then an input element is live if any of the corresponding output
1526 // elements are live.
1527 Ratio = VWidth/InVWidth;
1528 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) {
1529 if (DemandedElts & (1ULL << OutIdx))
1530 InputDemandedElts |= 1ULL << (OutIdx/Ratio);
1536 // If there are more elements in the source than there are in the result,
1537 // then an input element is live if the corresponding output element is
1539 Ratio = InVWidth/VWidth;
1540 for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
1541 if (DemandedElts & (1ULL << InIdx/Ratio))
1542 InputDemandedElts |= 1ULL << InIdx;
1545 // div/rem demand all inputs, because they don't want divide by zero.
1546 TmpV = SimplifyDemandedVectorElts(I->getOperand(0), InputDemandedElts,
1547 UndefElts2, Depth+1);
1549 I->setOperand(0, TmpV);
1553 UndefElts = UndefElts2;
1554 if (VWidth > InVWidth) {
1555 assert(0 && "Unimp");
1556 // If there are more elements in the result than there are in the source,
1557 // then an output element is undef if the corresponding input element is
1559 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
1560 if (UndefElts2 & (1ULL << (OutIdx/Ratio)))
1561 UndefElts |= 1ULL << OutIdx;
1562 } else if (VWidth < InVWidth) {
1563 assert(0 && "Unimp");
1564 // If there are more elements in the source than there are in the result,
1565 // then a result element is undef if all of the corresponding input
1566 // elements are undef.
1567 UndefElts = ~0ULL >> (64-VWidth); // Start out all undef.
1568 for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
1569 if ((UndefElts2 & (1ULL << InIdx)) == 0) // Not undef?
1570 UndefElts &= ~(1ULL << (InIdx/Ratio)); // Clear undef bit.
1574 case Instruction::And:
1575 case Instruction::Or:
1576 case Instruction::Xor:
1577 case Instruction::Add:
1578 case Instruction::Sub:
1579 case Instruction::Mul:
1580 // div/rem demand all inputs, because they don't want divide by zero.
1581 TmpV = SimplifyDemandedVectorElts(I->getOperand(0), DemandedElts,
1582 UndefElts, Depth+1);
1583 if (TmpV) { I->setOperand(0, TmpV); MadeChange = true; }
1584 TmpV = SimplifyDemandedVectorElts(I->getOperand(1), DemandedElts,
1585 UndefElts2, Depth+1);
1586 if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
1588 // Output elements are undefined if both are undefined. Consider things
1589 // like undef&0. The result is known zero, not undef.
1590 UndefElts &= UndefElts2;
1593 case Instruction::Call: {
1594 IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
1596 switch (II->getIntrinsicID()) {
1599 // Binary vector operations that work column-wise. A dest element is a
1600 // function of the corresponding input elements from the two inputs.
1601 case Intrinsic::x86_sse_sub_ss:
1602 case Intrinsic::x86_sse_mul_ss:
1603 case Intrinsic::x86_sse_min_ss:
1604 case Intrinsic::x86_sse_max_ss:
1605 case Intrinsic::x86_sse2_sub_sd:
1606 case Intrinsic::x86_sse2_mul_sd:
1607 case Intrinsic::x86_sse2_min_sd:
1608 case Intrinsic::x86_sse2_max_sd:
1609 TmpV = SimplifyDemandedVectorElts(II->getOperand(1), DemandedElts,
1610 UndefElts, Depth+1);
1611 if (TmpV) { II->setOperand(1, TmpV); MadeChange = true; }
1612 TmpV = SimplifyDemandedVectorElts(II->getOperand(2), DemandedElts,
1613 UndefElts2, Depth+1);
1614 if (TmpV) { II->setOperand(2, TmpV); MadeChange = true; }
1616 // If only the low elt is demanded and this is a scalarizable intrinsic,
1617 // scalarize it now.
1618 if (DemandedElts == 1) {
1619 switch (II->getIntrinsicID()) {
1621 case Intrinsic::x86_sse_sub_ss:
1622 case Intrinsic::x86_sse_mul_ss:
1623 case Intrinsic::x86_sse2_sub_sd:
1624 case Intrinsic::x86_sse2_mul_sd:
1625 // TODO: Lower MIN/MAX/ABS/etc
1626 Value *LHS = II->getOperand(1);
1627 Value *RHS = II->getOperand(2);
1628 // Extract the element as scalars.
1629 LHS = InsertNewInstBefore(new ExtractElementInst(LHS, 0U,"tmp"), *II);
1630 RHS = InsertNewInstBefore(new ExtractElementInst(RHS, 0U,"tmp"), *II);
1632 switch (II->getIntrinsicID()) {
1633 default: assert(0 && "Case stmts out of sync!");
1634 case Intrinsic::x86_sse_sub_ss:
1635 case Intrinsic::x86_sse2_sub_sd:
1636 TmpV = InsertNewInstBefore(BinaryOperator::createSub(LHS, RHS,
1637 II->getName()), *II);
1639 case Intrinsic::x86_sse_mul_ss:
1640 case Intrinsic::x86_sse2_mul_sd:
1641 TmpV = InsertNewInstBefore(BinaryOperator::createMul(LHS, RHS,
1642 II->getName()), *II);
1647 new InsertElementInst(UndefValue::get(II->getType()), TmpV, 0U,
1649 InsertNewInstBefore(New, *II);
1650 AddSoonDeadInstToWorklist(*II, 0);
1655 // Output elements are undefined if both are undefined. Consider things
1656 // like undef&0. The result is known zero, not undef.
1657 UndefElts &= UndefElts2;
1663 return MadeChange ? I : 0;
1666 /// @returns true if the specified compare instruction is
1667 /// true when both operands are equal...
1668 /// @brief Determine if the ICmpInst returns true if both operands are equal
1669 static bool isTrueWhenEqual(ICmpInst &ICI) {
1670 ICmpInst::Predicate pred = ICI.getPredicate();
1671 return pred == ICmpInst::ICMP_EQ || pred == ICmpInst::ICMP_UGE ||
1672 pred == ICmpInst::ICMP_SGE || pred == ICmpInst::ICMP_ULE ||
1673 pred == ICmpInst::ICMP_SLE;
1676 /// AssociativeOpt - Perform an optimization on an associative operator. This
1677 /// function is designed to check a chain of associative operators for a
1678 /// potential to apply a certain optimization. Since the optimization may be
1679 /// applicable if the expression was reassociated, this checks the chain, then
1680 /// reassociates the expression as necessary to expose the optimization
1681 /// opportunity. This makes use of a special Functor, which must define
1682 /// 'shouldApply' and 'apply' methods.
1684 template<typename Functor>
1685 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
1686 unsigned Opcode = Root.getOpcode();
1687 Value *LHS = Root.getOperand(0);
1689 // Quick check, see if the immediate LHS matches...
1690 if (F.shouldApply(LHS))
1691 return F.apply(Root);
1693 // Otherwise, if the LHS is not of the same opcode as the root, return.
1694 Instruction *LHSI = dyn_cast<Instruction>(LHS);
1695 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
1696 // Should we apply this transform to the RHS?
1697 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
1699 // If not to the RHS, check to see if we should apply to the LHS...
1700 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
1701 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
1705 // If the functor wants to apply the optimization to the RHS of LHSI,
1706 // reassociate the expression from ((? op A) op B) to (? op (A op B))
1708 BasicBlock *BB = Root.getParent();
1710 // Now all of the instructions are in the current basic block, go ahead
1711 // and perform the reassociation.
1712 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
1714 // First move the selected RHS to the LHS of the root...
1715 Root.setOperand(0, LHSI->getOperand(1));
1717 // Make what used to be the LHS of the root be the user of the root...
1718 Value *ExtraOperand = TmpLHSI->getOperand(1);
1719 if (&Root == TmpLHSI) {
1720 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
1723 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
1724 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
1725 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
1726 BasicBlock::iterator ARI = &Root; ++ARI;
1727 BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
1730 // Now propagate the ExtraOperand down the chain of instructions until we
1732 while (TmpLHSI != LHSI) {
1733 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
1734 // Move the instruction to immediately before the chain we are
1735 // constructing to avoid breaking dominance properties.
1736 NextLHSI->getParent()->getInstList().remove(NextLHSI);
1737 BB->getInstList().insert(ARI, NextLHSI);
1740 Value *NextOp = NextLHSI->getOperand(1);
1741 NextLHSI->setOperand(1, ExtraOperand);
1743 ExtraOperand = NextOp;
1746 // Now that the instructions are reassociated, have the functor perform
1747 // the transformation...
1748 return F.apply(Root);
1751 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
1757 // AddRHS - Implements: X + X --> X << 1
1760 AddRHS(Value *rhs) : RHS(rhs) {}
1761 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1762 Instruction *apply(BinaryOperator &Add) const {
1763 return BinaryOperator::createShl(Add.getOperand(0),
1764 ConstantInt::get(Add.getType(), 1));
1768 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
1770 struct AddMaskingAnd {
1772 AddMaskingAnd(Constant *c) : C2(c) {}
1773 bool shouldApply(Value *LHS) const {
1775 return match(LHS, m_And(m_Value(), m_ConstantInt(C1))) &&
1776 ConstantExpr::getAnd(C1, C2)->isNullValue();
1778 Instruction *apply(BinaryOperator &Add) const {
1779 return BinaryOperator::createOr(Add.getOperand(0), Add.getOperand(1));
1783 static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
1785 if (CastInst *CI = dyn_cast<CastInst>(&I)) {
1786 if (Constant *SOC = dyn_cast<Constant>(SO))
1787 return ConstantExpr::getCast(CI->getOpcode(), SOC, I.getType());
1789 return IC->InsertNewInstBefore(CastInst::create(
1790 CI->getOpcode(), SO, I.getType(), SO->getName() + ".cast"), I);
1793 // Figure out if the constant is the left or the right argument.
1794 bool ConstIsRHS = isa<Constant>(I.getOperand(1));
1795 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
1797 if (Constant *SOC = dyn_cast<Constant>(SO)) {
1799 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
1800 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
1803 Value *Op0 = SO, *Op1 = ConstOperand;
1805 std::swap(Op0, Op1);
1807 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
1808 New = BinaryOperator::create(BO->getOpcode(), Op0, Op1,SO->getName()+".op");
1809 else if (CmpInst *CI = dyn_cast<CmpInst>(&I))
1810 New = CmpInst::create(CI->getOpcode(), CI->getPredicate(), Op0, Op1,
1811 SO->getName()+".cmp");
1813 assert(0 && "Unknown binary instruction type!");
1816 return IC->InsertNewInstBefore(New, I);
1819 // FoldOpIntoSelect - Given an instruction with a select as one operand and a
1820 // constant as the other operand, try to fold the binary operator into the
1821 // select arguments. This also works for Cast instructions, which obviously do
1822 // not have a second operand.
1823 static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
1825 // Don't modify shared select instructions
1826 if (!SI->hasOneUse()) return 0;
1827 Value *TV = SI->getOperand(1);
1828 Value *FV = SI->getOperand(2);
1830 if (isa<Constant>(TV) || isa<Constant>(FV)) {
1831 // Bool selects with constant operands can be folded to logical ops.
1832 if (SI->getType() == Type::Int1Ty) return 0;
1834 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, IC);
1835 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, IC);
1837 return new SelectInst(SI->getCondition(), SelectTrueVal,
1844 /// FoldOpIntoPhi - Given a binary operator or cast instruction which has a PHI
1845 /// node as operand #0, see if we can fold the instruction into the PHI (which
1846 /// is only possible if all operands to the PHI are constants).
1847 Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
1848 PHINode *PN = cast<PHINode>(I.getOperand(0));
1849 unsigned NumPHIValues = PN->getNumIncomingValues();
1850 if (!PN->hasOneUse() || NumPHIValues == 0) return 0;
1852 // Check to see if all of the operands of the PHI are constants. If there is
1853 // one non-constant value, remember the BB it is. If there is more than one
1854 // or if *it* is a PHI, bail out.
1855 BasicBlock *NonConstBB = 0;
1856 for (unsigned i = 0; i != NumPHIValues; ++i)
1857 if (!isa<Constant>(PN->getIncomingValue(i))) {
1858 if (NonConstBB) return 0; // More than one non-const value.
1859 if (isa<PHINode>(PN->getIncomingValue(i))) return 0; // Itself a phi.
1860 NonConstBB = PN->getIncomingBlock(i);
1862 // If the incoming non-constant value is in I's block, we have an infinite
1864 if (NonConstBB == I.getParent())
1868 // If there is exactly one non-constant value, we can insert a copy of the
1869 // operation in that block. However, if this is a critical edge, we would be
1870 // inserting the computation one some other paths (e.g. inside a loop). Only
1871 // do this if the pred block is unconditionally branching into the phi block.
1873 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
1874 if (!BI || !BI->isUnconditional()) return 0;
1877 // Okay, we can do the transformation: create the new PHI node.
1878 PHINode *NewPN = new PHINode(I.getType(), "");
1879 NewPN->reserveOperandSpace(PN->getNumOperands()/2);
1880 InsertNewInstBefore(NewPN, *PN);
1881 NewPN->takeName(PN);
1883 // Next, add all of the operands to the PHI.
1884 if (I.getNumOperands() == 2) {
1885 Constant *C = cast<Constant>(I.getOperand(1));
1886 for (unsigned i = 0; i != NumPHIValues; ++i) {
1888 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
1889 if (CmpInst *CI = dyn_cast<CmpInst>(&I))
1890 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C);
1892 InV = ConstantExpr::get(I.getOpcode(), InC, C);
1894 assert(PN->getIncomingBlock(i) == NonConstBB);
1895 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
1896 InV = BinaryOperator::create(BO->getOpcode(),
1897 PN->getIncomingValue(i), C, "phitmp",
1898 NonConstBB->getTerminator());
1899 else if (CmpInst *CI = dyn_cast<CmpInst>(&I))
1900 InV = CmpInst::create(CI->getOpcode(),
1902 PN->getIncomingValue(i), C, "phitmp",
1903 NonConstBB->getTerminator());
1905 assert(0 && "Unknown binop!");
1907 AddToWorkList(cast<Instruction>(InV));
1909 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
1912 CastInst *CI = cast<CastInst>(&I);
1913 const Type *RetTy = CI->getType();
1914 for (unsigned i = 0; i != NumPHIValues; ++i) {
1916 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
1917 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy);
1919 assert(PN->getIncomingBlock(i) == NonConstBB);
1920 InV = CastInst::create(CI->getOpcode(), PN->getIncomingValue(i),
1921 I.getType(), "phitmp",
1922 NonConstBB->getTerminator());
1923 AddToWorkList(cast<Instruction>(InV));
1925 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
1928 return ReplaceInstUsesWith(I, NewPN);
1931 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
1932 bool Changed = SimplifyCommutative(I);
1933 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
1935 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
1936 // X + undef -> undef
1937 if (isa<UndefValue>(RHS))
1938 return ReplaceInstUsesWith(I, RHS);
1941 if (!I.getType()->isFPOrFPVector()) { // NOTE: -0 + +0 = +0.
1942 if (RHSC->isNullValue())
1943 return ReplaceInstUsesWith(I, LHS);
1944 } else if (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
1945 if (CFP->isExactlyValue(-0.0))
1946 return ReplaceInstUsesWith(I, LHS);
1949 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
1950 // X + (signbit) --> X ^ signbit
1951 const APInt& Val = CI->getValue();
1952 uint32_t BitWidth = Val.getBitWidth();
1953 if (Val == APInt::getSignBit(BitWidth))
1954 return BinaryOperator::createXor(LHS, RHS);
1956 // See if SimplifyDemandedBits can simplify this. This handles stuff like
1957 // (X & 254)+1 -> (X&254)|1
1958 if (!isa<VectorType>(I.getType())) {
1959 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
1960 if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
1961 KnownZero, KnownOne))
1966 if (isa<PHINode>(LHS))
1967 if (Instruction *NV = FoldOpIntoPhi(I))
1970 ConstantInt *XorRHS = 0;
1972 if (isa<ConstantInt>(RHSC) &&
1973 match(LHS, m_Xor(m_Value(XorLHS), m_ConstantInt(XorRHS)))) {
1974 uint32_t TySizeBits = I.getType()->getPrimitiveSizeInBits();
1975 const APInt& RHSVal = cast<ConstantInt>(RHSC)->getValue();
1977 uint32_t Size = TySizeBits / 2;
1978 APInt C0080Val(APInt(TySizeBits, 1ULL).shl(Size - 1));
1979 APInt CFF80Val(-C0080Val);
1981 if (TySizeBits > Size) {
1982 // If we have ADD(XOR(AND(X, 0xFF), 0x80), 0xF..F80), it's a sext.
1983 // If we have ADD(XOR(AND(X, 0xFF), 0xF..F80), 0x80), it's a sext.
1984 if ((RHSVal == CFF80Val && XorRHS->getValue() == C0080Val) ||
1985 (RHSVal == C0080Val && XorRHS->getValue() == CFF80Val)) {
1986 // This is a sign extend if the top bits are known zero.
1987 if (!MaskedValueIsZero(XorLHS,
1988 APInt::getHighBitsSet(TySizeBits, TySizeBits - Size)))
1989 Size = 0; // Not a sign ext, but can't be any others either.
1994 C0080Val = APIntOps::lshr(C0080Val, Size);
1995 CFF80Val = APIntOps::ashr(CFF80Val, Size);
1996 } while (Size >= 1);
1998 // FIXME: This shouldn't be necessary. When the backends can handle types
1999 // with funny bit widths then this whole cascade of if statements should
2000 // be removed. It is just here to get the size of the "middle" type back
2001 // up to something that the back ends can handle.
2002 const Type *MiddleType = 0;
2005 case 32: MiddleType = Type::Int32Ty; break;
2006 case 16: MiddleType = Type::Int16Ty; break;
2007 case 8: MiddleType = Type::Int8Ty; break;
2010 Instruction *NewTrunc = new TruncInst(XorLHS, MiddleType, "sext");
2011 InsertNewInstBefore(NewTrunc, I);
2012 return new SExtInst(NewTrunc, I.getType(), I.getName());
2018 if (I.getType()->isInteger() && I.getType() != Type::Int1Ty) {
2019 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
2021 if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
2022 if (RHSI->getOpcode() == Instruction::Sub)
2023 if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
2024 return ReplaceInstUsesWith(I, RHSI->getOperand(0));
2026 if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
2027 if (LHSI->getOpcode() == Instruction::Sub)
2028 if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
2029 return ReplaceInstUsesWith(I, LHSI->getOperand(0));
2034 if (Value *V = dyn_castNegVal(LHS))
2035 return BinaryOperator::createSub(RHS, V);
2038 if (!isa<Constant>(RHS))
2039 if (Value *V = dyn_castNegVal(RHS))
2040 return BinaryOperator::createSub(LHS, V);
2044 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
2045 if (X == RHS) // X*C + X --> X * (C+1)
2046 return BinaryOperator::createMul(RHS, AddOne(C2));
2048 // X*C1 + X*C2 --> X * (C1+C2)
2050 if (X == dyn_castFoldableMul(RHS, C1))
2051 return BinaryOperator::createMul(X, Add(C1, C2));
2054 // X + X*C --> X * (C+1)
2055 if (dyn_castFoldableMul(RHS, C2) == LHS)
2056 return BinaryOperator::createMul(LHS, AddOne(C2));
2058 // X + ~X --> -1 since ~X = -X-1
2059 if (dyn_castNotVal(LHS) == RHS || dyn_castNotVal(RHS) == LHS)
2060 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
2063 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
2064 if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
2065 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2)))
2068 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
2070 if (match(LHS, m_Not(m_Value(X)))) // ~X + C --> (C-1) - X
2071 return BinaryOperator::createSub(SubOne(CRHS), X);
2073 // (X & FF00) + xx00 -> (X+xx00) & FF00
2074 if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
2075 Constant *Anded = And(CRHS, C2);
2076 if (Anded == CRHS) {
2077 // See if all bits from the first bit set in the Add RHS up are included
2078 // in the mask. First, get the rightmost bit.
2079 const APInt& AddRHSV = CRHS->getValue();
2081 // Form a mask of all bits from the lowest bit added through the top.
2082 APInt AddRHSHighBits(~((AddRHSV & -AddRHSV)-1));
2084 // See if the and mask includes all of these bits.
2085 APInt AddRHSHighBitsAnd(AddRHSHighBits & C2->getValue());
2087 if (AddRHSHighBits == AddRHSHighBitsAnd) {
2088 // Okay, the xform is safe. Insert the new add pronto.
2089 Value *NewAdd = InsertNewInstBefore(BinaryOperator::createAdd(X, CRHS,
2090 LHS->getName()), I);
2091 return BinaryOperator::createAnd(NewAdd, C2);
2096 // Try to fold constant add into select arguments.
2097 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
2098 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2102 // add (cast *A to intptrtype) B ->
2103 // cast (GEP (cast *A to sbyte*) B) ->
2106 CastInst *CI = dyn_cast<CastInst>(LHS);
2109 CI = dyn_cast<CastInst>(RHS);
2112 if (CI && CI->getType()->isSized() &&
2113 (CI->getType()->getPrimitiveSizeInBits() ==
2114 TD->getIntPtrType()->getPrimitiveSizeInBits())
2115 && isa<PointerType>(CI->getOperand(0)->getType())) {
2116 Value *I2 = InsertCastBefore(Instruction::BitCast, CI->getOperand(0),
2117 PointerType::get(Type::Int8Ty), I);
2118 I2 = InsertNewInstBefore(new GetElementPtrInst(I2, Other, "ctg2"), I);
2119 return new PtrToIntInst(I2, CI->getType());
2123 return Changed ? &I : 0;
2126 // isSignBit - Return true if the value represented by the constant only has the
2127 // highest order bit set.
2128 static bool isSignBit(ConstantInt *CI) {
2129 uint32_t NumBits = CI->getType()->getPrimitiveSizeInBits();
2130 return CI->getValue() == APInt::getSignBit(NumBits);
2133 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
2134 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2136 if (Op0 == Op1) // sub X, X -> 0
2137 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2139 // If this is a 'B = x-(-A)', change to B = x+A...
2140 if (Value *V = dyn_castNegVal(Op1))
2141 return BinaryOperator::createAdd(Op0, V);
2143 if (isa<UndefValue>(Op0))
2144 return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
2145 if (isa<UndefValue>(Op1))
2146 return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
2148 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
2149 // Replace (-1 - A) with (~A)...
2150 if (C->isAllOnesValue())
2151 return BinaryOperator::createNot(Op1);
2153 // C - ~X == X + (1+C)
2155 if (match(Op1, m_Not(m_Value(X))))
2156 return BinaryOperator::createAdd(X, AddOne(C));
2158 // -(X >>u 31) -> (X >>s 31)
2159 // -(X >>s 31) -> (X >>u 31)
2161 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op1))
2162 if (SI->getOpcode() == Instruction::LShr) {
2163 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
2164 // Check to see if we are shifting out everything but the sign bit.
2165 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
2166 SI->getType()->getPrimitiveSizeInBits()-1) {
2167 // Ok, the transformation is safe. Insert AShr.
2168 return BinaryOperator::create(Instruction::AShr,
2169 SI->getOperand(0), CU, SI->getName());
2173 else if (SI->getOpcode() == Instruction::AShr) {
2174 if (ConstantInt *CU = dyn_cast<ConstantInt>(SI->getOperand(1))) {
2175 // Check to see if we are shifting out everything but the sign bit.
2176 if (CU->getLimitedValue(SI->getType()->getPrimitiveSizeInBits()) ==
2177 SI->getType()->getPrimitiveSizeInBits()-1) {
2178 // Ok, the transformation is safe. Insert LShr.
2179 return BinaryOperator::createLShr(
2180 SI->getOperand(0), CU, SI->getName());
2186 // Try to fold constant sub into select arguments.
2187 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
2188 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2191 if (isa<PHINode>(Op0))
2192 if (Instruction *NV = FoldOpIntoPhi(I))
2196 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
2197 if (Op1I->getOpcode() == Instruction::Add &&
2198 !Op0->getType()->isFPOrFPVector()) {
2199 if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
2200 return BinaryOperator::createNeg(Op1I->getOperand(1), I.getName());
2201 else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
2202 return BinaryOperator::createNeg(Op1I->getOperand(0), I.getName());
2203 else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
2204 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
2205 // C1-(X+C2) --> (C1-C2)-X
2206 return BinaryOperator::createSub(Subtract(CI1, CI2),
2207 Op1I->getOperand(0));
2211 if (Op1I->hasOneUse()) {
2212 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
2213 // is not used by anyone else...
2215 if (Op1I->getOpcode() == Instruction::Sub &&
2216 !Op1I->getType()->isFPOrFPVector()) {
2217 // Swap the two operands of the subexpr...
2218 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
2219 Op1I->setOperand(0, IIOp1);
2220 Op1I->setOperand(1, IIOp0);
2222 // Create the new top level add instruction...
2223 return BinaryOperator::createAdd(Op0, Op1);
2226 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
2228 if (Op1I->getOpcode() == Instruction::And &&
2229 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
2230 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
2233 InsertNewInstBefore(BinaryOperator::createNot(OtherOp, "B.not"), I);
2234 return BinaryOperator::createAnd(Op0, NewNot);
2237 // 0 - (X sdiv C) -> (X sdiv -C)
2238 if (Op1I->getOpcode() == Instruction::SDiv)
2239 if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
2241 if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
2242 return BinaryOperator::createSDiv(Op1I->getOperand(0),
2243 ConstantExpr::getNeg(DivRHS));
2245 // X - X*C --> X * (1-C)
2246 ConstantInt *C2 = 0;
2247 if (dyn_castFoldableMul(Op1I, C2) == Op0) {
2248 Constant *CP1 = Subtract(ConstantInt::get(I.getType(), 1), C2);
2249 return BinaryOperator::createMul(Op0, CP1);
2254 if (!Op0->getType()->isFPOrFPVector())
2255 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
2256 if (Op0I->getOpcode() == Instruction::Add) {
2257 if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
2258 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
2259 else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
2260 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
2261 } else if (Op0I->getOpcode() == Instruction::Sub) {
2262 if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
2263 return BinaryOperator::createNeg(Op0I->getOperand(1), I.getName());
2267 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
2268 if (X == Op1) // X*C - X --> X * (C-1)
2269 return BinaryOperator::createMul(Op1, SubOne(C1));
2271 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
2272 if (X == dyn_castFoldableMul(Op1, C2))
2273 return BinaryOperator::createMul(Op1, Subtract(C1, C2));
2278 /// isSignBitCheck - Given an exploded icmp instruction, return true if the
2279 /// comparison only checks the sign bit. If it only checks the sign bit, set
2280 /// TrueIfSigned if the result of the comparison is true when the input value is
2282 static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS,
2283 bool &TrueIfSigned) {
2285 case ICmpInst::ICMP_SLT: // True if LHS s< 0
2286 TrueIfSigned = true;
2287 return RHS->isZero();
2288 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
2289 TrueIfSigned = true;
2290 return RHS->isAllOnesValue();
2291 case ICmpInst::ICMP_SGT: // True if LHS s> -1
2292 TrueIfSigned = false;
2293 return RHS->isAllOnesValue();
2294 case ICmpInst::ICMP_UGT:
2295 // True if LHS u> RHS and RHS == high-bit-mask - 1
2296 TrueIfSigned = true;
2297 return RHS->getValue() ==
2298 APInt::getSignedMaxValue(RHS->getType()->getPrimitiveSizeInBits());
2299 case ICmpInst::ICMP_UGE:
2300 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
2301 TrueIfSigned = true;
2302 return RHS->getValue() ==
2303 APInt::getSignBit(RHS->getType()->getPrimitiveSizeInBits());
2309 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
2310 bool Changed = SimplifyCommutative(I);
2311 Value *Op0 = I.getOperand(0);
2313 if (isa<UndefValue>(I.getOperand(1))) // undef * X -> 0
2314 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2316 // Simplify mul instructions with a constant RHS...
2317 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
2318 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2320 // ((X << C1)*C2) == (X * (C2 << C1))
2321 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0))
2322 if (SI->getOpcode() == Instruction::Shl)
2323 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
2324 return BinaryOperator::createMul(SI->getOperand(0),
2325 ConstantExpr::getShl(CI, ShOp));
2328 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
2329 if (CI->equalsInt(1)) // X * 1 == X
2330 return ReplaceInstUsesWith(I, Op0);
2331 if (CI->isAllOnesValue()) // X * -1 == 0 - X
2332 return BinaryOperator::createNeg(Op0, I.getName());
2334 const APInt& Val = cast<ConstantInt>(CI)->getValue();
2335 if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C
2336 return BinaryOperator::createShl(Op0,
2337 ConstantInt::get(Op0->getType(), Val.logBase2()));
2339 } else if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1)) {
2340 if (Op1F->isNullValue())
2341 return ReplaceInstUsesWith(I, Op1);
2343 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
2344 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
2345 if (Op1F->getValue() == 1.0)
2346 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
2349 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
2350 if (Op0I->getOpcode() == Instruction::Add && Op0I->hasOneUse() &&
2351 isa<ConstantInt>(Op0I->getOperand(1))) {
2352 // Canonicalize (X+C1)*C2 -> X*C2+C1*C2.
2353 Instruction *Add = BinaryOperator::createMul(Op0I->getOperand(0),
2355 InsertNewInstBefore(Add, I);
2356 Value *C1C2 = ConstantExpr::getMul(Op1,
2357 cast<Constant>(Op0I->getOperand(1)));
2358 return BinaryOperator::createAdd(Add, C1C2);
2362 // Try to fold constant mul into select arguments.
2363 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
2364 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2367 if (isa<PHINode>(Op0))
2368 if (Instruction *NV = FoldOpIntoPhi(I))
2372 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
2373 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
2374 return BinaryOperator::createMul(Op0v, Op1v);
2376 // If one of the operands of the multiply is a cast from a boolean value, then
2377 // we know the bool is either zero or one, so this is a 'masking' multiply.
2378 // See if we can simplify things based on how the boolean was originally
2380 CastInst *BoolCast = 0;
2381 if (ZExtInst *CI = dyn_cast<ZExtInst>(I.getOperand(0)))
2382 if (CI->getOperand(0)->getType() == Type::Int1Ty)
2385 if (ZExtInst *CI = dyn_cast<ZExtInst>(I.getOperand(1)))
2386 if (CI->getOperand(0)->getType() == Type::Int1Ty)
2389 if (ICmpInst *SCI = dyn_cast<ICmpInst>(BoolCast->getOperand(0))) {
2390 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
2391 const Type *SCOpTy = SCIOp0->getType();
2394 // If the icmp is true iff the sign bit of X is set, then convert this
2395 // multiply into a shift/and combination.
2396 if (isa<ConstantInt>(SCIOp1) &&
2397 isSignBitCheck(SCI->getPredicate(), cast<ConstantInt>(SCIOp1), TIS) &&
2399 // Shift the X value right to turn it into "all signbits".
2400 Constant *Amt = ConstantInt::get(SCIOp0->getType(),
2401 SCOpTy->getPrimitiveSizeInBits()-1);
2403 InsertNewInstBefore(
2404 BinaryOperator::create(Instruction::AShr, SCIOp0, Amt,
2405 BoolCast->getOperand(0)->getName()+
2408 // If the multiply type is not the same as the source type, sign extend
2409 // or truncate to the multiply type.
2410 if (I.getType() != V->getType()) {
2411 uint32_t SrcBits = V->getType()->getPrimitiveSizeInBits();
2412 uint32_t DstBits = I.getType()->getPrimitiveSizeInBits();
2413 Instruction::CastOps opcode =
2414 (SrcBits == DstBits ? Instruction::BitCast :
2415 (SrcBits < DstBits ? Instruction::SExt : Instruction::Trunc));
2416 V = InsertCastBefore(opcode, V, I.getType(), I);
2419 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
2420 return BinaryOperator::createAnd(V, OtherOp);
2425 return Changed ? &I : 0;
2428 /// This function implements the transforms on div instructions that work
2429 /// regardless of the kind of div instruction it is (udiv, sdiv, or fdiv). It is
2430 /// used by the visitors to those instructions.
2431 /// @brief Transforms common to all three div instructions
2432 Instruction *InstCombiner::commonDivTransforms(BinaryOperator &I) {
2433 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2436 if (isa<UndefValue>(Op0))
2437 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2439 // X / undef -> undef
2440 if (isa<UndefValue>(Op1))
2441 return ReplaceInstUsesWith(I, Op1);
2443 // Handle cases involving: div X, (select Cond, Y, Z)
2444 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
2445 // div X, (Cond ? 0 : Y) -> div X, Y. If the div and the select are in the
2446 // same basic block, then we replace the select with Y, and the condition
2447 // of the select with false (if the cond value is in the same BB). If the
2448 // select has uses other than the div, this allows them to be simplified
2449 // also. Note that div X, Y is just as good as div X, 0 (undef)
2450 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
2451 if (ST->isNullValue()) {
2452 Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
2453 if (CondI && CondI->getParent() == I.getParent())
2454 UpdateValueUsesWith(CondI, ConstantInt::getFalse());
2455 else if (I.getParent() != SI->getParent() || SI->hasOneUse())
2456 I.setOperand(1, SI->getOperand(2));
2458 UpdateValueUsesWith(SI, SI->getOperand(2));
2462 // Likewise for: div X, (Cond ? Y : 0) -> div X, Y
2463 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
2464 if (ST->isNullValue()) {
2465 Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
2466 if (CondI && CondI->getParent() == I.getParent())
2467 UpdateValueUsesWith(CondI, ConstantInt::getTrue());
2468 else if (I.getParent() != SI->getParent() || SI->hasOneUse())
2469 I.setOperand(1, SI->getOperand(1));
2471 UpdateValueUsesWith(SI, SI->getOperand(1));
2479 /// This function implements the transforms common to both integer division
2480 /// instructions (udiv and sdiv). It is called by the visitors to those integer
2481 /// division instructions.
2482 /// @brief Common integer divide transforms
2483 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
2484 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2486 if (Instruction *Common = commonDivTransforms(I))
2489 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
2491 if (RHS->equalsInt(1))
2492 return ReplaceInstUsesWith(I, Op0);
2494 // (X / C1) / C2 -> X / (C1*C2)
2495 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
2496 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
2497 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
2498 return BinaryOperator::create(I.getOpcode(), LHS->getOperand(0),
2499 Multiply(RHS, LHSRHS));
2502 if (!RHS->isZero()) { // avoid X udiv 0
2503 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
2504 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2506 if (isa<PHINode>(Op0))
2507 if (Instruction *NV = FoldOpIntoPhi(I))
2512 // 0 / X == 0, we don't need to preserve faults!
2513 if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
2514 if (LHS->equalsInt(0))
2515 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2520 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
2521 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2523 // Handle the integer div common cases
2524 if (Instruction *Common = commonIDivTransforms(I))
2527 // X udiv C^2 -> X >> C
2528 // Check to see if this is an unsigned division with an exact power of 2,
2529 // if so, convert to a right shift.
2530 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
2531 if (C->getValue().isPowerOf2()) // 0 not included in isPowerOf2
2532 return BinaryOperator::createLShr(Op0,
2533 ConstantInt::get(Op0->getType(), C->getValue().logBase2()));
2536 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
2537 if (BinaryOperator *RHSI = dyn_cast<BinaryOperator>(I.getOperand(1))) {
2538 if (RHSI->getOpcode() == Instruction::Shl &&
2539 isa<ConstantInt>(RHSI->getOperand(0))) {
2540 const APInt& C1 = cast<ConstantInt>(RHSI->getOperand(0))->getValue();
2541 if (C1.isPowerOf2()) {
2542 Value *N = RHSI->getOperand(1);
2543 const Type *NTy = N->getType();
2544 if (uint32_t C2 = C1.logBase2()) {
2545 Constant *C2V = ConstantInt::get(NTy, C2);
2546 N = InsertNewInstBefore(BinaryOperator::createAdd(N, C2V, "tmp"), I);
2548 return BinaryOperator::createLShr(Op0, N);
2553 // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
2554 // where C1&C2 are powers of two.
2555 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
2556 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
2557 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
2558 const APInt &TVA = STO->getValue(), &FVA = SFO->getValue();
2559 if (TVA.isPowerOf2() && FVA.isPowerOf2()) {
2560 // Compute the shift amounts
2561 uint32_t TSA = TVA.logBase2(), FSA = FVA.logBase2();
2562 // Construct the "on true" case of the select
2563 Constant *TC = ConstantInt::get(Op0->getType(), TSA);
2564 Instruction *TSI = BinaryOperator::createLShr(
2565 Op0, TC, SI->getName()+".t");
2566 TSI = InsertNewInstBefore(TSI, I);
2568 // Construct the "on false" case of the select
2569 Constant *FC = ConstantInt::get(Op0->getType(), FSA);
2570 Instruction *FSI = BinaryOperator::createLShr(
2571 Op0, FC, SI->getName()+".f");
2572 FSI = InsertNewInstBefore(FSI, I);
2574 // construct the select instruction and return it.
2575 return new SelectInst(SI->getOperand(0), TSI, FSI, SI->getName());
2581 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
2582 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2584 // Handle the integer div common cases
2585 if (Instruction *Common = commonIDivTransforms(I))
2588 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
2590 if (RHS->isAllOnesValue())
2591 return BinaryOperator::createNeg(Op0);
2594 if (Value *LHSNeg = dyn_castNegVal(Op0))
2595 return BinaryOperator::createSDiv(LHSNeg, ConstantExpr::getNeg(RHS));
2598 // If the sign bits of both operands are zero (i.e. we can prove they are
2599 // unsigned inputs), turn this into a udiv.
2600 if (I.getType()->isInteger()) {
2601 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
2602 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
2603 return BinaryOperator::createUDiv(Op0, Op1, I.getName());
2610 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
2611 return commonDivTransforms(I);
2614 /// GetFactor - If we can prove that the specified value is at least a multiple
2615 /// of some factor, return that factor.
2616 static Constant *GetFactor(Value *V) {
2617 if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
2620 // Unless we can be tricky, we know this is a multiple of 1.
2621 Constant *Result = ConstantInt::get(V->getType(), 1);
2623 Instruction *I = dyn_cast<Instruction>(V);
2624 if (!I) return Result;
2626 if (I->getOpcode() == Instruction::Mul) {
2627 // Handle multiplies by a constant, etc.
2628 return ConstantExpr::getMul(GetFactor(I->getOperand(0)),
2629 GetFactor(I->getOperand(1)));
2630 } else if (I->getOpcode() == Instruction::Shl) {
2631 // (X<<C) -> X * (1 << C)
2632 if (Constant *ShRHS = dyn_cast<Constant>(I->getOperand(1))) {
2633 ShRHS = ConstantExpr::getShl(Result, ShRHS);
2634 return ConstantExpr::getMul(GetFactor(I->getOperand(0)), ShRHS);
2636 } else if (I->getOpcode() == Instruction::And) {
2637 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
2638 // X & 0xFFF0 is known to be a multiple of 16.
2639 uint32_t Zeros = RHS->getValue().countTrailingZeros();
2640 if (Zeros != V->getType()->getPrimitiveSizeInBits())
2641 return ConstantExpr::getShl(Result,
2642 ConstantInt::get(Result->getType(), Zeros));
2644 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
2645 // Only handle int->int casts.
