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
34 //===----------------------------------------------------------------------===//
36 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "llvm/IntrinsicInst.h"
39 #include "llvm/Pass.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/GlobalVariable.h"
42 #include "llvm/Target/TargetData.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/Local.h"
45 #include "llvm/Support/CallSite.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/GetElementPtrTypeIterator.h"
48 #include "llvm/Support/InstVisitor.h"
49 #include "llvm/Support/MathExtras.h"
50 #include "llvm/Support/PatternMatch.h"
51 #include "llvm/ADT/DepthFirstIterator.h"
52 #include "llvm/ADT/Statistic.h"
53 #include "llvm/ADT/STLExtras.h"
56 using namespace llvm::PatternMatch;
59 Statistic<> NumCombined ("instcombine", "Number of insts combined");
60 Statistic<> NumConstProp("instcombine", "Number of constant folds");
61 Statistic<> NumDeadInst ("instcombine", "Number of dead inst eliminated");
62 Statistic<> NumSunkInst ("instcombine", "Number of instructions sunk");
64 class InstCombiner : public FunctionPass,
65 public InstVisitor<InstCombiner, Instruction*> {
66 // Worklist of all of the instructions that need to be simplified.
67 std::vector<Instruction*> WorkList;
70 /// AddUsersToWorkList - When an instruction is simplified, add all users of
71 /// the instruction to the work lists because they might get more simplified
74 void AddUsersToWorkList(Instruction &I) {
75 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
77 WorkList.push_back(cast<Instruction>(*UI));
80 /// AddUsesToWorkList - When an instruction is simplified, add operands to
81 /// the work lists because they might get more simplified now.
83 void AddUsesToWorkList(Instruction &I) {
84 for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
85 if (Instruction *Op = dyn_cast<Instruction>(I.getOperand(i)))
86 WorkList.push_back(Op);
89 // removeFromWorkList - remove all instances of I from the worklist.
90 void removeFromWorkList(Instruction *I);
92 virtual bool runOnFunction(Function &F);
94 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
95 AU.addRequired<TargetData>();
99 TargetData &getTargetData() const { return *TD; }
101 // Visitation implementation - Implement instruction combining for different
102 // instruction types. The semantics are as follows:
104 // null - No change was made
105 // I - Change was made, I is still valid, I may be dead though
106 // otherwise - Change was made, replace I with returned instruction
108 Instruction *visitAdd(BinaryOperator &I);
109 Instruction *visitSub(BinaryOperator &I);
110 Instruction *visitMul(BinaryOperator &I);
111 Instruction *visitDiv(BinaryOperator &I);
112 Instruction *visitRem(BinaryOperator &I);
113 Instruction *visitAnd(BinaryOperator &I);
114 Instruction *visitOr (BinaryOperator &I);
115 Instruction *visitXor(BinaryOperator &I);
116 Instruction *visitSetCondInst(SetCondInst &I);
117 Instruction *visitSetCondInstWithCastAndCast(SetCondInst &SCI);
119 Instruction *FoldGEPSetCC(User *GEPLHS, Value *RHS,
120 Instruction::BinaryOps Cond, Instruction &I);
121 Instruction *visitShiftInst(ShiftInst &I);
122 Instruction *visitCastInst(CastInst &CI);
123 Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
125 Instruction *visitSelectInst(SelectInst &CI);
126 Instruction *visitCallInst(CallInst &CI);
127 Instruction *visitInvokeInst(InvokeInst &II);
128 Instruction *visitPHINode(PHINode &PN);
129 Instruction *visitGetElementPtrInst(GetElementPtrInst &GEP);
130 Instruction *visitAllocationInst(AllocationInst &AI);
131 Instruction *visitFreeInst(FreeInst &FI);
132 Instruction *visitLoadInst(LoadInst &LI);
133 Instruction *visitStoreInst(StoreInst &SI);
134 Instruction *visitBranchInst(BranchInst &BI);
135 Instruction *visitSwitchInst(SwitchInst &SI);
137 // visitInstruction - Specify what to return for unhandled instructions...
138 Instruction *visitInstruction(Instruction &I) { return 0; }
141 Instruction *visitCallSite(CallSite CS);
142 bool transformConstExprCastCall(CallSite CS);
145 // InsertNewInstBefore - insert an instruction New before instruction Old
146 // in the program. Add the new instruction to the worklist.
148 Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
149 assert(New && New->getParent() == 0 &&
150 "New instruction already inserted into a basic block!");
151 BasicBlock *BB = Old.getParent();
152 BB->getInstList().insert(&Old, New); // Insert inst
153 WorkList.push_back(New); // Add to worklist
157 /// InsertCastBefore - Insert a cast of V to TY before the instruction POS.
158 /// This also adds the cast to the worklist. Finally, this returns the
160 Value *InsertCastBefore(Value *V, const Type *Ty, Instruction &Pos) {
161 if (V->getType() == Ty) return V;
163 Instruction *C = new CastInst(V, Ty, V->getName(), &Pos);
164 WorkList.push_back(C);
168 // ReplaceInstUsesWith - This method is to be used when an instruction is
169 // found to be dead, replacable with another preexisting expression. Here
170 // we add all uses of I to the worklist, replace all uses of I with the new
171 // value, then return I, so that the inst combiner will know that I was
174 Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
175 AddUsersToWorkList(I); // Add all modified instrs to worklist
177 I.replaceAllUsesWith(V);
180 // If we are replacing the instruction with itself, this must be in a
181 // segment of unreachable code, so just clobber the instruction.
182 I.replaceAllUsesWith(UndefValue::get(I.getType()));
187 // EraseInstFromFunction - When dealing with an instruction that has side
188 // effects or produces a void value, we can't rely on DCE to delete the
189 // instruction. Instead, visit methods should return the value returned by
191 Instruction *EraseInstFromFunction(Instruction &I) {
192 assert(I.use_empty() && "Cannot erase instruction that is used!");
193 AddUsesToWorkList(I);
194 removeFromWorkList(&I);
196 return 0; // Don't do anything with FI
201 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
202 /// InsertBefore instruction. This is specialized a bit to avoid inserting
203 /// casts that are known to not do anything...
205 Value *InsertOperandCastBefore(Value *V, const Type *DestTy,
206 Instruction *InsertBefore);
208 // SimplifyCommutative - This performs a few simplifications for commutative
210 bool SimplifyCommutative(BinaryOperator &I);
213 // FoldOpIntoPhi - Given a binary operator or cast instruction which has a
214 // PHI node as operand #0, see if we can fold the instruction into the PHI
215 // (which is only possible if all operands to the PHI are constants).
216 Instruction *FoldOpIntoPhi(Instruction &I);
218 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
219 // operator and they all are only used by the PHI, PHI together their
220 // inputs, and do the operation once, to the result of the PHI.
221 Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
223 Instruction *OptAndOp(Instruction *Op, ConstantIntegral *OpRHS,
224 ConstantIntegral *AndRHS, BinaryOperator &TheAnd);
226 Instruction *InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
227 bool Inside, Instruction &IB);
230 RegisterOpt<InstCombiner> X("instcombine", "Combine redundant instructions");
233 // getComplexity: Assign a complexity or rank value to LLVM Values...
234 // 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
235 static unsigned getComplexity(Value *V) {
236 if (isa<Instruction>(V)) {
237 if (BinaryOperator::isNeg(V) || BinaryOperator::isNot(V))
241 if (isa<Argument>(V)) return 3;
242 return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
245 // isOnlyUse - Return true if this instruction will be deleted if we stop using
247 static bool isOnlyUse(Value *V) {
248 return V->hasOneUse() || isa<Constant>(V);
251 // getPromotedType - Return the specified type promoted as it would be to pass
252 // though a va_arg area...
253 static const Type *getPromotedType(const Type *Ty) {
254 switch (Ty->getTypeID()) {
255 case Type::SByteTyID:
256 case Type::ShortTyID: return Type::IntTy;
257 case Type::UByteTyID:
258 case Type::UShortTyID: return Type::UIntTy;
259 case Type::FloatTyID: return Type::DoubleTy;
264 /// isCast - If the specified operand is a CastInst or a constant expr cast,
265 /// return the operand value, otherwise return null.
266 static Value *isCast(Value *V) {
267 if (CastInst *I = dyn_cast<CastInst>(V))
268 return I->getOperand(0);
269 else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
270 if (CE->getOpcode() == Instruction::Cast)
271 return CE->getOperand(0);
275 // SimplifyCommutative - This performs a few simplifications for commutative
278 // 1. Order operands such that they are listed from right (least complex) to
279 // left (most complex). This puts constants before unary operators before
282 // 2. Transform: (op (op V, C1), C2) ==> (op V, (op C1, C2))
283 // 3. Transform: (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
285 bool InstCombiner::SimplifyCommutative(BinaryOperator &I) {
286 bool Changed = false;
287 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1)))
288 Changed = !I.swapOperands();
290 if (!I.isAssociative()) return Changed;
291 Instruction::BinaryOps Opcode = I.getOpcode();
292 if (BinaryOperator *Op = dyn_cast<BinaryOperator>(I.getOperand(0)))
293 if (Op->getOpcode() == Opcode && isa<Constant>(Op->getOperand(1))) {
294 if (isa<Constant>(I.getOperand(1))) {
295 Constant *Folded = ConstantExpr::get(I.getOpcode(),
296 cast<Constant>(I.getOperand(1)),
297 cast<Constant>(Op->getOperand(1)));
298 I.setOperand(0, Op->getOperand(0));
299 I.setOperand(1, Folded);
301 } else if (BinaryOperator *Op1=dyn_cast<BinaryOperator>(I.getOperand(1)))
302 if (Op1->getOpcode() == Opcode && isa<Constant>(Op1->getOperand(1)) &&
303 isOnlyUse(Op) && isOnlyUse(Op1)) {
304 Constant *C1 = cast<Constant>(Op->getOperand(1));
305 Constant *C2 = cast<Constant>(Op1->getOperand(1));
307 // Fold (op (op V1, C1), (op V2, C2)) ==> (op (op V1, V2), (op C1,C2))
308 Constant *Folded = ConstantExpr::get(I.getOpcode(), C1, C2);
309 Instruction *New = BinaryOperator::create(Opcode, Op->getOperand(0),
312 WorkList.push_back(New);
313 I.setOperand(0, New);
314 I.setOperand(1, Folded);
321 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
322 // if the LHS is a constant zero (which is the 'negate' form).
324 static inline Value *dyn_castNegVal(Value *V) {
325 if (BinaryOperator::isNeg(V))
326 return BinaryOperator::getNegArgument(V);
328 // Constants can be considered to be negated values if they can be folded.
329 if (ConstantInt *C = dyn_cast<ConstantInt>(V))
330 return ConstantExpr::getNeg(C);
334 static inline Value *dyn_castNotVal(Value *V) {
335 if (BinaryOperator::isNot(V))
336 return BinaryOperator::getNotArgument(V);
338 // Constants can be considered to be not'ed values...
339 if (ConstantIntegral *C = dyn_cast<ConstantIntegral>(V))
340 return ConstantExpr::getNot(C);
344 // dyn_castFoldableMul - If this value is a multiply that can be folded into
345 // other computations (because it has a constant operand), return the
346 // non-constant operand of the multiply, and set CST to point to the multiplier.
