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. SetCC instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All SetCC 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
32 // N. This list is incomplete
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/Instructions.h"
39 #include "llvm/Intrinsics.h"
40 #include "llvm/Pass.h"
41 #include "llvm/Constants.h"
42 #include "llvm/DerivedTypes.h"
43 #include "llvm/GlobalVariable.h"
44 #include "llvm/Target/TargetData.h"
45 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
46 #include "llvm/Transforms/Utils/Local.h"
47 #include "llvm/Support/CallSite.h"
48 #include "llvm/Support/GetElementPtrTypeIterator.h"
49 #include "llvm/Support/InstIterator.h"
50 #include "llvm/Support/InstVisitor.h"
51 #include "Support/Debug.h"
52 #include "Support/Statistic.h"
57 Statistic<> NumCombined ("instcombine", "Number of insts combined");
58 Statistic<> NumConstProp("instcombine", "Number of constant folds");
59 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
61 class InstCombiner : public FunctionPass,
62 public InstVisitor<InstCombiner, Instruction*> {
63 // Worklist of all of the instructions that need to be simplified.
64 std::vector<Instruction*> WorkList;
67 /// AddUsersToWorkList - When an instruction is simplified, add all users of
68 /// the instruction to the work lists because they might get more simplified
71 void AddUsersToWorkList(Instruction &I) {
72 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
74 WorkList.push_back(cast<Instruction>(*UI));
77 /// AddUsesToWorkList - When an instruction is simplified, add operands to
78 /// the work lists because they might get more simplified now.
80 void AddUsesToWorkList(Instruction &I) {
81 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
82 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
83 WorkList.push_back(Op);
86 // removeFromWorkList - remove all instances of I from the worklist.
87 void removeFromWorkList(Instruction *I);
89 virtual bool runOnFunction(Function &F);
91 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
92 AU.addRequired<TargetData>();
96 TargetData &getTargetData() const { return *TD; }
98 // Visitation implementation - Implement instruction combining for different
99 // instruction types. The semantics are as follows:
101 // null - No change was made
102 // I - Change was made, I is still valid, I may be dead though
103 // otherwise - Change was made, replace I with returned instruction
105 Instruction *visitAdd(BinaryOperator &I);
106 Instruction *visitSub(BinaryOperator &I);
107 Instruction *visitMul(BinaryOperator &I);
108 Instruction *visitDiv(BinaryOperator &I);
109 Instruction *visitRem(BinaryOperator &I);
110 Instruction *visitAnd(BinaryOperator &I);
111 Instruction *visitOr (BinaryOperator &I);
112 Instruction *visitXor(BinaryOperator &I);
113 Instruction *visitSetCondInst(BinaryOperator &I);
114 Instruction *visitShiftInst(ShiftInst &I);
115 Instruction *visitCastInst(CastInst &CI);
116 Instruction *visitSelectInst(SelectInst &CI);
117 Instruction *visitCallInst(CallInst &CI);
118 Instruction *visitInvokeInst(InvokeInst &II);
119 Instruction *visitPHINode(PHINode &PN);
120 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
121 Instruction *visitAllocationInst(AllocationInst &AI);
122 Instruction *visitFreeInst(FreeInst &FI);
123 Instruction *visitLoadInst(LoadInst &LI);
124 Instruction *visitBranchInst(BranchInst &BI);
126 // visitInstruction - Specify what to return for unhandled instructions...
127 Instruction *visitInstruction(Instruction &I) { return 0; }
130 Instruction *visitCallSite(CallSite CS);
131 bool transformConstExprCastCall(CallSite CS);
134 // InsertNewInstBefore - insert an instruction New before instruction Old
135 // in the program. Add the new instruction to the worklist.
137 Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
138 assert(New && New->getParent() == 0 &&
139 "New instruction already inserted into a basic block!");
140 BasicBlock *BB = Old.getParent();
141 BB->getInstList().insert(&Old, New); // Insert inst
142 WorkList.push_back(New); // Add to worklist
146 // ReplaceInstUsesWith - This method is to be used when an instruction is
147 // found to be dead, replacable with another preexisting expression. Here
148 // we add all uses of I to the worklist, replace all uses of I with the new
149 // value, then return I, so that the inst combiner will know that I was
152 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
153 AddUsersToWorkList(I); // Add all modified instrs to worklist
155 I.replaceAllUsesWith(V);
158 // If we are replacing the instruction with itself, this must be in a
159 // segment of unreachable code, so just clobber the instruction.
160 I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
165 // EraseInstFromFunction - When dealing with an instruction that has side
166 // effects or produces a void value, we can't rely on DCE to delete the
167 // instruction. Instead, visit methods should return the value returned by
169 Instruction *EraseInstFromFunction(Instruction &I) {
170 assert(I.use_empty() && "Cannot erase instruction that is used!");
171 AddUsesToWorkList(I);
172 removeFromWorkList(&I);
173 I.getParent()->getInstList().erase(&I);
174 return 0; // Don't do anything with FI
179 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
180 /// InsertBefore instruction. This is specialized a bit to avoid inserting
181 /// casts that are known to not do anything...
183 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
184 Instruction *InsertBefore);
186 // SimplifyCommutative - This performs a few simplifications for commutative
188 bool SimplifyCommutative(BinaryOperator &I);
190 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
191 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
194 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
197 // getComplexity: Assign a complexity or rank value to LLVM Values...
198 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
199 static unsigned getComplexity(Value *V) {
200 if (isa<Instruction>(V)) {
201 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
205 if (isa<Argument>(V)) return 2;
206 return isa<Constant>(V) ? 0 : 1;
209 // isOnlyUse - Return true if this instruction will be deleted if we stop using
211 static bool isOnlyUse(Value *V) {
212 return V->hasOneUse() || isa<Constant>(V);
215 // getSignedIntegralType - Given an unsigned integral type, return the signed
216 // version of it that has the same size.
217 static const Type *getSignedIntegralType(const Type *Ty) {
218 switch (Ty->getPrimitiveID()) {
219 default: assert(0 && "Invalid unsigned integer type!"); abort();
220 case Type::UByteTyID: return Type::SByteTy;
221 case Type::UShortTyID: return Type::ShortTy;
222 case Type::UIntTyID: return Type::IntTy;
223 case Type::ULongTyID: return Type::LongTy;
227 // getUnsignedIntegralType - Given an signed integral type, return the unsigned
228 // version of it that has the same size.
229 static const Type *getUnsignedIntegralType(const Type *Ty) {
230 switch (Ty->getPrimitiveID()) {
231 default: assert(0 && "Invalid signed integer type!"); abort();
232 case Type::SByteTyID: return Type::UByteTy;
233 case Type::ShortTyID: return Type::UShortTy;
234 case Type::IntTyID: return Type::UIntTy;
235 case Type::LongTyID: return Type::ULongTy;
239 // getPromotedType - Return the specified type promoted as it would be to pass
240 // though a va_arg area...
241 static const Type *getPromotedType(const Type *Ty) {
242 switch (Ty->getPrimitiveID()) {
243 case Type::SByteTyID:
244 case Type::ShortTyID: return Type::IntTy;
245 case Type::UByteTyID:
246 case Type::UShortTyID: return Type::UIntTy;
247 case Type::FloatTyID: return Type::DoubleTy;
252 // SimplifyCommutative - This performs a few simplifications for commutative
255 // 1. Order operands such that they are listed from right (least complex) to
256 // left (most complex). This puts constants before unary operators before
259 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
260 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
262 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
263 bool Changed = false;
264 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
265 Changed = !I.swapOperands();
267 if (!I.isAssociative()) return Changed;
268 Instruction::BinaryOps Opcode = I.getOpcode();
269 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
270 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
271 if (isa<Constant>(I.getOperand(1))) {
272 Constant *Folded = ConstantExpr::get(I.getOpcode(),
273 cast<Constant>(I.getOperand(1)),
274 cast<Constant>(Op->getOperand(1)));
275 I.setOperand(0, Op->getOperand(0));
276 I.setOperand(1, Folded);
278 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
279 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
280 isOnlyUse(Op) && isOnlyUse(Op1)) {
281 Constant *C1 = cast<Constant>(Op->getOperand(1));
282 Constant *C2 = cast<Constant>(Op1->getOperand(1));
284 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
285 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
286 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
289 WorkList.push_back(New);
290 I.setOperand(0, New);
291 I.setOperand(1, Folded);
298 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
299 // if the LHS is a constant zero (which is the 'negate' form).
301 static inline Value *dyn_castNegVal(Value *V) {
302 if (BinaryOperator::isNeg(V))
303 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
305 // Constants can be considered to be negated values if they can be folded...
306 if (Constant *C = dyn_cast<Constant>(V))
307 return ConstantExpr::get(Instruction::Sub,
308 Constant::getNullValue(V->getType()), C);
312 static Constant *NotConstant(Constant *C) {
313 return ConstantExpr::get(Instruction::Xor, C,
314 ConstantIntegral::getAllOnesValue(C->getType()));
317 static inline Value *dyn_castNotVal(Value *V) {
318 if (BinaryOperator::isNot(V))
319 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
321 // Constants can be considered to be not'ed values...
322 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
323 return NotConstant(C);
327 // dyn_castFoldableMul - If this value is a multiply that can be folded into
328 // other computations (because it has a constant operand), return the
329 // non-constant operand of the multiply.
331 static inline Value *dyn_castFoldableMul(Value *V) {
332 if (V->hasOneUse() && V->getType()->isInteger())
333 if (Instruction *I = dyn_cast<Instruction>(V))
334 if (I->getOpcode() == Instruction::Mul)
335 if (isa<Constant>(I->getOperand(1)))
336 return I->getOperand(0);
340 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
341 // a constant, return the constant being anded with.
343 template<class ValueType>
344 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
345 if (Instruction *I = dyn_cast<Instruction>(V))
346 if (I->getOpcode() == Instruction::And)
347 return dyn_cast<Constant>(I->getOperand(1));
349 // If this is a constant, it acts just like we were masking with it.
350 return dyn_cast<Constant>(V);
353 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
355 static unsigned Log2(uint64_t Val) {
356 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
359 if (Val & 1) return 0; // Multiple bits set?
367 /// AssociativeOpt - Perform an optimization on an associative operator. This
368 /// function is designed to check a chain of associative operators for a
369 /// potential to apply a certain optimization. Since the optimization may be
370 /// applicable if the expression was reassociated, this checks the chain, then
371 /// reassociates the expression as necessary to expose the optimization
372 /// opportunity. This makes use of a special Functor, which must define
373 /// 'shouldApply' and 'apply' methods.