2646 if (!CI->isIntegerCast())
2648 Value *Op = CI->getOperand(0);
2649 return ConstantExpr::getCast(CI->getOpcode(), GetFactor(Op), V->getType());
2654 /// This function implements the transforms on rem instructions that work
2655 /// regardless of the kind of rem instruction it is (urem, srem, or frem). It
2656 /// is used by the visitors to those instructions.
2657 /// @brief Transforms common to all three rem instructions
2658 Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
2659 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2661 // 0 % X == 0, we don't need to preserve faults!
2662 if (Constant *LHS = dyn_cast<Constant>(Op0))
2663 if (LHS->isNullValue())
2664 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2666 if (isa<UndefValue>(Op0)) // undef % X -> 0
2667 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2668 if (isa<UndefValue>(Op1))
2669 return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
2671 // Handle cases involving: rem X, (select Cond, Y, Z)
2672 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
2673 // rem X, (Cond ? 0 : Y) -> rem X, Y. If the rem and the select are in
2674 // the same basic block, then we replace the select with Y, and the
2675 // condition of the select with false (if the cond value is in the same
2676 // BB). If the select has uses other than the div, this allows them to be
2678 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
2679 if (ST->isNullValue()) {
2680 Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
2681 if (CondI && CondI->getParent() == I.getParent())
2682 UpdateValueUsesWith(CondI, ConstantInt::getFalse());
2683 else if (I.getParent() != SI->getParent() || SI->hasOneUse())
2684 I.setOperand(1, SI->getOperand(2));
2686 UpdateValueUsesWith(SI, SI->getOperand(2));
2689 // Likewise for: rem X, (Cond ? Y : 0) -> rem X, Y
2690 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
2691 if (ST->isNullValue()) {
2692 Instruction *CondI = dyn_cast<Instruction>(SI->getOperand(0));
2693 if (CondI && CondI->getParent() == I.getParent())
2694 UpdateValueUsesWith(CondI, ConstantInt::getTrue());
2695 else if (I.getParent() != SI->getParent() || SI->hasOneUse())
2696 I.setOperand(1, SI->getOperand(1));
2698 UpdateValueUsesWith(SI, SI->getOperand(1));
2706 /// This function implements the transforms common to both integer remainder
2707 /// instructions (urem and srem). It is called by the visitors to those integer
2708 /// remainder instructions.
2709 /// @brief Common integer remainder transforms
2710 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
2711 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2713 if (Instruction *common = commonRemTransforms(I))
2716 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
2717 // X % 0 == undef, we don't need to preserve faults!
2718 if (RHS->equalsInt(0))
2719 return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
2721 if (RHS->equalsInt(1)) // X % 1 == 0
2722 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2724 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
2725 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
2726 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2728 } else if (isa<PHINode>(Op0I)) {
2729 if (Instruction *NV = FoldOpIntoPhi(I))
2732 // (X * C1) % C2 --> 0 iff C1 % C2 == 0
2733 if (ConstantExpr::getSRem(GetFactor(Op0I), RHS)->isNullValue())
2734 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2741 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
2742 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2744 if (Instruction *common = commonIRemTransforms(I))
2747 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
2748 // X urem C^2 -> X and C
2749 // Check to see if this is an unsigned remainder with an exact power of 2,
2750 // if so, convert to a bitwise and.
2751 if (ConstantInt *C = dyn_cast<ConstantInt>(RHS))
2752 if (C->getValue().isPowerOf2())
2753 return BinaryOperator::createAnd(Op0, SubOne(C));
2756 if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
2757 // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
2758 if (RHSI->getOpcode() == Instruction::Shl &&
2759 isa<ConstantInt>(RHSI->getOperand(0))) {
2760 if (cast<ConstantInt>(RHSI->getOperand(0))->getValue().isPowerOf2()) {
2761 Constant *N1 = ConstantInt::getAllOnesValue(I.getType());
2762 Value *Add = InsertNewInstBefore(BinaryOperator::createAdd(RHSI, N1,
2764 return BinaryOperator::createAnd(Op0, Add);
2769 // urem X, (select Cond, 2^C1, 2^C2) --> select Cond, (and X, C1), (and X, C2)
2770 // where C1&C2 are powers of two.
2771 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
2772 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
2773 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
2774 // STO == 0 and SFO == 0 handled above.
2775 if ((STO->getValue().isPowerOf2()) &&
2776 (SFO->getValue().isPowerOf2())) {
2777 Value *TrueAnd = InsertNewInstBefore(
2778 BinaryOperator::createAnd(Op0, SubOne(STO), SI->getName()+".t"), I);
2779 Value *FalseAnd = InsertNewInstBefore(
2780 BinaryOperator::createAnd(Op0, SubOne(SFO), SI->getName()+".f"), I);
2781 return new SelectInst(SI->getOperand(0), TrueAnd, FalseAnd);
2789 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
2790 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2792 if (Instruction *common = commonIRemTransforms(I))
2795 if (Value *RHSNeg = dyn_castNegVal(Op1))
2796 if (!isa<ConstantInt>(RHSNeg) ||
2797 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive()) {
2799 AddUsesToWorkList(I);
2800 I.setOperand(1, RHSNeg);
2804 // If the top bits of both operands are zero (i.e. we can prove they are
2805 // unsigned inputs), turn this into a urem.
2806 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
2807 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
2808 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
2809 return BinaryOperator::createURem(Op0, Op1, I.getName());
2815 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
2816 return commonRemTransforms(I);
2819 // isMaxValueMinusOne - return true if this is Max-1
2820 static bool isMaxValueMinusOne(const ConstantInt *C, bool isSigned) {
2821 uint32_t TypeBits = C->getType()->getPrimitiveSizeInBits();
2823 return C->getValue() == APInt::getAllOnesValue(TypeBits) - 1;
2824 return C->getValue() == APInt::getSignedMaxValue(TypeBits)-1;
2827 // isMinValuePlusOne - return true if this is Min+1
2828 static bool isMinValuePlusOne(const ConstantInt *C, bool isSigned) {
2830 return C->getValue() == 1; // unsigned
2832 // Calculate 1111111111000000000000
2833 uint32_t TypeBits = C->getType()->getPrimitiveSizeInBits();
2834 return C->getValue() == APInt::getSignedMinValue(TypeBits)+1;
2837 // isOneBitSet - Return true if there is exactly one bit set in the specified
2839 static bool isOneBitSet(const ConstantInt *CI) {
2840 return CI->getValue().isPowerOf2();
2843 // isHighOnes - Return true if the constant is of the form 1+0+.
2844 // This is the same as lowones(~X).
2845 static bool isHighOnes(const ConstantInt *CI) {
2846 return (~CI->getValue() + 1).isPowerOf2();
2849 /// getICmpCode - Encode a icmp predicate into a three bit mask. These bits
2850 /// are carefully arranged to allow folding of expressions such as:
2852 /// (A < B) | (A > B) --> (A != B)
2854 /// Note that this is only valid if the first and second predicates have the
2855 /// same sign. Is illegal to do: (A u< B) | (A s> B)
2857 /// Three bits are used to represent the condition, as follows:
2862 /// <=> Value Definition
2863 /// 000 0 Always false
2870 /// 111 7 Always true
2872 static unsigned getICmpCode(const ICmpInst *ICI) {
2873 switch (ICI->getPredicate()) {
2875 case ICmpInst::ICMP_UGT: return 1; // 001
2876 case ICmpInst::ICMP_SGT: return 1; // 001
2877 case ICmpInst::ICMP_EQ: return 2; // 010
2878 case ICmpInst::ICMP_UGE: return 3; // 011
2879 case ICmpInst::ICMP_SGE: return 3; // 011
2880 case ICmpInst::ICMP_ULT: return 4; // 100
2881 case ICmpInst::ICMP_SLT: return 4; // 100
2882 case ICmpInst::ICMP_NE: return 5; // 101
2883 case ICmpInst::ICMP_ULE: return 6; // 110
2884 case ICmpInst::ICMP_SLE: return 6; // 110
2887 assert(0 && "Invalid ICmp predicate!");
2892 /// getICmpValue - This is the complement of getICmpCode, which turns an
2893 /// opcode and two operands into either a constant true or false, or a brand
2894 /// new /// ICmp instruction. The sign is passed in to determine which kind
2895 /// of predicate to use in new icmp instructions.
2896 static Value *getICmpValue(bool sign, unsigned code, Value *LHS, Value *RHS) {
2898 default: assert(0 && "Illegal ICmp code!");
2899 case 0: return ConstantInt::getFalse();
2902 return new ICmpInst(ICmpInst::ICMP_SGT, LHS, RHS);
2904 return new ICmpInst(ICmpInst::ICMP_UGT, LHS, RHS);
2905 case 2: return new ICmpInst(ICmpInst::ICMP_EQ, LHS, RHS);
2908 return new ICmpInst(ICmpInst::ICMP_SGE, LHS, RHS);
2910 return new ICmpInst(ICmpInst::ICMP_UGE, LHS, RHS);
2913 return new ICmpInst(ICmpInst::ICMP_SLT, LHS, RHS);
2915 return new ICmpInst(ICmpInst::ICMP_ULT, LHS, RHS);
2916 case 5: return new ICmpInst(ICmpInst::ICMP_NE, LHS, RHS);
2919 return new ICmpInst(ICmpInst::ICMP_SLE, LHS, RHS);
2921 return new ICmpInst(ICmpInst::ICMP_ULE, LHS, RHS);
2922 case 7: return ConstantInt::getTrue();
2926 static bool PredicatesFoldable(ICmpInst::Predicate p1, ICmpInst::Predicate p2) {
2927 return (ICmpInst::isSignedPredicate(p1) == ICmpInst::isSignedPredicate(p2)) ||
2928 (ICmpInst::isSignedPredicate(p1) &&
2929 (p2 == ICmpInst::ICMP_EQ || p2 == ICmpInst::ICMP_NE)) ||
2930 (ICmpInst::isSignedPredicate(p2) &&
2931 (p1 == ICmpInst::ICMP_EQ || p1 == ICmpInst::ICMP_NE));
2935 // FoldICmpLogical - Implements (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
2936 struct FoldICmpLogical {
2939 ICmpInst::Predicate pred;
2940 FoldICmpLogical(InstCombiner &ic, ICmpInst *ICI)
2941 : IC(ic), LHS(ICI->getOperand(0)), RHS(ICI->getOperand(1)),
2942 pred(ICI->getPredicate()) {}
2943 bool shouldApply(Value *V) const {
2944 if (ICmpInst *ICI = dyn_cast<ICmpInst>(V))
2945 if (PredicatesFoldable(pred, ICI->getPredicate()))
2946 return (ICI->getOperand(0) == LHS && ICI->getOperand(1) == RHS ||
2947 ICI->getOperand(0) == RHS && ICI->getOperand(1) == LHS);
2950 Instruction *apply(Instruction &Log) const {
2951 ICmpInst *ICI = cast<ICmpInst>(Log.getOperand(0));
2952 if (ICI->getOperand(0) != LHS) {
2953 assert(ICI->getOperand(1) == LHS);
2954 ICI->swapOperands(); // Swap the LHS and RHS of the ICmp
2957 ICmpInst *RHSICI = cast<ICmpInst>(Log.getOperand(1));
2958 unsigned LHSCode = getICmpCode(ICI);
2959 unsigned RHSCode = getICmpCode(RHSICI);
2961 switch (Log.getOpcode()) {
2962 case Instruction::And: Code = LHSCode & RHSCode; break;
2963 case Instruction::Or: Code = LHSCode | RHSCode; break;
2964 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
2965 default: assert(0 && "Illegal logical opcode!"); return 0;
2968 bool isSigned = ICmpInst::isSignedPredicate(RHSICI->getPredicate()) ||
2969 ICmpInst::isSignedPredicate(ICI->getPredicate());
2971 Value *RV = getICmpValue(isSigned, Code, LHS, RHS);
2972 if (Instruction *I = dyn_cast<Instruction>(RV))
2974 // Otherwise, it's a constant boolean value...
2975 return IC.ReplaceInstUsesWith(Log, RV);
2978 } // end anonymous namespace
2980 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
2981 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
2982 // guaranteed to be a binary operator.
2983 Instruction *InstCombiner::OptAndOp(Instruction *Op,
2985 ConstantInt *AndRHS,
2986 BinaryOperator &TheAnd) {
2987 Value *X = Op->getOperand(0);
2988 Constant *Together = 0;
2990 Together = And(AndRHS, OpRHS);
2992 switch (Op->getOpcode()) {
2993 case Instruction::Xor:
2994 if (Op->hasOneUse()) {
2995 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
2996 Instruction *And = BinaryOperator::createAnd(X, AndRHS);
2997 InsertNewInstBefore(And, TheAnd);
2999 return BinaryOperator::createXor(And, Together);
3002 case Instruction::Or:
3003 if (Together == AndRHS) // (X | C) & C --> C
3004 return ReplaceInstUsesWith(TheAnd, AndRHS);
3006 if (Op->hasOneUse() && Together != OpRHS) {
3007 // (X | C1) & C2 --> (X | (C1&C2)) & C2
3008 Instruction *Or = BinaryOperator::createOr(X, Together);
3009 InsertNewInstBefore(Or, TheAnd);
3011 return BinaryOperator::createAnd(Or, AndRHS);
3014 case Instruction::Add:
3015 if (Op->hasOneUse()) {
3016 // Adding a one to a single bit bit-field should be turned into an XOR
3017 // of the bit. First thing to check is to see if this AND is with a
3018 // single bit constant.
3019 const APInt& AndRHSV = cast<ConstantInt>(AndRHS)->getValue();
3021 // If there is only one bit set...
3022 if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
3023 // Ok, at this point, we know that we are masking the result of the
3024 // ADD down to exactly one bit. If the constant we are adding has
3025 // no bits set below this bit, then we can eliminate the ADD.
3026 const APInt& AddRHS = cast<ConstantInt>(OpRHS)->getValue();
3028 // Check to see if any bits below the one bit set in AndRHSV are set.
3029 if ((AddRHS & (AndRHSV-1)) == 0) {
3030 // If not, the only thing that can effect the output of the AND is
3031 // the bit specified by AndRHSV. If that bit is set, the effect of
3032 // the XOR is to toggle the bit. If it is clear, then the ADD has
3034 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
3035 TheAnd.setOperand(0, X);
3038 // Pull the XOR out of the AND.
3039 Instruction *NewAnd = BinaryOperator::createAnd(X, AndRHS);
3040 InsertNewInstBefore(NewAnd, TheAnd);
3041 NewAnd->takeName(Op);
3042 return BinaryOperator::createXor(NewAnd, AndRHS);
3049 case Instruction::Shl: {
3050 // We know that the AND will not produce any of the bits shifted in, so if
3051 // the anded constant includes them, clear them now!
3053 uint32_t BitWidth = AndRHS->getType()->getBitWidth();
3054 uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
3055 APInt ShlMask(APInt::getHighBitsSet(BitWidth, BitWidth-OpRHSVal));
3056 ConstantInt *CI = ConstantInt::get(AndRHS->getValue() & ShlMask);
3058 if (CI->getValue() == ShlMask) {
3059 // Masking out bits that the shift already masks
3060 return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
3061 } else if (CI != AndRHS) { // Reducing bits set in and.
3062 TheAnd.setOperand(1, CI);
3067 case Instruction::LShr:
3069 // We know that the AND will not produce any of the bits shifted in, so if
3070 // the anded constant includes them, clear them now! This only applies to
3071 // unsigned shifts, because a signed shr may bring in set bits!
3073 uint32_t BitWidth = AndRHS->getType()->getBitWidth();
3074 uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
3075 APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
3076 ConstantInt *CI = ConstantInt::get(AndRHS->getValue() & ShrMask);
3078 if (CI->getValue() == ShrMask) {
3079 // Masking out bits that the shift already masks.
3080 return ReplaceInstUsesWith(TheAnd, Op);
3081 } else if (CI != AndRHS) {
3082 TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
3087 case Instruction::AShr:
3089 // See if this is shifting in some sign extension, then masking it out
3091 if (Op->hasOneUse()) {
3092 uint32_t BitWidth = AndRHS->getType()->getBitWidth();
3093 uint32_t OpRHSVal = OpRHS->getLimitedValue(BitWidth);
3094 APInt ShrMask(APInt::getLowBitsSet(BitWidth, BitWidth - OpRHSVal));
3095 Constant *C = ConstantInt::get(AndRHS->getValue() & ShrMask);
3096 if (C == AndRHS) { // Masking out bits shifted in.
3097 // (Val ashr C1) & C2 -> (Val lshr C1) & C2
3098 // Make the argument unsigned.
3099 Value *ShVal = Op->getOperand(0);
3100 ShVal = InsertNewInstBefore(
3101 BinaryOperator::createLShr(ShVal, OpRHS,
3102 Op->getName()), TheAnd);
3103 return BinaryOperator::createAnd(ShVal, AndRHS, TheAnd.getName());
3112 /// InsertRangeTest - Emit a computation of: (V >= Lo && V < Hi) if Inside is
3113 /// true, otherwise (V < Lo || V >= Hi). In pratice, we emit the more efficient
3114 /// (V-Lo) <u Hi-Lo. This method expects that Lo <= Hi. isSigned indicates
3115 /// whether to treat the V, Lo and HI as signed or not. IB is the location to
3116 /// insert new instructions.
3117 Instruction *InstCombiner::InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
3118 bool isSigned, bool Inside,
3120 assert(cast<ConstantInt>(ConstantExpr::getICmp((isSigned ?
3121 ICmpInst::ICMP_SLE:ICmpInst::ICMP_ULE), Lo, Hi))->getZExtValue() &&
3122 "Lo is not <= Hi in range emission code!");
3125 if (Lo == Hi) // Trivially false.
3126 return new ICmpInst(ICmpInst::ICMP_NE, V, V);
3128 // V >= Min && V < Hi --> V < Hi
3129 if (cast<ConstantInt>(Lo)->isMinValue(isSigned)) {
3130 ICmpInst::Predicate pred = (isSigned ?
3131 ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT);
3132 return new ICmpInst(pred, V, Hi);
3135 // Emit V-Lo <u Hi-Lo
3136 Constant *NegLo = ConstantExpr::getNeg(Lo);
3137 Instruction *Add = BinaryOperator::createAdd(V, NegLo, V->getName()+".off");
3138 InsertNewInstBefore(Add, IB);
3139 Constant *UpperBound = ConstantExpr::getAdd(NegLo, Hi);
3140 return new ICmpInst(ICmpInst::ICMP_ULT, Add, UpperBound);
3143 if (Lo == Hi) // Trivially true.
3144 return new ICmpInst(ICmpInst::ICMP_EQ, V, V);
3146 // V < Min || V >= Hi -> V > Hi-1
3147 Hi = SubOne(cast<ConstantInt>(Hi));
3148 if (cast<ConstantInt>(Lo)->isMinValue(isSigned)) {
3149 ICmpInst::Predicate pred = (isSigned ?
3150 ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT);
3151 return new ICmpInst(pred, V, Hi);
3154 // Emit V-Lo >u Hi-1-Lo
3155 // Note that Hi has already had one subtracted from it, above.
3156 ConstantInt *NegLo = cast<ConstantInt>(ConstantExpr::getNeg(Lo));
3157 Instruction *Add = BinaryOperator::createAdd(V, NegLo, V->getName()+".off");
3158 InsertNewInstBefore(Add, IB);
3159 Constant *LowerBound = ConstantExpr::getAdd(NegLo, Hi);
3160 return new ICmpInst(ICmpInst::ICMP_UGT, Add, LowerBound);
3163 // isRunOfOnes - Returns true iff Val consists of one contiguous run of 1s with
3164 // any number of 0s on either side. The 1s are allowed to wrap from LSB to
3165 // MSB, so 0x000FFF0, 0x0000FFFF, and 0xFF0000FF are all runs. 0x0F0F0000 is
3166 // not, since all 1s are not contiguous.
3167 static bool isRunOfOnes(ConstantInt *Val, uint32_t &MB, uint32_t &ME) {
3168 const APInt& V = Val->getValue();
3169 uint32_t BitWidth = Val->getType()->getBitWidth();
3170 if (!APIntOps::isShiftedMask(BitWidth, V)) return false;
3172 // look for the first zero bit after the run of ones
3173 MB = BitWidth - ((V - 1) ^ V).countLeadingZeros();
3174 // look for the first non-zero bit
3175 ME = V.getActiveBits();
3179 /// FoldLogicalPlusAnd - This is part of an expression (LHS +/- RHS) & Mask,
3180 /// where isSub determines whether the operator is a sub. If we can fold one of
3181 /// the following xforms:
3183 /// ((A & N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == Mask
3184 /// ((A | N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
3185 /// ((A ^ N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
3187 /// return (A +/- B).
3189 Value *InstCombiner::FoldLogicalPlusAnd(Value *LHS, Value *RHS,
3190 ConstantInt *Mask, bool isSub,
3192 Instruction *LHSI = dyn_cast<Instruction>(LHS);
3193 if (!LHSI || LHSI->getNumOperands() != 2 ||
3194 !isa<ConstantInt>(LHSI->getOperand(1))) return 0;
3196 ConstantInt *N = cast<ConstantInt>(LHSI->getOperand(1));
3198 switch (LHSI->getOpcode()) {
3200 case Instruction::And:
3201 if (And(N, Mask) == Mask) {
3202 // If the AndRHS is a power of two minus one (0+1+), this is simple.
3203 if ((Mask->getValue().countLeadingZeros() +
3204 Mask->getValue().countPopulation()) ==
3205 Mask->getValue().getBitWidth())
3208 // Otherwise, if Mask is 0+1+0+, and if B is known to have the low 0+
3209 // part, we don't need any explicit masks to take them out of A. If that
3210 // is all N is, ignore it.
3211 uint32_t MB = 0, ME = 0;
3212 if (isRunOfOnes(Mask, MB, ME)) { // begin/end bit of run, inclusive
3213 uint32_t BitWidth = cast<IntegerType>(RHS->getType())->getBitWidth();
3214 APInt Mask(APInt::getLowBitsSet(BitWidth, MB-1));
3215 if (MaskedValueIsZero(RHS, Mask))
3220 case Instruction::Or:
3221 case Instruction::Xor:
3222 // If the AndRHS is a power of two minus one (0+1+), and N&Mask == 0
3223 if ((Mask->getValue().countLeadingZeros() +
3224 Mask->getValue().countPopulation()) == Mask->getValue().getBitWidth()
3225 && And(N, Mask)->isZero())
3232 New = BinaryOperator::createSub(LHSI->getOperand(0), RHS, "fold");
3234 New = BinaryOperator::createAdd(LHSI->getOperand(0), RHS, "fold");
3235 return InsertNewInstBefore(New, I);
3238 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
3239 bool Changed = SimplifyCommutative(I);
3240 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3242 if (isa<UndefValue>(Op1)) // X & undef -> 0
3243 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
3247 return ReplaceInstUsesWith(I, Op1);
3249 // See if we can simplify any instructions used by the instruction whose sole
3250 // purpose is to compute bits we don't care about.
3251 if (!isa<VectorType>(I.getType())) {
3252 uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
3253 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3254 if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
3255 KnownZero, KnownOne))
3258 if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) {
3259 if (CP->isAllOnesValue()) // X & <-1,-1> -> X
3260 return ReplaceInstUsesWith(I, I.getOperand(0));
3261 } else if (isa<ConstantAggregateZero>(Op1)) {
3262 return ReplaceInstUsesWith(I, Op1); // X & <0,0> -> <0,0>
3266 if (ConstantInt *AndRHS = dyn_cast<ConstantInt>(Op1)) {
3267 const APInt& AndRHSMask = AndRHS->getValue();
3268 APInt NotAndRHS(~AndRHSMask);
3270 // Optimize a variety of ((val OP C1) & C2) combinations...
3271 if (isa<BinaryOperator>(Op0)) {
3272 Instruction *Op0I = cast<Instruction>(Op0);
3273 Value *Op0LHS = Op0I->getOperand(0);
3274 Value *Op0RHS = Op0I->getOperand(1);
3275 switch (Op0I->getOpcode()) {
3276 case Instruction::Xor:
3277 case Instruction::Or:
3278 // If the mask is only needed on one incoming arm, push it up.
3279 if (Op0I->hasOneUse()) {
3280 if (MaskedValueIsZero(Op0LHS, NotAndRHS)) {
3281 // Not masking anything out for the LHS, move to RHS.
3282 Instruction *NewRHS = BinaryOperator::createAnd(Op0RHS, AndRHS,
3283 Op0RHS->getName()+".masked");
3284 InsertNewInstBefore(NewRHS, I);
3285 return BinaryOperator::create(
3286 cast<BinaryOperator>(Op0I)->getOpcode(), Op0LHS, NewRHS);
3288 if (!isa<Constant>(Op0RHS) &&
3289 MaskedValueIsZero(Op0RHS, NotAndRHS)) {
3290 // Not masking anything out for the RHS, move to LHS.
3291 Instruction *NewLHS = BinaryOperator::createAnd(Op0LHS, AndRHS,
3292 Op0LHS->getName()+".masked");
3293 InsertNewInstBefore(NewLHS, I);
3294 return BinaryOperator::create(
3295 cast<BinaryOperator>(Op0I)->getOpcode(), NewLHS, Op0RHS);
3300 case Instruction::Add:
3301 // ((A & N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == AndRHS.
3302 // ((A | N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
3303 // ((A ^ N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
3304 if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
3305 return BinaryOperator::createAnd(V, AndRHS);
3306 if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
3307 return BinaryOperator::createAnd(V, AndRHS); // Add commutes
3310 case Instruction::Sub:
3311 // ((A & N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == AndRHS.
3312 // ((A | N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
3313 // ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
3314 if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
3315 return BinaryOperator::createAnd(V, AndRHS);
3319 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
3320 if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
3322 } else if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
3323 // If this is an integer truncation or change from signed-to-unsigned, and
3324 // if the source is an and/or with immediate, transform it. This
3325 // frequently occurs for bitfield accesses.
3326 if (Instruction *CastOp = dyn_cast<Instruction>(CI->getOperand(0))) {
3327 if ((isa<TruncInst>(CI) || isa<BitCastInst>(CI)) &&
3328 CastOp->getNumOperands() == 2)
3329 if (ConstantInt *AndCI = dyn_cast<ConstantInt>(CastOp->getOperand(1)))
3330 if (CastOp->getOpcode() == Instruction::And) {
3331 // Change: and (cast (and X, C1) to T), C2
3332 // into : and (cast X to T), trunc_or_bitcast(C1)&C2
3333 // This will fold the two constants together, which may allow
3334 // other simplifications.
3335 Instruction *NewCast = CastInst::createTruncOrBitCast(
3336 CastOp->getOperand(0), I.getType(),
3337 CastOp->getName()+".shrunk");
3338 NewCast = InsertNewInstBefore(NewCast, I);
3339 // trunc_or_bitcast(C1)&C2
3340 Constant *C3 = ConstantExpr::getTruncOrBitCast(AndCI,I.getType());
3341 C3 = ConstantExpr::getAnd(C3, AndRHS);
3342 return BinaryOperator::createAnd(NewCast, C3);
3343 } else if (CastOp->getOpcode() == Instruction::Or) {
3344 // Change: and (cast (or X, C1) to T), C2
3345 // into : trunc(C1)&C2 iff trunc(C1)&C2 == C2
3346 Constant *C3 = ConstantExpr::getTruncOrBitCast(AndCI,I.getType());
3347 if (ConstantExpr::getAnd(C3, AndRHS) == AndRHS) // trunc(C1)&C2
3348 return ReplaceInstUsesWith(I, AndRHS);
3353 // Try to fold constant and into select arguments.
3354 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
3355 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
3357 if (isa<PHINode>(Op0))
3358 if (Instruction *NV = FoldOpIntoPhi(I))
3362 Value *Op0NotVal = dyn_castNotVal(Op0);
3363 Value *Op1NotVal = dyn_castNotVal(Op1);
3365 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
3366 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
3368 // (~A & ~B) == (~(A | B)) - De Morgan's Law
3369 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
3370 Instruction *Or = BinaryOperator::createOr(Op0NotVal, Op1NotVal,
3371 I.getName()+".demorgan");
3372 InsertNewInstBefore(Or, I);
3373 return BinaryOperator::createNot(Or);
3377 Value *A = 0, *B = 0, *C = 0, *D = 0;
3378 if (match(Op0, m_Or(m_Value(A), m_Value(B)))) {
3379 if (A == Op1 || B == Op1) // (A | ?) & A --> A
3380 return ReplaceInstUsesWith(I, Op1);
3382 // (A|B) & ~(A&B) -> A^B
3383 if (match(Op1, m_Not(m_And(m_Value(C), m_Value(D))))) {
3384 if ((A == C && B == D) || (A == D && B == C))
3385 return BinaryOperator::createXor(A, B);
3389 if (match(Op1, m_Or(m_Value(A), m_Value(B)))) {
3390 if (A == Op0 || B == Op0) // A & (A | ?) --> A
3391 return ReplaceInstUsesWith(I, Op0);
3393 // ~(A&B) & (A|B) -> A^B
3394 if (match(Op0, m_Not(m_And(m_Value(C), m_Value(D))))) {
3395 if ((A == C && B == D) || (A == D && B == C))
3396 return BinaryOperator::createXor(A, B);
3400 if (Op0->hasOneUse() &&
3401 match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3402 if (A == Op1) { // (A^B)&A -> A&(A^B)
3403 I.swapOperands(); // Simplify below
3404 std::swap(Op0, Op1);
3405 } else if (B == Op1) { // (A^B)&B -> B&(B^A)
3406 cast<BinaryOperator>(Op0)->swapOperands();
3407 I.swapOperands(); // Simplify below
3408 std::swap(Op0, Op1);
3411 if (Op1->hasOneUse() &&
3412 match(Op1, m_Xor(m_Value(A), m_Value(B)))) {
3413 if (B == Op0) { // B&(A^B) -> B&(B^A)
3414 cast<BinaryOperator>(Op1)->swapOperands();
3417 if (A == Op0) { // A&(A^B) -> A & ~B
3418 Instruction *NotB = BinaryOperator::createNot(B, "tmp");
3419 InsertNewInstBefore(NotB, I);
3420 return BinaryOperator::createAnd(A, NotB);
3425 if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1)) {
3426 // (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
3427 if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
3430 Value *LHSVal, *RHSVal;
3431 ConstantInt *LHSCst, *RHSCst;
3432 ICmpInst::Predicate LHSCC, RHSCC;
3433 if (match(Op0, m_ICmp(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
3434 if (match(RHS, m_ICmp(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
3435 if (LHSVal == RHSVal && // Found (X icmp C1) & (X icmp C2)
3436 // ICMP_[GL]E X, CST is folded to ICMP_[GL]T elsewhere.
3437 LHSCC != ICmpInst::ICMP_UGE && LHSCC != ICmpInst::ICMP_ULE &&
3438 RHSCC != ICmpInst::ICMP_UGE && RHSCC != ICmpInst::ICMP_ULE &&
3439 LHSCC != ICmpInst::ICMP_SGE && LHSCC != ICmpInst::ICMP_SLE &&
3440 RHSCC != ICmpInst::ICMP_SGE && RHSCC != ICmpInst::ICMP_SLE) {
3441 // Ensure that the larger constant is on the RHS.
3442 ICmpInst::Predicate GT = ICmpInst::isSignedPredicate(LHSCC) ?
3443 ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
3444 Constant *Cmp = ConstantExpr::getICmp(GT, LHSCst, RHSCst);
3445 ICmpInst *LHS = cast<ICmpInst>(Op0);
3446 if (cast<ConstantInt>(Cmp)->getZExtValue()) {
3447 std::swap(LHS, RHS);
3448 std::swap(LHSCst, RHSCst);
3449 std::swap(LHSCC, RHSCC);
3452 // At this point, we know we have have two icmp instructions
3453 // comparing a value against two constants and and'ing the result
3454 // together. Because of the above check, we know that we only have
3455 // icmp eq, icmp ne, icmp [su]lt, and icmp [SU]gt here. We also know
3456 // (from the FoldICmpLogical check above), that the two constants
3457 // are not equal and that the larger constant is on the RHS
3458 assert(LHSCst != RHSCst && "Compares not folded above?");
3461 default: assert(0 && "Unknown integer condition code!");
3462 case ICmpInst::ICMP_EQ:
3464 default: assert(0 && "Unknown integer condition code!");
3465 case ICmpInst::ICMP_EQ: // (X == 13 & X == 15) -> false
3466 case ICmpInst::ICMP_UGT: // (X == 13 & X > 15) -> false
3467 case ICmpInst::ICMP_SGT: // (X == 13 & X > 15) -> false
3468 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
3469 case ICmpInst::ICMP_NE: // (X == 13 & X != 15) -> X == 13
3470 case ICmpInst::ICMP_ULT: // (X == 13 & X < 15) -> X == 13
3471 case ICmpInst::ICMP_SLT: // (X == 13 & X < 15) -> X == 13
3472 return ReplaceInstUsesWith(I, LHS);
3474 case ICmpInst::ICMP_NE:
3476 default: assert(0 && "Unknown integer condition code!");
3477 case ICmpInst::ICMP_ULT:
3478 if (LHSCst == SubOne(RHSCst)) // (X != 13 & X u< 14) -> X < 13
3479 return new ICmpInst(ICmpInst::ICMP_ULT, LHSVal, LHSCst);
3480 break; // (X != 13 & X u< 15) -> no change
3481 case ICmpInst::ICMP_SLT:
3482 if (LHSCst == SubOne(RHSCst)) // (X != 13 & X s< 14) -> X < 13
3483 return new ICmpInst(ICmpInst::ICMP_SLT, LHSVal, LHSCst);
3484 break; // (X != 13 & X s< 15) -> no change
3485 case ICmpInst::ICMP_EQ: // (X != 13 & X == 15) -> X == 15
3486 case ICmpInst::ICMP_UGT: // (X != 13 & X u> 15) -> X u> 15
3487 case ICmpInst::ICMP_SGT: // (X != 13 & X s> 15) -> X s> 15
3488 return ReplaceInstUsesWith(I, RHS);
3489 case ICmpInst::ICMP_NE:
3490 if (LHSCst == SubOne(RHSCst)){// (X != 13 & X != 14) -> X-13 >u 1
3491 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
3492 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
3493 LHSVal->getName()+".off");
3494 InsertNewInstBefore(Add, I);
3495 return new ICmpInst(ICmpInst::ICMP_UGT, Add,
3496 ConstantInt::get(Add->getType(), 1));
3498 break; // (X != 13 & X != 15) -> no change
3501 case ICmpInst::ICMP_ULT:
3503 default: assert(0 && "Unknown integer condition code!");
3504 case ICmpInst::ICMP_EQ: // (X u< 13 & X == 15) -> false
3505 case ICmpInst::ICMP_UGT: // (X u< 13 & X u> 15) -> false
3506 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
3507 case ICmpInst::ICMP_SGT: // (X u< 13 & X s> 15) -> no change
3509 case ICmpInst::ICMP_NE: // (X u< 13 & X != 15) -> X u< 13
3510 case ICmpInst::ICMP_ULT: // (X u< 13 & X u< 15) -> X u< 13
3511 return ReplaceInstUsesWith(I, LHS);
3512 case ICmpInst::ICMP_SLT: // (X u< 13 & X s< 15) -> no change
3516 case ICmpInst::ICMP_SLT:
3518 default: assert(0 && "Unknown integer condition code!");
3519 case ICmpInst::ICMP_EQ: // (X s< 13 & X == 15) -> false
3520 case ICmpInst::ICMP_SGT: // (X s< 13 & X s> 15) -> false
3521 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
3522 case ICmpInst::ICMP_UGT: // (X s< 13 & X u> 15) -> no change
3524 case ICmpInst::ICMP_NE: // (X s< 13 & X != 15) -> X < 13
3525 case ICmpInst::ICMP_SLT: // (X s< 13 & X s< 15) -> X < 13
3526 return ReplaceInstUsesWith(I, LHS);
3527 case ICmpInst::ICMP_ULT: // (X s< 13 & X u< 15) -> no change
3531 case ICmpInst::ICMP_UGT:
3533 default: assert(0 && "Unknown integer condition code!");
3534 case ICmpInst::ICMP_EQ: // (X u> 13 & X == 15) -> X > 13
3535 return ReplaceInstUsesWith(I, LHS);
3536 case ICmpInst::ICMP_UGT: // (X u> 13 & X u> 15) -> X u> 15
3537 return ReplaceInstUsesWith(I, RHS);
3538 case ICmpInst::ICMP_SGT: // (X u> 13 & X s> 15) -> no change
3540 case ICmpInst::ICMP_NE:
3541 if (RHSCst == AddOne(LHSCst)) // (X u> 13 & X != 14) -> X u> 14
3542 return new ICmpInst(LHSCC, LHSVal, RHSCst);
3543 break; // (X u> 13 & X != 15) -> no change
3544 case ICmpInst::ICMP_ULT: // (X u> 13 & X u< 15) ->(X-14) <u 1
3545 return InsertRangeTest(LHSVal, AddOne(LHSCst), RHSCst, false,
3547 case ICmpInst::ICMP_SLT: // (X u> 13 & X s< 15) -> no change
3551 case ICmpInst::ICMP_SGT:
3553 default: assert(0 && "Unknown integer condition code!");
3554 case ICmpInst::ICMP_EQ: // (X s> 13 & X == 15) -> X s> 13
3555 return ReplaceInstUsesWith(I, LHS);
3556 case ICmpInst::ICMP_SGT: // (X s> 13 & X s> 15) -> X s> 15
3557 return ReplaceInstUsesWith(I, RHS);
3558 case ICmpInst::ICMP_UGT: // (X s> 13 & X u> 15) -> no change
3560 case ICmpInst::ICMP_NE:
3561 if (RHSCst == AddOne(LHSCst)) // (X s> 13 & X != 14) -> X s> 14
3562 return new ICmpInst(LHSCC, LHSVal, RHSCst);
3563 break; // (X s> 13 & X != 15) -> no change
3564 case ICmpInst::ICMP_SLT: // (X s> 13 & X s< 15) ->(X-14) s< 1
3565 return InsertRangeTest(LHSVal, AddOne(LHSCst), RHSCst, true,
3567 case ICmpInst::ICMP_ULT: // (X s> 13 & X u< 15) -> no change
3575 // fold (and (cast A), (cast B)) -> (cast (and A, B))
3576 if (CastInst *Op0C = dyn_cast<CastInst>(Op0))
3577 if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
3578 if (Op0C->getOpcode() == Op1C->getOpcode()) { // same cast kind ?
3579 const Type *SrcTy = Op0C->getOperand(0)->getType();
3580 if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
3581 // Only do this if the casts both really cause code to be generated.
3582 ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
3584 ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
3586 Instruction *NewOp = BinaryOperator::createAnd(Op0C->getOperand(0),
3587 Op1C->getOperand(0),
3589 InsertNewInstBefore(NewOp, I);
3590 return CastInst::create(Op0C->getOpcode(), NewOp, I.getType());
3594 // (X >> Z) & (Y >> Z) -> (X&Y) >> Z for all shifts.
3595 if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
3596 if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
3597 if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
3598 SI0->getOperand(1) == SI1->getOperand(1) &&
3599 (SI0->hasOneUse() || SI1->hasOneUse())) {
3600 Instruction *NewOp =
3601 InsertNewInstBefore(BinaryOperator::createAnd(SI0->getOperand(0),
3603 SI0->getName()), I);
3604 return BinaryOperator::create(SI1->getOpcode(), NewOp,
3605 SI1->getOperand(1));
3609 return Changed ? &I : 0;
3612 /// CollectBSwapParts - Look to see if the specified value defines a single byte
3613 /// in the result. If it does, and if the specified byte hasn't been filled in
3614 /// yet, fill it in and return false.
