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) {
852 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
854 if (RHS->equalsInt(1))
855 return ReplaceInstUsesWith(I, I.getOperand(0));
858 if (RHS->isAllOnesValue())
859 return BinaryOperator::createNeg(I.getOperand(0));
861 // Check to see if this is an unsigned division with an exact power of 2,
862 // if so, convert to a right shift.
863 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
864 if (uint64_t Val = C->getValue()) // Don't break X / 0
865 if (uint64_t C = Log2(Val))
866 return new ShiftInst(Instruction::Shr, I.getOperand(0),
867 ConstantUInt::get(Type::UByteTy, C));
870 // 0 / X == 0, we don't need to preserve faults!
871 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
872 if (LHS->equalsInt(0))
873 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
879 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
880 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
881 if (RHS->equalsInt(1)) // X % 1 == 0
882 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
883 if (RHS->isAllOnesValue()) // X % -1 == 0
884 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
886 // Check to see if this is an unsigned remainder with an exact power of 2,
887 // if so, convert to a bitwise and.
888 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
889 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
891 return BinaryOperator::create(Instruction::And, I.getOperand(0),
892 ConstantUInt::get(I.getType(), Val-1));
895 // 0 % X == 0, we don't need to preserve faults!
896 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
897 if (LHS->equalsInt(0))
898 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
903 // isMaxValueMinusOne - return true if this is Max-1
904 static bool isMaxValueMinusOne(const ConstantInt *C) {
905 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
906 // Calculate -1 casted to the right type...
907 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
908 uint64_t Val = ~0ULL; // All ones
909 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
910 return CU->getValue() == Val-1;
913 const ConstantSInt *CS = cast<ConstantSInt>(C);
915 // Calculate 0111111111..11111
916 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
917 int64_t Val = INT64_MAX; // All ones
918 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
919 return CS->getValue() == Val-1;
922 // isMinValuePlusOne - return true if this is Min+1
923 static bool isMinValuePlusOne(const ConstantInt *C) {
924 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
925 return CU->getValue() == 1;
927 const ConstantSInt *CS = cast<ConstantSInt>(C);
929 // Calculate 1111111111000000000000
930 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
931 int64_t Val = -1; // All ones
932 Val <<= TypeBits-1; // Shift over to the right spot
933 return CS->getValue() == Val+1;
936 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
937 /// are carefully arranged to allow folding of expressions such as:
939 /// (A < B) | (A > B) --> (A != B)
941 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
942 /// represents that the comparison is true if A == B, and bit value '1' is true
945 static unsigned getSetCondCode(const SetCondInst *SCI) {
946 switch (SCI->getOpcode()) {
948 case Instruction::SetGT: return 1;
949 case Instruction::SetEQ: return 2;
950 case Instruction::SetGE: return 3;
951 case Instruction::SetLT: return 4;
952 case Instruction::SetNE: return 5;
953 case Instruction::SetLE: return 6;
956 assert(0 && "Invalid SetCC opcode!");
961 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
962 /// opcode and two operands into either a constant true or false, or a brand new
963 /// SetCC instruction.
964 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
966 case 0: return ConstantBool::False;
967 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
968 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
969 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
970 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
971 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
972 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
973 case 7: return ConstantBool::True;
974 default: assert(0 && "Illegal SetCCCode!"); return 0;
978 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
979 struct FoldSetCCLogical {
982 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
983 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
984 bool shouldApply(Value *V) const {
985 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
986 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
987 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
990 Instruction *apply(BinaryOperator &Log) const {
991 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
992 if (SCI->getOperand(0) != LHS) {
993 assert(SCI->getOperand(1) == LHS);
994 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
997 unsigned LHSCode = getSetCondCode(SCI);
998 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
1000 switch (Log.getOpcode()) {
1001 case Instruction::And: Code = LHSCode & RHSCode; break;
1002 case Instruction::Or: Code = LHSCode | RHSCode; break;
1003 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
1004 default: assert(0 && "Illegal logical opcode!"); return 0;
1007 Value *RV = getSetCCValue(Code, LHS, RHS);
1008 if (Instruction *I = dyn_cast<Instruction>(RV))
1010 // Otherwise, it's a constant boolean value...
1011 return IC.ReplaceInstUsesWith(Log, RV);
1016 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
1017 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
1018 // guaranteed to be either a shift instruction or a binary operator.
1019 Instruction *InstCombiner::OptAndOp(Instruction *Op,
1020 ConstantIntegral *OpRHS,
1021 ConstantIntegral *AndRHS,
1022 BinaryOperator &TheAnd) {
1023 Value *X = Op->getOperand(0);
1024 Constant *Together = 0;
1025 if (!isa<ShiftInst>(Op))
1026 Together = ConstantExpr::get(Instruction::And, AndRHS, OpRHS);
1028 switch (Op->getOpcode()) {
1029 case Instruction::Xor:
1030 if (Together->isNullValue()) {
1031 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
1032 return BinaryOperator::create(Instruction::And, X, AndRHS);
1033 } else if (Op->hasOneUse()) {
1034 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
1035 std::string OpName = Op->getName(); Op->setName("");
1036 Instruction *And = BinaryOperator::create(Instruction::And,
1038 InsertNewInstBefore(And, TheAnd);
1039 return BinaryOperator::create(Instruction::Xor, And, Together);
1042 case Instruction::Or:
1043 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
1044 if (Together->isNullValue())
1045 return BinaryOperator::create(Instruction::And, X, AndRHS);
1047 if (Together == AndRHS) // (X | C) & C --> C
1048 return ReplaceInstUsesWith(TheAnd, AndRHS);
1050 if (Op->hasOneUse() && Together != OpRHS) {
1051 // (X | C1) & C2 --> (X | (C1&C2)) & C2
1052 std::string Op0Name = Op->getName(); Op->setName("");
1053 Instruction *Or = BinaryOperator::create(Instruction::Or, X,
1055 InsertNewInstBefore(Or, TheAnd);
1056 return BinaryOperator::create(Instruction::And, Or, AndRHS);
1060 case Instruction::Add:
1061 if (Op->hasOneUse()) {
1062 // Adding a one to a single bit bit-field should be turned into an XOR
1063 // of the bit. First thing to check is to see if this AND is with a
1064 // single bit constant.
1065 unsigned long long AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1067 // Clear bits that are not part of the constant.
1068 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
1070 // If there is only one bit set...
1071 if ((AndRHSV & (AndRHSV-1)) == 0) {
1072 // Ok, at this point, we know that we are masking the result of the
1073 // ADD down to exactly one bit. If the constant we are adding has
1074 // no bits set below this bit, then we can eliminate the ADD.
1075 unsigned long long AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1077 // Check to see if any bits below the one bit set in AndRHSV are set.
1078 if ((AddRHS & (AndRHSV-1)) == 0) {
1079 // If not, the only thing that can effect the output of the AND is
1080 // the bit specified by AndRHSV. If that bit is set, the effect of
1081 // the XOR is to toggle the bit. If it is clear, then the ADD has
1083 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1084 TheAnd.setOperand(0, X);
1087 std::string Name = Op->getName(); Op->setName("");
1088 // Pull the XOR out of the AND.
1089 Instruction *NewAnd =
1090 BinaryOperator::create(Instruction::And, X, AndRHS, Name);
1091 InsertNewInstBefore(NewAnd, TheAnd);
1092 return BinaryOperator::create(Instruction::Xor, NewAnd, AndRHS);
1099 case Instruction::Shl: {
1100 // We know that the AND will not produce any of the bits shifted in, so if
1101 // the anded constant includes them, clear them now!
1103 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1104 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1105 ConstantExpr::get(Instruction::Shl, AllOne, OpRHS));
1107 TheAnd.setOperand(1, CI);
1112 case Instruction::Shr:
1113 // We know that the AND will not produce any of the bits shifted in, so if
1114 // the anded constant includes them, clear them now! This only applies to
1115 // unsigned shifts, because a signed shr may bring in set bits!
