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))) {
1459 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
1460 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
1461 // happens a LOT in code produced by the C front-end, for bitfield
1463 if (LHSI->getOperand(0)->hasOneUse())
1464 if (ShiftInst *Shift = dyn_cast<ShiftInst>(LHSI->getOperand(0)))
1465 if (ConstantUInt *ShAmt =
1466 dyn_cast<ConstantUInt>(Shift->getOperand(1))) {
1467 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
1469 // We can fold this as long as we can't shift unknown bits
1470 // into the mask. This can only happen with signed shift
1471 // rights, as they sign-extend.
1472 const Type *Ty = Shift->getType();
1473 if (Shift->getOpcode() != Instruction::Shr ||
1474 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 ConstantExpr::getAnd(ConstantExpr::getShl(ConstantInt::getAllOnesValue(Ty), ConstantUInt::get(Type::UByteTy, Ty->getPrimitiveSize()*8-ShAmt->getValue())), AndCST)->isNullValue()) {
1478 unsigned ShiftOp = Shift->getOpcode() == Instruction::Shl
1479 ? Instruction::Shr : Instruction::Shl;
1480 I.setOperand(1, ConstantExpr::get(ShiftOp, CI, ShAmt));
1481 LHSI->setOperand(1,ConstantExpr::get(ShiftOp,AndCST,ShAmt));
1482 LHSI->setOperand(0, Shift->getOperand(0));
1483 WorkList.push_back(Shift); // Shift is probably dead.
1484 AddUsesToWorkList(I);
1490 case Instruction::Div:
1491 if (0 && isa<ConstantInt>(LHSI->getOperand(1))) {
1492 std::cerr << "COULD FOLD: " << *LHSI;
1493 std::cerr << "COULD FOLD: " << I << "\n";
1496 case Instruction::Select:
1497 // If either operand of the select is a constant, we can fold the
1498 // comparison into the select arms, which will cause one to be
1499 // constant folded and the select turned into a bitwise or.
1500 Value *Op1 = 0, *Op2 = 0;
1501 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
1502 // Fold the known value into the constant operand.
1503 Op1 = ConstantExpr::get(I.getOpcode(), C, CI);
1504 // Insert a new SetCC of the other select operand.
1505 Op2 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
1506 LHSI->getOperand(2), CI,
1508 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
1509 // Fold the known value into the constant operand.
1510 Op2 = ConstantExpr::get(I.getOpcode(), C, CI);
1511 // Insert a new SetCC of the other select operand.
1512 Op1 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
1513 LHSI->getOperand(1), CI,
1518 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
1522 // Simplify seteq and setne instructions...
1523 if (I.getOpcode() == Instruction::SetEQ ||
1524 I.getOpcode() == Instruction::SetNE) {
1525 bool isSetNE = I.getOpcode() == Instruction::SetNE;
1527 // If the first operand is (and|or|xor) with a constant, and the second
1528 // operand is a constant, simplify a bit.
1529 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
1530 switch (BO->getOpcode()) {
1531 case Instruction::Rem:
1532 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
1533 if (CI->isNullValue() && isa<ConstantSInt>(BO->getOperand(1)) &&
1535 cast<ConstantSInt>(BO->getOperand(1))->getValue() > 1)
1537 Log2(cast<ConstantSInt>(BO->getOperand(1))->getValue())) {
1538 const Type *UTy = BO->getType()->getUnsignedVersion();
1539 Value *NewX = InsertNewInstBefore(new CastInst(BO->getOperand(0),
1541 Constant *RHSCst = ConstantUInt::get(UTy, 1ULL << L2);
1542 Value *NewRem =InsertNewInstBefore(BinaryOperator::createRem(NewX,
1543 RHSCst, BO->getName()), I);
1544 return BinaryOperator::create(I.getOpcode(), NewRem,
1545 Constant::getNullValue(UTy));
1549 case Instruction::Add:
1550 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
1551 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1552 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1553 ConstantExpr::getSub(CI, BOp1C));
1554 } else if (CI->isNullValue()) {
1555 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1556 // efficiently invertible, or if the add has just this one use.
1557 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1559 if (Value *NegVal = dyn_castNegVal(BOp1))
1560 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
1561 else if (Value *NegVal = dyn_castNegVal(BOp0))
1562 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
1563 else if (BO->hasOneUse()) {
1564 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
1566 InsertNewInstBefore(Neg, I);
1567 return new SetCondInst(I.getOpcode(), BOp0, Neg);
1571 case Instruction::Xor:
1572 // For the xor case, we can xor two constants together, eliminating
1573 // the explicit xor.
1574 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
1575 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
1576 ConstantExpr::getXor(CI, BOC));
1579 case Instruction::Sub:
1580 // Replace (([sub|xor] A, B) != 0) with (A != B)
1581 if (CI->isNullValue())
1582 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
1586 case Instruction::Or:
1587 // If bits are being or'd in that are not present in the constant we
1588 // are comparing against, then the comparison could never succeed!
1589 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1590 Constant *NotCI = ConstantExpr::getNot(CI);
1591 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
1592 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1596 case Instruction::And:
1597 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1598 // If bits are being compared against that are and'd out, then the
1599 // comparison can never succeed!
1600 if (!ConstantExpr::getAnd(CI,
1601 ConstantExpr::getNot(BOC))->isNullValue())
1602 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
1604 // If we have ((X & C) == C), turn it into ((X & C) != 0).
1605 if (CI == BOC && isOneBitSet(CI))
1606 return new SetCondInst(isSetNE ? Instruction::SetEQ :
1607 Instruction::SetNE, Op0,
1608 Constant::getNullValue(CI->getType()));
1610 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
1611 // to be a signed value as appropriate.
1612 if (isSignBit(BOC)) {
1613 Value *X = BO->getOperand(0);
1614 // If 'X' is not signed, insert a cast now...
1615 if (!BOC->getType()->isSigned()) {
1616 const Type *DestTy = BOC->getType()->getSignedVersion();
1617 CastInst *NewCI = new CastInst(X,DestTy,X->getName()+".signed");
1618 InsertNewInstBefore(NewCI, I);
1621 return new SetCondInst(isSetNE ? Instruction::SetLT :
1622 Instruction::SetGE, X,
1623 Constant::getNullValue(X->getType()));
1629 } else { // Not a SetEQ/SetNE
1630 // If the LHS is a cast from an integral value of the same size,
1631 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
1632 Value *CastOp = Cast->getOperand(0);
1633 const Type *SrcTy = CastOp->getType();
1634 unsigned SrcTySize = SrcTy->getPrimitiveSize();
1635 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
1636 SrcTySize == Cast->getType()->getPrimitiveSize()) {
1637 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
1638 "Source and destination signednesses should differ!");
1639 if (Cast->getType()->isSigned()) {
1640 // If this is a signed comparison, check for comparisons in the
1641 // vicinity of zero.