375 template<typename Functor>
376 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
377 unsigned Opcode = Root.getOpcode();
378 Value *LHS = Root.getOperand(0);
380 // Quick check, see if the immediate LHS matches...
381 if (F.shouldApply(LHS))
382 return F.apply(Root);
384 // Otherwise, if the LHS is not of the same opcode as the root, return.
385 Instruction *LHSI = dyn_cast<Instruction>(LHS);
386 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
387 // Should we apply this transform to the RHS?
388 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
390 // If not to the RHS, check to see if we should apply to the LHS...
391 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
392 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
396 // If the functor wants to apply the optimization to the RHS of LHSI,
397 // reassociate the expression from ((? op A) op B) to (? op (A op B))
399 BasicBlock *BB = Root.getParent();
401 // Now all of the instructions are in the current basic block, go ahead
402 // and perform the reassociation.
403 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
405 // First move the selected RHS to the LHS of the root...
406 Root.setOperand(0, LHSI->getOperand(1));
408 // Make what used to be the LHS of the root be the user of the root...
409 Value *ExtraOperand = TmpLHSI->getOperand(1);
410 if (&Root == TmpLHSI) {
411 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
414 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
415 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
416 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
417 BasicBlock::iterator ARI = &Root; ++ARI;
418 BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
421 // Now propagate the ExtraOperand down the chain of instructions until we
423 while (TmpLHSI != LHSI) {
424 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
425 // Move the instruction to immediately before the chain we are
426 // constructing to avoid breaking dominance properties.
427 NextLHSI->getParent()->getInstList().remove(NextLHSI);
428 BB->getInstList().insert(ARI, NextLHSI);
431 Value *NextOp = NextLHSI->getOperand(1);
432 NextLHSI->setOperand(1, ExtraOperand);
434 ExtraOperand = NextOp;
437 // Now that the instructions are reassociated, have the functor perform
438 // the transformation...
439 return F.apply(Root);
442 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
448 // AddRHS - Implements: X + X --> X << 1
451 AddRHS(Value *rhs) : RHS(rhs) {}
452 bool shouldApply(Value *LHS) const { return LHS == RHS; }
453 Instruction *apply(BinaryOperator &Add) const {
454 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
455 ConstantInt::get(Type::UByteTy, 1));
459 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
461 struct AddMaskingAnd {
463 AddMaskingAnd(Constant *c) : C2(c) {}
464 bool shouldApply(Value *LHS) const {
465 if (Constant *C1 = dyn_castMaskingAnd(LHS))
466 return ConstantExpr::get(Instruction::And, C1, C2)->isNullValue();
469 Instruction *apply(BinaryOperator &Add) const {
470 return BinaryOperator::create(Instruction::Or, Add.getOperand(0),
475 static Value *FoldOperationIntoSelectOperand(Instruction &BI, Value *SO,
477 // Figure out if the constant is the left or the right argument.
478 bool ConstIsRHS = isa<Constant>(BI.getOperand(1));
479 Constant *ConstOperand = cast<Constant>(BI.getOperand(ConstIsRHS));
481 if (Constant *SOC = dyn_cast<Constant>(SO)) {
483 return ConstantExpr::get(BI.getOpcode(), SOC, ConstOperand);
484 return ConstantExpr::get(BI.getOpcode(), ConstOperand, SOC);
487 Value *Op0 = SO, *Op1 = ConstOperand;
491 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&BI))
492 New = BinaryOperator::create(BO->getOpcode(), Op0, Op1);
493 else if (ShiftInst *SI = dyn_cast<ShiftInst>(&BI))
494 New = new ShiftInst(SI->getOpcode(), Op0, Op1);
496 assert(0 && "Unknown binary instruction type!");
499 return IC->InsertNewInstBefore(New, BI);
502 // FoldBinOpIntoSelect - Given an instruction with a select as one operand and a
503 // constant as the other operand, try to fold the binary operator into the
505 static Instruction *FoldBinOpIntoSelect(Instruction &BI, SelectInst *SI,
507 // Don't modify shared select instructions
508 if (!SI->hasOneUse()) return 0;
509 Value *TV = SI->getOperand(1);
510 Value *FV = SI->getOperand(2);
512 if (isa<Constant>(TV) || isa<Constant>(FV)) {
513 Value *SelectTrueVal = FoldOperationIntoSelectOperand(BI, TV, IC);
514 Value *SelectFalseVal = FoldOperationIntoSelectOperand(BI, FV, IC);
516 return new SelectInst(SI->getCondition(), SelectTrueVal,
522 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
523 bool Changed = SimplifyCommutative(I);
524 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
526 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
528 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
530 return ReplaceInstUsesWith(I, LHS);
532 // X + (signbit) --> X ^ signbit
533 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
534 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
535 uint64_t Val = CI->getRawValue() & (1ULL << NumBits)-1;
536 if (Val == (1ULL << NumBits-1))
537 return BinaryOperator::create(Instruction::Xor, LHS, RHS);
542 if (I.getType()->isInteger())
543 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
546 if (Value *V = dyn_castNegVal(LHS))
547 return BinaryOperator::create(Instruction::Sub, RHS, V);
550 if (!isa<Constant>(RHS))
551 if (Value *V = dyn_castNegVal(RHS))
552 return BinaryOperator::create(Instruction::Sub, LHS, V);
554 // X*C + X --> X * (C+1)
555 if (dyn_castFoldableMul(LHS) == RHS) {
557 ConstantExpr::get(Instruction::Add,
558 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
559 ConstantInt::get(I.getType(), 1));
560 return BinaryOperator::create(Instruction::Mul, RHS, CP1);
563 // X + X*C --> X * (C+1)
564 if (dyn_castFoldableMul(RHS) == LHS) {
566 ConstantExpr::get(Instruction::Add,
567 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
568 ConstantInt::get(I.getType(), 1));
569 return BinaryOperator::create(Instruction::Mul, LHS, CP1);
572 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
573 if (Constant *C2 = dyn_castMaskingAnd(RHS))
574 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
576 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
577 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
578 switch (ILHS->getOpcode()) {
579 case Instruction::Xor:
580 // ~X + C --> (C-1) - X
581 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
582 if (XorRHS->isAllOnesValue())
583 return BinaryOperator::create(Instruction::Sub,
584 ConstantExpr::get(Instruction::Sub,
585 CRHS, ConstantInt::get(I.getType(), 1)),
586 ILHS->getOperand(0));
588 case Instruction::Select:
589 // Try to fold constant add into select arguments.
590 if (Instruction *R = FoldBinOpIntoSelect(I,cast<SelectInst>(ILHS),this))
598 return Changed ? &I : 0;
601 // isSignBit - Return true if the value represented by the constant only has the
602 // highest order bit set.
603 static bool isSignBit(ConstantInt *CI) {
604 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
605 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
608 static unsigned getTypeSizeInBits(const Type *Ty) {
609 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
612 /// RemoveNoopCast - Strip off nonconverting casts from the value.
614 static Value *RemoveNoopCast(Value *V) {
615 if (CastInst *CI = dyn_cast<CastInst>(V)) {
616 const Type *CTy = CI->getType();
617 const Type *OpTy = CI->getOperand(0)->getType();
618 if (CTy->isInteger() && OpTy->isInteger()) {
619 if (CTy->getPrimitiveSize() == OpTy->getPrimitiveSize())
620 return RemoveNoopCast(CI->getOperand(0));
621 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
622 return RemoveNoopCast(CI->getOperand(0));
627 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
628 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
630 if (Op0 == Op1) // sub X, X -> 0
631 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
633 // If this is a 'B = x-(-A)', change to B = x+A...
634 if (Value *V = dyn_castNegVal(Op1))
635 return BinaryOperator::create(Instruction::Add, Op0, V);
637 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
638 // Replace (-1 - A) with (~A)...
639 if (C->isAllOnesValue())
640 return BinaryOperator::createNot(Op1);
642 // C - ~X == X + (1+C)
643 if (BinaryOperator::isNot(Op1))
644 return BinaryOperator::create(Instruction::Add,
645 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
646 ConstantExpr::get(Instruction::Add, C,
647 ConstantInt::get(I.getType(), 1)));
648 // -((uint)X >> 31) -> ((int)X >> 31)
649 // -((int)X >> 31) -> ((uint)X >> 31)
650 if (C->isNullValue()) {
651 Value *NoopCastedRHS = RemoveNoopCast(Op1);
652 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
653 if (SI->getOpcode() == Instruction::Shr)
654 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
656 if (SI->getType()->isSigned())
657 NewTy = getUnsignedIntegralType(SI->getType());
659 NewTy = getSignedIntegralType(SI->getType());
660 // Check to see if we are shifting out everything but the sign bit.
661 if (CU->getValue() == SI->getType()->getPrimitiveSize()*8-1) {
662 // Ok, the transformation is safe. Insert a cast of the incoming
663 // value, then the new shift, then the new cast.
664 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
665 SI->getOperand(0)->getName());
666 Value *InV = InsertNewInstBefore(FirstCast, I);
667 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
669 if (NewShift->getType() == I.getType())
672 InV = InsertNewInstBefore(NewShift, I);
673 return new CastInst(NewShift, I.getType());
679 // Try to fold constant sub into select arguments.
680 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
681 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
685 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
686 if (Op1I->hasOneUse()) {
687 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
688 // is not used by anyone else...
690 if (Op1I->getOpcode() == Instruction::Sub &&
691 !Op1I->getType()->isFloatingPoint()) {
692 // Swap the two operands of the subexpr...
693 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
694 Op1I->setOperand(0, IIOp1);
695 Op1I->setOperand(1, IIOp0);
697 // Create the new top level add instruction...
698 return BinaryOperator::create(Instruction::Add, Op0, Op1);
701 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
703 if (Op1I->getOpcode() == Instruction::And &&
704 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
705 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
707 Instruction *NewNot = BinaryOperator::createNot(OtherOp, "B.not", &I);
708 return BinaryOperator::create(Instruction::And, Op0, NewNot);
711 // X - X*C --> X * (1-C)
712 if (dyn_castFoldableMul(Op1I) == Op0) {
714 ConstantExpr::get(Instruction::Sub,
715 ConstantInt::get(I.getType(), 1),
716 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
717 assert(CP1 && "Couldn't constant fold 1-C?");
718 return BinaryOperator::create(Instruction::Mul, Op0, CP1);
722 // X*C - X --> X * (C-1)
723 if (dyn_castFoldableMul(Op0) == Op1) {
725 ConstantExpr::get(Instruction::Sub,
726 cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
727 ConstantInt::get(I.getType(), 1));
728 assert(CP1 && "Couldn't constant fold C - 1?");
729 return BinaryOperator::create(Instruction::Mul, Op1, CP1);
735 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
736 /// really just returns true if the most significant (sign) bit is set.