347 // Otherwise, return null.
349 static inline Value *dyn_castFoldableMul(Value *V, ConstantInt *&CST) {
350 if (V->hasOneUse() && V->getType()->isInteger())
351 if (Instruction *I = dyn_cast<Instruction>(V)) {
352 if (I->getOpcode() == Instruction::Mul)
353 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1))))
354 return I->getOperand(0);
355 if (I->getOpcode() == Instruction::Shl)
356 if ((CST = dyn_cast<ConstantInt>(I->getOperand(1)))) {
357 // The multiplier is really 1 << CST.
358 Constant *One = ConstantInt::get(V->getType(), 1);
359 CST = cast<ConstantInt>(ConstantExpr::getShl(One, CST));
360 return I->getOperand(0);
366 /// dyn_castGetElementPtr - If this is a getelementptr instruction or constant
367 /// expression, return it.
368 static User *dyn_castGetElementPtr(Value *V) {
369 if (isa<GetElementPtrInst>(V)) return cast<User>(V);
370 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
371 if (CE->getOpcode() == Instruction::GetElementPtr)
372 return cast<User>(V);
376 // AddOne, SubOne - Add or subtract a constant one from an integer constant...
377 static ConstantInt *AddOne(ConstantInt *C) {
378 return cast<ConstantInt>(ConstantExpr::getAdd(C,
379 ConstantInt::get(C->getType(), 1)));
381 static ConstantInt *SubOne(ConstantInt *C) {
382 return cast<ConstantInt>(ConstantExpr::getSub(C,
383 ConstantInt::get(C->getType(), 1)));
386 // isTrueWhenEqual - Return true if the specified setcondinst instruction is
387 // true when both operands are equal...
389 static bool isTrueWhenEqual(Instruction &I) {
390 return I.getOpcode() == Instruction::SetEQ ||
391 I.getOpcode() == Instruction::SetGE ||
392 I.getOpcode() == Instruction::SetLE;
395 /// AssociativeOpt - Perform an optimization on an associative operator. This
396 /// function is designed to check a chain of associative operators for a
397 /// potential to apply a certain optimization. Since the optimization may be
398 /// applicable if the expression was reassociated, this checks the chain, then
399 /// reassociates the expression as necessary to expose the optimization
400 /// opportunity. This makes use of a special Functor, which must define
401 /// 'shouldApply' and 'apply' methods.
403 template<typename Functor>
404 Instruction *AssociativeOpt(BinaryOperator &Root, const Functor &F) {
405 unsigned Opcode = Root.getOpcode();
406 Value *LHS = Root.getOperand(0);
408 // Quick check, see if the immediate LHS matches...
409 if (F.shouldApply(LHS))
410 return F.apply(Root);
412 // Otherwise, if the LHS is not of the same opcode as the root, return.
413 Instruction *LHSI = dyn_cast<Instruction>(LHS);
414 while (LHSI && LHSI->getOpcode() == Opcode && LHSI->hasOneUse()) {
415 // Should we apply this transform to the RHS?
416 bool ShouldApply = F.shouldApply(LHSI->getOperand(1));
418 // If not to the RHS, check to see if we should apply to the LHS...
419 if (!ShouldApply && F.shouldApply(LHSI->getOperand(0))) {
420 cast<BinaryOperator>(LHSI)->swapOperands(); // Make the LHS the RHS
424 // If the functor wants to apply the optimization to the RHS of LHSI,
425 // reassociate the expression from ((? op A) op B) to (? op (A op B))
427 BasicBlock *BB = Root.getParent();
429 // Now all of the instructions are in the current basic block, go ahead
430 // and perform the reassociation.
431 Instruction *TmpLHSI = cast<Instruction>(Root.getOperand(0));
433 // First move the selected RHS to the LHS of the root...
434 Root.setOperand(0, LHSI->getOperand(1));
436 // Make what used to be the LHS of the root be the user of the root...
437 Value *ExtraOperand = TmpLHSI->getOperand(1);
438 if (&Root == TmpLHSI) {
439 Root.replaceAllUsesWith(Constant::getNullValue(TmpLHSI->getType()));
442 Root.replaceAllUsesWith(TmpLHSI); // Users now use TmpLHSI
443 TmpLHSI->setOperand(1, &Root); // TmpLHSI now uses the root
444 TmpLHSI->getParent()->getInstList().remove(TmpLHSI);
445 BasicBlock::iterator ARI = &Root; ++ARI;
446 BB->getInstList().insert(ARI, TmpLHSI); // Move TmpLHSI to after Root
449 // Now propagate the ExtraOperand down the chain of instructions until we
451 while (TmpLHSI != LHSI) {
452 Instruction *NextLHSI = cast<Instruction>(TmpLHSI->getOperand(0));
453 // Move the instruction to immediately before the chain we are
454 // constructing to avoid breaking dominance properties.
455 NextLHSI->getParent()->getInstList().remove(NextLHSI);
456 BB->getInstList().insert(ARI, NextLHSI);
459 Value *NextOp = NextLHSI->getOperand(1);
460 NextLHSI->setOperand(1, ExtraOperand);
462 ExtraOperand = NextOp;
465 // Now that the instructions are reassociated, have the functor perform
466 // the transformation...
467 return F.apply(Root);
470 LHSI = dyn_cast<Instruction>(LHSI->getOperand(0));
476 // AddRHS - Implements: X + X --> X << 1
479 AddRHS(Value *rhs) : RHS(rhs) {}
480 bool shouldApply(Value *LHS) const { return LHS == RHS; }
481 Instruction *apply(BinaryOperator &Add) const {
482 return new ShiftInst(Instruction::Shl, Add.getOperand(0),
483 ConstantInt::get(Type::UByteTy, 1));
487 // AddMaskingAnd - Implements (A & C1)+(B & C2) --> (A & C1)|(B & C2)
489 struct AddMaskingAnd {
491 AddMaskingAnd(Constant *c) : C2(c) {}
492 bool shouldApply(Value *LHS) const {
494 return match(LHS, m_And(m_Value(), m_ConstantInt(C1))) &&
495 ConstantExpr::getAnd(C1, C2)->isNullValue();
497 Instruction *apply(BinaryOperator &Add) const {
498 return BinaryOperator::createOr(Add.getOperand(0), Add.getOperand(1));
502 static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
504 if (isa<CastInst>(I)) {
505 if (Constant *SOC = dyn_cast<Constant>(SO))
506 return ConstantExpr::getCast(SOC, I.getType());
508 return IC->InsertNewInstBefore(new CastInst(SO, I.getType(),
509 SO->getName() + ".cast"), I);
512 // Figure out if the constant is the left or the right argument.
513 bool ConstIsRHS = isa<Constant>(I.getOperand(1));
514 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
516 if (Constant *SOC = dyn_cast<Constant>(SO)) {
518 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
519 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
522 Value *Op0 = SO, *Op1 = ConstOperand;
526 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I))
527 New = BinaryOperator::create(BO->getOpcode(), Op0, Op1,SO->getName()+".op");
528 else if (ShiftInst *SI = dyn_cast<ShiftInst>(&I))
529 New = new ShiftInst(SI->getOpcode(), Op0, Op1, SO->getName()+".sh");
531 assert(0 && "Unknown binary instruction type!");
534 return IC->InsertNewInstBefore(New, I);
537 // FoldOpIntoSelect - Given an instruction with a select as one operand and a
538 // constant as the other operand, try to fold the binary operator into the
539 // select arguments. This also works for Cast instructions, which obviously do
540 // not have a second operand.
541 static Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
543 // Don't modify shared select instructions
544 if (!SI->hasOneUse()) return 0;
545 Value *TV = SI->getOperand(1);
546 Value *FV = SI->getOperand(2);
548 if (isa<Constant>(TV) || isa<Constant>(FV)) {
549 // Bool selects with constant operands can be folded to logical ops.
550 if (SI->getType() == Type::BoolTy) return 0;
552 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, IC);
553 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, IC);
555 return new SelectInst(SI->getCondition(), SelectTrueVal,
562 /// FoldOpIntoPhi - Given a binary operator or cast instruction which has a PHI
563 /// node as operand #0, see if we can fold the instruction into the PHI (which
564 /// is only possible if all operands to the PHI are constants).
565 Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
566 PHINode *PN = cast<PHINode>(I.getOperand(0));
567 unsigned NumPHIValues = PN->getNumIncomingValues();
568 if (!PN->hasOneUse() || NumPHIValues == 0 ||
569 !isa<Constant>(PN->getIncomingValue(0))) return 0;
571 // Check to see if all of the operands of the PHI are constants. If not, we
572 // cannot do the transformation.
573 for (unsigned i = 1; i != NumPHIValues; ++i)
574 if (!isa<Constant>(PN->getIncomingValue(i)))
577 // Okay, we can do the transformation: create the new PHI node.
578 PHINode *NewPN = new PHINode(I.getType(), I.getName());
580 NewPN->reserveOperandSpace(PN->getNumOperands()/2);
581 InsertNewInstBefore(NewPN, *PN);
583 // Next, add all of the operands to the PHI.