1642 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
1644 return BinaryOperator::createSetGT(CastOp,
1645 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize*8-1))-1));
1646 else if (I.getOpcode() == Instruction::SetGT &&
1647 cast<ConstantSInt>(CI)->getValue() == -1)
1648 // X > -1 => x < 128
1649 return BinaryOperator::createSetLT(CastOp,
1650 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize*8-1)));
1652 ConstantUInt *CUI = cast<ConstantUInt>(CI);
1653 if (I.getOpcode() == Instruction::SetLT &&
1654 CUI->getValue() == 1ULL << (SrcTySize*8-1))
1655 // X < 128 => X > -1
1656 return BinaryOperator::createSetGT(CastOp,
1657 ConstantSInt::get(SrcTy, -1));
1658 else if (I.getOpcode() == Instruction::SetGT &&
1659 CUI->getValue() == (1ULL << (SrcTySize*8-1))-1)
1661 return BinaryOperator::createSetLT(CastOp,
1662 Constant::getNullValue(SrcTy));
1668 // Check to see if we are comparing against the minimum or maximum value...
1669 if (CI->isMinValue()) {
1670 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
1671 return ReplaceInstUsesWith(I, ConstantBool::False);
1672 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
1673 return ReplaceInstUsesWith(I, ConstantBool::True);
1674 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
1675 return BinaryOperator::createSetEQ(Op0, Op1);
1676 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
1677 return BinaryOperator::createSetNE(Op0, Op1);
1679 } else if (CI->isMaxValue()) {
1680 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
1681 return ReplaceInstUsesWith(I, ConstantBool::False);
1682 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
1683 return ReplaceInstUsesWith(I, ConstantBool::True);
1684 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
1685 return BinaryOperator::createSetEQ(Op0, Op1);
1686 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
1687 return BinaryOperator::createSetNE(Op0, Op1);
1689 // Comparing against a value really close to min or max?
1690 } else if (isMinValuePlusOne(CI)) {
1691 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
1692 return BinaryOperator::createSetEQ(Op0, SubOne(CI));
1693 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
1694 return BinaryOperator::createSetNE(Op0, SubOne(CI));
1696 } else if (isMaxValueMinusOne(CI)) {
1697 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
1698 return BinaryOperator::createSetEQ(Op0, AddOne(CI));
1699 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
1700 return BinaryOperator::createSetNE(Op0, AddOne(CI));
1703 // If we still have a setle or setge instruction, turn it into the
1704 // appropriate setlt or setgt instruction. Since the border cases have
1705 // already been handled above, this requires little checking.
1707 if (I.getOpcode() == Instruction::SetLE)
1708 return BinaryOperator::createSetLT(Op0, AddOne(CI));
1709 if (I.getOpcode() == Instruction::SetGE)
1710 return BinaryOperator::createSetGT(Op0, SubOne(CI));
1713 // Test to see if the operands of the setcc are casted versions of other
1714 // values. If the cast can be stripped off both arguments, we do so now.
1715 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1716 Value *CastOp0 = CI->getOperand(0);
1717 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
1718 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
1719 (I.getOpcode() == Instruction::SetEQ ||
1720 I.getOpcode() == Instruction::SetNE)) {
1721 // We keep moving the cast from the left operand over to the right
1722 // operand, where it can often be eliminated completely.
1725 // If operand #1 is a cast instruction, see if we can eliminate it as
1727 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
1728 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
1730 Op1 = CI2->getOperand(0);
1732 // If Op1 is a constant, we can fold the cast into the constant.
1733 if (Op1->getType() != Op0->getType())
1734 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1735 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
1737 // Otherwise, cast the RHS right before the setcc
1738 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
1739 InsertNewInstBefore(cast<Instruction>(Op1), I);
1741 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
1744 // Handle the special case of: setcc (cast bool to X), <cst>
1745 // This comes up when you have code like
1748 // For generality, we handle any zero-extension of any operand comparison
1750 if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
1751 const Type *SrcTy = CastOp0->getType();
1752 const Type *DestTy = Op0->getType();
1753 if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
1754 (SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
1755 // Ok, we have an expansion of operand 0 into a new type. Get the
1756 // constant value, masink off bits which are not set in the RHS. These
1757 // could be set if the destination value is signed.
1758 uint64_t ConstVal = ConstantRHS->getRawValue();
1759 ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
1761 // If the constant we are comparing it with has high bits set, which
1762 // don't exist in the original value, the values could never be equal,
1763 // because the source would be zero extended.
1765 SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
1766 bool HasSignBit = ConstVal & (1ULL << (DestTy->getPrimitiveSize()*8-1));
1767 if (ConstVal & ~((1ULL << SrcBits)-1)) {
1768 switch (I.getOpcode()) {
1769 default: assert(0 && "Unknown comparison type!");
1770 case Instruction::SetEQ:
1771 return ReplaceInstUsesWith(I, ConstantBool::False);
1772 case Instruction::SetNE:
1773 return ReplaceInstUsesWith(I, ConstantBool::True);
1774 case Instruction::SetLT:
1775 case Instruction::SetLE:
1776 if (DestTy->isSigned() && HasSignBit)
1777 return ReplaceInstUsesWith(I, ConstantBool::False);
1778 return ReplaceInstUsesWith(I, ConstantBool::True);
1779 case Instruction::SetGT:
1780 case Instruction::SetGE:
1781 if (DestTy->isSigned() && HasSignBit)
1782 return ReplaceInstUsesWith(I, ConstantBool::True);
1783 return ReplaceInstUsesWith(I, ConstantBool::False);
1787 // Otherwise, we can replace the setcc with a setcc of the smaller
1789 Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
1790 return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
1794 return Changed ? &I : 0;
1799 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
1800 assert(I.getOperand(1)->getType() == Type::UByteTy);
1801 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1802 bool isLeftShift = I.getOpcode() == Instruction::Shl;
1804 // shl X, 0 == X and shr X, 0 == X
1805 // shl 0, X == 0 and shr 0, X == 0
1806 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
1807 Op0 == Constant::getNullValue(Op0->getType()))
1808 return ReplaceInstUsesWith(I, Op0);
1810 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
1812 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
1813 if (CSI->isAllOnesValue())
1814 return ReplaceInstUsesWith(I, CSI);
1816 // Try to fold constant and into select arguments.
1817 if (isa<Constant>(Op0))
1818 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1819 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1822 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
1823 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
1824 // of a signed value.
1826 unsigned TypeBits = Op0->getType()->getPrimitiveSize()*8;
1827 if (CUI->getValue() >= TypeBits) {
1828 if (!Op0->getType()->isSigned() || isLeftShift)
1829 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
1831 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
1836 // ((X*C1) << C2) == (X * (C1 << C2))
1837 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
1838 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
1839 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
1840 return BinaryOperator::createMul(BO->getOperand(0),
1841 ConstantExpr::getShl(BOOp, CUI));
1843 // Try to fold constant and into select arguments.
