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);
125 Instruction *visitSwitchInst(SwitchInst &SI);
127 // visitInstruction - Specify what to return for unhandled instructions...
128 Instruction *visitInstruction(Instruction &I) { return 0; }
131 Instruction *visitCallSite(CallSite CS);
132 bool transformConstExprCastCall(CallSite CS);
135 // InsertNewInstBefore - insert an instruction New before instruction Old
136 // in the program. Add the new instruction to the worklist.
138 Value *InsertNewInstBefore(Instruction *New, Instruction &Old) {
139 assert(New && New->getParent() == 0 &&
140 "New instruction already inserted into a basic block!");
141 BasicBlock *BB = Old.getParent();
142 BB->getInstList().insert(&Old, New); // Insert inst
143 WorkList.push_back(New); // Add to worklist
147 // ReplaceInstUsesWith - This method is to be used when an instruction is
148 // found to be dead, replacable with another preexisting expression. Here
149 // we add all uses of I to the worklist, replace all uses of I with the new
150 // value, then return I, so that the inst combiner will know that I was
153 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
154 AddUsersToWorkList(I); // Add all modified instrs to worklist
156 I.replaceAllUsesWith(V);
159 // If we are replacing the instruction with itself, this must be in a
160 // segment of unreachable code, so just clobber the instruction.
161 I.replaceAllUsesWith(Constant::getNullValue(I.getType()));
166 // EraseInstFromFunction - When dealing with an instruction that has side
167 // effects or produces a void value, we can't rely on DCE to delete the
168 // instruction. Instead, visit methods should return the value returned by
170 Instruction *EraseInstFromFunction(Instruction &I) {
171 assert(I.use_empty() && "Cannot erase instruction that is used!");
172 AddUsesToWorkList(I);
173 removeFromWorkList(&I);
174 I.getParent()->getInstList().erase(&I);
175 return 0; // Don't do anything with FI
180 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
181 /// InsertBefore instruction. This is specialized a bit to avoid inserting
182 /// casts that are known to not do anything...
184 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
185 Instruction *InsertBefore);
187 // SimplifyCommutative - This performs a few simplifications for commutative
189 bool SimplifyCommutative(BinaryOperator &I);
191 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
192 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
195 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
198 // getComplexity: Assign a complexity or rank value to LLVM Values...
199 // 0 -> Constant, 1 -> Other, 2 -> Argument, 2 -> Unary, 3 -> OtherInst
200 static unsigned getComplexity(Value *V) {
201 if (isa<Instruction>(V)) {
202 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
206 if (isa<Argument>(V)) return 2;
207 return isa<Constant>(V) ? 0 : 1;
210 // isOnlyUse - Return true if this instruction will be deleted if we stop using
212 static bool isOnlyUse(Value *V) {
213 return V->hasOneUse() || isa<Constant>(V);
216 // getPromotedType - Return the specified type promoted as it would be to pass
217 // though a va_arg area...
218 static const Type *getPromotedType(const Type *Ty) {
219 switch (Ty->getTypeID()) {
220 case Type::SByteTyID:
221 case Type::ShortTyID: return Type::IntTy;
222 case Type::UByteTyID:
223 case Type::UShortTyID: return Type::UIntTy;
224 case Type::FloatTyID: return Type::DoubleTy;
229 // SimplifyCommutative - This performs a few simplifications for commutative
232 // 1. Order operands such that they are listed from right (least complex) to
233 // left (most complex). This puts constants before unary operators before
236 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
237 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
239 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
240 bool Changed = false;
241 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
242 Changed = !I.swapOperands();
244 if (!I.isAssociative()) return Changed;
245 Instruction::BinaryOps Opcode = I.getOpcode();
246 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
247 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
248 if (isa<Constant>(I.getOperand(1))) {
249 Constant *Folded = ConstantExpr::get(I.getOpcode(),
250 cast<Constant>(I.getOperand(1)),
251 cast<Constant>(Op->getOperand(1)));
252 I.setOperand(0, Op->getOperand(0));
253 I.setOperand(1, Folded);
255 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
256 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
257 isOnlyUse(Op) && isOnlyUse(Op1)) {
258 Constant *C1 = cast<Constant>(Op->getOperand(1));
259 Constant *C2 = cast<Constant>(Op1->getOperand(1));
261 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
262 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
263 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
266 WorkList.push_back(New);
267 I.setOperand(0, New);
268 I.setOperand(1, Folded);
275 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
276 // if the LHS is a constant zero (which is the 'negate' form).
278 static inline Value *dyn_castNegVal(Value *V) {
279 if (BinaryOperator::isNeg(V))
280 return BinaryOperator::getNegArgument(cast<BinaryOperator>(V));
282 // Constants can be considered to be negated values if they can be folded...
283 if (Constant *C = dyn_cast<Constant>(V))
284 return ConstantExpr::getNeg(C);
288 static inline Value *dyn_castNotVal(Value *V) {
289 if (BinaryOperator::isNot(V))
290 return BinaryOperator::getNotArgument(cast<BinaryOperator>(V));
292 // Constants can be considered to be not'ed values...
293 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
294 return ConstantExpr::getNot(C);
298 // dyn_castFoldableMul - If this value is a multiply that can be folded into
299 // other computations (because it has a constant operand), return the
300 // non-constant operand of the multiply.
302 static inline Value *dyn_castFoldableMul(Value *V) {
303 if (V->hasOneUse() && V->getType()->isInteger())
304 if (Instruction *I = dyn_cast<Instruction>(V))
305 if (I->getOpcode() == Instruction::Mul)
306 if (isa<Constant>(I->getOperand(1)))
307 return I->getOperand(0);
311 // dyn_castMaskingAnd - If this value is an And instruction masking a value with
312 // a constant, return the constant being anded with.
314 template<class ValueType>
315 static inline Constant *dyn_castMaskingAnd(ValueType *V) {
316 if (Instruction *I = dyn_cast<Instruction>(V))
317 if (I->getOpcode() == Instruction::And)
318 return dyn_cast<Constant>(I->getOperand(1));
320 // If this is a constant, it acts just like we were masking with it.
321 return dyn_cast<Constant>(V);
324 // Log2 - Calculate the log base 2 for the specified value if it is exactly a
326 static unsigned Log2(uint64_t Val) {
327 assert(Val > 1 && "Values 0 and 1 should be handled elsewhere!");
330 if (Val & 1) return 0; // Multiple bits set?
338 /// AssociativeOpt - Perform an optimization on an associative operator. This
339 /// function is designed to check a chain of associative operators for a
340 /// potential to apply a certain optimization. Since the optimization may be
341 /// applicable if the expression was reassociated, this checks the chain, then
342 /// reassociates the expression as necessary to expose the optimization
343 /// opportunity. This makes use of a special Functor, which must define
344 /// 'shouldApply' and 'apply' methods.
346 template<typename Functor>
347 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
348 unsigned Opcode = Root.getOpcode();
349 Value *LHS = Root.getOperand(0);
351 // Quick check, see if the immediate LHS matches...
352 if (F.shouldApply(LHS))
353 return F.apply(Root);
355 // Otherwise, if the LHS is not of the same opcode as the root, return.
356 Instruction *LHSI = dyn_cast<Instruction>(LHS);
357 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
358 // Should we apply this transform to the RHS?
359 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
361 // If not to the RHS, check to see if we should apply to the LHS...
362 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
363 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
367 // If the functor wants to apply the optimization to the RHS of LHSI,
368 // reassociate the expression from ((? op A) op B) to (? op (A op B))
370 BasicBlock *BB = Root.getParent();
372 // Now all of the instructions are in the current basic block, go ahead
373 // and perform the reassociation.
374 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
376 // First move the selected RHS to the LHS of the root...
377 Root.setOperand(0, LHSI->getOperand(1));
379 // Make what used to be the LHS of the root be the user of the root...
380 Value *ExtraOperand = TmpLHSI->getOperand(1);
381 if (&Root == TmpLHSI) {
382 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
385 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
386 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
387 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
388 BasicBlock::iterator ARI = &Root; ++ARI;
389 BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
392 // Now propagate the ExtraOperand down the chain of instructions until we
394 while (TmpLHSI != LHSI) {
395 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
396 // Move the instruction to immediately before the chain we are
397 // constructing to avoid breaking dominance properties.
398 NextLHSI->getParent()->getInstList().remove(NextLHSI);
399 BB->getInstList().insert(ARI, NextLHSI);
402 Value *NextOp = NextLHSI->getOperand(1);
403 NextLHSI->setOperand(1, ExtraOperand);
405 ExtraOperand = NextOp;
408 // Now that the instructions are reassociated, have the functor perform
409 // the transformation...
410 return F.apply(Root);
413 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
419 // AddRHS - Implements: X + X --> X << 1
422 AddRHS(Value *rhs) : RHS(rhs) {}
423 bool shouldApply(Value *LHS) const { return LHS == RHS; }
424 Instruction *apply(BinaryOperator &Add) const {
425 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
426 ConstantInt::get(Type::UByteTy, 1));
430 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
432 struct AddMaskingAnd {
434 AddMaskingAnd(Constant *c) : C2(c) {}
435 bool shouldApply(Value *LHS) const {
436 if (Constant *C1 = dyn_castMaskingAnd(LHS))
437 return ConstantExpr::getAnd(C1, C2)->isNullValue();
440 Instruction *apply(BinaryOperator &Add) const {
441 return BinaryOperator::createOr(Add.getOperand(0), Add.getOperand(1));
445 static Value *FoldOperationIntoSelectOperand(Instruction &BI, Value *SO,
447 // Figure out if the constant is the left or the right argument.
448 bool ConstIsRHS = isa<Constant>(BI.getOperand(1));
449 Constant *ConstOperand = cast<Constant>(BI.getOperand(ConstIsRHS));
451 if (Constant *SOC = dyn_cast<Constant>(SO)) {
453 return ConstantExpr::get(BI.getOpcode(), SOC, ConstOperand);
454 return ConstantExpr::get(BI.getOpcode(), ConstOperand, SOC);
457 Value *Op0 = SO, *Op1 = ConstOperand;
461 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&BI))
462 New = BinaryOperator::create(BO->getOpcode(), Op0, Op1);
463 else if (ShiftInst *SI = dyn_cast<ShiftInst>(&BI))
464 New = new ShiftInst(SI->getOpcode(), Op0, Op1);
466 assert(0 && "Unknown binary instruction type!");
469 return IC->InsertNewInstBefore(New, BI);
472 // FoldBinOpIntoSelect - Given an instruction with a select as one operand and a
473 // constant as the other operand, try to fold the binary operator into the
475 static Instruction *FoldBinOpIntoSelect(Instruction &BI, SelectInst *SI,
477 // Don't modify shared select instructions
478 if (!SI->hasOneUse()) return 0;
479 Value *TV = SI->getOperand(1);
480 Value *FV = SI->getOperand(2);
482 if (isa<Constant>(TV) || isa<Constant>(FV)) {
483 Value *SelectTrueVal = FoldOperationIntoSelectOperand(BI, TV, IC);
484 Value *SelectFalseVal = FoldOperationIntoSelectOperand(BI, FV, IC);
486 return new SelectInst(SI->getCondition(), SelectTrueVal,
492 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
493 bool Changed = SimplifyCommutative(I);
494 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
496 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
498 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
500 return ReplaceInstUsesWith(I, LHS);
502 // X + (signbit) --> X ^ signbit
503 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
504 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
505 uint64_t Val = CI->getRawValue() & (1ULL << NumBits)-1;
506 if (Val == (1ULL << NumBits-1))
507 return BinaryOperator::createXor(LHS, RHS);
512 if (I.getType()->isInteger())
513 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
516 if (Value *V = dyn_castNegVal(LHS))
517 return BinaryOperator::createSub(RHS, V);
520 if (!isa<Constant>(RHS))
521 if (Value *V = dyn_castNegVal(RHS))
522 return BinaryOperator::createSub(LHS, V);
524 // X*C + X --> X * (C+1)
525 if (dyn_castFoldableMul(LHS) == RHS) {
527 ConstantExpr::getAdd(
528 cast<Constant>(cast<Instruction>(LHS)->getOperand(1)),
529 ConstantInt::get(I.getType(), 1));
530 return BinaryOperator::createMul(RHS, CP1);
533 // X + X*C --> X * (C+1)
534 if (dyn_castFoldableMul(RHS) == LHS) {
536 ConstantExpr::getAdd(
537 cast<Constant>(cast<Instruction>(RHS)->getOperand(1)),
538 ConstantInt::get(I.getType(), 1));
539 return BinaryOperator::createMul(LHS, CP1);
542 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
543 if (Constant *C2 = dyn_castMaskingAnd(RHS))
544 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
546 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
547 if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
548 switch (ILHS->getOpcode()) {
549 case Instruction::Xor:
550 // ~X + C --> (C-1) - X
551 if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
552 if (XorRHS->isAllOnesValue())
553 return BinaryOperator::createSub(ConstantExpr::getSub(CRHS,
554 ConstantInt::get(I.getType(), 1)),
555 ILHS->getOperand(0));
557 case Instruction::Select:
558 // Try to fold constant add into select arguments.