1117 if (AndRHS->getType()->isUnsigned()) {
1118 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1119 Constant *CI = ConstantExpr::get(Instruction::And, AndRHS,
1120 ConstantExpr::get(Instruction::Shr, AllOne, OpRHS));
1122 TheAnd.setOperand(1, CI);
1132 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1133 bool Changed = SimplifyCommutative(I);
1134 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1136 // and X, X = X and X, 0 == 0
1137 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1138 return ReplaceInstUsesWith(I, Op1);
1141 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1142 if (RHS->isAllOnesValue())
1143 return ReplaceInstUsesWith(I, Op0);
1145 // Optimize a variety of ((val OP C1) & C2) combinations...
1146 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1147 Instruction *Op0I = cast<Instruction>(Op0);
1148 Value *X = Op0I->getOperand(0);
1149 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1150 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1154 // Try to fold constant and into select arguments.
1155 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1156 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1160 Value *Op0NotVal = dyn_castNotVal(Op0);
1161 Value *Op1NotVal = dyn_castNotVal(Op1);
1163 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1164 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1165 Instruction *Or = BinaryOperator::create(Instruction::Or, Op0NotVal,
1166 Op1NotVal,I.getName()+".demorgan");
1167 InsertNewInstBefore(Or, I);
1168 return BinaryOperator::createNot(Or);
1171 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1172 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1174 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1175 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1176 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1179 return Changed ? &I : 0;
1184 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1185 bool Changed = SimplifyCommutative(I);
1186 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1188 // or X, X = X or X, 0 == X
1189 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1190 return ReplaceInstUsesWith(I, Op0);
1193 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1194 if (RHS->isAllOnesValue())
1195 return ReplaceInstUsesWith(I, Op1);
1197 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1198 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1199 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1200 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1201 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1202 Instruction *Or = BinaryOperator::create(Instruction::Or,
1203 Op0I->getOperand(0), RHS,
1205 InsertNewInstBefore(Or, I);
1206 return BinaryOperator::create(Instruction::And, Or,
1207 ConstantExpr::get(Instruction::Or, RHS, Op0CI));
1210 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1211 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1212 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1213 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1214 Instruction *Or = BinaryOperator::create(Instruction::Or,
1215 Op0I->getOperand(0), RHS,
1217 InsertNewInstBefore(Or, I);
1218 return BinaryOperator::create(Instruction::Xor, Or,
1219 ConstantExpr::get(Instruction::And, Op0CI,
1224 // Try to fold constant and into select arguments.
1225 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1226 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1230 // (A & C1)|(A & C2) == A & (C1|C2)
1231 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1232 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1233 if (LHS->getOperand(0) == RHS->getOperand(0))
1234 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1235 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1236 return BinaryOperator::create(Instruction::And, LHS->getOperand(0),
1237 ConstantExpr::get(Instruction::Or, C0, C1));
1239 Value *Op0NotVal = dyn_castNotVal(Op0);
1240 Value *Op1NotVal = dyn_castNotVal(Op1);
1242 if (Op1 == Op0NotVal) // ~A | A == -1
1243 return ReplaceInstUsesWith(I,
1244 ConstantIntegral::getAllOnesValue(I.getType()));
1246 if (Op0 == Op1NotVal) // A | ~A == -1
1247 return ReplaceInstUsesWith(I,
1248 ConstantIntegral::getAllOnesValue(I.getType()));
1250 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1251 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1252 Instruction *And = BinaryOperator::create(Instruction::And, Op0NotVal,
1253 Op1NotVal,I.getName()+".demorgan",
1255 WorkList.push_back(And);
1256 return BinaryOperator::createNot(And);
1259 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1260 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1261 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1264 return Changed ? &I : 0;
1267 // XorSelf - Implements: X ^ X --> 0
1270 XorSelf(Value *rhs) : RHS(rhs) {}
1271 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1272 Instruction *apply(BinaryOperator &Xor) const {
1278 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1279 bool Changed = SimplifyCommutative(I);
1280 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1282 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1283 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1284 assert(Result == &I && "AssociativeOpt didn't work?");
1285 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1288 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1290 if (RHS->isNullValue())
1291 return ReplaceInstUsesWith(I, Op0);
1293 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1294 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1295 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1296 if (RHS == ConstantBool::True && SCI->hasOneUse())
1297 return new SetCondInst(SCI->getInverseCondition(),
1298 SCI->getOperand(0), SCI->getOperand(1));
1300 // ~(c-X) == X-c-1 == X+(-c-1)
1301 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1302 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1303 Constant *NegOp0I0C = ConstantExpr::get(Instruction::Sub,
1304 Constant::getNullValue(Op0I0C->getType()), Op0I0C);
1305 Constant *ConstantRHS = ConstantExpr::get(Instruction::Sub, NegOp0I0C,
1306 ConstantInt::get(I.getType(), 1));
1307 return BinaryOperator::create(Instruction::Add, Op0I->getOperand(1),
1311 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1312 switch (Op0I->getOpcode()) {
1313 case Instruction::Add:
1314 // ~(X-c) --> (-c-1)-X
1315 if (RHS->isAllOnesValue()) {
1316 Constant *NegOp0CI = ConstantExpr::get(Instruction::Sub,
1317 Constant::getNullValue(Op0CI->getType()), Op0CI);
1318 return BinaryOperator::create(Instruction::Sub,
1319 ConstantExpr::get(Instruction::Sub, NegOp0CI,
1320 ConstantInt::get(I.getType(), 1)),
1321 Op0I->getOperand(0));
1324 case Instruction::And:
1325 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1326 if (ConstantExpr::get(Instruction::And, RHS, Op0CI)->isNullValue())
1327 return BinaryOperator::create(Instruction::Or, Op0, RHS);
1329 case Instruction::Or:
1330 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1331 if (ConstantExpr::get(Instruction::And, RHS, Op0CI) == RHS)
1332 return BinaryOperator::create(Instruction::And, Op0,
1339 // Try to fold constant and into select arguments.
1340 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1341 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1345 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1347 return ReplaceInstUsesWith(I,
1348 ConstantIntegral::getAllOnesValue(I.getType()));
1350 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1352 return ReplaceInstUsesWith(I,
1353 ConstantIntegral::getAllOnesValue(I.getType()));
1355 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1356 if (Op1I->getOpcode() == Instruction::Or) {
1357 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1358 cast<BinaryOperator>(Op1I)->swapOperands();
1360 std::swap(Op0, Op1);
1361 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1363 std::swap(Op0, Op1);
1365 } else if (Op1I->getOpcode() == Instruction::Xor) {
1366 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1367 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1368 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1369 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1372 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1373 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1374 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1375 cast<BinaryOperator>(Op0I)->swapOperands();
1376 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1377 Value *NotB = BinaryOperator::createNot(Op1, Op1->getName()+".not", &I);
1378 WorkList.push_back(cast<Instruction>(NotB));
1379 return BinaryOperator::create(Instruction::And, Op0I->getOperand(0),
1382 } else if (Op0I->getOpcode() == Instruction::Xor) {
1383 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1384 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1385 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1386 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1389 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1390 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1391 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1392 if (ConstantExpr::get(Instruction::And, C1, C2)->isNullValue())
1393 return BinaryOperator::create(Instruction::Or, Op0, Op1);
1395 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1396 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1397 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1400 return Changed ? &I : 0;
1403 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1404 static Constant *AddOne(ConstantInt *C) {
1405 Constant *Result = ConstantExpr::get(Instruction::Add, C,
1406 ConstantInt::get(C->getType(), 1));
1407 assert(Result && "Constant folding integer addition failed!");
1410 static Constant *SubOne(ConstantInt *C) {
1411 Constant *Result = ConstantExpr::get(Instruction::Sub, C,
1412 ConstantInt::get(C->getType(), 1));
1413 assert(Result && "Constant folding integer addition failed!");
1417 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1418 // true when both operands are equal...