1844 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1845 if (Instruction *R = FoldBinOpIntoSelect(I, SI, this))
1848 // If the operand is an bitwise operator with a constant RHS, and the
1849 // shift is the only use, we can pull it out of the shift.
1850 if (Op0->hasOneUse())
1851 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
1852 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
1853 bool isValid = true; // Valid only for And, Or, Xor
1854 bool highBitSet = false; // Transform if high bit of constant set?
1856 switch (Op0BO->getOpcode()) {
1857 default: isValid = false; break; // Do not perform transform!
1858 case Instruction::Or:
1859 case Instruction::Xor:
1862 case Instruction::And:
1867 // If this is a signed shift right, and the high bit is modified
1868 // by the logical operation, do not perform the transformation.
1869 // The highBitSet boolean indicates the value of the high bit of
1870 // the constant which would cause it to be modified for this
1873 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
1874 uint64_t Val = Op0C->getRawValue();
1875 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
1879 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
1881 Instruction *NewShift =
1882 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
1885 InsertNewInstBefore(NewShift, I);
1887 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
1892 // If this is a shift of a shift, see if we can fold the two together...
1893 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
1894 if (ConstantUInt *ShiftAmt1C =
1895 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
1896 unsigned ShiftAmt1 = ShiftAmt1C->getValue();
1897 unsigned ShiftAmt2 = CUI->getValue();
1899 // Check for (A << c1) << c2 and (A >> c1) >> c2
1900 if (I.getOpcode() == Op0SI->getOpcode()) {
1901 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
1902 if (Op0->getType()->getPrimitiveSize()*8 < Amt)
1903 Amt = Op0->getType()->getPrimitiveSize()*8;
1904 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
1905 ConstantUInt::get(Type::UByteTy, Amt));
1908 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
1909 // signed types, we can only support the (A >> c1) << c2 configuration,
1910 // because it can not turn an arbitrary bit of A into a sign bit.
1911 if (I.getType()->isUnsigned() || isLeftShift) {
1912 // Calculate bitmask for what gets shifted off the edge...
1913 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
1915 C = ConstantExpr::getShl(C, ShiftAmt1C);
1917 C = ConstantExpr::getShr(C, ShiftAmt1C);
1920 BinaryOperator::createAnd(Op0SI->getOperand(0), C,
1921 Op0SI->getOperand(0)->getName()+".mask");
1922 InsertNewInstBefore(Mask, I);
1924 // Figure out what flavor of shift we should use...
1925 if (ShiftAmt1 == ShiftAmt2)
1926 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
1927 else if (ShiftAmt1 < ShiftAmt2) {
1928 return new ShiftInst(I.getOpcode(), Mask,
1929 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
1931 return new ShiftInst(Op0SI->getOpcode(), Mask,
1932 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
1942 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
1945 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
1946 const Type *DstTy) {
1948 // It is legal to eliminate the instruction if casting A->B->A if the sizes
1949 // are identical and the bits don't get reinterpreted (for example
1950 // int->float->int would not be allowed)
1951 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
1954 // Allow free casting and conversion of sizes as long as the sign doesn't
1956 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
1957 unsigned SrcSize = SrcTy->getPrimitiveSize();
1958 unsigned MidSize = MidTy->getPrimitiveSize();
1959 unsigned DstSize = DstTy->getPrimitiveSize();
1961 // Cases where we are monotonically decreasing the size of the type are
1962 // always ok, regardless of what sign changes are going on.
1964 if (SrcSize >= MidSize && MidSize >= DstSize)
1967 // Cases where the source and destination type are the same, but the middle
1968 // type is bigger are noops.
1970 if (SrcSize == DstSize && MidSize > SrcSize)
1973 // If we are monotonically growing, things are more complex.
1975 if (SrcSize <= MidSize && MidSize <= DstSize) {
1976 // We have eight combinations of signedness to worry about. Here's the
1978 static const int SignTable[8] = {
1979 // CODE, SrcSigned, MidSigned, DstSigned, Comment
1980 1, // U U U Always ok
1981 1, // U U S Always ok
1982 3, // U S U Ok iff SrcSize != MidSize
1983 3, // U S S Ok iff SrcSize != MidSize
1984 0, // S U U Never ok
1985 2, // S U S Ok iff MidSize == DstSize
1986 1, // S S U Always ok
1987 1, // S S S Always ok
1990 // Choose an action based on the current entry of the signtable that this
1991 // cast of cast refers to...
1992 unsigned Row = SrcTy->isSigned()*4+MidTy->isSigned()*2+DstTy->isSigned();
1993 switch (SignTable[Row]) {
1994 case 0: return false; // Never ok
1995 case 1: return true; // Always ok
1996 case 2: return MidSize == DstSize; // Ok iff MidSize == DstSize
1997 case 3: // Ok iff SrcSize != MidSize
1998 return SrcSize != MidSize || SrcTy == Type::BoolTy;
1999 default: assert(0 && "Bad entry in sign table!");
2004 // Otherwise, we cannot succeed. Specifically we do not want to allow things
2005 // like: short -> ushort -> uint, because this can create wrong results if
2006 // the input short is negative!
2011 static bool ValueRequiresCast(const Value *V, const Type *Ty) {
2012 if (V->getType() == Ty || isa<Constant>(V)) return false;
2013 if (const CastInst *CI = dyn_cast<CastInst>(V))
2014 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty))
2019 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
2020 /// InsertBefore instruction. This is specialized a bit to avoid inserting
2021 /// casts that are known to not do anything...
2023 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
2024 Instruction *InsertBefore) {
2025 if (V->getType() == DestTy) return V;
2026 if (Constant *C = dyn_cast<Constant>(V))
2027 return ConstantExpr::getCast(C, DestTy);
2029 CastInst *CI = new CastInst(V, DestTy, V->getName());
2030 InsertNewInstBefore(CI, *InsertBefore);
2034 // CastInst simplification
2036 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
2037 Value *Src = CI.getOperand(0);
2039 // If the user is casting a value to the same type, eliminate this cast
2041 if (CI.getType() == Src->getType())
2042 return ReplaceInstUsesWith(CI, Src);
2044 // If casting the result of another cast instruction, try to eliminate this
2047 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) {
2048 if (isEliminableCastOfCast(CSrc->getOperand(0)->getType(),
2049 CSrc->getType(), CI.getType())) {
2050 // This instruction now refers directly to the cast's src operand. This
2051 // has a good chance of making CSrc dead.
2052 CI.setOperand(0, CSrc->getOperand(0));
2056 // If this is an A->B->A cast, and we are dealing with integral types, try
2057 // to convert this into a logical 'and' instruction.