584 if (I.getNumOperands() == 2) {
585 Constant *C = cast<Constant>(I.getOperand(1));
586 for (unsigned i = 0; i != NumPHIValues; ++i) {
587 Constant *InV = cast<Constant>(PN->getIncomingValue(i));
588 NewPN->addIncoming(ConstantExpr::get(I.getOpcode(), InV, C),
589 PN->getIncomingBlock(i));
592 assert(isa<CastInst>(I) && "Unary op should be a cast!");
593 const Type *RetTy = I.getType();
594 for (unsigned i = 0; i != NumPHIValues; ++i) {
595 Constant *InV = cast<Constant>(PN->getIncomingValue(i));
596 NewPN->addIncoming(ConstantExpr::getCast(InV, RetTy),
597 PN->getIncomingBlock(i));
600 return ReplaceInstUsesWith(I, NewPN);
603 Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
604 bool Changed = SimplifyCommutative(I);
605 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
607 if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
608 // X + undef -> undef
609 if (isa<UndefValue>(RHS))
610 return ReplaceInstUsesWith(I, RHS);
613 if (!I.getType()->isFloatingPoint() && // -0 + +0 = +0, so it's not a noop
615 return ReplaceInstUsesWith(I, LHS);
617 // X + (signbit) --> X ^ signbit
618 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHSC)) {
619 unsigned NumBits = CI->getType()->getPrimitiveSizeInBits();
620 uint64_t Val = CI->getRawValue() & (1ULL << NumBits)-1;
621 if (Val == (1ULL << (NumBits-1)))
622 return BinaryOperator::createXor(LHS, RHS);
625 if (isa<PHINode>(LHS))
626 if (Instruction *NV = FoldOpIntoPhi(I))
631 if (I.getType()->isInteger()) {
632 if (Instruction *Result = AssociativeOpt(I, AddRHS(RHS))) return Result;
634 if (Instruction *RHSI = dyn_cast<Instruction>(RHS)) {
635 if (RHSI->getOpcode() == Instruction::Sub)
636 if (LHS == RHSI->getOperand(1)) // A + (B - A) --> B
637 return ReplaceInstUsesWith(I, RHSI->getOperand(0));
639 if (Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
640 if (LHSI->getOpcode() == Instruction::Sub)
641 if (RHS == LHSI->getOperand(1)) // (B - A) + A --> B
642 return ReplaceInstUsesWith(I, LHSI->getOperand(0));
647 if (Value *V = dyn_castNegVal(LHS))
648 return BinaryOperator::createSub(RHS, V);
651 if (!isa<Constant>(RHS))
652 if (Value *V = dyn_castNegVal(RHS))
653 return BinaryOperator::createSub(LHS, V);
657 if (Value *X = dyn_castFoldableMul(LHS, C2)) {
658 if (X == RHS) // X*C + X --> X * (C+1)
659 return BinaryOperator::createMul(RHS, AddOne(C2));
661 // X*C1 + X*C2 --> X * (C1+C2)
663 if (X == dyn_castFoldableMul(RHS, C1))
664 return BinaryOperator::createMul(X, ConstantExpr::getAdd(C1, C2));
667 // X + X*C --> X * (C+1)
668 if (dyn_castFoldableMul(RHS, C2) == LHS)
669 return BinaryOperator::createMul(LHS, AddOne(C2));
672 // (A & C1)+(B & C2) --> (A & C1)|(B & C2) iff C1&C2 == 0
673 if (match(RHS, m_And(m_Value(), m_ConstantInt(C2))))
674 if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
676 if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
678 if (match(LHS, m_Not(m_Value(X)))) { // ~X + C --> (C-1) - X
679 Constant *C= ConstantExpr::getSub(CRHS, ConstantInt::get(I.getType(), 1));
680 return BinaryOperator::createSub(C, X);
683 // (X & FF00) + xx00 -> (X+xx00) & FF00
684 if (LHS->hasOneUse() && match(LHS, m_And(m_Value(X), m_ConstantInt(C2)))) {
685 Constant *Anded = ConstantExpr::getAnd(CRHS, C2);
687 // See if all bits from the first bit set in the Add RHS up are included
688 // in the mask. First, get the rightmost bit.
689 uint64_t AddRHSV = CRHS->getRawValue();
691 // Form a mask of all bits from the lowest bit added through the top.
692 uint64_t AddRHSHighBits = ~((AddRHSV & -AddRHSV)-1);
693 AddRHSHighBits &= ~0ULL >> (64-C2->getType()->getPrimitiveSizeInBits());
695 // See if the and mask includes all of these bits.
696 uint64_t AddRHSHighBitsAnd = AddRHSHighBits & C2->getRawValue();
698 if (AddRHSHighBits == AddRHSHighBitsAnd) {
699 // Okay, the xform is safe. Insert the new add pronto.
700 Value *NewAdd = InsertNewInstBefore(BinaryOperator::createAdd(X, CRHS,
702 return BinaryOperator::createAnd(NewAdd, C2);
707 // Try to fold constant add into select arguments.
708 if (SelectInst *SI = dyn_cast<SelectInst>(LHS))
709 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
713 return Changed ? &I : 0;
716 // isSignBit - Return true if the value represented by the constant only has the
717 // highest order bit set.
718 static bool isSignBit(ConstantInt *CI) {
719 unsigned NumBits = CI->getType()->getPrimitiveSizeInBits();
720 return (CI->getRawValue() & (~0ULL >> (64-NumBits))) == (1ULL << (NumBits-1));
723 /// RemoveNoopCast - Strip off nonconverting casts from the value.
725 static Value *RemoveNoopCast(Value *V) {
726 if (CastInst *CI = dyn_cast<CastInst>(V)) {
727 const Type *CTy = CI->getType();
728 const Type *OpTy = CI->getOperand(0)->getType();
729 if (CTy->isInteger() && OpTy->isInteger()) {
730 if (CTy->getPrimitiveSizeInBits() == OpTy->getPrimitiveSizeInBits())
731 return RemoveNoopCast(CI->getOperand(0));
732 } else if (isa<PointerType>(CTy) && isa<PointerType>(OpTy))
733 return RemoveNoopCast(CI->getOperand(0));
738 Instruction *InstCombiner::visitSub(BinaryOperator &I) {
739 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
741 if (Op0 == Op1) // sub X, X -> 0
742 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
744 // If this is a 'B = x-(-A)', change to B = x+A...
745 if (Value *V = dyn_castNegVal(Op1))
746 return BinaryOperator::createAdd(Op0, V);
748 if (isa<UndefValue>(Op0))
749 return ReplaceInstUsesWith(I, Op0); // undef - X -> undef
750 if (isa<UndefValue>(Op1))
751 return ReplaceInstUsesWith(I, Op1); // X - undef -> undef
753 if (ConstantInt *C = dyn_cast<ConstantInt>(Op0)) {
754 // Replace (-1 - A) with (~A)...
755 if (C->isAllOnesValue())
756 return BinaryOperator::createNot(Op1);
758 // C - ~X == X + (1+C)
760 if (match(Op1, m_Not(m_Value(X))))
761 return BinaryOperator::createAdd(X,
762 ConstantExpr::getAdd(C, ConstantInt::get(I.getType(), 1)));
763 // -((uint)X >> 31) -> ((int)X >> 31)
764 // -((int)X >> 31) -> ((uint)X >> 31)
765 if (C->isNullValue()) {
766 Value *NoopCastedRHS = RemoveNoopCast(Op1);
767 if (ShiftInst *SI = dyn_cast<ShiftInst>(NoopCastedRHS))
768 if (SI->getOpcode() == Instruction::Shr)
769 if (ConstantUInt *CU = dyn_cast<ConstantUInt>(SI->getOperand(1))) {
771 if (SI->getType()->isSigned())
772 NewTy = SI->getType()->getUnsignedVersion();
774 NewTy = SI->getType()->getSignedVersion();
775 // Check to see if we are shifting out everything but the sign bit.
776 if (CU->getValue() == SI->getType()->getPrimitiveSizeInBits()-1) {
777 // Ok, the transformation is safe. Insert a cast of the incoming
778 // value, then the new shift, then the new cast.
779 Instruction *FirstCast = new CastInst(SI->getOperand(0), NewTy,
780 SI->getOperand(0)->getName());
781 Value *InV = InsertNewInstBefore(FirstCast, I);
782 Instruction *NewShift = new ShiftInst(Instruction::Shr, FirstCast,
784 if (NewShift->getType() == I.getType())
787 InV = InsertNewInstBefore(NewShift, I);
788 return new CastInst(NewShift, I.getType());
794 // Try to fold constant sub into select arguments.
795 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
796 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
799 if (isa<PHINode>(Op0))
800 if (Instruction *NV = FoldOpIntoPhi(I))
804 if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
805 if (Op1I->getOpcode() == Instruction::Add &&
806 !Op0->getType()->isFloatingPoint()) {
807 if (Op1I->getOperand(0) == Op0) // X-(X+Y) == -Y
808 return BinaryOperator::createNeg(Op1I->getOperand(1), I.getName());
809 else if (Op1I->getOperand(1) == Op0) // X-(Y+X) == -Y
810 return BinaryOperator::createNeg(Op1I->getOperand(0), I.getName());
811 else if (ConstantInt *CI1 = dyn_cast<ConstantInt>(I.getOperand(0))) {
812 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(Op1I->getOperand(1)))
813 // C1-(X+C2) --> (C1-C2)-X
814 return BinaryOperator::createSub(ConstantExpr::getSub(CI1, CI2),
815 Op1I->getOperand(0));
819 if (Op1I->hasOneUse()) {
820 // Replace (x - (y - z)) with (x + (z - y)) if the (y - z) subexpression
821 // is not used by anyone else...
823 if (Op1I->getOpcode() == Instruction::Sub &&
824 !Op1I->getType()->isFloatingPoint()) {
825 // Swap the two operands of the subexpr...
826 Value *IIOp0 = Op1I->getOperand(0), *IIOp1 = Op1I->getOperand(1);
827 Op1I->setOperand(0, IIOp1);
828 Op1I->setOperand(1, IIOp0);
830 // Create the new top level add instruction...
831 return BinaryOperator::createAdd(Op0, Op1);
834 // Replace (A - (A & B)) with (A & ~B) if this is the only use of (A&B)...
836 if (Op1I->getOpcode() == Instruction::And &&
837 (Op1I->getOperand(0) == Op0 || Op1I->getOperand(1) == Op0)) {
838 Value *OtherOp = Op1I->getOperand(Op1I->getOperand(0) == Op0);
841 InsertNewInstBefore(BinaryOperator::createNot(OtherOp, "B.not"), I);
842 return BinaryOperator::createAnd(Op0, NewNot);
845 // -(X sdiv C) -> (X sdiv -C)
846 if (Op1I->getOpcode() == Instruction::Div)
847 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
848 if (CSI->isNullValue())
849 if (Constant *DivRHS = dyn_cast<Constant>(Op1I->getOperand(1)))
850 return BinaryOperator::createDiv(Op1I->getOperand(0),
851 ConstantExpr::getNeg(DivRHS));
853 // X - X*C --> X * (1-C)
855 if (dyn_castFoldableMul(Op1I, C2) == Op0) {
857 ConstantExpr::getSub(ConstantInt::get(I.getType(), 1), C2);
858 return BinaryOperator::createMul(Op0, CP1);
863 if (!Op0->getType()->isFloatingPoint())
864 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
865 if (Op0I->getOpcode() == Instruction::Add) {
866 if (Op0I->getOperand(0) == Op1) // (Y+X)-Y == X
867 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
868 else if (Op0I->getOperand(1) == Op1) // (X+Y)-Y == X
869 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
870 } else if (Op0I->getOpcode() == Instruction::Sub) {
871 if (Op0I->getOperand(0) == Op1) // (X-Y)-X == -Y
872 return BinaryOperator::createNeg(Op0I->getOperand(1), I.getName());
876 if (Value *X = dyn_castFoldableMul(Op0, C1)) {
877 if (X == Op1) { // X*C - X --> X * (C-1)
878 Constant *CP1 = ConstantExpr::getSub(C1, ConstantInt::get(I.getType(),1));
879 return BinaryOperator::createMul(Op1, CP1);
882 ConstantInt *C2; // X*C1 - X*C2 -> X * (C1-C2)
883 if (X == dyn_castFoldableMul(Op1, C2))
884 return BinaryOperator::createMul(Op1, ConstantExpr::getSub(C1, C2));
889 /// isSignBitCheck - Given an exploded setcc instruction, return true if it is
890 /// really just returns true if the most significant (sign) bit is set.
891 static bool isSignBitCheck(unsigned Opcode, Value *LHS, ConstantInt *RHS) {
892 if (RHS->getType()->isSigned()) {
893 // True if source is LHS < 0 or LHS <= -1
894 return Opcode == Instruction::SetLT && RHS->isNullValue() ||
895 Opcode == Instruction::SetLE && RHS->isAllOnesValue();
897 ConstantUInt *RHSC = cast<ConstantUInt>(RHS);
898 // True if source is LHS > 127 or LHS >= 128, where the constants depend on
899 // the size of the integer type.