3615 static bool CollectBSwapParts(Value *V, SmallVector<Value*, 8> &ByteValues) {
3616 Instruction *I = dyn_cast<Instruction>(V);
3617 if (I == 0) return true;
3619 // If this is an or instruction, it is an inner node of the bswap.
3620 if (I->getOpcode() == Instruction::Or)
3621 return CollectBSwapParts(I->getOperand(0), ByteValues) ||
3622 CollectBSwapParts(I->getOperand(1), ByteValues);
3624 uint32_t BitWidth = I->getType()->getPrimitiveSizeInBits();
3625 // If this is a shift by a constant int, and it is "24", then its operand
3626 // defines a byte. We only handle unsigned types here.
3627 if (I->isShift() && isa<ConstantInt>(I->getOperand(1))) {
3628 // Not shifting the entire input by N-1 bytes?
3629 if (cast<ConstantInt>(I->getOperand(1))->getLimitedValue(BitWidth) !=
3630 8*(ByteValues.size()-1))
3634 if (I->getOpcode() == Instruction::Shl) {
3635 // X << 24 defines the top byte with the lowest of the input bytes.
3636 DestNo = ByteValues.size()-1;
3638 // X >>u 24 defines the low byte with the highest of the input bytes.
3642 // If the destination byte value is already defined, the values are or'd
3643 // together, which isn't a bswap (unless it's an or of the same bits).
3644 if (ByteValues[DestNo] && ByteValues[DestNo] != I->getOperand(0))
3646 ByteValues[DestNo] = I->getOperand(0);
3650 // Otherwise, we can only handle and(shift X, imm), imm). Bail out of if we
3652 Value *Shift = 0, *ShiftLHS = 0;
3653 ConstantInt *AndAmt = 0, *ShiftAmt = 0;
3654 if (!match(I, m_And(m_Value(Shift), m_ConstantInt(AndAmt))) ||
3655 !match(Shift, m_Shift(m_Value(ShiftLHS), m_ConstantInt(ShiftAmt))))
3657 Instruction *SI = cast<Instruction>(Shift);
3659 // Make sure that the shift amount is by a multiple of 8 and isn't too big.
3660 if (ShiftAmt->getLimitedValue(BitWidth) & 7 ||
3661 ShiftAmt->getLimitedValue(BitWidth) > 8*ByteValues.size())
3664 // Turn 0xFF -> 0, 0xFF00 -> 1, 0xFF0000 -> 2, etc.
3666 if (AndAmt->getValue().getActiveBits() > 64)
3668 uint64_t AndAmtVal = AndAmt->getZExtValue();
3669 for (DestByte = 0; DestByte != ByteValues.size(); ++DestByte)
3670 if (AndAmtVal == uint64_t(0xFF) << 8*DestByte)
3672 // Unknown mask for bswap.
3673 if (DestByte == ByteValues.size()) return true;
3675 unsigned ShiftBytes = ShiftAmt->getZExtValue()/8;
3677 if (SI->getOpcode() == Instruction::Shl)
3678 SrcByte = DestByte - ShiftBytes;
3680 SrcByte = DestByte + ShiftBytes;
3682 // If the SrcByte isn't a bswapped value from the DestByte, reject it.
3683 if (SrcByte != ByteValues.size()-DestByte-1)
3686 // If the destination byte value is already defined, the values are or'd
3687 // together, which isn't a bswap (unless it's an or of the same bits).
3688 if (ByteValues[DestByte] && ByteValues[DestByte] != SI->getOperand(0))
3690 ByteValues[DestByte] = SI->getOperand(0);
3694 /// MatchBSwap - Given an OR instruction, check to see if this is a bswap idiom.
3695 /// If so, insert the new bswap intrinsic and return it.
3696 Instruction *InstCombiner::MatchBSwap(BinaryOperator &I) {
3697 const IntegerType *ITy = dyn_cast<IntegerType>(I.getType());
3698 if (!ITy || ITy->getBitWidth() % 16)
3699 return 0; // Can only bswap pairs of bytes. Can't do vectors.
3701 /// ByteValues - For each byte of the result, we keep track of which value
3702 /// defines each byte.
3703 SmallVector<Value*, 8> ByteValues;
3704 ByteValues.resize(ITy->getBitWidth()/8);
3706 // Try to find all the pieces corresponding to the bswap.
3707 if (CollectBSwapParts(I.getOperand(0), ByteValues) ||
3708 CollectBSwapParts(I.getOperand(1), ByteValues))
3711 // Check to see if all of the bytes come from the same value.
3712 Value *V = ByteValues[0];
3713 if (V == 0) return 0; // Didn't find a byte? Must be zero.
3715 // Check to make sure that all of the bytes come from the same value.
3716 for (unsigned i = 1, e = ByteValues.size(); i != e; ++i)
3717 if (ByteValues[i] != V)
3719 const Type *Tys[] = { ITy };
3720 Module *M = I.getParent()->getParent()->getParent();
3721 Function *F = Intrinsic::getDeclaration(M, Intrinsic::bswap, Tys, 1);
3722 return new CallInst(F, V);
3726 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
3727 bool Changed = SimplifyCommutative(I);
3728 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3730 if (isa<UndefValue>(Op1)) // X | undef -> -1
3731 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
3735 return ReplaceInstUsesWith(I, Op0);
3737 // See if we can simplify any instructions used by the instruction whose sole
3738 // purpose is to compute bits we don't care about.
3739 if (!isa<VectorType>(I.getType())) {
3740 uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
3741 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
3742 if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
3743 KnownZero, KnownOne))
3745 } else if (isa<ConstantAggregateZero>(Op1)) {
3746 return ReplaceInstUsesWith(I, Op0); // X | <0,0> -> X
3747 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1)) {
3748 if (CP->isAllOnesValue()) // X | <-1,-1> -> <-1,-1>
3749 return ReplaceInstUsesWith(I, I.getOperand(1));
3755 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
3756 ConstantInt *C1 = 0; Value *X = 0;
3757 // (X & C1) | C2 --> (X | C2) & (C1|C2)
3758 if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
3759 Instruction *Or = BinaryOperator::createOr(X, RHS);
3760 InsertNewInstBefore(Or, I);
3762 return BinaryOperator::createAnd(Or,
3763 ConstantInt::get(RHS->getValue() | C1->getValue()));
3766 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
3767 if (match(Op0, m_Xor(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
3768 Instruction *Or = BinaryOperator::createOr(X, RHS);
3769 InsertNewInstBefore(Or, I);
3771 return BinaryOperator::createXor(Or,
3772 ConstantInt::get(C1->getValue() & ~RHS->getValue()));
3775 // Try to fold constant and into select arguments.
3776 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
3777 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
3779 if (isa<PHINode>(Op0))
3780 if (Instruction *NV = FoldOpIntoPhi(I))
3784 Value *A = 0, *B = 0;
3785 ConstantInt *C1 = 0, *C2 = 0;
3787 if (match(Op0, m_And(m_Value(A), m_Value(B))))
3788 if (A == Op1 || B == Op1) // (A & ?) | A --> A
3789 return ReplaceInstUsesWith(I, Op1);
3790 if (match(Op1, m_And(m_Value(A), m_Value(B))))
3791 if (A == Op0 || B == Op0) // A | (A & ?) --> A
3792 return ReplaceInstUsesWith(I, Op0);
3794 // (A | B) | C and A | (B | C) -> bswap if possible.
3795 // (A >> B) | (C << D) and (A << B) | (B >> C) -> bswap if possible.
3796 if (match(Op0, m_Or(m_Value(), m_Value())) ||
3797 match(Op1, m_Or(m_Value(), m_Value())) ||
3798 (match(Op0, m_Shift(m_Value(), m_Value())) &&
3799 match(Op1, m_Shift(m_Value(), m_Value())))) {
3800 if (Instruction *BSwap = MatchBSwap(I))
3804 // (X^C)|Y -> (X|Y)^C iff Y&C == 0
3805 if (Op0->hasOneUse() && match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
3806 MaskedValueIsZero(Op1, C1->getValue())) {
3807 Instruction *NOr = BinaryOperator::createOr(A, Op1);
3808 InsertNewInstBefore(NOr, I);
3810 return BinaryOperator::createXor(NOr, C1);
3813 // Y|(X^C) -> (X|Y)^C iff Y&C == 0
3814 if (Op1->hasOneUse() && match(Op1, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
3815 MaskedValueIsZero(Op0, C1->getValue())) {
3816 Instruction *NOr = BinaryOperator::createOr(A, Op0);
3817 InsertNewInstBefore(NOr, I);
3819 return BinaryOperator::createXor(NOr, C1);
3823 Value *C = 0, *D = 0;
3824 if (match(Op0, m_And(m_Value(A), m_Value(C))) &&
3825 match(Op1, m_And(m_Value(B), m_Value(D)))) {
3826 Value *V1 = 0, *V2 = 0, *V3 = 0;
3827 C1 = dyn_cast<ConstantInt>(C);
3828 C2 = dyn_cast<ConstantInt>(D);
3829 if (C1 && C2) { // (A & C1)|(B & C2)
3830 // If we have: ((V + N) & C1) | (V & C2)
3831 // .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0
3832 // replace with V+N.
3833 if (C1->getValue() == ~C2->getValue()) {
3834 if ((C2->getValue() & (C2->getValue()+1)) == 0 && // C2 == 0+1+
3835 match(A, m_Add(m_Value(V1), m_Value(V2)))) {
3836 // Add commutes, try both ways.
3837 if (V1 == B && MaskedValueIsZero(V2, C2->getValue()))
3838 return ReplaceInstUsesWith(I, A);
3839 if (V2 == B && MaskedValueIsZero(V1, C2->getValue()))
3840 return ReplaceInstUsesWith(I, A);
3842 // Or commutes, try both ways.
3843 if ((C1->getValue() & (C1->getValue()+1)) == 0 &&
3844 match(B, m_Add(m_Value(V1), m_Value(V2)))) {
3845 // Add commutes, try both ways.
3846 if (V1 == A && MaskedValueIsZero(V2, C1->getValue()))
3847 return ReplaceInstUsesWith(I, B);
3848 if (V2 == A && MaskedValueIsZero(V1, C1->getValue()))
3849 return ReplaceInstUsesWith(I, B);
3852 V1 = 0; V2 = 0; V3 = 0;
3855 // Check to see if we have any common things being and'ed. If so, find the
3856 // terms for V1 & (V2|V3).
3857 if (isOnlyUse(Op0) || isOnlyUse(Op1)) {
3858 if (A == B) // (A & C)|(A & D) == A & (C|D)
3859 V1 = A, V2 = C, V3 = D;
3860 else if (A == D) // (A & C)|(B & A) == A & (B|C)
3861 V1 = A, V2 = B, V3 = C;
3862 else if (C == B) // (A & C)|(C & D) == C & (A|D)
3863 V1 = C, V2 = A, V3 = D;
3864 else if (C == D) // (A & C)|(B & C) == C & (A|B)
3865 V1 = C, V2 = A, V3 = B;
3869 InsertNewInstBefore(BinaryOperator::createOr(V2, V3, "tmp"), I);
3870 return BinaryOperator::createAnd(V1, Or);
3875 // (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts.
3876 if (BinaryOperator *SI1 = dyn_cast<BinaryOperator>(Op1)) {
3877 if (BinaryOperator *SI0 = dyn_cast<BinaryOperator>(Op0))
3878 if (SI0->isShift() && SI0->getOpcode() == SI1->getOpcode() &&
3879 SI0->getOperand(1) == SI1->getOperand(1) &&
3880 (SI0->hasOneUse() || SI1->hasOneUse())) {
3881 Instruction *NewOp =
3882 InsertNewInstBefore(BinaryOperator::createOr(SI0->getOperand(0),
3884 SI0->getName()), I);
3885 return BinaryOperator::create(SI1->getOpcode(), NewOp,
3886 SI1->getOperand(1));
3890 if (match(Op0, m_Not(m_Value(A)))) { // ~A | Op1
3891 if (A == Op1) // ~A | A == -1
3892 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
3896 // Note, A is still live here!
3897 if (match(Op1, m_Not(m_Value(B)))) { // Op0 | ~B
3899 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
3901 // (~A | ~B) == (~(A & B)) - De Morgan's Law
3902 if (A && isOnlyUse(Op0) && isOnlyUse(Op1)) {
3903 Value *And = InsertNewInstBefore(BinaryOperator::createAnd(A, B,
3904 I.getName()+".demorgan"), I);
3905 return BinaryOperator::createNot(And);
3909 // (icmp1 A, B) | (icmp2 A, B) --> (icmp3 A, B)
3910 if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1))) {
3911 if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
3914 Value *LHSVal, *RHSVal;
3915 ConstantInt *LHSCst, *RHSCst;
3916 ICmpInst::Predicate LHSCC, RHSCC;
3917 if (match(Op0, m_ICmp(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
3918 if (match(RHS, m_ICmp(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
3919 if (LHSVal == RHSVal && // Found (X icmp C1) | (X icmp C2)
3920 // icmp [us][gl]e x, cst is folded to icmp [us][gl]t elsewhere.
3921 LHSCC != ICmpInst::ICMP_UGE && LHSCC != ICmpInst::ICMP_ULE &&
3922 RHSCC != ICmpInst::ICMP_UGE && RHSCC != ICmpInst::ICMP_ULE &&
3923 LHSCC != ICmpInst::ICMP_SGE && LHSCC != ICmpInst::ICMP_SLE &&
3924 RHSCC != ICmpInst::ICMP_SGE && RHSCC != ICmpInst::ICMP_SLE &&
3925 // We can't fold (ugt x, C) | (sgt x, C2).
3926 PredicatesFoldable(LHSCC, RHSCC)) {
3927 // Ensure that the larger constant is on the RHS.
3928 ICmpInst *LHS = cast<ICmpInst>(Op0);
3930 if (ICmpInst::isSignedPredicate(LHSCC))
3931 NeedsSwap = LHSCst->getValue().sgt(RHSCst->getValue());
3933 NeedsSwap = LHSCst->getValue().ugt(RHSCst->getValue());
3936 std::swap(LHS, RHS);
3937 std::swap(LHSCst, RHSCst);
3938 std::swap(LHSCC, RHSCC);
3941 // At this point, we know we have have two icmp instructions
3942 // comparing a value against two constants and or'ing the result
3943 // together. Because of the above check, we know that we only have
3944 // ICMP_EQ, ICMP_NE, ICMP_LT, and ICMP_GT here. We also know (from the
3945 // FoldICmpLogical check above), that the two constants are not
3947 assert(LHSCst != RHSCst && "Compares not folded above?");
3950 default: assert(0 && "Unknown integer condition code!");
3951 case ICmpInst::ICMP_EQ:
3953 default: assert(0 && "Unknown integer condition code!");
3954 case ICmpInst::ICMP_EQ:
3955 if (LHSCst == SubOne(RHSCst)) {// (X == 13 | X == 14) -> X-13 <u 2
3956 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
3957 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
3958 LHSVal->getName()+".off");
3959 InsertNewInstBefore(Add, I);
3960 AddCST = Subtract(AddOne(RHSCst), LHSCst);
3961 return new ICmpInst(ICmpInst::ICMP_ULT, Add, AddCST);
3963 break; // (X == 13 | X == 15) -> no change
3964 case ICmpInst::ICMP_UGT: // (X == 13 | X u> 14) -> no change
3965 case ICmpInst::ICMP_SGT: // (X == 13 | X s> 14) -> no change
3967 case ICmpInst::ICMP_NE: // (X == 13 | X != 15) -> X != 15
3968 case ICmpInst::ICMP_ULT: // (X == 13 | X u< 15) -> X u< 15
3969 case ICmpInst::ICMP_SLT: // (X == 13 | X s< 15) -> X s< 15
3970 return ReplaceInstUsesWith(I, RHS);
3973 case ICmpInst::ICMP_NE:
3975 default: assert(0 && "Unknown integer condition code!");
3976 case ICmpInst::ICMP_EQ: // (X != 13 | X == 15) -> X != 13
3977 case ICmpInst::ICMP_UGT: // (X != 13 | X u> 15) -> X != 13
3978 case ICmpInst::ICMP_SGT: // (X != 13 | X s> 15) -> X != 13
3979 return ReplaceInstUsesWith(I, LHS);
3980 case ICmpInst::ICMP_NE: // (X != 13 | X != 15) -> true
3981 case ICmpInst::ICMP_ULT: // (X != 13 | X u< 15) -> true
3982 case ICmpInst::ICMP_SLT: // (X != 13 | X s< 15) -> true
3983 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
3986 case ICmpInst::ICMP_ULT:
3988 default: assert(0 && "Unknown integer condition code!");
3989 case ICmpInst::ICMP_EQ: // (X u< 13 | X == 14) -> no change
3991 case ICmpInst::ICMP_UGT: // (X u< 13 | X u> 15) ->(X-13) u> 2
3992 return InsertRangeTest(LHSVal, LHSCst, AddOne(RHSCst), false,
3994 case ICmpInst::ICMP_SGT: // (X u< 13 | X s> 15) -> no change
3996 case ICmpInst::ICMP_NE: // (X u< 13 | X != 15) -> X != 15
3997 case ICmpInst::ICMP_ULT: // (X u< 13 | X u< 15) -> X u< 15
3998 return ReplaceInstUsesWith(I, RHS);
3999 case ICmpInst::ICMP_SLT: // (X u< 13 | X s< 15) -> no change
4003 case ICmpInst::ICMP_SLT:
4005 default: assert(0 && "Unknown integer condition code!");
4006 case ICmpInst::ICMP_EQ: // (X s< 13 | X == 14) -> no change
4008 case ICmpInst::ICMP_SGT: // (X s< 13 | X s> 15) ->(X-13) s> 2
4009 return InsertRangeTest(LHSVal, LHSCst, AddOne(RHSCst), true,
4011 case ICmpInst::ICMP_UGT: // (X s< 13 | X u> 15) -> no change
4013 case ICmpInst::ICMP_NE: // (X s< 13 | X != 15) -> X != 15
4014 case ICmpInst::ICMP_SLT: // (X s< 13 | X s< 15) -> X s< 15
4015 return ReplaceInstUsesWith(I, RHS);
4016 case ICmpInst::ICMP_ULT: // (X s< 13 | X u< 15) -> no change
4020 case ICmpInst::ICMP_UGT:
4022 default: assert(0 && "Unknown integer condition code!");
4023 case ICmpInst::ICMP_EQ: // (X u> 13 | X == 15) -> X u> 13
4024 case ICmpInst::ICMP_UGT: // (X u> 13 | X u> 15) -> X u> 13
4025 return ReplaceInstUsesWith(I, LHS);
4026 case ICmpInst::ICMP_SGT: // (X u> 13 | X s> 15) -> no change
4028 case ICmpInst::ICMP_NE: // (X u> 13 | X != 15) -> true
4029 case ICmpInst::ICMP_ULT: // (X u> 13 | X u< 15) -> true
4030 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4031 case ICmpInst::ICMP_SLT: // (X u> 13 | X s< 15) -> no change
4035 case ICmpInst::ICMP_SGT:
4037 default: assert(0 && "Unknown integer condition code!");
4038 case ICmpInst::ICMP_EQ: // (X s> 13 | X == 15) -> X > 13
4039 case ICmpInst::ICMP_SGT: // (X s> 13 | X s> 15) -> X > 13
4040 return ReplaceInstUsesWith(I, LHS);
4041 case ICmpInst::ICMP_UGT: // (X s> 13 | X u> 15) -> no change
4043 case ICmpInst::ICMP_NE: // (X s> 13 | X != 15) -> true
4044 case ICmpInst::ICMP_SLT: // (X s> 13 | X s< 15) -> true
4045 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4046 case ICmpInst::ICMP_ULT: // (X s> 13 | X u< 15) -> no change
4054 // fold (or (cast A), (cast B)) -> (cast (or A, B))
4055 if (CastInst *Op0C = dyn_cast<CastInst>(Op0))
4056 if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
4057 if (Op0C->getOpcode() == Op1C->getOpcode()) {// same cast kind ?
4058 const Type *SrcTy = Op0C->getOperand(0)->getType();
4059 if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
4060 // Only do this if the casts both really cause code to be generated.
4061 ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
4063 ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
4065 Instruction *NewOp = BinaryOperator::createOr(Op0C->getOperand(0),
4066 Op1C->getOperand(0),
4068 InsertNewInstBefore(NewOp, I);
4069 return CastInst::create(Op0C->getOpcode(), NewOp, I.getType());
4074 return Changed ? &I : 0;
4077 // XorSelf - Implements: X ^ X --> 0
4080 XorSelf(Value *rhs) : RHS(rhs) {}
4081 bool shouldApply(Value *LHS) const { return LHS == RHS; }
4082 Instruction *apply(BinaryOperator &Xor) const {
4088 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
4089 bool Changed = SimplifyCommutative(I);
4090 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4092 if (isa<UndefValue>(Op1))
4093 return ReplaceInstUsesWith(I, Op1); // X ^ undef -> undef
4095 // xor X, X = 0, even if X is nested in a sequence of Xor's.
4096 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
4097 assert(Result == &I && "AssociativeOpt didn't work?"); Result=Result;
4098 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
4101 // See if we can simplify any instructions used by the instruction whose sole
4102 // purpose is to compute bits we don't care about.
4103 if (!isa<VectorType>(I.getType())) {
4104 uint32_t BitWidth = cast<IntegerType>(I.getType())->getBitWidth();
4105 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4106 if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(BitWidth),
4107 KnownZero, KnownOne))
4109 } else if (isa<ConstantAggregateZero>(Op1)) {
4110 return ReplaceInstUsesWith(I, Op0); // X ^ <0,0> -> X
4113 // Is this a ~ operation?
4114 if (Value *NotOp = dyn_castNotVal(&I)) {
4115 // ~(~X & Y) --> (X | ~Y) - De Morgan's Law
4116 // ~(~X | Y) === (X & ~Y) - De Morgan's Law
4117 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(NotOp)) {
4118 if (Op0I->getOpcode() == Instruction::And ||
4119 Op0I->getOpcode() == Instruction::Or) {
4120 if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
4121 if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
4123 BinaryOperator::createNot(Op0I->getOperand(1),
4124 Op0I->getOperand(1)->getName()+".not");
4125 InsertNewInstBefore(NotY, I);
4126 if (Op0I->getOpcode() == Instruction::And)
4127 return BinaryOperator::createOr(Op0NotVal, NotY);
4129 return BinaryOperator::createAnd(Op0NotVal, NotY);
4136 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
4137 // xor (icmp A, B), true = not (icmp A, B) = !icmp A, B
4138 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Op0))
4139 if (RHS == ConstantInt::getTrue() && ICI->hasOneUse())
4140 return new ICmpInst(ICI->getInversePredicate(),
4141 ICI->getOperand(0), ICI->getOperand(1));
4143 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
4144 // ~(c-X) == X-c-1 == X+(-c-1)
4145 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
4146 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
4147 Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
4148 Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
4149 ConstantInt::get(I.getType(), 1));
4150 return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
4153 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
4154 if (Op0I->getOpcode() == Instruction::Add) {
4155 // ~(X-c) --> (-c-1)-X
4156 if (RHS->isAllOnesValue()) {
4157 Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
4158 return BinaryOperator::createSub(
4159 ConstantExpr::getSub(NegOp0CI,
4160 ConstantInt::get(I.getType(), 1)),
4161 Op0I->getOperand(0));
4162 } else if (RHS->getValue().isSignBit()) {
4163 // (X + C) ^ signbit -> (X + C + signbit)
4164 Constant *C = ConstantInt::get(RHS->getValue() + Op0CI->getValue());
4165 return BinaryOperator::createAdd(Op0I->getOperand(0), C);
4168 } else if (Op0I->getOpcode() == Instruction::Or) {
4169 // (X|C1)^C2 -> X^(C1|C2) iff X&~C1 == 0
4170 if (MaskedValueIsZero(Op0I->getOperand(0), Op0CI->getValue())) {
4171 Constant *NewRHS = ConstantExpr::getOr(Op0CI, RHS);
4172 // Anything in both C1 and C2 is known to be zero, remove it from
4174 Constant *CommonBits = And(Op0CI, RHS);
4175 NewRHS = ConstantExpr::getAnd(NewRHS,
4176 ConstantExpr::getNot(CommonBits));
4177 AddToWorkList(Op0I);
4178 I.setOperand(0, Op0I->getOperand(0));
4179 I.setOperand(1, NewRHS);
4185 // Try to fold constant and into select arguments.
4186 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
4187 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
4189 if (isa<PHINode>(Op0))
4190 if (Instruction *NV = FoldOpIntoPhi(I))
4194 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
4196 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
4198 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
4200 return ReplaceInstUsesWith(I, Constant::getAllOnesValue(I.getType()));
4203 BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1);
4206 if (match(Op1I, m_Or(m_Value(A), m_Value(B)))) {
4207 if (A == Op0) { // B^(B|A) == (A|B)^B
4208 Op1I->swapOperands();
4210 std::swap(Op0, Op1);
4211 } else if (B == Op0) { // B^(A|B) == (A|B)^B
4212 I.swapOperands(); // Simplified below.
4213 std::swap(Op0, Op1);
4215 } else if (match(Op1I, m_Xor(m_Value(A), m_Value(B)))) {
4216 if (Op0 == A) // A^(A^B) == B
4217 return ReplaceInstUsesWith(I, B);
4218 else if (Op0 == B) // A^(B^A) == B
4219 return ReplaceInstUsesWith(I, A);
4220 } else if (match(Op1I, m_And(m_Value(A), m_Value(B))) && Op1I->hasOneUse()){
4221 if (A == Op0) { // A^(A&B) -> A^(B&A)
4222 Op1I->swapOperands();
4225 if (B == Op0) { // A^(B&A) -> (B&A)^A
4226 I.swapOperands(); // Simplified below.
4227 std::swap(Op0, Op1);
4232 BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0);
4235 if (match(Op0I, m_Or(m_Value(A), m_Value(B))) && Op0I->hasOneUse()) {
4236 if (A == Op1) // (B|A)^B == (A|B)^B
4238 if (B == Op1) { // (A|B)^B == A & ~B
4240 InsertNewInstBefore(BinaryOperator::createNot(Op1, "tmp"), I);
4241 return BinaryOperator::createAnd(A, NotB);
4243 } else if (match(Op0I, m_Xor(m_Value(A), m_Value(B)))) {
4244 if (Op1 == A) // (A^B)^A == B
4245 return ReplaceInstUsesWith(I, B);
4246 else if (Op1 == B) // (B^A)^A == B
4247 return ReplaceInstUsesWith(I, A);
4248 } else if (match(Op0I, m_And(m_Value(A), m_Value(B))) && Op0I->hasOneUse()){
4249 if (A == Op1) // (A&B)^A -> (B&A)^A
4251 if (B == Op1 && // (B&A)^A == ~B & A
4252 !isa<ConstantInt>(Op1)) { // Canonical form is (B&C)^C
4254 InsertNewInstBefore(BinaryOperator::createNot(A, "tmp"), I);
4255 return BinaryOperator::createAnd(N, Op1);
4260 // (X >> Z) ^ (Y >> Z) -> (X^Y) >> Z for all shifts.
4261 if (Op0I && Op1I && Op0I->isShift() &&
4262 Op0I->getOpcode() == Op1I->getOpcode() &&
4263 Op0I->getOperand(1) == Op1I->getOperand(1) &&
4264 (Op1I->hasOneUse() || Op1I->hasOneUse())) {
4265 Instruction *NewOp =
4266 InsertNewInstBefore(BinaryOperator::createXor(Op0I->getOperand(0),
4267 Op1I->getOperand(0),
4268 Op0I->getName()), I);
4269 return BinaryOperator::create(Op1I->getOpcode(), NewOp,
4270 Op1I->getOperand(1));
4274 Value *A, *B, *C, *D;
4275 // (A & B)^(A | B) -> A ^ B
4276 if (match(Op0I, m_And(m_Value(A), m_Value(B))) &&
4277 match(Op1I, m_Or(m_Value(C), m_Value(D)))) {
4278 if ((A == C && B == D) || (A == D && B == C))
4279 return BinaryOperator::createXor(A, B);
4281 // (A | B)^(A & B) -> A ^ B
4282 if (match(Op0I, m_Or(m_Value(A), m_Value(B))) &&
4283 match(Op1I, m_And(m_Value(C), m_Value(D)))) {
4284 if ((A == C && B == D) || (A == D && B == C))
4285 return BinaryOperator::createXor(A, B);
4289 if ((Op0I->hasOneUse() || Op1I->hasOneUse()) &&
4290 match(Op0I, m_And(m_Value(A), m_Value(B))) &&
4291 match(Op1I, m_And(m_Value(C), m_Value(D)))) {
4292 // (X & Y)^(X & Y) -> (Y^Z) & X
4293 Value *X = 0, *Y = 0, *Z = 0;
4295 X = A, Y = B, Z = D;
4297 X = A, Y = B, Z = C;
4299 X = B, Y = A, Z = D;
4301 X = B, Y = A, Z = C;
4304 Instruction *NewOp =
4305 InsertNewInstBefore(BinaryOperator::createXor(Y, Z, Op0->getName()), I);
4306 return BinaryOperator::createAnd(NewOp, X);
4311 // (icmp1 A, B) ^ (icmp2 A, B) --> (icmp3 A, B)
4312 if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
4313 if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
4316 // fold (xor (cast A), (cast B)) -> (cast (xor A, B))
4317 if (CastInst *Op0C = dyn_cast<CastInst>(Op0))
4318 if (CastInst *Op1C = dyn_cast<CastInst>(Op1))
4319 if (Op0C->getOpcode() == Op1C->getOpcode()) { // same cast kind?
4320 const Type *SrcTy = Op0C->getOperand(0)->getType();
4321 if (SrcTy == Op1C->getOperand(0)->getType() && SrcTy->isInteger() &&
4322 // Only do this if the casts both really cause code to be generated.
4323 ValueRequiresCast(Op0C->getOpcode(), Op0C->getOperand(0),
4325 ValueRequiresCast(Op1C->getOpcode(), Op1C->getOperand(0),
4327 Instruction *NewOp = BinaryOperator::createXor(Op0C->getOperand(0),
4328 Op1C->getOperand(0),
4330 InsertNewInstBefore(NewOp, I);
4331 return CastInst::create(Op0C->getOpcode(), NewOp, I.getType());
4335 return Changed ? &I : 0;
4338 /// AddWithOverflow - Compute Result = In1+In2, returning true if the result
4339 /// overflowed for this type.
4340 static bool AddWithOverflow(ConstantInt *&Result, ConstantInt *In1,
4341 ConstantInt *In2, bool IsSigned = false) {
4342 Result = cast<ConstantInt>(Add(In1, In2));
4345 if (In2->getValue().isNegative())
4346 return Result->getValue().sgt(In1->getValue());
4348 return Result->getValue().slt(In1->getValue());
4350 return Result->getValue().ult(In1->getValue());
4353 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
4354 /// code necessary to compute the offset from the base pointer (without adding
4355 /// in the base pointer). Return the result as a signed integer of intptr size.
4356 static Value *EmitGEPOffset(User *GEP, Instruction &I, InstCombiner &IC) {
4357 TargetData &TD = IC.getTargetData();
4358 gep_type_iterator GTI = gep_type_begin(GEP);
4359 const Type *IntPtrTy = TD.getIntPtrType();
4360 Value *Result = Constant::getNullValue(IntPtrTy);
4362 // Build a mask for high order bits.
4363 unsigned IntPtrWidth = TD.getPointerSize()*8;
4364 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
4366 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
4367 Value *Op = GEP->getOperand(i);
4368 uint64_t Size = TD.getTypeSize(GTI.getIndexedType()) & PtrSizeMask;
4369 if (ConstantInt *OpC = dyn_cast<ConstantInt>(Op)) {
4370 if (OpC->isZero()) continue;
4372 // Handle a struct index, which adds its field offset to the pointer.
4373 if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
4374 Size = TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
4376 if (ConstantInt *RC = dyn_cast<ConstantInt>(Result))
4377 Result = ConstantInt::get(RC->getValue() + APInt(IntPtrWidth, Size));
4379 Result = IC.InsertNewInstBefore(
4380 BinaryOperator::createAdd(Result,
4381 ConstantInt::get(IntPtrTy, Size),
4382 GEP->getName()+".offs"), I);
4386 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
4387 Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
4388 Scale = ConstantExpr::getMul(OC, Scale);
4389 if (Constant *RC = dyn_cast<Constant>(Result))
4390 Result = ConstantExpr::getAdd(RC, Scale);
4392 // Emit an add instruction.
4393 Result = IC.InsertNewInstBefore(
4394 BinaryOperator::createAdd(Result, Scale,
4395 GEP->getName()+".offs"), I);
4399 // Convert to correct type.
4400 if (Op->getType() != IntPtrTy) {
4401 if (Constant *OpC = dyn_cast<Constant>(Op))
4402 Op = ConstantExpr::getSExt(OpC, IntPtrTy);
4404 Op = IC.InsertNewInstBefore(new SExtInst(Op, IntPtrTy,
4405 Op->getName()+".c"), I);
4408 Constant *Scale = ConstantInt::get(IntPtrTy, Size);
4409 if (Constant *OpC = dyn_cast<Constant>(Op))
4410 Op = ConstantExpr::getMul(OpC, Scale);
4411 else // We'll let instcombine(mul) convert this to a shl if possible.
4412 Op = IC.InsertNewInstBefore(BinaryOperator::createMul(Op, Scale,
4413 GEP->getName()+".idx"), I);
4416 // Emit an add instruction.
4417 if (isa<Constant>(Op) && isa<Constant>(Result))
4418 Result = ConstantExpr::getAdd(cast<Constant>(Op),
4419 cast<Constant>(Result));
4421 Result = IC.InsertNewInstBefore(BinaryOperator::createAdd(Op, Result,
4422 GEP->getName()+".offs"), I);
4427 /// FoldGEPICmp - Fold comparisons between a GEP instruction and something
4428 /// else. At this point we know that the GEP is on the LHS of the comparison.
4429 Instruction *InstCombiner::FoldGEPICmp(User *GEPLHS, Value *RHS,
4430 ICmpInst::Predicate Cond,
4432 assert(dyn_castGetElementPtr(GEPLHS) && "LHS is not a getelementptr!");
4434 if (CastInst *CI = dyn_cast<CastInst>(RHS))
4435 if (isa<PointerType>(CI->getOperand(0)->getType()))
4436 RHS = CI->getOperand(0);
4438 Value *PtrBase = GEPLHS->getOperand(0);
4439 if (PtrBase == RHS) {
4440 // As an optimization, we don't actually have to compute the actual value of
4441 // OFFSET if this is a icmp_eq or icmp_ne comparison, just return whether
4442 // each index is zero or not.
4443 if (Cond == ICmpInst::ICMP_EQ || Cond == ICmpInst::ICMP_NE) {
4444 Instruction *InVal = 0;
4445 gep_type_iterator GTI = gep_type_begin(GEPLHS);
4446 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i, ++GTI) {
4448 if (Constant *C = dyn_cast<Constant>(GEPLHS->getOperand(i))) {
4449 if (isa<UndefValue>(C)) // undef index -> undef.
4450 return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
4451 if (C->isNullValue())
4453 else if (TD->getTypeSize(GTI.getIndexedType()) == 0) {
4454 EmitIt = false; // This is indexing into a zero sized array?
4455 } else if (isa<ConstantInt>(C))
4456 return ReplaceInstUsesWith(I, // No comparison is needed here.
4457 ConstantInt::get(Type::Int1Ty,
4458 Cond == ICmpInst::ICMP_NE));
4463 new ICmpInst(Cond, GEPLHS->getOperand(i),
4464 Constant::getNullValue(GEPLHS->getOperand(i)->getType()));
4468 InVal = InsertNewInstBefore(InVal, I);
4469 InsertNewInstBefore(Comp, I);
4470 if (Cond == ICmpInst::ICMP_NE) // True if any are unequal
4471 InVal = BinaryOperator::createOr(InVal, Comp);
4472 else // True if all are equal
4473 InVal = BinaryOperator::createAnd(InVal, Comp);
4481 // No comparison is needed here, all indexes = 0
4482 ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty,
4483 Cond == ICmpInst::ICMP_EQ));
4486 // Only lower this if the icmp is the only user of the GEP or if we expect
4487 // the result to fold to a constant!
4488 if (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) {
4489 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
4490 Value *Offset = EmitGEPOffset(GEPLHS, I, *this);
4491 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
4492 Constant::getNullValue(Offset->getType()));
4494 } else if (User *GEPRHS = dyn_castGetElementPtr(RHS)) {
4495 // If the base pointers are different, but the indices are the same, just
4496 // compare the base pointer.
4497 if (PtrBase != GEPRHS->getOperand(0)) {
4498 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
4499 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
4500 GEPRHS->getOperand(0)->getType();
4502 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
4503 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
4504 IndicesTheSame = false;
4508 // If all indices are the same, just compare the base pointers.
4510 return new ICmpInst(ICmpInst::getSignedPredicate(Cond),
4511 GEPLHS->getOperand(0), GEPRHS->getOperand(0));
4513 // Otherwise, the base pointers are different and the indices are
4514 // different, bail out.
4518 // If one of the GEPs has all zero indices, recurse.
4519 bool AllZeros = true;
4520 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
4521 if (!isa<Constant>(GEPLHS->getOperand(i)) ||
4522 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
4527 return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
4528 ICmpInst::getSwappedPredicate(Cond), I);
4530 // If the other GEP has all zero indices, recurse.
4532 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
4533 if (!isa<Constant>(GEPRHS->getOperand(i)) ||
4534 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
4539 return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
4541 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
4542 // If the GEPs only differ by one index, compare it.
4543 unsigned NumDifferences = 0; // Keep track of # differences.
4544 unsigned DiffOperand = 0; // The operand that differs.
4545 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
4546 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
4547 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
4548 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
4549 // Irreconcilable differences.
4553 if (NumDifferences++) break;
4558 if (NumDifferences == 0) // SAME GEP?
4559 return ReplaceInstUsesWith(I, // No comparison is needed here.
4560 ConstantInt::get(Type::Int1Ty,
4561 Cond == ICmpInst::ICMP_EQ));
4562 else if (NumDifferences == 1) {
4563 Value *LHSV = GEPLHS->getOperand(DiffOperand);
4564 Value *RHSV = GEPRHS->getOperand(DiffOperand);
4565 // Make sure we do a signed comparison here.
4566 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
4570 // Only lower this if the icmp is the only user of the GEP or if we expect
4571 // the result to fold to a constant!
4572 if ((isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
4573 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
4574 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
4575 Value *L = EmitGEPOffset(GEPLHS, I, *this);
4576 Value *R = EmitGEPOffset(GEPRHS, I, *this);
4577 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
4583 Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
4584 bool Changed = SimplifyCompare(I);
4585 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4587 // Fold trivial predicates.