737 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
738 if (RHS->getType()->isSigned()) {
739 // True if source is LHS < 0 or LHS <= -1
740 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
741 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
743 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
744 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
745 // the size of the integer type.
746 if (Opcode == Instruction::SetGE)
747 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
748 if (Opcode == Instruction::SetGT)
749 return RHSC->getValue() ==
750 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
755 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
756 bool Changed = SimplifyCommutative(I);
757 Value *Op0 = I.getOperand(0);
759 // Simplify mul instructions with a constant RHS...
760 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
761 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
763 // ((X << C1)*C2) == (X * (C2 << C1))
764 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
765 if (SI->getOpcode() == Instruction::Shl)
766 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
767 return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
768 ConstantExpr::get(Instruction::Shl, CI, ShOp));
770 if (CI->isNullValue())
771 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
772 if (CI->equalsInt(1)) // X * 1 == X
773 return ReplaceInstUsesWith(I, Op0);
774 if (CI->isAllOnesValue()) // X * -1 == 0 - X
775 return BinaryOperator::createNeg(Op0, I.getName());
777 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
778 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
779 return new ShiftInst(Instruction::Shl, Op0,
780 ConstantUInt::get(Type::UByteTy, C));
782 ConstantFP *Op1F = cast<ConstantFP>(Op1);
783 if (Op1F->isNullValue())
784 return ReplaceInstUsesWith(I, Op1);
786 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
787 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
788 if (Op1F->getValue() == 1.0)
789 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
792 // Try to fold constant mul into select arguments.
793 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
794 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
798 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
799 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
800 return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
802 // If one of the operands of the multiply is a cast from a boolean value, then
803 // we know the bool is either zero or one, so this is a 'masking' multiply.
804 // See if we can simplify things based on how the boolean was originally
806 CastInst *BoolCast = 0;
807 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
808 if (CI->getOperand(0)->getType() == Type::BoolTy)
811 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
812 if (CI->getOperand(0)->getType() == Type::BoolTy)
815 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
816 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
817 const Type *SCOpTy = SCIOp0->getType();
819 // If the setcc is true iff the sign bit of X is set, then convert this
820 // multiply into a shift/and combination.
821 if (isa<ConstantInt>(SCIOp1) &&
822 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
823 // Shift the X value right to turn it into "all signbits".
824 Constant *Amt = ConstantUInt::get(Type::UByteTy,
825 SCOpTy->getPrimitiveSize()*8-1);
826 if (SCIOp0->getType()->isUnsigned()) {
827 const Type *NewTy = getSignedIntegralType(SCIOp0->getType());
828 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
829 SCIOp0->getName()), I);
833 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
834 BoolCast->getOperand(0)->getName()+
837 // If the multiply type is not the same as the source type, sign extend
838 // or truncate to the multiply type.
839 if (I.getType() != V->getType())
840 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
842 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
843 return BinaryOperator::create(Instruction::And, V, OtherOp);
848 return Changed ? &I : 0;
851 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
853 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
854 if (RHS->equalsInt(1))
855 return ReplaceInstUsesWith(I, I.getOperand(0));
857 // Check to see if this is an unsigned division with an exact power of 2,
858 // if so, convert to a right shift.
859 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
860 if (uint64_t Val = C->getValue()) // Don't break X / 0
861 if (uint64_t C = Log2(Val))
862 return new ShiftInst(Instruction::Shr, I.getOperand(0),
863 ConstantUInt::get(Type::UByteTy, C));
866 // 0 / X == 0, we don't need to preserve faults!
867 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
868 if (LHS->equalsInt(0))
869 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
875 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
876 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
877 if (RHS->equalsInt(1)) // X % 1 == 0
878 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
879 if (RHS->isAllOnesValue()) // X % -1 == 0
880 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
882 // Check to see if this is an unsigned remainder with an exact power of 2,
883 // if so, convert to a bitwise and.
884 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
885 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
887 return BinaryOperator::create(Instruction::And, I.getOperand(0),
888 ConstantUInt::get(I.getType(), Val-1));
891 // 0 % X == 0, we don't need to preserve faults!
892 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
893 if (LHS->equalsInt(0))
894 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
899 // isMaxValueMinusOne - return true if this is Max-1
900 static bool isMaxValueMinusOne(const ConstantInt *C) {
901 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
902 // Calculate -1 casted to the right type...
903 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
904 uint64_t Val = ~0ULL; // All ones
905 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
906 return CU->getValue() == Val-1;
909 const ConstantSInt *CS = cast<ConstantSInt>(C);
911 // Calculate 0111111111..11111
912 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
913 int64_t Val = INT64_MAX; // All ones
914 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
915 return CS->getValue() == Val-1;
918 // isMinValuePlusOne - return true if this is Min+1
919 static bool isMinValuePlusOne(const ConstantInt *C) {
920 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
921 return CU->getValue() == 1;
923 const ConstantSInt *CS = cast<ConstantSInt>(C);
925 // Calculate 1111111111000000000000
926 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
927 int64_t Val = -1; // All ones
928 Val <<= TypeBits-1; // Shift over to the right spot
929 return CS->getValue() == Val+1;
932 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
933 /// are carefully arranged to allow folding of expressions such as:
935 /// (A < B) | (A > B) --> (A != B)
937 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
938 /// represents that the comparison is true if A == B, and bit value '1' is true
941 static unsigned getSetCondCode(const SetCondInst *SCI) {
942 switch (SCI->getOpcode()) {
944 case Instruction::SetGT: return 1;
945 case Instruction::SetEQ: return 2;
946 case Instruction::SetGE: return 3;
947 case Instruction::SetLT: return 4;
948 case Instruction::SetNE: return 5;
949 case Instruction::SetLE: return 6;
952 assert(0 && "Invalid SetCC opcode!");
957 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
958 /// opcode and two operands into either a constant true or false, or a brand new
959 /// SetCC instruction.
960 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
962 case 0: return ConstantBool::False;
963 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
964 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
965 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
966 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
967 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
968 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
969 case 7: return ConstantBool::True;
970 default: assert(0 && "Illegal SetCCCode!"); return 0;
974 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
975 struct FoldSetCCLogical {
978 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
979 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
980 bool shouldApply(Value *V) const {
981 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
982 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
983 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
986 Instruction *apply(BinaryOperator &Log) const {
987 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
988 if (SCI->getOperand(0) != LHS) {
989 assert(SCI->getOperand(1) == LHS);
990 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
993 unsigned LHSCode = getSetCondCode(SCI);
994 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
996 switch (Log.getOpcode()) {
997 case Instruction::And: Code = LHSCode & RHSCode; break;
998 case Instruction::Or: Code = LHSCode | RHSCode; break;
999 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
1000 default: assert(0 && "Illegal logical opcode!"); return 0;
1003 Value *RV = getSetCCValue(Code, LHS, RHS);
1004 if (Instruction *I = dyn_cast<Instruction>(RV))
1006 // Otherwise, it's a constant boolean value...
1007 return IC.ReplaceInstUsesWith(Log, RV);
1012 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
1013 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
1014 // guaranteed to be either a shift instruction or a binary operator.
1015 Instruction *InstCombiner::OptAndOp(Instruction *Op,
1016 ConstantIntegral *OpRHS,
1017 ConstantIntegral *AndRHS,
1018 BinaryOperator &TheAnd) {
1019 Value *X = Op->getOperand(0);
1020 Constant *Together = 0;
1021 if (!isa<ShiftInst>(Op))
1022 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
1024 switch (Op->getOpcode()) {
1025 case Instruction::Xor:
1026 if (Together->isNullValue()) {
1027 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
1028 return BinaryOperator::create(Instruction::And, X, AndRHS);
1029 } else if (Op->hasOneUse()) {
1030 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
1031 std::string OpName = Op->getName(); Op->setName("");
1032 Instruction *And = BinaryOperator::create(Instruction::And,
1034 InsertNewInstBefore(And, TheAnd);
1035 return BinaryOperator::create(Instruction::Xor, And, Together);
1038 case Instruction::Or:
1039 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
1040 if (Together->isNullValue())
1041 return BinaryOperator::create(Instruction::And, X, AndRHS);
1043 if (Together == AndRHS) // (X | C) & C --> C
1044 return ReplaceInstUsesWith(TheAnd, AndRHS);
1046 if (Op->hasOneUse() && Together != OpRHS) {
1047 // (X | C1) & C2 --> (X | (C1&C2)) & C2
1048 std::string Op0Name = Op->getName(); Op->setName("");
1049 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
1051 InsertNewInstBefore(Or, TheAnd);
1052 return BinaryOperator::create(Instruction::And, Or, AndRHS);
1056 case Instruction::Add:
1057 if (Op->hasOneUse()) {
1058 // Adding a one to a single bit bit-field should be turned into an XOR
1059 // of the bit. First thing to check is to see if this AND is with a
1060 // single bit constant.
1061 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1063 // Clear bits that are not part of the constant.
1064 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
1066 // If there is only one bit set...
1067 if ((AndRHSV & (AndRHSV-1)) == 0) {
1068 // Ok, at this point, we know that we are masking the result of the
1069 // ADD down to exactly one bit. If the constant we are adding has
1070 // no bits set below this bit, then we can eliminate the ADD.
1071 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1073 // Check to see if any bits below the one bit set in AndRHSV are set.
1074 if ((AddRHS & (AndRHSV-1)) == 0) {
1075 // If not, the only thing that can effect the output of the AND is
1076 // the bit specified by AndRHSV. If that bit is set, the effect of
1077 // the XOR is to toggle the bit. If it is clear, then the ADD has
1079 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1080 TheAnd.setOperand(0, X);
1083 std::string Name = Op->getName(); Op->setName("");
1084 // Pull the XOR out of the AND.