1420 static bool isTrueWhenEqual(Instruction &I) {
1421 return I.getOpcode() == Instruction::SetEQ ||
1422 I.getOpcode() == Instruction::SetGE ||
1423 I.getOpcode() == Instruction::SetLE;
1426 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1427 bool Changed = SimplifyCommutative(I);
1428 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1429 const Type *Ty = Op0->getType();
1433 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1435 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1436 if (isa<ConstantPointerNull>(Op1) &&
1437 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1438 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1441 // setcc's with boolean values can always be turned into bitwise operations
1442 if (Ty == Type::BoolTy) {
1443 // If this is <, >, or !=, we can change this into a simple xor instruction
1444 if (!isTrueWhenEqual(I))
1445 return BinaryOperator::create(Instruction::Xor, Op0, Op1);
1447 // Otherwise we need to make a temporary intermediate instruction and insert
1448 // it into the instruction stream. This is what we are after:
1450 // seteq bool %A, %B -> ~(A^B)
1451 // setle bool %A, %B -> ~A | B
1452 // setge bool %A, %B -> A | ~B
1454 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1455 Instruction *Xor = BinaryOperator::create(Instruction::Xor, Op0, Op1,
1457 InsertNewInstBefore(Xor, I);
1458 return BinaryOperator::createNot(Xor);
1461 // Handle the setXe cases...
1462 assert(I.getOpcode() == Instruction::SetGE ||
1463 I.getOpcode() == Instruction::SetLE);
1465 if (I.getOpcode() == Instruction::SetGE)
1466 std::swap(Op0, Op1); // Change setge -> setle
1468 // Now we just have the SetLE case.
1469 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1470 InsertNewInstBefore(Not, I);
1471 return BinaryOperator::create(Instruction::Or, Not, Op1);
1474 // Check to see if we are doing one of many comparisons against constant
1475 // integers at the end of their ranges...
1477 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1478 // Simplify seteq and setne instructions...
1479 if (I.getOpcode() == Instruction::SetEQ ||
1480 I.getOpcode() == Instruction::SetNE) {
1481 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1483 // If the first operand is (and|or|xor) with a constant, and the second
1484 // operand is a constant, simplify a bit.
1485 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1486 switch (BO->getOpcode()) {
1487 case Instruction::Add:
1488 if (CI->isNullValue()) {
1489 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1490 // efficiently invertible, or if the add has just this one use.
1491 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1492 if (Value *NegVal = dyn_castNegVal(BOp1))
1493 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1494 else if (Value *NegVal = dyn_castNegVal(BOp0))
1495 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1496 else if (BO->hasOneUse()) {
1497 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1499 InsertNewInstBefore(Neg, I);
1500 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1504 case Instruction::Xor:
1505 // For the xor case, we can xor two constants together, eliminating
1506 // the explicit xor.
1507 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1508 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1509 ConstantExpr::get(Instruction::Xor, CI, BOC));
1512 case Instruction::Sub:
1513 // Replace (([sub|xor] A, B) != 0) with (A != B)
1514 if (CI->isNullValue())
1515 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1519 case Instruction::Or:
1520 // If bits are being or'd in that are not present in the constant we
1521 // are comparing against, then the comparison could never succeed!
1522 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1523 Constant *NotCI = NotConstant(CI);
1524 if (!ConstantExpr::get(Instruction::And, BOC, NotCI)->isNullValue())
1525 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1529 case Instruction::And:
1530 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1531 // If bits are being compared against that are and'd out, then the
1532 // comparison can never succeed!
1533 if (!ConstantExpr::get(Instruction::And, CI,
1534 NotConstant(BOC))->isNullValue())
1535 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1537 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1538 // to be a signed value as appropriate.
1539 if (isSignBit(BOC)) {
1540 Value *X = BO->getOperand(0);
1541 // If 'X' is not signed, insert a cast now...
1542 if (!BOC->getType()->isSigned()) {
1543 const Type *DestTy = getSignedIntegralType(BOC->getType());
1544 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1545 InsertNewInstBefore(NewCI, I);
1548 return new SetCondInst(isSetNE ? Instruction::SetLT :
1549 Instruction::SetGE, X,
1550 Constant::getNullValue(X->getType()));
1556 } else { // Not a SetEQ/SetNE
1557 // If the LHS is a cast from an integral value of the same size,
1558 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1559 Value *CastOp = Cast->getOperand(0);
1560 const Type *SrcTy = CastOp->getType();
1561 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1562 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1563 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1564 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1565 "Source and destination signednesses should differ!");
1566 if (Cast->getType()->isSigned()) {
1567 // If this is a signed comparison, check for comparisons in the
1568 // vicinity of zero.
1569 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1571 return BinaryOperator::create(Instruction::SetGT, CastOp,
1572 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1573 else if (I.getOpcode() == Instruction::SetGT &&
1574 cast<ConstantSInt>(CI)->getValue() == -1)
1575 // X > -1 => x < 128
1576 return BinaryOperator::create(Instruction::SetLT, CastOp,
1577 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1579 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1580 if (I.getOpcode() == Instruction::SetLT &&
1581 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1582 // X < 128 => X > -1
1583 return BinaryOperator::create(Instruction::SetGT, CastOp,
1584 ConstantSInt::get(SrcTy, -1));
1585 else if (I.getOpcode() == Instruction::SetGT &&
1586 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1588 return BinaryOperator::create(Instruction::SetLT, CastOp,
1589 Constant::getNullValue(SrcTy));
1595 // Check to see if we are comparing against the minimum or maximum value...
1596 if (CI->isMinValue()) {
1597 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1598 return ReplaceInstUsesWith(I, ConstantBool::False);
1599 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1600 return ReplaceInstUsesWith(I, ConstantBool::True);
1601 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1602 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1603 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1604 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1606 } else if (CI->isMaxValue()) {
1607 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1608 return ReplaceInstUsesWith(I, ConstantBool::False);
1609 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1610 return ReplaceInstUsesWith(I, ConstantBool::True);
1611 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1612 return BinaryOperator::create(Instruction::SetEQ, Op0, Op1);
1613 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1614 return BinaryOperator::create(Instruction::SetNE, Op0, Op1);
1616 // Comparing against a value really close to min or max?
1617 } else if (isMinValuePlusOne(CI)) {
1618 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1619 return BinaryOperator::create(Instruction::SetEQ, Op0, SubOne(CI));
1620 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1621 return BinaryOperator::create(Instruction::SetNE, Op0, SubOne(CI));
1623 } else if (isMaxValueMinusOne(CI)) {
1624 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1625 return BinaryOperator::create(Instruction::SetEQ, Op0, AddOne(CI));
1626 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1627 return BinaryOperator::create(Instruction::SetNE, Op0, AddOne(CI));
1630 // If we still have a setle or setge instruction, turn it into the
1631 // appropriate setlt or setgt instruction. Since the border cases have
1632 // already been handled above, this requires little checking.
1634 if (I.getOpcode() == Instruction::SetLE)
1635 return BinaryOperator::create(Instruction::SetLT, Op0, AddOne(CI));
1636 if (I.getOpcode() == Instruction::SetGE)
1637 return BinaryOperator::create(Instruction::SetGT, Op0, SubOne(CI));
1640 // Test to see if the operands of the setcc are casted versions of other
1641 // values. If the cast can be stripped off both arguments, we do so now.
1642 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1643 Value *CastOp0 = CI->getOperand(0);
1644 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1645 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1646 (I.getOpcode() == Instruction::SetEQ ||
1647 I.getOpcode() == Instruction::SetNE)) {
1648 // We keep moving the cast from the left operand over to the right
1649 // operand, where it can often be eliminated completely.
1652 // If operand #1 is a cast instruction, see if we can eliminate it as
1654 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1655 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1657 Op1 = CI2->getOperand(0);
1659 // If Op1 is a constant, we can fold the cast into the constant.