4588 if (I.getPredicate() == FCmpInst::FCMP_FALSE)
4589 return ReplaceInstUsesWith(I, Constant::getNullValue(Type::Int1Ty));
4590 if (I.getPredicate() == FCmpInst::FCMP_TRUE)
4591 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty, 1));
4593 // Simplify 'fcmp pred X, X'
4595 switch (I.getPredicate()) {
4596 default: assert(0 && "Unknown predicate!");
4597 case FCmpInst::FCMP_UEQ: // True if unordered or equal
4598 case FCmpInst::FCMP_UGE: // True if unordered, greater than, or equal
4599 case FCmpInst::FCMP_ULE: // True if unordered, less than, or equal
4600 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty, 1));
4601 case FCmpInst::FCMP_OGT: // True if ordered and greater than
4602 case FCmpInst::FCMP_OLT: // True if ordered and less than
4603 case FCmpInst::FCMP_ONE: // True if ordered and operands are unequal
4604 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty, 0));
4606 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4607 case FCmpInst::FCMP_ULT: // True if unordered or less than
4608 case FCmpInst::FCMP_UGT: // True if unordered or greater than
4609 case FCmpInst::FCMP_UNE: // True if unordered or not equal
4610 // Canonicalize these to be 'fcmp uno %X, 0.0'.
4611 I.setPredicate(FCmpInst::FCMP_UNO);
4612 I.setOperand(1, Constant::getNullValue(Op0->getType()));
4615 case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4616 case FCmpInst::FCMP_OEQ: // True if ordered and equal
4617 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4618 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4619 // Canonicalize these to be 'fcmp ord %X, 0.0'.
4620 I.setPredicate(FCmpInst::FCMP_ORD);
4621 I.setOperand(1, Constant::getNullValue(Op0->getType()));
4626 if (isa<UndefValue>(Op1)) // fcmp pred X, undef -> undef
4627 return ReplaceInstUsesWith(I, UndefValue::get(Type::Int1Ty));
4629 // Handle fcmp with constant RHS
4630 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4631 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4632 switch (LHSI->getOpcode()) {
4633 case Instruction::PHI:
4634 if (Instruction *NV = FoldOpIntoPhi(I))
4637 case Instruction::Select:
4638 // If either operand of the select is a constant, we can fold the
4639 // comparison into the select arms, which will cause one to be
4640 // constant folded and the select turned into a bitwise or.
4641 Value *Op1 = 0, *Op2 = 0;
4642 if (LHSI->hasOneUse()) {
4643 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
4644 // Fold the known value into the constant operand.
4645 Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
4646 // Insert a new FCmp of the other select operand.
4647 Op2 = InsertNewInstBefore(new FCmpInst(I.getPredicate(),
4648 LHSI->getOperand(2), RHSC,
4650 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
4651 // Fold the known value into the constant operand.
4652 Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
4653 // Insert a new FCmp of the other select operand.
4654 Op1 = InsertNewInstBefore(new FCmpInst(I.getPredicate(),
4655 LHSI->getOperand(1), RHSC,
4661 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
4666 return Changed ? &I : 0;
4669 Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
4670 bool Changed = SimplifyCompare(I);
4671 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4672 const Type *Ty = Op0->getType();
4676 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty,
4677 isTrueWhenEqual(I)));
4679 if (isa<UndefValue>(Op1)) // X icmp undef -> undef
4680 return ReplaceInstUsesWith(I, UndefValue::get(Type::Int1Ty));
4682 // icmp of GlobalValues can never equal each other as long as they aren't
4683 // external weak linkage type.
4684 if (GlobalValue *GV0 = dyn_cast<GlobalValue>(Op0))
4685 if (GlobalValue *GV1 = dyn_cast<GlobalValue>(Op1))
4686 if (!GV0->hasExternalWeakLinkage() || !GV1->hasExternalWeakLinkage())
4687 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty,
4688 !isTrueWhenEqual(I)));
4690 // icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
4691 // addresses never equal each other! We already know that Op0 != Op1.
4692 if ((isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0) ||
4693 isa<ConstantPointerNull>(Op0)) &&
4694 (isa<GlobalValue>(Op1) || isa<AllocaInst>(Op1) ||
4695 isa<ConstantPointerNull>(Op1)))
4696 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty,
4697 !isTrueWhenEqual(I)));
4699 // icmp's with boolean values can always be turned into bitwise operations
4700 if (Ty == Type::Int1Ty) {
4701 switch (I.getPredicate()) {
4702 default: assert(0 && "Invalid icmp instruction!");
4703 case ICmpInst::ICMP_EQ: { // icmp eq bool %A, %B -> ~(A^B)
4704 Instruction *Xor = BinaryOperator::createXor(Op0, Op1, I.getName()+"tmp");
4705 InsertNewInstBefore(Xor, I);
4706 return BinaryOperator::createNot(Xor);
4708 case ICmpInst::ICMP_NE: // icmp eq bool %A, %B -> A^B
4709 return BinaryOperator::createXor(Op0, Op1);
4711 case ICmpInst::ICMP_UGT:
4712 case ICmpInst::ICMP_SGT:
4713 std::swap(Op0, Op1); // Change icmp gt -> icmp lt
4715 case ICmpInst::ICMP_ULT:
4716 case ICmpInst::ICMP_SLT: { // icmp lt bool A, B -> ~X & Y
4717 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
4718 InsertNewInstBefore(Not, I);
4719 return BinaryOperator::createAnd(Not, Op1);
4721 case ICmpInst::ICMP_UGE:
4722 case ICmpInst::ICMP_SGE:
4723 std::swap(Op0, Op1); // Change icmp ge -> icmp le
4725 case ICmpInst::ICMP_ULE:
4726 case ICmpInst::ICMP_SLE: { // icmp le bool %A, %B -> ~A | B
4727 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
4728 InsertNewInstBefore(Not, I);
4729 return BinaryOperator::createOr(Not, Op1);
4734 // See if we are doing a comparison between a constant and an instruction that
4735 // can be folded into the comparison.
4736 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
4737 switch (I.getPredicate()) {
4739 case ICmpInst::ICMP_ULT: // A <u MIN -> FALSE
4740 if (CI->isMinValue(false))
4741 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4742 if (CI->isMaxValue(false)) // A <u MAX -> A != MAX
4743 return new ICmpInst(ICmpInst::ICMP_NE, Op0,Op1);
4744 if (isMinValuePlusOne(CI,false)) // A <u MIN+1 -> A == MIN
4745 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
4746 // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
4747 if (CI->isMinValue(true))
4748 return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
4749 ConstantInt::getAllOnesValue(Op0->getType()));
4753 case ICmpInst::ICMP_SLT:
4754 if (CI->isMinValue(true)) // A <s MIN -> FALSE
4755 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4756 if (CI->isMaxValue(true)) // A <s MAX -> A != MAX
4757 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4758 if (isMinValuePlusOne(CI,true)) // A <s MIN+1 -> A == MIN
4759 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, SubOne(CI));
4762 case ICmpInst::ICMP_UGT:
4763 if (CI->isMaxValue(false)) // A >u MAX -> FALSE
4764 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4765 if (CI->isMinValue(false)) // A >u MIN -> A != MIN
4766 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4767 if (isMaxValueMinusOne(CI, false)) // A >u MAX-1 -> A == MAX
4768 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
4770 // (x >u 2147483647) -> (x <s 0) -> true if sign bit set
4771 if (CI->isMaxValue(true))
4772 return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
4773 ConstantInt::getNullValue(Op0->getType()));
4776 case ICmpInst::ICMP_SGT:
4777 if (CI->isMaxValue(true)) // A >s MAX -> FALSE
4778 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4779 if (CI->isMinValue(true)) // A >s MIN -> A != MIN
4780 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4781 if (isMaxValueMinusOne(CI, true)) // A >s MAX-1 -> A == MAX
4782 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, AddOne(CI));
4785 case ICmpInst::ICMP_ULE:
4786 if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
4787 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4788 if (CI->isMinValue(false)) // A <=u MIN -> A == MIN
4789 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4790 if (isMaxValueMinusOne(CI,false)) // A <=u MAX-1 -> A != MAX
4791 return new ICmpInst(ICmpInst::ICMP_NE, Op0, AddOne(CI));
4794 case ICmpInst::ICMP_SLE:
4795 if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
4796 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4797 if (CI->isMinValue(true)) // A <=s MIN -> A == MIN
4798 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4799 if (isMaxValueMinusOne(CI,true)) // A <=s MAX-1 -> A != MAX
4800 return new ICmpInst(ICmpInst::ICMP_NE, Op0, AddOne(CI));
4803 case ICmpInst::ICMP_UGE:
4804 if (CI->isMinValue(false)) // A >=u MIN -> TRUE
4805 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4806 if (CI->isMaxValue(false)) // A >=u MAX -> A == MAX
4807 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4808 if (isMinValuePlusOne(CI,false)) // A >=u MIN-1 -> A != MIN
4809 return new ICmpInst(ICmpInst::ICMP_NE, Op0, SubOne(CI));
4812 case ICmpInst::ICMP_SGE:
4813 if (CI->isMinValue(true)) // A >=s MIN -> TRUE
4814 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4815 if (CI->isMaxValue(true)) // A >=s MAX -> A == MAX
4816 return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4817 if (isMinValuePlusOne(CI,true)) // A >=s MIN-1 -> A != MIN
4818 return new ICmpInst(ICmpInst::ICMP_NE, Op0, SubOne(CI));
4822 // If we still have a icmp le or icmp ge instruction, turn it into the
4823 // appropriate icmp lt or icmp gt instruction. Since the border cases have
4824 // already been handled above, this requires little checking.
4826 switch (I.getPredicate()) {
4828 case ICmpInst::ICMP_ULE:
4829 return new ICmpInst(ICmpInst::ICMP_ULT, Op0, AddOne(CI));
4830 case ICmpInst::ICMP_SLE:
4831 return new ICmpInst(ICmpInst::ICMP_SLT, Op0, AddOne(CI));
4832 case ICmpInst::ICMP_UGE:
4833 return new ICmpInst( ICmpInst::ICMP_UGT, Op0, SubOne(CI));
4834 case ICmpInst::ICMP_SGE:
4835 return new ICmpInst(ICmpInst::ICMP_SGT, Op0, SubOne(CI));
4838 // See if we can fold the comparison based on bits known to be zero or one
4839 // in the input. If this comparison is a normal comparison, it demands all
4840 // bits, if it is a sign bit comparison, it only demands the sign bit.
4843 bool isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
4845 uint32_t BitWidth = cast<IntegerType>(Ty)->getBitWidth();
4846 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
4847 if (SimplifyDemandedBits(Op0,
4848 isSignBit ? APInt::getSignBit(BitWidth)
4849 : APInt::getAllOnesValue(BitWidth),
4850 KnownZero, KnownOne, 0))
4853 // Given the known and unknown bits, compute a range that the LHS could be
4855 if ((KnownOne | KnownZero) != 0) {
4856 // Compute the Min, Max and RHS values based on the known bits. For the
4857 // EQ and NE we use unsigned values.
4858 APInt Min(BitWidth, 0), Max(BitWidth, 0);
4859 const APInt& RHSVal = CI->getValue();
4860 if (ICmpInst::isSignedPredicate(I.getPredicate())) {
4861 ComputeSignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne, Min,
4864 ComputeUnsignedMinMaxValuesFromKnownBits(Ty, KnownZero, KnownOne, Min,
4867 switch (I.getPredicate()) { // LE/GE have been folded already.
4868 default: assert(0 && "Unknown icmp opcode!");
4869 case ICmpInst::ICMP_EQ:
4870 if (Max.ult(RHSVal) || Min.ugt(RHSVal))
4871 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4873 case ICmpInst::ICMP_NE:
4874 if (Max.ult(RHSVal) || Min.ugt(RHSVal))
4875 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4877 case ICmpInst::ICMP_ULT:
4878 if (Max.ult(RHSVal))
4879 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4880 if (Min.uge(RHSVal))
4881 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4883 case ICmpInst::ICMP_UGT:
4884 if (Min.ugt(RHSVal))
4885 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4886 if (Max.ule(RHSVal))
4887 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4889 case ICmpInst::ICMP_SLT:
4890 if (Max.slt(RHSVal))
4891 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4892 if (Min.sgt(RHSVal))
4893 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4895 case ICmpInst::ICMP_SGT:
4896 if (Min.sgt(RHSVal))
4897 return ReplaceInstUsesWith(I, ConstantInt::getTrue());
4898 if (Max.sle(RHSVal))
4899 return ReplaceInstUsesWith(I, ConstantInt::getFalse());
4904 // Since the RHS is a ConstantInt (CI), if the left hand side is an
4905 // instruction, see if that instruction also has constants so that the
4906 // instruction can be folded into the icmp
4907 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4908 if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI))
4912 // Handle icmp with constant (but not simple integer constant) RHS
4913 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4914 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4915 switch (LHSI->getOpcode()) {
4916 case Instruction::GetElementPtr:
4917 if (RHSC->isNullValue()) {
4918 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
4919 bool isAllZeros = true;
4920 for (unsigned i = 1, e = LHSI->getNumOperands(); i != e; ++i)
4921 if (!isa<Constant>(LHSI->getOperand(i)) ||
4922 !cast<Constant>(LHSI->getOperand(i))->isNullValue()) {
4927 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
4928 Constant::getNullValue(LHSI->getOperand(0)->getType()));
4932 case Instruction::PHI:
4933 if (Instruction *NV = FoldOpIntoPhi(I))
4936 case Instruction::Select: {
4937 // If either operand of the select is a constant, we can fold the
4938 // comparison into the select arms, which will cause one to be
4939 // constant folded and the select turned into a bitwise or.
4940 Value *Op1 = 0, *Op2 = 0;
4941 if (LHSI->hasOneUse()) {
4942 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
4943 // Fold the known value into the constant operand.
4944 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
4945 // Insert a new ICmp of the other select operand.
4946 Op2 = InsertNewInstBefore(new ICmpInst(I.getPredicate(),
4947 LHSI->getOperand(2), RHSC,
4949 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
4950 // Fold the known value into the constant operand.
4951 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
4952 // Insert a new ICmp of the other select operand.
4953 Op1 = InsertNewInstBefore(new ICmpInst(I.getPredicate(),
4954 LHSI->getOperand(1), RHSC,
4960 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
4963 case Instruction::Malloc:
4964 // If we have (malloc != null), and if the malloc has a single use, we
4965 // can assume it is successful and remove the malloc.
4966 if (LHSI->hasOneUse() && isa<ConstantPointerNull>(RHSC)) {
4967 AddToWorkList(LHSI);
4968 return ReplaceInstUsesWith(I, ConstantInt::get(Type::Int1Ty,
4969 !isTrueWhenEqual(I)));
4975 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4976 if (User *GEP = dyn_castGetElementPtr(Op0))
4977 if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I))
4979 if (User *GEP = dyn_castGetElementPtr(Op1))
4980 if (Instruction *NI = FoldGEPICmp(GEP, Op0,
4981 ICmpInst::getSwappedPredicate(I.getPredicate()), I))
4984 // Test to see if the operands of the icmp are casted versions of other
4985 // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4987 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4988 if (isa<PointerType>(Op0->getType()) &&
4989 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4990 // We keep moving the cast from the left operand over to the right
4991 // operand, where it can often be eliminated completely.
4992 Op0 = CI->getOperand(0);
4994 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4995 // so eliminate it as well.
4996 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4997 Op1 = CI2->getOperand(0);
4999 // If Op1 is a constant, we can fold the cast into the constant.
5000 if (Op0->getType() != Op1->getType())
5001 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
5002 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
5004 // Otherwise, cast the RHS right before the icmp
5005 Op1 = InsertCastBefore(Instruction::BitCast, Op1, Op0->getType(), I);
5007 return new ICmpInst(I.getPredicate(), Op0, Op1);
5011 if (isa<CastInst>(Op0)) {
5012 // Handle the special case of: icmp (cast bool to X), <cst>
5013 // This comes up when you have code like
5016 // For generality, we handle any zero-extension of any operand comparison
5017 // with a constant or another cast from the same type.
5018 if (isa<ConstantInt>(Op1) || isa<CastInst>(Op1))
5019 if (Instruction *R = visitICmpInstWithCastAndCast(I))
5023 if (I.isEquality()) {
5024 Value *A, *B, *C, *D;
5025 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
5026 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
5027 Value *OtherVal = A == Op1 ? B : A;
5028 return new ICmpInst(I.getPredicate(), OtherVal,
5029 Constant::getNullValue(A->getType()));
5032 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
5033 // A^c1 == C^c2 --> A == C^(c1^c2)
5034 if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
5035 if (ConstantInt *C2 = dyn_cast<ConstantInt>(D))
5036 if (Op1->hasOneUse()) {
5037 Constant *NC = ConstantInt::get(C1->getValue() ^ C2->getValue());
5038 Instruction *Xor = BinaryOperator::createXor(C, NC, "tmp");
5039 return new ICmpInst(I.getPredicate(), A,
5040 InsertNewInstBefore(Xor, I));
5043 // A^B == A^D -> B == D
5044 if (A == C) return new ICmpInst(I.getPredicate(), B, D);
5045 if (A == D) return new ICmpInst(I.getPredicate(), B, C);
5046 if (B == C) return new ICmpInst(I.getPredicate(), A, D);
5047 if (B == D) return new ICmpInst(I.getPredicate(), A, C);
5051 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
5052 (A == Op0 || B == Op0)) {
5053 // A == (A^B) -> B == 0
5054 Value *OtherVal = A == Op0 ? B : A;
5055 return new ICmpInst(I.getPredicate(), OtherVal,
5056 Constant::getNullValue(A->getType()));
5058 if (match(Op0, m_Sub(m_Value(A), m_Value(B))) && A == Op1) {
5059 // (A-B) == A -> B == 0
5060 return new ICmpInst(I.getPredicate(), B,
5061 Constant::getNullValue(B->getType()));
5063 if (match(Op1, m_Sub(m_Value(A), m_Value(B))) && A == Op0) {
5064 // A == (A-B) -> B == 0
5065 return new ICmpInst(I.getPredicate(), B,
5066 Constant::getNullValue(B->getType()));
5069 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
5070 if (Op0->hasOneUse() && Op1->hasOneUse() &&
5071 match(Op0, m_And(m_Value(A), m_Value(B))) &&
5072 match(Op1, m_And(m_Value(C), m_Value(D)))) {
5073 Value *X = 0, *Y = 0, *Z = 0;
5076 X = B; Y = D; Z = A;
5077 } else if (A == D) {
5078 X = B; Y = C; Z = A;
5079 } else if (B == C) {
5080 X = A; Y = D; Z = B;
5081 } else if (B == D) {
5082 X = A; Y = C; Z = B;
5085 if (X) { // Build (X^Y) & Z
5086 Op1 = InsertNewInstBefore(BinaryOperator::createXor(X, Y, "tmp"), I);
5087 Op1 = InsertNewInstBefore(BinaryOperator::createAnd(Op1, Z, "tmp"), I);
5088 I.setOperand(0, Op1);
5089 I.setOperand(1, Constant::getNullValue(Op1->getType()));
5094 return Changed ? &I : 0;
5098 /// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS
5099 /// and CmpRHS are both known to be integer constants.
5100 Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
5101 ConstantInt *DivRHS) {
5102 ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1));
5103 const APInt &CmpRHSV = CmpRHS->getValue();
5105 // FIXME: If the operand types don't match the type of the divide
5106 // then don't attempt this transform. The code below doesn't have the
5107 // logic to deal with a signed divide and an unsigned compare (and
5108 // vice versa). This is because (x /s C1) <s C2 produces different
5109 // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
5110 // (x /u C1) <u C2. Simply casting the operands and result won't
5111 // work. :( The if statement below tests that condition and bails
5113 bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv;
5114 if (!ICI.isEquality() && DivIsSigned != ICI.isSignedPredicate())
5116 if (DivRHS->isZero())
5117 return 0; // The ProdOV computation fails on divide by zero.
5119 // Compute Prod = CI * DivRHS. We are essentially solving an equation
5120 // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
5121 // C2 (CI). By solving for X we can turn this into a range check
5122 // instead of computing a divide.
5123 ConstantInt *Prod = Multiply(CmpRHS, DivRHS);
5125 // Determine if the product overflows by seeing if the product is
5126 // not equal to the divide. Make sure we do the same kind of divide
5127 // as in the LHS instruction that we're folding.
5128 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
5129 ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
5131 // Get the ICmp opcode
5132 ICmpInst::Predicate Pred = ICI.getPredicate();
5134 // Figure out the interval that is being checked. For example, a comparison
5135 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
5136 // Compute this interval based on the constants involved and the signedness of
5137 // the compare/divide. This computes a half-open interval, keeping track of
5138 // whether either value in the interval overflows. After analysis each
5139 // overflow variable is set to 0 if it's corresponding bound variable is valid
5140 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
5141 int LoOverflow = 0, HiOverflow = 0;
5142 ConstantInt *LoBound = 0, *HiBound = 0;
5145 if (!DivIsSigned) { // udiv
5146 // e.g. X/5 op 3 --> [15, 20)
5148 HiOverflow = LoOverflow = ProdOV;
5150 HiOverflow = AddWithOverflow(HiBound, LoBound, DivRHS, false);
5151 } else if (DivRHS->getValue().isPositive()) { // Divisor is > 0.
5152 if (CmpRHSV == 0) { // (X / pos) op 0
5153 // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
5154 LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
5156 } else if (CmpRHSV.isPositive()) { // (X / pos) op pos
5157 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
5158 HiOverflow = LoOverflow = ProdOV;
5160 HiOverflow = AddWithOverflow(HiBound, Prod, DivRHS, true);
5161 } else { // (X / pos) op neg
5162 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
5163 Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
5164 LoOverflow = AddWithOverflow(LoBound, Prod,
5165 cast<ConstantInt>(DivRHSH), true) ? -1 : 0;
5166 HiBound = AddOne(Prod);
5167 HiOverflow = ProdOV ? -1 : 0;
5169 } else { // Divisor is < 0.
5170 if (CmpRHSV == 0) { // (X / neg) op 0
5171 // e.g. X/-5 op 0 --> [-4, 5)
5172 LoBound = AddOne(DivRHS);
5173 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
5174 if (HiBound == DivRHS) { // -INTMIN = INTMIN
5175 HiOverflow = 1; // [INTMIN+1, overflow)
5176 HiBound = 0; // e.g. X/INTMIN = 0 --> X > INTMIN
5178 } else if (CmpRHSV.isPositive()) { // (X / neg) op pos
5179 // e.g. X/-5 op 3 --> [-19, -14)
5180 HiOverflow = LoOverflow = ProdOV ? -1 : 0;
5182 LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS), true) ?-1:0;
5183 HiBound = AddOne(Prod);
5184 } else { // (X / neg) op neg
5185 // e.g. X/-5 op -3 --> [15, 20)
5187 LoOverflow = HiOverflow = ProdOV ? 1 : 0;
5188 HiBound = Subtract(Prod, DivRHS);
5191 // Dividing by a negative swaps the condition. LT <-> GT
5192 Pred = ICmpInst::getSwappedPredicate(Pred);
5195 Value *X = DivI->getOperand(0);
5197 default: assert(0 && "Unhandled icmp opcode!");
5198 case ICmpInst::ICMP_EQ:
5199 if (LoOverflow && HiOverflow)
5200 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
5201 else if (HiOverflow)
5202 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
5203 ICmpInst::ICMP_UGE, X, LoBound);
5204 else if (LoOverflow)
5205 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
5206 ICmpInst::ICMP_ULT, X, HiBound);
5208 return InsertRangeTest(X, LoBound, HiBound, DivIsSigned, true, ICI);
5209 case ICmpInst::ICMP_NE:
5210 if (LoOverflow && HiOverflow)
5211 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
5212 else if (HiOverflow)
5213 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
5214 ICmpInst::ICMP_ULT, X, LoBound);
5215 else if (LoOverflow)
5216 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
5217 ICmpInst::ICMP_UGE, X, HiBound);
5219 return InsertRangeTest(X, LoBound, HiBound, DivIsSigned, false, ICI);
5220 case ICmpInst::ICMP_ULT:
5221 case ICmpInst::ICMP_SLT:
5222 if (LoOverflow == +1) // Low bound is greater than input range.
5223 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
5224 if (LoOverflow == -1) // Low bound is less than input range.
5225 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
5226 return new ICmpInst(Pred, X, LoBound);
5227 case ICmpInst::ICMP_UGT:
5228 case ICmpInst::ICMP_SGT:
5229 if (HiOverflow == +1) // High bound greater than input range.
5230 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
5231 else if (HiOverflow == -1) // High bound less than input range.
5232 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
5233 if (Pred == ICmpInst::ICMP_UGT)
5234 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
5236 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
5241 /// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
5243 Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
5246 const APInt &RHSV = RHS->getValue();
5248 switch (LHSI->getOpcode()) {
5249 case Instruction::Xor: // (icmp pred (xor X, XorCST), CI)
5250 if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
5251 // If this is a comparison that tests the signbit (X < 0) or (x > -1),
5253 if (ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0 ||
5254 ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue()) {
5255 Value *CompareVal = LHSI->getOperand(0);
5257 // If the sign bit of the XorCST is not set, there is no change to
5258 // the operation, just stop using the Xor.
5259 if (!XorCST->getValue().isNegative()) {
5260 ICI.setOperand(0, CompareVal);
5261 AddToWorkList(LHSI);
5265 // Was the old condition true if the operand is positive?
5266 bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT;
5268 // If so, the new one isn't.
5269 isTrueIfPositive ^= true;
5271 if (isTrueIfPositive)
5272 return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, SubOne(RHS));
5274 return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, AddOne(RHS));
5278 case Instruction::And: // (icmp pred (and X, AndCST), RHS)
5279 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
5280 LHSI->getOperand(0)->hasOneUse()) {
5281 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
5283 // If the LHS is an AND of a truncating cast, we can widen the
5284 // and/compare to be the input width without changing the value
5285 // produced, eliminating a cast.
5286 if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) {
5287 // We can do this transformation if either the AND constant does not
5288 // have its sign bit set or if it is an equality comparison.
5289 // Extending a relational comparison when we're checking the sign
5290 // bit would not work.
5291 if (Cast->hasOneUse() &&
5292 (ICI.isEquality() || AndCST->getValue().isPositive() &&
5293 RHSV.isPositive())) {
5295 cast<IntegerType>(Cast->getOperand(0)->getType())->getBitWidth();
5296 APInt NewCST = AndCST->getValue();
5297 NewCST.zext(BitWidth);
5299 NewCI.zext(BitWidth);
5300 Instruction *NewAnd =
5301 BinaryOperator::createAnd(Cast->getOperand(0),
5302 ConstantInt::get(NewCST),LHSI->getName());
5303 InsertNewInstBefore(NewAnd, ICI);
5304 return new ICmpInst(ICI.getPredicate(), NewAnd,
5305 ConstantInt::get(NewCI));
5309 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
5310 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
5311 // happens a LOT in code produced by the C front-end, for bitfield
5313 BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0));
5314 if (Shift && !Shift->isShift())
5318 ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0;
5319 const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift.
5320 const Type *AndTy = AndCST->getType(); // Type of the and.
5322 // We can fold this as long as we can't shift unknown bits
5323 // into the mask. This can only happen with signed shift
5324 // rights, as they sign-extend.
5326 bool CanFold = Shift->isLogicalShift();
5328 // To test for the bad case of the signed shr, see if any
5329 // of the bits shifted in could be tested after the mask.
5330 uint32_t TyBits = Ty->getPrimitiveSizeInBits();
5331 int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits);
5333 uint32_t BitWidth = AndTy->getPrimitiveSizeInBits();
5334 if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) &
5335 AndCST->getValue()) == 0)
5341 if (Shift->getOpcode() == Instruction::Shl)
5342 NewCst = ConstantExpr::getLShr(RHS, ShAmt);
5344 NewCst = ConstantExpr::getShl(RHS, ShAmt);
5346 // Check to see if we are shifting out any of the bits being
5348 if (ConstantExpr::get(Shift->getOpcode(), NewCst, ShAmt) != RHS) {
5349 // If we shifted bits out, the fold is not going to work out.
5350 // As a special case, check to see if this means that the
5351 // result is always true or false now.
5352 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
5353 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
5354 if (ICI.getPredicate() == ICmpInst::ICMP_NE)
5355 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
5357 ICI.setOperand(1, NewCst);
5358 Constant *NewAndCST;
5359 if (Shift->getOpcode() == Instruction::Shl)
5360 NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt);
5362 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
5363 LHSI->setOperand(1, NewAndCST);
5364 LHSI->setOperand(0, Shift->getOperand(0));
5365 AddToWorkList(Shift); // Shift is dead.
5366 AddUsesToWorkList(ICI);
5372 // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is
5373 // preferable because it allows the C<<Y expression to be hoisted out
5374 // of a loop if Y is invariant and X is not.
5375 if (Shift && Shift->hasOneUse() && RHSV == 0 &&
5376 ICI.isEquality() && !Shift->isArithmeticShift() &&
5377 isa<Instruction>(Shift->getOperand(0))) {
5380 if (Shift->getOpcode() == Instruction::LShr) {
5381 NS = BinaryOperator::createShl(AndCST,
5382 Shift->getOperand(1), "tmp");
5384 // Insert a logical shift.
5385 NS = BinaryOperator::createLShr(AndCST,
5386 Shift->getOperand(1), "tmp");
5388 InsertNewInstBefore(cast<Instruction>(NS), ICI);
5390 // Compute X & (C << Y).
5391 Instruction *NewAnd =
5392 BinaryOperator::createAnd(Shift->getOperand(0), NS, LHSI->getName());
5393 InsertNewInstBefore(NewAnd, ICI);
5395 ICI.setOperand(0, NewAnd);
5401 case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI)
5402 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
5405 uint32_t TypeBits = RHSV.getBitWidth();
5407 // Check that the shift amount is in range. If not, don't perform
5408 // undefined shifts. When the shift is visited it will be
5410 if (ShAmt->uge(TypeBits))
5413 if (ICI.isEquality()) {
5414 // If we are comparing against bits always shifted out, the
5415 // comparison cannot succeed.
5417 ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt), ShAmt);
5418 if (Comp != RHS) {// Comparing against a bit that we know is zero.
5419 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
5420 Constant *Cst = ConstantInt::get(Type::Int1Ty, IsICMP_NE);
5421 return ReplaceInstUsesWith(ICI, Cst);
5424 if (LHSI->hasOneUse()) {
5425 // Otherwise strength reduce the shift into an and.
5426 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
5428 ConstantInt::get(APInt::getLowBitsSet(TypeBits, TypeBits-ShAmtVal));
5431 BinaryOperator::createAnd(LHSI->getOperand(0),
5432 Mask, LHSI->getName()+".mask");
5433 Value *And = InsertNewInstBefore(AndI, ICI);
5434 return new ICmpInst(ICI.getPredicate(), And,
5435 ConstantInt::get(RHSV.lshr(ShAmtVal)));
5439 // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
5440 bool TrueIfSigned = false;
5441 if (LHSI->hasOneUse() &&
5442 isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) {
5443 // (X << 31) <s 0 --> (X&1) != 0
5444 Constant *Mask = ConstantInt::get(APInt(TypeBits, 1) <<
5445 (TypeBits-ShAmt->getZExtValue()-1));
5447 BinaryOperator::createAnd(LHSI->getOperand(0),
5448 Mask, LHSI->getName()+".mask");
5449 Value *And = InsertNewInstBefore(AndI, ICI);
5451 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
5452 And, Constant::getNullValue(And->getType()));
5457 case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
5458 case Instruction::AShr: {
5459 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
5462 if (ICI.isEquality()) {
5463 // Check that the shift amount is in range. If not, don't perform
5464 // undefined shifts. When the shift is visited it will be
5466 uint32_t TypeBits = RHSV.getBitWidth();
5467 if (ShAmt->uge(TypeBits))
5469 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
5471 // If we are comparing against bits always shifted out, the
5472 // comparison cannot succeed.
5473 APInt Comp = RHSV << ShAmtVal;
5474 if (LHSI->getOpcode() == Instruction::LShr)
5475 Comp = Comp.lshr(ShAmtVal);
5477 Comp = Comp.ashr(ShAmtVal);
5479 if (Comp != RHSV) { // Comparing against a bit that we know is zero.
5480 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
5481 Constant *Cst = ConstantInt::get(Type::Int1Ty, IsICMP_NE);
5482 return ReplaceInstUsesWith(ICI, Cst);
5485 if (LHSI->hasOneUse() || RHSV == 0) {
5486 // Otherwise strength reduce the shift into an and.
5487 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
5488 Constant *Mask = ConstantInt::get(Val);
5491 BinaryOperator::createAnd(LHSI->getOperand(0),
5492 Mask, LHSI->getName()+".mask");
5493 Value *And = InsertNewInstBefore(AndI, ICI);
5494 return new ICmpInst(ICI.getPredicate(), And,
5495 ConstantExpr::getShl(RHS, ShAmt));
5501 case Instruction::SDiv:
5502 case Instruction::UDiv:
5503 // Fold: icmp pred ([us]div X, C1), C2 -> range test
5504 // Fold this div into the comparison, producing a range check.
5505 // Determine, based on the divide type, what the range is being
5506 // checked. If there is an overflow on the low or high side, remember
5507 // it, otherwise compute the range [low, hi) bounding the new value.
5508 // See: InsertRangeTest above for the kinds of replacements possible.
5509 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
5510 if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
5516 // Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
5517 if (ICI.isEquality()) {
5518 bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
5520 // If the first operand is (add|sub|and|or|xor|rem) with a constant, and
5521 // the second operand is a constant, simplify a bit.
5522 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) {
5523 switch (BO->getOpcode()) {
5524 case Instruction::SRem:
5525 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
5526 if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){
5527 const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue();
5528 if (V.sgt(APInt(V.getBitWidth(), 1)) && V.isPowerOf2()) {
5529 Instruction *NewRem =
5530 BinaryOperator::createURem(BO->getOperand(0), BO->getOperand(1),
5532 InsertNewInstBefore(NewRem, ICI);
5533 return new ICmpInst(ICI.getPredicate(), NewRem,
5534 Constant::getNullValue(BO->getType()));
5538 case Instruction::Add:
5539 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
5540 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
5541 if (BO->hasOneUse())
5542 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
5543 Subtract(RHS, BOp1C));
5544 } else if (RHSV == 0) {
5545 // Replace ((add A, B) != 0) with (A != -B) if A or B is
5546 // efficiently invertible, or if the add has just this one use.
5547 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
5549 if (Value *NegVal = dyn_castNegVal(BOp1))
5550 return new ICmpInst(ICI.getPredicate(), BOp0, NegVal);
5551 else if (Value *NegVal = dyn_castNegVal(BOp0))
5552 return new ICmpInst(ICI.getPredicate(), NegVal, BOp1);
5553 else if (BO->hasOneUse()) {
5554 Instruction *Neg = BinaryOperator::createNeg(BOp1);
5555 InsertNewInstBefore(Neg, ICI);
5557 return new ICmpInst(ICI.getPredicate(), BOp0, Neg);
5561 case Instruction::Xor:
5562 // For the xor case, we can xor two constants together, eliminating
5563 // the explicit xor.
5564 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
5565 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
5566 ConstantExpr::getXor(RHS, BOC));
5569 case Instruction::Sub:
5570 // Replace (([sub|xor] A, B) != 0) with (A != B)
5572 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
5576 case Instruction::Or:
5577 // If bits are being or'd in that are not present in the constant we
5578 // are comparing against, then the comparison could never succeed!
5579 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
5580 Constant *NotCI = ConstantExpr::getNot(RHS);
5581 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
5582 return ReplaceInstUsesWith(ICI, ConstantInt::get(Type::Int1Ty,
5587 case Instruction::And:
5588 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
5589 // If bits are being compared against that are and'd out, then the
5590 // comparison can never succeed!
5591 if ((RHSV & ~BOC->getValue()) != 0)
5592 return ReplaceInstUsesWith(ICI, ConstantInt::get(Type::Int1Ty,
5595 // If we have ((X & C) == C), turn it into ((X & C) != 0).
5596 if (RHS == BOC && RHSV.isPowerOf2())
5597 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ :
5598 ICmpInst::ICMP_NE, LHSI,
5599 Constant::getNullValue(RHS->getType()));
5601 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
5602 if (isSignBit(BOC)) {
5603 Value *X = BO->getOperand(0);
5604 Constant *Zero = Constant::getNullValue(X->getType());
5605 ICmpInst::Predicate pred = isICMP_NE ?
5606 ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
5607 return new ICmpInst(pred, X, Zero);
5610 // ((X & ~7) == 0) --> X < 8
5611 if (RHSV == 0 && isHighOnes(BOC)) {
5612 Value *X = BO->getOperand(0);
5613 Constant *NegX = ConstantExpr::getNeg(BOC);
5614 ICmpInst::Predicate pred = isICMP_NE ?
5615 ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
5616 return new ICmpInst(pred, X, NegX);
5621 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) {
5622 // Handle icmp {eq|ne} <intrinsic>, intcst.
5623 if (II->getIntrinsicID() == Intrinsic::bswap) {
5625 ICI.setOperand(0, II->getOperand(1));
5626 ICI.setOperand(1, ConstantInt::get(RHSV.byteSwap()));
5630 } else { // Not a ICMP_EQ/ICMP_NE
5631 // If the LHS is a cast from an integral value of the same size,
5632 // then since we know the RHS is a constant, try to simlify.
5633 if (CastInst *Cast = dyn_cast<CastInst>(LHSI)) {
5634 Value *CastOp = Cast->getOperand(0);
5635 const Type *SrcTy = CastOp->getType();
5636 uint32_t SrcTySize = SrcTy->getPrimitiveSizeInBits();
5637 if (SrcTy->isInteger() &&
5638 SrcTySize == Cast->getType()->getPrimitiveSizeInBits()) {
5639 // If this is an unsigned comparison, try to make the comparison use
5640 // smaller constant values.
5641 if (ICI.getPredicate() == ICmpInst::ICMP_ULT && RHSV.isSignBit()) {
5642 // X u< 128 => X s> -1
5643 return new ICmpInst(ICmpInst::ICMP_SGT, CastOp,
5644 ConstantInt::get(APInt::getAllOnesValue(SrcTySize)));
5645 } else if (ICI.getPredicate() == ICmpInst::ICMP_UGT &&
5646 RHSV == APInt::getSignedMaxValue(SrcTySize)) {
5647 // X u> 127 => X s< 0
5648 return new ICmpInst(ICmpInst::ICMP_SLT, CastOp,
5649 Constant::getNullValue(SrcTy));
5657 /// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst).
5658 /// We only handle extending casts so far.
5660 Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) {
5661 const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0));
5662 Value *LHSCIOp = LHSCI->getOperand(0);
5663 const Type *SrcTy = LHSCIOp->getType();
5664 const Type *DestTy = LHSCI->getType();
5667 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
5668 // integer type is the same size as the pointer type.
5669 if (LHSCI->getOpcode() == Instruction::PtrToInt &&
5670 getTargetData().getPointerSizeInBits() ==
5671 cast<IntegerType>(DestTy)->getBitWidth()) {
5673 if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
5674 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
5675 } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
5676 RHSOp = RHSC->getOperand(0);
5677 // If the pointer types don't match, insert a bitcast.
5678 if (LHSCIOp->getType() != RHSOp->getType())
5679 RHSOp = InsertCastBefore(Instruction::BitCast, RHSOp,
5680 LHSCIOp->getType(), ICI);
5684 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);
5687 // The code below only handles extension cast instructions, so far.