1085 Instruction *NewAnd =
1086 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
1087 InsertNewInstBefore(NewAnd, TheAnd);
1088 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
1095 case Instruction::Shl: {
1096 // We know that the AND will not produce any of the bits shifted in, so if
1097 // the anded constant includes them, clear them now!
1099 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1100 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1101 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
1103 TheAnd.setOperand(1, CI);
1108 case Instruction::Shr:
1109 // We know that the AND will not produce any of the bits shifted in, so if
1110 // the anded constant includes them, clear them now! This only applies to
1111 // unsigned shifts, because a signed shr may bring in set bits!
1113 if (AndRHS->getType()->isUnsigned()) {
1114 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1115 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1116 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
1118 TheAnd.setOperand(1, CI);
1128 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1129 bool Changed = SimplifyCommutative(I);
1130 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1132 // and X, X = X and X, 0 == 0
1133 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1134 return ReplaceInstUsesWith(I, Op1);
1137 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1138 if (RHS->isAllOnesValue())
1139 return ReplaceInstUsesWith(I, Op0);
1141 // Optimize a variety of ((val OP C1) & C2) combinations...
1142 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1143 Instruction *Op0I = cast<Instruction>(Op0);
1144 Value *X = Op0I->getOperand(0);
1145 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1146 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1150 // Try to fold constant and into select arguments.
1151 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1152 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1156 Value *Op0NotVal = dyn_castNotVal(Op0);
1157 Value *Op1NotVal = dyn_castNotVal(Op1);
1159 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1160 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1161 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1162 Op1NotVal,I.getName()+".demorgan");
1163 InsertNewInstBefore(Or, I);
1164 return BinaryOperator::createNot(Or);
1167 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1168 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1170 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1171 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1172 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1175 return Changed ? &I : 0;
1180 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1181 bool Changed = SimplifyCommutative(I);
1182 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1184 // or X, X = X or X, 0 == X
1185 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1186 return ReplaceInstUsesWith(I, Op0);
1189 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1190 if (RHS->isAllOnesValue())
1191 return ReplaceInstUsesWith(I, Op1);
1193 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1194 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1195 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1196 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1197 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1198 Instruction *Or = BinaryOperator::create(Instruction::Or,
1199 Op0I->getOperand(0), RHS,
1201 InsertNewInstBefore(Or, I);
1202 return BinaryOperator::create(Instruction::And, Or,
1203 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1206 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1207 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1208 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1209 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1210 Instruction *Or = BinaryOperator::create(Instruction::Or,
1211 Op0I->getOperand(0), RHS,
1213 InsertNewInstBefore(Or, I);
1214 return BinaryOperator::create(Instruction::Xor, Or,
1215 ConstantExpr::get(Instruction::And, Op0CI,
1220 // Try to fold constant and into select arguments.
1221 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1222 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1226 // (A & C1)|(A & C2) == A & (C1|C2)
1227 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1228 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1229 if (LHS->getOperand(0) == RHS->getOperand(0))
1230 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1231 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1232 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1233 ConstantExpr::get(Instruction::Or, C0, C1));
1235 Value *Op0NotVal = dyn_castNotVal(Op0);
1236 Value *Op1NotVal = dyn_castNotVal(Op1);
1238 if (Op1 == Op0NotVal) // ~A | A == -1
1239 return ReplaceInstUsesWith(I,
1240 ConstantIntegral::getAllOnesValue(I.getType()));
1242 if (Op0 == Op1NotVal) // A | ~A == -1
1243 return ReplaceInstUsesWith(I,
1244 ConstantIntegral::getAllOnesValue(I.getType()));
1246 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1247 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1248 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1249 Op1NotVal,I.getName()+".demorgan",
1251 WorkList.push_back(And);
1252 return BinaryOperator::createNot(And);
1255 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1256 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1257 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1260 return Changed ? &I : 0;
1263 // XorSelf - Implements: X ^ X --> 0
1266 XorSelf(Value *rhs) : RHS(rhs) {}
1267 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1268 Instruction *apply(BinaryOperator &Xor) const {
1274 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1275 bool Changed = SimplifyCommutative(I);
1276 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1278 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1279 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1280 assert(Result == &I && "AssociativeOpt didn't work?");
1281 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1284 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1286 if (RHS->isNullValue())
1287 return ReplaceInstUsesWith(I, Op0);
1289 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1290 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1291 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1292 if (RHS == ConstantBool::True && SCI->hasOneUse())
1293 return new SetCondInst(SCI->getInverseCondition(),
1294 SCI->getOperand(0), SCI->getOperand(1));
1296 // ~(c-X) == X-c-1 == X+(-c-1)
1297 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1298 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1299 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1300 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1301 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1302 ConstantInt::get(I.getType(), 1));
1303 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1307 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1308 switch (Op0I->getOpcode()) {
1309 case Instruction::Add:
1310 // ~(X-c) --> (-c-1)-X
1311 if (RHS->isAllOnesValue()) {
1312 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1313 Constant::getNullValue(Op0CI->getType()), Op0CI);
1314 return BinaryOperator::create(Instruction::Sub,
1315 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1316 ConstantInt::get(I.getType(), 1)),
1317 Op0I->getOperand(0));
1320 case Instruction::And:
1321 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1322 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1323 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1325 case Instruction::Or:
1326 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1327 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1328 return BinaryOperator::create(Instruction::And, Op0,
1335 // Try to fold constant and into select arguments.
1336 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1337 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1341 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1343 return ReplaceInstUsesWith(I,
1344 ConstantIntegral::getAllOnesValue(I.getType()));
1346 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1348 return ReplaceInstUsesWith(I,
1349 ConstantIntegral::getAllOnesValue(I.getType()));
1351 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1352 if (Op1I->getOpcode() == Instruction::Or) {
1353 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1354 cast<BinaryOperator>(Op1I)->swapOperands();
1356 std::swap(Op0, Op1);
1357 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1359 std::swap(Op0, Op1);
1361 } else if (Op1I->getOpcode() == Instruction::Xor) {
1362 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1363 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1364 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1365 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1368 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1369 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1370 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1371 cast<BinaryOperator>(Op0I)->swapOperands();
1372 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1373 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1374 WorkList.push_back(cast<Instruction>(NotB));
1375 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1378 } else if (Op0I->getOpcode() == Instruction::Xor) {
1379 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1380 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1381 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1382 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1385 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1386 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1387 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1388 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1389 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1391 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1392 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1393 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1396 return Changed ? &I : 0;
1399 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1400 static Constant *AddOne(ConstantInt *C) {
1401 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1402 ConstantInt::get(C->getType(), 1));
1403 assert(Result && "Constant folding integer addition failed!");
1406 static Constant *SubOne(ConstantInt *C) {
1407 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1408 ConstantInt::get(C->getType(), 1));
1409 assert(Result && "Constant folding integer addition failed!");
1413 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1414 // true when both operands are equal...
1416 static bool isTrueWhenEqual(Instruction &I) {
1417 return I.getOpcode() == Instruction::SetEQ ||
1418 I.getOpcode() == Instruction::SetGE ||
1419 I.getOpcode() == Instruction::SetLE;
1422 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1423 bool Changed = SimplifyCommutative(I);
1424 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1425 const Type *Ty = Op0->getType();
1429 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1431 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1432 if (isa<ConstantPointerNull>(Op1) &&
1433 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1434 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1437 // setcc's with boolean values can always be turned into bitwise operations
1438 if (Ty == Type::BoolTy) {
1439 // If this is <, >, or !=, we can change this into a simple xor instruction
1440 if (!isTrueWhenEqual(I))
1441 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1443 // Otherwise we need to make a temporary intermediate instruction and insert
1444 // it into the instruction stream. This is what we are after:
1446 // seteq bool %A, %B -> ~(A^B)
1447 // setle bool %A, %B -> ~A | B
1448 // setge bool %A, %B -> A | ~B
1450 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1451 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1453 InsertNewInstBefore(Xor, I);
1454 return BinaryOperator::createNot(Xor);
1457 // Handle the setXe cases...
1458 assert(I.getOpcode() == Instruction::SetGE ||
1459 I.getOpcode() == Instruction::SetLE);
1461 if (I.getOpcode() == Instruction::SetGE)
1462 std::swap(Op0, Op1); // Change setge -> setle
1464 // Now we just have the SetLE case.
1465 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1466 InsertNewInstBefore(Not, I);
1467 return BinaryOperator::create(Instruction::Or, Not, Op1);
1470 // Check to see if we are doing one of many comparisons against constant
1471 // integers at the end of their ranges...
1473 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1474 // Simplify seteq and setne instructions...
1475 if (I.getOpcode() == Instruction::SetEQ ||
1476 I.getOpcode() == Instruction::SetNE) {
1477 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1479 // If the first operand is (and|or|xor) with a constant, and the second
1480 // operand is a constant, simplify a bit.
1481 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1482 switch (BO->getOpcode()) {
1483 case Instruction::Add:
1484 if (CI->isNullValue()) {
1485 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1486 // efficiently invertible, or if the add has just this one use.
1487 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1488 if (Value *NegVal = dyn_castNegVal(BOp1))
1489 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1490 else if (Value *NegVal = dyn_castNegVal(BOp0))
1491 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1492 else if (BO->hasOneUse()) {
1493 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1495 InsertNewInstBefore(Neg, I);
1496 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1500 case Instruction::Xor:
1501 // For the xor case, we can xor two constants together, eliminating
1502 // the explicit xor.
1503 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1504 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1505 ConstantExpr::get(Instruction::Xor, CI, BOC));
1508 case Instruction::Sub:
1509 // Replace (([sub|xor] A, B) != 0) with (A != B)
1510 if (CI->isNullValue())
1511 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1515 case Instruction::Or:
1516 // If bits are being or'd in that are not present in the constant we
1517 // are comparing against, then the comparison could never succeed!
1518 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1519 Constant *NotCI = NotConstant(CI);
1520 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1521 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1525 case Instruction::And:
1526 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1527 // If bits are being compared against that are and'd out, then the
1528 // comparison can never succeed!
1529 if (!ConstantExpr::get(Instruction::And, CI,
1530 NotConstant(BOC))->isNullValue())
1531 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1533 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1534 // to be a signed value as appropriate.
1535 if (isSignBit(BOC)) {
1536 Value *X = BO->getOperand(0);
1537 // If 'X' is not signed, insert a cast now...