559 if (Instruction *R = FoldBinOpIntoSelect(I,cast<SelectInst>(ILHS),this))
567 return Changed ? &I : 0;
570 // isSignBit - Return true if the value represented by the constant only has the
571 // highest order bit set.
572 static bool isSignBit(ConstantInt *CI) {
573 unsigned NumBits = CI->getType()->getPrimitiveSize()*8;
574 return (CI->getRawValue() & ~(-1LL << NumBits)) == (1ULL << (NumBits-1));
577 static unsigned getTypeSizeInBits(const Type *Ty) {
578 return Ty == Type::BoolTy ? 1 : Ty->getPrimitiveSize()*8;
581 /// RemoveNoopCast - Strip off nonconverting casts from the value.
583 static Value *RemoveNoopCast(Value *V) {
584 if (CastInst *CI = dyn_cast<CastInst>(V)) {
585 const Type *CTy = CI->getType();
586 const Type *OpTy = CI->getOperand(0)->getType();
587 if (CTy->isInteger() && OpTy->isInteger()) {
588 if (CTy->getPrimitiveSize() == OpTy->getPrimitiveSize())
589 return RemoveNoopCast(CI->getOperand(0));
590 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
591 return RemoveNoopCast(CI->getOperand(0));
596 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
597 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
599 if (Op0 == Op1) // sub X, X -> 0
600 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
602 // If this is a 'B = x-(-A)', change to B = x+A...
603 if (Value *V = dyn_castNegVal(Op1))
604 return BinaryOperator::createAdd(Op0, V);
606 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
607 // Replace (-1 - A) with (~A)...
608 if (C->isAllOnesValue())
609 return BinaryOperator::createNot(Op1);
611 // C - ~X == X + (1+C)
612 if (BinaryOperator::isNot(Op1))
613 return BinaryOperator::createAdd(
614 BinaryOperator::getNotArgument(cast<BinaryOperator>(Op1)),
615 ConstantExpr::getAdd(C, ConstantInt::get(I.getType(), 1)));
616 // -((uint)X >> 31) -> ((int)X >> 31)
617 // -((int)X >> 31) -> ((uint)X >> 31)
618 if (C->isNullValue()) {
619 Value *NoopCastedRHS = RemoveNoopCast(Op1);
620 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
621 if (SI->getOpcode() == Instruction::Shr)
622 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
624 if (SI->getType()->isSigned())
625 NewTy = SI->getType()->getUnsignedVersion();
627 NewTy = SI->getType()->getSignedVersion();
628 // Check to see if we are shifting out everything but the sign bit.
629 if (CU->getValue() == SI->getType()->getPrimitiveSize()*8-1) {
630 // Ok, the transformation is safe. Insert a cast of the incoming
631 // value, then the new shift, then the new cast.
632 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
633 SI->getOperand(0)->getName());
634 Value *InV = InsertNewInstBefore(FirstCast, I);
635 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
637 if (NewShift->getType() == I.getType())
640 InV = InsertNewInstBefore(NewShift, I);
641 return new CastInst(NewShift, I.getType());
647 // Try to fold constant sub into select arguments.
648 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
649 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
653 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1))
654 if (Op1I->hasOneUse()) {
655 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
656 // is not used by anyone else...
658 if (Op1I->getOpcode() == Instruction::Sub &&
659 !Op1I->getType()->isFloatingPoint()) {
660 // Swap the two operands of the subexpr...
661 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
662 Op1I->setOperand(0, IIOp1);
663 Op1I->setOperand(1, IIOp0);
665 // Create the new top level add instruction...
666 return BinaryOperator::createAdd(Op0, Op1);
669 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
671 if (Op1I->getOpcode() == Instruction::And &&
672 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
673 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
676 InsertNewInstBefore(BinaryOperator::createNot(OtherOp, "B.not"), I);
677 return BinaryOperator::createAnd(Op0, NewNot);
680 // X - X*C --> X * (1-C)
681 if (dyn_castFoldableMul(Op1I) == Op0) {
683 ConstantExpr::getSub(ConstantInt::get(I.getType(), 1),
684 cast<Constant>(cast<Instruction>(Op1)->getOperand(1)));
685 assert(CP1 && "Couldn't constant fold 1-C?");
686 return BinaryOperator::createMul(Op0, CP1);
690 // X*C - X --> X * (C-1)
691 if (dyn_castFoldableMul(Op0) == Op1) {
693 ConstantExpr::getSub(cast<Constant>(cast<Instruction>(Op0)->getOperand(1)),
694 ConstantInt::get(I.getType(), 1));
695 assert(CP1 && "Couldn't constant fold C - 1?");
696 return BinaryOperator::createMul(Op1, CP1);
702 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
703 /// really just returns true if the most significant (sign) bit is set.
704 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
705 if (RHS->getType()->isSigned()) {
706 // True if source is LHS < 0 or LHS <= -1
707 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
708 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
710 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
711 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
712 // the size of the integer type.
713 if (Opcode == Instruction::SetGE)
714 return RHSC->getValue() == 1ULL<<(RHS->getType()->getPrimitiveSize()*8-1);
715 if (Opcode == Instruction::SetGT)
716 return RHSC->getValue() ==
717 (1ULL << (RHS->getType()->getPrimitiveSize()*8-1))-1;
722 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
723 bool Changed = SimplifyCommutative(I);
724 Value *Op0 = I.getOperand(0);
726 // Simplify mul instructions with a constant RHS...
727 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
728 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
730 // ((X << C1)*C2) == (X * (C2 << C1))
731 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
732 if (SI->getOpcode() == Instruction::Shl)
733 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
734 return BinaryOperator::createMul(SI->getOperand(0),
735 ConstantExpr::getShl(CI, ShOp));
737 if (CI->isNullValue())
738 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
739 if (CI->equalsInt(1)) // X * 1 == X
740 return ReplaceInstUsesWith(I, Op0);
741 if (CI->isAllOnesValue()) // X * -1 == 0 - X
742 return BinaryOperator::createNeg(Op0, I.getName());
744 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
745 if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
746 return new ShiftInst(Instruction::Shl, Op0,
747 ConstantUInt::get(Type::UByteTy, C));
749 ConstantFP *Op1F = cast<ConstantFP>(Op1);
750 if (Op1F->isNullValue())
751 return ReplaceInstUsesWith(I, Op1);
753 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
754 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
755 if (Op1F->getValue() == 1.0)
756 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
759 // Try to fold constant mul into select arguments.
760 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
761 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
765 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
766 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
767 return BinaryOperator::createMul(Op0v, Op1v);
769 // If one of the operands of the multiply is a cast from a boolean value, then
770 // we know the bool is either zero or one, so this is a 'masking' multiply.
771 // See if we can simplify things based on how the boolean was originally
773 CastInst *BoolCast = 0;
774 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
775 if (CI->getOperand(0)->getType() == Type::BoolTy)
778 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
779 if (CI->getOperand(0)->getType() == Type::BoolTy)
782 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
783 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
784 const Type *SCOpTy = SCIOp0->getType();
786 // If the setcc is true iff the sign bit of X is set, then convert this
787 // multiply into a shift/and combination.
788 if (isa<ConstantInt>(SCIOp1) &&
789 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
790 // Shift the X value right to turn it into "all signbits".
791 Constant *Amt = ConstantUInt::get(Type::UByteTy,
792 SCOpTy->getPrimitiveSize()*8-1);
793 if (SCIOp0->getType()->isUnsigned()) {
794 const Type *NewTy = SCIOp0->getType()->getSignedVersion();
795 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
796 SCIOp0->getName()), I);
800 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
801 BoolCast->getOperand(0)->getName()+
804 // If the multiply type is not the same as the source type, sign extend
805 // or truncate to the multiply type.
806 if (I.getType() != V->getType())
807 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
809 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
810 return BinaryOperator::createAnd(V, OtherOp);
815 return Changed ? &I : 0;
818 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
819 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
821 if (RHS->equalsInt(1))
822 return ReplaceInstUsesWith(I, I.getOperand(0));
825 if (RHS->isAllOnesValue())
826 return BinaryOperator::createNeg(I.getOperand(0));
828 // Check to see if this is an unsigned division with an exact power of 2,
829 // if so, convert to a right shift.
830 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
831 if (uint64_t Val = C->getValue()) // Don't break X / 0
832 if (uint64_t C = Log2(Val))
833 return new ShiftInst(Instruction::Shr, I.getOperand(0),
834 ConstantUInt::get(Type::UByteTy, C));
837 // 0 / X == 0, we don't need to preserve faults!
838 if (ConstantInt *LHS = dyn_cast<ConstantInt>(I.getOperand(0)))
839 if (LHS->equalsInt(0))
840 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
846 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
847 if (I.getType()->isSigned())
848 if (Value *RHSNeg = dyn_castNegVal(I.getOperand(1)))
849 if (!isa<ConstantSInt>(RHSNeg) ||
850 cast<ConstantSInt>(RHSNeg)->getValue() >= 0) {
852 AddUsesToWorkList(I);
853 I.setOperand(1, RHSNeg);
857 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I.getOperand(1))) {
858 if (RHS->equalsInt(1)) // X % 1 == 0
859 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
861 // Check to see if this is an unsigned remainder with an exact power of 2,
862 // if so, convert to a bitwise and.
863 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
864 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
865 if (!(Val & (Val-1))) // Power of 2
866 return BinaryOperator::createAnd(I.getOperand(0),
867 ConstantUInt::get(I.getType(), Val-1));
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()));
878 // isMaxValueMinusOne - return true if this is Max-1
879 static bool isMaxValueMinusOne(const ConstantInt *C) {
880 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
881 // Calculate -1 casted to the right type...