900 if (Opcode == Instruction::SetGE)
901 return RHSC->getValue() ==
902 1ULL << (RHS->getType()->getPrimitiveSizeInBits()-1);
903 if (Opcode == Instruction::SetGT)
904 return RHSC->getValue() ==
905 (1ULL << (RHS->getType()->getPrimitiveSizeInBits()-1))-1;
910 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
911 bool Changed = SimplifyCommutative(I);
912 Value *Op0 = I.getOperand(0);
914 if (isa<UndefValue>(I.getOperand(1))) // undef * X -> 0
915 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
917 // Simplify mul instructions with a constant RHS...
918 if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
919 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
921 // ((X << C1)*C2) == (X * (C2 << C1))
922 if (ShiftInst *SI = dyn_cast<ShiftInst>(Op0))
923 if (SI->getOpcode() == Instruction::Shl)
924 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
925 return BinaryOperator::createMul(SI->getOperand(0),
926 ConstantExpr::getShl(CI, ShOp));
928 if (CI->isNullValue())
929 return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
930 if (CI->equalsInt(1)) // X * 1 == X
931 return ReplaceInstUsesWith(I, Op0);
932 if (CI->isAllOnesValue()) // X * -1 == 0 - X
933 return BinaryOperator::createNeg(Op0, I.getName());
935 int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
936 if (isPowerOf2_64(Val)) { // Replace X*(2^C) with X << C
937 uint64_t C = Log2_64(Val);
938 return new ShiftInst(Instruction::Shl, Op0,
939 ConstantUInt::get(Type::UByteTy, C));
941 } else if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1)) {
942 if (Op1F->isNullValue())
943 return ReplaceInstUsesWith(I, Op1);
945 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
946 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
947 if (Op1F->getValue() == 1.0)
948 return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul double %X, 1.0'
951 // Try to fold constant mul into select arguments.
952 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
953 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
956 if (isa<PHINode>(Op0))
957 if (Instruction *NV = FoldOpIntoPhi(I))
961 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
962 if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
963 return BinaryOperator::createMul(Op0v, Op1v);
965 // If one of the operands of the multiply is a cast from a boolean value, then
966 // we know the bool is either zero or one, so this is a 'masking' multiply.
967 // See if we can simplify things based on how the boolean was originally
969 CastInst *BoolCast = 0;
970 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
971 if (CI->getOperand(0)->getType() == Type::BoolTy)
974 if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
975 if (CI->getOperand(0)->getType() == Type::BoolTy)
978 if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
979 Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
980 const Type *SCOpTy = SCIOp0->getType();
982 // If the setcc is true iff the sign bit of X is set, then convert this
983 // multiply into a shift/and combination.
984 if (isa<ConstantInt>(SCIOp1) &&
985 isSignBitCheck(SCI->getOpcode(), SCIOp0, cast<ConstantInt>(SCIOp1))) {
986 // Shift the X value right to turn it into "all signbits".
987 Constant *Amt = ConstantUInt::get(Type::UByteTy,
988 SCOpTy->getPrimitiveSizeInBits()-1);
989 if (SCIOp0->getType()->isUnsigned()) {
990 const Type *NewTy = SCIOp0->getType()->getSignedVersion();
991 SCIOp0 = InsertNewInstBefore(new CastInst(SCIOp0, NewTy,
992 SCIOp0->getName()), I);
996 InsertNewInstBefore(new ShiftInst(Instruction::Shr, SCIOp0, Amt,
997 BoolCast->getOperand(0)->getName()+
1000 // If the multiply type is not the same as the source type, sign extend
1001 // or truncate to the multiply type.
1002 if (I.getType() != V->getType())
1003 V = InsertNewInstBefore(new CastInst(V, I.getType(), V->getName()),I);
1005 Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
1006 return BinaryOperator::createAnd(V, OtherOp);
1011 return Changed ? &I : 0;
1014 Instruction *InstCombiner::visitDiv(BinaryOperator &I) {
1015 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1017 if (isa<UndefValue>(Op0)) // undef / X -> 0
1018 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1019 if (isa<UndefValue>(Op1))
1020 return ReplaceInstUsesWith(I, Op1); // X / undef -> undef
1022 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
1024 if (RHS->equalsInt(1))
1025 return ReplaceInstUsesWith(I, Op0);
1028 if (RHS->isAllOnesValue())
1029 return BinaryOperator::createNeg(Op0);
1031 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
1032 if (LHS->getOpcode() == Instruction::Div)
1033 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
1034 // (X / C1) / C2 -> X / (C1*C2)
1035 return BinaryOperator::createDiv(LHS->getOperand(0),
1036 ConstantExpr::getMul(RHS, LHSRHS));
1039 // Check to see if this is an unsigned division with an exact power of 2,
1040 // if so, convert to a right shift.
1041 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
1042 if (uint64_t Val = C->getValue()) // Don't break X / 0
1043 if (isPowerOf2_64(Val)) {
1044 uint64_t C = Log2_64(Val);
1045 return new ShiftInst(Instruction::Shr, Op0,
1046 ConstantUInt::get(Type::UByteTy, C));
1050 if (RHS->getType()->isSigned())
1051 if (Value *LHSNeg = dyn_castNegVal(Op0))
1052 return BinaryOperator::createDiv(LHSNeg, ConstantExpr::getNeg(RHS));
1054 if (!RHS->isNullValue()) {
1055 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1056 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
1058 if (isa<PHINode>(Op0))
1059 if (Instruction *NV = FoldOpIntoPhi(I))
1064 // If this is 'udiv X, (Cond ? C1, C2)' where C1&C2 are powers of two,
1065 // transform this into: '(Cond ? (udiv X, C1) : (udiv X, C2))'.
1066 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1067 if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
1068 if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
1069 if (STO->getValue() == 0) { // Couldn't be this argument.
1070 I.setOperand(1, SFO);
1072 } else if (SFO->getValue() == 0) {
1073 I.setOperand(1, STO);
1077 uint64_t TVA = STO->getValue(), FVA = SFO->getValue();
1078 if (isPowerOf2_64(TVA) && isPowerOf2_64(FVA)) {
1079 unsigned TSA = Log2_64(TVA), FSA = Log2_64(FVA);
1080 Constant *TC = ConstantUInt::get(Type::UByteTy, TSA);
1081 Instruction *TSI = new ShiftInst(Instruction::Shr, Op0,
1082 TC, SI->getName()+".t");
1083 TSI = InsertNewInstBefore(TSI, I);
1085 Constant *FC = ConstantUInt::get(Type::UByteTy, FSA);
1086 Instruction *FSI = new ShiftInst(Instruction::Shr, Op0,
1087 FC, SI->getName()+".f");
1088 FSI = InsertNewInstBefore(FSI, I);
1089 return new SelectInst(SI->getOperand(0), TSI, FSI);
1093 // 0 / X == 0, we don't need to preserve faults!
1094 if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
1095 if (LHS->equalsInt(0))
1096 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1102 Instruction *InstCombiner::visitRem(BinaryOperator &I) {
1103 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1104 if (I.getType()->isSigned())
1105 if (Value *RHSNeg = dyn_castNegVal(Op1))
1106 if (!isa<ConstantSInt>(RHSNeg) ||
1107 cast<ConstantSInt>(RHSNeg)->getValue() > 0) {
1109 AddUsesToWorkList(I);
1110 I.setOperand(1, RHSNeg);
1114 if (isa<UndefValue>(Op0)) // undef % X -> 0
1115 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1116 if (isa<UndefValue>(Op1))
1117 return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
1119 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
1120 if (RHS->equalsInt(1)) // X % 1 == 0
1121 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1123 // Check to see if this is an unsigned remainder with an exact power of 2,
1124 // if so, convert to a bitwise and.
1125 if (ConstantUInt *C = dyn_cast<ConstantUInt>(RHS))
1126 if (uint64_t Val = C->getValue()) // Don't break X % 0 (divide by zero)
1127 if (!(Val & (Val-1))) // Power of 2
1128 return BinaryOperator::createAnd(Op0,
1129 ConstantUInt::get(I.getType(), Val-1));
1131 if (!RHS->isNullValue()) {
1132 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1133 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
1135 if (isa<PHINode>(Op0))
1136 if (Instruction *NV = FoldOpIntoPhi(I))
1141 // If this is 'urem X, (Cond ? C1, C2)' where C1&C2 are powers of two,
1142 // transform this into: '(Cond ? (urem X, C1) : (urem X, C2))'.
1143 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1144 if (ConstantUInt *STO = dyn_cast<ConstantUInt>(SI->getOperand(1)))
1145 if (ConstantUInt *SFO = dyn_cast<ConstantUInt>(SI->getOperand(2))) {
1146 if (STO->getValue() == 0) { // Couldn't be this argument.
1147 I.setOperand(1, SFO);
1149 } else if (SFO->getValue() == 0) {
1150 I.setOperand(1, STO);
1154 if (!(STO->getValue() & (STO->getValue()-1)) &&
1155 !(SFO->getValue() & (SFO->getValue()-1))) {
1156 Value *TrueAnd = InsertNewInstBefore(BinaryOperator::createAnd(Op0,
1157 SubOne(STO), SI->getName()+".t"), I);
1158 Value *FalseAnd = InsertNewInstBefore(BinaryOperator::createAnd(Op0,
1159 SubOne(SFO), SI->getName()+".f"), I);
1160 return new SelectInst(SI->getOperand(0), TrueAnd, FalseAnd);
1164 // 0 % X == 0, we don't need to preserve faults!
1165 if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
1166 if (LHS->equalsInt(0))
1167 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1172 // isMaxValueMinusOne - return true if this is Max-1
1173 static bool isMaxValueMinusOne(const ConstantInt *C) {
1174 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C)) {
1175 // Calculate -1 casted to the right type...
1176 unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
1177 uint64_t Val = ~0ULL; // All ones
1178 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
1179 return CU->getValue() == Val-1;
1182 const ConstantSInt *CS = cast<ConstantSInt>(C);
1184 // Calculate 0111111111..11111
1185 unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
1186 int64_t Val = INT64_MAX; // All ones
1187 Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
1188 return CS->getValue() == Val-1;
1191 // isMinValuePlusOne - return true if this is Min+1
1192 static bool isMinValuePlusOne(const ConstantInt *C) {
1193 if (const ConstantUInt *CU = dyn_cast<ConstantUInt>(C))
1194 return CU->getValue() == 1;
1196 const ConstantSInt *CS = cast<ConstantSInt>(C);
1198 // Calculate 1111111111000000000000
1199 unsigned TypeBits = C->getType()->getPrimitiveSizeInBits();
1200 int64_t Val = -1; // All ones
1201 Val <<= TypeBits-1; // Shift over to the right spot
1202 return CS->getValue() == Val+1;
1205 // isOneBitSet - Return true if there is exactly one bit set in the specified
1207 static bool isOneBitSet(const ConstantInt *CI) {
1208 uint64_t V = CI->getRawValue();
1209 return V && (V & (V-1)) == 0;
1212 #if 0 // Currently unused
1213 // isLowOnes - Return true if the constant is of the form 0+1+.