5689 if (LHSCI->getOpcode() != Instruction::ZExt &&
5690 LHSCI->getOpcode() != Instruction::SExt)
5693 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
5694 bool isSignedCmp = ICI.isSignedPredicate();
5696 if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) {
5697 // Not an extension from the same type?
5698 RHSCIOp = CI->getOperand(0);
5699 if (RHSCIOp->getType() != LHSCIOp->getType())
5702 // If the signedness of the two compares doesn't agree (i.e. one is a sext
5703 // and the other is a zext), then we can't handle this.
5704 if (CI->getOpcode() != LHSCI->getOpcode())
5707 // Likewise, if the signedness of the [sz]exts and the compare don't match,
5708 // then we can't handle this.
5709 if (isSignedExt != isSignedCmp && !ICI.isEquality())
5712 // Okay, just insert a compare of the reduced operands now!
5713 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
5716 // If we aren't dealing with a constant on the RHS, exit early
5717 ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1));
5721 // Compute the constant that would happen if we truncated to SrcTy then
5722 // reextended to DestTy.
5723 Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy);
5724 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
5726 // If the re-extended constant didn't change...
5728 // Make sure that sign of the Cmp and the sign of the Cast are the same.
5729 // For example, we might have:
5730 // %A = sext short %X to uint
5731 // %B = icmp ugt uint %A, 1330
5732 // It is incorrect to transform this into
5733 // %B = icmp ugt short %X, 1330
5734 // because %A may have negative value.
5736 // However, it is OK if SrcTy is bool (See cast-set.ll testcase)
5737 // OR operation is EQ/NE.
5738 if (isSignedExt == isSignedCmp || SrcTy == Type::Int1Ty || ICI.isEquality())
5739 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
5744 // The re-extended constant changed so the constant cannot be represented
5745 // in the shorter type. Consequently, we cannot emit a simple comparison.
5747 // First, handle some easy cases. We know the result cannot be equal at this
5748 // point so handle the ICI.isEquality() cases
5749 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
5750 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse());
5751 if (ICI.getPredicate() == ICmpInst::ICMP_NE)
5752 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue());
5754 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
5755 // should have been folded away previously and not enter in here.
5758 // We're performing a signed comparison.
5759 if (cast<ConstantInt>(CI)->getValue().isNegative())
5760 Result = ConstantInt::getFalse(); // X < (small) --> false
5762 Result = ConstantInt::getTrue(); // X < (large) --> true
5764 // We're performing an unsigned comparison.
5766 // We're performing an unsigned comp with a sign extended value.
5767 // This is true if the input is >= 0. [aka >s -1]
5768 Constant *NegOne = ConstantInt::getAllOnesValue(SrcTy);
5769 Result = InsertNewInstBefore(new ICmpInst(ICmpInst::ICMP_SGT, LHSCIOp,
5770 NegOne, ICI.getName()), ICI);
5772 // Unsigned extend & unsigned compare -> always true.
5773 Result = ConstantInt::getTrue();
5777 // Finally, return the value computed.
5778 if (ICI.getPredicate() == ICmpInst::ICMP_ULT ||
5779 ICI.getPredicate() == ICmpInst::ICMP_SLT) {
5780 return ReplaceInstUsesWith(ICI, Result);
5782 assert((ICI.getPredicate()==ICmpInst::ICMP_UGT ||
5783 ICI.getPredicate()==ICmpInst::ICMP_SGT) &&
5784 "ICmp should be folded!");
5785 if (Constant *CI = dyn_cast<Constant>(Result))
5786 return ReplaceInstUsesWith(ICI, ConstantExpr::getNot(CI));
5788 return BinaryOperator::createNot(Result);
5792 Instruction *InstCombiner::visitShl(BinaryOperator &I) {
5793 return commonShiftTransforms(I);
5796 Instruction *InstCombiner::visitLShr(BinaryOperator &I) {
5797 return commonShiftTransforms(I);
5800 Instruction *InstCombiner::visitAShr(BinaryOperator &I) {
5801 return commonShiftTransforms(I);
5804 Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) {
5805 assert(I.getOperand(1)->getType() == I.getOperand(0)->getType());
5806 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
5808 // shl X, 0 == X and shr X, 0 == X
5809 // shl 0, X == 0 and shr 0, X == 0
5810 if (Op1 == Constant::getNullValue(Op1->getType()) ||
5811 Op0 == Constant::getNullValue(Op0->getType()))
5812 return ReplaceInstUsesWith(I, Op0);
5814 if (isa<UndefValue>(Op0)) {
5815 if (I.getOpcode() == Instruction::AShr) // undef >>s X -> undef
5816 return ReplaceInstUsesWith(I, Op0);
5817 else // undef << X -> 0, undef >>u X -> 0
5818 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
5820 if (isa<UndefValue>(Op1)) {
5821 if (I.getOpcode() == Instruction::AShr) // X >>s undef -> X
5822 return ReplaceInstUsesWith(I, Op0);
5823 else // X << undef, X >>u undef -> 0
5824 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
5827 // ashr int -1, X = -1 (for any arithmetic shift rights of ~0)
5828 if (I.getOpcode() == Instruction::AShr)
5829 if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0))
5830 if (CSI->isAllOnesValue())
5831 return ReplaceInstUsesWith(I, CSI);
5833 // Try to fold constant and into select arguments.
5834 if (isa<Constant>(Op0))
5835 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
5836 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
5839 // See if we can turn a signed shr into an unsigned shr.
5840 if (I.isArithmeticShift()) {
5841 if (MaskedValueIsZero(Op0,
5842 APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()))) {
5843 return BinaryOperator::createLShr(Op0, Op1, I.getName());
5847 if (ConstantInt *CUI = dyn_cast<ConstantInt>(Op1))
5848 if (Instruction *Res = FoldShiftByConstant(Op0, CUI, I))
5853 Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
5854 BinaryOperator &I) {
5855 bool isLeftShift = I.getOpcode() == Instruction::Shl;
5857 // See if we can simplify any instructions used by the instruction whose sole
5858 // purpose is to compute bits we don't care about.
5859 uint32_t TypeBits = Op0->getType()->getPrimitiveSizeInBits();
5860 APInt KnownZero(TypeBits, 0), KnownOne(TypeBits, 0);
5861 if (SimplifyDemandedBits(&I, APInt::getAllOnesValue(TypeBits),
5862 KnownZero, KnownOne))
5865 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
5866 // of a signed value.
5868 if (Op1->uge(TypeBits)) {
5869 if (I.getOpcode() != Instruction::AShr)
5870 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
5872 I.setOperand(1, ConstantInt::get(I.getType(), TypeBits-1));
5877 // ((X*C1) << C2) == (X * (C1 << C2))
5878 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
5879 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
5880 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
5881 return BinaryOperator::createMul(BO->getOperand(0),
5882 ConstantExpr::getShl(BOOp, Op1));
5884 // Try to fold constant and into select arguments.
5885 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
5886 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
5888 if (isa<PHINode>(Op0))
5889 if (Instruction *NV = FoldOpIntoPhi(I))
5892 if (Op0->hasOneUse()) {
5893 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) {
5894 // Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
5897 switch (Op0BO->getOpcode()) {
5899 case Instruction::Add:
5900 case Instruction::And:
5901 case Instruction::Or:
5902 case Instruction::Xor: {
5903 // These operators commute.
5904 // Turn (Y + (X >> C)) << C -> (X + (Y << C)) & (~0 << C)
5905 if (isLeftShift && Op0BO->getOperand(1)->hasOneUse() &&
5906 match(Op0BO->getOperand(1),
5907 m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == Op1) {
5908 Instruction *YS = BinaryOperator::createShl(
5909 Op0BO->getOperand(0), Op1,
5911 InsertNewInstBefore(YS, I); // (Y << C)
5913 BinaryOperator::create(Op0BO->getOpcode(), YS, V1,
5914 Op0BO->getOperand(1)->getName());
5915 InsertNewInstBefore(X, I); // (X + (Y << C))
5916 uint32_t Op1Val = Op1->getLimitedValue(TypeBits);
5917 return BinaryOperator::createAnd(X, ConstantInt::get(
5918 APInt::getHighBitsSet(TypeBits, TypeBits-Op1Val)));
5921 // Turn (Y + ((X >> C) & CC)) << C -> ((X & (CC << C)) + (Y << C))
5922 Value *Op0BOOp1 = Op0BO->getOperand(1);
5923 if (isLeftShift && Op0BOOp1->hasOneUse() &&
5925 m_And(m_Shr(m_Value(V1), m_Value(V2)),m_ConstantInt(CC))) &&
5926 cast<BinaryOperator>(Op0BOOp1)->getOperand(0)->hasOneUse() &&
5928 Instruction *YS = BinaryOperator::createShl(
5929 Op0BO->getOperand(0), Op1,
5931 InsertNewInstBefore(YS, I); // (Y << C)
5933 BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, Op1),
5934 V1->getName()+".mask");
5935 InsertNewInstBefore(XM, I); // X & (CC << C)
5937 return BinaryOperator::create(Op0BO->getOpcode(), YS, XM);
5942 case Instruction::Sub: {
5943 // Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
5944 if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
5945 match(Op0BO->getOperand(0),
5946 m_Shr(m_Value(V1), m_ConstantInt(CC))) && CC == Op1) {
5947 Instruction *YS = BinaryOperator::createShl(
5948 Op0BO->getOperand(1), Op1,
5950 InsertNewInstBefore(YS, I); // (Y << C)
5952 BinaryOperator::create(Op0BO->getOpcode(), V1, YS,
5953 Op0BO->getOperand(0)->getName());
5954 InsertNewInstBefore(X, I); // (X + (Y << C))
5955 uint32_t Op1Val = Op1->getLimitedValue(TypeBits);
5956 return BinaryOperator::createAnd(X, ConstantInt::get(
5957 APInt::getHighBitsSet(TypeBits, TypeBits-Op1Val)));
5960 // Turn (((X >> C)&CC) + Y) << C -> (X + (Y << C)) & (CC << C)
5961 if (isLeftShift && Op0BO->getOperand(0)->hasOneUse() &&
5962 match(Op0BO->getOperand(0),
5963 m_And(m_Shr(m_Value(V1), m_Value(V2)),
5964 m_ConstantInt(CC))) && V2 == Op1 &&
5965 cast<BinaryOperator>(Op0BO->getOperand(0))
5966 ->getOperand(0)->hasOneUse()) {
5967 Instruction *YS = BinaryOperator::createShl(
5968 Op0BO->getOperand(1), Op1,
5970 InsertNewInstBefore(YS, I); // (Y << C)
5972 BinaryOperator::createAnd(V1, ConstantExpr::getShl(CC, Op1),
5973 V1->getName()+".mask");
5974 InsertNewInstBefore(XM, I); // X & (CC << C)
5976 return BinaryOperator::create(Op0BO->getOpcode(), XM, YS);
5984 // If the operand is an bitwise operator with a constant RHS, and the
5985 // shift is the only use, we can pull it out of the shift.
5986 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
5987 bool isValid = true; // Valid only for And, Or, Xor
5988 bool highBitSet = false; // Transform if high bit of constant set?
5990 switch (Op0BO->getOpcode()) {
5991 default: isValid = false; break; // Do not perform transform!
5992 case Instruction::Add:
5993 isValid = isLeftShift;
5995 case Instruction::Or:
5996 case Instruction::Xor:
5999 case Instruction::And:
6004 // If this is a signed shift right, and the high bit is modified
6005 // by the logical operation, do not perform the transformation.
6006 // The highBitSet boolean indicates the value of the high bit of
6007 // the constant which would cause it to be modified for this
6010 if (isValid && !isLeftShift && I.getOpcode() == Instruction::AShr) {
6011 isValid = Op0C->getValue()[TypeBits-1] == highBitSet;
6015 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, Op1);
6017 Instruction *NewShift =
6018 BinaryOperator::create(I.getOpcode(), Op0BO->getOperand(0), Op1);
6019 InsertNewInstBefore(NewShift, I);
6020 NewShift->takeName(Op0BO);
6022 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
6029 // Find out if this is a shift of a shift by a constant.
6030 BinaryOperator *ShiftOp = dyn_cast<BinaryOperator>(Op0);
6031 if (ShiftOp && !ShiftOp->isShift())
6034 if (ShiftOp && isa<ConstantInt>(ShiftOp->getOperand(1))) {
6035 ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1));
6036 uint32_t ShiftAmt1 = ShiftAmt1C->getLimitedValue(TypeBits);
6037 uint32_t ShiftAmt2 = Op1->getLimitedValue(TypeBits);
6038 assert(ShiftAmt2 != 0 && "Should have been simplified earlier");
6039 if (ShiftAmt1 == 0) return 0; // Will be simplified in the future.
6040 Value *X = ShiftOp->getOperand(0);
6042 uint32_t AmtSum = ShiftAmt1+ShiftAmt2; // Fold into one big shift.
6043 if (AmtSum > TypeBits)
6046 const IntegerType *Ty = cast<IntegerType>(I.getType());
6048 // Check for (X << c1) << c2 and (X >> c1) >> c2
6049 if (I.getOpcode() == ShiftOp->getOpcode()) {
6050 return BinaryOperator::create(I.getOpcode(), X,
6051 ConstantInt::get(Ty, AmtSum));
6052 } else if (ShiftOp->getOpcode() == Instruction::LShr &&
6053 I.getOpcode() == Instruction::AShr) {
6054 // ((X >>u C1) >>s C2) -> (X >>u (C1+C2)) since C1 != 0.
6055 return BinaryOperator::createLShr(X, ConstantInt::get(Ty, AmtSum));
6056 } else if (ShiftOp->getOpcode() == Instruction::AShr &&
6057 I.getOpcode() == Instruction::LShr) {
6058 // ((X >>s C1) >>u C2) -> ((X >>s (C1+C2)) & mask) since C1 != 0.
6059 Instruction *Shift =
6060 BinaryOperator::createAShr(X, ConstantInt::get(Ty, AmtSum));
6061 InsertNewInstBefore(Shift, I);
6063 APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
6064 return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
6067 // Okay, if we get here, one shift must be left, and the other shift must be
6068 // right. See if the amounts are equal.
6069 if (ShiftAmt1 == ShiftAmt2) {
6070 // If we have ((X >>? C) << C), turn this into X & (-1 << C).
6071 if (I.getOpcode() == Instruction::Shl) {
6072 APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1));
6073 return BinaryOperator::createAnd(X, ConstantInt::get(Mask));
6075 // If we have ((X << C) >>u C), turn this into X & (-1 >>u C).
6076 if (I.getOpcode() == Instruction::LShr) {
6077 APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt1));
6078 return BinaryOperator::createAnd(X, ConstantInt::get(Mask));
6080 // We can simplify ((X << C) >>s C) into a trunc + sext.
6081 // NOTE: we could do this for any C, but that would make 'unusual' integer
6082 // types. For now, just stick to ones well-supported by the code
6084 const Type *SExtType = 0;
6085 switch (Ty->getBitWidth() - ShiftAmt1) {
6092 SExtType = IntegerType::get(Ty->getBitWidth() - ShiftAmt1);
6097 Instruction *NewTrunc = new TruncInst(X, SExtType, "sext");
6098 InsertNewInstBefore(NewTrunc, I);
6099 return new SExtInst(NewTrunc, Ty);
6101 // Otherwise, we can't handle it yet.
6102 } else if (ShiftAmt1 < ShiftAmt2) {
6103 uint32_t ShiftDiff = ShiftAmt2-ShiftAmt1;
6105 // (X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2)
6106 if (I.getOpcode() == Instruction::Shl) {
6107 assert(ShiftOp->getOpcode() == Instruction::LShr ||
6108 ShiftOp->getOpcode() == Instruction::AShr);
6109 Instruction *Shift =
6110 BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff));
6111 InsertNewInstBefore(Shift, I);
6113 APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
6114 return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
6117 // (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2)
6118 if (I.getOpcode() == Instruction::LShr) {
6119 assert(ShiftOp->getOpcode() == Instruction::Shl);
6120 Instruction *Shift =
6121 BinaryOperator::createLShr(X, ConstantInt::get(Ty, ShiftDiff));
6122 InsertNewInstBefore(Shift, I);
6124 APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
6125 return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
6128 // We can't handle (X << C1) >>s C2, it shifts arbitrary bits in.
6130 assert(ShiftAmt2 < ShiftAmt1);
6131 uint32_t ShiftDiff = ShiftAmt1-ShiftAmt2;
6133 // (X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2)
6134 if (I.getOpcode() == Instruction::Shl) {
6135 assert(ShiftOp->getOpcode() == Instruction::LShr ||
6136 ShiftOp->getOpcode() == Instruction::AShr);
6137 Instruction *Shift =
6138 BinaryOperator::create(ShiftOp->getOpcode(), X,
6139 ConstantInt::get(Ty, ShiftDiff));
6140 InsertNewInstBefore(Shift, I);
6142 APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt2));
6143 return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
6146 // (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2)
6147 if (I.getOpcode() == Instruction::LShr) {
6148 assert(ShiftOp->getOpcode() == Instruction::Shl);
6149 Instruction *Shift =
6150 BinaryOperator::createShl(X, ConstantInt::get(Ty, ShiftDiff));
6151 InsertNewInstBefore(Shift, I);
6153 APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
6154 return BinaryOperator::createAnd(Shift, ConstantInt::get(Mask));
6157 // We can't handle (X << C1) >>a C2, it shifts arbitrary bits in.
6164 /// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear
6165 /// expression. If so, decompose it, returning some value X, such that Val is
6168 static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale,
6170 assert(Val->getType() == Type::Int32Ty && "Unexpected allocation size type!");
6171 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) {
6172 Offset = CI->getZExtValue();
6174 return ConstantInt::get(Type::Int32Ty, 0);
6175 } else if (Instruction *I = dyn_cast<Instruction>(Val)) {
6176 if (I->getNumOperands() == 2) {
6177 if (ConstantInt *CUI = dyn_cast<ConstantInt>(I->getOperand(1))) {
6178 if (I->getOpcode() == Instruction::Shl) {
6179 // This is a value scaled by '1 << the shift amt'.
6180 Scale = 1U << CUI->getZExtValue();
6182 return I->getOperand(0);
6183 } else if (I->getOpcode() == Instruction::Mul) {
6184 // This value is scaled by 'CUI'.
6185 Scale = CUI->getZExtValue();
6187 return I->getOperand(0);
6188 } else if (I->getOpcode() == Instruction::Add) {
6189 // We have X+C. Check to see if we really have (X*C2)+C1,
6190 // where C1 is divisible by C2.
6193 DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset);
6194 Offset += CUI->getZExtValue();
6195 if (SubScale > 1 && (Offset % SubScale == 0)) {
6204 // Otherwise, we can't look past this.
6211 /// PromoteCastOfAllocation - If we find a cast of an allocation instruction,
6212 /// try to eliminate the cast by moving the type information into the alloc.
6213 Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI,
6214 AllocationInst &AI) {
6215 const PointerType *PTy = cast<PointerType>(CI.getType());
6217 // Remove any uses of AI that are dead.
6218 assert(!CI.use_empty() && "Dead instructions should be removed earlier!");
6220 for (Value::use_iterator UI = AI.use_begin(), E = AI.use_end(); UI != E; ) {
6221 Instruction *User = cast<Instruction>(*UI++);
6222 if (isInstructionTriviallyDead(User)) {
6223 while (UI != E && *UI == User)
6224 ++UI; // If this instruction uses AI more than once, don't break UI.
6227 DOUT << "IC: DCE: " << *User;
6228 EraseInstFromFunction(*User);
6232 // Get the type really allocated and the type casted to.
6233 const Type *AllocElTy = AI.getAllocatedType();
6234 const Type *CastElTy = PTy->getElementType();
6235 if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
6237 unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy);
6238 unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy);
6239 if (CastElTyAlign < AllocElTyAlign) return 0;
6241 // If the allocation has multiple uses, only promote it if we are strictly
6242 // increasing the alignment of the resultant allocation. If we keep it the
6243 // same, we open the door to infinite loops of various kinds.
6244 if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0;
6246 uint64_t AllocElTySize = TD->getTypeSize(AllocElTy);
6247 uint64_t CastElTySize = TD->getTypeSize(CastElTy);
6248 if (CastElTySize == 0 || AllocElTySize == 0) return 0;
6250 // See if we can satisfy the modulus by pulling a scale out of the array
6252 unsigned ArraySizeScale;
6254 Value *NumElements = // See if the array size is a decomposable linear expr.
6255 DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset);
6257 // If we can now satisfy the modulus, by using a non-1 scale, we really can
6259 if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 ||
6260 (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0;
6262 unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize;
6267 // If the allocation size is constant, form a constant mul expression
6268 Amt = ConstantInt::get(Type::Int32Ty, Scale);
6269 if (isa<ConstantInt>(NumElements))
6270 Amt = Multiply(cast<ConstantInt>(NumElements), cast<ConstantInt>(Amt));
6271 // otherwise multiply the amount and the number of elements
6272 else if (Scale != 1) {
6273 Instruction *Tmp = BinaryOperator::createMul(Amt, NumElements, "tmp");
6274 Amt = InsertNewInstBefore(Tmp, AI);
6278 if (int Offset = (AllocElTySize*ArrayOffset)/CastElTySize) {
6279 Value *Off = ConstantInt::get(Type::Int32Ty, Offset, true);
6280 Instruction *Tmp = BinaryOperator::createAdd(Amt, Off, "tmp");
6281 Amt = InsertNewInstBefore(Tmp, AI);
6284 AllocationInst *New;
6285 if (isa<MallocInst>(AI))
6286 New = new MallocInst(CastElTy, Amt, AI.getAlignment());
6288 New = new AllocaInst(CastElTy, Amt, AI.getAlignment());
6289 InsertNewInstBefore(New, AI);
6292 // If the allocation has multiple uses, insert a cast and change all things
6293 // that used it to use the new cast. This will also hack on CI, but it will
6295 if (!AI.hasOneUse()) {
6296 AddUsesToWorkList(AI);
6297 // New is the allocation instruction, pointer typed. AI is the original
6298 // allocation instruction, also pointer typed. Thus, cast to use is BitCast.
6299 CastInst *NewCast = new BitCastInst(New, AI.getType(), "tmpcast");
6300 InsertNewInstBefore(NewCast, AI);
6301 AI.replaceAllUsesWith(NewCast);
6303 return ReplaceInstUsesWith(CI, New);
6306 /// CanEvaluateInDifferentType - Return true if we can take the specified value
6307 /// and return it as type Ty without inserting any new casts and without
6308 /// changing the computed value. This is used by code that tries to decide
6309 /// whether promoting or shrinking integer operations to wider or smaller types
6310 /// will allow us to eliminate a truncate or extend.
6312 /// This is a truncation operation if Ty is smaller than V->getType(), or an
6313 /// extension operation if Ty is larger.
6314 static bool CanEvaluateInDifferentType(Value *V, const IntegerType *Ty,
6315 unsigned CastOpc, int &NumCastsRemoved) {
6316 // We can always evaluate constants in another type.
6317 if (isa<ConstantInt>(V))
6320 Instruction *I = dyn_cast<Instruction>(V);
6321 if (!I) return false;
6323 const IntegerType *OrigTy = cast<IntegerType>(V->getType());
6325 // If this is an extension or truncate, we can often eliminate it.
6326 if (isa<TruncInst>(I) || isa<ZExtInst>(I) || isa<SExtInst>(I)) {
6327 // If this is a cast from the destination type, we can trivially eliminate
6328 // it, and this will remove a cast overall.
6329 if (I->getOperand(0)->getType() == Ty) {
6330 // If the first operand is itself a cast, and is eliminable, do not count
6331 // this as an eliminable cast. We would prefer to eliminate those two
6333 if (!isa<CastInst>(I->getOperand(0)))
6339 // We can't extend or shrink something that has multiple uses: doing so would
6340 // require duplicating the instruction in general, which isn't profitable.
6341 if (!I->hasOneUse()) return false;
6343 switch (I->getOpcode()) {
6344 case Instruction::Add:
6345 case Instruction::Sub:
6346 case Instruction::And:
6347 case Instruction::Or:
6348 case Instruction::Xor:
6349 // These operators can all arbitrarily be extended or truncated.
6350 return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
6352 CanEvaluateInDifferentType(I->getOperand(1), Ty, CastOpc,
6355 case Instruction::Shl:
6356 // If we are truncating the result of this SHL, and if it's a shift of a
6357 // constant amount, we can always perform a SHL in a smaller type.
6358 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
6359 uint32_t BitWidth = Ty->getBitWidth();
6360 if (BitWidth < OrigTy->getBitWidth() &&
6361 CI->getLimitedValue(BitWidth) < BitWidth)
6362 return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
6366 case Instruction::LShr:
6367 // If this is a truncate of a logical shr, we can truncate it to a smaller
6368 // lshr iff we know that the bits we would otherwise be shifting in are
6370 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
6371 uint32_t OrigBitWidth = OrigTy->getBitWidth();
6372 uint32_t BitWidth = Ty->getBitWidth();
6373 if (BitWidth < OrigBitWidth &&
6374 MaskedValueIsZero(I->getOperand(0),
6375 APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) &&
6376 CI->getLimitedValue(BitWidth) < BitWidth) {
6377 return CanEvaluateInDifferentType(I->getOperand(0), Ty, CastOpc,
6382 case Instruction::ZExt:
6383 case Instruction::SExt:
6384 case Instruction::Trunc:
6385 // If this is the same kind of case as our original (e.g. zext+zext), we
6386 // can safely replace it. Note that replacing it does not reduce the number
6387 // of casts in the input.
6388 if (I->getOpcode() == CastOpc)
6392 // TODO: Can handle more cases here.
6399 /// EvaluateInDifferentType - Given an expression that
6400 /// CanEvaluateInDifferentType returns true for, actually insert the code to
6401 /// evaluate the expression.
6402 Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty,
6404 if (Constant *C = dyn_cast<Constant>(V))
6405 return ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/);
6407 // Otherwise, it must be an instruction.
6408 Instruction *I = cast<Instruction>(V);
6409 Instruction *Res = 0;
6410 switch (I->getOpcode()) {
6411 case Instruction::Add:
6412 case Instruction::Sub:
6413 case Instruction::And:
6414 case Instruction::Or:
6415 case Instruction::Xor:
6416 case Instruction::AShr:
6417 case Instruction::LShr:
6418 case Instruction::Shl: {
6419 Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
6420 Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
6421 Res = BinaryOperator::create((Instruction::BinaryOps)I->getOpcode(),
6422 LHS, RHS, I->getName());
6425 case Instruction::Trunc:
6426 case Instruction::ZExt:
6427 case Instruction::SExt:
6428 // If the source type of the cast is the type we're trying for then we can
6429 // just return the source. There's no need to insert it because it is not
6431 if (I->getOperand(0)->getType() == Ty)
6432 return I->getOperand(0);
6434 // Otherwise, must be the same type of case, so just reinsert a new one.
6435 Res = CastInst::create(cast<CastInst>(I)->getOpcode(), I->getOperand(0),
6439 // TODO: Can handle more cases here.
6440 assert(0 && "Unreachable!");
6444 return InsertNewInstBefore(Res, *I);
6447 /// @brief Implement the transforms common to all CastInst visitors.
6448 Instruction *InstCombiner::commonCastTransforms(CastInst &CI) {
6449 Value *Src = CI.getOperand(0);
6451 // Many cases of "cast of a cast" are eliminable. If it's eliminable we just
6452 // eliminate it now.
6453 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
6454 if (Instruction::CastOps opc =
6455 isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) {
6456 // The first cast (CSrc) is eliminable so we need to fix up or replace
6457 // the second cast (CI). CSrc will then have a good chance of being dead.
6458 return CastInst::create(opc, CSrc->getOperand(0), CI.getType());
6462 // If we are casting a select then fold the cast into the select
6463 if (SelectInst *SI = dyn_cast<SelectInst>(Src))
6464 if (Instruction *NV = FoldOpIntoSelect(CI, SI, this))
6467 // If we are casting a PHI then fold the cast into the PHI
6468 if (isa<PHINode>(Src))
6469 if (Instruction *NV = FoldOpIntoPhi(CI))
6475 /// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint)
6476 Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
6477 Value *Src = CI.getOperand(0);
6479 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
6480 // If casting the result of a getelementptr instruction with no offset, turn
6481 // this into a cast of the original pointer!
6482 if (GEP->hasAllZeroIndices()) {
6483 // Changing the cast operand is usually not a good idea but it is safe
6484 // here because the pointer operand is being replaced with another
6485 // pointer operand so the opcode doesn't need to change.
6487 CI.setOperand(0, GEP->getOperand(0));
6491 // If the GEP has a single use, and the base pointer is a bitcast, and the
6492 // GEP computes a constant offset, see if we can convert these three
6493 // instructions into fewer. This typically happens with unions and other
6494 // non-type-safe code.
6495 if (GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0))) {
6496 if (GEP->hasAllConstantIndices()) {
6497 // We are guaranteed to get a constant from EmitGEPOffset.
6498 ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP, CI, *this));
6499 int64_t Offset = OffsetV->getSExtValue();
6501 // Get the base pointer input of the bitcast, and the type it points to.
6502 Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
6503 const Type *GEPIdxTy =
6504 cast<PointerType>(OrigBase->getType())->getElementType();
6505 if (GEPIdxTy->isSized()) {
6506 SmallVector<Value*, 8> NewIndices;
6508 // Start with the index over the outer type. Note that the type size
6509 // might be zero (even if the offset isn't zero) if the indexed type
6510 // is something like [0 x {int, int}]
6511 const Type *IntPtrTy = TD->getIntPtrType();
6512 int64_t FirstIdx = 0;
6513 if (int64_t TySize = TD->getTypeSize(GEPIdxTy)) {
6514 FirstIdx = Offset/TySize;
6517 // Handle silly modulus not returning values values [0..TySize).
6521 assert(Offset >= 0);
6523 assert((uint64_t)Offset < (uint64_t)TySize &&"Out of range offset");
6526 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
6528 // Index into the types. If we fail, set OrigBase to null.
6530 if (const StructType *STy = dyn_cast<StructType>(GEPIdxTy)) {
6531 const StructLayout *SL = TD->getStructLayout(STy);
6532 if (Offset < (int64_t)SL->getSizeInBytes()) {
6533 unsigned Elt = SL->getElementContainingOffset(Offset);
6534 NewIndices.push_back(ConstantInt::get(Type::Int32Ty, Elt));
6536 Offset -= SL->getElementOffset(Elt);
6537 GEPIdxTy = STy->getElementType(Elt);
6539 // Otherwise, we can't index into this, bail out.
6543 } else if (isa<ArrayType>(GEPIdxTy) || isa<VectorType>(GEPIdxTy)) {
6544 const SequentialType *STy = cast<SequentialType>(GEPIdxTy);
6545 if (uint64_t EltSize = TD->getTypeSize(STy->getElementType())) {
6546 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
6549 NewIndices.push_back(ConstantInt::get(IntPtrTy, 0));
6551 GEPIdxTy = STy->getElementType();
6553 // Otherwise, we can't index into this, bail out.
6559 // If we were able to index down into an element, create the GEP
6560 // and bitcast the result. This eliminates one bitcast, potentially
6562 Instruction *NGEP = new GetElementPtrInst(OrigBase, &NewIndices[0],
6563 NewIndices.size(), "");
6564 InsertNewInstBefore(NGEP, CI);
6565 NGEP->takeName(GEP);
6567 if (isa<BitCastInst>(CI))
6568 return new BitCastInst(NGEP, CI.getType());
6569 assert(isa<PtrToIntInst>(CI));
6570 return new PtrToIntInst(NGEP, CI.getType());
6577 return commonCastTransforms(CI);
6582 /// Only the TRUNC, ZEXT, SEXT, and BITCAST can both operand and result as
6583 /// integer types. This function implements the common transforms for all those
6585 /// @brief Implement the transforms common to CastInst with integer operands
6586 Instruction *InstCombiner::commonIntCastTransforms(CastInst &CI) {
6587 if (Instruction *Result = commonCastTransforms(CI))
6590 Value *Src = CI.getOperand(0);
6591 const Type *SrcTy = Src->getType();
6592 const Type *DestTy = CI.getType();
6593 uint32_t SrcBitSize = SrcTy->getPrimitiveSizeInBits();
6594 uint32_t DestBitSize = DestTy->getPrimitiveSizeInBits();
6596 // See if we can simplify any instructions used by the LHS whose sole
6597 // purpose is to compute bits we don't care about.
6598 APInt KnownZero(DestBitSize, 0), KnownOne(DestBitSize, 0);
6599 if (SimplifyDemandedBits(&CI, APInt::getAllOnesValue(DestBitSize),
6600 KnownZero, KnownOne))
6603 // If the source isn't an instruction or has more than one use then we
6604 // can't do anything more.
6605 Instruction *SrcI = dyn_cast<Instruction>(Src);
6606 if (!SrcI || !Src->hasOneUse())
6609 // Attempt to propagate the cast into the instruction for int->int casts.
6610 int NumCastsRemoved = 0;
6611 if (!isa<BitCastInst>(CI) &&
6612 CanEvaluateInDifferentType(SrcI, cast<IntegerType>(DestTy),
6613 CI.getOpcode(), NumCastsRemoved)) {
6614 // If this cast is a truncate, evaluting in a different type always
6615 // eliminates the cast, so it is always a win. If this is a zero-extension,
6616 // we need to do an AND to maintain the clear top-part of the computation,
6617 // so we require that the input have eliminated at least one cast. If this
6618 // is a sign extension, we insert two new casts (to do the extension) so we
6619 // require that two casts have been eliminated.
6621 switch (CI.getOpcode()) {
6623 // All the others use floating point so we shouldn't actually
6624 // get here because of the check above.
6625 assert(0 && "Unknown cast type");
6626 case Instruction::Trunc:
6629 case Instruction::ZExt:
6630 DoXForm = NumCastsRemoved >= 1;
6632 case Instruction::SExt:
6633 DoXForm = NumCastsRemoved >= 2;
6638 Value *Res = EvaluateInDifferentType(SrcI, DestTy,
6639 CI.getOpcode() == Instruction::SExt);
6640 assert(Res->getType() == DestTy);
6641 switch (CI.getOpcode()) {
6642 default: assert(0 && "Unknown cast type!");
6643 case Instruction::Trunc:
6644 case Instruction::BitCast:
6645 // Just replace this cast with the result.
6646 return ReplaceInstUsesWith(CI, Res);
6647 case Instruction::ZExt: {
6648 // We need to emit an AND to clear the high bits.
6649 assert(SrcBitSize < DestBitSize && "Not a zext?");
6650 Constant *C = ConstantInt::get(APInt::getLowBitsSet(DestBitSize,
6652 return BinaryOperator::createAnd(Res, C);
6654 case Instruction::SExt:
6655 // We need to emit a cast to truncate, then a cast to sext.
6656 return CastInst::create(Instruction::SExt,
6657 InsertCastBefore(Instruction::Trunc, Res, Src->getType(),
6663 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
6664 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
6666 switch (SrcI->getOpcode()) {
6667 case Instruction::Add:
6668 case Instruction::Mul:
6669 case Instruction::And:
6670 case Instruction::Or:
6671 case Instruction::Xor:
6672 // If we are discarding information, rewrite.
6673 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
6674 // Don't insert two casts if they cannot be eliminated. We allow
6675 // two casts to be inserted if the sizes are the same. This could
6676 // only be converting signedness, which is a noop.
6677 if (DestBitSize == SrcBitSize ||
6678 !ValueRequiresCast(CI.getOpcode(), Op1, DestTy,TD) ||
6679 !ValueRequiresCast(CI.getOpcode(), Op0, DestTy, TD)) {
6680 Instruction::CastOps opcode = CI.getOpcode();
6681 Value *Op0c = InsertOperandCastBefore(opcode, Op0, DestTy, SrcI);
6682 Value *Op1c = InsertOperandCastBefore(opcode, Op1, DestTy, SrcI);
6683 return BinaryOperator::create(
6684 cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
6688 // cast (xor bool X, true) to int --> xor (cast bool X to int), 1
6689 if (isa<ZExtInst>(CI) && SrcBitSize == 1 &&
6690 SrcI->getOpcode() == Instruction::Xor &&
6691 Op1 == ConstantInt::getTrue() &&
6692 (!Op0->hasOneUse() || !isa<CmpInst>(Op0))) {
6693 Value *New = InsertOperandCastBefore(Instruction::ZExt, Op0, DestTy, &CI);
6694 return BinaryOperator::createXor(New, ConstantInt::get(CI.getType(), 1));
6697 case Instruction::SDiv:
6698 case Instruction::UDiv:
6699 case Instruction::SRem:
6700 case Instruction::URem:
6701 // If we are just changing the sign, rewrite.
6702 if (DestBitSize == SrcBitSize) {
6703 // Don't insert two casts if they cannot be eliminated. We allow
6704 // two casts to be inserted if the sizes are the same. This could
6705 // only be converting signedness, which is a noop.
6706 if (!ValueRequiresCast(CI.getOpcode(), Op1, DestTy, TD) ||
6707 !ValueRequiresCast(CI.getOpcode(), Op0, DestTy, TD)) {
6708 Value *Op0c = InsertOperandCastBefore(Instruction::BitCast,
6710 Value *Op1c = InsertOperandCastBefore(Instruction::BitCast,
6712 return BinaryOperator::create(
6713 cast<BinaryOperator>(SrcI)->getOpcode(), Op0c, Op1c);
6718 case Instruction::Shl:
6719 // Allow changing the sign of the source operand. Do not allow
6720 // changing the size of the shift, UNLESS the shift amount is a
6721 // constant. We must not change variable sized shifts to a smaller
6722 // size, because it is undefined to shift more bits out than exist
6724 if (DestBitSize == SrcBitSize ||
6725 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
6726 Instruction::CastOps opcode = (DestBitSize == SrcBitSize ?
6727 Instruction::BitCast : Instruction::Trunc);
6728 Value *Op0c = InsertOperandCastBefore(opcode, Op0, DestTy, SrcI);
6729 Value *Op1c = InsertOperandCastBefore(opcode, Op1, DestTy, SrcI);
6730 return BinaryOperator::createShl(Op0c, Op1c);
6733 case Instruction::AShr:
6734 // If this is a signed shr, and if all bits shifted in are about to be
6735 // truncated off, turn it into an unsigned shr to allow greater
6737 if (DestBitSize < SrcBitSize &&
6738 isa<ConstantInt>(Op1)) {
6739 uint32_t ShiftAmt = cast<ConstantInt>(Op1)->getLimitedValue(SrcBitSize);
6740 if (SrcBitSize > ShiftAmt && SrcBitSize-ShiftAmt >= DestBitSize) {
6741 // Insert the new logical shift right.
6742 return BinaryOperator::createLShr(Op0, Op1);
6750 Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
6751 if (Instruction *Result = commonIntCastTransforms(CI))
6754 Value *Src = CI.getOperand(0);
6755 const Type *Ty = CI.getType();
6756 uint32_t DestBitWidth = Ty->getPrimitiveSizeInBits();
6757 uint32_t SrcBitWidth = cast<IntegerType>(Src->getType())->getBitWidth();
6759 if (Instruction *SrcI = dyn_cast<Instruction>(Src)) {
6760 switch (SrcI->getOpcode()) {
6762 case Instruction::LShr:
6763 // We can shrink lshr to something smaller if we know the bits shifted in
6764 // are already zeros.