2059 if (CSrc->getOperand(0)->getType() == CI.getType() &&
2060 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
2061 CI.getType()->isUnsigned() && CSrc->getType()->isUnsigned() &&
2062 CSrc->getType()->getPrimitiveSize() < CI.getType()->getPrimitiveSize()){
2063 assert(CSrc->getType() != Type::ULongTy &&
2064 "Cannot have type bigger than ulong!");
2065 uint64_t AndValue = (1ULL << CSrc->getType()->getPrimitiveSize()*8)-1;
2066 Constant *AndOp = ConstantUInt::get(CI.getType(), AndValue);
2067 return BinaryOperator::createAnd(CSrc->getOperand(0), AndOp);
2071 // If this is a cast to bool, turn it into the appropriate setne instruction.
2072 if (CI.getType() == Type::BoolTy)
2073 return BinaryOperator::createSetNE(CI.getOperand(0),
2074 Constant::getNullValue(CI.getOperand(0)->getType()));
2076 // If casting the result of a getelementptr instruction with no offset, turn
2077 // this into a cast of the original pointer!
2079 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
2080 bool AllZeroOperands = true;
2081 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2082 if (!isa<Constant>(GEP->getOperand(i)) ||
2083 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
2084 AllZeroOperands = false;
2087 if (AllZeroOperands) {
2088 CI.setOperand(0, GEP->getOperand(0));
2093 // If we are casting a malloc or alloca to a pointer to a type of the same
2094 // size, rewrite the allocation instruction to allocate the "right" type.
2096 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
2097 if (AI->hasOneUse() && !AI->isArrayAllocation())
2098 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
2099 // Get the type really allocated and the type casted to...
2100 const Type *AllocElTy = AI->getAllocatedType();
2101 const Type *CastElTy = PTy->getElementType();
2102 if (AllocElTy->isSized() && CastElTy->isSized()) {
2103 unsigned AllocElTySize = TD->getTypeSize(AllocElTy);
2104 unsigned CastElTySize = TD->getTypeSize(CastElTy);
2106 // If the allocation is for an even multiple of the cast type size
2107 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
2108 Value *Amt = ConstantUInt::get(Type::UIntTy,
2109 AllocElTySize/CastElTySize);
2110 std::string Name = AI->getName(); AI->setName("");
2111 AllocationInst *New;
2112 if (isa<MallocInst>(AI))
2113 New = new MallocInst(CastElTy, Amt, Name);
2115 New = new AllocaInst(CastElTy, Amt, Name);
2116 InsertNewInstBefore(New, *AI);
2117 return ReplaceInstUsesWith(CI, New);
2122 // If the source value is an instruction with only this use, we can attempt to
2123 // propagate the cast into the instruction. Also, only handle integral types
2125 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
2126 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
2127 CI.getType()->isInteger()) { // Don't mess with casts to bool here
2128 const Type *DestTy = CI.getType();
2129 unsigned SrcBitSize = getTypeSizeInBits(Src->getType());
2130 unsigned DestBitSize = getTypeSizeInBits(DestTy);
2132 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
2133 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
2135 switch (SrcI->getOpcode()) {
2136 case Instruction::Add:
2137 case Instruction::Mul:
2138 case Instruction::And:
2139 case Instruction::Or:
2140 case Instruction::Xor:
2141 // If we are discarding information, or just changing the sign, rewrite.
2142 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
2143 // Don't insert two casts if they cannot be eliminated. We allow two
2144 // casts to be inserted if the sizes are the same. This could only be
2145 // converting signedness, which is a noop.
2146 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy) ||
2147 !ValueRequiresCast(Op0, DestTy)) {
2148 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2149 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
2150 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
2151 ->getOpcode(), Op0c, Op1c);
2155 case Instruction::Shl:
2156 // Allow changing the sign of the source operand. Do not allow changing
2157 // the size of the shift, UNLESS the shift amount is a constant. We
2158 // mush not change variable sized shifts to a smaller size, because it
2159 // is undefined to shift more bits out than exist in the value.
2160 if (DestBitSize == SrcBitSize ||
2161 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
2162 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
2163 return new ShiftInst(Instruction::Shl, Op0c, Op1);
2172 /// GetSelectFoldableOperands - We want to turn code that looks like this:
2174 /// %D = select %cond, %C, %A
2176 /// %C = select %cond, %B, 0
2179 /// Assuming that the specified instruction is an operand to the select, return
2180 /// a bitmask indicating which operands of this instruction are foldable if they
2181 /// equal the other incoming value of the select.
2183 static unsigned GetSelectFoldableOperands(Instruction *I) {
2184 switch (I->getOpcode()) {
2185 case Instruction::Add:
2186 case Instruction::Mul:
2187 case Instruction::And:
2188 case Instruction::Or:
2189 case Instruction::Xor:
2190 return 3; // Can fold through either operand.
2191 case Instruction::Sub: // Can only fold on the amount subtracted.
2192 case Instruction::Shl: // Can only fold on the shift amount.
2193 case Instruction::Shr:
2196 return 0; // Cannot fold
2200 /// GetSelectFoldableConstant - For the same transformation as the previous
2201 /// function, return the identity constant that goes into the select.
2202 static Constant *GetSelectFoldableConstant(Instruction *I) {
2203 switch (I->getOpcode()) {
2204 default: assert(0 && "This cannot happen!"); abort();
2205 case Instruction::Add:
2206 case Instruction::Sub:
2207 case Instruction::Or:
2208 case Instruction::Xor:
2209 return Constant::getNullValue(I->getType());
2210 case Instruction::Shl:
2211 case Instruction::Shr:
2212 return Constant::getNullValue(Type::UByteTy);
2213 case Instruction::And:
2214 return ConstantInt::getAllOnesValue(I->getType());
2215 case Instruction::Mul:
2216 return ConstantInt::get(I->getType(), 1);
2220 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
2221 Value *CondVal = SI.getCondition();
2222 Value *TrueVal = SI.getTrueValue();
2223 Value *FalseVal = SI.getFalseValue();
2225 // select true, X, Y -> X
2226 // select false, X, Y -> Y
2227 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
2228 if (C == ConstantBool::True)
2229 return ReplaceInstUsesWith(SI, TrueVal);
2231 assert(C == ConstantBool::False);
2232 return ReplaceInstUsesWith(SI, FalseVal);
2235 // select C, X, X -> X
2236 if (TrueVal == FalseVal)
2237 return ReplaceInstUsesWith(SI, TrueVal);
2239 if (SI.getType() == Type::BoolTy)
2240 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
2241 if (C == ConstantBool::True) {
2242 // Change: A = select B, true, C --> A = or B, C
2243 return BinaryOperator::createOr(CondVal, FalseVal);
2245 // Change: A = select B, false, C --> A = and !B, C
2247 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2248 "not."+CondVal->getName()), SI);
2249 return BinaryOperator::createAnd(NotCond, FalseVal);
2251 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
2252 if (C == ConstantBool::False) {
2253 // Change: A = select B, C, false --> A = and B, C
2254 return BinaryOperator::createAnd(CondVal, TrueVal);
2256 // Change: A = select B, C, true --> A = or !B, C
2258 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2259 "not."+CondVal->getName()), SI);
2260 return BinaryOperator::createOr(NotCond, TrueVal);
2264 // Selecting between two integer constants?