1538 if (!BOC->getType()->isSigned()) {
1539 const Type *DestTy = getSignedIntegralType(BOC->getType());
1540 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1541 InsertNewInstBefore(NewCI, I);
1544 return new SetCondInst(isSetNE ? Instruction::SetLT :
1545 Instruction::SetGE, X,
1546 Constant::getNullValue(X->getType()));
1552 } else { // Not a SetEQ/SetNE
1553 // If the LHS is a cast from an integral value of the same size,
1554 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1555 Value *CastOp = Cast->getOperand(0);
1556 const Type *SrcTy = CastOp->getType();
1557 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1558 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1559 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1560 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1561 "Source and destination signednesses should differ!");
1562 if (Cast->getType()->isSigned()) {
1563 // If this is a signed comparison, check for comparisons in the
1564 // vicinity of zero.
1565 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1567 return BinaryOperator::create(Instruction::SetGT, CastOp,
1568 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1569 else if (I.getOpcode() == Instruction::SetGT &&
1570 cast<ConstantSInt>(CI)->getValue() == -1)
1571 // X > -1 => x < 128
1572 return BinaryOperator::create(Instruction::SetLT, CastOp,
1573 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1575 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1576 if (I.getOpcode() == Instruction::SetLT &&
1577 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1578 // X < 128 => X > -1
1579 return BinaryOperator::create(Instruction::SetGT, CastOp,
1580 ConstantSInt::get(SrcTy, -1));
1581 else if (I.getOpcode() == Instruction::SetGT &&
1582 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1584 return BinaryOperator::create(Instruction::SetLT, CastOp,
1585 Constant::getNullValue(SrcTy));
1591 // Check to see if we are comparing against the minimum or maximum value...
1592 if (CI->isMinValue()) {
1593 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1594 return ReplaceInstUsesWith(I, ConstantBool::False);
1595 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1596 return ReplaceInstUsesWith(I, ConstantBool::True);
1597 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1598 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1599 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1600 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1602 } else if (CI->isMaxValue()) {
1603 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1604 return ReplaceInstUsesWith(I, ConstantBool::False);
1605 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1606 return ReplaceInstUsesWith(I, ConstantBool::True);
1607 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1608 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1609 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1610 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1612 // Comparing against a value really close to min or max?
1613 } else if (isMinValuePlusOne(CI)) {
1614 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1615 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1616 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1617 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1619 } else if (isMaxValueMinusOne(CI)) {
1620 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1621 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1622 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1623 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1626 // If we still have a setle or setge instruction, turn it into the
1627 // appropriate setlt or setgt instruction. Since the border cases have
1628 // already been handled above, this requires little checking.
1630 if (I.getOpcode() == Instruction::SetLE)
1631 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1632 if (I.getOpcode() == Instruction::SetGE)
1633 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1636 // Test to see if the operands of the setcc are casted versions of other
1637 // values. If the cast can be stripped off both arguments, we do so now.
1638 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1639 Value *CastOp0 = CI->getOperand(0);
1640 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1641 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1642 (I.getOpcode() == Instruction::SetEQ ||
1643 I.getOpcode() == Instruction::SetNE)) {
1644 // We keep moving the cast from the left operand over to the right
1645 // operand, where it can often be eliminated completely.
1648 // If operand #1 is a cast instruction, see if we can eliminate it as
1650 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1651 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1653 Op1 = CI2->getOperand(0);
1655 // If Op1 is a constant, we can fold the cast into the constant.
1656 if (Op1->getType() != Op0->getType())
1657 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1658 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1660 // Otherwise, cast the RHS right before the setcc
1661 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1662 InsertNewInstBefore(cast<Instruction>(Op1), I);
1664 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1667 // Handle the special case of: setcc (cast bool to X), <cst>
1668 // This comes up when you have code like
1671 // For generality, we handle any zero-extension of any operand comparison
1673 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1674 const Type *SrcTy = CastOp0->getType();
1675 const Type *DestTy = Op0->getType();
1676 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1677 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1678 // Ok, we have an expansion of operand 0 into a new type. Get the
1679 // constant value, masink off bits which are not set in the RHS. These
1680 // could be set if the destination value is signed.
1681 uint64_t ConstVal = ConstantRHS->getRawValue();
1682 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1684 // If the constant we are comparing it with has high bits set, which
1685 // don't exist in the original value, the values could never be equal,
1686 // because the source would be zero extended.
1688 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1689 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1690 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1691 switch (I.getOpcode()) {
1692 default: assert(0 && "Unknown comparison type!");
1693 case Instruction::SetEQ:
1694 return ReplaceInstUsesWith(I, ConstantBool::False);
1695 case Instruction::SetNE:
1696 return ReplaceInstUsesWith(I, ConstantBool::True);
1697 case Instruction::SetLT:
1698 case Instruction::SetLE:
1699 if (DestTy->isSigned() && HasSignBit)
1700 return ReplaceInstUsesWith(I, ConstantBool::False);
1701 return ReplaceInstUsesWith(I, ConstantBool::True);
1702 case Instruction::SetGT:
1703 case Instruction::SetGE:
1704 if (DestTy->isSigned() && HasSignBit)
1705 return ReplaceInstUsesWith(I, ConstantBool::True);
1706 return ReplaceInstUsesWith(I, ConstantBool::False);
1710 // Otherwise, we can replace the setcc with a setcc of the smaller
1712 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1713 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1717 return Changed ? &I : 0;
1722 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1723 assert(I.getOperand(1)->getType() == Type::UByteTy);
1724 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1725 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1727 // shl X, 0 == X and shr X, 0 == X
1728 // shl 0, X == 0 and shr 0, X == 0
1729 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1730 Op0 == Constant::getNullValue(Op0->getType()))
1731 return ReplaceInstUsesWith(I, Op0);
1733 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1735 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1736 if (CSI->isAllOnesValue())
1737 return ReplaceInstUsesWith(I, CSI);
1739 // Try to fold constant and into select arguments.
1740 if (isa<Constant>(Op0))
1741 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1742 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1745 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1746 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1747 // of a signed value.
1749 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1750 if (CUI->getValue() >= TypeBits) {
1751 if (!Op0->getType()->isSigned() || isLeftShift)
1752 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1754 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1759 // ((X*C1) << C2) == (X * (C1 << C2))
1760 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1761 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1762 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1763 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1764 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1766 // Try to fold constant and into select arguments.
1767 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1768 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1771 // If the operand is an bitwise operator with a constant RHS, and the
1772 // shift is the only use, we can pull it out of the shift.
1773 if (Op0->hasOneUse())
1774 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1775 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1776 bool isValid = true; // Valid only for And, Or, Xor
1777 bool highBitSet = false; // Transform if high bit of constant set?
1779 switch (Op0BO->getOpcode()) {
1780 default: isValid = false; break; // Do not perform transform!
1781 case Instruction::Or:
1782 case Instruction::Xor:
1785 case Instruction::And:
1790 // If this is a signed shift right, and the high bit is modified
1791 // by the logical operation, do not perform the transformation.
1792 // The highBitSet boolean indicates the value of the high bit of
1793 // the constant which would cause it to be modified for this
1796 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1797 uint64_t Val = Op0C->getRawValue();
1798 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1802 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1804 Instruction *NewShift =
1805 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1808 InsertNewInstBefore(NewShift, I);
1810 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1815 // If this is a shift of a shift, see if we can fold the two together...
1816 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1817 if (ConstantUInt *ShiftAmt1C =
1818 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1819 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1820 unsigned ShiftAmt2 = CUI->getValue();
1822 // Check for (A << c1) << c2 and (A >> c1) >> c2
1823 if (I.getOpcode() == Op0SI->getOpcode()) {
1824 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1825 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1826 Amt = Op0->getType()->getPrimitiveSize()*8;
1827 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1828 ConstantUInt::get(Type::UByteTy, Amt));
1831 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1832 // signed types, we can only support the (A >> c1) << c2 configuration,
1833 // because it can not turn an arbitrary bit of A into a sign bit.
1834 if (I.getType()->isUnsigned() || isLeftShift) {
1835 // Calculate bitmask for what gets shifted off the edge...
1836 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1838 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1840 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1843 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1844 C, Op0SI->getOperand(0)->getName()+".mask");
1845 InsertNewInstBefore(Mask, I);
1847 // Figure out what flavor of shift we should use...
1848 if (ShiftAmt1 == ShiftAmt2)
1849 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1850 else if (ShiftAmt1 < ShiftAmt2) {
1851 return new ShiftInst(I.getOpcode(), Mask,
1852 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1854 return new ShiftInst(Op0SI->getOpcode(), Mask,
1855 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1865 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1868 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1869 const Type *DstTy) {
1871 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1872 // are identical and the bits don't get reinterpreted (for example
1873 // int->float->int would not be allowed)
1874 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1877 // Allow free casting and conversion of sizes as long as the sign doesn't
1879 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1880 unsigned SrcSize = SrcTy->getPrimitiveSize();
1881 unsigned MidSize = MidTy->getPrimitiveSize();
1882 unsigned DstSize = DstTy->getPrimitiveSize();
1884 // Cases where we are monotonically decreasing the size of the type are
1885 // always ok, regardless of what sign changes are going on.
1887 if (SrcSize >= MidSize && MidSize >= DstSize)
1890 // Cases where the source and destination type are the same, but the middle
1891 // type is bigger are noops.
1893 if (SrcSize == DstSize && MidSize > SrcSize)
1896 // If we are monotonically growing, things are more complex.
1898 if (SrcSize <= MidSize && MidSize <= DstSize) {
1899 // We have eight combinations of signedness to worry about. Here's the
1901 static const int SignTable[8] = {
1902 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1903 1, // U U U Always ok
1904 1, // U U S Always ok
1905 3, // U S U Ok iff SrcSize != MidSize
1906 3, // U S S Ok iff SrcSize != MidSize
1907 0, // S U U Never ok
1908 2, // S U S Ok iff MidSize == DstSize
1909 1, // S S U Always ok
1910 1, // S S S Always ok
1913 // Choose an action based on the current entry of the signtable that this
1914 // cast of cast refers to...
1915 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1916 switch (SignTable[Row]) {
1917 case 0: return false; // Never ok
1918 case 1: return true; // Always ok
1919 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1920 case 3: // Ok iff SrcSize != MidSize
1921 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1922 default: assert(0 && "Bad entry in sign table!");
1927 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1928 // like: short -> ushort -> uint, because this can create wrong results if
1929 // the input short is negative!