6765 if (ConstantInt *ShAmtV = dyn_cast<ConstantInt>(SrcI->getOperand(1))) {
6766 uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
6768 // Get a mask for the bits shifting in.
6769 APInt Mask(APInt::getLowBitsSet(SrcBitWidth, ShAmt).shl(DestBitWidth));
6770 Value* SrcIOp0 = SrcI->getOperand(0);
6771 if (SrcI->hasOneUse() && MaskedValueIsZero(SrcIOp0, Mask)) {
6772 if (ShAmt >= DestBitWidth) // All zeros.
6773 return ReplaceInstUsesWith(CI, Constant::getNullValue(Ty));
6775 // Okay, we can shrink this. Truncate the input, then return a new
6777 Value *V1 = InsertCastBefore(Instruction::Trunc, SrcIOp0, Ty, CI);
6778 Value *V2 = InsertCastBefore(Instruction::Trunc, SrcI->getOperand(1),
6780 return BinaryOperator::createLShr(V1, V2);
6782 } else { // This is a variable shr.
6784 // Turn 'trunc (lshr X, Y) to bool' into '(X & (1 << Y)) != 0'. This is
6785 // more LLVM instructions, but allows '1 << Y' to be hoisted if
6786 // loop-invariant and CSE'd.
6787 if (CI.getType() == Type::Int1Ty && SrcI->hasOneUse()) {
6788 Value *One = ConstantInt::get(SrcI->getType(), 1);
6790 Value *V = InsertNewInstBefore(
6791 BinaryOperator::createShl(One, SrcI->getOperand(1),
6793 V = InsertNewInstBefore(BinaryOperator::createAnd(V,
6794 SrcI->getOperand(0),
6796 Value *Zero = Constant::getNullValue(V->getType());
6797 return new ICmpInst(ICmpInst::ICMP_NE, V, Zero);
6807 Instruction *InstCombiner::visitZExt(ZExtInst &CI) {
6808 // If one of the common conversion will work ..
6809 if (Instruction *Result = commonIntCastTransforms(CI))
6812 Value *Src = CI.getOperand(0);
6814 // If this is a cast of a cast
6815 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
6816 // If this is a TRUNC followed by a ZEXT then we are dealing with integral
6817 // types and if the sizes are just right we can convert this into a logical
6818 // 'and' which will be much cheaper than the pair of casts.
6819 if (isa<TruncInst>(CSrc)) {
6820 // Get the sizes of the types involved
6821 Value *A = CSrc->getOperand(0);
6822 uint32_t SrcSize = A->getType()->getPrimitiveSizeInBits();
6823 uint32_t MidSize = CSrc->getType()->getPrimitiveSizeInBits();
6824 uint32_t DstSize = CI.getType()->getPrimitiveSizeInBits();
6825 // If we're actually extending zero bits and the trunc is a no-op
6826 if (MidSize < DstSize && SrcSize == DstSize) {
6827 // Replace both of the casts with an And of the type mask.
6828 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize));
6829 Constant *AndConst = ConstantInt::get(AndValue);
6831 BinaryOperator::createAnd(CSrc->getOperand(0), AndConst);
6832 // Unfortunately, if the type changed, we need to cast it back.
6833 if (And->getType() != CI.getType()) {
6834 And->setName(CSrc->getName()+".mask");
6835 InsertNewInstBefore(And, CI);
6836 And = CastInst::createIntegerCast(And, CI.getType(), false/*ZExt*/);
6843 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) {
6844 // If we are just checking for a icmp eq of a single bit and zext'ing it
6845 // to an integer, then shift the bit to the appropriate place and then
6846 // cast to integer to avoid the comparison.
6847 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
6848 const APInt &Op1CV = Op1C->getValue();
6850 // zext (x <s 0) to i32 --> x>>u31 true if signbit set.
6851 // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear.
6852 if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
6853 (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())){
6854 Value *In = ICI->getOperand(0);
6855 Value *Sh = ConstantInt::get(In->getType(),
6856 In->getType()->getPrimitiveSizeInBits()-1);
6857 In = InsertNewInstBefore(BinaryOperator::createLShr(In, Sh,
6858 In->getName()+".lobit"),
6860 if (In->getType() != CI.getType())
6861 In = CastInst::createIntegerCast(In, CI.getType(),
6862 false/*ZExt*/, "tmp", &CI);
6864 if (ICI->getPredicate() == ICmpInst::ICMP_SGT) {
6865 Constant *One = ConstantInt::get(In->getType(), 1);
6866 In = InsertNewInstBefore(BinaryOperator::createXor(In, One,
6867 In->getName()+".not"),
6871 return ReplaceInstUsesWith(CI, In);
6876 // zext (X == 0) to i32 --> X^1 iff X has only the low bit set.
6877 // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
6878 // zext (X == 1) to i32 --> X iff X has only the low bit set.
6879 // zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set.
6880 // zext (X != 0) to i32 --> X iff X has only the low bit set.
6881 // zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set.
6882 // zext (X != 1) to i32 --> X^1 iff X has only the low bit set.
6883 // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set.
6884 if ((Op1CV == 0 || Op1CV.isPowerOf2()) &&
6885 // This only works for EQ and NE
6886 ICI->isEquality()) {
6887 // If Op1C some other power of two, convert:
6888 uint32_t BitWidth = Op1C->getType()->getBitWidth();
6889 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
6890 APInt TypeMask(APInt::getAllOnesValue(BitWidth));
6891 ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne);
6893 APInt KnownZeroMask(~KnownZero);
6894 if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1?
6895 bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE;
6896 if (Op1CV != 0 && (Op1CV != KnownZeroMask)) {
6897 // (X&4) == 2 --> false
6898 // (X&4) != 2 --> true
6899 Constant *Res = ConstantInt::get(Type::Int1Ty, isNE);
6900 Res = ConstantExpr::getZExt(Res, CI.getType());
6901 return ReplaceInstUsesWith(CI, Res);
6904 uint32_t ShiftAmt = KnownZeroMask.logBase2();
6905 Value *In = ICI->getOperand(0);
6907 // Perform a logical shr by shiftamt.
6908 // Insert the shift to put the result in the low bit.
6909 In = InsertNewInstBefore(
6910 BinaryOperator::createLShr(In,
6911 ConstantInt::get(In->getType(), ShiftAmt),
6912 In->getName()+".lobit"), CI);
6915 if ((Op1CV != 0) == isNE) { // Toggle the low bit.
6916 Constant *One = ConstantInt::get(In->getType(), 1);
6917 In = BinaryOperator::createXor(In, One, "tmp");
6918 InsertNewInstBefore(cast<Instruction>(In), CI);
6921 if (CI.getType() == In->getType())
6922 return ReplaceInstUsesWith(CI, In);
6924 return CastInst::createIntegerCast(In, CI.getType(), false/*ZExt*/);
6932 Instruction *InstCombiner::visitSExt(SExtInst &CI) {
6933 if (Instruction *I = commonIntCastTransforms(CI))
6936 Value *Src = CI.getOperand(0);
6938 // sext (x <s 0) -> ashr x, 31 -> all ones if signed
6939 // sext (x >s -1) -> ashr x, 31 -> all ones if not signed
6940 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) {
6941 // If we are just checking for a icmp eq of a single bit and zext'ing it
6942 // to an integer, then shift the bit to the appropriate place and then
6943 // cast to integer to avoid the comparison.
6944 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) {
6945 const APInt &Op1CV = Op1C->getValue();
6947 // sext (x <s 0) to i32 --> x>>s31 true if signbit set.
6948 // sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear.
6949 if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) ||
6950 (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())){
6951 Value *In = ICI->getOperand(0);
6952 Value *Sh = ConstantInt::get(In->getType(),
6953 In->getType()->getPrimitiveSizeInBits()-1);
6954 In = InsertNewInstBefore(BinaryOperator::createAShr(In, Sh,
6955 In->getName()+".lobit"),
6957 if (In->getType() != CI.getType())
6958 In = CastInst::createIntegerCast(In, CI.getType(),
6959 true/*SExt*/, "tmp", &CI);
6961 if (ICI->getPredicate() == ICmpInst::ICMP_SGT)
6962 In = InsertNewInstBefore(BinaryOperator::createNot(In,
6963 In->getName()+".not"), CI);
6965 return ReplaceInstUsesWith(CI, In);
6973 Instruction *InstCombiner::visitFPTrunc(CastInst &CI) {
6974 return commonCastTransforms(CI);
6977 Instruction *InstCombiner::visitFPExt(CastInst &CI) {
6978 return commonCastTransforms(CI);
6981 Instruction *InstCombiner::visitFPToUI(CastInst &CI) {
6982 return commonCastTransforms(CI);
6985 Instruction *InstCombiner::visitFPToSI(CastInst &CI) {
6986 return commonCastTransforms(CI);
6989 Instruction *InstCombiner::visitUIToFP(CastInst &CI) {
6990 return commonCastTransforms(CI);
6993 Instruction *InstCombiner::visitSIToFP(CastInst &CI) {
6994 return commonCastTransforms(CI);
6997 Instruction *InstCombiner::visitPtrToInt(CastInst &CI) {
6998 return commonPointerCastTransforms(CI);
7001 Instruction *InstCombiner::visitIntToPtr(CastInst &CI) {
7002 return commonCastTransforms(CI);
7005 Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
7006 // If the operands are integer typed then apply the integer transforms,
7007 // otherwise just apply the common ones.
7008 Value *Src = CI.getOperand(0);
7009 const Type *SrcTy = Src->getType();
7010 const Type *DestTy = CI.getType();
7012 if (SrcTy->isInteger() && DestTy->isInteger()) {
7013 if (Instruction *Result = commonIntCastTransforms(CI))
7015 } else if (isa<PointerType>(SrcTy)) {
7016 if (Instruction *I = commonPointerCastTransforms(CI))
7019 if (Instruction *Result = commonCastTransforms(CI))
7024 // Get rid of casts from one type to the same type. These are useless and can
7025 // be replaced by the operand.
7026 if (DestTy == Src->getType())
7027 return ReplaceInstUsesWith(CI, Src);
7029 if (const PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) {
7030 const PointerType *SrcPTy = cast<PointerType>(SrcTy);
7031 const Type *DstElTy = DstPTy->getElementType();
7032 const Type *SrcElTy = SrcPTy->getElementType();
7034 // If we are casting a malloc or alloca to a pointer to a type of the same
7035 // size, rewrite the allocation instruction to allocate the "right" type.
7036 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
7037 if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
7040 // If the source and destination are pointers, and this cast is equivalent
7041 // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep.
7042 // This can enhance SROA and other transforms that want type-safe pointers.
7043 Constant *ZeroUInt = Constant::getNullValue(Type::Int32Ty);
7044 unsigned NumZeros = 0;
7045 while (SrcElTy != DstElTy &&
7046 isa<CompositeType>(SrcElTy) && !isa<PointerType>(SrcElTy) &&
7047 SrcElTy->getNumContainedTypes() /* not "{}" */) {
7048 SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt);
7052 // If we found a path from the src to dest, create the getelementptr now.
7053 if (SrcElTy == DstElTy) {
7054 SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt);
7055 return new GetElementPtrInst(Src, &Idxs[0], Idxs.size());
7059 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) {
7060 if (SVI->hasOneUse()) {
7061 // Okay, we have (bitconvert (shuffle ..)). Check to see if this is
7062 // a bitconvert to a vector with the same # elts.
7063 if (isa<VectorType>(DestTy) &&
7064 cast<VectorType>(DestTy)->getNumElements() ==
7065 SVI->getType()->getNumElements()) {
7067 // If either of the operands is a cast from CI.getType(), then
7068 // evaluating the shuffle in the casted destination's type will allow
7069 // us to eliminate at least one cast.
7070 if (((Tmp = dyn_cast<CastInst>(SVI->getOperand(0))) &&
7071 Tmp->getOperand(0)->getType() == DestTy) ||
7072 ((Tmp = dyn_cast<CastInst>(SVI->getOperand(1))) &&
7073 Tmp->getOperand(0)->getType() == DestTy)) {
7074 Value *LHS = InsertOperandCastBefore(Instruction::BitCast,
7075 SVI->getOperand(0), DestTy, &CI);
7076 Value *RHS = InsertOperandCastBefore(Instruction::BitCast,
7077 SVI->getOperand(1), DestTy, &CI);
7078 // Return a new shuffle vector. Use the same element ID's, as we
7079 // know the vector types match #elts.
7080 return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2));
7088 /// GetSelectFoldableOperands - We want to turn code that looks like this:
7090 /// %D = select %cond, %C, %A
7092 /// %C = select %cond, %B, 0
7095 /// Assuming that the specified instruction is an operand to the select, return
7096 /// a bitmask indicating which operands of this instruction are foldable if they
7097 /// equal the other incoming value of the select.
7099 static unsigned GetSelectFoldableOperands(Instruction *I) {
7100 switch (I->getOpcode()) {
7101 case Instruction::Add:
7102 case Instruction::Mul:
7103 case Instruction::And:
7104 case Instruction::Or:
7105 case Instruction::Xor:
7106 return 3; // Can fold through either operand.
7107 case Instruction::Sub: // Can only fold on the amount subtracted.
7108 case Instruction::Shl: // Can only fold on the shift amount.
7109 case Instruction::LShr:
7110 case Instruction::AShr:
7113 return 0; // Cannot fold
7117 /// GetSelectFoldableConstant - For the same transformation as the previous
7118 /// function, return the identity constant that goes into the select.
7119 static Constant *GetSelectFoldableConstant(Instruction *I) {
7120 switch (I->getOpcode()) {
7121 default: assert(0 && "This cannot happen!"); abort();
7122 case Instruction::Add:
7123 case Instruction::Sub:
7124 case Instruction::Or:
7125 case Instruction::Xor:
7126 case Instruction::Shl:
7127 case Instruction::LShr:
7128 case Instruction::AShr:
7129 return Constant::getNullValue(I->getType());
7130 case Instruction::And:
7131 return Constant::getAllOnesValue(I->getType());
7132 case Instruction::Mul:
7133 return ConstantInt::get(I->getType(), 1);
7137 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
7138 /// have the same opcode and only one use each. Try to simplify this.
7139 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
7141 if (TI->getNumOperands() == 1) {
7142 // If this is a non-volatile load or a cast from the same type,
7145 if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
7148 return 0; // unknown unary op.
7151 // Fold this by inserting a select from the input values.
7152 SelectInst *NewSI = new SelectInst(SI.getCondition(), TI->getOperand(0),
7153 FI->getOperand(0), SI.getName()+".v");
7154 InsertNewInstBefore(NewSI, SI);
7155 return CastInst::create(Instruction::CastOps(TI->getOpcode()), NewSI,
7159 // Only handle binary operators here.
7160 if (!isa<BinaryOperator>(TI))
7163 // Figure out if the operations have any operands in common.
7164 Value *MatchOp, *OtherOpT, *OtherOpF;
7166 if (TI->getOperand(0) == FI->getOperand(0)) {
7167 MatchOp = TI->getOperand(0);
7168 OtherOpT = TI->getOperand(1);
7169 OtherOpF = FI->getOperand(1);
7170 MatchIsOpZero = true;
7171 } else if (TI->getOperand(1) == FI->getOperand(1)) {
7172 MatchOp = TI->getOperand(1);
7173 OtherOpT = TI->getOperand(0);
7174 OtherOpF = FI->getOperand(0);
7175 MatchIsOpZero = false;
7176 } else if (!TI->isCommutative()) {
7178 } else if (TI->getOperand(0) == FI->getOperand(1)) {
7179 MatchOp = TI->getOperand(0);
7180 OtherOpT = TI->getOperand(1);
7181 OtherOpF = FI->getOperand(0);
7182 MatchIsOpZero = true;
7183 } else if (TI->getOperand(1) == FI->getOperand(0)) {
7184 MatchOp = TI->getOperand(1);
7185 OtherOpT = TI->getOperand(0);
7186 OtherOpF = FI->getOperand(1);
7187 MatchIsOpZero = true;
7192 // If we reach here, they do have operations in common.
7193 SelectInst *NewSI = new SelectInst(SI.getCondition(), OtherOpT,
7194 OtherOpF, SI.getName()+".v");
7195 InsertNewInstBefore(NewSI, SI);
7197 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
7199 return BinaryOperator::create(BO->getOpcode(), MatchOp, NewSI);
7201 return BinaryOperator::create(BO->getOpcode(), NewSI, MatchOp);
7203 assert(0 && "Shouldn't get here");
7207 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
7208 Value *CondVal = SI.getCondition();
7209 Value *TrueVal = SI.getTrueValue();
7210 Value *FalseVal = SI.getFalseValue();
7212 // select true, X, Y -> X
7213 // select false, X, Y -> Y
7214 if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
7215 return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
7217 // select C, X, X -> X
7218 if (TrueVal == FalseVal)
7219 return ReplaceInstUsesWith(SI, TrueVal);
7221 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
7222 return ReplaceInstUsesWith(SI, FalseVal);
7223 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
7224 return ReplaceInstUsesWith(SI, TrueVal);
7225 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
7226 if (isa<Constant>(TrueVal))
7227 return ReplaceInstUsesWith(SI, TrueVal);
7229 return ReplaceInstUsesWith(SI, FalseVal);
7232 if (SI.getType() == Type::Int1Ty) {
7233 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
7234 if (C->getZExtValue()) {
7235 // Change: A = select B, true, C --> A = or B, C
7236 return BinaryOperator::createOr(CondVal, FalseVal);
7238 // Change: A = select B, false, C --> A = and !B, C
7240 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
7241 "not."+CondVal->getName()), SI);
7242 return BinaryOperator::createAnd(NotCond, FalseVal);
7244 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
7245 if (C->getZExtValue() == false) {
7246 // Change: A = select B, C, false --> A = and B, C
7247 return BinaryOperator::createAnd(CondVal, TrueVal);
7249 // Change: A = select B, C, true --> A = or !B, C
7251 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
7252 "not."+CondVal->getName()), SI);
7253 return BinaryOperator::createOr(NotCond, TrueVal);
7258 // Selecting between two integer constants?
7259 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
7260 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
7261 // select C, 1, 0 -> zext C to int
7262 if (FalseValC->isZero() && TrueValC->getValue() == 1) {
7263 return CastInst::create(Instruction::ZExt, CondVal, SI.getType());
7264 } else if (TrueValC->isZero() && FalseValC->getValue() == 1) {
7265 // select C, 0, 1 -> zext !C to int
7267 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
7268 "not."+CondVal->getName()), SI);
7269 return CastInst::create(Instruction::ZExt, NotCond, SI.getType());
7272 // FIXME: Turn select 0/-1 and -1/0 into sext from condition!
7274 if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
7276 // (x <s 0) ? -1 : 0 -> ashr x, 31
7277 if (TrueValC->isAllOnesValue() && FalseValC->isZero())
7278 if (ConstantInt *CmpCst = dyn_cast<ConstantInt>(IC->getOperand(1))) {
7279 if (IC->getPredicate() == ICmpInst::ICMP_SLT && CmpCst->isZero()) {
7280 // The comparison constant and the result are not neccessarily the
7281 // same width. Make an all-ones value by inserting a AShr.
7282 Value *X = IC->getOperand(0);
7283 uint32_t Bits = X->getType()->getPrimitiveSizeInBits();
7284 Constant *ShAmt = ConstantInt::get(X->getType(), Bits-1);
7285 Instruction *SRA = BinaryOperator::create(Instruction::AShr, X,
7287 InsertNewInstBefore(SRA, SI);
7289 // Finally, convert to the type of the select RHS. We figure out
7290 // if this requires a SExt, Trunc or BitCast based on the sizes.
7291 Instruction::CastOps opc = Instruction::BitCast;
7292 uint32_t SRASize = SRA->getType()->getPrimitiveSizeInBits();
7293 uint32_t SISize = SI.getType()->getPrimitiveSizeInBits();
7294 if (SRASize < SISize)
7295 opc = Instruction::SExt;
7296 else if (SRASize > SISize)
7297 opc = Instruction::Trunc;
7298 return CastInst::create(opc, SRA, SI.getType());
7303 // If one of the constants is zero (we know they can't both be) and we
7304 // have an icmp instruction with zero, and we have an 'and' with the
7305 // non-constant value, eliminate this whole mess. This corresponds to
7306 // cases like this: ((X & 27) ? 27 : 0)
7307 if (TrueValC->isZero() || FalseValC->isZero())
7308 if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
7309 cast<Constant>(IC->getOperand(1))->isNullValue())
7310 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
7311 if (ICA->getOpcode() == Instruction::And &&
7312 isa<ConstantInt>(ICA->getOperand(1)) &&
7313 (ICA->getOperand(1) == TrueValC ||
7314 ICA->getOperand(1) == FalseValC) &&
7315 isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
7316 // Okay, now we know that everything is set up, we just don't
7317 // know whether we have a icmp_ne or icmp_eq and whether the
7318 // true or false val is the zero.
7319 bool ShouldNotVal = !TrueValC->isZero();
7320 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
7323 V = InsertNewInstBefore(BinaryOperator::create(
7324 Instruction::Xor, V, ICA->getOperand(1)), SI);
7325 return ReplaceInstUsesWith(SI, V);
7330 // See if we are selecting two values based on a comparison of the two values.
7331 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
7332 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
7333 // Transform (X == Y) ? X : Y -> Y
7334 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ)
7335 return ReplaceInstUsesWith(SI, FalseVal);
7336 // Transform (X != Y) ? X : Y -> X
7337 if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
7338 return ReplaceInstUsesWith(SI, TrueVal);
7339 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
7341 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
7342 // Transform (X == Y) ? Y : X -> X
7343 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ)
7344 return ReplaceInstUsesWith(SI, FalseVal);
7345 // Transform (X != Y) ? Y : X -> Y
7346 if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
7347 return ReplaceInstUsesWith(SI, TrueVal);
7348 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
7352 // See if we are selecting two values based on a comparison of the two values.
7353 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal)) {
7354 if (ICI->getOperand(0) == TrueVal && ICI->getOperand(1) == FalseVal) {
7355 // Transform (X == Y) ? X : Y -> Y
7356 if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
7357 return ReplaceInstUsesWith(SI, FalseVal);
7358 // Transform (X != Y) ? X : Y -> X
7359 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
7360 return ReplaceInstUsesWith(SI, TrueVal);
7361 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
7363 } else if (ICI->getOperand(0) == FalseVal && ICI->getOperand(1) == TrueVal){
7364 // Transform (X == Y) ? Y : X -> X
7365 if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
7366 return ReplaceInstUsesWith(SI, FalseVal);
7367 // Transform (X != Y) ? Y : X -> Y
7368 if (ICI->getPredicate() == ICmpInst::ICMP_NE)
7369 return ReplaceInstUsesWith(SI, TrueVal);
7370 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
7374 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
7375 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
7376 if (TI->hasOneUse() && FI->hasOneUse()) {
7377 Instruction *AddOp = 0, *SubOp = 0;
7379 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
7380 if (TI->getOpcode() == FI->getOpcode())
7381 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
7384 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
7385 // even legal for FP.
7386 if (TI->getOpcode() == Instruction::Sub &&
7387 FI->getOpcode() == Instruction::Add) {
7388 AddOp = FI; SubOp = TI;
7389 } else if (FI->getOpcode() == Instruction::Sub &&
7390 TI->getOpcode() == Instruction::Add) {
7391 AddOp = TI; SubOp = FI;
7395 Value *OtherAddOp = 0;
7396 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
7397 OtherAddOp = AddOp->getOperand(1);
7398 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
7399 OtherAddOp = AddOp->getOperand(0);
7403 // So at this point we know we have (Y -> OtherAddOp):
7404 // select C, (add X, Y), (sub X, Z)
7405 Value *NegVal; // Compute -Z
7406 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
7407 NegVal = ConstantExpr::getNeg(C);
7409 NegVal = InsertNewInstBefore(
7410 BinaryOperator::createNeg(SubOp->getOperand(1), "tmp"), SI);
7413 Value *NewTrueOp = OtherAddOp;
7414 Value *NewFalseOp = NegVal;
7416 std::swap(NewTrueOp, NewFalseOp);
7417 Instruction *NewSel =
7418 new SelectInst(CondVal, NewTrueOp,NewFalseOp,SI.getName()+".p");
7420 NewSel = InsertNewInstBefore(NewSel, SI);
7421 return BinaryOperator::createAdd(SubOp->getOperand(0), NewSel);
7426 // See if we can fold the select into one of our operands.
7427 if (SI.getType()->isInteger()) {
7428 // See the comment above GetSelectFoldableOperands for a description of the
7429 // transformation we are doing here.
7430 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
7431 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
7432 !isa<Constant>(FalseVal))
7433 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
7434 unsigned OpToFold = 0;
7435 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
7437 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
7442 Constant *C = GetSelectFoldableConstant(TVI);
7443 Instruction *NewSel =
7444 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C);
7445 InsertNewInstBefore(NewSel, SI);
7446 NewSel->takeName(TVI);
7447 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
7448 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
7450 assert(0 && "Unknown instruction!!");
7455 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
7456 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
7457 !isa<Constant>(TrueVal))
7458 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
7459 unsigned OpToFold = 0;
7460 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
7462 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
7467 Constant *C = GetSelectFoldableConstant(FVI);
7468 Instruction *NewSel =
7469 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold));
7470 InsertNewInstBefore(NewSel, SI);
7471 NewSel->takeName(FVI);
7472 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
7473 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
7475 assert(0 && "Unknown instruction!!");
7480 if (BinaryOperator::isNot(CondVal)) {
7481 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
7482 SI.setOperand(1, FalseVal);
7483 SI.setOperand(2, TrueVal);
7490 /// GetKnownAlignment - If the specified pointer has an alignment that we can
7491 /// determine, return it, otherwise return 0.
7492 static unsigned GetKnownAlignment(Value *V, TargetData *TD) {
7493 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
7494 unsigned Align = GV->getAlignment();
7495 if (Align == 0 && TD)
7496 Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
7498 } else if (AllocationInst *AI = dyn_cast<AllocationInst>(V)) {
7499 unsigned Align = AI->getAlignment();
7500 if (Align == 0 && TD) {
7501 if (isa<AllocaInst>(AI))
7502 Align = TD->getPrefTypeAlignment(AI->getType()->getElementType());
7503 else if (isa<MallocInst>(AI)) {
7504 // Malloc returns maximally aligned memory.
7505 Align = TD->getABITypeAlignment(AI->getType()->getElementType());
7508 (unsigned)TD->getABITypeAlignment(Type::DoubleTy));
7511 (unsigned)TD->getABITypeAlignment(Type::Int64Ty));
7515 } else if (isa<BitCastInst>(V) ||
7516 (isa<ConstantExpr>(V) &&
7517 cast<ConstantExpr>(V)->getOpcode() == Instruction::BitCast)) {
7518 User *CI = cast<User>(V);
7519 if (isa<PointerType>(CI->getOperand(0)->getType()))
7520 return GetKnownAlignment(CI->getOperand(0), TD);
7522 } else if (User *GEPI = dyn_castGetElementPtr(V)) {
7523 unsigned BaseAlignment = GetKnownAlignment(GEPI->getOperand(0), TD);
7524 if (BaseAlignment == 0) return 0;
7526 // If all indexes are zero, it is just the alignment of the base pointer.
7527 bool AllZeroOperands = true;
7528 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
7529 if (!isa<Constant>(GEPI->getOperand(i)) ||
7530 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
7531 AllZeroOperands = false;
7534 if (AllZeroOperands)
7535 return BaseAlignment;
7537 // Otherwise, if the base alignment is >= the alignment we expect for the
7538 // base pointer type, then we know that the resultant pointer is aligned at
7539 // least as much as its type requires.
7542 const Type *BasePtrTy = GEPI->getOperand(0)->getType();
7543 const PointerType *PtrTy = cast<PointerType>(BasePtrTy);
7544 unsigned Align = TD->getABITypeAlignment(PtrTy->getElementType());
7545 if (Align <= BaseAlignment) {
7546 const Type *GEPTy = GEPI->getType();
7547 const PointerType *GEPPtrTy = cast<PointerType>(GEPTy);
7548 Align = std::min(Align, (unsigned)
7549 TD->getABITypeAlignment(GEPPtrTy->getElementType()));
7558 /// visitCallInst - CallInst simplification. This mostly only handles folding
7559 /// of intrinsic instructions. For normal calls, it allows visitCallSite to do
7560 /// the heavy lifting.
7562 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
7563 IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
7564 if (!II) return visitCallSite(&CI);
7566 // Intrinsics cannot occur in an invoke, so handle them here instead of in
7568 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(II)) {
7569 bool Changed = false;
7571 // memmove/cpy/set of zero bytes is a noop.
7572 if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
7573 if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
7575 if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
7576 if (CI->getZExtValue() == 1) {
7577 // Replace the instruction with just byte operations. We would
7578 // transform other cases to loads/stores, but we don't know if
7579 // alignment is sufficient.
7583 // If we have a memmove and the source operation is a constant global,
7584 // then the source and dest pointers can't alias, so we can change this
7585 // into a call to memcpy.
7586 if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(II)) {
7587 if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
7588 if (GVSrc->isConstant()) {
7589 Module *M = CI.getParent()->getParent()->getParent();
7591 if (CI.getCalledFunction()->getFunctionType()->getParamType(2) ==
7593 Name = "llvm.memcpy.i32";
7595 Name = "llvm.memcpy.i64";
7596 Constant *MemCpy = M->getOrInsertFunction(Name,
7597 CI.getCalledFunction()->getFunctionType());
7598 CI.setOperand(0, MemCpy);
7603 // If we can determine a pointer alignment that is bigger than currently
7604 // set, update the alignment.
7605 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
7606 unsigned Alignment1 = GetKnownAlignment(MI->getOperand(1), TD);
7607 unsigned Alignment2 = GetKnownAlignment(MI->getOperand(2), TD);
7608 unsigned Align = std::min(Alignment1, Alignment2);
7609 if (MI->getAlignment()->getZExtValue() < Align) {
7610 MI->setAlignment(ConstantInt::get(Type::Int32Ty, Align));
7613 } else if (isa<MemSetInst>(MI)) {
7614 unsigned Alignment = GetKnownAlignment(MI->getDest(), TD);
7615 if (MI->getAlignment()->getZExtValue() < Alignment) {
7616 MI->setAlignment(ConstantInt::get(Type::Int32Ty, Alignment));
7621 if (Changed) return II;
7623 switch (II->getIntrinsicID()) {
7625 case Intrinsic::ppc_altivec_lvx:
7626 case Intrinsic::ppc_altivec_lvxl:
7627 case Intrinsic::x86_sse_loadu_ps:
7628 case Intrinsic::x86_sse2_loadu_pd:
7629 case Intrinsic::x86_sse2_loadu_dq:
7630 // Turn PPC lvx -> load if the pointer is known aligned.
7631 // Turn X86 loadups -> load if the pointer is known aligned.
7632 if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
7633 Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(1),
7634 PointerType::get(II->getType()), CI);
7635 return new LoadInst(Ptr);
7638 case Intrinsic::ppc_altivec_stvx:
7639 case Intrinsic::ppc_altivec_stvxl:
7640 // Turn stvx -> store if the pointer is known aligned.
7641 if (GetKnownAlignment(II->getOperand(2), TD) >= 16) {
7642 const Type *OpPtrTy = PointerType::get(II->getOperand(1)->getType());
7643 Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(2),
7645 return new StoreInst(II->getOperand(1), Ptr);
7648 case Intrinsic::x86_sse_storeu_ps:
7649 case Intrinsic::x86_sse2_storeu_pd:
7650 case Intrinsic::x86_sse2_storeu_dq:
7651 case Intrinsic::x86_sse2_storel_dq:
7652 // Turn X86 storeu -> store if the pointer is known aligned.
7653 if (GetKnownAlignment(II->getOperand(1), TD) >= 16) {
7654 const Type *OpPtrTy = PointerType::get(II->getOperand(2)->getType());
7655 Value *Ptr = InsertCastBefore(Instruction::BitCast, II->getOperand(1),
7657 return new StoreInst(II->getOperand(2), Ptr);
7661 case Intrinsic::x86_sse_cvttss2si: {
7662 // These intrinsics only demands the 0th element of its input vector. If
7663 // we can simplify the input based on that, do so now.
7665 if (Value *V = SimplifyDemandedVectorElts(II->getOperand(1), 1,
7667 II->setOperand(1, V);
7673 case Intrinsic::ppc_altivec_vperm:
7674 // Turn vperm(V1,V2,mask) -> shuffle(V1,V2,mask) if mask is a constant.
7675 if (ConstantVector *Mask = dyn_cast<ConstantVector>(II->getOperand(3))) {
7676 assert(Mask->getNumOperands() == 16 && "Bad type for intrinsic!");
7678 // Check that all of the elements are integer constants or undefs.
7679 bool AllEltsOk = true;
7680 for (unsigned i = 0; i != 16; ++i) {
7681 if (!isa<ConstantInt>(Mask->getOperand(i)) &&
7682 !isa<UndefValue>(Mask->getOperand(i))) {
7689 // Cast the input vectors to byte vectors.
7690 Value *Op0 = InsertCastBefore(Instruction::BitCast,
7691 II->getOperand(1), Mask->getType(), CI);
7692 Value *Op1 = InsertCastBefore(Instruction::BitCast,
7693 II->getOperand(2), Mask->getType(), CI);
7694 Value *Result = UndefValue::get(Op0->getType());
7696 // Only extract each element once.
7697 Value *ExtractedElts[32];
7698 memset(ExtractedElts, 0, sizeof(ExtractedElts));
7700 for (unsigned i = 0; i != 16; ++i) {
7701 if (isa<UndefValue>(Mask->getOperand(i)))
7703 unsigned Idx=cast<ConstantInt>(Mask->getOperand(i))->getZExtValue();
7704 Idx &= 31; // Match the hardware behavior.
7706 if (ExtractedElts[Idx] == 0) {
7708 new ExtractElementInst(Idx < 16 ? Op0 : Op1, Idx&15, "tmp");
7709 InsertNewInstBefore(Elt, CI);
7710 ExtractedElts[Idx] = Elt;
7713 // Insert this value into the result vector.
7714 Result = new InsertElementInst(Result, ExtractedElts[Idx], i,"tmp");
7715 InsertNewInstBefore(cast<Instruction>(Result), CI);
7717 return CastInst::create(Instruction::BitCast, Result, CI.getType());
7722 case Intrinsic::stackrestore: {
7723 // If the save is right next to the restore, remove the restore. This can
7724 // happen when variable allocas are DCE'd.
7725 if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getOperand(1))) {
7726 if (SS->getIntrinsicID() == Intrinsic::stacksave) {
7727 BasicBlock::iterator BI = SS;
7729 return EraseInstFromFunction(CI);
7733 // If the stack restore is in a return/unwind block and if there are no
7734 // allocas or calls between the restore and the return, nuke the restore.
7735 TerminatorInst *TI = II->getParent()->getTerminator();
7736 if (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)) {
7737 BasicBlock::iterator BI = II;
7738 bool CannotRemove = false;
7739 for (++BI; &*BI != TI; ++BI) {
7740 if (isa<AllocaInst>(BI) ||
7741 (isa<CallInst>(BI) && !isa<IntrinsicInst>(BI))) {
7742 CannotRemove = true;
7747 return EraseInstFromFunction(CI);
7754 return visitCallSite(II);
7757 // InvokeInst simplification
7759 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
7760 return visitCallSite(&II);
7763 // visitCallSite - Improvements for call and invoke instructions.
7765 Instruction *InstCombiner::visitCallSite(CallSite CS) {
7766 bool Changed = false;
7768 // If the callee is a constexpr cast of a function, attempt to move the cast
7769 // to the arguments of the call/invoke.
7770 if (transformConstExprCastCall(CS)) return 0;
7772 Value *Callee = CS.getCalledValue();
7774 if (Function *CalleeF = dyn_cast<Function>(Callee))
7775 if (CalleeF->getCallingConv() != CS.getCallingConv()) {
7776 Instruction *OldCall = CS.getInstruction();
7777 // If the call and callee calling conventions don't match, this call must
7778 // be unreachable, as the call is undefined.
7779 new StoreInst(ConstantInt::getTrue(),
7780 UndefValue::get(PointerType::get(Type::Int1Ty)), OldCall);
7781 if (!OldCall->use_empty())
7782 OldCall->replaceAllUsesWith(UndefValue::get(OldCall->getType()));
7783 if (isa<CallInst>(OldCall)) // Not worth removing an invoke here.
7784 return EraseInstFromFunction(*OldCall);
7788 if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
7789 // This instruction is not reachable, just remove it. We insert a store to
7790 // undef so that we know that this code is not reachable, despite the fact
7791 // that we can't modify the CFG here.
7792 new StoreInst(ConstantInt::getTrue(),
7793 UndefValue::get(PointerType::get(Type::Int1Ty)),
7794 CS.getInstruction());
7796 if (!CS.getInstruction()->use_empty())
7797 CS.getInstruction()->
7798 replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
7800 if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
7801 // Don't break the CFG, insert a dummy cond branch.
7802 new BranchInst(II->getNormalDest(), II->getUnwindDest(),
7803 ConstantInt::getTrue(), II);
7805 return EraseInstFromFunction(*CS.getInstruction());
7808 const PointerType *PTy = cast<PointerType>(Callee->getType());
7809 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
7810 if (FTy->isVarArg()) {
7811 // See if we can optimize any arguments passed through the varargs area of
7813 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
7814 E = CS.arg_end(); I != E; ++I)
7815 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
7816 // If this cast does not effect the value passed through the varargs
7817 // area, we can eliminate the use of the cast.
7818 Value *Op = CI->getOperand(0);
7819 if (CI->isLosslessCast()) {
7826 return Changed ? CS.getInstruction() : 0;
7829 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
7830 // attempt to move the cast to the arguments of the call/invoke.
7832 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
7833 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
7834 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
7835 if (CE->getOpcode() != Instruction::BitCast ||
7836 !isa<Function>(CE->getOperand(0)))
7838 Function *Callee = cast<Function>(CE->getOperand(0));
7839 Instruction *Caller = CS.getInstruction();
7841 // Okay, this is a cast from a function to a different type. Unless doing so
7842 // would cause a type conversion of one of our arguments, change this call to
7843 // be a direct call with arguments casted to the appropriate types.
7845 const FunctionType *FT = Callee->getFunctionType();
7846 const Type *OldRetTy = Caller->getType();
7848 const FunctionType *ActualFT =
7849 cast<FunctionType>(cast<PointerType>(CE->getType())->getElementType());
7851 // If the parameter attributes don't match up, don't do the xform. We don't
7852 // want to lose an sret attribute or something.
7853 if (FT->getParamAttrs() != ActualFT->getParamAttrs())
7856 // Check to see if we are changing the return type...
7857 if (OldRetTy != FT->getReturnType()) {
7858 if (Callee->isDeclaration() && !Caller->use_empty() &&
7859 // Conversion is ok if changing from pointer to int of same size.
7860 !(isa<PointerType>(FT->getReturnType()) &&
7861 TD->getIntPtrType() == OldRetTy))
7862 return false; // Cannot transform this return value.
7864 // If the callsite is an invoke instruction, and the return value is used by
7865 // a PHI node in a successor, we cannot change the return type of the call
7866 // because there is no place to put the cast instruction (without breaking
7867 // the critical edge). Bail out in this case.