1660 if (Op1->getType() != Op0->getType())
1661 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1662 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1664 // Otherwise, cast the RHS right before the setcc
1665 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1666 InsertNewInstBefore(cast<Instruction>(Op1), I);
1668 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1671 // Handle the special case of: setcc (cast bool to X), <cst>
1672 // This comes up when you have code like
1675 // For generality, we handle any zero-extension of any operand comparison
1677 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1678 const Type *SrcTy = CastOp0->getType();
1679 const Type *DestTy = Op0->getType();
1680 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1681 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1682 // Ok, we have an expansion of operand 0 into a new type. Get the
1683 // constant value, masink off bits which are not set in the RHS. These
1684 // could be set if the destination value is signed.
1685 uint64_t ConstVal = ConstantRHS->getRawValue();
1686 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1688 // If the constant we are comparing it with has high bits set, which
1689 // don't exist in the original value, the values could never be equal,
1690 // because the source would be zero extended.
1692 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1693 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1694 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1695 switch (I.getOpcode()) {
1696 default: assert(0 && "Unknown comparison type!");
1697 case Instruction::SetEQ:
1698 return ReplaceInstUsesWith(I, ConstantBool::False);
1699 case Instruction::SetNE:
1700 return ReplaceInstUsesWith(I, ConstantBool::True);
1701 case Instruction::SetLT:
1702 case Instruction::SetLE:
1703 if (DestTy->isSigned() && HasSignBit)
1704 return ReplaceInstUsesWith(I, ConstantBool::False);
1705 return ReplaceInstUsesWith(I, ConstantBool::True);
1706 case Instruction::SetGT:
1707 case Instruction::SetGE:
1708 if (DestTy->isSigned() && HasSignBit)
1709 return ReplaceInstUsesWith(I, ConstantBool::True);
1710 return ReplaceInstUsesWith(I, ConstantBool::False);
1714 // Otherwise, we can replace the setcc with a setcc of the smaller
1716 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1717 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1721 return Changed ? &I : 0;
1726 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1727 assert(I.getOperand(1)->getType() == Type::UByteTy);
1728 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1729 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1731 // shl X, 0 == X and shr X, 0 == X
1732 // shl 0, X == 0 and shr 0, X == 0
1733 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1734 Op0 == Constant::getNullValue(Op0->getType()))
1735 return ReplaceInstUsesWith(I, Op0);
1737 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1739 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1740 if (CSI->isAllOnesValue())
1741 return ReplaceInstUsesWith(I, CSI);
1743 // Try to fold constant and into select arguments.
1744 if (isa<Constant>(Op0))
1745 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1746 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1749 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1750 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1751 // of a signed value.
1753 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1754 if (CUI->getValue() >= TypeBits) {
1755 if (!Op0->getType()->isSigned() || isLeftShift)
1756 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1758 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1763 // ((X*C1) << C2) == (X * (C1 << C2))
1764 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1765 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1766 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1767 return BinaryOperator::create(Instruction::Mul, BO->getOperand(0),
1768 ConstantExpr::get(Instruction::Shl, BOOp, CUI));
1770 // Try to fold constant and into select arguments.
1771 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1772 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1775 // If the operand is an bitwise operator with a constant RHS, and the
1776 // shift is the only use, we can pull it out of the shift.
1777 if (Op0->hasOneUse())
1778 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1779 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1780 bool isValid = true; // Valid only for And, Or, Xor
1781 bool highBitSet = false; // Transform if high bit of constant set?
1783 switch (Op0BO->getOpcode()) {
1784 default: isValid = false; break; // Do not perform transform!
1785 case Instruction::Or:
1786 case Instruction::Xor:
1789 case Instruction::And:
1794 // If this is a signed shift right, and the high bit is modified
1795 // by the logical operation, do not perform the transformation.
1796 // The highBitSet boolean indicates the value of the high bit of
1797 // the constant which would cause it to be modified for this
1800 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1801 uint64_t Val = Op0C->getRawValue();
1802 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1806 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1808 Instruction *NewShift =
1809 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1812 InsertNewInstBefore(NewShift, I);
1814 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1819 // If this is a shift of a shift, see if we can fold the two together...
1820 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1821 if (ConstantUInt *ShiftAmt1C =
1822 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1823 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1824 unsigned ShiftAmt2 = CUI->getValue();
1826 // Check for (A << c1) << c2 and (A >> c1) >> c2
1827 if (I.getOpcode() == Op0SI->getOpcode()) {
1828 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1829 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1830 Amt = Op0->getType()->getPrimitiveSize()*8;
1831 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1832 ConstantUInt::get(Type::UByteTy, Amt));
1835 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1836 // signed types, we can only support the (A >> c1) << c2 configuration,
1837 // because it can not turn an arbitrary bit of A into a sign bit.
1838 if (I.getType()->isUnsigned() || isLeftShift) {
1839 // Calculate bitmask for what gets shifted off the edge...
1840 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1842 C = ConstantExpr::get(Instruction::Shl, C, ShiftAmt1C);
1844 C = ConstantExpr::get(Instruction::Shr, C, ShiftAmt1C);
1847 BinaryOperator::create(Instruction::And, Op0SI->getOperand(0),
1848 C, Op0SI->getOperand(0)->getName()+".mask");
1849 InsertNewInstBefore(Mask, I);
1851 // Figure out what flavor of shift we should use...
1852 if (ShiftAmt1 == ShiftAmt2)
1853 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1854 else if (ShiftAmt1 < ShiftAmt2) {
1855 return new ShiftInst(I.getOpcode(), Mask,
1856 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1858 return new ShiftInst(Op0SI->getOpcode(), Mask,
1859 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1869 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1872 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1873 const Type *DstTy) {
1875 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1876 // are identical and the bits don't get reinterpreted (for example
1877 // int->float->int would not be allowed)
1878 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1881 // Allow free casting and conversion of sizes as long as the sign doesn't
1883 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1884 unsigned SrcSize = SrcTy->getPrimitiveSize();
1885 unsigned MidSize = MidTy->getPrimitiveSize();
1886 unsigned DstSize = DstTy->getPrimitiveSize();
1888 // Cases where we are monotonically decreasing the size of the type are
1889 // always ok, regardless of what sign changes are going on.
1891 if (SrcSize >= MidSize && MidSize >= DstSize)
1894 // Cases where the source and destination type are the same, but the middle
1895 // type is bigger are noops.
1897 if (SrcSize == DstSize && MidSize > SrcSize)
1900 // If we are monotonically growing, things are more complex.
1902 if (SrcSize <= MidSize && MidSize <= DstSize) {
1903 // We have eight combinations of signedness to worry about. Here's the
1905 static const int SignTable[8] = {
1906 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1907 1, // U U U Always ok
1908 1, // U U S Always ok
1909 3, // U S U Ok iff SrcSize != MidSize
1910 3, // U S S Ok iff SrcSize != MidSize
1911 0, // S U U Never ok
1912 2, // S U S Ok iff MidSize == DstSize
1913 1, // S S U Always ok
1914 1, // S S S Always ok
1917 // Choose an action based on the current entry of the signtable that this
1918 // cast of cast refers to...
1919 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1920 switch (SignTable[Row]) {
1921 case 0: return false; // Never ok
1922 case 1: return true; // Always ok
1923 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1924 case 3: // Ok iff SrcSize != MidSize
1925 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1926 default: assert(0 && "Bad entry in sign table!");
1931 // Otherwise, we cannot succeed. Specifically we do not want to allow things
1932 // like: short -> ushort -> uint, because this can create wrong results if
1933 // the input short is negative!
1938 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
1939 if (V->getType() == Ty || isa<Constant>(V)) return false;
1940 if (const CastInst *CI = dyn_cast<CastInst>(V))
1941 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
1946 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
1947 /// InsertBefore instruction. This is specialized a bit to avoid inserting
1948 /// casts that are known to not do anything...