2265 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
2266 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
2267 // select C, 1, 0 -> cast C to int
2268 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
2269 return new CastInst(CondVal, SI.getType());
2270 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
2271 // select C, 0, 1 -> cast !C to int
2273 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
2274 "not."+CondVal->getName()), SI);
2275 return new CastInst(NotCond, SI.getType());
2278 // If one of the constants is zero (we know they can't both be) and we
2279 // have a setcc instruction with zero, and we have an 'and' with the
2280 // non-constant value, eliminate this whole mess. This corresponds to
2281 // cases like this: ((X & 27) ? 27 : 0)
2282 if (TrueValC->isNullValue() || FalseValC->isNullValue())
2283 if (Instruction *IC = dyn_cast<Instruction>(SI.getCondition()))
2284 if ((IC->getOpcode() == Instruction::SetEQ ||
2285 IC->getOpcode() == Instruction::SetNE) &&
2286 isa<ConstantInt>(IC->getOperand(1)) &&
2287 cast<Constant>(IC->getOperand(1))->isNullValue())
2288 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
2289 if (ICA->getOpcode() == Instruction::And &&
2290 isa<ConstantInt>(ICA->getOperand(1)) &&
2291 (ICA->getOperand(1) == TrueValC ||
2292 ICA->getOperand(1) == FalseValC) &&
2293 isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
2294 // Okay, now we know that everything is set up, we just don't
2295 // know whether we have a setne or seteq and whether the true or
2296 // false val is the zero.
2297 bool ShouldNotVal = !TrueValC->isNullValue();
2298 ShouldNotVal ^= IC->getOpcode() == Instruction::SetNE;
2301 V = InsertNewInstBefore(BinaryOperator::create(
2302 Instruction::Xor, V, ICA->getOperand(1)), SI);
2303 return ReplaceInstUsesWith(SI, V);
2307 // See if we are selecting two values based on a comparison of the two values.
2308 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
2309 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
2310 // Transform (X == Y) ? X : Y -> Y
2311 if (SCI->getOpcode() == Instruction::SetEQ)
2312 return ReplaceInstUsesWith(SI, FalseVal);
2313 // Transform (X != Y) ? X : Y -> X
2314 if (SCI->getOpcode() == Instruction::SetNE)
2315 return ReplaceInstUsesWith(SI, TrueVal);
2316 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2318 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
2319 // Transform (X == Y) ? Y : X -> X
2320 if (SCI->getOpcode() == Instruction::SetEQ)
2321 return ReplaceInstUsesWith(SI, FalseVal);
2322 // Transform (X != Y) ? Y : X -> Y
2323 if (SCI->getOpcode() == Instruction::SetNE)
2324 return ReplaceInstUsesWith(SI, TrueVal);
2325 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
2329 // See if we can fold the select into one of our operands.
2330 if (SI.getType()->isInteger()) {
2331 // See the comment above GetSelectFoldableOperands for a description of the
2332 // transformation we are doing here.
2333 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
2334 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
2335 !isa<Constant>(FalseVal))
2336 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
2337 unsigned OpToFold = 0;
2338 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
2340 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
2345 Constant *C = GetSelectFoldableConstant(TVI);
2346 std::string Name = TVI->getName(); TVI->setName("");
2347 Instruction *NewSel =
2348 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
2350 InsertNewInstBefore(NewSel, SI);
2351 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
2352 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
2353 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
2354 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
2356 assert(0 && "Unknown instruction!!");
2361 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
2362 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
2363 !isa<Constant>(TrueVal))
2364 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
2365 unsigned OpToFold = 0;
2366 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
2368 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
2373 Constant *C = GetSelectFoldableConstant(FVI);
2374 std::string Name = FVI->getName(); FVI->setName("");
2375 Instruction *NewSel =
2376 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
2378 InsertNewInstBefore(NewSel, SI);
2379 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
2380 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
2381 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
2382 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
2384 assert(0 && "Unknown instruction!!");
2393 // CallInst simplification
2395 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
2396 // Intrinsics cannot occur in an invoke, so handle them here instead of in
2398 if (Function *F = CI.getCalledFunction())
2399 switch (F->getIntrinsicID()) {
2400 case Intrinsic::memmove:
2401 case Intrinsic::memcpy:
2402 case Intrinsic::memset:
2403 // memmove/cpy/set of zero bytes is a noop.
2404 if (Constant *NumBytes = dyn_cast<Constant>(CI.getOperand(3))) {
2405 if (NumBytes->isNullValue())
2406 return EraseInstFromFunction(CI);
2413 return visitCallSite(&CI);
2416 // InvokeInst simplification
2418 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
2419 return visitCallSite(&II);
2422 // visitCallSite - Improvements for call and invoke instructions.
2424 Instruction *InstCombiner::visitCallSite(CallSite CS) {
2425 bool Changed = false;
2427 // If the callee is a constexpr cast of a function, attempt to move the cast
2428 // to the arguments of the call/invoke.
2429 if (transformConstExprCastCall(CS)) return 0;
2431 Value *Callee = CS.getCalledValue();
2432 const PointerType *PTy = cast<PointerType>(Callee->getType());
2433 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
2434 if (FTy->isVarArg()) {
2435 // See if we can optimize any arguments passed through the varargs area of
2437 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
2438 E = CS.arg_end(); I != E; ++I)
2439 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
2440 // If this cast does not effect the value passed through the varargs
2441 // area, we can eliminate the use of the cast.
2442 Value *Op = CI->getOperand(0);
2443 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
2450 return Changed ? CS.getInstruction() : 0;
2453 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
2454 // attempt to move the cast to the arguments of the call/invoke.
2456 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
2457 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
2458 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
2459 if (CE->getOpcode() != Instruction::Cast ||
2460 !isa<ConstantPointerRef>(CE->getOperand(0)))
2462 ConstantPointerRef *CPR = cast<ConstantPointerRef>(CE->getOperand(0));
2463 if (!isa<Function>(CPR->getValue())) return false;
2464 Function *Callee = cast<Function>(CPR->getValue());
2465 Instruction *Caller = CS.getInstruction();
2467 // Okay, this is a cast from a function to a different type. Unless doing so
2468 // would cause a type conversion of one of our arguments, change this call to
2469 // be a direct call with arguments casted to the appropriate types.
2471 const FunctionType *FT = Callee->getFunctionType();
2472 const Type *OldRetTy = Caller->getType();
2474 // Check to see if we are changing the return type...
2475 if (OldRetTy != FT->getReturnType()) {
2476 if (Callee->isExternal() &&
2477 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
2478 !Caller->use_empty())
2479 return false; // Cannot transform this return value...
2481 // If the callsite is an invoke instruction, and the return value is used by
2482 // a PHI node in a successor, we cannot change the return type of the call
2483 // because there is no place to put the cast instruction (without breaking
2484 // the critical edge). Bail out in this case.