1934 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1935 if (V->getType() == Ty || isa<Constant>(V)) return false;
1936 if (const CastInst *CI = dyn_cast<CastInst>(V))
1937 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1942 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1943 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1944 /// casts that are known to not do anything...
1946 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1947 Instruction *InsertBefore) {
1948 if (V->getType() == DestTy) return V;
1949 if (Constant *C = dyn_cast<Constant>(V))
1950 return ConstantExpr::getCast(C, DestTy);
1952 CastInst *CI = new CastInst(V, DestTy, V->getName());
1953 InsertNewInstBefore(CI, *InsertBefore);
1957 // CastInst simplification
1959 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1960 Value *Src = CI.getOperand(0);
1962 // If the user is casting a value to the same type, eliminate this cast
1964 if (CI.getType() == Src->getType())
1965 return ReplaceInstUsesWith(CI, Src);
1967 // If casting the result of another cast instruction, try to eliminate this
1970 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1971 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1972 CSrc->getType(), CI.getType())) {
1973 // This instruction now refers directly to the cast's src operand. This
1974 // has a good chance of making CSrc dead.
1975 CI.setOperand(0, CSrc->getOperand(0));
1979 // If this is an A->B->A cast, and we are dealing with integral types, try
1980 // to convert this into a logical 'and' instruction.
1982 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1983 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1984 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1985 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1986 assert(CSrc->getType() != Type::ULongTy &&
1987 "Cannot have type bigger than ulong!");
1988 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1989 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1990 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1995 // If casting the result of a getelementptr instruction with no offset, turn
1996 // this into a cast of the original pointer!
1998 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
1999 bool AllZeroOperands = true;
2000 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2001 if (!isa<Constant>(GEP->getOperand(i)) ||
2002 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
2003 AllZeroOperands = false;
2006 if (AllZeroOperands) {
2007 CI.setOperand(0, GEP->getOperand(0));
2012 // If we are casting a malloc or alloca to a pointer to a type of the same
2013 // size, rewrite the allocation instruction to allocate the "right" type.
2015 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
2016 if (AI->hasOneUse() && !AI->isArrayAllocation())
2017 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
2018 // Get the type really allocated and the type casted to...
2019 const Type *AllocElTy = AI->getAllocatedType();
2020 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
2021 const Type *CastElTy = PTy->getElementType();
2022 unsigned CastElTySize = TD->getTypeSize(CastElTy);
2024 // If the allocation is for an even multiple of the cast type size
2025 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
2026 Value *Amt = ConstantUInt::get(Type::UIntTy,
2027 AllocElTySize/CastElTySize);
2028 std::string Name = AI->getName(); AI->setName("");
2029 AllocationInst *New;
2030 if (isa<MallocInst>(AI))
2031 New = new MallocInst(CastElTy, Amt, Name);
2033 New = new AllocaInst(CastElTy, Amt, Name);
2034 InsertNewInstBefore(New, CI);
2035 return ReplaceInstUsesWith(CI, New);
2039 // If the source value is an instruction with only this use, we can attempt to
2040 // propagate the cast into the instruction. Also, only handle integral types
2042 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
2043 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
2044 CI.getType()->isInteger()) { // Don't mess with casts to bool here
2045 const Type *DestTy = CI.getType();
2046 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
2047 unsigned DestBitSize = getTypeSizeInBits(DestTy);
2049 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
2050 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
2052 switch (SrcI->getOpcode()) {
2053 case Instruction::Add:
2054 case Instruction::Mul:
2055 case Instruction::And:
2056 case Instruction::Or:
2057 case Instruction::Xor:
2058 // If we are discarding information, or just changing the sign, rewrite.
2059 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
2060 // Don't insert two casts if they cannot be eliminated. We allow two
2061 // casts to be inserted if the sizes are the same. This could only be
2062 // converting signedness, which is a noop.
2063 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
2064 !ValueRequiresCast(Op0, DestTy)) {
2065 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2066 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
2067 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
2068 ->getOpcode(), Op0c, Op1c);
2072 case Instruction::Shl:
2073 // Allow changing the sign of the source operand. Do not allow changing
2074 // the size of the shift, UNLESS the shift amount is a constant. We
2075 // mush not change variable sized shifts to a smaller size, because it
2076 // is undefined to shift more bits out than exist in the value.
2077 if (DestBitSize == SrcBitSize ||
2078 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2079 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2080 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2089 /// GetSelectFoldableOperands - We want to turn code that looks like this:
2091 /// %D = select %cond, %C, %A
2093 /// %C = select %cond, %B, 0
2096 /// Assuming that the specified instruction is an operand to the select, return
2097 /// a bitmask indicating which operands of this instruction are foldable if they
2098 /// equal the other incoming value of the select.
2100 static unsigned GetSelectFoldableOperands(Instruction *I) {
2101 switch (I->getOpcode()) {
2102 case Instruction::Add:
2103 case Instruction::Mul:
2104 case Instruction::And:
2105 case Instruction::Or:
2106 case Instruction::Xor:
2107 return 3; // Can fold through either operand.
2108 case Instruction::Sub: // Can only fold on the amount subtracted.
2109 case Instruction::Shl: // Can only fold on the shift amount.
2110 case Instruction::Shr:
2113 return 0; // Cannot fold
2117 /// GetSelectFoldableConstant - For the same transformation as the previous
2118 /// function, return the identity constant that goes into the select.
2119 static Constant *GetSelectFoldableConstant(Instruction *I) {
2120 switch (I->getOpcode()) {
2121 default: assert(0 && "This cannot happen!"); abort();
2122 case Instruction::Add:
2123 case Instruction::Sub:
2124 case Instruction::Or:
2125 case Instruction::Xor:
2126 return Constant::getNullValue(I->getType());
2127 case Instruction::Shl:
2128 case Instruction::Shr:
2129 return Constant::getNullValue(Type::UByteTy);
2130 case Instruction::And:
2131 return ConstantInt::getAllOnesValue(I->getType());
2132 case Instruction::Mul:
2133 return ConstantInt::get(I->getType(), 1);
2137 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
2138 Value *CondVal = SI.getCondition();
2139 Value *TrueVal = SI.getTrueValue();
2140 Value *FalseVal = SI.getFalseValue();
2142 // select true, X, Y -> X
2143 // select false, X, Y -> Y
2144 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
2145 if (C == ConstantBool::True)
2146 return ReplaceInstUsesWith(SI, TrueVal);
2148 assert(C == ConstantBool::False);
2149 return ReplaceInstUsesWith(SI, FalseVal);
2152 // select C, X, X -> X
2153 if (TrueVal == FalseVal)
2154 return ReplaceInstUsesWith(SI, TrueVal);
2156 if (SI.getType() == Type::BoolTy)
2157 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
2158 if (C == ConstantBool::True) {
2159 // Change: A = select B, true, C --> A = or B, C
2160 return BinaryOperator::create(Instruction::Or, CondVal, FalseVal);
2162 // Change: A = select B, false, C --> A = and !B, C
2164 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2165 "not."+CondVal->getName()), SI);
2166 return BinaryOperator::create(Instruction::And, NotCond, FalseVal);
2168 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
2169 if (C == ConstantBool::False) {
2170 // Change: A = select B, C, false --> A = and B, C
2171 return BinaryOperator::create(Instruction::And, CondVal, TrueVal);
2173 // Change: A = select B, C, true --> A = or !B, C
2175 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2176 "not."+CondVal->getName()), SI);
2177 return BinaryOperator::create(Instruction::Or, NotCond, TrueVal);
2181 // Selecting between two integer constants?
2182 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
2183 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
2184 // select C, 1, 0 -> cast C to int
2185 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
2186 return new CastInst(CondVal, SI.getType());
2187 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
2188 // select C, 0, 1 -> cast !C to int
2190 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2191 "not."+CondVal->getName()), SI);
2192 return new CastInst(NotCond, SI.getType());
2196 // See if we are selecting two values based on a comparison of the two values.
2197 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
2198 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
2199 // Transform (X == Y) ? X : Y -> Y
2200 if (SCI->getOpcode() == Instruction::SetEQ)
2201 return ReplaceInstUsesWith(SI, FalseVal);
2202 // Transform (X != Y) ? X : Y -> X
2203 if (SCI->getOpcode() == Instruction::SetNE)
2204 return ReplaceInstUsesWith(SI, TrueVal);
2205 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2207 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
2208 // Transform (X == Y) ? Y : X -> X
2209 if (SCI->getOpcode() == Instruction::SetEQ)
2210 return ReplaceInstUsesWith(SI, FalseVal);
2211 // Transform (X != Y) ? Y : X -> Y
2212 if (SCI->getOpcode() == Instruction::SetNE)
2213 return ReplaceInstUsesWith(SI, TrueVal);
2214 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2218 // See if we can fold the select into one of our operands.
2219 if (SI.getType()->isInteger()) {
2220 // See the comment above GetSelectFoldableOperands for a description of the
2221 // transformation we are doing here.
2222 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
2223 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
2224 !isa<Constant>(FalseVal))
2225 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
2226 unsigned OpToFold = 0;
2227 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
2229 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
2234 Constant *C = GetSelectFoldableConstant(TVI);
2235 std::string Name = TVI->getName(); TVI->setName("");
2236 Instruction *NewSel =
2237 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
2239 InsertNewInstBefore(NewSel, SI);
2240 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
2241 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
2242 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
2243 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
2245 assert(0 && "Unknown instruction!!");
2250 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
2251 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
2252 !isa<Constant>(TrueVal))
2253 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
2254 unsigned OpToFold = 0;
2255 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
2257 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
2262 Constant *C = GetSelectFoldableConstant(FVI);
2263 std::string Name = FVI->getName(); FVI->setName("");
2264 Instruction *NewSel =
2265 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
2267 InsertNewInstBefore(NewSel, SI);
2268 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
2269 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
2270 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
2271 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
2273 assert(0 && "Unknown instruction!!");
2282 // CallInst simplification
2284 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2285 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2287 if (Function *F = CI.getCalledFunction())
2288 switch (F->getIntrinsicID()) {
2289 case Intrinsic::memmove:
2290 case Intrinsic::memcpy:
2291 case Intrinsic::memset:
2292 // memmove/cpy/set of zero bytes is a noop.
2293 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2294 if (NumBytes->isNullValue())
2295 return EraseInstFromFunction(CI);
2302 return visitCallSite(&CI);
2305 // InvokeInst simplification
2307 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2308 return visitCallSite(&II);
2311 // visitCallSite - Improvements for call and invoke instructions.