882 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
883 uint64_t Val = ~0ULL; // All ones
884 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
885 return CU->getValue() == Val-1;
888 const ConstantSInt *CS = cast<ConstantSInt>(C);
890 // Calculate 0111111111..11111
891 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
892 int64_t Val = INT64_MAX; // All ones
893 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
894 return CS->getValue() == Val-1;
897 // isMinValuePlusOne - return true if this is Min+1
898 static bool isMinValuePlusOne(const ConstantInt *C) {
899 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
900 return CU->getValue() == 1;
902 const ConstantSInt *CS = cast<ConstantSInt>(C);
904 // Calculate 1111111111000000000000
905 unsigned TypeBits = C->getType()->getPrimitiveSize()*8;
906 int64_t Val = -1; // All ones
907 Val <<= TypeBits-1; // Shift over to the right spot
908 return CS->getValue() == Val+1;
911 // isOneBitSet - Return true if there is exactly one bit set in the specified
913 static bool isOneBitSet(const ConstantInt *CI) {
914 uint64_t V = CI->getRawValue();
915 return V && (V & (V-1)) == 0;
918 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
919 /// are carefully arranged to allow folding of expressions such as:
921 /// (A < B) | (A > B) --> (A != B)
923 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
924 /// represents that the comparison is true if A == B, and bit value '1' is true
927 static unsigned getSetCondCode(const SetCondInst *SCI) {
928 switch (SCI->getOpcode()) {
930 case Instruction::SetGT: return 1;
931 case Instruction::SetEQ: return 2;
932 case Instruction::SetGE: return 3;
933 case Instruction::SetLT: return 4;
934 case Instruction::SetNE: return 5;
935 case Instruction::SetLE: return 6;
938 assert(0 && "Invalid SetCC opcode!");
943 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
944 /// opcode and two operands into either a constant true or false, or a brand new
945 /// SetCC instruction.
946 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
948 case 0: return ConstantBool::False;
949 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
950 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
951 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
952 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
953 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
954 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
955 case 7: return ConstantBool::True;
956 default: assert(0 && "Illegal SetCCCode!"); return 0;
960 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
961 struct FoldSetCCLogical {
964 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
965 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
966 bool shouldApply(Value *V) const {
967 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
968 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
969 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
972 Instruction *apply(BinaryOperator &Log) const {
973 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
974 if (SCI->getOperand(0) != LHS) {
975 assert(SCI->getOperand(1) == LHS);
976 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
979 unsigned LHSCode = getSetCondCode(SCI);
980 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
982 switch (Log.getOpcode()) {
983 case Instruction::And: Code = LHSCode & RHSCode; break;
984 case Instruction::Or: Code = LHSCode | RHSCode; break;
985 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
986 default: assert(0 && "Illegal logical opcode!"); return 0;
989 Value *RV = getSetCCValue(Code, LHS, RHS);
990 if (Instruction *I = dyn_cast<Instruction>(RV))
992 // Otherwise, it's a constant boolean value...
993 return IC.ReplaceInstUsesWith(Log, RV);
998 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
999 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
1000 // guaranteed to be either a shift instruction or a binary operator.
1001 Instruction *InstCombiner::OptAndOp(Instruction *Op,
1002 ConstantIntegral *OpRHS,
1003 ConstantIntegral *AndRHS,
1004 BinaryOperator &TheAnd) {
1005 Value *X = Op->getOperand(0);
1006 Constant *Together = 0;
1007 if (!isa<ShiftInst>(Op))
1008 Together = ConstantExpr::getAnd(AndRHS, OpRHS);
1010 switch (Op->getOpcode()) {
1011 case Instruction::Xor:
1012 if (Together->isNullValue()) {
1013 // (X ^ C1) & C2 --> (X & C2) iff (C1&C2) == 0
1014 return BinaryOperator::createAnd(X, AndRHS);
1015 } else if (Op->hasOneUse()) {
1016 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
1017 std::string OpName = Op->getName(); Op->setName("");
1018 Instruction *And = BinaryOperator::createAnd(X, AndRHS, OpName);
1019 InsertNewInstBefore(And, TheAnd);
1020 return BinaryOperator::createXor(And, Together);
1023 case Instruction::Or:
1024 // (X | C1) & C2 --> X & C2 iff C1 & C1 == 0
1025 if (Together->isNullValue())
1026 return BinaryOperator::createAnd(X, AndRHS);
1028 if (Together == AndRHS) // (X | C) & C --> C
1029 return ReplaceInstUsesWith(TheAnd, AndRHS);
1031 if (Op->hasOneUse() && Together != OpRHS) {
1032 // (X | C1) & C2 --> (X | (C1&C2)) & C2
1033 std::string Op0Name = Op->getName(); Op->setName("");
1034 Instruction *Or = BinaryOperator::createOr(X, Together, Op0Name);
1035 InsertNewInstBefore(Or, TheAnd);
1036 return BinaryOperator::createAnd(Or, AndRHS);
1040 case Instruction::Add:
1041 if (Op->hasOneUse()) {
1042 // Adding a one to a single bit bit-field should be turned into an XOR
1043 // of the bit. First thing to check is to see if this AND is with a
1044 // single bit constant.
1045 uint64_t AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1047 // Clear bits that are not part of the constant.
1048 AndRHSV &= (1ULL << AndRHS->getType()->getPrimitiveSize()*8)-1;
1050 // If there is only one bit set...
1051 if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
1052 // Ok, at this point, we know that we are masking the result of the
1053 // ADD down to exactly one bit. If the constant we are adding has
1054 // no bits set below this bit, then we can eliminate the ADD.
1055 uint64_t AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1057 // Check to see if any bits below the one bit set in AndRHSV are set.
1058 if ((AddRHS & (AndRHSV-1)) == 0) {
1059 // If not, the only thing that can effect the output of the AND is
1060 // the bit specified by AndRHSV. If that bit is set, the effect of
1061 // the XOR is to toggle the bit. If it is clear, then the ADD has
1063 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1064 TheAnd.setOperand(0, X);
1067 std::string Name = Op->getName(); Op->setName("");
1068 // Pull the XOR out of the AND.
1069 Instruction *NewAnd = BinaryOperator::createAnd(X, AndRHS, Name);
1070 InsertNewInstBefore(NewAnd, TheAnd);
1071 return BinaryOperator::createXor(NewAnd, AndRHS);
1078 case Instruction::Shl: {
1079 // We know that the AND will not produce any of the bits shifted in, so if
1080 // the anded constant includes them, clear them now!
1082 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1083 Constant *CI = ConstantExpr::getAnd(AndRHS,
1084 ConstantExpr::getShl(AllOne, OpRHS));
1086 TheAnd.setOperand(1, CI);
1091 case Instruction::Shr:
1092 // We know that the AND will not produce any of the bits shifted in, so if
1093 // the anded constant includes them, clear them now! This only applies to
1094 // unsigned shifts, because a signed shr may bring in set bits!
1096 if (AndRHS->getType()->isUnsigned()) {
1097 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1098 Constant *CI = ConstantExpr::getAnd(AndRHS,
1099 ConstantExpr::getShr(AllOne, OpRHS));
1101 TheAnd.setOperand(1, CI);
1111 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1112 bool Changed = SimplifyCommutative(I);
1113 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1115 // and X, X = X and X, 0 == 0
1116 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1117 return ReplaceInstUsesWith(I, Op1);
1120 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1121 if (RHS->isAllOnesValue())
1122 return ReplaceInstUsesWith(I, Op0);
1124 // Optimize a variety of ((val OP C1) & C2) combinations...
1125 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1126 Instruction *Op0I = cast<Instruction>(Op0);
1127 Value *X = Op0I->getOperand(0);
1128 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1129 if (Instruction *Res = OptAndOp(Op0I, Op0CI, RHS, I))
1133 // Try to fold constant and into select arguments.
1134 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1135 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1139 Value *Op0NotVal = dyn_castNotVal(Op0);
1140 Value *Op1NotVal = dyn_castNotVal(Op1);
1142 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1143 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1145 // (~A & ~B) == (~(A | B)) - Demorgan's Law
1146 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1147 Instruction *Or = BinaryOperator::createOr(Op0NotVal, Op1NotVal,
1148 I.getName()+".demorgan");
1149 InsertNewInstBefore(Or, I);
1150 return BinaryOperator::createNot(Or);
1153 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1154 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1155 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1158 return Changed ? &I : 0;
1163 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1164 bool Changed = SimplifyCommutative(I);
1165 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1167 // or X, X = X or X, 0 == X
1168 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1169 return ReplaceInstUsesWith(I, Op0);
1172 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1173 if (RHS->isAllOnesValue())
1174 return ReplaceInstUsesWith(I, Op1);
1176 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1177 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1178 if (Op0I->getOpcode() == Instruction::And && isOnlyUse(Op0))
1179 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1180 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1181 Instruction *Or = BinaryOperator::createOr(Op0I->getOperand(0), RHS,
1183 InsertNewInstBefore(Or, I);
1184 return BinaryOperator::createAnd(Or, ConstantExpr::getOr(RHS, Op0CI));
1187 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1188 if (Op0I->getOpcode() == Instruction::Xor && isOnlyUse(Op0))
1189 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1))) {
1190 std::string Op0Name = Op0I->getName(); Op0I->setName("");
1191 Instruction *Or = BinaryOperator::createOr(Op0I->getOperand(0), RHS,
1193 InsertNewInstBefore(Or, I);
1194 return BinaryOperator::createXor(Or,
1195 ConstantExpr::getAnd(Op0CI,
1196 ConstantExpr::getNot(RHS)));
1200 // Try to fold constant and into select arguments.
1201 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1202 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1206 // (A & C1)|(A & C2) == A & (C1|C2)
1207 if (Instruction *LHS = dyn_cast<BinaryOperator>(Op0))
1208 if (Instruction *RHS = dyn_cast<BinaryOperator>(Op1))
1209 if (LHS->getOperand(0) == RHS->getOperand(0))
1210 if (Constant *C0 = dyn_castMaskingAnd(LHS))
1211 if (Constant *C1 = dyn_castMaskingAnd(RHS))
1212 return BinaryOperator::createAnd(LHS->getOperand(0),
1213 ConstantExpr::getOr(C0, C1));
1215 Value *Op0NotVal = dyn_castNotVal(Op0);
1216 Value *Op1NotVal = dyn_castNotVal(Op1);
1218 if (Op1 == Op0NotVal) // ~A | A == -1
1219 return ReplaceInstUsesWith(I,
1220 ConstantIntegral::getAllOnesValue(I.getType()));
1222 if (Op0 == Op1NotVal) // A | ~A == -1
1223 return ReplaceInstUsesWith(I,
1224 ConstantIntegral::getAllOnesValue(I.getType()));
1226 // (~A | ~B) == (~(A & B)) - Demorgan's Law
1227 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1228 Value *And = InsertNewInstBefore(
1229 BinaryOperator::createAnd(Op0NotVal,
1230 Op1NotVal,I.getName()+".demorgan"),I);
1231 return BinaryOperator::createNot(And);
1234 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1235 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1236 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1239 return Changed ? &I : 0;
1242 // XorSelf - Implements: X ^ X --> 0
1245 XorSelf(Value *rhs) : RHS(rhs) {}
1246 bool shouldApply(Value *LHS) const { return LHS == RHS; }
1247 Instruction *apply(BinaryOperator &Xor) const {
1253 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
1254 bool Changed = SimplifyCommutative(I);
1255 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1257 // xor X, X = 0, even if X is nested in a sequence of Xor's.