2485 if (!Caller->use_empty())
2486 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
2487 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
2489 if (PHINode *PN = dyn_cast<PHINode>(*UI))
2490 if (PN->getParent() == II->getNormalDest() ||
2491 PN->getParent() == II->getUnwindDest())
2495 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
2496 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
2498 CallSite::arg_iterator AI = CS.arg_begin();
2499 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
2500 const Type *ParamTy = FT->getParamType(i);
2501 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
2502 if (Callee->isExternal() && !isConvertible) return false;
2505 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
2506 Callee->isExternal())
2507 return false; // Do not delete arguments unless we have a function body...
2509 // Okay, we decided that this is a safe thing to do: go ahead and start
2510 // inserting cast instructions as necessary...
2511 std::vector<Value*> Args;
2512 Args.reserve(NumActualArgs);
2514 AI = CS.arg_begin();
2515 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
2516 const Type *ParamTy = FT->getParamType(i);
2517 if ((*AI)->getType() == ParamTy) {
2518 Args.push_back(*AI);
2520 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
2525 // If the function takes more arguments than the call was taking, add them
2527 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
2528 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
2530 // If we are removing arguments to the function, emit an obnoxious warning...
2531 if (FT->getNumParams() < NumActualArgs)
2532 if (!FT->isVarArg()) {
2533 std::cerr << "WARNING: While resolving call to function '"
2534 << Callee->getName() << "' arguments were dropped!\n";
2536 // Add all of the arguments in their promoted form to the arg list...
2537 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
2538 const Type *PTy = getPromotedType((*AI)->getType());
2539 if (PTy != (*AI)->getType()) {
2540 // Must promote to pass through va_arg area!
2541 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
2542 InsertNewInstBefore(Cast, *Caller);
2543 Args.push_back(Cast);
2545 Args.push_back(*AI);
2550 if (FT->getReturnType() == Type::VoidTy)
2551 Caller->setName(""); // Void type should not have a name...
2554 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2555 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
2556 Args, Caller->getName(), Caller);
2558 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
2561 // Insert a cast of the return type as necessary...
2563 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
2564 if (NV->getType() != Type::VoidTy) {
2565 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
2567 // If this is an invoke instruction, we should insert it after the first
2568 // non-phi, instruction in the normal successor block.
2569 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
2570 BasicBlock::iterator I = II->getNormalDest()->begin();
2571 while (isa<PHINode>(I)) ++I;
2572 InsertNewInstBefore(NC, *I);
2574 // Otherwise, it's a call, just insert cast right after the call instr
2575 InsertNewInstBefore(NC, *Caller);
2577 AddUsersToWorkList(*Caller);
2579 NV = Constant::getNullValue(Caller->getType());
2583 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
2584 Caller->replaceAllUsesWith(NV);
2585 Caller->getParent()->getInstList().erase(Caller);
2586 removeFromWorkList(Caller);
2592 // PHINode simplification
2594 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
2595 if (Value *V = hasConstantValue(&PN))
2596 return ReplaceInstUsesWith(PN, V);
2598 // If the only user of this instruction is a cast instruction, and all of the
2599 // incoming values are constants, change this PHI to merge together the casted
2602 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
2603 if (CI->getType() != PN.getType()) { // noop casts will be folded
2604 bool AllConstant = true;
2605 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
2606 if (!isa<Constant>(PN.getIncomingValue(i))) {
2607 AllConstant = false;
2611 // Make a new PHI with all casted values.
2612 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
2613 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
2614 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
2615 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
2616 PN.getIncomingBlock(i));
2619 // Update the cast instruction.
2620 CI->setOperand(0, New);
2621 WorkList.push_back(CI); // revisit the cast instruction to fold.
2622 WorkList.push_back(New); // Make sure to revisit the new Phi
2623 return &PN; // PN is now dead!
2629 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
2630 Instruction *InsertPoint,
2632 unsigned PS = IC->getTargetData().getPointerSize();
2633 const Type *VTy = V->getType();
2635 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
2636 // We must insert a cast to ensure we sign-extend.
2637 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
2638 V->getName()), *InsertPoint);
2639 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
2644 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
2645 Value *PtrOp = GEP.getOperand(0);
2646 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
2647 // If so, eliminate the noop.
2648 if (GEP.getNumOperands() == 1)
2649 return ReplaceInstUsesWith(GEP, PtrOp);
2651 bool HasZeroPointerIndex = false;
2652 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
2653 HasZeroPointerIndex = C->isNullValue();
2655 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
2656 return ReplaceInstUsesWith(GEP, PtrOp);
2658 // Eliminate unneeded casts for indices.
2659 bool MadeChange = false;
2660 gep_type_iterator GTI = gep_type_begin(GEP);
2661 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
2662 if (isa<SequentialType>(*GTI)) {
2663 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
2664 Value *Src = CI->getOperand(0);
2665 const Type *SrcTy = Src->getType();
2666 const Type *DestTy = CI->getType();
2667 if (Src->getType()->isInteger()) {
2668 if (SrcTy->getPrimitiveSize() == DestTy->getPrimitiveSize()) {
2669 // We can always eliminate a cast from ulong or long to the other.
2670 // We can always eliminate a cast from uint to int or the other on
2671 // 32-bit pointer platforms.
2672 if (DestTy->getPrimitiveSize() >= TD->getPointerSize()) {
2674 GEP.setOperand(i, Src);
2676 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
2677 SrcTy->getPrimitiveSize() == 4) {
2678 // We can always eliminate a cast from int to [u]long. We can
2679 // eliminate a cast from uint to [u]long iff the target is a 32-bit
2681 if (SrcTy->isSigned() ||
2682 SrcTy->getPrimitiveSize() >= TD->getPointerSize()) {
2684 GEP.setOperand(i, Src);
2689 // If we are using a wider index than needed for this platform, shrink it
2690 // to what we need. If the incoming value needs a cast instruction,
2691 // insert it. This explicit cast can make subsequent optimizations more
2693 Value *Op = GEP.getOperand(i);
2694 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
2695 if (Constant *C = dyn_cast<Constant>(Op)) {
2696 GEP.setOperand(i, ConstantExpr::getCast(C, TD->getIntPtrType()));
2699 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
2700 Op->getName()), GEP);
2701 GEP.setOperand(i, Op);
2705 if (MadeChange) return &GEP;
2707 // Combine Indices - If the source pointer to this getelementptr instruction
2708 // is a getelementptr instruction, combine the indices of the two
2709 // getelementptr instructions into a single instruction.
2711 std::vector<Value*> SrcGEPOperands;
2712 if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(PtrOp)) {
2713 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
2714 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
2715 if (CE->getOpcode() == Instruction::GetElementPtr)
2716 SrcGEPOperands.assign(CE->op_begin(), CE->op_end());
2719 if (!SrcGEPOperands.empty()) {
2720 // Note that if our source is a gep chain itself that we wait for that
2721 // chain to be resolved before we perform this transformation. This
2722 // avoids us creating a TON of code in some cases.