2313 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2314 bool Changed = false;
2316 // If the callee is a constexpr cast of a function, attempt to move the cast
2317 // to the arguments of the call/invoke.
2318 if (transformConstExprCastCall(CS)) return 0;
2320 Value *Callee = CS.getCalledValue();
2321 const PointerType *PTy = cast<PointerType>(Callee->getType());
2322 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2323 if (FTy->isVarArg()) {
2324 // See if we can optimize any arguments passed through the varargs area of
2326 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2327 E = CS.arg_end(); I != E; ++I)
2328 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2329 // If this cast does not effect the value passed through the varargs
2330 // area, we can eliminate the use of the cast.
2331 Value *Op = CI->getOperand(0);
2332 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2339 return Changed ? CS.getInstruction() : 0;
2342 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2343 // attempt to move the cast to the arguments of the call/invoke.
2345 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2346 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2347 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2348 if (CE->getOpcode() != Instruction::Cast ||
2349 !isa<ConstantPointerRef>(CE->getOperand(0)))
2351 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2352 if (!isa<Function>(CPR->getValue())) return false;
2353 Function *Callee = cast<Function>(CPR->getValue());
2354 Instruction *Caller = CS.getInstruction();
2356 // Okay, this is a cast from a function to a different type. Unless doing so
2357 // would cause a type conversion of one of our arguments, change this call to
2358 // be a direct call with arguments casted to the appropriate types.
2360 const FunctionType *FT = Callee->getFunctionType();
2361 const Type *OldRetTy = Caller->getType();
2363 // Check to see if we are changing the return type...
2364 if (OldRetTy != FT->getReturnType()) {
2365 if (Callee->isExternal() &&
2366 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2367 !Caller->use_empty())
2368 return false; // Cannot transform this return value...
2370 // If the callsite is an invoke instruction, and the return value is used by
2371 // a PHI node in a successor, we cannot change the return type of the call
2372 // because there is no place to put the cast instruction (without breaking
2373 // the critical edge). Bail out in this case.
2374 if (!Caller->use_empty())
2375 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2376 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2378 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2379 if (PN->getParent() == II->getNormalDest() ||
2380 PN->getParent() == II->getUnwindDest())
2384 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2385 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2387 CallSite::arg_iterator AI = CS.arg_begin();
2388 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2389 const Type *ParamTy = FT->getParamType(i);
2390 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2391 if (Callee->isExternal() && !isConvertible) return false;
2394 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2395 Callee->isExternal())
2396 return false; // Do not delete arguments unless we have a function body...
2398 // Okay, we decided that this is a safe thing to do: go ahead and start
2399 // inserting cast instructions as necessary...
2400 std::vector<Value*> Args;
2401 Args.reserve(NumActualArgs);
2403 AI = CS.arg_begin();
2404 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2405 const Type *ParamTy = FT->getParamType(i);
2406 if ((*AI)->getType() == ParamTy) {
2407 Args.push_back(*AI);
2409 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
2414 // If the function takes more arguments than the call was taking, add them
2416 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2417 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2419 // If we are removing arguments to the function, emit an obnoxious warning...
2420 if (FT->getNumParams() < NumActualArgs)
2421 if (!FT->isVarArg()) {
2422 std::cerr << "WARNING: While resolving call to function '"
2423 << Callee->getName() << "' arguments were dropped!\n";
2425 // Add all of the arguments in their promoted form to the arg list...
2426 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2427 const Type *PTy = getPromotedType((*AI)->getType());
2428 if (PTy != (*AI)->getType()) {
2429 // Must promote to pass through va_arg area!
2430 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2431 InsertNewInstBefore(Cast, *Caller);
2432 Args.push_back(Cast);
2434 Args.push_back(*AI);
2439 if (FT->getReturnType() == Type::VoidTy)
2440 Caller->setName(""); // Void type should not have a name...
2443 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2444 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2445 Args, Caller->getName(), Caller);
2447 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2450 // Insert a cast of the return type as necessary...
2452 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2453 if (NV->getType() != Type::VoidTy) {
2454 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2456 // If this is an invoke instruction, we should insert it after the first
2457 // non-phi, instruction in the normal successor block.
2458 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2459 BasicBlock::iterator I = II->getNormalDest()->begin();
2460 while (isa<PHINode>(I)) ++I;
2461 InsertNewInstBefore(NC, *I);
2463 // Otherwise, it's a call, just insert cast right after the call instr
2464 InsertNewInstBefore(NC, *Caller);
2466 AddUsersToWorkList(*Caller);
2468 NV = Constant::getNullValue(Caller->getType());
2472 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2473 Caller->replaceAllUsesWith(NV);
2474 Caller->getParent()->getInstList().erase(Caller);
2475 removeFromWorkList(Caller);
2481 // PHINode simplification
2483 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2484 if (Value *V = hasConstantValue(&PN))
2485 return ReplaceInstUsesWith(PN, V);
2487 // If the only user of this instruction is a cast instruction, and all of the
2488 // incoming values are constants, change this PHI to merge together the casted
2491 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2492 if (CI->getType() != PN.getType()) { // noop casts will be folded
2493 bool AllConstant = true;
2494 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2495 if (!isa<Constant>(PN.getIncomingValue(i))) {
2496 AllConstant = false;
2500 // Make a new PHI with all casted values.
2501 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2502 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2503 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2504 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2505 PN.getIncomingBlock(i));
2508 // Update the cast instruction.
2509 CI->setOperand(0, New);
2510 WorkList.push_back(CI); // revisit the cast instruction to fold.
2511 WorkList.push_back(New); // Make sure to revisit the new Phi
2512 return &PN; // PN is now dead!
2518 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
2519 Instruction *InsertPoint,
2521 unsigned PS = IC->getTargetData().getPointerSize();
2522 const Type *VTy = V->getType();
2524 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
2525 // We must insert a cast to ensure we sign-extend.
2526 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
2527 V->getName()), *InsertPoint);
2528 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
2533 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2534 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2535 // If so, eliminate the noop.
2536 if (GEP.getNumOperands() == 1)
2537 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2539 bool HasZeroPointerIndex = false;
2540 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2541 HasZeroPointerIndex = C->isNullValue();
2543 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2544 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2546 // Eliminate unneeded casts for indices.
2547 bool MadeChange = false;
2548 gep_type_iterator GTI = gep_type_begin(GEP);
2549 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
2550 if (isa<SequentialType>(*GTI)) {
2551 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
2552 Value *Src = CI->getOperand(0);
2553 const Type *SrcTy = Src->getType();
2554 const Type *DestTy = CI->getType();
2555 if (Src->getType()->isInteger()) {
2556 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
2557 // We can always eliminate a cast from ulong or long to the other.
2558 // We can always eliminate a cast from uint to int or the other on
2559 // 32-bit pointer platforms.
2560 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
2562 GEP.setOperand(i, Src);
2564 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2565 SrcTy->getPrimitiveSize() == 4) {
2566 // We can always eliminate a cast from int to [u]long. We can
2567 // eliminate a cast from uint to [u]long iff the target is a 32-bit
2569 if (SrcTy->isSigned() ||
2570 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
2572 GEP.setOperand(i, Src);
2577 // If we are using a wider index than needed for this platform, shrink it
2578 // to what we need. If the incoming value needs a cast instruction,
2579 // insert it. This explicit cast can make subsequent optimizations more
2581 Value *Op = GEP.getOperand(i);
2582 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
2583 if (Constant *C = dyn_cast<Constant>(Op)) {
2584 GEP.setOperand(i, ConstantExpr::getCast(C, TD->getIntPtrType()));
2587 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
2588 Op->getName()), GEP);
2589 GEP.setOperand(i, Op);
2593 if (MadeChange) return &GEP;
2595 // Combine Indices - If the source pointer to this getelementptr instruction
2596 // is a getelementptr instruction, combine the indices of the two
2597 // getelementptr instructions into a single instruction.
2599 std::vector<Value*> SrcGEPOperands;
2600 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2601 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2602 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2603 if (CE->getOpcode() == Instruction::GetElementPtr)
2604 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2607 if (!SrcGEPOperands.empty()) {
2608 std::vector<Value *> Indices;
2610 // Can we combine the two pointer arithmetics offsets?
2611 if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
2612 isa<Constant>(GEP.getOperand(1))) {
2613 Constant *SGC = cast<Constant>(SrcGEPOperands[1]);
2614 Constant *GC = cast<Constant>(GEP.getOperand(1));
2615 if (SGC->getType() != GC->getType()) {
2616 SGC = ConstantExpr::getSignExtend(SGC, Type::LongTy);
2617 GC = ConstantExpr::getSignExtend(GC, Type::LongTy);
2620 // Replace: gep (gep %P, long C1), long C2, ...
2621 // With: gep %P, long (C1+C2), ...
2622 GEP.setOperand(0, SrcGEPOperands[0]);
2623 GEP.setOperand(1, ConstantExpr::getAdd(SGC, GC));
2624 if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
2625 AddUsersToWorkList(*I); // Reduce use count of Src
2627 } else if (SrcGEPOperands.size() == 2) {
2628 // Replace: gep (gep %P, long B), long A, ...
2629 // With: T = long A+B; gep %P, T, ...
2631 // Note that if our source is a gep chain itself that we wait for that
2632 // chain to be resolved before we perform this transformation. This
2633 // avoids us creating a TON of code in some cases.
2635 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2636 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2637 return 0; // Wait until our source is folded to completion.
2639 Value *Sum, *SO1 = SrcGEPOperands[1], *GO1 = GEP.getOperand(1);
2640 if (SO1 == Constant::getNullValue(SO1->getType())) {
2642 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
2645 // If they aren't the same type, convert both to an integer of the
2646 // target's pointer size.
2647 if (SO1->getType() != GO1->getType()) {
2648 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
2649 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
2650 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
2651 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
2653 unsigned PS = TD->getPointerSize();
2655 if (SO1->getType()->getPrimitiveSize() == PS) {
2656 // Convert GO1 to SO1's type.
2657 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
2659 } else if (GO1->getType()->getPrimitiveSize() == PS) {
2660 // Convert SO1 to GO1's type.