1258 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
1259 assert(Result == &I && "AssociativeOpt didn't work?");
1260 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1263 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1265 if (RHS->isNullValue())
1266 return ReplaceInstUsesWith(I, Op0);
1268 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
1269 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
1270 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
1271 if (RHS == ConstantBool::True && SCI->hasOneUse())
1272 return new SetCondInst(SCI->getInverseCondition(),
1273 SCI->getOperand(0), SCI->getOperand(1));
1275 // ~(c-X) == X-c-1 == X+(-c-1)
1276 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
1277 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
1278 Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
1279 Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
1280 ConstantInt::get(I.getType(), 1));
1281 return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
1284 // ~(~X & Y) --> (X | ~Y)
1285 if (Op0I->getOpcode() == Instruction::And && RHS->isAllOnesValue()) {
1286 if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
1287 if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
1289 BinaryOperator::createNot(Op0I->getOperand(1),
1290 Op0I->getOperand(1)->getName()+".not");
1291 InsertNewInstBefore(NotY, I);
1292 return BinaryOperator::createOr(Op0NotVal, NotY);
1296 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1297 switch (Op0I->getOpcode()) {
1298 case Instruction::Add:
1299 // ~(X-c) --> (-c-1)-X
1300 if (RHS->isAllOnesValue()) {
1301 Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
1302 return BinaryOperator::createSub(
1303 ConstantExpr::getSub(NegOp0CI,
1304 ConstantInt::get(I.getType(), 1)),
1305 Op0I->getOperand(0));
1308 case Instruction::And:
1309 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
1310 if (ConstantExpr::getAnd(RHS, Op0CI)->isNullValue())
1311 return BinaryOperator::createOr(Op0, RHS);
1313 case Instruction::Or:
1314 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
1315 if (ConstantExpr::getAnd(RHS, Op0CI) == RHS)
1316 return BinaryOperator::createAnd(Op0, ConstantExpr::getNot(RHS));
1322 // Try to fold constant and into select arguments.
1323 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1324 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1328 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
1330 return ReplaceInstUsesWith(I,
1331 ConstantIntegral::getAllOnesValue(I.getType()));
1333 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
1335 return ReplaceInstUsesWith(I,
1336 ConstantIntegral::getAllOnesValue(I.getType()));
1338 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
1339 if (Op1I->getOpcode() == Instruction::Or) {
1340 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
1341 cast<BinaryOperator>(Op1I)->swapOperands();
1343 std::swap(Op0, Op1);
1344 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
1346 std::swap(Op0, Op1);
1348 } else if (Op1I->getOpcode() == Instruction::Xor) {
1349 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
1350 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
1351 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
1352 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
1355 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
1356 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
1357 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
1358 cast<BinaryOperator>(Op0I)->swapOperands();
1359 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
1360 Value *NotB = InsertNewInstBefore(BinaryOperator::createNot(Op1,
1361 Op1->getName()+".not"), I);
1362 return BinaryOperator::createAnd(Op0I->getOperand(0), NotB);
1364 } else if (Op0I->getOpcode() == Instruction::Xor) {
1365 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
1366 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
1367 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
1368 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
1371 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1^C2 == 0
1372 if (Constant *C1 = dyn_castMaskingAnd(Op0))
1373 if (Constant *C2 = dyn_castMaskingAnd(Op1))
1374 if (ConstantExpr::getAnd(C1, C2)->isNullValue())
1375 return BinaryOperator::createOr(Op0, Op1);
1377 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
1378 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
1379 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1382 return Changed ? &I : 0;
1385 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
1386 static Constant *AddOne(ConstantInt *C) {
1387 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
1389 static Constant *SubOne(ConstantInt *C) {
1390 return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
1393 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
1394 // true when both operands are equal...
1396 static bool isTrueWhenEqual(Instruction &I) {
1397 return I.getOpcode() == Instruction::SetEQ ||
1398 I.getOpcode() == Instruction::SetGE ||
1399 I.getOpcode() == Instruction::SetLE;
1402 Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
1403 bool Changed = SimplifyCommutative(I);
1404 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1405 const Type *Ty = Op0->getType();
1409 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
1411 // setcc <global/alloca*>, 0 - Global/Stack value addresses are never null!
1412 if (isa<ConstantPointerNull>(Op1) &&
1413 (isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0)))
1414 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
1417 // setcc's with boolean values can always be turned into bitwise operations
1418 if (Ty == Type::BoolTy) {
1419 // If this is <, >, or !=, we can change this into a simple xor instruction
1420 if (!isTrueWhenEqual(I))
1421 return BinaryOperator::createXor(Op0, Op1);
1423 // Otherwise we need to make a temporary intermediate instruction and insert
1424 // it into the instruction stream. This is what we are after:
1426 // seteq bool %A, %B -> ~(A^B)
1427 // setle bool %A, %B -> ~A | B
1428 // setge bool %A, %B -> A | ~B
1430 if (I.getOpcode() == Instruction::SetEQ) { // seteq case
1431 Instruction *Xor = BinaryOperator::createXor(Op0, Op1, I.getName()+"tmp");
1432 InsertNewInstBefore(Xor, I);
1433 return BinaryOperator::createNot(Xor);
1436 // Handle the setXe cases...
1437 assert(I.getOpcode() == Instruction::SetGE ||
1438 I.getOpcode() == Instruction::SetLE);
1440 if (I.getOpcode() == Instruction::SetGE)
1441 std::swap(Op0, Op1); // Change setge -> setle
1443 // Now we just have the SetLE case.
1444 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
1445 InsertNewInstBefore(Not, I);
1446 return BinaryOperator::createOr(Not, Op1);
1449 // See if we are doing a comparison between a constant and an instruction that
1450 // can be folded into the comparison.
1451 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1452 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
1453 if (LHSI->hasOneUse())
1454 switch (LHSI->getOpcode()) {
1455 case Instruction::And:
1456 if (isa<ConstantInt>(LHSI->getOperand(1)) &&
1457 LHSI->getOperand(0)->hasOneUse()) {
1458 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
1459 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
1460 // happens a LOT in code produced by the C front-end, for bitfield
1462 ShiftInst *Shift = dyn_cast<ShiftInst>(LHSI->getOperand(0));
1463 ConstantUInt *ShAmt;
1464 ShAmt = Shift ? dyn_cast<ConstantUInt>(Shift->getOperand(1)) : 0;
1465 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
1466 const Type *Ty = LHSI->getType();
1468 // We can fold this as long as we can't shift unknown bits
1469 // into the mask. This can only happen with signed shift
1470 // rights, as they sign-extend.
1472 bool CanFold = Shift->getOpcode() != Instruction::Shr ||
1473 Shift->getType()->isUnsigned();
1475 // To test for the bad case of the signed shr, see if any
1476 // of the bits shifted in could be tested after the mask.
1477 Constant *OShAmt = ConstantUInt::get(Type::UByteTy,
1478 Ty->getPrimitiveSize()*8-ShAmt->getValue());
1480 ConstantExpr::getShl(ConstantInt::getAllOnesValue(Ty), OShAmt);
1481 if (ConstantExpr::getAnd(ShVal, AndCST)->isNullValue())
1486 unsigned ShiftOp = Shift->getOpcode() == Instruction::Shl
1487 ? Instruction::Shr : Instruction::Shl;
1488 Constant *NewCst = ConstantExpr::get(ShiftOp, CI, ShAmt);
1490 // Check to see if we are shifting out any of the bits being
1492 if (ConstantExpr::get(Shift->getOpcode(), NewCst, ShAmt) != CI){
1493 // If we shifted bits out, the fold is not going to work out.
1494 // As a special case, check to see if this means that the
1495 // result is always true or false now.
1496 if (I.getOpcode() == Instruction::SetEQ)
1497 return ReplaceInstUsesWith(I, ConstantBool::False);
1498 if (I.getOpcode() == Instruction::SetNE)
1499 return ReplaceInstUsesWith(I, ConstantBool::True);
1501 I.setOperand(1, NewCst);
1502 LHSI->setOperand(1, ConstantExpr::get(ShiftOp, AndCST,ShAmt));
1503 LHSI->setOperand(0, Shift->getOperand(0));
1504 WorkList.push_back(Shift); // Shift is dead.
1505 AddUsesToWorkList(I);
1512 case Instruction::Div:
1513 if (0 && isa<ConstantInt>(LHSI->getOperand(1))) {
1514 std::cerr << "COULD FOLD: " << *LHSI;
1515 std::cerr << "COULD FOLD: " << I << "\n";
1518 case Instruction::Select:
1519 // If either operand of the select is a constant, we can fold the
1520 // comparison into the select arms, which will cause one to be
1521 // constant folded and the select turned into a bitwise or.
1522 Value *Op1 = 0, *Op2 = 0;
1523 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
1524 // Fold the known value into the constant operand.
1525 Op1 = ConstantExpr::get(I.getOpcode(), C, CI);
1526 // Insert a new SetCC of the other select operand.
1527 Op2 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
1528 LHSI->getOperand(2), CI,
1530 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
1531 // Fold the known value into the constant operand.
1532 Op2 = ConstantExpr::get(I.getOpcode(), C, CI);
1533 // Insert a new SetCC of the other select operand.
1534 Op1 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
1535 LHSI->getOperand(1), CI,
1540 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
1544 // Simplify seteq and setne instructions...
1545 if (I.getOpcode() == Instruction::SetEQ ||
1546 I.getOpcode() == Instruction::SetNE) {
1547 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1549 // If the first operand is (and|or|xor) with a constant, and the second
1550 // operand is a constant, simplify a bit.
1551 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1552 switch (BO->getOpcode()) {
1553 case Instruction::Rem:
1554 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
1555 if (CI->isNullValue() && isa<ConstantSInt>(BO->getOperand(1)) &&
1557 cast<ConstantSInt>(BO->getOperand(1))->getValue() > 1)
1559 Log2(cast<ConstantSInt>(BO->getOperand(1))->getValue())) {
1560 const Type *UTy = BO->getType()->getUnsignedVersion();
1561 Value *NewX = InsertNewInstBefore(new CastInst(BO->getOperand(0),
1563 Constant *RHSCst = ConstantUInt::get(UTy, 1ULL << L2);
1564 Value *NewRem =InsertNewInstBefore(BinaryOperator::createRem(NewX,
1565 RHSCst, BO->getName()), I);
1566 return BinaryOperator::create(I.getOpcode(), NewRem,
1567 Constant::getNullValue(UTy));
1571 case Instruction::Add:
1572 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
1573 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1574 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1575 ConstantExpr::getSub(CI, BOp1C));
1576 } else if (CI->isNullValue()) {
1577 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1578 // efficiently invertible, or if the add has just this one use.
1579 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1581 if (Value *NegVal = dyn_castNegVal(BOp1))
1582 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1583 else if (Value *NegVal = dyn_castNegVal(BOp0))
1584 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1585 else if (BO->hasOneUse()) {
1586 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1588 InsertNewInstBefore(Neg, I);
1589 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1593 case Instruction::Xor:
1594 // For the xor case, we can xor two constants together, eliminating
1595 // the explicit xor.
1596 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1597 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1598 ConstantExpr::getXor(CI, BOC));
1601 case Instruction::Sub:
1602 // Replace (([sub|xor] A, B) != 0) with (A != B)
1603 if (CI->isNullValue())
1604 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1608 case Instruction::Or:
1609 // If bits are being or'd in that are not present in the constant we
1610 // are comparing against, then the comparison could never succeed!
1611 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1612 Constant *NotCI = ConstantExpr::getNot(CI);
1613 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
1614 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1618 case Instruction::And:
1619 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1620 // If bits are being compared against that are and'd out, then the
1621 // comparison can never succeed!
1622 if (!ConstantExpr::getAnd(CI,
1623 ConstantExpr::getNot(BOC))->isNullValue())
1624 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1626 // If we have ((X & C) == C), turn it into ((X & C) != 0).
1627 if (CI == BOC && isOneBitSet(CI))
1628 return new SetCondInst(isSetNE ? Instruction::SetEQ :
1629 Instruction::SetNE, Op0,
1630 Constant::getNullValue(CI->getType()));
1632 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1633 // to be a signed value as appropriate.