2724 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
2725 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
2726 return 0; // Wait until our source is folded to completion.
2728 std::vector<Value *> Indices;
2730 // Find out whether the last index in the source GEP is a sequential idx.
2731 bool EndsWithSequential = false;
2732 for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
2733 E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
2734 EndsWithSequential = !isa<StructType>(*I);
2736 // Can we combine the two pointer arithmetics offsets?
2737 if (EndsWithSequential) {
2738 // Replace: gep (gep %P, long B), long A, ...
2739 // With: T = long A+B; gep %P, T, ...
2741 Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
2742 if (SO1 == Constant::getNullValue(SO1->getType())) {
2744 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
2747 // If they aren't the same type, convert both to an integer of the
2748 // target's pointer size.
2749 if (SO1->getType() != GO1->getType()) {
2750 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
2751 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
2752 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
2753 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
2755 unsigned PS = TD->getPointerSize();
2757 if (SO1->getType()->getPrimitiveSize() == PS) {
2758 // Convert GO1 to SO1's type.
2759 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
2761 } else if (GO1->getType()->getPrimitiveSize() == PS) {
2762 // Convert SO1 to GO1's type.
2763 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
2765 const Type *PT = TD->getIntPtrType();
2766 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
2767 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
2771 if (isa<Constant>(SO1) && isa<Constant>(GO1))
2772 Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
2774 Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
2775 InsertNewInstBefore(cast<Instruction>(Sum), GEP);
2779 // Recycle the GEP we already have if possible.
2780 if (SrcGEPOperands.size() == 2) {
2781 GEP.setOperand(0, SrcGEPOperands[0]);
2782 GEP.setOperand(1, Sum);
2785 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2786 SrcGEPOperands.end()-1);
2787 Indices.push_back(Sum);
2788 Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
2790 } else if (isa<Constant>(*GEP.idx_begin()) &&
2791 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
2792 SrcGEPOperands.size() != 1) {
2793 // Otherwise we can do the fold if the first index of the GEP is a zero
2794 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
2795 SrcGEPOperands.end());
2796 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
2799 if (!Indices.empty())
2800 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
2802 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
2803 // GEP of global variable. If all of the indices for this GEP are
2804 // constants, we can promote this to a constexpr instead of an instruction.
2806 // Scan for nonconstants...
2807 std::vector<Constant*> Indices;
2808 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
2809 for (; I != E && isa<Constant>(*I); ++I)
2810 Indices.push_back(cast<Constant>(*I));
2812 if (I == E) { // If they are all constants...
2814 ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
2816 // Replace all uses of the GEP with the new constexpr...
2817 return ReplaceInstUsesWith(GEP, CE);
2819 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PtrOp)) {
2820 if (CE->getOpcode() == Instruction::Cast) {
2821 if (HasZeroPointerIndex) {
2822 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
2823 // into : GEP [10 x ubyte]* X, long 0, ...
2825 // This occurs when the program declares an array extern like "int X[];"
2827 Constant *X = CE->getOperand(0);
2828 const PointerType *CPTy = cast<PointerType>(CE->getType());
2829 if (const PointerType *XTy = dyn_cast<PointerType>(X->getType()))
2830 if (const ArrayType *XATy =
2831 dyn_cast<ArrayType>(XTy->getElementType()))
2832 if (const ArrayType *CATy =
2833 dyn_cast<ArrayType>(CPTy->getElementType()))
2834 if (CATy->getElementType() == XATy->getElementType()) {
2835 // At this point, we know that the cast source type is a pointer
2836 // to an array of the same type as the destination pointer
2837 // array. Because the array type is never stepped over (there
2838 // is a leading zero) we can fold the cast into this GEP.
2839 GEP.setOperand(0, X);
2849 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
2850 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
2851 if (AI.isArrayAllocation()) // Check C != 1
2852 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
2853 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
2854 AllocationInst *New = 0;
2856 // Create and insert the replacement instruction...
2857 if (isa<MallocInst>(AI))
2858 New = new MallocInst(NewTy, 0, AI.getName());
2860 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
2861 New = new AllocaInst(NewTy, 0, AI.getName());
2864 InsertNewInstBefore(New, AI);
2866 // Scan to the end of the allocation instructions, to skip over a block of
2867 // allocas if possible...
2869 BasicBlock::iterator It = New;
2870 while (isa<AllocationInst>(*It)) ++It;
2872 // Now that I is pointing to the first non-allocation-inst in the block,
2873 // insert our getelementptr instruction...
2875 std::vector<Value*> Idx(2, Constant::getNullValue(Type::IntTy));
2876 Value *V = new GetElementPtrInst(New, Idx, New->getName()+".sub", It);
2878 // Now make everything use the getelementptr instead of the original
2880 return ReplaceInstUsesWith(AI, V);
2883 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
2884 // Note that we only do this for alloca's, because malloc should allocate and
2885 // return a unique pointer, even for a zero byte allocation.
2886 if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
2887 TD->getTypeSize(AI.getAllocatedType()) == 0)
2888 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
2893 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
2894 Value *Op = FI.getOperand(0);
2896 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
2897 if (CastInst *CI = dyn_cast<CastInst>(Op))
2898 if (isa<PointerType>(CI->getOperand(0)->getType())) {
2899 FI.setOperand(0, CI->getOperand(0));
2903 // If we have 'free null' delete the instruction. This can happen in stl code
2904 // when lots of inlining happens.
2905 if (isa<ConstantPointerNull>(Op))
2906 return EraseInstFromFunction(FI);
2912 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
2913 /// constantexpr, return the constant value being addressed by the constant
2914 /// expression, or null if something is funny.
2916 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
2917 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
2918 return 0; // Do not allow stepping over the value!
2920 // Loop over all of the operands, tracking down which value we are
2922 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
2923 for (++I; I != E; ++I)
2924 if (const StructType *STy = dyn_cast<StructType>(*I)) {
2925 ConstantUInt *CU = cast<ConstantUInt>(I.getOperand());
2926 assert(CU->getValue() < STy->getNumElements() &&
2927 "Struct index out of range!");
2928 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
2929 C = cast<Constant>(CS->getValues()[CU->getValue()]);
2930 } else if (isa<ConstantAggregateZero>(C)) {
2931 C = Constant::getNullValue(STy->getElementType(CU->getValue()));
2935 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
2936 const ArrayType *ATy = cast<ArrayType>(*I);
2937 if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0;
2938 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
2939 C = cast<Constant>(CA->getValues()[CI->getRawValue()]);
2940 else if (isa<ConstantAggregateZero>(C))
2941 C = Constant::getNullValue(ATy->getElementType());
2950 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
2951 Value *Op = LI.getOperand(0);
2952 if (LI.isVolatile()) return 0;
2954 if (Constant *C = dyn_cast<Constant>(Op))
2955 if (C->isNullValue()) // load null -> 0
2956 return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
2957 else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
2958 Op = CPR->getValue();
2960 // Instcombine load (constant global) into the value loaded...