7868 if (!Caller->use_empty())
7869 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
7870 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
7872 if (PHINode *PN = dyn_cast<PHINode>(*UI))
7873 if (PN->getParent() == II->getNormalDest() ||
7874 PN->getParent() == II->getUnwindDest())
7878 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
7879 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
7881 CallSite::arg_iterator AI = CS.arg_begin();
7882 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
7883 const Type *ParamTy = FT->getParamType(i);
7884 const Type *ActTy = (*AI)->getType();
7885 ConstantInt *c = dyn_cast<ConstantInt>(*AI);
7886 //Some conversions are safe even if we do not have a body.
7887 //Either we can cast directly, or we can upconvert the argument
7888 bool isConvertible = ActTy == ParamTy ||
7889 (isa<PointerType>(ParamTy) && isa<PointerType>(ActTy)) ||
7890 (ParamTy->isInteger() && ActTy->isInteger() &&
7891 ParamTy->getPrimitiveSizeInBits() >= ActTy->getPrimitiveSizeInBits()) ||
7892 (c && ParamTy->getPrimitiveSizeInBits() >= ActTy->getPrimitiveSizeInBits()
7893 && c->getValue().isStrictlyPositive());
7894 if (Callee->isDeclaration() && !isConvertible) return false;
7896 // Most other conversions can be done if we have a body, even if these
7897 // lose information, e.g. int->short.
7898 // Some conversions cannot be done at all, e.g. float to pointer.
7899 // Logic here parallels CastInst::getCastOpcode (the design there
7900 // requires legality checks like this be done before calling it).
7901 if (ParamTy->isInteger()) {
7902 if (const VectorType *VActTy = dyn_cast<VectorType>(ActTy)) {
7903 if (VActTy->getBitWidth() != ParamTy->getPrimitiveSizeInBits())
7906 if (!ActTy->isInteger() && !ActTy->isFloatingPoint() &&
7907 !isa<PointerType>(ActTy))
7909 } else if (ParamTy->isFloatingPoint()) {
7910 if (const VectorType *VActTy = dyn_cast<VectorType>(ActTy)) {
7911 if (VActTy->getBitWidth() != ParamTy->getPrimitiveSizeInBits())
7914 if (!ActTy->isInteger() && !ActTy->isFloatingPoint())
7916 } else if (const VectorType *VParamTy = dyn_cast<VectorType>(ParamTy)) {
7917 if (const VectorType *VActTy = dyn_cast<VectorType>(ActTy)) {
7918 if (VActTy->getBitWidth() != VParamTy->getBitWidth())
7921 if (VParamTy->getBitWidth() != ActTy->getPrimitiveSizeInBits())
7923 } else if (isa<PointerType>(ParamTy)) {
7924 if (!ActTy->isInteger() && !isa<PointerType>(ActTy))
7931 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
7932 Callee->isDeclaration())
7933 return false; // Do not delete arguments unless we have a function body...
7935 // Okay, we decided that this is a safe thing to do: go ahead and start
7936 // inserting cast instructions as necessary...
7937 std::vector<Value*> Args;
7938 Args.reserve(NumActualArgs);
7940 AI = CS.arg_begin();
7941 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
7942 const Type *ParamTy = FT->getParamType(i);
7943 if ((*AI)->getType() == ParamTy) {
7944 Args.push_back(*AI);
7946 Instruction::CastOps opcode = CastInst::getCastOpcode(*AI,
7947 false, ParamTy, false);
7948 CastInst *NewCast = CastInst::create(opcode, *AI, ParamTy, "tmp");
7949 Args.push_back(InsertNewInstBefore(NewCast, *Caller));
7953 // If the function takes more arguments than the call was taking, add them
7955 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
7956 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
7958 // If we are removing arguments to the function, emit an obnoxious warning...
7959 if (FT->getNumParams() < NumActualArgs)
7960 if (!FT->isVarArg()) {
7961 cerr << "WARNING: While resolving call to function '"
7962 << Callee->getName() << "' arguments were dropped!\n";
7964 // Add all of the arguments in their promoted form to the arg list...
7965 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
7966 const Type *PTy = getPromotedType((*AI)->getType());
7967 if (PTy != (*AI)->getType()) {
7968 // Must promote to pass through va_arg area!
7969 Instruction::CastOps opcode = CastInst::getCastOpcode(*AI, false,
7971 Instruction *Cast = CastInst::create(opcode, *AI, PTy, "tmp");
7972 InsertNewInstBefore(Cast, *Caller);
7973 Args.push_back(Cast);
7975 Args.push_back(*AI);
7980 if (FT->getReturnType() == Type::VoidTy)
7981 Caller->setName(""); // Void type should not have a name.
7984 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
7985 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
7986 &Args[0], Args.size(), Caller->getName(), Caller);
7987 cast<InvokeInst>(NC)->setCallingConv(II->getCallingConv());
7989 NC = new CallInst(Callee, Args.begin(), Args.end(),
7990 Caller->getName(), Caller);
7991 if (cast<CallInst>(Caller)->isTailCall())
7992 cast<CallInst>(NC)->setTailCall();
7993 cast<CallInst>(NC)->setCallingConv(cast<CallInst>(Caller)->getCallingConv());
7996 // Insert a cast of the return type as necessary.
7998 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
7999 if (NV->getType() != Type::VoidTy) {
8000 const Type *CallerTy = Caller->getType();
8001 Instruction::CastOps opcode = CastInst::getCastOpcode(NC, false,
8003 NV = NC = CastInst::create(opcode, NC, CallerTy, "tmp");
8005 // If this is an invoke instruction, we should insert it after the first
8006 // non-phi, instruction in the normal successor block.
8007 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
8008 BasicBlock::iterator I = II->getNormalDest()->begin();
8009 while (isa<PHINode>(I)) ++I;
8010 InsertNewInstBefore(NC, *I);
8012 // Otherwise, it's a call, just insert cast right after the call instr
8013 InsertNewInstBefore(NC, *Caller);
8015 AddUsersToWorkList(*Caller);
8017 NV = UndefValue::get(Caller->getType());
8021 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
8022 Caller->replaceAllUsesWith(NV);
8023 Caller->eraseFromParent();
8024 RemoveFromWorkList(Caller);
8028 /// FoldPHIArgBinOpIntoPHI - If we have something like phi [add (a,b), add(c,d)]
8029 /// and if a/b/c/d and the add's all have a single use, turn this into two phi's
8030 /// and a single binop.
8031 Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
8032 Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
8033 assert(isa<BinaryOperator>(FirstInst) || isa<GetElementPtrInst>(FirstInst) ||
8034 isa<CmpInst>(FirstInst));
8035 unsigned Opc = FirstInst->getOpcode();
8036 Value *LHSVal = FirstInst->getOperand(0);
8037 Value *RHSVal = FirstInst->getOperand(1);
8039 const Type *LHSType = LHSVal->getType();
8040 const Type *RHSType = RHSVal->getType();
8042 // Scan to see if all operands are the same opcode, all have one use, and all
8043 // kill their operands (i.e. the operands have one use).
8044 for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) {
8045 Instruction *I = dyn_cast<Instruction>(PN.getIncomingValue(i));
8046 if (!I || I->getOpcode() != Opc || !I->hasOneUse() ||
8047 // Verify type of the LHS matches so we don't fold cmp's of different
8048 // types or GEP's with different index types.
8049 I->getOperand(0)->getType() != LHSType ||
8050 I->getOperand(1)->getType() != RHSType)
8053 // If they are CmpInst instructions, check their predicates
8054 if (Opc == Instruction::ICmp || Opc == Instruction::FCmp)
8055 if (cast<CmpInst>(I)->getPredicate() !=
8056 cast<CmpInst>(FirstInst)->getPredicate())
8059 // Keep track of which operand needs a phi node.
8060 if (I->getOperand(0) != LHSVal) LHSVal = 0;
8061 if (I->getOperand(1) != RHSVal) RHSVal = 0;
8064 // Otherwise, this is safe to transform, determine if it is profitable.
8066 // If this is a GEP, and if the index (not the pointer) needs a PHI, bail out.
8067 // Indexes are often folded into load/store instructions, so we don't want to
8068 // hide them behind a phi.
8069 if (isa<GetElementPtrInst>(FirstInst) && RHSVal == 0)
8072 Value *InLHS = FirstInst->getOperand(0);
8073 Value *InRHS = FirstInst->getOperand(1);
8074 PHINode *NewLHS = 0, *NewRHS = 0;
8076 NewLHS = new PHINode(LHSType, FirstInst->getOperand(0)->getName()+".pn");
8077 NewLHS->reserveOperandSpace(PN.getNumOperands()/2);
8078 NewLHS->addIncoming(InLHS, PN.getIncomingBlock(0));
8079 InsertNewInstBefore(NewLHS, PN);
8084 NewRHS = new PHINode(RHSType, FirstInst->getOperand(1)->getName()+".pn");
8085 NewRHS->reserveOperandSpace(PN.getNumOperands()/2);
8086 NewRHS->addIncoming(InRHS, PN.getIncomingBlock(0));
8087 InsertNewInstBefore(NewRHS, PN);
8091 // Add all operands to the new PHIs.
8092 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
8094 Value *NewInLHS =cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
8095 NewLHS->addIncoming(NewInLHS, PN.getIncomingBlock(i));
8098 Value *NewInRHS =cast<Instruction>(PN.getIncomingValue(i))->getOperand(1);
8099 NewRHS->addIncoming(NewInRHS, PN.getIncomingBlock(i));
8103 if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
8104 return BinaryOperator::create(BinOp->getOpcode(), LHSVal, RHSVal);
8105 else if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
8106 return CmpInst::create(CIOp->getOpcode(), CIOp->getPredicate(), LHSVal,
8109 assert(isa<GetElementPtrInst>(FirstInst));
8110 return new GetElementPtrInst(LHSVal, RHSVal);
8114 /// isSafeToSinkLoad - Return true if we know that it is safe sink the load out
8115 /// of the block that defines it. This means that it must be obvious the value
8116 /// of the load is not changed from the point of the load to the end of the
8119 /// Finally, it is safe, but not profitable, to sink a load targetting a
8120 /// non-address-taken alloca. Doing so will cause us to not promote the alloca
8122 static bool isSafeToSinkLoad(LoadInst *L) {
8123 BasicBlock::iterator BBI = L, E = L->getParent()->end();
8125 for (++BBI; BBI != E; ++BBI)
8126 if (BBI->mayWriteToMemory())
8129 // Check for non-address taken alloca. If not address-taken already, it isn't
8130 // profitable to do this xform.
8131 if (AllocaInst *AI = dyn_cast<AllocaInst>(L->getOperand(0))) {
8132 bool isAddressTaken = false;
8133 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
8135 if (isa<LoadInst>(UI)) continue;
8136 if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
8137 // If storing TO the alloca, then the address isn't taken.
8138 if (SI->getOperand(1) == AI) continue;
8140 isAddressTaken = true;
8144 if (!isAddressTaken)
8152 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
8153 // operator and they all are only used by the PHI, PHI together their
8154 // inputs, and do the operation once, to the result of the PHI.
8155 Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
8156 Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
8158 // Scan the instruction, looking for input operations that can be folded away.
8159 // If all input operands to the phi are the same instruction (e.g. a cast from
8160 // the same type or "+42") we can pull the operation through the PHI, reducing
8161 // code size and simplifying code.
8162 Constant *ConstantOp = 0;
8163 const Type *CastSrcTy = 0;
8164 bool isVolatile = false;
8165 if (isa<CastInst>(FirstInst)) {
8166 CastSrcTy = FirstInst->getOperand(0)->getType();
8167 } else if (isa<BinaryOperator>(FirstInst) || isa<CmpInst>(FirstInst)) {
8168 // Can fold binop, compare or shift here if the RHS is a constant,
8169 // otherwise call FoldPHIArgBinOpIntoPHI.
8170 ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
8171 if (ConstantOp == 0)
8172 return FoldPHIArgBinOpIntoPHI(PN);
8173 } else if (LoadInst *LI = dyn_cast<LoadInst>(FirstInst)) {
8174 isVolatile = LI->isVolatile();
8175 // We can't sink the load if the loaded value could be modified between the
8176 // load and the PHI.
8177 if (LI->getParent() != PN.getIncomingBlock(0) ||
8178 !isSafeToSinkLoad(LI))
8180 } else if (isa<GetElementPtrInst>(FirstInst)) {
8181 if (FirstInst->getNumOperands() == 2)
8182 return FoldPHIArgBinOpIntoPHI(PN);
8183 // Can't handle general GEPs yet.
8186 return 0; // Cannot fold this operation.
8189 // Check to see if all arguments are the same operation.
8190 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
8191 if (!isa<Instruction>(PN.getIncomingValue(i))) return 0;
8192 Instruction *I = cast<Instruction>(PN.getIncomingValue(i));
8193 if (!I->hasOneUse() || !I->isSameOperationAs(FirstInst))
8196 if (I->getOperand(0)->getType() != CastSrcTy)
8197 return 0; // Cast operation must match.
8198 } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
8199 // We can't sink the load if the loaded value could be modified between
8200 // the load and the PHI.
8201 if (LI->isVolatile() != isVolatile ||
8202 LI->getParent() != PN.getIncomingBlock(i) ||
8203 !isSafeToSinkLoad(LI))
8205 } else if (I->getOperand(1) != ConstantOp) {
8210 // Okay, they are all the same operation. Create a new PHI node of the
8211 // correct type, and PHI together all of the LHS's of the instructions.
8212 PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(),
8213 PN.getName()+".in");
8214 NewPN->reserveOperandSpace(PN.getNumOperands()/2);
8216 Value *InVal = FirstInst->getOperand(0);
8217 NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
8219 // Add all operands to the new PHI.
8220 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
8221 Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
8222 if (NewInVal != InVal)
8224 NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
8229 // The new PHI unions all of the same values together. This is really
8230 // common, so we handle it intelligently here for compile-time speed.
8234 InsertNewInstBefore(NewPN, PN);
8238 // Insert and return the new operation.
8239 if (CastInst* FirstCI = dyn_cast<CastInst>(FirstInst))
8240 return CastInst::create(FirstCI->getOpcode(), PhiVal, PN.getType());
8241 else if (isa<LoadInst>(FirstInst))
8242 return new LoadInst(PhiVal, "", isVolatile);
8243 else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
8244 return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
8245 else if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
8246 return CmpInst::create(CIOp->getOpcode(), CIOp->getPredicate(),
8247 PhiVal, ConstantOp);
8249 assert(0 && "Unknown operation");
8253 /// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
8255 static bool DeadPHICycle(PHINode *PN,
8256 SmallPtrSet<PHINode*, 16> &PotentiallyDeadPHIs) {
8257 if (PN->use_empty()) return true;
8258 if (!PN->hasOneUse()) return false;
8260 // Remember this node, and if we find the cycle, return.
8261 if (!PotentiallyDeadPHIs.insert(PN))
8264 if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
8265 return DeadPHICycle(PU, PotentiallyDeadPHIs);
8270 // PHINode simplification
8272 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
8273 // If LCSSA is around, don't mess with Phi nodes
8274 if (MustPreserveLCSSA) return 0;
8276 if (Value *V = PN.hasConstantValue())
8277 return ReplaceInstUsesWith(PN, V);
8279 // If all PHI operands are the same operation, pull them through the PHI,
8280 // reducing code size.
8281 if (isa<Instruction>(PN.getIncomingValue(0)) &&
8282 PN.getIncomingValue(0)->hasOneUse())
8283 if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
8286 // If this is a trivial cycle in the PHI node graph, remove it. Basically, if
8287 // this PHI only has a single use (a PHI), and if that PHI only has one use (a
8288 // PHI)... break the cycle.
8289 if (PN.hasOneUse()) {
8290 Instruction *PHIUser = cast<Instruction>(PN.use_back());
8291 if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) {
8292 SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs;
8293 PotentiallyDeadPHIs.insert(&PN);
8294 if (DeadPHICycle(PU, PotentiallyDeadPHIs))
8295 return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
8298 // If this phi has a single use, and if that use just computes a value for
8299 // the next iteration of a loop, delete the phi. This occurs with unused
8300 // induction variables, e.g. "for (int j = 0; ; ++j);". Detecting this
8301 // common case here is good because the only other things that catch this
8302 // are induction variable analysis (sometimes) and ADCE, which is only run
8304 if (PHIUser->hasOneUse() &&
8305 (isa<BinaryOperator>(PHIUser) || isa<GetElementPtrInst>(PHIUser)) &&
8306 PHIUser->use_back() == &PN) {
8307 return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
8314 static Value *InsertCastToIntPtrTy(Value *V, const Type *DTy,
8315 Instruction *InsertPoint,
8317 unsigned PtrSize = DTy->getPrimitiveSizeInBits();
8318 unsigned VTySize = V->getType()->getPrimitiveSizeInBits();
8319 // We must cast correctly to the pointer type. Ensure that we
8320 // sign extend the integer value if it is smaller as this is
8321 // used for address computation.
8322 Instruction::CastOps opcode =
8323 (VTySize < PtrSize ? Instruction::SExt :
8324 (VTySize == PtrSize ? Instruction::BitCast : Instruction::Trunc));
8325 return IC->InsertCastBefore(opcode, V, DTy, *InsertPoint);
8329 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
8330 Value *PtrOp = GEP.getOperand(0);
8331 // Is it 'getelementptr %P, i32 0' or 'getelementptr %P'
8332 // If so, eliminate the noop.
8333 if (GEP.getNumOperands() == 1)
8334 return ReplaceInstUsesWith(GEP, PtrOp);
8336 if (isa<UndefValue>(GEP.getOperand(0)))
8337 return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
8339 bool HasZeroPointerIndex = false;
8340 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
8341 HasZeroPointerIndex = C->isNullValue();
8343 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
8344 return ReplaceInstUsesWith(GEP, PtrOp);
8346 // Eliminate unneeded casts for indices.
8347 bool MadeChange = false;
8349 gep_type_iterator GTI = gep_type_begin(GEP);
8350 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI) {
8351 if (isa<SequentialType>(*GTI)) {
8352 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
8353 if (CI->getOpcode() == Instruction::ZExt ||
8354 CI->getOpcode() == Instruction::SExt) {
8355 const Type *SrcTy = CI->getOperand(0)->getType();
8356 // We can eliminate a cast from i32 to i64 iff the target
8357 // is a 32-bit pointer target.
8358 if (SrcTy->getPrimitiveSizeInBits() >= TD->getPointerSizeInBits()) {
8360 GEP.setOperand(i, CI->getOperand(0));
8364 // If we are using a wider index than needed for this platform, shrink it
8365 // to what we need. If the incoming value needs a cast instruction,
8366 // insert it. This explicit cast can make subsequent optimizations more
8368 Value *Op = GEP.getOperand(i);
8369 if (TD->getTypeSize(Op->getType()) > TD->getPointerSize())
8370 if (Constant *C = dyn_cast<Constant>(Op)) {
8371 GEP.setOperand(i, ConstantExpr::getTrunc(C, TD->getIntPtrType()));
8374 Op = InsertCastBefore(Instruction::Trunc, Op, TD->getIntPtrType(),
8376 GEP.setOperand(i, Op);
8381 if (MadeChange) return &GEP;
8383 // If this GEP instruction doesn't move the pointer, and if the input operand
8384 // is a bitcast of another pointer, just replace the GEP with a bitcast of the
8385 // real input to the dest type.
8386 if (GEP.hasAllZeroIndices() && isa<BitCastInst>(GEP.getOperand(0)))
8387 return new BitCastInst(cast<BitCastInst>(GEP.getOperand(0))->getOperand(0),
8390 // Combine Indices - If the source pointer to this getelementptr instruction
8391 // is a getelementptr instruction, combine the indices of the two
8392 // getelementptr instructions into a single instruction.
8394 SmallVector<Value*, 8> SrcGEPOperands;
8395 if (User *Src = dyn_castGetElementPtr(PtrOp))
8396 SrcGEPOperands.append(Src->op_begin(), Src->op_end());
8398 if (!SrcGEPOperands.empty()) {
8399 // Note that if our source is a gep chain itself that we wait for that
8400 // chain to be resolved before we perform this transformation. This
8401 // avoids us creating a TON of code in some cases.
8403 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
8404 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
8405 return 0; // Wait until our source is folded to completion.
8407 SmallVector<Value*, 8> Indices;
8409 // Find out whether the last index in the source GEP is a sequential idx.
8410 bool EndsWithSequential = false;
8411 for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
8412 E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
8413 EndsWithSequential = !isa<StructType>(*I);
8415 // Can we combine the two pointer arithmetics offsets?
8416 if (EndsWithSequential) {
8417 // Replace: gep (gep %P, long B), long A, ...
8418 // With: T = long A+B; gep %P, T, ...
8420 Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
8421 if (SO1 == Constant::getNullValue(SO1->getType())) {
8423 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
8426 // If they aren't the same type, convert both to an integer of the
8427 // target's pointer size.
8428 if (SO1->getType() != GO1->getType()) {
8429 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
8430 SO1 = ConstantExpr::getIntegerCast(SO1C, GO1->getType(), true);
8431 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
8432 GO1 = ConstantExpr::getIntegerCast(GO1C, SO1->getType(), true);
8434 unsigned PS = TD->getPointerSize();
8435 if (TD->getTypeSize(SO1->getType()) == PS) {
8436 // Convert GO1 to SO1's type.
8437 GO1 = InsertCastToIntPtrTy(GO1, SO1->getType(), &GEP, this);
8439 } else if (TD->getTypeSize(GO1->getType()) == PS) {
8440 // Convert SO1 to GO1's type.
8441 SO1 = InsertCastToIntPtrTy(SO1, GO1->getType(), &GEP, this);
8443 const Type *PT = TD->getIntPtrType();
8444 SO1 = InsertCastToIntPtrTy(SO1, PT, &GEP, this);
8445 GO1 = InsertCastToIntPtrTy(GO1, PT, &GEP, this);
8449 if (isa<Constant>(SO1) && isa<Constant>(GO1))
8450 Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
8452 Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
8453 InsertNewInstBefore(cast<Instruction>(Sum), GEP);
8457 // Recycle the GEP we already have if possible.
8458 if (SrcGEPOperands.size() == 2) {
8459 GEP.setOperand(0, SrcGEPOperands[0]);
8460 GEP.setOperand(1, Sum);
8463 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
8464 SrcGEPOperands.end()-1);
8465 Indices.push_back(Sum);
8466 Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
8468 } else if (isa<Constant>(*GEP.idx_begin()) &&
8469 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
8470 SrcGEPOperands.size() != 1) {
8471 // Otherwise we can do the fold if the first index of the GEP is a zero
8472 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
8473 SrcGEPOperands.end());
8474 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
8477 if (!Indices.empty())
8478 return new GetElementPtrInst(SrcGEPOperands[0], &Indices[0],
8479 Indices.size(), GEP.getName());
8481 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
8482 // GEP of global variable. If all of the indices for this GEP are
8483 // constants, we can promote this to a constexpr instead of an instruction.
8485 // Scan for nonconstants...
8486 SmallVector<Constant*, 8> Indices;
8487 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
8488 for (; I != E && isa<Constant>(*I); ++I)
8489 Indices.push_back(cast<Constant>(*I));
8491 if (I == E) { // If they are all constants...
8492 Constant *CE = ConstantExpr::getGetElementPtr(GV,
8493 &Indices[0],Indices.size());
8495 // Replace all uses of the GEP with the new constexpr...
8496 return ReplaceInstUsesWith(GEP, CE);
8498 } else if (Value *X = getBitCastOperand(PtrOp)) { // Is the operand a cast?
8499 if (!isa<PointerType>(X->getType())) {
8500 // Not interesting. Source pointer must be a cast from pointer.
8501 } else if (HasZeroPointerIndex) {
8502 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
8503 // into : GEP [10 x ubyte]* X, long 0, ...
8505 // This occurs when the program declares an array extern like "int X[];"
8507 const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
8508 const PointerType *XTy = cast<PointerType>(X->getType());
8509 if (const ArrayType *XATy =
8510 dyn_cast<ArrayType>(XTy->getElementType()))
8511 if (const ArrayType *CATy =
8512 dyn_cast<ArrayType>(CPTy->getElementType()))
8513 if (CATy->getElementType() == XATy->getElementType()) {
8514 // At this point, we know that the cast source type is a pointer
8515 // to an array of the same type as the destination pointer
8516 // array. Because the array type is never stepped over (there
8517 // is a leading zero) we can fold the cast into this GEP.
8518 GEP.setOperand(0, X);
8521 } else if (GEP.getNumOperands() == 2) {
8522 // Transform things like:
8523 // %t = getelementptr ubyte* cast ([2 x int]* %str to uint*), uint %V
8524 // into: %t1 = getelementptr [2 x int*]* %str, int 0, uint %V; cast
8525 const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
8526 const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
8527 if (isa<ArrayType>(SrcElTy) &&
8528 TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
8529 TD->getTypeSize(ResElTy)) {
8530 Value *V = InsertNewInstBefore(
8531 new GetElementPtrInst(X, Constant::getNullValue(Type::Int32Ty),
8532 GEP.getOperand(1), GEP.getName()), GEP);
8533 // V and GEP are both pointer types --> BitCast
8534 return new BitCastInst(V, GEP.getType());
8537 // Transform things like:
8538 // getelementptr sbyte* cast ([100 x double]* X to sbyte*), int %tmp
8539 // (where tmp = 8*tmp2) into:
8540 // getelementptr [100 x double]* %arr, int 0, int %tmp.2
8542 if (isa<ArrayType>(SrcElTy) &&
8543 (ResElTy == Type::Int8Ty || ResElTy == Type::Int8Ty)) {
8544 uint64_t ArrayEltSize =
8545 TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType());
8547 // Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We
8548 // allow either a mul, shift, or constant here.
8550 ConstantInt *Scale = 0;
8551 if (ArrayEltSize == 1) {
8552 NewIdx = GEP.getOperand(1);
8553 Scale = ConstantInt::get(NewIdx->getType(), 1);
8554 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
8555 NewIdx = ConstantInt::get(CI->getType(), 1);
8557 } else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
8558 if (Inst->getOpcode() == Instruction::Shl &&
8559 isa<ConstantInt>(Inst->getOperand(1))) {
8560 ConstantInt *ShAmt = cast<ConstantInt>(Inst->getOperand(1));
8561 uint32_t ShAmtVal = ShAmt->getLimitedValue(64);
8562 Scale = ConstantInt::get(Inst->getType(), 1ULL << ShAmtVal);
8563 NewIdx = Inst->getOperand(0);
8564 } else if (Inst->getOpcode() == Instruction::Mul &&
8565 isa<ConstantInt>(Inst->getOperand(1))) {
8566 Scale = cast<ConstantInt>(Inst->getOperand(1));
8567 NewIdx = Inst->getOperand(0);
8571 // If the index will be to exactly the right offset with the scale taken
8572 // out, perform the transformation.
8573 if (Scale && Scale->getZExtValue() % ArrayEltSize == 0) {
8574 if (isa<ConstantInt>(Scale))
8575 Scale = ConstantInt::get(Scale->getType(),
8576 Scale->getZExtValue() / ArrayEltSize);
8577 if (Scale->getZExtValue() != 1) {
8578 Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(),
8580 Instruction *Sc = BinaryOperator::createMul(NewIdx, C, "idxscale");
8581 NewIdx = InsertNewInstBefore(Sc, GEP);
8584 // Insert the new GEP instruction.
8585 Instruction *NewGEP =
8586 new GetElementPtrInst(X, Constant::getNullValue(Type::Int32Ty),
8587 NewIdx, GEP.getName());
8588 NewGEP = InsertNewInstBefore(NewGEP, GEP);
8589 // The NewGEP must be pointer typed, so must the old one -> BitCast
8590 return new BitCastInst(NewGEP, GEP.getType());
8599 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
8600 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
8601 if (AI.isArrayAllocation()) // Check C != 1
8602 if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
8604 ArrayType::get(AI.getAllocatedType(), C->getZExtValue());
8605 AllocationInst *New = 0;
8607 // Create and insert the replacement instruction...
8608 if (isa<MallocInst>(AI))
8609 New = new MallocInst(NewTy, 0, AI.getAlignment(), AI.getName());
8611 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
8612 New = new AllocaInst(NewTy, 0, AI.getAlignment(), AI.getName());
8615 InsertNewInstBefore(New, AI);
8617 // Scan to the end of the allocation instructions, to skip over a block of
8618 // allocas if possible...
8620 BasicBlock::iterator It = New;
8621 while (isa<AllocationInst>(*It)) ++It;
8623 // Now that I is pointing to the first non-allocation-inst in the block,
8624 // insert our getelementptr instruction...
8626 Value *NullIdx = Constant::getNullValue(Type::Int32Ty);
8627 Value *V = new GetElementPtrInst(New, NullIdx, NullIdx,
8628 New->getName()+".sub", It);
8630 // Now make everything use the getelementptr instead of the original
8632 return ReplaceInstUsesWith(AI, V);
8633 } else if (isa<UndefValue>(AI.getArraySize())) {
8634 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
8637 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
8638 // Note that we only do this for alloca's, because malloc should allocate and
8639 // return a unique pointer, even for a zero byte allocation.
8640 if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
8641 TD->getTypeSize(AI.getAllocatedType()) == 0)
8642 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
8647 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
8648 Value *Op = FI.getOperand(0);
8650 // free undef -> unreachable.
8651 if (isa<UndefValue>(Op)) {
8652 // Insert a new store to null because we cannot modify the CFG here.
8653 new StoreInst(ConstantInt::getTrue(),
8654 UndefValue::get(PointerType::get(Type::Int1Ty)), &FI);
8655 return EraseInstFromFunction(FI);
8658 // If we have 'free null' delete the instruction. This can happen in stl code
8659 // when lots of inlining happens.
8660 if (isa<ConstantPointerNull>(Op))
8661 return EraseInstFromFunction(FI);
8663 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
8664 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op)) {
8665 FI.setOperand(0, CI->getOperand(0));
8669 // Change free (gep X, 0,0,0,0) into free(X)
8670 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
8671 if (GEPI->hasAllZeroIndices()) {
8672 AddToWorkList(GEPI);
8673 FI.setOperand(0, GEPI->getOperand(0));
8678 // Change free(malloc) into nothing, if the malloc has a single use.
8679 if (MallocInst *MI = dyn_cast<MallocInst>(Op))
8680 if (MI->hasOneUse()) {
8681 EraseInstFromFunction(FI);
8682 return EraseInstFromFunction(*MI);
8689 /// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible.
8690 static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
8691 User *CI = cast<User>(LI.getOperand(0));
8692 Value *CastOp = CI->getOperand(0);
8694 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
8695 if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
8696 const Type *SrcPTy = SrcTy->getElementType();
8698 if (DestPTy->isInteger() || isa<PointerType>(DestPTy) ||
8699 isa<VectorType>(DestPTy)) {
8700 // If the source is an array, the code below will not succeed. Check to
8701 // see if a trivial 'gep P, 0, 0' will help matters. Only do this for
8703 if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
8704 if (Constant *CSrc = dyn_cast<Constant>(CastOp))
8705 if (ASrcTy->getNumElements() != 0) {
8707 Idxs[0] = Idxs[1] = Constant::getNullValue(Type::Int32Ty);
8708 CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs, 2);
8709 SrcTy = cast<PointerType>(CastOp->getType());
8710 SrcPTy = SrcTy->getElementType();
8713 if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy) ||
8714 isa<VectorType>(SrcPTy)) &&
8715 // Do not allow turning this into a load of an integer, which is then
8716 // casted to a pointer, this pessimizes pointer analysis a lot.
8717 (isa<PointerType>(SrcPTy) == isa<PointerType>(LI.getType())) &&
8718 IC.getTargetData().getTypeSizeInBits(SrcPTy) ==
8719 IC.getTargetData().getTypeSizeInBits(DestPTy)) {
8721 // Okay, we are casting from one integer or pointer type to another of
8722 // the same size. Instead of casting the pointer before the load, cast
8723 // the result of the loaded value.
8724 Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CastOp,
8726 LI.isVolatile()),LI);
8727 // Now cast the result of the load.
8728 return new BitCastInst(NewLoad, LI.getType());
8735 /// isSafeToLoadUnconditionally - Return true if we know that executing a load
8736 /// from this value cannot trap. If it is not obviously safe to load from the
8737 /// specified pointer, we do a quick local scan of the basic block containing
8738 /// ScanFrom, to determine if the address is already accessed.
8739 static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
8740 // If it is an alloca or global variable, it is always safe to load from.
8741 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
8743 // Otherwise, be a little bit agressive by scanning the local block where we
8744 // want to check to see if the pointer is already being loaded or stored
8745 // from/to. If so, the previous load or store would have already trapped,
8746 // so there is no harm doing an extra load (also, CSE will later eliminate
8747 // the load entirely).
8748 BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
8753 if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
8754 if (LI->getOperand(0) == V) return true;
8755 } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
8756 if (SI->getOperand(1) == V) return true;
8762 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
8763 Value *Op = LI.getOperand(0);
8765 // Attempt to improve the alignment.
8766 unsigned KnownAlign = GetKnownAlignment(Op, TD);
8767 if (KnownAlign > LI.getAlignment())
8768 LI.setAlignment(KnownAlign);
8770 // load (cast X) --> cast (load X) iff safe
8771 if (isa<CastInst>(Op))
8772 if (Instruction *Res = InstCombineLoadCast(*this, LI))
8775 // None of the following transforms are legal for volatile loads.
8776 if (LI.isVolatile()) return 0;
8778 if (&LI.getParent()->front() != &LI) {
8779 BasicBlock::iterator BBI = &LI; --BBI;
8780 // If the instruction immediately before this is a store to the same
8781 // address, do a simple form of store->load forwarding.
8782 if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
8783 if (SI->getOperand(1) == LI.getOperand(0))
8784 return ReplaceInstUsesWith(LI, SI->getOperand(0));
8785 if (LoadInst *LIB = dyn_cast<LoadInst>(BBI))
8786 if (LIB->getOperand(0) == LI.getOperand(0))
8787 return ReplaceInstUsesWith(LI, LIB);
8790 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op))
8791 if (isa<ConstantPointerNull>(GEPI->getOperand(0))) {
8792 // Insert a new store to null instruction before the load to indicate
8793 // that this code is not reachable. We do this instead of inserting
8794 // an unreachable instruction directly because we cannot modify the
8796 new StoreInst(UndefValue::get(LI.getType()),
8797 Constant::getNullValue(Op->getType()), &LI);
8798 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
8801 if (Constant *C = dyn_cast<Constant>(Op)) {
8802 // load null/undef -> undef
8803 if ((C->isNullValue() || isa<UndefValue>(C))) {
8804 // Insert a new store to null instruction before the load to indicate that
8805 // this code is not reachable. We do this instead of inserting an
8806 // unreachable instruction directly because we cannot modify the CFG.
8807 new StoreInst(UndefValue::get(LI.getType()),
8808 Constant::getNullValue(Op->getType()), &LI);
8809 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
8812 // Instcombine load (constant global) into the value loaded.
8813 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
8814 if (GV->isConstant() && !GV->isDeclaration())
8815 return ReplaceInstUsesWith(LI, GV->getInitializer());
8817 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
8818 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
8819 if (CE->getOpcode() == Instruction::GetElementPtr) {
8820 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
8821 if (GV->isConstant() && !GV->isDeclaration())
8823 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
8824 return ReplaceInstUsesWith(LI, V);
8825 if (CE->getOperand(0)->isNullValue()) {
8826 // Insert a new store to null instruction before the load to indicate
8827 // that this code is not reachable. We do this instead of inserting
8828 // an unreachable instruction directly because we cannot modify the
8830 new StoreInst(UndefValue::get(LI.getType()),
8831 Constant::getNullValue(Op->getType()), &LI);
8832 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
8835 } else if (CE->isCast()) {
8836 if (Instruction *Res = InstCombineLoadCast(*this, LI))
8841 if (Op->hasOneUse()) {
8842 // Change select and PHI nodes to select values instead of addresses: this
8843 // helps alias analysis out a lot, allows many others simplifications, and
8844 // exposes redundancy in the code.
8846 // Note that we cannot do the transformation unless we know that the
8847 // introduced loads cannot trap! Something like this is valid as long as
8848 // the condition is always false: load (select bool %C, int* null, int* %G),
8849 // but it would not be valid if we transformed it to load from null
8852 if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
8853 // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
8854 if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
8855 isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
8856 Value *V1 = InsertNewInstBefore(new LoadInst(SI->getOperand(1),
8857 SI->getOperand(1)->getName()+".val"), LI);
8858 Value *V2 = InsertNewInstBefore(new LoadInst(SI->getOperand(2),
8859 SI->getOperand(2)->getName()+".val"), LI);
8860 return new SelectInst(SI->getCondition(), V1, V2);
8863 // load (select (cond, null, P)) -> load P
8864 if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
8865 if (C->isNullValue()) {
8866 LI.setOperand(0, SI->getOperand(2));
8870 // load (select (cond, P, null)) -> load P
8871 if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
8872 if (C->isNullValue()) {
8873 LI.setOperand(0, SI->getOperand(1));
8881 /// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P
8883 static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
8884 User *CI = cast<User>(SI.getOperand(1));
8885 Value *CastOp = CI->getOperand(0);
8887 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
8888 if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
8889 const Type *SrcPTy = SrcTy->getElementType();
8891 if (DestPTy->isInteger() || isa<PointerType>(DestPTy)) {
8892 // If the source is an array, the code below will not succeed. Check to
8893 // see if a trivial 'gep P, 0, 0' will help matters. Only do this for
8895 if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
8896 if (Constant *CSrc = dyn_cast<Constant>(CastOp))
8897 if (ASrcTy->getNumElements() != 0) {
8899 Idxs[0] = Idxs[1] = Constant::getNullValue(Type::Int32Ty);
8900 CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs, 2);
8901 SrcTy = cast<PointerType>(CastOp->getType());
8902 SrcPTy = SrcTy->getElementType();
8905 if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
8906 IC.getTargetData().getTypeSizeInBits(SrcPTy) ==
8907 IC.getTargetData().getTypeSizeInBits(DestPTy)) {
8909 // Okay, we are casting from one integer or pointer type to another of
8910 // the same size. Instead of casting the pointer before
8911 // the store, cast the value to be stored.
8913 Value *SIOp0 = SI.getOperand(0);
8914 Instruction::CastOps opcode = Instruction::BitCast;
8915 const Type* CastSrcTy = SIOp0->getType();
8916 const Type* CastDstTy = SrcPTy;
8917 if (isa<PointerType>(CastDstTy)) {
8918 if (CastSrcTy->isInteger())
8919 opcode = Instruction::IntToPtr;
8920 } else if (isa<IntegerType>(CastDstTy)) {
8921 if (isa<PointerType>(SIOp0->getType()))
8922 opcode = Instruction::PtrToInt;
8924 if (Constant *C = dyn_cast<Constant>(SIOp0))
8925 NewCast = ConstantExpr::getCast(opcode, C, CastDstTy);
8927 NewCast = IC.InsertNewInstBefore(
8928 CastInst::create(opcode, SIOp0, CastDstTy, SIOp0->getName()+".c"),
8930 return new StoreInst(NewCast, CastOp);
8937 Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
8938 Value *Val = SI.getOperand(0);
8939 Value *Ptr = SI.getOperand(1);
8941 if (isa<UndefValue>(Ptr)) { // store X, undef -> noop (even if volatile)
8942 EraseInstFromFunction(SI);
8947 // If the RHS is an alloca with a single use, zapify the store, making the
8949 if (Ptr->hasOneUse()) {
8950 if (isa<AllocaInst>(Ptr)) {
8951 EraseInstFromFunction(SI);
8956 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr))
8957 if (isa<AllocaInst>(GEP->getOperand(0)) &&
8958 GEP->getOperand(0)->hasOneUse()) {
8959 EraseInstFromFunction(SI);
8965 // Attempt to improve the alignment.