1214 static bool isLowOnes(const ConstantInt *CI) {
1215 uint64_t V = CI->getRawValue();
1217 // There won't be bits set in parts that the type doesn't contain.
1218 V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
1220 uint64_t U = V+1; // If it is low ones, this should be a power of two.
1221 return U && V && (U & V) == 0;
1225 // isHighOnes - Return true if the constant is of the form 1+0+.
1226 // This is the same as lowones(~X).
1227 static bool isHighOnes(const ConstantInt *CI) {
1228 uint64_t V = ~CI->getRawValue();
1229 if (~V == 0) return false; // 0's does not match "1+"
1231 // There won't be bits set in parts that the type doesn't contain.
1232 V &= ConstantInt::getAllOnesValue(CI->getType())->getRawValue();
1234 uint64_t U = V+1; // If it is low ones, this should be a power of two.
1235 return U && V && (U & V) == 0;
1239 /// getSetCondCode - Encode a setcc opcode into a three bit mask. These bits
1240 /// are carefully arranged to allow folding of expressions such as:
1242 /// (A < B) | (A > B) --> (A != B)
1244 /// Bit value '4' represents that the comparison is true if A > B, bit value '2'
1245 /// represents that the comparison is true if A == B, and bit value '1' is true
1248 static unsigned getSetCondCode(const SetCondInst *SCI) {
1249 switch (SCI->getOpcode()) {
1251 case Instruction::SetGT: return 1;
1252 case Instruction::SetEQ: return 2;
1253 case Instruction::SetGE: return 3;
1254 case Instruction::SetLT: return 4;
1255 case Instruction::SetNE: return 5;
1256 case Instruction::SetLE: return 6;
1259 assert(0 && "Invalid SetCC opcode!");
1264 /// getSetCCValue - This is the complement of getSetCondCode, which turns an
1265 /// opcode and two operands into either a constant true or false, or a brand new
1266 /// SetCC instruction.
1267 static Value *getSetCCValue(unsigned Opcode, Value *LHS, Value *RHS) {
1269 case 0: return ConstantBool::False;
1270 case 1: return new SetCondInst(Instruction::SetGT, LHS, RHS);
1271 case 2: return new SetCondInst(Instruction::SetEQ, LHS, RHS);
1272 case 3: return new SetCondInst(Instruction::SetGE, LHS, RHS);
1273 case 4: return new SetCondInst(Instruction::SetLT, LHS, RHS);
1274 case 5: return new SetCondInst(Instruction::SetNE, LHS, RHS);
1275 case 6: return new SetCondInst(Instruction::SetLE, LHS, RHS);
1276 case 7: return ConstantBool::True;
1277 default: assert(0 && "Illegal SetCCCode!"); return 0;
1281 // FoldSetCCLogical - Implements (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1282 struct FoldSetCCLogical {
1285 FoldSetCCLogical(InstCombiner &ic, SetCondInst *SCI)
1286 : IC(ic), LHS(SCI->getOperand(0)), RHS(SCI->getOperand(1)) {}
1287 bool shouldApply(Value *V) const {
1288 if (SetCondInst *SCI = dyn_cast<SetCondInst>(V))
1289 return (SCI->getOperand(0) == LHS && SCI->getOperand(1) == RHS ||
1290 SCI->getOperand(0) == RHS && SCI->getOperand(1) == LHS);
1293 Instruction *apply(BinaryOperator &Log) const {
1294 SetCondInst *SCI = cast<SetCondInst>(Log.getOperand(0));
1295 if (SCI->getOperand(0) != LHS) {
1296 assert(SCI->getOperand(1) == LHS);
1297 SCI->swapOperands(); // Swap the LHS and RHS of the SetCC
1300 unsigned LHSCode = getSetCondCode(SCI);
1301 unsigned RHSCode = getSetCondCode(cast<SetCondInst>(Log.getOperand(1)));
1303 switch (Log.getOpcode()) {
1304 case Instruction::And: Code = LHSCode & RHSCode; break;
1305 case Instruction::Or: Code = LHSCode | RHSCode; break;
1306 case Instruction::Xor: Code = LHSCode ^ RHSCode; break;
1307 default: assert(0 && "Illegal logical opcode!"); return 0;
1310 Value *RV = getSetCCValue(Code, LHS, RHS);
1311 if (Instruction *I = dyn_cast<Instruction>(RV))
1313 // Otherwise, it's a constant boolean value...
1314 return IC.ReplaceInstUsesWith(Log, RV);
1319 /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use
1320 /// this predicate to simplify operations downstream. V and Mask are known to
1321 /// be the same type.
1322 static bool MaskedValueIsZero(Value *V, ConstantIntegral *Mask) {
1323 // Note, we cannot consider 'undef' to be "IsZero" here. The problem is that
1324 // we cannot optimize based on the assumption that it is zero without changing
1325 // to to an explicit zero. If we don't change it to zero, other code could
1326 // optimized based on the contradictory assumption that it is non-zero.
1327 // Because instcombine aggressively folds operations with undef args anyway,
1328 // this won't lose us code quality.
1329 if (Mask->isNullValue())
1331 if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(V))
1332 return ConstantExpr::getAnd(CI, Mask)->isNullValue();
1334 if (Instruction *I = dyn_cast<Instruction>(V)) {
1335 switch (I->getOpcode()) {
1336 case Instruction::And:
1337 // (X & C1) & C2 == 0 iff C1 & C2 == 0.
1338 if (ConstantIntegral *CI = dyn_cast<ConstantIntegral>(I->getOperand(1)))
1339 if (ConstantExpr::getAnd(CI, Mask)->isNullValue())
1342 case Instruction::Or:
1343 // If the LHS and the RHS are MaskedValueIsZero, the result is also zero.
1344 return MaskedValueIsZero(I->getOperand(1), Mask) &&
1345 MaskedValueIsZero(I->getOperand(0), Mask);
1346 case Instruction::Select:
1347 // If the T and F values are MaskedValueIsZero, the result is also zero.
1348 return MaskedValueIsZero(I->getOperand(2), Mask) &&
1349 MaskedValueIsZero(I->getOperand(1), Mask);
1350 case Instruction::Cast: {
1351 const Type *SrcTy = I->getOperand(0)->getType();
1352 if (SrcTy == Type::BoolTy)
1353 return (Mask->getRawValue() & 1) == 0;
1355 if (SrcTy->isInteger()) {
1356 // (cast <ty> X to int) & C2 == 0 iff <ty> could not have contained C2.
1357 if (SrcTy->isUnsigned() && // Only handle zero ext.
1358 ConstantExpr::getCast(Mask, SrcTy)->isNullValue())
1361 // If this is a noop cast, recurse.
1362 if ((SrcTy->isSigned() && SrcTy->getUnsignedVersion() == I->getType())||
1363 SrcTy->getSignedVersion() == I->getType()) {
1365 ConstantExpr::getCast(Mask, I->getOperand(0)->getType());
1366 return MaskedValueIsZero(I->getOperand(0),
1367 cast<ConstantIntegral>(NewMask));
1372 case Instruction::Shl:
1373 // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0
1374 if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
1375 return MaskedValueIsZero(I->getOperand(0),
1376 cast<ConstantIntegral>(ConstantExpr::getUShr(Mask, SA)));
1378 case Instruction::Shr:
1379 // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0
1380 if (ConstantUInt *SA = dyn_cast<ConstantUInt>(I->getOperand(1)))
1381 if (I->getType()->isUnsigned()) {
1382 Constant *C1 = ConstantIntegral::getAllOnesValue(I->getType());
1383 C1 = ConstantExpr::getShr(C1, SA);
1384 C1 = ConstantExpr::getAnd(C1, Mask);
1385 if (C1->isNullValue())
1395 // OptAndOp - This handles expressions of the form ((val OP C1) & C2). Where
1396 // the Op parameter is 'OP', OpRHS is 'C1', and AndRHS is 'C2'. Op is
1397 // guaranteed to be either a shift instruction or a binary operator.
1398 Instruction *InstCombiner::OptAndOp(Instruction *Op,
1399 ConstantIntegral *OpRHS,
1400 ConstantIntegral *AndRHS,
1401 BinaryOperator &TheAnd) {
1402 Value *X = Op->getOperand(0);
1403 Constant *Together = 0;
1404 if (!isa<ShiftInst>(Op))
1405 Together = ConstantExpr::getAnd(AndRHS, OpRHS);
1407 switch (Op->getOpcode()) {
1408 case Instruction::Xor:
1409 if (Op->hasOneUse()) {
1410 // (X ^ C1) & C2 --> (X & C2) ^ (C1&C2)
1411 std::string OpName = Op->getName(); Op->setName("");
1412 Instruction *And = BinaryOperator::createAnd(X, AndRHS, OpName);
1413 InsertNewInstBefore(And, TheAnd);
1414 return BinaryOperator::createXor(And, Together);
1417 case Instruction::Or:
1418 if (Together == AndRHS) // (X | C) & C --> C
1419 return ReplaceInstUsesWith(TheAnd, AndRHS);
1421 if (Op->hasOneUse() && Together != OpRHS) {
1422 // (X | C1) & C2 --> (X | (C1&C2)) & C2
1423 std::string Op0Name = Op->getName(); Op->setName("");
1424 Instruction *Or = BinaryOperator::createOr(X, Together, Op0Name);
1425 InsertNewInstBefore(Or, TheAnd);
1426 return BinaryOperator::createAnd(Or, AndRHS);
1429 case Instruction::Add:
1430 if (Op->hasOneUse()) {
1431 // Adding a one to a single bit bit-field should be turned into an XOR
1432 // of the bit. First thing to check is to see if this AND is with a
1433 // single bit constant.
1434 uint64_t AndRHSV = cast<ConstantInt>(AndRHS)->getRawValue();
1436 // Clear bits that are not part of the constant.
1437 AndRHSV &= ~0ULL >> (64-AndRHS->getType()->getPrimitiveSizeInBits());
1439 // If there is only one bit set...
1440 if (isOneBitSet(cast<ConstantInt>(AndRHS))) {
1441 // Ok, at this point, we know that we are masking the result of the
1442 // ADD down to exactly one bit. If the constant we are adding has
1443 // no bits set below this bit, then we can eliminate the ADD.
1444 uint64_t AddRHS = cast<ConstantInt>(OpRHS)->getRawValue();
1446 // Check to see if any bits below the one bit set in AndRHSV are set.
1447 if ((AddRHS & (AndRHSV-1)) == 0) {
1448 // If not, the only thing that can effect the output of the AND is
1449 // the bit specified by AndRHSV. If that bit is set, the effect of
1450 // the XOR is to toggle the bit. If it is clear, then the ADD has
1452 if ((AddRHS & AndRHSV) == 0) { // Bit is not set, noop
1453 TheAnd.setOperand(0, X);
1456 std::string Name = Op->getName(); Op->setName("");
1457 // Pull the XOR out of the AND.
1458 Instruction *NewAnd = BinaryOperator::createAnd(X, AndRHS, Name);
1459 InsertNewInstBefore(NewAnd, TheAnd);
1460 return BinaryOperator::createXor(NewAnd, AndRHS);
1467 case Instruction::Shl: {
1468 // We know that the AND will not produce any of the bits shifted in, so if
1469 // the anded constant includes them, clear them now!