2661 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
2663 const Type *PT = TD->getIntPtrType();
2664 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
2665 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
2669 Sum = BinaryOperator::create(Instruction::Add, SO1, GO1,
2670 GEP.getOperand(0)->getName()+".sum", &GEP);
2671 WorkList.push_back(cast<Instruction>(Sum));
2673 GEP.setOperand(0, SrcGEPOperands[0]);
2674 GEP.setOperand(1, Sum);
2676 } else if (isa<Constant>(*GEP.idx_begin()) &&
2677 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
2678 SrcGEPOperands.size() != 1) {
2679 // Otherwise we can do the fold if the first index of the GEP is a zero
2680 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2681 SrcGEPOperands.end());
2682 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2683 } else if (SrcGEPOperands.back() ==
2684 Constant::getNullValue(SrcGEPOperands.back()->getType())) {
2685 // We have to check to make sure this really is an ARRAY index we are
2686 // ending up with, not a struct index.
2687 generic_gep_type_iterator<std::vector<Value*>::iterator>
2688 GTI = gep_type_begin(SrcGEPOperands[0]->getType(),
2689 SrcGEPOperands.begin()+1, SrcGEPOperands.end());
2690 std::advance(GTI, SrcGEPOperands.size()-2);
2691 if (isa<SequentialType>(*GTI)) {
2692 // If the src gep ends with a constant array index, merge this get into
2693 // it, even if we have a non-zero array index.
2694 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2695 SrcGEPOperands.end()-1);
2696 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2700 if (!Indices.empty())
2701 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2703 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2704 // GEP of global variable. If all of the indices for this GEP are
2705 // constants, we can promote this to a constexpr instead of an instruction.
2707 // Scan for nonconstants...
2708 std::vector<Constant*> Indices;
2709 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2710 for (; I != E && isa<Constant>(*I); ++I)
2711 Indices.push_back(cast<Constant>(*I));
2713 if (I == E) { // If they are all constants...
2715 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2717 // Replace all uses of the GEP with the new constexpr...
2718 return ReplaceInstUsesWith(GEP, CE);
2720 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2721 if (CE->getOpcode() == Instruction::Cast) {
2722 if (HasZeroPointerIndex) {
2723 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2724 // into : GEP [10 x ubyte]* X, long 0, ...
2726 // This occurs when the program declares an array extern like "int X[];"
2728 Constant *X = CE->getOperand(0);
2729 const PointerType *CPTy = cast<PointerType>(CE->getType());
2730 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2731 if (const ArrayType *XATy =
2732 dyn_cast<ArrayType>(XTy->getElementType()))
2733 if (const ArrayType *CATy =
2734 dyn_cast<ArrayType>(CPTy->getElementType()))
2735 if (CATy->getElementType() == XATy->getElementType()) {
2736 // At this point, we know that the cast source type is a pointer
2737 // to an array of the same type as the destination pointer
2738 // array. Because the array type is never stepped over (there
2739 // is a leading zero) we can fold the cast into this GEP.
2740 GEP.setOperand(0, X);
2750 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2751 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2752 if (AI.isArrayAllocation()) // Check C != 1
2753 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2754 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2755 AllocationInst *New = 0;
2757 // Create and insert the replacement instruction...
2758 if (isa<MallocInst>(AI))
2759 New = new MallocInst(NewTy, 0, AI.getName());
2761 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2762 New = new AllocaInst(NewTy, 0, AI.getName());
2765 InsertNewInstBefore(New, AI);
2767 // Scan to the end of the allocation instructions, to skip over a block of
2768 // allocas if possible...
2770 BasicBlock::iterator It = New;
2771 while (isa<AllocationInst>(*It)) ++It;
2773 // Now that I is pointing to the first non-allocation-inst in the block,
2774 // insert our getelementptr instruction...
2776 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
2777 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2779 // Now make everything use the getelementptr instead of the original
2781 return ReplaceInstUsesWith(AI, V);
2784 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2785 // Note that we only do this for alloca's, because malloc should allocate and
2786 // return a unique pointer, even for a zero byte allocation.
2787 if (isa<AllocaInst>(AI) && TD->getTypeSize(AI.getAllocatedType()) == 0)
2788 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2793 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2794 Value *Op = FI.getOperand(0);
2796 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2797 if (CastInst *CI = dyn_cast<CastInst>(Op))
2798 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2799 FI.setOperand(0, CI->getOperand(0));
2803 // If we have 'free null' delete the instruction. This can happen in stl code
2804 // when lots of inlining happens.
2805 if (isa<ConstantPointerNull>(Op))
2806 return EraseInstFromFunction(FI);
2812 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2813 /// constantexpr, return the constant value being addressed by the constant
2814 /// expression, or null if something is funny.
2816 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2817 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
2818 return 0; // Do not allow stepping over the value!
2820 // Loop over all of the operands, tracking down which value we are
2822 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2823 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2824 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2825 if (CS == 0) return 0;
2826 if (CU->getValue() >= CS->getValues().size()) return 0;
2827 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2828 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2829 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2830 if (CA == 0) return 0;
2831 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2832 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2838 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2839 Value *Op = LI.getOperand(0);
2840 if (LI.isVolatile()) return 0;
2842 if (Constant *C = dyn_cast<Constant>(Op))
2843 if (C->isNullValue()) // load null -> 0
2844 return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
2845 else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
2846 Op = CPR->getValue();
2848 // Instcombine load (constant global) into the value loaded...
2849 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2850 if (GV->isConstant() && !GV->isExternal())
2851 return ReplaceInstUsesWith(LI, GV->getInitializer());
2853 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2854 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2855 if (CE->getOpcode() == Instruction::GetElementPtr)
2856 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2857 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2858 if (GV->isConstant() && !GV->isExternal())
2859 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2860 return ReplaceInstUsesWith(LI, V);
2862 // load (cast X) --> cast (load X) iff safe
2863 if (CastInst *CI = dyn_cast<CastInst>(Op)) {
2864 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
2865 if (const PointerType *SrcTy =
2866 dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
2867 const Type *SrcPTy = SrcTy->getElementType();
2868 if (TD->getTypeSize(SrcPTy) == TD->getTypeSize(DestPTy) &&
2869 (SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
2870 (DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
2871 // Okay, we are casting from one integer or pointer type to another of
2872 // the same size. Instead of casting the pointer before the load, cast
2873 // the result of the loaded value.
2874 Value *NewLoad = InsertNewInstBefore(new LoadInst(CI->getOperand(0),
2875 CI->getName()), LI);
2876 // Now cast the result of the load.
2877 return new CastInst(NewLoad, LI.getType());
2886 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2887 // Change br (not X), label True, label False to: br X, label False, True
2888 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
2889 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2890 BasicBlock *TrueDest = BI.getSuccessor(0);
2891 BasicBlock *FalseDest = BI.getSuccessor(1);
2892 // Swap Destinations and condition...
2894 BI.setSuccessor(0, FalseDest);
2895 BI.setSuccessor(1, TrueDest);
2897 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
2898 // Cannonicalize setne -> seteq
2899 if ((I->getOpcode() == Instruction::SetNE ||
2900 I->getOpcode() == Instruction::SetLE ||
2901 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
2902 std::string Name = I->getName(); I->setName("");
2903 Instruction::BinaryOps NewOpcode =
2904 SetCondInst::getInverseCondition(I->getOpcode());
2905 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
2906 I->getOperand(1), Name, I);
2907 BasicBlock *TrueDest = BI.getSuccessor(0);
2908 BasicBlock *FalseDest = BI.getSuccessor(1);
2909 // Swap Destinations and condition...
2910 BI.setCondition(NewSCC);
2911 BI.setSuccessor(0, FalseDest);
2912 BI.setSuccessor(1, TrueDest);
2913 removeFromWorkList(I);
2914 I->getParent()->getInstList().erase(I);
2915 WorkList.push_back(cast<Instruction>(NewSCC));
2924 void InstCombiner::removeFromWorkList(Instruction *I) {
2925 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2929 bool InstCombiner::runOnFunction(Function &F) {
2930 bool Changed = false;
2931 TD = &getAnalysis<TargetData>();
2933 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2935 while (!WorkList.empty()) {
2936 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2937 WorkList.pop_back();
2939 // Check to see if we can DCE or ConstantPropagate the instruction...
2940 // Check to see if we can DIE the instruction...
2941 if (isInstructionTriviallyDead(I)) {
2942 // Add operands to the worklist...
2943 if (I->getNumOperands() < 4)
2944 AddUsesToWorkList(*I);
2947 I->getParent()->getInstList().erase(I);
2948 removeFromWorkList(I);
2952 // Instruction isn't dead, see if we can constant propagate it...
2953 if (Constant *C = ConstantFoldInstruction(I)) {
2954 // Add operands to the worklist...
2955 AddUsesToWorkList(*I);
2956 ReplaceInstUsesWith(*I, C);
2959 I->getParent()->getInstList().erase(I);
2960 removeFromWorkList(I);
2964 // Check to see if any of the operands of this instruction are a
2965 // ConstantPointerRef. Since they sneak in all over the place and inhibit
2966 // optimization, we want to strip them out unconditionally!
2967 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2968 if (ConstantPointerRef *CPR =
2969 dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
2970 I->setOperand(i, CPR->getValue());
2974 // Now that we have an instruction, try combining it to simplify it...
2975 if (Instruction *Result = visit(*I)) {
2977 // Should we replace the old instruction with a new one?
2979 DEBUG(std::cerr << "IC: Old = " << *I
2980 << " New = " << *Result);
2982 // Instructions can end up on the worklist more than once. Make sure
2983 // we do not process an instruction that has been deleted.
2984 removeFromWorkList(I);
2986 // Move the name to the new instruction first...
2987 std::string OldName = I->getName(); I->setName("");
2988 Result->setName(OldName);
2990 // Insert the new instruction into the basic block...
2991 BasicBlock *InstParent = I->getParent();
2992 InstParent->getInstList().insert(I, Result);
2994 // Everything uses the new instruction now...
2995 I->replaceAllUsesWith(Result);
2997 // Erase the old instruction.
2998 InstParent->getInstList().erase(I);
3000 DEBUG(std::cerr << "IC: MOD = " << *I);
3002 BasicBlock::iterator II = I;
3004 // If the instruction was modified, it's possible that it is now dead.
3005 // if so, remove it.
3006 if (dceInstruction(II)) {
3007 // Instructions may end up in the worklist more than once. Erase them
3009 removeFromWorkList(I);
3015 WorkList.push_back(Result);
3016 AddUsersToWorkList(*Result);
3025 Pass *llvm::createInstructionCombiningPass() {
3026 return new InstCombiner();