8966 unsigned KnownAlign = GetKnownAlignment(Ptr, TD);
8967 if (KnownAlign > SI.getAlignment())
8968 SI.setAlignment(KnownAlign);
8970 // Do really simple DSE, to catch cases where there are several consequtive
8971 // stores to the same location, separated by a few arithmetic operations. This
8972 // situation often occurs with bitfield accesses.
8973 BasicBlock::iterator BBI = &SI;
8974 for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts;
8978 if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) {
8979 // Prev store isn't volatile, and stores to the same location?
8980 if (!PrevSI->isVolatile() && PrevSI->getOperand(1) == SI.getOperand(1)) {
8983 EraseInstFromFunction(*PrevSI);
8989 // If this is a load, we have to stop. However, if the loaded value is from
8990 // the pointer we're loading and is producing the pointer we're storing,
8991 // then *this* store is dead (X = load P; store X -> P).
8992 if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
8993 if (LI == Val && LI->getOperand(0) == Ptr) {
8994 EraseInstFromFunction(SI);
8998 // Otherwise, this is a load from some other location. Stores before it
9003 // Don't skip over loads or things that can modify memory.
9004 if (BBI->mayWriteToMemory())
9009 if (SI.isVolatile()) return 0; // Don't hack volatile stores.
9011 // store X, null -> turns into 'unreachable' in SimplifyCFG
9012 if (isa<ConstantPointerNull>(Ptr)) {
9013 if (!isa<UndefValue>(Val)) {
9014 SI.setOperand(0, UndefValue::get(Val->getType()));
9015 if (Instruction *U = dyn_cast<Instruction>(Val))
9016 AddToWorkList(U); // Dropped a use.
9019 return 0; // Do not modify these!
9022 // store undef, Ptr -> noop
9023 if (isa<UndefValue>(Val)) {
9024 EraseInstFromFunction(SI);
9029 // If the pointer destination is a cast, see if we can fold the cast into the
9031 if (isa<CastInst>(Ptr))
9032 if (Instruction *Res = InstCombineStoreToCast(*this, SI))
9034 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
9036 if (Instruction *Res = InstCombineStoreToCast(*this, SI))
9040 // If this store is the last instruction in the basic block, and if the block
9041 // ends with an unconditional branch, try to move it to the successor block.
9043 if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
9044 if (BI->isUnconditional())
9045 if (SimplifyStoreAtEndOfBlock(SI))
9046 return 0; // xform done!
9051 /// SimplifyStoreAtEndOfBlock - Turn things like:
9052 /// if () { *P = v1; } else { *P = v2 }
9053 /// into a phi node with a store in the successor.
9055 /// Simplify things like:
9056 /// *P = v1; if () { *P = v2; }
9057 /// into a phi node with a store in the successor.
9059 bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
9060 BasicBlock *StoreBB = SI.getParent();
9062 // Check to see if the successor block has exactly two incoming edges. If
9063 // so, see if the other predecessor contains a store to the same location.
9064 // if so, insert a PHI node (if needed) and move the stores down.
9065 BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0);
9067 // Determine whether Dest has exactly two predecessors and, if so, compute
9068 // the other predecessor.
9069 pred_iterator PI = pred_begin(DestBB);
9070 BasicBlock *OtherBB = 0;
9074 if (PI == pred_end(DestBB))
9077 if (*PI != StoreBB) {
9082 if (++PI != pred_end(DestBB))
9086 // Verify that the other block ends in a branch and is not otherwise empty.
9087 BasicBlock::iterator BBI = OtherBB->getTerminator();
9088 BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
9089 if (!OtherBr || BBI == OtherBB->begin())
9092 // If the other block ends in an unconditional branch, check for the 'if then
9093 // else' case. there is an instruction before the branch.
9094 StoreInst *OtherStore = 0;
9095 if (OtherBr->isUnconditional()) {
9096 // If this isn't a store, or isn't a store to the same location, bail out.
9098 OtherStore = dyn_cast<StoreInst>(BBI);
9099 if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1))
9102 // Otherwise, the other block ended with a conditional branch. If one of the
9103 // destinations is StoreBB, then we have the if/then case.
9104 if (OtherBr->getSuccessor(0) != StoreBB &&
9105 OtherBr->getSuccessor(1) != StoreBB)
9108 // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
9109 // if/then triangle. See if there is a store to the same ptr as SI that
9110 // lives in OtherBB.
9112 // Check to see if we find the matching store.
9113 if ((OtherStore = dyn_cast<StoreInst>(BBI))) {
9114 if (OtherStore->getOperand(1) != SI.getOperand(1))
9118 // If we find something that may be using the stored value, or if we run
9119 // out of instructions, we can't do the xform.
9120 if (isa<LoadInst>(BBI) || BBI->mayWriteToMemory() ||
9121 BBI == OtherBB->begin())
9125 // In order to eliminate the store in OtherBr, we have to
9126 // make sure nothing reads the stored value in StoreBB.
9127 for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
9128 // FIXME: This should really be AA driven.
9129 if (isa<LoadInst>(I) || I->mayWriteToMemory())
9134 // Insert a PHI node now if we need it.
9135 Value *MergedVal = OtherStore->getOperand(0);
9136 if (MergedVal != SI.getOperand(0)) {
9137 PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
9138 PN->reserveOperandSpace(2);
9139 PN->addIncoming(SI.getOperand(0), SI.getParent());
9140 PN->addIncoming(OtherStore->getOperand(0), OtherBB);
9141 MergedVal = InsertNewInstBefore(PN, DestBB->front());
9144 // Advance to a place where it is safe to insert the new store and
9146 BBI = DestBB->begin();
9147 while (isa<PHINode>(BBI)) ++BBI;
9148 InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
9149 OtherStore->isVolatile()), *BBI);
9151 // Nuke the old stores.
9152 EraseInstFromFunction(SI);
9153 EraseInstFromFunction(*OtherStore);
9159 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
9160 // Change br (not X), label True, label False to: br X, label False, True
9162 BasicBlock *TrueDest;
9163 BasicBlock *FalseDest;
9164 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
9165 !isa<Constant>(X)) {
9166 // Swap Destinations and condition...
9168 BI.setSuccessor(0, FalseDest);
9169 BI.setSuccessor(1, TrueDest);
9173 // Cannonicalize fcmp_one -> fcmp_oeq
9174 FCmpInst::Predicate FPred; Value *Y;
9175 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)),
9176 TrueDest, FalseDest)))
9177 if ((FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE ||
9178 FPred == FCmpInst::FCMP_OGE) && BI.getCondition()->hasOneUse()) {
9179 FCmpInst *I = cast<FCmpInst>(BI.getCondition());
9180 FCmpInst::Predicate NewPred = FCmpInst::getInversePredicate(FPred);
9181 Instruction *NewSCC = new FCmpInst(NewPred, X, Y, "", I);
9182 NewSCC->takeName(I);
9183 // Swap Destinations and condition...
9184 BI.setCondition(NewSCC);
9185 BI.setSuccessor(0, FalseDest);
9186 BI.setSuccessor(1, TrueDest);
9187 RemoveFromWorkList(I);
9188 I->eraseFromParent();
9189 AddToWorkList(NewSCC);
9193 // Cannonicalize icmp_ne -> icmp_eq
9194 ICmpInst::Predicate IPred;
9195 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)),
9196 TrueDest, FalseDest)))
9197 if ((IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE ||
9198 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE ||
9199 IPred == ICmpInst::ICMP_SGE) && BI.getCondition()->hasOneUse()) {
9200 ICmpInst *I = cast<ICmpInst>(BI.getCondition());
9201 ICmpInst::Predicate NewPred = ICmpInst::getInversePredicate(IPred);
9202 Instruction *NewSCC = new ICmpInst(NewPred, X, Y, "", I);
9203 NewSCC->takeName(I);
9204 // Swap Destinations and condition...
9205 BI.setCondition(NewSCC);
9206 BI.setSuccessor(0, FalseDest);
9207 BI.setSuccessor(1, TrueDest);
9208 RemoveFromWorkList(I);
9209 I->eraseFromParent();;
9210 AddToWorkList(NewSCC);
9217 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
9218 Value *Cond = SI.getCondition();
9219 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
9220 if (I->getOpcode() == Instruction::Add)
9221 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
9222 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
9223 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
9224 SI.setOperand(i,ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
9226 SI.setOperand(0, I->getOperand(0));
9234 /// CheapToScalarize - Return true if the value is cheaper to scalarize than it
9235 /// is to leave as a vector operation.
9236 static bool CheapToScalarize(Value *V, bool isConstant) {
9237 if (isa<ConstantAggregateZero>(V))
9239 if (ConstantVector *C = dyn_cast<ConstantVector>(V)) {
9240 if (isConstant) return true;
9241 // If all elts are the same, we can extract.
9242 Constant *Op0 = C->getOperand(0);
9243 for (unsigned i = 1; i < C->getNumOperands(); ++i)
9244 if (C->getOperand(i) != Op0)
9248 Instruction *I = dyn_cast<Instruction>(V);
9249 if (!I) return false;
9251 // Insert element gets simplified to the inserted element or is deleted if
9252 // this is constant idx extract element and its a constant idx insertelt.
9253 if (I->getOpcode() == Instruction::InsertElement && isConstant &&
9254 isa<ConstantInt>(I->getOperand(2)))
9256 if (I->getOpcode() == Instruction::Load && I->hasOneUse())
9258 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I))
9259 if (BO->hasOneUse() &&
9260 (CheapToScalarize(BO->getOperand(0), isConstant) ||
9261 CheapToScalarize(BO->getOperand(1), isConstant)))
9263 if (CmpInst *CI = dyn_cast<CmpInst>(I))
9264 if (CI->hasOneUse() &&
9265 (CheapToScalarize(CI->getOperand(0), isConstant) ||
9266 CheapToScalarize(CI->getOperand(1), isConstant)))
9272 /// Read and decode a shufflevector mask.
9274 /// It turns undef elements into values that are larger than the number of
9275 /// elements in the input.
9276 static std::vector<unsigned> getShuffleMask(const ShuffleVectorInst *SVI) {
9277 unsigned NElts = SVI->getType()->getNumElements();
9278 if (isa<ConstantAggregateZero>(SVI->getOperand(2)))
9279 return std::vector<unsigned>(NElts, 0);
9280 if (isa<UndefValue>(SVI->getOperand(2)))
9281 return std::vector<unsigned>(NElts, 2*NElts);
9283 std::vector<unsigned> Result;
9284 const ConstantVector *CP = cast<ConstantVector>(SVI->getOperand(2));
9285 for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
9286 if (isa<UndefValue>(CP->getOperand(i)))
9287 Result.push_back(NElts*2); // undef -> 8
9289 Result.push_back(cast<ConstantInt>(CP->getOperand(i))->getZExtValue());
9293 /// FindScalarElement - Given a vector and an element number, see if the scalar
9294 /// value is already around as a register, for example if it were inserted then
9295 /// extracted from the vector.
9296 static Value *FindScalarElement(Value *V, unsigned EltNo) {
9297 assert(isa<VectorType>(V->getType()) && "Not looking at a vector?");
9298 const VectorType *PTy = cast<VectorType>(V->getType());
9299 unsigned Width = PTy->getNumElements();
9300 if (EltNo >= Width) // Out of range access.
9301 return UndefValue::get(PTy->getElementType());
9303 if (isa<UndefValue>(V))
9304 return UndefValue::get(PTy->getElementType());
9305 else if (isa<ConstantAggregateZero>(V))
9306 return Constant::getNullValue(PTy->getElementType());
9307 else if (ConstantVector *CP = dyn_cast<ConstantVector>(V))
9308 return CP->getOperand(EltNo);
9309 else if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
9310 // If this is an insert to a variable element, we don't know what it is.
9311 if (!isa<ConstantInt>(III->getOperand(2)))
9313 unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
9315 // If this is an insert to the element we are looking for, return the
9318 return III->getOperand(1);
9320 // Otherwise, the insertelement doesn't modify the value, recurse on its
9322 return FindScalarElement(III->getOperand(0), EltNo);
9323 } else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
9324 unsigned InEl = getShuffleMask(SVI)[EltNo];
9326 return FindScalarElement(SVI->getOperand(0), InEl);
9327 else if (InEl < Width*2)
9328 return FindScalarElement(SVI->getOperand(1), InEl - Width);
9330 return UndefValue::get(PTy->getElementType());
9333 // Otherwise, we don't know.
9337 Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
9339 // If vector val is undef, replace extract with scalar undef.
9340 if (isa<UndefValue>(EI.getOperand(0)))
9341 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
9343 // If vector val is constant 0, replace extract with scalar 0.
9344 if (isa<ConstantAggregateZero>(EI.getOperand(0)))
9345 return ReplaceInstUsesWith(EI, Constant::getNullValue(EI.getType()));
9347 if (ConstantVector *C = dyn_cast<ConstantVector>(EI.getOperand(0))) {
9348 // If vector val is constant with uniform operands, replace EI
9349 // with that operand
9350 Constant *op0 = C->getOperand(0);
9351 for (unsigned i = 1; i < C->getNumOperands(); ++i)
9352 if (C->getOperand(i) != op0) {
9357 return ReplaceInstUsesWith(EI, op0);
9360 // If extracting a specified index from the vector, see if we can recursively
9361 // find a previously computed scalar that was inserted into the vector.
9362 if (ConstantInt *IdxC = dyn_cast<ConstantInt>(EI.getOperand(1))) {
9363 unsigned IndexVal = IdxC->getZExtValue();
9364 unsigned VectorWidth =
9365 cast<VectorType>(EI.getOperand(0)->getType())->getNumElements();
9367 // If this is extracting an invalid index, turn this into undef, to avoid
9368 // crashing the code below.
9369 if (IndexVal >= VectorWidth)
9370 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
9372 // This instruction only demands the single element from the input vector.
9373 // If the input vector has a single use, simplify it based on this use
9375 if (EI.getOperand(0)->hasOneUse() && VectorWidth != 1) {
9377 if (Value *V = SimplifyDemandedVectorElts(EI.getOperand(0),
9380 EI.setOperand(0, V);
9385 if (Value *Elt = FindScalarElement(EI.getOperand(0), IndexVal))
9386 return ReplaceInstUsesWith(EI, Elt);
9388 // If the this extractelement is directly using a bitcast from a vector of
9389 // the same number of elements, see if we can find the source element from
9390 // it. In this case, we will end up needing to bitcast the scalars.
9391 if (BitCastInst *BCI = dyn_cast<BitCastInst>(EI.getOperand(0))) {
9392 if (const VectorType *VT =
9393 dyn_cast<VectorType>(BCI->getOperand(0)->getType()))
9394 if (VT->getNumElements() == VectorWidth)
9395 if (Value *Elt = FindScalarElement(BCI->getOperand(0), IndexVal))
9396 return new BitCastInst(Elt, EI.getType());
9400 if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0))) {
9401 if (I->hasOneUse()) {
9402 // Push extractelement into predecessor operation if legal and
9403 // profitable to do so
9404 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
9405 bool isConstantElt = isa<ConstantInt>(EI.getOperand(1));
9406 if (CheapToScalarize(BO, isConstantElt)) {
9407 ExtractElementInst *newEI0 =
9408 new ExtractElementInst(BO->getOperand(0), EI.getOperand(1),
9409 EI.getName()+".lhs");
9410 ExtractElementInst *newEI1 =
9411 new ExtractElementInst(BO->getOperand(1), EI.getOperand(1),
9412 EI.getName()+".rhs");
9413 InsertNewInstBefore(newEI0, EI);
9414 InsertNewInstBefore(newEI1, EI);
9415 return BinaryOperator::create(BO->getOpcode(), newEI0, newEI1);
9417 } else if (isa<LoadInst>(I)) {
9418 Value *Ptr = InsertCastBefore(Instruction::BitCast, I->getOperand(0),
9419 PointerType::get(EI.getType()), EI);
9420 GetElementPtrInst *GEP =
9421 new GetElementPtrInst(Ptr, EI.getOperand(1), I->getName() + ".gep");
9422 InsertNewInstBefore(GEP, EI);
9423 return new LoadInst(GEP);
9426 if (InsertElementInst *IE = dyn_cast<InsertElementInst>(I)) {
9427 // Extracting the inserted element?
9428 if (IE->getOperand(2) == EI.getOperand(1))
9429 return ReplaceInstUsesWith(EI, IE->getOperand(1));
9430 // If the inserted and extracted elements are constants, they must not
9431 // be the same value, extract from the pre-inserted value instead.
9432 if (isa<Constant>(IE->getOperand(2)) &&
9433 isa<Constant>(EI.getOperand(1))) {
9434 AddUsesToWorkList(EI);
9435 EI.setOperand(0, IE->getOperand(0));
9438 } else if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(I)) {
9439 // If this is extracting an element from a shufflevector, figure out where
9440 // it came from and extract from the appropriate input element instead.
9441 if (ConstantInt *Elt = dyn_cast<ConstantInt>(EI.getOperand(1))) {
9442 unsigned SrcIdx = getShuffleMask(SVI)[Elt->getZExtValue()];
9444 if (SrcIdx < SVI->getType()->getNumElements())
9445 Src = SVI->getOperand(0);
9446 else if (SrcIdx < SVI->getType()->getNumElements()*2) {
9447 SrcIdx -= SVI->getType()->getNumElements();
9448 Src = SVI->getOperand(1);
9450 return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
9452 return new ExtractElementInst(Src, SrcIdx);
9459 /// CollectSingleShuffleElements - If V is a shuffle of values that ONLY returns
9460 /// elements from either LHS or RHS, return the shuffle mask and true.
9461 /// Otherwise, return false.
9462 static bool CollectSingleShuffleElements(Value *V, Value *LHS, Value *RHS,
9463 std::vector<Constant*> &Mask) {
9464 assert(V->getType() == LHS->getType() && V->getType() == RHS->getType() &&
9465 "Invalid CollectSingleShuffleElements");
9466 unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
9468 if (isa<UndefValue>(V)) {
9469 Mask.assign(NumElts, UndefValue::get(Type::Int32Ty));
9471 } else if (V == LHS) {
9472 for (unsigned i = 0; i != NumElts; ++i)
9473 Mask.push_back(ConstantInt::get(Type::Int32Ty, i));
9475 } else if (V == RHS) {
9476 for (unsigned i = 0; i != NumElts; ++i)
9477 Mask.push_back(ConstantInt::get(Type::Int32Ty, i+NumElts));
9479 } else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
9480 // If this is an insert of an extract from some other vector, include it.
9481 Value *VecOp = IEI->getOperand(0);
9482 Value *ScalarOp = IEI->getOperand(1);
9483 Value *IdxOp = IEI->getOperand(2);
9485 if (!isa<ConstantInt>(IdxOp))
9487 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
9489 if (isa<UndefValue>(ScalarOp)) { // inserting undef into vector.
9490 // Okay, we can handle this if the vector we are insertinting into is
9492 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
9493 // If so, update the mask to reflect the inserted undef.
9494 Mask[InsertedIdx] = UndefValue::get(Type::Int32Ty);
9497 } else if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)){
9498 if (isa<ConstantInt>(EI->getOperand(1)) &&
9499 EI->getOperand(0)->getType() == V->getType()) {
9500 unsigned ExtractedIdx =
9501 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
9503 // This must be extracting from either LHS or RHS.
9504 if (EI->getOperand(0) == LHS || EI->getOperand(0) == RHS) {
9505 // Okay, we can handle this if the vector we are insertinting into is
9507 if (CollectSingleShuffleElements(VecOp, LHS, RHS, Mask)) {
9508 // If so, update the mask to reflect the inserted value.
9509 if (EI->getOperand(0) == LHS) {
9510 Mask[InsertedIdx & (NumElts-1)] =
9511 ConstantInt::get(Type::Int32Ty, ExtractedIdx);
9513 assert(EI->getOperand(0) == RHS);
9514 Mask[InsertedIdx & (NumElts-1)] =
9515 ConstantInt::get(Type::Int32Ty, ExtractedIdx+NumElts);
9524 // TODO: Handle shufflevector here!
9529 /// CollectShuffleElements - We are building a shuffle of V, using RHS as the
9530 /// RHS of the shuffle instruction, if it is not null. Return a shuffle mask
9531 /// that computes V and the LHS value of the shuffle.
9532 static Value *CollectShuffleElements(Value *V, std::vector<Constant*> &Mask,
9534 assert(isa<VectorType>(V->getType()) &&
9535 (RHS == 0 || V->getType() == RHS->getType()) &&
9536 "Invalid shuffle!");
9537 unsigned NumElts = cast<VectorType>(V->getType())->getNumElements();
9539 if (isa<UndefValue>(V)) {
9540 Mask.assign(NumElts, UndefValue::get(Type::Int32Ty));
9542 } else if (isa<ConstantAggregateZero>(V)) {
9543 Mask.assign(NumElts, ConstantInt::get(Type::Int32Ty, 0));
9545 } else if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(V)) {
9546 // If this is an insert of an extract from some other vector, include it.
9547 Value *VecOp = IEI->getOperand(0);
9548 Value *ScalarOp = IEI->getOperand(1);
9549 Value *IdxOp = IEI->getOperand(2);
9551 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
9552 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
9553 EI->getOperand(0)->getType() == V->getType()) {
9554 unsigned ExtractedIdx =
9555 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
9556 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
9558 // Either the extracted from or inserted into vector must be RHSVec,
9559 // otherwise we'd end up with a shuffle of three inputs.
9560 if (EI->getOperand(0) == RHS || RHS == 0) {
9561 RHS = EI->getOperand(0);
9562 Value *V = CollectShuffleElements(VecOp, Mask, RHS);
9563 Mask[InsertedIdx & (NumElts-1)] =
9564 ConstantInt::get(Type::Int32Ty, NumElts+ExtractedIdx);
9569 Value *V = CollectShuffleElements(EI->getOperand(0), Mask, RHS);
9570 // Everything but the extracted element is replaced with the RHS.
9571 for (unsigned i = 0; i != NumElts; ++i) {
9572 if (i != InsertedIdx)
9573 Mask[i] = ConstantInt::get(Type::Int32Ty, NumElts+i);
9578 // If this insertelement is a chain that comes from exactly these two
9579 // vectors, return the vector and the effective shuffle.
9580 if (CollectSingleShuffleElements(IEI, EI->getOperand(0), RHS, Mask))
9581 return EI->getOperand(0);
9586 // TODO: Handle shufflevector here!
9588 // Otherwise, can't do anything fancy. Return an identity vector.
9589 for (unsigned i = 0; i != NumElts; ++i)
9590 Mask.push_back(ConstantInt::get(Type::Int32Ty, i));
9594 Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
9595 Value *VecOp = IE.getOperand(0);
9596 Value *ScalarOp = IE.getOperand(1);
9597 Value *IdxOp = IE.getOperand(2);
9599 // Inserting an undef or into an undefined place, remove this.
9600 if (isa<UndefValue>(ScalarOp) || isa<UndefValue>(IdxOp))
9601 ReplaceInstUsesWith(IE, VecOp);
9603 // If the inserted element was extracted from some other vector, and if the
9604 // indexes are constant, try to turn this into a shufflevector operation.
9605 if (ExtractElementInst *EI = dyn_cast<ExtractElementInst>(ScalarOp)) {
9606 if (isa<ConstantInt>(EI->getOperand(1)) && isa<ConstantInt>(IdxOp) &&
9607 EI->getOperand(0)->getType() == IE.getType()) {
9608 unsigned NumVectorElts = IE.getType()->getNumElements();
9609 unsigned ExtractedIdx =
9610 cast<ConstantInt>(EI->getOperand(1))->getZExtValue();
9611 unsigned InsertedIdx = cast<ConstantInt>(IdxOp)->getZExtValue();
9613 if (ExtractedIdx >= NumVectorElts) // Out of range extract.
9614 return ReplaceInstUsesWith(IE, VecOp);
9616 if (InsertedIdx >= NumVectorElts) // Out of range insert.
9617 return ReplaceInstUsesWith(IE, UndefValue::get(IE.getType()));
9619 // If we are extracting a value from a vector, then inserting it right
9620 // back into the same place, just use the input vector.
9621 if (EI->getOperand(0) == VecOp && ExtractedIdx == InsertedIdx)
9622 return ReplaceInstUsesWith(IE, VecOp);
9624 // We could theoretically do this for ANY input. However, doing so could
9625 // turn chains of insertelement instructions into a chain of shufflevector
9626 // instructions, and right now we do not merge shufflevectors. As such,
9627 // only do this in a situation where it is clear that there is benefit.
9628 if (isa<UndefValue>(VecOp) || isa<ConstantAggregateZero>(VecOp)) {
9629 // Turn this into shuffle(EIOp0, VecOp, Mask). The result has all of
9630 // the values of VecOp, except then one read from EIOp0.
9631 // Build a new shuffle mask.
9632 std::vector<Constant*> Mask;
9633 if (isa<UndefValue>(VecOp))
9634 Mask.assign(NumVectorElts, UndefValue::get(Type::Int32Ty));
9636 assert(isa<ConstantAggregateZero>(VecOp) && "Unknown thing");
9637 Mask.assign(NumVectorElts, ConstantInt::get(Type::Int32Ty,
9640 Mask[InsertedIdx] = ConstantInt::get(Type::Int32Ty, ExtractedIdx);
9641 return new ShuffleVectorInst(EI->getOperand(0), VecOp,
9642 ConstantVector::get(Mask));
9645 // If this insertelement isn't used by some other insertelement, turn it
9646 // (and any insertelements it points to), into one big shuffle.
9647 if (!IE.hasOneUse() || !isa<InsertElementInst>(IE.use_back())) {
9648 std::vector<Constant*> Mask;
9650 Value *LHS = CollectShuffleElements(&IE, Mask, RHS);
9651 if (RHS == 0) RHS = UndefValue::get(LHS->getType());
9652 // We now have a shuffle of LHS, RHS, Mask.
9653 return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Mask));
9662 Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) {
9663 Value *LHS = SVI.getOperand(0);
9664 Value *RHS = SVI.getOperand(1);
9665 std::vector<unsigned> Mask = getShuffleMask(&SVI);
9667 bool MadeChange = false;
9669 // Undefined shuffle mask -> undefined value.
9670 if (isa<UndefValue>(SVI.getOperand(2)))
9671 return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType()));
9673 // If we have shuffle(x, undef, mask) and any elements of mask refer to
9674 // the undef, change them to undefs.
9675 if (isa<UndefValue>(SVI.getOperand(1))) {
9676 // Scan to see if there are any references to the RHS. If so, replace them
9677 // with undef element refs and set MadeChange to true.
9678 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
9679 if (Mask[i] >= e && Mask[i] != 2*e) {
9686 // Remap any references to RHS to use LHS.
9687 std::vector<Constant*> Elts;
9688 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
9690 Elts.push_back(UndefValue::get(Type::Int32Ty));
9692 Elts.push_back(ConstantInt::get(Type::Int32Ty, Mask[i]));
9694 SVI.setOperand(2, ConstantVector::get(Elts));
9698 // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask')
9699 // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask').
9700 if (LHS == RHS || isa<UndefValue>(LHS)) {
9701 if (isa<UndefValue>(LHS) && LHS == RHS) {
9702 // shuffle(undef,undef,mask) -> undef.
9703 return ReplaceInstUsesWith(SVI, LHS);
9706 // Remap any references to RHS to use LHS.
9707 std::vector<Constant*> Elts;
9708 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
9710 Elts.push_back(UndefValue::get(Type::Int32Ty));
9712 if ((Mask[i] >= e && isa<UndefValue>(RHS)) ||
9713 (Mask[i] < e && isa<UndefValue>(LHS)))
9714 Mask[i] = 2*e; // Turn into undef.
9716 Mask[i] &= (e-1); // Force to LHS.
9717 Elts.push_back(ConstantInt::get(Type::Int32Ty, Mask[i]));
9720 SVI.setOperand(0, SVI.getOperand(1));
9721 SVI.setOperand(1, UndefValue::get(RHS->getType()));
9722 SVI.setOperand(2, ConstantVector::get(Elts));
9723 LHS = SVI.getOperand(0);
9724 RHS = SVI.getOperand(1);
9728 // Analyze the shuffle, are the LHS or RHS and identity shuffles?
9729 bool isLHSID = true, isRHSID = true;
9731 for (unsigned i = 0, e = Mask.size(); i != e; ++i) {
9732 if (Mask[i] >= e*2) continue; // Ignore undef values.
9733 // Is this an identity shuffle of the LHS value?
9734 isLHSID &= (Mask[i] == i);
9736 // Is this an identity shuffle of the RHS value?
9737 isRHSID &= (Mask[i]-e == i);
9740 // Eliminate identity shuffles.
9741 if (isLHSID) return ReplaceInstUsesWith(SVI, LHS);
9742 if (isRHSID) return ReplaceInstUsesWith(SVI, RHS);
9744 // If the LHS is a shufflevector itself, see if we can combine it with this
9745 // one without producing an unusual shuffle. Here we are really conservative:
9746 // we are absolutely afraid of producing a shuffle mask not in the input
9747 // program, because the code gen may not be smart enough to turn a merged
9748 // shuffle into two specific shuffles: it may produce worse code. As such,
9749 // we only merge two shuffles if the result is one of the two input shuffle
9750 // masks. In this case, merging the shuffles just removes one instruction,
9751 // which we know is safe. This is good for things like turning:
9752 // (splat(splat)) -> splat.
9753 if (ShuffleVectorInst *LHSSVI = dyn_cast<ShuffleVectorInst>(LHS)) {
9754 if (isa<UndefValue>(RHS)) {
9755 std::vector<unsigned> LHSMask = getShuffleMask(LHSSVI);
9757 std::vector<unsigned> NewMask;
9758 for (unsigned i = 0, e = Mask.size(); i != e; ++i)
9760 NewMask.push_back(2*e);
9762 NewMask.push_back(LHSMask[Mask[i]]);
9764 // If the result mask is equal to the src shuffle or this shuffle mask, do
9766 if (NewMask == LHSMask || NewMask == Mask) {
9767 std::vector<Constant*> Elts;
9768 for (unsigned i = 0, e = NewMask.size(); i != e; ++i) {
9769 if (NewMask[i] >= e*2) {
9770 Elts.push_back(UndefValue::get(Type::Int32Ty));
9772 Elts.push_back(ConstantInt::get(Type::Int32Ty, NewMask[i]));
9775 return new ShuffleVectorInst(LHSSVI->getOperand(0),
9776 LHSSVI->getOperand(1),
9777 ConstantVector::get(Elts));
9782 return MadeChange ? &SVI : 0;
9788 /// TryToSinkInstruction - Try to move the specified instruction from its
9789 /// current block into the beginning of DestBlock, which can only happen if it's
9790 /// safe to move the instruction past all of the instructions between it and the
9791 /// end of its block.
9792 static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
9793 assert(I->hasOneUse() && "Invariants didn't hold!");
9795 // Cannot move control-flow-involving, volatile loads, vaarg, etc.
9796 if (isa<PHINode>(I) || I->mayWriteToMemory()) return false;
9798 // Do not sink alloca instructions out of the entry block.
9799 if (isa<AllocaInst>(I) && I->getParent() ==
9800 &DestBlock->getParent()->getEntryBlock())
9803 // We can only sink load instructions if there is nothing between the load and
9804 // the end of block that could change the value.
9805 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
9806 for (BasicBlock::iterator Scan = LI, E = LI->getParent()->end();
9808 if (Scan->mayWriteToMemory())
9812 BasicBlock::iterator InsertPos = DestBlock->begin();
9813 while (isa<PHINode>(InsertPos)) ++InsertPos;
9815 I->moveBefore(InsertPos);
9821 /// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
9822 /// all reachable code to the worklist.
9824 /// This has a couple of tricks to make the code faster and more powerful. In
9825 /// particular, we constant fold and DCE instructions as we go, to avoid adding
9826 /// them to the worklist (this significantly speeds up instcombine on code where
9827 /// many instructions are dead or constant). Additionally, if we find a branch
9828 /// whose condition is a known constant, we only visit the reachable successors.
9830 static void AddReachableCodeToWorklist(BasicBlock *BB,
9831 SmallPtrSet<BasicBlock*, 64> &Visited,
9833 const TargetData *TD) {
9834 std::vector<BasicBlock*> Worklist;
9835 Worklist.push_back(BB);
9837 while (!Worklist.empty()) {
9838 BB = Worklist.back();
9839 Worklist.pop_back();
9841 // We have now visited this block! If we've already been here, ignore it.
9842 if (!Visited.insert(BB)) continue;
9844 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
9845 Instruction *Inst = BBI++;
9847 // DCE instruction if trivially dead.
9848 if (isInstructionTriviallyDead(Inst)) {
9850 DOUT << "IC: DCE: " << *Inst;
9851 Inst->eraseFromParent();
9855 // ConstantProp instruction if trivially constant.
9856 if (Constant *C = ConstantFoldInstruction(Inst, TD)) {
9857 DOUT << "IC: ConstFold to: " << *C << " from: " << *Inst;
9858 Inst->replaceAllUsesWith(C);
9860 Inst->eraseFromParent();
9864 IC.AddToWorkList(Inst);
9867 // Recursively visit successors. If this is a branch or switch on a
9868 // constant, only visit the reachable successor.
9869 TerminatorInst *TI = BB->getTerminator();
9870 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
9871 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
9872 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
9873 Worklist.push_back(BI->getSuccessor(!CondVal));
9876 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
9877 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
9878 // See if this is an explicit destination.
9879 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i)
9880 if (SI->getCaseValue(i) == Cond) {
9881 Worklist.push_back(SI->getSuccessor(i));
9885 // Otherwise it is the default destination.
9886 Worklist.push_back(SI->getSuccessor(0));
9891 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
9892 Worklist.push_back(TI->getSuccessor(i));
9896 bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
9897 bool Changed = false;
9898 TD = &getAnalysis<TargetData>();
9900 DEBUG(DOUT << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
9901 << F.getNameStr() << "\n");
9904 // Do a depth-first traversal of the function, populate the worklist with
9905 // the reachable instructions. Ignore blocks that are not reachable. Keep
9906 // track of which blocks we visit.
9907 SmallPtrSet<BasicBlock*, 64> Visited;
9908 AddReachableCodeToWorklist(F.begin(), Visited, *this, TD);
9910 // Do a quick scan over the function. If we find any blocks that are
9911 // unreachable, remove any instructions inside of them. This prevents
9912 // the instcombine code from having to deal with some bad special cases.
9913 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
9914 if (!Visited.count(BB)) {
9915 Instruction *Term = BB->getTerminator();
9916 while (Term != BB->begin()) { // Remove instrs bottom-up
9917 BasicBlock::iterator I = Term; --I;
9919 DOUT << "IC: DCE: " << *I;
9922 if (!I->use_empty())
9923 I->replaceAllUsesWith(UndefValue::get(I->getType()));
9924 I->eraseFromParent();
9929 while (!Worklist.empty()) {
9930 Instruction *I = RemoveOneFromWorkList();
9931 if (I == 0) continue; // skip null values.
9933 // Check to see if we can DCE the instruction.
9934 if (isInstructionTriviallyDead(I)) {
9935 // Add operands to the worklist.
9936 if (I->getNumOperands() < 4)
9937 AddUsesToWorkList(*I);
9940 DOUT << "IC: DCE: " << *I;
9942 I->eraseFromParent();
9943 RemoveFromWorkList(I);
9947 // Instruction isn't dead, see if we can constant propagate it.
9948 if (Constant *C = ConstantFoldInstruction(I, TD)) {
9949 DOUT << "IC: ConstFold to: " << *C << " from: " << *I;
9951 // Add operands to the worklist.
9952 AddUsesToWorkList(*I);
9953 ReplaceInstUsesWith(*I, C);
9956 I->eraseFromParent();
9957 RemoveFromWorkList(I);
9961 // See if we can trivially sink this instruction to a successor basic block.
9962 if (I->hasOneUse()) {
9963 BasicBlock *BB = I->getParent();
9964 BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
9965 if (UserParent != BB) {
9966 bool UserIsSuccessor = false;
9967 // See if the user is one of our successors.
9968 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
9969 if (*SI == UserParent) {
9970 UserIsSuccessor = true;
9974 // If the user is one of our immediate successors, and if that successor
9975 // only has us as a predecessors (we'd have to split the critical edge
9976 // otherwise), we can keep going.
9977 if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
9978 next(pred_begin(UserParent)) == pred_end(UserParent))
9979 // Okay, the CFG is simple enough, try to sink this instruction.
9980 Changed |= TryToSinkInstruction(I, UserParent);
9984 // Now that we have an instruction, try combining it to simplify it...
9988 DEBUG(std::ostringstream SS; I->print(SS); OrigI = SS.str(););
9989 if (Instruction *Result = visit(*I)) {
9991 // Should we replace the old instruction with a new one?
9993 DOUT << "IC: Old = " << *I
9994 << " New = " << *Result;
9996 // Everything uses the new instruction now.
9997 I->replaceAllUsesWith(Result);
9999 // Push the new instruction and any users onto the worklist.
10000 AddToWorkList(Result);
10001 AddUsersToWorkList(*Result);
10003 // Move the name to the new instruction first.
10004 Result->takeName(I);
10006 // Insert the new instruction into the basic block...
10007 BasicBlock *InstParent = I->getParent();
10008 BasicBlock::iterator InsertPos = I;
10010 if (!isa<PHINode>(Result)) // If combining a PHI, don't insert
10011 while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
10014 InstParent->getInstList().insert(InsertPos, Result);
10016 // Make sure that we reprocess all operands now that we reduced their
10018 AddUsesToWorkList(*I);
10020 // Instructions can end up on the worklist more than once. Make sure
10021 // we do not process an instruction that has been deleted.
10022 RemoveFromWorkList(I);
10024 // Erase the old instruction.
10025 InstParent->getInstList().erase(I);
10028 DOUT << "IC: Mod = " << OrigI
10029 << " New = " << *I;
10032 // If the instruction was modified, it's possible that it is now dead.
10033 // if so, remove it.
10034 if (isInstructionTriviallyDead(I)) {
10035 // Make sure we process all operands now that we are reducing their
10037 AddUsesToWorkList(*I);
10039 // Instructions may end up in the worklist more than once. Erase all
10040 // occurrences of this instruction.
10041 RemoveFromWorkList(I);
10042 I->eraseFromParent();
10045 AddUsersToWorkList(*I);
10052 assert(WorklistMap.empty() && "Worklist empty, but map not?");
10054 // Do an explicit clear, this shrinks the map if needed.
10055 WorklistMap.clear();
10060 bool InstCombiner::runOnFunction(Function &F) {
10061 MustPreserveLCSSA = mustPreserveAnalysisID(LCSSAID);
10063 bool EverMadeChange = false;
10065 // Iterate while there is work to do.
10066 unsigned Iteration = 0;
10067 while (DoOneIteration(F, Iteration++))
10068 EverMadeChange = true;
10069 return EverMadeChange;
10072 FunctionPass *llvm::createInstructionCombiningPass() {
10073 return new InstCombiner();