1471 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1472 Constant *ShlMask = ConstantExpr::getShl(AllOne, OpRHS);
1473 Constant *CI = ConstantExpr::getAnd(AndRHS, ShlMask);
1475 if (CI == ShlMask) { // Masking out bits that the shift already masks
1476 return ReplaceInstUsesWith(TheAnd, Op); // No need for the and.
1477 } else if (CI != AndRHS) { // Reducing bits set in and.
1478 TheAnd.setOperand(1, CI);
1483 case Instruction::Shr:
1484 // We know that the AND will not produce any of the bits shifted in, so if
1485 // the anded constant includes them, clear them now! This only applies to
1486 // unsigned shifts, because a signed shr may bring in set bits!
1488 if (AndRHS->getType()->isUnsigned()) {
1489 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1490 Constant *ShrMask = ConstantExpr::getShr(AllOne, OpRHS);
1491 Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
1493 if (CI == ShrMask) { // Masking out bits that the shift already masks.
1494 return ReplaceInstUsesWith(TheAnd, Op);
1495 } else if (CI != AndRHS) {
1496 TheAnd.setOperand(1, CI); // Reduce bits set in and cst.
1499 } else { // Signed shr.
1500 // See if this is shifting in some sign extension, then masking it out
1502 if (Op->hasOneUse()) {
1503 Constant *AllOne = ConstantIntegral::getAllOnesValue(AndRHS->getType());
1504 Constant *ShrMask = ConstantExpr::getUShr(AllOne, OpRHS);
1505 Constant *CI = ConstantExpr::getAnd(AndRHS, ShrMask);
1506 if (CI == AndRHS) { // Masking out bits shifted in.
1507 // Make the argument unsigned.
1508 Value *ShVal = Op->getOperand(0);
1509 ShVal = InsertCastBefore(ShVal,
1510 ShVal->getType()->getUnsignedVersion(),
1512 ShVal = InsertNewInstBefore(new ShiftInst(Instruction::Shr, ShVal,
1513 OpRHS, Op->getName()),
1515 Value *AndRHS2 = ConstantExpr::getCast(AndRHS, ShVal->getType());
1516 ShVal = InsertNewInstBefore(BinaryOperator::createAnd(ShVal, AndRHS2,
1519 return new CastInst(ShVal, Op->getType());
1529 /// InsertRangeTest - Emit a computation of: (V >= Lo && V < Hi) if Inside is
1530 /// true, otherwise (V < Lo || V >= Hi). In pratice, we emit the more efficient
1531 /// (V-Lo) <u Hi-Lo. This method expects that Lo <= Hi. IB is the location to
1532 /// insert new instructions.
1533 Instruction *InstCombiner::InsertRangeTest(Value *V, Constant *Lo, Constant *Hi,
1534 bool Inside, Instruction &IB) {
1535 assert(cast<ConstantBool>(ConstantExpr::getSetLE(Lo, Hi))->getValue() &&
1536 "Lo is not <= Hi in range emission code!");
1538 if (Lo == Hi) // Trivially false.
1539 return new SetCondInst(Instruction::SetNE, V, V);
1540 if (cast<ConstantIntegral>(Lo)->isMinValue())
1541 return new SetCondInst(Instruction::SetLT, V, Hi);
1543 Constant *AddCST = ConstantExpr::getNeg(Lo);
1544 Instruction *Add = BinaryOperator::createAdd(V, AddCST,V->getName()+".off");
1545 InsertNewInstBefore(Add, IB);
1546 // Convert to unsigned for the comparison.
1547 const Type *UnsType = Add->getType()->getUnsignedVersion();
1548 Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
1549 AddCST = ConstantExpr::getAdd(AddCST, Hi);
1550 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1551 return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
1554 if (Lo == Hi) // Trivially true.
1555 return new SetCondInst(Instruction::SetEQ, V, V);
1557 Hi = SubOne(cast<ConstantInt>(Hi));
1558 if (cast<ConstantIntegral>(Lo)->isMinValue()) // V < 0 || V >= Hi ->'V > Hi-1'
1559 return new SetCondInst(Instruction::SetGT, V, Hi);
1561 // Emit X-Lo > Hi-Lo-1
1562 Constant *AddCST = ConstantExpr::getNeg(Lo);
1563 Instruction *Add = BinaryOperator::createAdd(V, AddCST, V->getName()+".off");
1564 InsertNewInstBefore(Add, IB);
1565 // Convert to unsigned for the comparison.
1566 const Type *UnsType = Add->getType()->getUnsignedVersion();
1567 Value *OffsetVal = InsertCastBefore(Add, UnsType, IB);
1568 AddCST = ConstantExpr::getAdd(AddCST, Hi);
1569 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1570 return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
1574 Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
1575 bool Changed = SimplifyCommutative(I);
1576 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1578 if (isa<UndefValue>(Op1)) // X & undef -> 0
1579 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1583 return ReplaceInstUsesWith(I, Op1);
1585 if (ConstantIntegral *AndRHS = dyn_cast<ConstantIntegral>(Op1)) {
1587 if (AndRHS->isAllOnesValue())
1588 return ReplaceInstUsesWith(I, Op0);
1590 if (MaskedValueIsZero(Op0, AndRHS)) // LHS & RHS == 0
1591 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1593 // If the mask is not masking out any bits, there is no reason to do the
1594 // and in the first place.
1595 ConstantIntegral *NotAndRHS =
1596 cast<ConstantIntegral>(ConstantExpr::getNot(AndRHS));
1597 if (MaskedValueIsZero(Op0, NotAndRHS))
1598 return ReplaceInstUsesWith(I, Op0);
1600 // Optimize a variety of ((val OP C1) & C2) combinations...
1601 if (isa<BinaryOperator>(Op0) || isa<ShiftInst>(Op0)) {
1602 Instruction *Op0I = cast<Instruction>(Op0);
1603 Value *Op0LHS = Op0I->getOperand(0);
1604 Value *Op0RHS = Op0I->getOperand(1);
1605 switch (Op0I->getOpcode()) {
1606 case Instruction::Xor:
1607 case Instruction::Or:
1608 // (X ^ V) & C2 --> (X & C2) iff (V & C2) == 0
1609 // (X | V) & C2 --> (X & C2) iff (V & C2) == 0
1610 if (MaskedValueIsZero(Op0LHS, AndRHS))
1611 return BinaryOperator::createAnd(Op0RHS, AndRHS);
1612 if (MaskedValueIsZero(Op0RHS, AndRHS))
1613 return BinaryOperator::createAnd(Op0LHS, AndRHS);
1615 // If the mask is only needed on one incoming arm, push it up.
1616 if (Op0I->hasOneUse()) {
1617 if (MaskedValueIsZero(Op0LHS, NotAndRHS)) {
1618 // Not masking anything out for the LHS, move to RHS.
1619 Instruction *NewRHS = BinaryOperator::createAnd(Op0RHS, AndRHS,
1620 Op0RHS->getName()+".masked");
1621 InsertNewInstBefore(NewRHS, I);
1622 return BinaryOperator::create(
1623 cast<BinaryOperator>(Op0I)->getOpcode(), Op0LHS, NewRHS);
1625 if (!isa<Constant>(NotAndRHS) &&
1626 MaskedValueIsZero(Op0RHS, NotAndRHS)) {
1627 // Not masking anything out for the RHS, move to LHS.
1628 Instruction *NewLHS = BinaryOperator::createAnd(Op0LHS, AndRHS,
1629 Op0LHS->getName()+".masked");
1630 InsertNewInstBefore(NewLHS, I);
1631 return BinaryOperator::create(
1632 cast<BinaryOperator>(Op0I)->getOpcode(), NewLHS, Op0RHS);
1637 case Instruction::And:
1638 // (X & V) & C2 --> 0 iff (V & C2) == 0
1639 if (MaskedValueIsZero(Op0LHS, AndRHS) ||
1640 MaskedValueIsZero(Op0RHS, AndRHS))
1641 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1645 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
1646 if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
1648 } else if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
1649 const Type *SrcTy = CI->getOperand(0)->getType();
1651 // If this is an integer truncation or change from signed-to-unsigned, and
1652 // if the source is an and/or with immediate, transform it. This
1653 // frequently occurs for bitfield accesses.
1654 if (Instruction *CastOp = dyn_cast<Instruction>(CI->getOperand(0))) {
1655 if (SrcTy->getPrimitiveSizeInBits() >=
1656 I.getType()->getPrimitiveSizeInBits() &&
1657 CastOp->getNumOperands() == 2)
1658 if (ConstantInt *AndCI =dyn_cast<ConstantInt>(CastOp->getOperand(1)))
1659 if (CastOp->getOpcode() == Instruction::And) {
1660 // Change: and (cast (and X, C1) to T), C2
1661 // into : and (cast X to T), trunc(C1)&C2
1662 // This will folds the two ands together, which may allow other
1664 Instruction *NewCast =
1665 new CastInst(CastOp->getOperand(0), I.getType(),
1666 CastOp->getName()+".shrunk");
1667 NewCast = InsertNewInstBefore(NewCast, I);
1669 Constant *C3=ConstantExpr::getCast(AndCI, I.getType());//trunc(C1)
1670 C3 = ConstantExpr::getAnd(C3, AndRHS); // trunc(C1)&C2
1671 return BinaryOperator::createAnd(NewCast, C3);
1672 } else if (CastOp->getOpcode() == Instruction::Or) {
1673 // Change: and (cast (or X, C1) to T), C2
1674 // into : trunc(C1)&C2 iff trunc(C1)&C2 == C2
1675 Constant *C3=ConstantExpr::getCast(AndCI, I.getType());//trunc(C1)
1676 if (ConstantExpr::getAnd(C3, AndRHS) == AndRHS) // trunc(C1)&C2
1677 return ReplaceInstUsesWith(I, AndRHS);
1682 // If this is an integer sign or zero extension instruction.
1683 if (SrcTy->isIntegral() &&
1684 SrcTy->getPrimitiveSizeInBits() <
1685 CI->getType()->getPrimitiveSizeInBits()) {
1687 if (SrcTy->isUnsigned()) {
1688 // See if this and is clearing out bits that are known to be zero
1689 // anyway (due to the zero extension).
1690 Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy);
1691 Mask = ConstantExpr::getZeroExtend(Mask, CI->getType());
1692 Constant *Result = ConstantExpr::getAnd(Mask, AndRHS);
1693 if (Result == Mask) // The "and" isn't doing anything, remove it.
1694 return ReplaceInstUsesWith(I, CI);
1695 if (Result != AndRHS) { // Reduce the and RHS constant.
1696 I.setOperand(1, Result);
1701 if (CI->hasOneUse() && SrcTy->isInteger()) {
1702 // We can only do this if all of the sign bits brought in are masked
1703 // out. Compute this by first getting 0000011111, then inverting
1705 Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy);
1706 Mask = ConstantExpr::getZeroExtend(Mask, CI->getType());
1707 Mask = ConstantExpr::getNot(Mask); // 1's in the new bits.
1708 if (ConstantExpr::getAnd(Mask, AndRHS)->isNullValue()) {
1709 // If the and is clearing all of the sign bits, change this to a
1710 // zero extension cast. To do this, cast the cast input to
1711 // unsigned, then to the requested size.