1950 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
1951 Instruction *InsertBefore) {
1952 if (V->getType() == DestTy) return V;
1953 if (Constant *C = dyn_cast<Constant>(V))
1954 return ConstantExpr::getCast(C, DestTy);
1956 CastInst *CI = new CastInst(V, DestTy, V->getName());
1957 InsertNewInstBefore(CI, *InsertBefore);
1961 // CastInst simplification
1963 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
1964 Value *Src = CI.getOperand(0);
1966 // If the user is casting a value to the same type, eliminate this cast
1968 if (CI.getType() == Src->getType())
1969 return ReplaceInstUsesWith(CI, Src);
1971 // If casting the result of another cast instruction, try to eliminate this
1974 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
1975 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
1976 CSrc->getType(), CI.getType())) {
1977 // This instruction now refers directly to the cast's src operand. This
1978 // has a good chance of making CSrc dead.
1979 CI.setOperand(0, CSrc->getOperand(0));
1983 // If this is an A->B->A cast, and we are dealing with integral types, try
1984 // to convert this into a logical 'and' instruction.
1986 if (CSrc->getOperand(0)->getType() == CI.getType() &&
1987 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
1988 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
1989 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
1990 assert(CSrc->getType() != Type::ULongTy &&
1991 "Cannot have type bigger than ulong!");
1992 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
1993 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
1994 return BinaryOperator::create(Instruction::And, CSrc->getOperand(0),
1999 // If casting the result of a getelementptr instruction with no offset, turn
2000 // this into a cast of the original pointer!
2002 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
2003 bool AllZeroOperands = true;
2004 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2005 if (!isa<Constant>(GEP->getOperand(i)) ||
2006 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
2007 AllZeroOperands = false;
2010 if (AllZeroOperands) {
2011 CI.setOperand(0, GEP->getOperand(0));
2016 // If we are casting a malloc or alloca to a pointer to a type of the same
2017 // size, rewrite the allocation instruction to allocate the "right" type.
2019 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
2020 if (AI->hasOneUse() && !AI->isArrayAllocation())
2021 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
2022 // Get the type really allocated and the type casted to...
2023 const Type *AllocElTy = AI->getAllocatedType();
2024 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
2025 const Type *CastElTy = PTy->getElementType();
2026 unsigned CastElTySize = TD->getTypeSize(CastElTy);
2028 // If the allocation is for an even multiple of the cast type size
2029 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
2030 Value *Amt = ConstantUInt::get(Type::UIntTy,
2031 AllocElTySize/CastElTySize);
2032 std::string Name = AI->getName(); AI->setName("");
2033 AllocationInst *New;
2034 if (isa<MallocInst>(AI))
2035 New = new MallocInst(CastElTy, Amt, Name);
2037 New = new AllocaInst(CastElTy, Amt, Name);
2038 InsertNewInstBefore(New, CI);
2039 return ReplaceInstUsesWith(CI, New);
2043 // If the source value is an instruction with only this use, we can attempt to
2044 // propagate the cast into the instruction. Also, only handle integral types
2046 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
2047 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
2048 CI.getType()->isInteger()) { // Don't mess with casts to bool here
2049 const Type *DestTy = CI.getType();
2050 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
2051 unsigned DestBitSize = getTypeSizeInBits(DestTy);
2053 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
2054 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
2056 switch (SrcI->getOpcode()) {
2057 case Instruction::Add:
2058 case Instruction::Mul:
2059 case Instruction::And:
2060 case Instruction::Or:
2061 case Instruction::Xor:
2062 // If we are discarding information, or just changing the sign, rewrite.
2063 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
2064 // Don't insert two casts if they cannot be eliminated. We allow two
2065 // casts to be inserted if the sizes are the same. This could only be
2066 // converting signedness, which is a noop.
2067 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
2068 !ValueRequiresCast(Op0, DestTy)) {
2069 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2070 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
2071 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
2072 ->getOpcode(), Op0c, Op1c);
2076 case Instruction::Shl:
2077 // Allow changing the sign of the source operand. Do not allow changing
2078 // the size of the shift, UNLESS the shift amount is a constant. We
2079 // mush not change variable sized shifts to a smaller size, because it
2080 // is undefined to shift more bits out than exist in the value.
2081 if (DestBitSize == SrcBitSize ||
2082 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2083 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2084 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2093 /// GetSelectFoldableOperands - We want to turn code that looks like this:
2095 /// %D = select %cond, %C, %A
2097 /// %C = select %cond, %B, 0
2100 /// Assuming that the specified instruction is an operand to the select, return
2101 /// a bitmask indicating which operands of this instruction are foldable if they
2102 /// equal the other incoming value of the select.
2104 static unsigned GetSelectFoldableOperands(Instruction *I) {
2105 switch (I->getOpcode()) {
2106 case Instruction::Add:
2107 case Instruction::Mul:
2108 case Instruction::And:
2109 case Instruction::Or:
2110 case Instruction::Xor:
2111 return 3; // Can fold through either operand.
2112 case Instruction::Sub: // Can only fold on the amount subtracted.
2113 case Instruction::Shl: // Can only fold on the shift amount.
2114 case Instruction::Shr:
2117 return 0; // Cannot fold
2121 /// GetSelectFoldableConstant - For the same transformation as the previous
2122 /// function, return the identity constant that goes into the select.
2123 static Constant *GetSelectFoldableConstant(Instruction *I) {
2124 switch (I->getOpcode()) {
2125 default: assert(0 && "This cannot happen!"); abort();
2126 case Instruction::Add:
2127 case Instruction::Sub:
2128 case Instruction::Or:
2129 case Instruction::Xor:
2130 return Constant::getNullValue(I->getType());
2131 case Instruction::Shl:
2132 case Instruction::Shr:
2133 return Constant::getNullValue(Type::UByteTy);
2134 case Instruction::And:
2135 return ConstantInt::getAllOnesValue(I->getType());
2136 case Instruction::Mul:
2137 return ConstantInt::get(I->getType(), 1);
2141 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
2142 Value *CondVal = SI.getCondition();
2143 Value *TrueVal = SI.getTrueValue();
2144 Value *FalseVal = SI.getFalseValue();
2146 // select true, X, Y -> X
2147 // select false, X, Y -> Y
2148 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
2149 if (C == ConstantBool::True)
2150 return ReplaceInstUsesWith(SI, TrueVal);
2152 assert(C == ConstantBool::False);
2153 return ReplaceInstUsesWith(SI, FalseVal);
2156 // select C, X, X -> X
2157 if (TrueVal == FalseVal)
2158 return ReplaceInstUsesWith(SI, TrueVal);
2160 if (SI.getType() == Type::BoolTy)
2161 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
2162 if (C == ConstantBool::True) {
2163 // Change: A = select B, true, C --> A = or B, C
2164 return BinaryOperator::create(Instruction::Or, CondVal, FalseVal);
2166 // Change: A = select B, false, C --> A = and !B, C
2168 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2169 "not."+CondVal->getName()), SI);
2170 return BinaryOperator::create(Instruction::And, NotCond, FalseVal);
2172 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
2173 if (C == ConstantBool::False) {
2174 // Change: A = select B, C, false --> A = and B, C
2175 return BinaryOperator::create(Instruction::And, CondVal, TrueVal);
2177 // Change: A = select B, C, true --> A = or !B, C
2179 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2180 "not."+CondVal->getName()), SI);
2181 return BinaryOperator::create(Instruction::Or, NotCond, TrueVal);
2185 // Selecting between two integer constants?
2186 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
2187 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
2188 // select C, 1, 0 -> cast C to int
2189 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
2190 return new CastInst(CondVal, SI.getType());
2191 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
2192 // select C, 0, 1 -> cast !C to int
2194 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2195 "not."+CondVal->getName()), SI);
2196 return new CastInst(NotCond, SI.getType());
2200 // See if we are selecting two values based on a comparison of the two values.