1634 if (isSignBit(BOC)) {
1635 Value *X = BO->getOperand(0);
1636 // If 'X' is not signed, insert a cast now...
1637 if (!BOC->getType()->isSigned()) {
1638 const Type *DestTy = BOC->getType()->getSignedVersion();
1639 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1640 InsertNewInstBefore(NewCI, I);
1643 return new SetCondInst(isSetNE ? Instruction::SetLT :
1644 Instruction::SetGE, X,
1645 Constant::getNullValue(X->getType()));
1651 } else { // Not a SetEQ/SetNE
1652 // If the LHS is a cast from an integral value of the same size,
1653 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1654 Value *CastOp = Cast->getOperand(0);
1655 const Type *SrcTy = CastOp->getType();
1656 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1657 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1658 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1659 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1660 "Source and destination signednesses should differ!");
1661 if (Cast->getType()->isSigned()) {
1662 // If this is a signed comparison, check for comparisons in the
1663 // vicinity of zero.
1664 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1666 return BinaryOperator::createSetGT(CastOp,
1667 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1668 else if (I.getOpcode() == Instruction::SetGT &&
1669 cast<ConstantSInt>(CI)->getValue() == -1)
1670 // X > -1 => x < 128
1671 return BinaryOperator::createSetLT(CastOp,
1672 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1674 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1675 if (I.getOpcode() == Instruction::SetLT &&
1676 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1677 // X < 128 => X > -1
1678 return BinaryOperator::createSetGT(CastOp,
1679 ConstantSInt::get(SrcTy, -1));
1680 else if (I.getOpcode() == Instruction::SetGT &&
1681 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1683 return BinaryOperator::createSetLT(CastOp,
1684 Constant::getNullValue(SrcTy));
1690 // Check to see if we are comparing against the minimum or maximum value...
1691 if (CI->isMinValue()) {
1692 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1693 return ReplaceInstUsesWith(I, ConstantBool::False);
1694 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1695 return ReplaceInstUsesWith(I, ConstantBool::True);
1696 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1697 return BinaryOperator::createSetEQ(Op0, Op1);
1698 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1699 return BinaryOperator::createSetNE(Op0, Op1);
1701 } else if (CI->isMaxValue()) {
1702 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1703 return ReplaceInstUsesWith(I, ConstantBool::False);
1704 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1705 return ReplaceInstUsesWith(I, ConstantBool::True);
1706 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1707 return BinaryOperator::createSetEQ(Op0, Op1);
1708 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1709 return BinaryOperator::createSetNE(Op0, Op1);
1711 // Comparing against a value really close to min or max?
1712 } else if (isMinValuePlusOne(CI)) {
1713 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1714 return BinaryOperator::createSetEQ(Op0, SubOne(CI));
1715 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1716 return BinaryOperator::createSetNE(Op0, SubOne(CI));
1718 } else if (isMaxValueMinusOne(CI)) {
1719 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1720 return BinaryOperator::createSetEQ(Op0, AddOne(CI));
1721 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1722 return BinaryOperator::createSetNE(Op0, AddOne(CI));
1725 // If we still have a setle or setge instruction, turn it into the
1726 // appropriate setlt or setgt instruction. Since the border cases have
1727 // already been handled above, this requires little checking.
1729 if (I.getOpcode() == Instruction::SetLE)
1730 return BinaryOperator::createSetLT(Op0, AddOne(CI));
1731 if (I.getOpcode() == Instruction::SetGE)
1732 return BinaryOperator::createSetGT(Op0, SubOne(CI));
1735 // Test to see if the operands of the setcc are casted versions of other
1736 // values. If the cast can be stripped off both arguments, we do so now.
1737 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1738 Value *CastOp0 = CI->getOperand(0);
1739 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1740 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1741 (I.getOpcode() == Instruction::SetEQ ||
1742 I.getOpcode() == Instruction::SetNE)) {
1743 // We keep moving the cast from the left operand over to the right
1744 // operand, where it can often be eliminated completely.
1747 // If operand #1 is a cast instruction, see if we can eliminate it as
1749 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1750 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1752 Op1 = CI2->getOperand(0);
1754 // If Op1 is a constant, we can fold the cast into the constant.
1755 if (Op1->getType() != Op0->getType())
1756 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1757 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1759 // Otherwise, cast the RHS right before the setcc
1760 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1761 InsertNewInstBefore(cast<Instruction>(Op1), I);
1763 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1766 // Handle the special case of: setcc (cast bool to X), <cst>
1767 // This comes up when you have code like
1770 // For generality, we handle any zero-extension of any operand comparison
1772 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1773 const Type *SrcTy = CastOp0->getType();
1774 const Type *DestTy = Op0->getType();
1775 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1776 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1777 // Ok, we have an expansion of operand 0 into a new type. Get the
1778 // constant value, masink off bits which are not set in the RHS. These
1779 // could be set if the destination value is signed.
1780 uint64_t ConstVal = ConstantRHS->getRawValue();
1781 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1783 // If the constant we are comparing it with has high bits set, which
1784 // don't exist in the original value, the values could never be equal,
1785 // because the source would be zero extended.
1787 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1788 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1789 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1790 switch (I.getOpcode()) {
1791 default: assert(0 && "Unknown comparison type!");
1792 case Instruction::SetEQ:
1793 return ReplaceInstUsesWith(I, ConstantBool::False);
1794 case Instruction::SetNE:
1795 return ReplaceInstUsesWith(I, ConstantBool::True);
1796 case Instruction::SetLT:
1797 case Instruction::SetLE:
1798 if (DestTy->isSigned() && HasSignBit)
1799 return ReplaceInstUsesWith(I, ConstantBool::False);
1800 return ReplaceInstUsesWith(I, ConstantBool::True);
1801 case Instruction::SetGT:
1802 case Instruction::SetGE:
1803 if (DestTy->isSigned() && HasSignBit)
1804 return ReplaceInstUsesWith(I, ConstantBool::True);
1805 return ReplaceInstUsesWith(I, ConstantBool::False);
1809 // Otherwise, we can replace the setcc with a setcc of the smaller
1811 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1812 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1816 return Changed ? &I : 0;
1821 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1822 assert(I.getOperand(1)->getType() == Type::UByteTy);
1823 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1824 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1826 // shl X, 0 == X and shr X, 0 == X
1827 // shl 0, X == 0 and shr 0, X == 0
1828 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1829 Op0 == Constant::getNullValue(Op0->getType()))
1830 return ReplaceInstUsesWith(I, Op0);
1832 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1834 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1835 if (CSI->isAllOnesValue())
1836 return ReplaceInstUsesWith(I, CSI);
1838 // Try to fold constant and into select arguments.
1839 if (isa<Constant>(Op0))
1840 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1841 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1844 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1845 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1846 // of a signed value.
1848 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1849 if (CUI->getValue() >= TypeBits) {
1850 if (!Op0->getType()->isSigned() || isLeftShift)
1851 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1853 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1858 // ((X*C1) << C2) == (X * (C1 << C2))
1859 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1860 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1861 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1862 return BinaryOperator::createMul(BO->getOperand(0),
1863 ConstantExpr::getShl(BOOp, CUI));
1865 // Try to fold constant and into select arguments.
1866 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1867 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1870 // If the operand is an bitwise operator with a constant RHS, and the
1871 // shift is the only use, we can pull it out of the shift.
1872 if (Op0->hasOneUse())
1873 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1874 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1875 bool isValid = true; // Valid only for And, Or, Xor
1876 bool highBitSet = false; // Transform if high bit of constant set?
1878 switch (Op0BO->getOpcode()) {
1879 default: isValid = false; break; // Do not perform transform!
1880 case Instruction::Or:
1881 case Instruction::Xor:
1884 case Instruction::And:
1889 // If this is a signed shift right, and the high bit is modified
1890 // by the logical operation, do not perform the transformation.
1891 // The highBitSet boolean indicates the value of the high bit of
1892 // the constant which would cause it to be modified for this
1895 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1896 uint64_t Val = Op0C->getRawValue();
1897 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1901 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1903 Instruction *NewShift =
1904 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1907 InsertNewInstBefore(NewShift, I);
1909 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1914 // If this is a shift of a shift, see if we can fold the two together...
1915 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1916 if (ConstantUInt *ShiftAmt1C =
1917 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1918 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1919 unsigned ShiftAmt2 = CUI->getValue();
1921 // Check for (A << c1) << c2 and (A >> c1) >> c2
1922 if (I.getOpcode() == Op0SI->getOpcode()) {
1923 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1924 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1925 Amt = Op0->getType()->getPrimitiveSize()*8;
1926 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1927 ConstantUInt::get(Type::UByteTy, Amt));
1930 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1931 // signed types, we can only support the (A >> c1) << c2 configuration,
1932 // because it can not turn an arbitrary bit of A into a sign bit.
1933 if (I.getType()->isUnsigned() || isLeftShift) {
1934 // Calculate bitmask for what gets shifted off the edge...
1935 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1937 C = ConstantExpr::getShl(C, ShiftAmt1C);
1939 C = ConstantExpr::getShr(C, ShiftAmt1C);
1942 BinaryOperator::createAnd(Op0SI->getOperand(0), C,
1943 Op0SI->getOperand(0)->getName()+".mask");
1944 InsertNewInstBefore(Mask, I);
1946 // Figure out what flavor of shift we should use...
1947 if (ShiftAmt1 == ShiftAmt2)
1948 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1949 else if (ShiftAmt1 < ShiftAmt2) {
1950 return new ShiftInst(I.getOpcode(), Mask,
1951 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1953 return new ShiftInst(Op0SI->getOpcode(), Mask,
1954 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1970 /// getCastType - In the future, we will split the cast instruction into these
1971 /// various types. Until then, we have to do the analysis here.
1972 static CastType getCastType(const Type *Src, const Type *Dest) {
1973 assert(Src->isIntegral() && Dest->isIntegral() &&
1974 "Only works on integral types!");
1975 unsigned SrcSize = Src->getPrimitiveSize()*8;
1976 if (Src == Type::BoolTy) SrcSize = 1;
1977 unsigned DestSize = Dest->getPrimitiveSize()*8;
1978 if (Dest == Type::BoolTy) DestSize = 1;
1980 if (SrcSize == DestSize) return Noop;
1981 if (SrcSize > DestSize) return Truncate;
1982 if (Src->isSigned()) return Signext;
1987 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1990 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1991 const Type *DstTy, TargetData *TD) {
1993 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1994 // are identical and the bits don't get reinterpreted (for example
1995 // int->float->int would not be allowed).
1996 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1999 // If we are casting between pointer and integer types, treat pointers as
2000 // integers of the appropriate size for the code below.
2001 if (isa<PointerType>(SrcTy)) SrcTy = TD->getIntPtrType();
2002 if (isa<PointerType>(MidTy)) MidTy = TD->getIntPtrType();
2003 if (isa<PointerType>(DstTy)) DstTy = TD->getIntPtrType();
2005 // Allow free casting and conversion of sizes as long as the sign doesn't
2007 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
2008 CastType FirstCast = getCastType(SrcTy, MidTy);
2009 CastType SecondCast = getCastType(MidTy, DstTy);
2011 // Capture the effect of these two casts. If the result is a legal cast,
2012 // the CastType is stored here, otherwise a special code is used.