1712 Value *CastOp = CI->getOperand(0);
1714 new CastInst(CastOp, CastOp->getType()->getUnsignedVersion(),
1715 CI->getName()+".uns");
1716 NC = InsertNewInstBefore(NC, I);
1717 // Finally, insert a replacement for CI.
1718 NC = new CastInst(NC, CI->getType(), CI->getName());
1720 NC = InsertNewInstBefore(NC, I);
1721 WorkList.push_back(CI); // Delete CI later.
1722 I.setOperand(0, NC);
1723 return &I; // The AND operand was modified.
1730 // Try to fold constant and into select arguments.
1731 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1732 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
1734 if (isa<PHINode>(Op0))
1735 if (Instruction *NV = FoldOpIntoPhi(I))
1739 Value *Op0NotVal = dyn_castNotVal(Op0);
1740 Value *Op1NotVal = dyn_castNotVal(Op1);
1742 if (Op0NotVal == Op1 || Op1NotVal == Op0) // A & ~A == ~A & A == 0
1743 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
1745 // (~A & ~B) == (~(A | B)) - De Morgan's Law
1746 if (Op0NotVal && Op1NotVal && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1747 Instruction *Or = BinaryOperator::createOr(Op0NotVal, Op1NotVal,
1748 I.getName()+".demorgan");
1749 InsertNewInstBefore(Or, I);
1750 return BinaryOperator::createNot(Or);
1753 if (SetCondInst *RHS = dyn_cast<SetCondInst>(Op1)) {
1754 // (setcc1 A, B) & (setcc2 A, B) --> (setcc3 A, B)
1755 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1758 Value *LHSVal, *RHSVal;
1759 ConstantInt *LHSCst, *RHSCst;
1760 Instruction::BinaryOps LHSCC, RHSCC;
1761 if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
1762 if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
1763 if (LHSVal == RHSVal && // Found (X setcc C1) & (X setcc C2)
1764 // Set[GL]E X, CST is folded to Set[GL]T elsewhere.
1765 LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
1766 RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
1767 // Ensure that the larger constant is on the RHS.
1768 Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
1769 SetCondInst *LHS = cast<SetCondInst>(Op0);
1770 if (cast<ConstantBool>(Cmp)->getValue()) {
1771 std::swap(LHS, RHS);
1772 std::swap(LHSCst, RHSCst);
1773 std::swap(LHSCC, RHSCC);
1776 // At this point, we know we have have two setcc instructions
1777 // comparing a value against two constants and and'ing the result
1778 // together. Because of the above check, we know that we only have
1779 // SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
1780 // FoldSetCCLogical check above), that the two constants are not
1782 assert(LHSCst != RHSCst && "Compares not folded above?");
1785 default: assert(0 && "Unknown integer condition code!");
1786 case Instruction::SetEQ:
1788 default: assert(0 && "Unknown integer condition code!");
1789 case Instruction::SetEQ: // (X == 13 & X == 15) -> false
1790 case Instruction::SetGT: // (X == 13 & X > 15) -> false
1791 return ReplaceInstUsesWith(I, ConstantBool::False);
1792 case Instruction::SetNE: // (X == 13 & X != 15) -> X == 13
1793 case Instruction::SetLT: // (X == 13 & X < 15) -> X == 13
1794 return ReplaceInstUsesWith(I, LHS);
1796 case Instruction::SetNE:
1798 default: assert(0 && "Unknown integer condition code!");
1799 case Instruction::SetLT:
1800 if (LHSCst == SubOne(RHSCst)) // (X != 13 & X < 14) -> X < 13
1801 return new SetCondInst(Instruction::SetLT, LHSVal, LHSCst);
1802 break; // (X != 13 & X < 15) -> no change
1803 case Instruction::SetEQ: // (X != 13 & X == 15) -> X == 15
1804 case Instruction::SetGT: // (X != 13 & X > 15) -> X > 15
1805 return ReplaceInstUsesWith(I, RHS);
1806 case Instruction::SetNE:
1807 if (LHSCst == SubOne(RHSCst)) {// (X != 13 & X != 14) -> X-13 >u 1
1808 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
1809 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
1810 LHSVal->getName()+".off");
1811 InsertNewInstBefore(Add, I);
1812 const Type *UnsType = Add->getType()->getUnsignedVersion();
1813 Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
1814 AddCST = ConstantExpr::getSub(RHSCst, LHSCst);
1815 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1816 return new SetCondInst(Instruction::SetGT, OffsetVal, AddCST);
1818 break; // (X != 13 & X != 15) -> no change
1821 case Instruction::SetLT:
1823 default: assert(0 && "Unknown integer condition code!");
1824 case Instruction::SetEQ: // (X < 13 & X == 15) -> false
1825 case Instruction::SetGT: // (X < 13 & X > 15) -> false
1826 return ReplaceInstUsesWith(I, ConstantBool::False);
1827 case Instruction::SetNE: // (X < 13 & X != 15) -> X < 13
1828 case Instruction::SetLT: // (X < 13 & X < 15) -> X < 13
1829 return ReplaceInstUsesWith(I, LHS);
1831 case Instruction::SetGT:
1833 default: assert(0 && "Unknown integer condition code!");
1834 case Instruction::SetEQ: // (X > 13 & X == 15) -> X > 13
1835 return ReplaceInstUsesWith(I, LHS);
1836 case Instruction::SetGT: // (X > 13 & X > 15) -> X > 15
1837 return ReplaceInstUsesWith(I, RHS);
1838 case Instruction::SetNE:
1839 if (RHSCst == AddOne(LHSCst)) // (X > 13 & X != 14) -> X > 14
1840 return new SetCondInst(Instruction::SetGT, LHSVal, RHSCst);
1841 break; // (X > 13 & X != 15) -> no change
1842 case Instruction::SetLT: // (X > 13 & X < 15) -> (X-14) <u 1
1843 return InsertRangeTest(LHSVal, AddOne(LHSCst), RHSCst, true, I);
1849 return Changed ? &I : 0;
1852 Instruction *InstCombiner::visitOr(BinaryOperator &I) {
1853 bool Changed = SimplifyCommutative(I);
1854 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1856 if (isa<UndefValue>(Op1))
1857 return ReplaceInstUsesWith(I, // X | undef -> -1
1858 ConstantIntegral::getAllOnesValue(I.getType()));
1860 // or X, X = X or X, 0 == X
1861 if (Op0 == Op1 || Op1 == Constant::getNullValue(I.getType()))
1862 return ReplaceInstUsesWith(I, Op0);
1865 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
1866 // If X is known to only contain bits that already exist in RHS, just
1867 // replace this instruction with RHS directly.
1868 if (MaskedValueIsZero(Op0,
1869 cast<ConstantIntegral>(ConstantExpr::getNot(RHS))))
1870 return ReplaceInstUsesWith(I, RHS);
1872 ConstantInt *C1; Value *X;
1873 // (X & C1) | C2 --> (X | C2) & (C1|C2)
1874 if (match(Op0, m_And(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
1875 Instruction *Or = BinaryOperator::createOr(X, RHS, Op0->getName());
1877 InsertNewInstBefore(Or, I);
1878 return BinaryOperator::createAnd(Or, ConstantExpr::getOr(RHS, C1));
1881 // (X ^ C1) | C2 --> (X | C2) ^ (C1&~C2)
1882 if (match(Op0, m_Xor(m_Value(X), m_ConstantInt(C1))) && isOnlyUse(Op0)) {
1883 std::string Op0Name = Op0->getName(); Op0->setName("");
1884 Instruction *Or = BinaryOperator::createOr(X, RHS, Op0Name);
1885 InsertNewInstBefore(Or, I);
1886 return BinaryOperator::createXor(Or,
1887 ConstantExpr::getAnd(C1, ConstantExpr::getNot(RHS)));
1890 // Try to fold constant and into select arguments.
1891 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1892 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
1894 if (isa<PHINode>(Op0))
1895 if (Instruction *NV = FoldOpIntoPhi(I))
1899 Value *A, *B; ConstantInt *C1, *C2;
1901 if (match(Op0, m_And(m_Value(A), m_Value(B))))
1902 if (A == Op1 || B == Op1) // (A & ?) | A --> A
1903 return ReplaceInstUsesWith(I, Op1);
1904 if (match(Op1, m_And(m_Value(A), m_Value(B))))
1905 if (A == Op0 || B == Op0) // A | (A & ?) --> A
1906 return ReplaceInstUsesWith(I, Op0);
1908 // (X^C)|Y -> (X|Y)^C iff Y&C == 0
1909 if (Op0->hasOneUse() && match(Op0, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
1910 MaskedValueIsZero(Op1, C1)) {
1911 Instruction *NOr = BinaryOperator::createOr(A, Op1, Op0->getName());
1913 return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
1916 // Y|(X^C) -> (X|Y)^C iff Y&C == 0
1917 if (Op1->hasOneUse() && match(Op1, m_Xor(m_Value(A), m_ConstantInt(C1))) &&
1918 MaskedValueIsZero(Op0, C1)) {
1919 Instruction *NOr = BinaryOperator::createOr(A, Op0, Op1->getName());
1921 return BinaryOperator::createXor(InsertNewInstBefore(NOr, I), C1);
1924 // (A & C1)|(A & C2) == A & (C1|C2)
1925 if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
1926 match(Op1, m_And(m_Value(B), m_ConstantInt(C2))) && A == B)
1927 return BinaryOperator::createAnd(A, ConstantExpr::getOr(C1, C2));
1929 if (match(Op0, m_Not(m_Value(A)))) { // ~A | Op1
1930 if (A == Op1) // ~A | A == -1
1931 return ReplaceInstUsesWith(I,
1932 ConstantIntegral::getAllOnesValue(I.getType()));
1936 // Note, A is still live here!
1937 if (match(Op1, m_Not(m_Value(B)))) { // Op0 | ~B
1939 return ReplaceInstUsesWith(I,
1940 ConstantIntegral::getAllOnesValue(I.getType()));
1942 // (~A | ~B) == (~(A & B)) - De Morgan's Law
1943 if (A && isOnlyUse(Op0) && isOnlyUse(Op1)) {
1944 Value *And = InsertNewInstBefore(BinaryOperator::createAnd(A, B,
1945 I.getName()+".demorgan"), I);
1946 return BinaryOperator::createNot(And);
1950 // (setcc1 A, B) | (setcc2 A, B) --> (setcc3 A, B)
1951 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1))) {
1952 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
1955 Value *LHSVal, *RHSVal;
1956 ConstantInt *LHSCst, *RHSCst;
1957 Instruction::BinaryOps LHSCC, RHSCC;
1958 if (match(Op0, m_SetCond(LHSCC, m_Value(LHSVal), m_ConstantInt(LHSCst))))
1959 if (match(RHS, m_SetCond(RHSCC, m_Value(RHSVal), m_ConstantInt(RHSCst))))
1960 if (LHSVal == RHSVal && // Found (X setcc C1) | (X setcc C2)
1961 // Set[GL]E X, CST is folded to Set[GL]T elsewhere.