2961 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
2962 if (GV->isConstant() && !GV->isExternal())
2963 return ReplaceInstUsesWith(LI, GV->getInitializer());
2965 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
2966 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
2967 if (CE->getOpcode() == Instruction::GetElementPtr)
2968 if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
2969 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
2970 if (GV->isConstant() && !GV->isExternal())
2971 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
2972 return ReplaceInstUsesWith(LI, V);
2974 // load (cast X) --> cast (load X) iff safe
2975 if (CastInst *CI = dyn_cast<CastInst>(Op)) {
2976 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
2977 if (const PointerType *SrcTy =
2978 dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
2979 const Type *SrcPTy = SrcTy->getElementType();
2980 if (SrcPTy->isSized() && DestPTy->isSized() &&
2981 TD->getTypeSize(SrcPTy) == TD->getTypeSize(DestPTy) &&
2982 (SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
2983 (DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
2984 // Okay, we are casting from one integer or pointer type to another of
2985 // the same size. Instead of casting the pointer before the load, cast
2986 // the result of the loaded value.
2987 Value *NewLoad = InsertNewInstBefore(new LoadInst(CI->getOperand(0),
2988 CI->getName()), LI);
2989 // Now cast the result of the load.
2990 return new CastInst(NewLoad, LI.getType());
2999 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
3000 // Change br (not X), label True, label False to: br X, label False, True
3001 if (BI.isConditional() && !isa<Constant>(BI.getCondition())) {
3002 if (Value *V = dyn_castNotVal(BI.getCondition())) {
3003 BasicBlock *TrueDest = BI.getSuccessor(0);
3004 BasicBlock *FalseDest = BI.getSuccessor(1);
3005 // Swap Destinations and condition...
3007 BI.setSuccessor(0, FalseDest);
3008 BI.setSuccessor(1, TrueDest);
3010 } else if (SetCondInst *I = dyn_cast<SetCondInst>(BI.getCondition())) {
3011 // Cannonicalize setne -> seteq
3012 if ((I->getOpcode() == Instruction::SetNE ||
3013 I->getOpcode() == Instruction::SetLE ||
3014 I->getOpcode() == Instruction::SetGE) && I->hasOneUse()) {
3015 std::string Name = I->getName(); I->setName("");
3016 Instruction::BinaryOps NewOpcode =
3017 SetCondInst::getInverseCondition(I->getOpcode());
3018 Value *NewSCC = BinaryOperator::create(NewOpcode, I->getOperand(0),
3019 I->getOperand(1), Name, I);
3020 BasicBlock *TrueDest = BI.getSuccessor(0);
3021 BasicBlock *FalseDest = BI.getSuccessor(1);
3022 // Swap Destinations and condition...
3023 BI.setCondition(NewSCC);
3024 BI.setSuccessor(0, FalseDest);
3025 BI.setSuccessor(1, TrueDest);
3026 removeFromWorkList(I);
3027 I->getParent()->getInstList().erase(I);
3028 WorkList.push_back(cast<Instruction>(NewSCC));
3036 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
3037 Value *Cond = SI.getCondition();
3038 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
3039 if (I->getOpcode() == Instruction::Add)
3040 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
3041 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
3042 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
3043 SI.setOperand(i, ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
3045 SI.setOperand(0, I->getOperand(0));
3046 WorkList.push_back(I);
3054 void InstCombiner::removeFromWorkList(Instruction *I) {
3055 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
3059 bool InstCombiner::runOnFunction(Function &F) {
3060 bool Changed = false;
3061 TD = &getAnalysis<TargetData>();
3063 for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
3064 WorkList.push_back(&*i);
3067 while (!WorkList.empty()) {
3068 Instruction *I = WorkList.back(); // Get an instruction from the worklist
3069 WorkList.pop_back();
3071 // Check to see if we can DCE or ConstantPropagate the instruction...
3072 // Check to see if we can DIE the instruction...
3073 if (isInstructionTriviallyDead(I)) {
3074 // Add operands to the worklist...
3075 if (I->getNumOperands() < 4)
3076 AddUsesToWorkList(*I);
3079 I->getParent()->getInstList().erase(I);
3080 removeFromWorkList(I);
3084 // Instruction isn't dead, see if we can constant propagate it...
3085 if (Constant *C = ConstantFoldInstruction(I)) {
3086 // Add operands to the worklist...
3087 AddUsesToWorkList(*I);
3088 ReplaceInstUsesWith(*I, C);
3091 I->getParent()->getInstList().erase(I);
3092 removeFromWorkList(I);
3096 // Check to see if any of the operands of this instruction are a
3097 // ConstantPointerRef. Since they sneak in all over the place and inhibit
3098 // optimization, we want to strip them out unconditionally!
3099 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
3100 if (ConstantPointerRef *CPR =
3101 dyn_cast<ConstantPointerRef>(I->getOperand(i))) {
3102 I->setOperand(i, CPR->getValue());
3106 // Now that we have an instruction, try combining it to simplify it...
3107 if (Instruction *Result = visit(*I)) {
3109 // Should we replace the old instruction with a new one?
3111 DEBUG(std::cerr << "IC: Old = " << *I
3112 << " New = " << *Result);
3114 // Everything uses the new instruction now.
3115 I->replaceAllUsesWith(Result);
3117 // Push the new instruction and any users onto the worklist.
3118 WorkList.push_back(Result);
3119 AddUsersToWorkList(*Result);
3121 // Move the name to the new instruction first...
3122 std::string OldName = I->getName(); I->setName("");
3123 Result->setName(OldName);
3125 // Insert the new instruction into the basic block...
3126 BasicBlock *InstParent = I->getParent();
3127 InstParent->getInstList().insert(I, Result);
3129 // Make sure that we reprocess all operands now that we reduced their
3131 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
3132 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
3133 WorkList.push_back(OpI);
3135 // Instructions can end up on the worklist more than once. Make sure
3136 // we do not process an instruction that has been deleted.
3137 removeFromWorkList(I);
3139 // Erase the old instruction.
3140 InstParent->getInstList().erase(I);
3142 DEBUG(std::cerr << "IC: MOD = " << *I);
3144 // If the instruction was modified, it's possible that it is now dead.
3145 // if so, remove it.
3146 if (isInstructionTriviallyDead(I)) {
3147 // Make sure we process all operands now that we are reducing their
3149 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
3150 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
3151 WorkList.push_back(OpI);
3153 // Instructions may end up in the worklist more than once. Erase all
3154 // occurrances of this instruction.
3155 removeFromWorkList(I);
3156 I->getParent()->getInstList().erase(I);
3158 WorkList.push_back(Result);
3159 AddUsersToWorkList(*Result);
3169 Pass *llvm::createInstructionCombiningPass() {
3170 return new InstCombiner();