2013 static const unsigned CastResult[] = {
2014 // First cast is noop
2016 // First cast is a truncate
2017 1, 1, 4, 4, // trunc->extend is not safe to eliminate
2018 // First cast is a sign ext
2019 2, 5, 2, 4, // signext->zeroext never ok
2020 // First cast is a zero ext
2024 unsigned Result = CastResult[FirstCast*4+SecondCast];
2026 default: assert(0 && "Illegal table value!");
2031 // FIXME: in the future, when LLVM has explicit sign/zeroextends and
2032 // truncates, we could eliminate more casts.
2033 return (unsigned)getCastType(SrcTy, DstTy) == Result;
2035 return false; // Not possible to eliminate this here.
2037 // Sign or zero extend followed by truncate is always ok if the result
2038 // is a truncate or noop.
2039 CastType ResultCast = getCastType(SrcTy, DstTy);
2040 if (ResultCast == Noop || ResultCast == Truncate)
2042 // Otherwise we are still growing the value, we are only safe if the
2043 // result will match the sign/zeroextendness of the result.
2044 return ResultCast == FirstCast;
2050 static bool ValueRequiresCast(const Value *V, const Type *Ty, TargetData *TD) {
2051 if (V->getType() == Ty || isa<Constant>(V)) return false;
2052 if (const CastInst *CI = dyn_cast<CastInst>(V))
2053 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty,
2059 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
2060 /// InsertBefore instruction. This is specialized a bit to avoid inserting
2061 /// casts that are known to not do anything...
2063 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
2064 Instruction *InsertBefore) {
2065 if (V->getType() == DestTy) return V;
2066 if (Constant *C = dyn_cast<Constant>(V))
2067 return ConstantExpr::getCast(C, DestTy);
2069 CastInst *CI = new CastInst(V, DestTy, V->getName());
2070 InsertNewInstBefore(CI, *InsertBefore);
2074 // CastInst simplification
2076 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
2077 Value *Src = CI.getOperand(0);
2079 // If the user is casting a value to the same type, eliminate this cast
2081 if (CI.getType() == Src->getType())
2082 return ReplaceInstUsesWith(CI, Src);
2084 // If casting the result of another cast instruction, try to eliminate this
2087 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
2088 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
2089 CSrc->getType(), CI.getType(), TD)) {
2090 // This instruction now refers directly to the cast's src operand. This
2091 // has a good chance of making CSrc dead.
2092 CI.setOperand(0, CSrc->getOperand(0));
2096 // If this is an A->B->A cast, and we are dealing with integral types, try
2097 // to convert this into a logical 'and' instruction.
2099 if (CSrc->getOperand(0)->getType() == CI.getType() &&
2100 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
2101 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
2102 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
2103 assert(CSrc->getType() != Type::ULongTy &&
2104 "Cannot have type bigger than ulong!");
2105 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
2106 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
2107 return BinaryOperator::createAnd(CSrc->getOperand(0), AndOp);
2111 // If this is a cast to bool, turn it into the appropriate setne instruction.
2112 if (CI.getType() == Type::BoolTy)
2113 return BinaryOperator::createSetNE(CI.getOperand(0),
2114 Constant::getNullValue(CI.getOperand(0)->getType()));
2116 // If casting the result of a getelementptr instruction with no offset, turn
2117 // this into a cast of the original pointer!
2119 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
2120 bool AllZeroOperands = true;
2121 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2122 if (!isa<Constant>(GEP->getOperand(i)) ||
2123 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
2124 AllZeroOperands = false;
2127 if (AllZeroOperands) {
2128 CI.setOperand(0, GEP->getOperand(0));
2133 // If we are casting a malloc or alloca to a pointer to a type of the same
2134 // size, rewrite the allocation instruction to allocate the "right" type.
2136 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
2137 if (AI->hasOneUse() && !AI->isArrayAllocation())
2138 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
2139 // Get the type really allocated and the type casted to...
2140 const Type *AllocElTy = AI->getAllocatedType();
2141 const Type *CastElTy = PTy->getElementType();
2142 if (AllocElTy->isSized() && CastElTy->isSized()) {
2143 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
2144 unsigned CastElTySize = TD->getTypeSize(CastElTy);
2146 // If the allocation is for an even multiple of the cast type size
2147 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
2148 Value *Amt = ConstantUInt::get(Type::UIntTy,
2149 AllocElTySize/CastElTySize);
2150 std::string Name = AI->getName(); AI->setName("");
2151 AllocationInst *New;
2152 if (isa<MallocInst>(AI))
2153 New = new MallocInst(CastElTy, Amt, Name);
2155 New = new AllocaInst(CastElTy, Amt, Name);
2156 InsertNewInstBefore(New, *AI);
2157 return ReplaceInstUsesWith(CI, New);
2162 // If the source value is an instruction with only this use, we can attempt to
2163 // propagate the cast into the instruction. Also, only handle integral types
2165 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
2166 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
2167 CI.getType()->isInteger()) { // Don't mess with casts to bool here
2168 const Type *DestTy = CI.getType();
2169 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
2170 unsigned DestBitSize = getTypeSizeInBits(DestTy);
2172 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
2173 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
2175 switch (SrcI->getOpcode()) {
2176 case Instruction::Add:
2177 case Instruction::Mul:
2178 case Instruction::And:
2179 case Instruction::Or:
2180 case Instruction::Xor:
2181 // If we are discarding information, or just changing the sign, rewrite.
2182 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
2183 // Don't insert two casts if they cannot be eliminated. We allow two
2184 // casts to be inserted if the sizes are the same. This could only be
2185 // converting signedness, which is a noop.
2186 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy,TD) ||
2187 !ValueRequiresCast(Op0, DestTy, TD)) {
2188 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2189 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
2190 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
2191 ->getOpcode(), Op0c, Op1c);
2195 case Instruction::Shl:
2196 // Allow changing the sign of the source operand. Do not allow changing
2197 // the size of the shift, UNLESS the shift amount is a constant. We
2198 // mush not change variable sized shifts to a smaller size, because it
2199 // is undefined to shift more bits out than exist in the value.
2200 if (DestBitSize == SrcBitSize ||
2201 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2202 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2203 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2212 /// GetSelectFoldableOperands - We want to turn code that looks like this:
2214 /// %D = select %cond, %C, %A
2216 /// %C = select %cond, %B, 0
2219 /// Assuming that the specified instruction is an operand to the select, return
2220 /// a bitmask indicating which operands of this instruction are foldable if they
2221 /// equal the other incoming value of the select.
2223 static unsigned GetSelectFoldableOperands(Instruction *I) {
2224 switch (I->getOpcode()) {
2225 case Instruction::Add:
2226 case Instruction::Mul:
2227 case Instruction::And:
2228 case Instruction::Or:
2229 case Instruction::Xor:
2230 return 3; // Can fold through either operand.
2231 case Instruction::Sub: // Can only fold on the amount subtracted.
2232 case Instruction::Shl: // Can only fold on the shift amount.
2233 case Instruction::Shr:
2236 return 0; // Cannot fold
2240 /// GetSelectFoldableConstant - For the same transformation as the previous
2241 /// function, return the identity constant that goes into the select.
2242 static Constant *GetSelectFoldableConstant(Instruction *I) {
2243 switch (I->getOpcode()) {
2244 default: assert(0 && "This cannot happen!"); abort();
2245 case Instruction::Add:
2246 case Instruction::Sub:
2247 case Instruction::Or:
2248 case Instruction::Xor:
2249 return Constant::getNullValue(I->getType());
2250 case Instruction::Shl:
2251 case Instruction::Shr:
2252 return Constant::getNullValue(Type::UByteTy);
2253 case Instruction::And:
2254 return ConstantInt::getAllOnesValue(I->getType());
2255 case Instruction::Mul:
2256 return ConstantInt::get(I->getType(), 1);
2260 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
2261 Value *CondVal = SI.getCondition();
2262 Value *TrueVal = SI.getTrueValue();
2263 Value *FalseVal = SI.getFalseValue();
2265 // select true, X, Y -> X
2266 // select false, X, Y -> Y
2267 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
2268 if (C == ConstantBool::True)
2269 return ReplaceInstUsesWith(SI, TrueVal);
2271 assert(C == ConstantBool::False);
2272 return ReplaceInstUsesWith(SI, FalseVal);
2275 // select C, X, X -> X
2276 if (TrueVal == FalseVal)
2277 return ReplaceInstUsesWith(SI, TrueVal);
2279 if (SI.getType() == Type::BoolTy)
2280 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
2281 if (C == ConstantBool::True) {
2282 // Change: A = select B, true, C --> A = or B, C
2283 return BinaryOperator::createOr(CondVal, FalseVal);
2285 // Change: A = select B, false, C --> A = and !B, C
2287 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2288 "not."+CondVal->getName()), SI);
2289 return BinaryOperator::createAnd(NotCond, FalseVal);
2291 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
2292 if (C == ConstantBool::False) {
2293 // Change: A = select B, C, false --> A = and B, C
2294 return BinaryOperator::createAnd(CondVal, TrueVal);
2296 // Change: A = select B, C, true --> A = or !B, C
2298 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2299 "not."+CondVal->getName()), SI);
2300 return BinaryOperator::createOr(NotCond, TrueVal);
2304 // Selecting between two integer constants?
2305 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
2306 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
2307 // select C, 1, 0 -> cast C to int
2308 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
2309 return new CastInst(CondVal, SI.getType());
2310 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
2311 // select C, 0, 1 -> cast !C to int
2313 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2314 "not."+CondVal->getName()), SI);
2315 return new CastInst(NotCond, SI.getType());
2318 // If one of the constants is zero (we know they can't both be) and we
2319 // have a setcc instruction with zero, and we have an 'and' with the
2320 // non-constant value, eliminate this whole mess. This corresponds to
2321 // cases like this: ((X & 27) ? 27 : 0)
2322 if (TrueValC->isNullValue() || FalseValC->isNullValue())
2323 if (Instruction *IC = dyn_cast<Instruction>(SI.getCondition()))
2324 if ((IC->getOpcode() == Instruction::SetEQ ||
2325 IC->getOpcode() == Instruction::SetNE) &&
2326 isa<ConstantInt>(IC->getOperand(1)) &&
2327 cast<Constant>(IC->getOperand(1))->isNullValue())
2328 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
2329 if (ICA->getOpcode() == Instruction::And &&
2330 isa<ConstantInt>(ICA->getOperand(1)) &&
2331 (ICA->getOperand(1) == TrueValC ||
2332 ICA->getOperand(1) == FalseValC) &&
2333 isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
2334 // Okay, now we know that everything is set up, we just don't
2335 // know whether we have a setne or seteq and whether the true or
2336 // false val is the zero.
2337 bool ShouldNotVal = !TrueValC->isNullValue();
2338 ShouldNotVal ^= IC->getOpcode() == Instruction::SetNE;
2341 V = InsertNewInstBefore(BinaryOperator::create(
2342 Instruction::Xor, V, ICA->getOperand(1)), SI);
2343 return ReplaceInstUsesWith(SI, V);
2347 // See if we are selecting two values based on a comparison of the two values.
2348 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
2349 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
2350 // Transform (X == Y) ? X : Y -> Y
2351 if (SCI->getOpcode() == Instruction::SetEQ)
2352 return ReplaceInstUsesWith(SI, FalseVal);
2353 // Transform (X != Y) ? X : Y -> X
2354 if (SCI->getOpcode() == Instruction::SetNE)
2355 return ReplaceInstUsesWith(SI, TrueVal);
2356 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2358 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
2359 // Transform (X == Y) ? Y : X -> X
2360 if (SCI->getOpcode() == Instruction::SetEQ)
2361 return ReplaceInstUsesWith(SI, FalseVal);
2362 // Transform (X != Y) ? Y : X -> Y
2363 if (SCI->getOpcode() == Instruction::SetNE)
2364 return ReplaceInstUsesWith(SI, TrueVal);
2365 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2369 // See if we can fold the select into one of our operands.