2201 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
2202 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
2203 // Transform (X == Y) ? X : Y -> Y
2204 if (SCI->getOpcode() == Instruction::SetEQ)
2205 return ReplaceInstUsesWith(SI, FalseVal);
2206 // Transform (X != Y) ? X : Y -> X
2207 if (SCI->getOpcode() == Instruction::SetNE)
2208 return ReplaceInstUsesWith(SI, TrueVal);
2209 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2211 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
2212 // Transform (X == Y) ? Y : X -> X
2213 if (SCI->getOpcode() == Instruction::SetEQ)
2214 return ReplaceInstUsesWith(SI, FalseVal);
2215 // Transform (X != Y) ? Y : X -> Y
2216 if (SCI->getOpcode() == Instruction::SetNE)
2217 return ReplaceInstUsesWith(SI, TrueVal);
2218 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2222 // See if we can fold the select into one of our operands.
2223 if (SI.getType()->isInteger()) {
2224 // See the comment above GetSelectFoldableOperands for a description of the
2225 // transformation we are doing here.
2226 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
2227 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
2228 !isa<Constant>(FalseVal))
2229 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
2230 unsigned OpToFold = 0;
2231 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
2233 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
2238 Constant *C = GetSelectFoldableConstant(TVI);
2239 std::string Name = TVI->getName(); TVI->setName("");
2240 Instruction *NewSel =
2241 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
2243 InsertNewInstBefore(NewSel, SI);
2244 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
2245 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
2246 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
2247 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
2249 assert(0 && "Unknown instruction!!");
2254 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
2255 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
2256 !isa<Constant>(TrueVal))
2257 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
2258 unsigned OpToFold = 0;
2259 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
2261 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
2266 Constant *C = GetSelectFoldableConstant(FVI);
2267 std::string Name = FVI->getName(); FVI->setName("");
2268 Instruction *NewSel =
2269 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
2271 InsertNewInstBefore(NewSel, SI);
2272 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
2273 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
2274 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
2275 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
2277 assert(0 && "Unknown instruction!!");
2286 // CallInst simplification
2288 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2289 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2291 if (Function *F = CI.getCalledFunction())
2292 switch (F->getIntrinsicID()) {
2293 case Intrinsic::memmove:
2294 case Intrinsic::memcpy:
2295 case Intrinsic::memset:
2296 // memmove/cpy/set of zero bytes is a noop.
2297 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2298 if (NumBytes->isNullValue())
2299 return EraseInstFromFunction(CI);
2306 return visitCallSite(&CI);
2309 // InvokeInst simplification
2311 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2312 return visitCallSite(&II);
2315 // visitCallSite - Improvements for call and invoke instructions.
2317 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2318 bool Changed = false;
2320 // If the callee is a constexpr cast of a function, attempt to move the cast
2321 // to the arguments of the call/invoke.
2322 if (transformConstExprCastCall(CS)) return 0;
2324 Value *Callee = CS.getCalledValue();
2325 const PointerType *PTy = cast<PointerType>(Callee->getType());
2326 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2327 if (FTy->isVarArg()) {
2328 // See if we can optimize any arguments passed through the varargs area of
2330 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2331 E = CS.arg_end(); I != E; ++I)
2332 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2333 // If this cast does not effect the value passed through the varargs
2334 // area, we can eliminate the use of the cast.
2335 Value *Op = CI->getOperand(0);
2336 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2343 return Changed ? CS.getInstruction() : 0;
2346 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2347 // attempt to move the cast to the arguments of the call/invoke.
2349 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2350 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2351 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2352 if (CE->getOpcode() != Instruction::Cast ||
2353 !isa<ConstantPointerRef>(CE->getOperand(0)))
2355 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2356 if (!isa<Function>(CPR->getValue())) return false;
2357 Function *Callee = cast<Function>(CPR->getValue());
2358 Instruction *Caller = CS.getInstruction();
2360 // Okay, this is a cast from a function to a different type. Unless doing so
2361 // would cause a type conversion of one of our arguments, change this call to
2362 // be a direct call with arguments casted to the appropriate types.
2364 const FunctionType *FT = Callee->getFunctionType();
2365 const Type *OldRetTy = Caller->getType();
2367 // Check to see if we are changing the return type...
2368 if (OldRetTy != FT->getReturnType()) {
2369 if (Callee->isExternal() &&
2370 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2371 !Caller->use_empty())
2372 return false; // Cannot transform this return value...
2374 // If the callsite is an invoke instruction, and the return value is used by
2375 // a PHI node in a successor, we cannot change the return type of the call
2376 // because there is no place to put the cast instruction (without breaking
2377 // the critical edge). Bail out in this case.
2378 if (!Caller->use_empty())
2379 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2380 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2382 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2383 if (PN->getParent() == II->getNormalDest() ||
2384 PN->getParent() == II->getUnwindDest())
2388 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2389 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2391 CallSite::arg_iterator AI = CS.arg_begin();
2392 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2393 const Type *ParamTy = FT->getParamType(i);
2394 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2395 if (Callee->isExternal() && !isConvertible) return false;
2398 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2399 Callee->isExternal())
2400 return false; // Do not delete arguments unless we have a function body...
2402 // Okay, we decided that this is a safe thing to do: go ahead and start
2403 // inserting cast instructions as necessary...
2404 std::vector<Value*> Args;
2405 Args.reserve(NumActualArgs);
2407 AI = CS.arg_begin();
2408 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2409 const Type *ParamTy = FT->getParamType(i);
2410 if ((*AI)->getType() == ParamTy) {
2411 Args.push_back(*AI);
2413 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
2418 // If the function takes more arguments than the call was taking, add them
2420 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2421 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2423 // If we are removing arguments to the function, emit an obnoxious warning...
2424 if (FT->getNumParams() < NumActualArgs)
2425 if (!FT->isVarArg()) {
2426 std::cerr << "WARNING: While resolving call to function '"
2427 << Callee->getName() << "' arguments were dropped!\n";
2429 // Add all of the arguments in their promoted form to the arg list...
2430 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2431 const Type *PTy = getPromotedType((*AI)->getType());
2432 if (PTy != (*AI)->getType()) {
2433 // Must promote to pass through va_arg area!
2434 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2435 InsertNewInstBefore(Cast, *Caller);
2436 Args.push_back(Cast);
2438 Args.push_back(*AI);
2443 if (FT->getReturnType() == Type::VoidTy)
2444 Caller->setName(""); // Void type should not have a name...
2447 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2448 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2449 Args, Caller->getName(), Caller);
2451 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2454 // Insert a cast of the return type as necessary...
2456 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2457 if (NV->getType() != Type::VoidTy) {
2458 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2460 // If this is an invoke instruction, we should insert it after the first
2461 // non-phi, instruction in the normal successor block.
2462 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2463 BasicBlock::iterator I = II->getNormalDest()->begin();
2464 while (isa<PHINode>(I)) ++I;
2465 InsertNewInstBefore(NC, *I);
2467 // Otherwise, it's a call, just insert cast right after the call instr
2468 InsertNewInstBefore(NC, *Caller);
2470 AddUsersToWorkList(*Caller);
2472 NV = Constant::getNullValue(Caller->getType());
2476 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2477 Caller->replaceAllUsesWith(NV);
2478 Caller->getParent()->getInstList().erase(Caller);
2479 removeFromWorkList(Caller);
2485 // PHINode simplification
2487 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2488 if (Value *V = hasConstantValue(&PN))
2489 return ReplaceInstUsesWith(PN, V);
2491 // If the only user of this instruction is a cast instruction, and all of the
2492 // incoming values are constants, change this PHI to merge together the casted
2495 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2496 if (CI->getType() != PN.getType()) { // noop casts will be folded
2497 bool AllConstant = true;
2498 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2499 if (!isa<Constant>(PN.getIncomingValue(i))) {
2500 AllConstant = false;
2504 // Make a new PHI with all casted values.
2505 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2506 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2507 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2508 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2509 PN.getIncomingBlock(i));
2512 // Update the cast instruction.
2513 CI->setOperand(0, New);
2514 WorkList.push_back(CI); // revisit the cast instruction to fold.
2515 WorkList.push_back(New); // Make sure to revisit the new Phi
2516 return &PN; // PN is now dead!
2522 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
2523 Instruction *InsertPoint,
2525 unsigned PS = IC->getTargetData().getPointerSize();
2526 const Type *VTy = V->getType();
2528 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
2529 // We must insert a cast to ensure we sign-extend.