2370 if (SI.getType()->isInteger()) {
2371 // See the comment above GetSelectFoldableOperands for a description of the
2372 // transformation we are doing here.
2373 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
2374 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
2375 !isa<Constant>(FalseVal))
2376 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
2377 unsigned OpToFold = 0;
2378 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
2380 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
2385 Constant *C = GetSelectFoldableConstant(TVI);
2386 std::string Name = TVI->getName(); TVI->setName("");
2387 Instruction *NewSel =
2388 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
2390 InsertNewInstBefore(NewSel, SI);
2391 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
2392 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
2393 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
2394 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
2396 assert(0 && "Unknown instruction!!");
2401 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
2402 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
2403 !isa<Constant>(TrueVal))
2404 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
2405 unsigned OpToFold = 0;
2406 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
2408 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
2413 Constant *C = GetSelectFoldableConstant(FVI);
2414 std::string Name = FVI->getName(); FVI->setName("");
2415 Instruction *NewSel =
2416 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
2418 InsertNewInstBefore(NewSel, SI);
2419 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
2420 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
2421 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
2422 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
2424 assert(0 && "Unknown instruction!!");
2433 // CallInst simplification
2435 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2436 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2438 if (Function *F = CI.getCalledFunction())
2439 switch (F->getIntrinsicID()) {
2440 case Intrinsic::memmove:
2441 case Intrinsic::memcpy:
2442 case Intrinsic::memset:
2443 // memmove/cpy/set of zero bytes is a noop.
2444 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2445 if (NumBytes->isNullValue())
2446 return EraseInstFromFunction(CI);
2453 return visitCallSite(&CI);
2456 // InvokeInst simplification
2458 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2459 return visitCallSite(&II);
2462 // visitCallSite - Improvements for call and invoke instructions.
2464 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2465 bool Changed = false;
2467 // If the callee is a constexpr cast of a function, attempt to move the cast
2468 // to the arguments of the call/invoke.
2469 if (transformConstExprCastCall(CS)) return 0;
2471 Value *Callee = CS.getCalledValue();
2472 const PointerType *PTy = cast<PointerType>(Callee->getType());
2473 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2474 if (FTy->isVarArg()) {
2475 // See if we can optimize any arguments passed through the varargs area of
2477 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2478 E = CS.arg_end(); I != E; ++I)
2479 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2480 // If this cast does not effect the value passed through the varargs
2481 // area, we can eliminate the use of the cast.
2482 Value *Op = CI->getOperand(0);
2483 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2490 return Changed ? CS.getInstruction() : 0;
2493 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2494 // attempt to move the cast to the arguments of the call/invoke.
2496 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2497 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2498 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2499 if (CE->getOpcode() != Instruction::Cast || !isa<Function>(CE->getOperand(0)))
2501 Function *Callee = cast<Function>(CE->getOperand(0));
2502 Instruction *Caller = CS.getInstruction();
2504 // Okay, this is a cast from a function to a different type. Unless doing so
2505 // would cause a type conversion of one of our arguments, change this call to
2506 // be a direct call with arguments casted to the appropriate types.
2508 const FunctionType *FT = Callee->getFunctionType();
2509 const Type *OldRetTy = Caller->getType();
2511 // Check to see if we are changing the return type...
2512 if (OldRetTy != FT->getReturnType()) {
2513 if (Callee->isExternal() &&
2514 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2515 !Caller->use_empty())
2516 return false; // Cannot transform this return value...
2518 // If the callsite is an invoke instruction, and the return value is used by
2519 // a PHI node in a successor, we cannot change the return type of the call
2520 // because there is no place to put the cast instruction (without breaking
2521 // the critical edge). Bail out in this case.
2522 if (!Caller->use_empty())
2523 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2524 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2526 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2527 if (PN->getParent() == II->getNormalDest() ||
2528 PN->getParent() == II->getUnwindDest())
2532 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2533 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2535 CallSite::arg_iterator AI = CS.arg_begin();
2536 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2537 const Type *ParamTy = FT->getParamType(i);
2538 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2539 if (Callee->isExternal() && !isConvertible) return false;
2542 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2543 Callee->isExternal())
2544 return false; // Do not delete arguments unless we have a function body...
2546 // Okay, we decided that this is a safe thing to do: go ahead and start
2547 // inserting cast instructions as necessary...
2548 std::vector<Value*> Args;
2549 Args.reserve(NumActualArgs);
2551 AI = CS.arg_begin();
2552 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2553 const Type *ParamTy = FT->getParamType(i);
2554 if ((*AI)->getType() == ParamTy) {
2555 Args.push_back(*AI);
2557 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
2562 // If the function takes more arguments than the call was taking, add them
2564 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2565 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2567 // If we are removing arguments to the function, emit an obnoxious warning...
2568 if (FT->getNumParams() < NumActualArgs)
2569 if (!FT->isVarArg()) {
2570 std::cerr << "WARNING: While resolving call to function '"
2571 << Callee->getName() << "' arguments were dropped!\n";
2573 // Add all of the arguments in their promoted form to the arg list...
2574 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2575 const Type *PTy = getPromotedType((*AI)->getType());
2576 if (PTy != (*AI)->getType()) {
2577 // Must promote to pass through va_arg area!
2578 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2579 InsertNewInstBefore(Cast, *Caller);
2580 Args.push_back(Cast);
2582 Args.push_back(*AI);
2587 if (FT->getReturnType() == Type::VoidTy)
2588 Caller->setName(""); // Void type should not have a name...
2591 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2592 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2593 Args, Caller->getName(), Caller);
2595 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2598 // Insert a cast of the return type as necessary...
2600 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2601 if (NV->getType() != Type::VoidTy) {
2602 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2604 // If this is an invoke instruction, we should insert it after the first
2605 // non-phi, instruction in the normal successor block.
2606 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2607 BasicBlock::iterator I = II->getNormalDest()->begin();
2608 while (isa<PHINode>(I)) ++I;
2609 InsertNewInstBefore(NC, *I);
2611 // Otherwise, it's a call, just insert cast right after the call instr
2612 InsertNewInstBefore(NC, *Caller);
2614 AddUsersToWorkList(*Caller);
2616 NV = Constant::getNullValue(Caller->getType());
2620 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2621 Caller->replaceAllUsesWith(NV);
2622 Caller->getParent()->getInstList().erase(Caller);
2623 removeFromWorkList(Caller);
2629 // PHINode simplification
2631 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2632 if (Value *V = hasConstantValue(&PN))
2633 return ReplaceInstUsesWith(PN, V);
2635 // If the only user of this instruction is a cast instruction, and all of the
2636 // incoming values are constants, change this PHI to merge together the casted
2639 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2640 if (CI->getType() != PN.getType()) { // noop casts will be folded
2641 bool AllConstant = true;
2642 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2643 if (!isa<Constant>(PN.getIncomingValue(i))) {
2644 AllConstant = false;
2648 // Make a new PHI with all casted values.
2649 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2650 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2651 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2652 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2653 PN.getIncomingBlock(i));
2656 // Update the cast instruction.
2657 CI->setOperand(0, New);
2658 WorkList.push_back(CI); // revisit the cast instruction to fold.
2659 WorkList.push_back(New); // Make sure to revisit the new Phi
2660 return &PN; // PN is now dead!
2666 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
2667 Instruction *InsertPoint,
2669 unsigned PS = IC->getTargetData().getPointerSize();
2670 const Type *VTy = V->getType();
2672 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
2673 // We must insert a cast to ensure we sign-extend.
2674 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
2675 V->getName()), *InsertPoint);
2676 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
2681 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2682 Value *PtrOp = GEP.getOperand(0);
2683 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2684 // If so, eliminate the noop.
2685 if (GEP.getNumOperands() == 1)
2686 return ReplaceInstUsesWith(GEP, PtrOp);
2688 bool HasZeroPointerIndex = false;
2689 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2690 HasZeroPointerIndex = C->isNullValue();
2692 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2693 return ReplaceInstUsesWith(GEP, PtrOp);
2695 // Eliminate unneeded casts for indices.
2696 bool MadeChange = false;
2697 gep_type_iterator GTI = gep_type_begin(GEP);
2698 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
2699 if (isa<SequentialType>(*GTI)) {
2700 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
2701 Value *Src = CI->getOperand(0);
2702 const Type *SrcTy = Src->getType();
2703 const Type *DestTy = CI->getType();
2704 if (Src->getType()->isInteger()) {
2705 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
2706 // We can always eliminate a cast from ulong or long to the other.
2707 // We can always eliminate a cast from uint to int or the other on
2708 // 32-bit pointer platforms.
2709 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
2711 GEP.setOperand(i, Src);
2713 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2714 SrcTy->getPrimitiveSize() == 4) {
2715 // We can always eliminate a cast from int to [u]long. We can
2716 // eliminate a cast from uint to [u]long iff the target is a 32-bit
2718 if (SrcTy->isSigned() ||
2719 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
2721 GEP.setOperand(i, Src);
2726 // If we are using a wider index than needed for this platform, shrink it
2727 // to what we need. If the incoming value needs a cast instruction,
2728 // insert it. This explicit cast can make subsequent optimizations more
2730 Value *Op = GEP.getOperand(i);
2731 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
2732 if (Constant *C = dyn_cast<Constant>(Op)) {
2733 GEP.setOperand(i, ConstantExpr::getCast(C,
2734 TD->getIntPtrType()->getSignedVersion()));
2737 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
2738 Op->getName()), GEP);
2739 GEP.setOperand(i, Op);
2743 // If this is a constant idx, make sure to canonicalize it to be a signed
2744 // operand, otherwise CSE and other optimizations are pessimized.
2745 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op)) {
2746 GEP.setOperand(i, ConstantExpr::getCast(CUI,
2747 CUI->getType()->getSignedVersion()));
2751 if (MadeChange) return &GEP;
2753 // Combine Indices - If the source pointer to this getelementptr instruction
2754 // is a getelementptr instruction, combine the indices of the two
2755 // getelementptr instructions into a single instruction.
2757 std::vector<Value*> SrcGEPOperands;
2758 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(PtrOp)) {
2759 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2760 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
2761 if (CE->getOpcode() == Instruction::GetElementPtr)
2762 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2765 if (!SrcGEPOperands.empty()) {
2766 // Note that if our source is a gep chain itself that we wait for that
2767 // chain to be resolved before we perform this transformation. This
2768 // avoids us creating a TON of code in some cases.
2770 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2771 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2772 return 0; // Wait until our source is folded to completion.
2774 std::vector<Value *> Indices;
2776 // Find out whether the last index in the source GEP is a sequential idx.
2777 bool EndsWithSequential = false;
2778 for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
2779 E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
2780 EndsWithSequential = !isa<StructType>(*I);
2782 // Can we combine the two pointer arithmetics offsets?
2783 if (EndsWithSequential) {
2784 // Replace: gep (gep %P, long B), long A, ...
2785 // With: T = long A+B; gep %P, T, ...
2787 Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
2788 if (SO1 == Constant::getNullValue(SO1->getType())) {
2790 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
2793 // If they aren't the same type, convert both to an integer of the
2794 // target's pointer size.
2795 if (SO1->getType() != GO1->getType()) {
2796 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
2797 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
2798 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
2799 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
2801 unsigned PS = TD->getPointerSize();
2803 if (SO1->getType()->getPrimitiveSize() == PS) {
2804 // Convert GO1 to SO1's type.
2805 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
2807 } else if (GO1->getType()->getPrimitiveSize() == PS) {
2808 // Convert SO1 to GO1's type.
2809 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
2811 const Type *PT = TD->getIntPtrType();
2812 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
2813 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
2817 if (isa<Constant>(SO1) && isa<Constant>(GO1))
2818 Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
2820 Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
2821 InsertNewInstBefore(cast<Instruction>(Sum), GEP);
2825 // Recycle the GEP we already have if possible.
2826 if (SrcGEPOperands.size() == 2) {
2827 GEP.setOperand(0, SrcGEPOperands[0]);
2828 GEP.setOperand(1, Sum);
2831 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2832 SrcGEPOperands.end()-1);
2833 Indices.push_back(Sum);
2834 Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
2836 } else if (isa<Constant>(*GEP.idx_begin()) &&
2837 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
2838 SrcGEPOperands.size() != 1) {
2839 // Otherwise we can do the fold if the first index of the GEP is a zero
2840 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2841 SrcGEPOperands.end());
2842 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2845 if (!Indices.empty())
2846 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2848 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
2849 // GEP of global variable. If all of the indices for this GEP are
2850 // constants, we can promote this to a constexpr instead of an instruction.
2852 // Scan for nonconstants...
2853 std::vector<Constant*> Indices;
2854 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2855 for (; I != E && isa<Constant>(*I); ++I)
2856 Indices.push_back(cast<Constant>(*I));
2858 if (I == E) { // If they are all constants...
2859 Constant *CE = ConstantExpr::getGetElementPtr(GV, Indices);
2861 // Replace all uses of the GEP with the new constexpr...
2862 return ReplaceInstUsesWith(GEP, CE);
2864 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
2865 if (CE->getOpcode() == Instruction::Cast) {
2866 if (HasZeroPointerIndex) {
2867 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2868 // into : GEP [10 x ubyte]* X, long 0, ...
2870 // This occurs when the program declares an array extern like "int X[];"
2872 Constant *X = CE->getOperand(0);
2873 const PointerType *CPTy = cast<PointerType>(CE->getType());
2874 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2875 if (const ArrayType *XATy =
2876 dyn_cast<ArrayType>(XTy->getElementType()))
2877 if (const ArrayType *CATy =
2878 dyn_cast<ArrayType>(CPTy->getElementType()))
2879 if (CATy->getElementType() == XATy->getElementType()) {
2880 // At this point, we know that the cast source type is a pointer
2881 // to an array of the same type as the destination pointer
2882 // array. Because the array type is never stepped over (there
2883 // is a leading zero) we can fold the cast into this GEP.
2884 GEP.setOperand(0, X);
2894 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2895 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2896 if (AI.isArrayAllocation()) // Check C != 1
2897 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2898 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2899 AllocationInst *New = 0;
2901 // Create and insert the replacement instruction...
2902 if (isa<MallocInst>(AI))
2903 New = new MallocInst(NewTy, 0, AI.getName());
2905 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2906 New = new AllocaInst(NewTy, 0, AI.getName());
2909 InsertNewInstBefore(New, AI);
2911 // Scan to the end of the allocation instructions, to skip over a block of
2912 // allocas if possible...
2914 BasicBlock::iterator It = New;
2915 while (isa<AllocationInst>(*It)) ++It;
2917 // Now that I is pointing to the first non-allocation-inst in the block,
2918 // insert our getelementptr instruction...
2920 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
2921 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2923 // Now make everything use the getelementptr instead of the original
2925 return ReplaceInstUsesWith(AI, V);
2928 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2929 // Note that we only do this for alloca's, because malloc should allocate and
2930 // return a unique pointer, even for a zero byte allocation.
2931 if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
2932 TD->getTypeSize(AI.getAllocatedType()) == 0)
2933 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2938 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2939 Value *Op = FI.getOperand(0);
2941 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2942 if (CastInst *CI = dyn_cast<CastInst>(Op))
2943 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2944 FI.setOperand(0, CI->getOperand(0));
2948 // If we have 'free null' delete the instruction. This can happen in stl code
2949 // when lots of inlining happens.
2950 if (isa<ConstantPointerNull>(Op))
2951 return EraseInstFromFunction(FI);
2957 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2958 /// constantexpr, return the constant value being addressed by the constant
2959 /// expression, or null if something is funny.
2961 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2962 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
2963 return 0; // Do not allow stepping over the value!
2965 // Loop over all of the operands, tracking down which value we are
2967 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2968 for (++I; I != E; ++I)
2969 if (const StructType *STy = dyn_cast<StructType>(*I)) {
2970 ConstantUInt *CU = cast<ConstantUInt>(I.getOperand());
2971 assert(CU->getValue() < STy->getNumElements() &&
2972 "Struct index out of range!");
2973 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
2974 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2975 } else if (isa<ConstantAggregateZero>(C)) {
2976 C = Constant::getNullValue(STy->getElementType(CU->getValue()));
2980 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
2981 const ArrayType *ATy = cast<ArrayType>(*I);
2982 if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0;
2983 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
2984 C = cast<Constant>(CA->getValues()[CI->getRawValue()]);
2985 else if (isa<ConstantAggregateZero>(C))
2986 C = Constant::getNullValue(ATy->getElementType());
2995 static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
2996 User *CI = cast<User>(LI.getOperand(0));
2998 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
2999 if (const PointerType *SrcTy =
3000 dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
3001 const Type *SrcPTy = SrcTy->getElementType();
3002 if (SrcPTy->isSized() && DestPTy->isSized() &&
3003 IC.getTargetData().getTypeSize(SrcPTy) ==
3004 IC.getTargetData().getTypeSize(DestPTy) &&
3005 (SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
3006 (DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
3007 // Okay, we are casting from one integer or pointer type to another of
3008 // the same size. Instead of casting the pointer before the load, cast
3009 // the result of the loaded value.
3010 Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CI->getOperand(0),
3011 CI->getName()), LI);
3012 // Now cast the result of the load.
3013 return new CastInst(NewLoad, LI.getType());
3019 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
3020 Value *Op = LI.getOperand(0);
3021 if (LI.isVolatile()) return 0;
3023 if (Constant *C = dyn_cast<Constant>(Op))
3024 if (C->isNullValue()) // load null -> 0
3025 return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
3027 // Instcombine load (constant global) into the value loaded...
3028 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
3029 if (GV->isConstant() && !GV->isExternal())
3030 return ReplaceInstUsesWith(LI, GV->getInitializer());
3032 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
3033 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
3034 if (CE->getOpcode() == Instruction::GetElementPtr) {
3035 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
3036 if (GV->isConstant() && !GV->isExternal())
3037 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
3038 return ReplaceInstUsesWith(LI, V);
3039 } else if (CE->getOpcode() == Instruction::Cast) {
3040 if (Instruction *Res = InstCombineLoadCast(*this, LI))
3044 // load (cast X) --> cast (load X) iff safe
3045 if (CastInst *CI = dyn_cast<CastInst>(Op))
3046 if (Instruction *Res = InstCombineLoadCast(*this, LI))
3053 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
3054 // Change br (not X), label True, label False to: br X, label False, True
3055 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
3056 if (Value *V = dyn_castNotVal(BI.getCondition())) {
3057 BasicBlock *TrueDest = BI.getSuccessor(0);
3058 BasicBlock *FalseDest = BI.getSuccessor(1);
3059 // Swap Destinations and condition...
3061 BI.setSuccessor(0, FalseDest);
3062 BI.setSuccessor(1, TrueDest);
3064 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
3065 // Cannonicalize setne -> seteq
3066 if ((I->getOpcode() == Instruction::SetNE ||
3067 I->getOpcode() == Instruction::SetLE ||
3068 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
3069 std::string Name = I->getName(); I->setName("");
3070 Instruction::BinaryOps NewOpcode =
3071 SetCondInst::getInverseCondition(I->getOpcode());
3072 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
3073 I->getOperand(1), Name, I);
3074 BasicBlock *TrueDest = BI.getSuccessor(0);
3075 BasicBlock *FalseDest = BI.getSuccessor(1);
3076 // Swap Destinations and condition...
3077 BI.setCondition(NewSCC);
3078 BI.setSuccessor(0, FalseDest);
3079 BI.setSuccessor(1, TrueDest);
3080 removeFromWorkList(I);
3081 I->getParent()->getInstList().erase(I);
3082 WorkList.push_back(cast<Instruction>(NewSCC));
3090 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
3091 Value *Cond = SI.getCondition();
3092 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
3093 if (I->getOpcode() == Instruction::Add)
3094 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
3095 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
3096 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
3097 SI.setOperand(i, ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
3099 SI.setOperand(0, I->getOperand(0));
3100 WorkList.push_back(I);
3108 void InstCombiner::removeFromWorkList(Instruction *I) {
3109 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
3113 bool InstCombiner::runOnFunction(Function &F) {
3114 bool Changed = false;
3115 TD = &getAnalysis<TargetData>();
3117 for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
3118 WorkList.push_back(&*i);
3121 while (!WorkList.empty()) {
3122 Instruction *I = WorkList.back(); // Get an instruction from the worklist
3123 WorkList.pop_back();
3125 // Check to see if we can DCE or ConstantPropagate the instruction...
3126 // Check to see if we can DIE the instruction...
3127 if (isInstructionTriviallyDead(I)) {
3128 // Add operands to the worklist...
3129 if (I->getNumOperands() < 4)
3130 AddUsesToWorkList(*I);
3133 I->getParent()->getInstList().erase(I);
3134 removeFromWorkList(I);
3138 // Instruction isn't dead, see if we can constant propagate it...
3139 if (Constant *C = ConstantFoldInstruction(I)) {
3140 // Add operands to the worklist...
3141 AddUsesToWorkList(*I);
3142 ReplaceInstUsesWith(*I, C);
3145 I->getParent()->getInstList().erase(I);
3146 removeFromWorkList(I);
3150 // Now that we have an instruction, try combining it to simplify it...
3151 if (Instruction *Result = visit(*I)) {
3153 // Should we replace the old instruction with a new one?
3155 DEBUG(std::cerr << "IC: Old = " << *I
3156 << " New = " << *Result);
3158 // Everything uses the new instruction now.
3159 I->replaceAllUsesWith(Result);
3161 // Push the new instruction and any users onto the worklist.
3162 WorkList.push_back(Result);
3163 AddUsersToWorkList(*Result);
3165 // Move the name to the new instruction first...
3166 std::string OldName = I->getName(); I->setName("");
3167 Result->setName(OldName);
3169 // Insert the new instruction into the basic block...
3170 BasicBlock *InstParent = I->getParent();
3171 InstParent->getInstList().insert(I, Result);
3173 // Make sure that we reprocess all operands now that we reduced their
3175 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
3176 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
3177 WorkList.push_back(OpI);
3179 // Instructions can end up on the worklist more than once. Make sure
3180 // we do not process an instruction that has been deleted.
3181 removeFromWorkList(I);
3183 // Erase the old instruction.
3184 InstParent->getInstList().erase(I);
3186 DEBUG(std::cerr << "IC: MOD = " << *I);
3188 // If the instruction was modified, it's possible that it is now dead.
3189 // if so, remove it.
3190 if (isInstructionTriviallyDead(I)) {
3191 // Make sure we process all operands now that we are reducing their
3193 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
3194 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
3195 WorkList.push_back(OpI);
3197 // Instructions may end up in the worklist more than once. Erase all
3198 // occurrances of this instruction.
3199 removeFromWorkList(I);
3200 I->getParent()->getInstList().erase(I);
3202 WorkList.push_back(Result);
3203 AddUsersToWorkList(*Result);
3213 Pass *llvm::createInstructionCombiningPass() {
3214 return new InstCombiner();