2530 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
2531 V->getName()), *InsertPoint);
2532 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
2537 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2538 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2539 // If so, eliminate the noop.
2540 if (GEP.getNumOperands() == 1)
2541 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2543 bool HasZeroPointerIndex = false;
2544 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2545 HasZeroPointerIndex = C->isNullValue();
2547 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2548 return ReplaceInstUsesWith(GEP, GEP.getOperand(0));
2550 // Eliminate unneeded casts for indices.
2551 bool MadeChange = false;
2552 gep_type_iterator GTI = gep_type_begin(GEP);
2553 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
2554 if (isa<SequentialType>(*GTI)) {
2555 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
2556 Value *Src = CI->getOperand(0);
2557 const Type *SrcTy = Src->getType();
2558 const Type *DestTy = CI->getType();
2559 if (Src->getType()->isInteger()) {
2560 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
2561 // We can always eliminate a cast from ulong or long to the other.
2562 // We can always eliminate a cast from uint to int or the other on
2563 // 32-bit pointer platforms.
2564 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
2566 GEP.setOperand(i, Src);
2568 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2569 SrcTy->getPrimitiveSize() == 4) {
2570 // We can always eliminate a cast from int to [u]long. We can
2571 // eliminate a cast from uint to [u]long iff the target is a 32-bit
2573 if (SrcTy->isSigned() ||
2574 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
2576 GEP.setOperand(i, Src);
2581 // If we are using a wider index than needed for this platform, shrink it
2582 // to what we need. If the incoming value needs a cast instruction,
2583 // insert it. This explicit cast can make subsequent optimizations more
2585 Value *Op = GEP.getOperand(i);
2586 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
2587 if (Constant *C = dyn_cast<Constant>(Op)) {
2588 GEP.setOperand(i, ConstantExpr::getCast(C, TD->getIntPtrType()));
2591 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
2592 Op->getName()), GEP);
2593 GEP.setOperand(i, Op);
2597 if (MadeChange) return &GEP;
2599 // Combine Indices - If the source pointer to this getelementptr instruction
2600 // is a getelementptr instruction, combine the indices of the two
2601 // getelementptr instructions into a single instruction.
2603 std::vector<Value*> SrcGEPOperands;
2604 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
2605 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2606 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2607 if (CE->getOpcode() == Instruction::GetElementPtr)
2608 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2611 if (!SrcGEPOperands.empty()) {
2612 std::vector<Value *> Indices;
2614 // Can we combine the two pointer arithmetics offsets?
2615 if (SrcGEPOperands.size() == 2 && isa<Constant>(SrcGEPOperands[1]) &&
2616 isa<Constant>(GEP.getOperand(1))) {
2617 Constant *SGC = cast<Constant>(SrcGEPOperands[1]);
2618 Constant *GC = cast<Constant>(GEP.getOperand(1));
2619 if (SGC->getType() != GC->getType()) {
2620 SGC = ConstantExpr::getSignExtend(SGC, Type::LongTy);
2621 GC = ConstantExpr::getSignExtend(GC, Type::LongTy);
2624 // Replace: gep (gep %P, long C1), long C2, ...
2625 // With: gep %P, long (C1+C2), ...
2626 GEP.setOperand(0, SrcGEPOperands[0]);
2627 GEP.setOperand(1, ConstantExpr::getAdd(SGC, GC));
2628 if (Instruction *I = dyn_cast<Instruction>(GEP.getOperand(0)))
2629 AddUsersToWorkList(*I); // Reduce use count of Src
2631 } else if (SrcGEPOperands.size() == 2) {
2632 // Replace: gep (gep %P, long B), long A, ...
2633 // With: T = long A+B; gep %P, T, ...
2635 // Note that if our source is a gep chain itself that we wait for that
2636 // chain to be resolved before we perform this transformation. This
2637 // avoids us creating a TON of code in some cases.
2639 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2640 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2641 return 0; // Wait until our source is folded to completion.
2643 Value *Sum, *SO1 = SrcGEPOperands[1], *GO1 = GEP.getOperand(1);
2644 if (SO1 == Constant::getNullValue(SO1->getType())) {
2646 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
2649 // If they aren't the same type, convert both to an integer of the
2650 // target's pointer size.
2651 if (SO1->getType() != GO1->getType()) {
2652 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
2653 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
2654 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
2655 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
2657 unsigned PS = TD->getPointerSize();
2659 if (SO1->getType()->getPrimitiveSize() == PS) {
2660 // Convert GO1 to SO1's type.
2661 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
2663 } else if (GO1->getType()->getPrimitiveSize() == PS) {
2664 // Convert SO1 to GO1's type.
2665 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
2667 const Type *PT = TD->getIntPtrType();
2668 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
2669 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
2673 Sum = BinaryOperator::create(Instruction::Add, SO1, GO1,
2674 GEP.getOperand(0)->getName()+".sum", &GEP);
2675 WorkList.push_back(cast<Instruction>(Sum));
2677 GEP.setOperand(0, SrcGEPOperands[0]);
2678 GEP.setOperand(1, Sum);
2680 } else if (isa<Constant>(*GEP.idx_begin()) &&
2681 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
2682 SrcGEPOperands.size() != 1) {
2683 // Otherwise we can do the fold if the first index of the GEP is a zero
2684 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2685 SrcGEPOperands.end());
2686 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2687 } else if (SrcGEPOperands.back() ==
2688 Constant::getNullValue(SrcGEPOperands.back()->getType())) {
2689 // We have to check to make sure this really is an ARRAY index we are
2690 // ending up with, not a struct index.
2691 generic_gep_type_iterator<std::vector<Value*>::iterator>
2692 GTI = gep_type_begin(SrcGEPOperands[0]->getType(),
2693 SrcGEPOperands.begin()+1, SrcGEPOperands.end());
2694 std::advance(GTI, SrcGEPOperands.size()-2);
2695 if (isa<SequentialType>(*GTI)) {
2696 // If the src gep ends with a constant array index, merge this get into
2697 // it, even if we have a non-zero array index.
2698 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2699 SrcGEPOperands.end()-1);
2700 Indices.insert(Indices.end(), GEP.idx_begin(), GEP.idx_end());
2704 if (!Indices.empty())
2705 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2707 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
2708 // GEP of global variable. If all of the indices for this GEP are
2709 // constants, we can promote this to a constexpr instead of an instruction.
2711 // Scan for nonconstants...
2712 std::vector<Constant*> Indices;
2713 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2714 for (; I != E && isa<Constant>(*I); ++I)
2715 Indices.push_back(cast<Constant>(*I));
2717 if (I == E) { // If they are all constants...
2719 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2721 // Replace all uses of the GEP with the new constexpr...
2722 return ReplaceInstUsesWith(GEP, CE);
2724 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP.getOperand(0))) {
2725 if (CE->getOpcode() == Instruction::Cast) {
2726 if (HasZeroPointerIndex) {
2727 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2728 // into : GEP [10 x ubyte]* X, long 0, ...
2730 // This occurs when the program declares an array extern like "int X[];"
2732 Constant *X = CE->getOperand(0);
2733 const PointerType *CPTy = cast<PointerType>(CE->getType());
2734 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2735 if (const ArrayType *XATy =
2736 dyn_cast<ArrayType>(XTy->getElementType()))
2737 if (const ArrayType *CATy =
2738 dyn_cast<ArrayType>(CPTy->getElementType()))
2739 if (CATy->getElementType() == XATy->getElementType()) {
2740 // At this point, we know that the cast source type is a pointer
2741 // to an array of the same type as the destination pointer
2742 // array. Because the array type is never stepped over (there
2743 // is a leading zero) we can fold the cast into this GEP.
2744 GEP.setOperand(0, X);
2754 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2755 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2756 if (AI.isArrayAllocation()) // Check C != 1
2757 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2758 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2759 AllocationInst *New = 0;
2761 // Create and insert the replacement instruction...
2762 if (isa<MallocInst>(AI))
2763 New = new MallocInst(NewTy, 0, AI.getName());
2765 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2766 New = new AllocaInst(NewTy, 0, AI.getName());
2769 InsertNewInstBefore(New, AI);
2771 // Scan to the end of the allocation instructions, to skip over a block of
2772 // allocas if possible...
2774 BasicBlock::iterator It = New;
2775 while (isa<AllocationInst>(*It)) ++It;
2777 // Now that I is pointing to the first non-allocation-inst in the block,
2778 // insert our getelementptr instruction...
2780 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
2781 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2783 // Now make everything use the getelementptr instead of the original
2785 return ReplaceInstUsesWith(AI, V);
2788 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2789 // Note that we only do this for alloca's, because malloc should allocate and
2790 // return a unique pointer, even for a zero byte allocation.
2791 if (isa<AllocaInst>(AI) && TD->getTypeSize(AI.getAllocatedType()) == 0)
2792 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2797 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2798 Value *Op = FI.getOperand(0);
2800 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2801 if (CastInst *CI = dyn_cast<CastInst>(Op))
2802 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2803 FI.setOperand(0, CI->getOperand(0));
2807 // If we have 'free null' delete the instruction. This can happen in stl code
2808 // when lots of inlining happens.
2809 if (isa<ConstantPointerNull>(Op))
2810 return EraseInstFromFunction(FI);
2816 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2817 /// constantexpr, return the constant value being addressed by the constant
2818 /// expression, or null if something is funny.
2820 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2821 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
2822 return 0; // Do not allow stepping over the value!
2824 // Loop over all of the operands, tracking down which value we are
2826 for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
2827 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
2828 ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
2829 if (CS == 0) return 0;
2830 if (CU->getValue() >= CS->getValues().size()) return 0;
2831 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2832 } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
2833 ConstantArray *CA = dyn_cast<ConstantArray>(C);
2834 if (CA == 0) return 0;
2835 if ((uint64_t)CS->getValue() >= CA->getValues().size()) return 0;
2836 C = cast<Constant>(CA->getValues()[CS->getValue()]);
2842 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2843 Value *Op = LI.getOperand(0);
2844 if (LI.isVolatile()) return 0;
2846 if (Constant *C = dyn_cast<Constant>(Op))
2847 if (C->isNullValue()) // load null -> 0
2848 return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
2849 else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
2850 Op = CPR->getValue();
2852 // Instcombine load (constant global) into the value loaded...
2853 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2854 if (GV->isConstant() && !GV->isExternal())
2855 return ReplaceInstUsesWith(LI, GV->getInitializer());
2857 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2858 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2859 if (CE->getOpcode() == Instruction::GetElementPtr)
2860 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2861 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2862 if (GV->isConstant() && !GV->isExternal())
2863 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2864 return ReplaceInstUsesWith(LI, V);
2866 // load (cast X) --> cast (load X) iff safe
2867 if (CastInst *CI = dyn_cast<CastInst>(Op)) {
2868 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
2869 if (const PointerType *SrcTy =
2870 dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
2871 const Type *SrcPTy = SrcTy->getElementType();
2872 if (TD->getTypeSize(SrcPTy) == TD->getTypeSize(DestPTy) &&
2873 (SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
2874 (DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
2875 // Okay, we are casting from one integer or pointer type to another of
2876 // the same size. Instead of casting the pointer before the load, cast
2877 // the result of the loaded value.
2878 Value *NewLoad = InsertNewInstBefore(new LoadInst(CI->getOperand(0),
2879 CI->getName()), LI);
2880 // Now cast the result of the load.
2881 return new CastInst(NewLoad, LI.getType());
2890 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2891 // Change br (not X), label True, label False to: br X, label False, True
2892 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
2893 if (Value *V = dyn_castNotVal(BI.getCondition())) {
2894 BasicBlock *TrueDest = BI.getSuccessor(0);
2895 BasicBlock *FalseDest = BI.getSuccessor(1);
2896 // Swap Destinations and condition...
2898 BI.setSuccessor(0, FalseDest);
2899 BI.setSuccessor(1, TrueDest);
2901 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
2902 // Cannonicalize setne -> seteq
2903 if ((I->getOpcode() == Instruction::SetNE ||
2904 I->getOpcode() == Instruction::SetLE ||
2905 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
2906 std::string Name = I->getName(); I->setName("");
2907 Instruction::BinaryOps NewOpcode =
2908 SetCondInst::getInverseCondition(I->getOpcode());
2909 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
2910 I->getOperand(1), Name, I);
2911 BasicBlock *TrueDest = BI.getSuccessor(0);
2912 BasicBlock *FalseDest = BI.getSuccessor(1);
2913 // Swap Destinations and condition...
2914 BI.setCondition(NewSCC);
2915 BI.setSuccessor(0, FalseDest);
2916 BI.setSuccessor(1, TrueDest);
2917 removeFromWorkList(I);
2918 I->getParent()->getInstList().erase(I);
2919 WorkList.push_back(cast<Instruction>(NewSCC));
2928 void InstCombiner::removeFromWorkList(Instruction *I) {
2929 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
2933 bool InstCombiner::runOnFunction(Function &F) {
2934 bool Changed = false;
2935 TD = &getAnalysis<TargetData>();
2937 WorkList.insert(WorkList.end(), inst_begin(F), inst_end(F));
2939 while (!WorkList.empty()) {
2940 Instruction *I = WorkList.back(); // Get an instruction from the worklist
2941 WorkList.pop_back();
2943 // Check to see if we can DCE or ConstantPropagate the instruction...
2944 // Check to see if we can DIE the instruction...
2945 if (isInstructionTriviallyDead(I)) {
2946 // Add operands to the worklist...
2947 if (I->getNumOperands() < 4)
2948 AddUsesToWorkList(*I);
2951 I->getParent()->getInstList().erase(I);
2952 removeFromWorkList(I);
2956 // Instruction isn't dead, see if we can constant propagate it...
2957 if (Constant *C = ConstantFoldInstruction(I)) {
2958 // Add operands to the worklist...
2959 AddUsesToWorkList(*I);
2960 ReplaceInstUsesWith(*I, C);
2963 I->getParent()->getInstList().erase(I);
2964 removeFromWorkList(I);
2968 // Check to see if any of the operands of this instruction are a
2969 // ConstantPointerRef. Since they sneak in all over the place and inhibit
2970 // optimization, we want to strip them out unconditionally!
2971 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
2972 if (ConstantPointerRef *CPR =
2973 dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
2974 I->setOperand(i, CPR->getValue());
2978 // Now that we have an instruction, try combining it to simplify it...
2979 if (Instruction *Result = visit(*I)) {
2981 // Should we replace the old instruction with a new one?
2983 DEBUG(std::cerr << "IC: Old = " << *I
2984 << " New = " << *Result);
2986 // Instructions can end up on the worklist more than once. Make sure
2987 // we do not process an instruction that has been deleted.
2988 removeFromWorkList(I);
2990 // Move the name to the new instruction first...
2991 std::string OldName = I->getName(); I->setName("");
2992 Result->setName(OldName);
2994 // Insert the new instruction into the basic block...
2995 BasicBlock *InstParent = I->getParent();
2996 InstParent->getInstList().insert(I, Result);
2998 // Everything uses the new instruction now...
2999 I->replaceAllUsesWith(Result);
3001 // Erase the old instruction.
3002 InstParent->getInstList().erase(I);
3004 DEBUG(std::cerr << "IC: MOD = " << *I);
3006 BasicBlock::iterator II = I;
3008 // If the instruction was modified, it's possible that it is now dead.
3009 // if so, remove it.
3010 if (dceInstruction(II)) {
3011 // Instructions may end up in the worklist more than once. Erase them
3013 removeFromWorkList(I);
3019 WorkList.push_back(Result);
3020 AddUsersToWorkList(*Result);
3029 Pass *llvm::createInstructionCombiningPass() {
3030 return new InstCombiner();