1962 LHSCC != Instruction::SetGE && LHSCC != Instruction::SetLE &&
1963 RHSCC != Instruction::SetGE && RHSCC != Instruction::SetLE) {
1964 // Ensure that the larger constant is on the RHS.
1965 Constant *Cmp = ConstantExpr::getSetGT(LHSCst, RHSCst);
1966 SetCondInst *LHS = cast<SetCondInst>(Op0);
1967 if (cast<ConstantBool>(Cmp)->getValue()) {
1968 std::swap(LHS, RHS);
1969 std::swap(LHSCst, RHSCst);
1970 std::swap(LHSCC, RHSCC);
1973 // At this point, we know we have have two setcc instructions
1974 // comparing a value against two constants and or'ing the result
1975 // together. Because of the above check, we know that we only have
1976 // SetEQ, SetNE, SetLT, and SetGT here. We also know (from the
1977 // FoldSetCCLogical check above), that the two constants are not
1979 assert(LHSCst != RHSCst && "Compares not folded above?");
1982 default: assert(0 && "Unknown integer condition code!");
1983 case Instruction::SetEQ:
1985 default: assert(0 && "Unknown integer condition code!");
1986 case Instruction::SetEQ:
1987 if (LHSCst == SubOne(RHSCst)) {// (X == 13 | X == 14) -> X-13 <u 2
1988 Constant *AddCST = ConstantExpr::getNeg(LHSCst);
1989 Instruction *Add = BinaryOperator::createAdd(LHSVal, AddCST,
1990 LHSVal->getName()+".off");
1991 InsertNewInstBefore(Add, I);
1992 const Type *UnsType = Add->getType()->getUnsignedVersion();
1993 Value *OffsetVal = InsertCastBefore(Add, UnsType, I);
1994 AddCST = ConstantExpr::getSub(AddOne(RHSCst), LHSCst);
1995 AddCST = ConstantExpr::getCast(AddCST, UnsType);
1996 return new SetCondInst(Instruction::SetLT, OffsetVal, AddCST);
1998 break; // (X == 13 | X == 15) -> no change
2000 case Instruction::SetGT: // (X == 13 | X > 14) -> no change
2002 case Instruction::SetNE: // (X == 13 | X != 15) -> X != 15
2003 case Instruction::SetLT: // (X == 13 | X < 15) -> X < 15
2004 return ReplaceInstUsesWith(I, RHS);
2007 case Instruction::SetNE:
2009 default: assert(0 && "Unknown integer condition code!");
2010 case Instruction::SetEQ: // (X != 13 | X == 15) -> X != 13
2011 case Instruction::SetGT: // (X != 13 | X > 15) -> X != 13
2012 return ReplaceInstUsesWith(I, LHS);
2013 case Instruction::SetNE: // (X != 13 | X != 15) -> true
2014 case Instruction::SetLT: // (X != 13 | X < 15) -> true
2015 return ReplaceInstUsesWith(I, ConstantBool::True);
2018 case Instruction::SetLT:
2020 default: assert(0 && "Unknown integer condition code!");
2021 case Instruction::SetEQ: // (X < 13 | X == 14) -> no change
2023 case Instruction::SetGT: // (X < 13 | X > 15) -> (X-13) > 2
2024 return InsertRangeTest(LHSVal, LHSCst, AddOne(RHSCst), false, I);
2025 case Instruction::SetNE: // (X < 13 | X != 15) -> X != 15
2026 case Instruction::SetLT: // (X < 13 | X < 15) -> X < 15
2027 return ReplaceInstUsesWith(I, RHS);
2030 case Instruction::SetGT:
2032 default: assert(0 && "Unknown integer condition code!");
2033 case Instruction::SetEQ: // (X > 13 | X == 15) -> X > 13
2034 case Instruction::SetGT: // (X > 13 | X > 15) -> X > 13
2035 return ReplaceInstUsesWith(I, LHS);
2036 case Instruction::SetNE: // (X > 13 | X != 15) -> true
2037 case Instruction::SetLT: // (X > 13 | X < 15) -> true
2038 return ReplaceInstUsesWith(I, ConstantBool::True);
2043 return Changed ? &I : 0;
2046 // XorSelf - Implements: X ^ X --> 0
2049 XorSelf(Value *rhs) : RHS(rhs) {}
2050 bool shouldApply(Value *LHS) const { return LHS == RHS; }
2051 Instruction *apply(BinaryOperator &Xor) const {
2057 Instruction *InstCombiner::visitXor(BinaryOperator &I) {
2058 bool Changed = SimplifyCommutative(I);
2059 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2061 if (isa<UndefValue>(Op1))
2062 return ReplaceInstUsesWith(I, Op1); // X ^ undef -> undef
2064 // xor X, X = 0, even if X is nested in a sequence of Xor's.
2065 if (Instruction *Result = AssociativeOpt(I, XorSelf(Op1))) {
2066 assert(Result == &I && "AssociativeOpt didn't work?");
2067 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
2070 if (ConstantIntegral *RHS = dyn_cast<ConstantIntegral>(Op1)) {
2072 if (RHS->isNullValue())
2073 return ReplaceInstUsesWith(I, Op0);
2075 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0)) {
2076 // xor (setcc A, B), true = not (setcc A, B) = setncc A, B
2077 if (SetCondInst *SCI = dyn_cast<SetCondInst>(Op0I))
2078 if (RHS == ConstantBool::True && SCI->hasOneUse())
2079 return new SetCondInst(SCI->getInverseCondition(),
2080 SCI->getOperand(0), SCI->getOperand(1));
2082 // ~(c-X) == X-c-1 == X+(-c-1)
2083 if (Op0I->getOpcode() == Instruction::Sub && RHS->isAllOnesValue())
2084 if (Constant *Op0I0C = dyn_cast<Constant>(Op0I->getOperand(0))) {
2085 Constant *NegOp0I0C = ConstantExpr::getNeg(Op0I0C);
2086 Constant *ConstantRHS = ConstantExpr::getSub(NegOp0I0C,
2087 ConstantInt::get(I.getType(), 1));
2088 return BinaryOperator::createAdd(Op0I->getOperand(1), ConstantRHS);
2091 // ~(~X & Y) --> (X | ~Y)
2092 if (Op0I->getOpcode() == Instruction::And && RHS->isAllOnesValue()) {
2093 if (dyn_castNotVal(Op0I->getOperand(1))) Op0I->swapOperands();
2094 if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0))) {
2096 BinaryOperator::createNot(Op0I->getOperand(1),
2097 Op0I->getOperand(1)->getName()+".not");
2098 InsertNewInstBefore(NotY, I);
2099 return BinaryOperator::createOr(Op0NotVal, NotY);
2103 if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
2104 switch (Op0I->getOpcode()) {
2105 case Instruction::Add:
2106 // ~(X-c) --> (-c-1)-X
2107 if (RHS->isAllOnesValue()) {
2108 Constant *NegOp0CI = ConstantExpr::getNeg(Op0CI);
2109 return BinaryOperator::createSub(
2110 ConstantExpr::getSub(NegOp0CI,
2111 ConstantInt::get(I.getType(), 1)),
2112 Op0I->getOperand(0));
2115 case Instruction::And:
2116 // (X & C1) ^ C2 --> (X & C1) | C2 iff (C1&C2) == 0
2117 if (ConstantExpr::getAnd(RHS, Op0CI)->isNullValue())
2118 return BinaryOperator::createOr(Op0, RHS);
2120 case Instruction::Or:
2121 // (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
2122 if (ConstantExpr::getAnd(RHS, Op0CI) == RHS)
2123 return BinaryOperator::createAnd(Op0, ConstantExpr::getNot(RHS));
2129 // Try to fold constant and into select arguments.
2130 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
2131 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
2133 if (isa<PHINode>(Op0))
2134 if (Instruction *NV = FoldOpIntoPhi(I))
2138 if (Value *X = dyn_castNotVal(Op0)) // ~A ^ A == -1
2140 return ReplaceInstUsesWith(I,
2141 ConstantIntegral::getAllOnesValue(I.getType()));
2143 if (Value *X = dyn_castNotVal(Op1)) // A ^ ~A == -1
2145 return ReplaceInstUsesWith(I,
2146 ConstantIntegral::getAllOnesValue(I.getType()));
2148 if (Instruction *Op1I = dyn_cast<Instruction>(Op1))
2149 if (Op1I->getOpcode() == Instruction::Or) {
2150 if (Op1I->getOperand(0) == Op0) { // B^(B|A) == (A|B)^B
2151 cast<BinaryOperator>(Op1I)->swapOperands();
2153 std::swap(Op0, Op1);
2154 } else if (Op1I->getOperand(1) == Op0) { // B^(A|B) == (A|B)^B
2156 std::swap(Op0, Op1);
2158 } else if (Op1I->getOpcode() == Instruction::Xor) {
2159 if (Op0 == Op1I->getOperand(0)) // A^(A^B) == B
2160 return ReplaceInstUsesWith(I, Op1I->getOperand(1));
2161 else if (Op0 == Op1I->getOperand(1)) // A^(B^A) == B
2162 return ReplaceInstUsesWith(I, Op1I->getOperand(0));
2165 if (Instruction *Op0I = dyn_cast<Instruction>(Op0))
2166 if (Op0I->getOpcode() == Instruction::Or && Op0I->hasOneUse()) {
2167 if (Op0I->getOperand(0) == Op1) // (B|A)^B == (A|B)^B
2168 cast<BinaryOperator>(Op0I)->swapOperands();
2169 if (Op0I->getOperand(1) == Op1) { // (A|B)^B == A & ~B
2170 Value *NotB = InsertNewInstBefore(BinaryOperator::createNot(Op1,
2171 Op1->getName()+".not"), I);
2172 return BinaryOperator::createAnd(Op0I->getOperand(0), NotB);
2174 } else if (Op0I->getOpcode() == Instruction::Xor) {
2175 if (Op1 == Op0I->getOperand(0)) // (A^B)^A == B
2176 return ReplaceInstUsesWith(I, Op0I->getOperand(1));
2177 else if (Op1 == Op0I->getOperand(1)) // (B^A)^A == B
2178 return ReplaceInstUsesWith(I, Op0I->getOperand(0));
2181 // (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
2182 Value *A, *B; ConstantInt *C1, *C2;
2183 if (match(Op0, m_And(m_Value(A), m_ConstantInt(C1))) &&
2184 match(Op1, m_And(m_Value(B), m_ConstantInt(C2))) &&
2185 ConstantExpr::getAnd(C1, C2)->isNullValue())
2186 return BinaryOperator::createOr(Op0, Op1);
2188 // (setcc1 A, B) ^ (setcc2 A, B) --> (setcc3 A, B)
2189 if (SetCondInst *RHS = dyn_cast<SetCondInst>(I.getOperand(1)))
2190 if (Instruction *R = AssociativeOpt(I, FoldSetCCLogical(*this, RHS)))
2193 return Changed ? &I : 0;
2196 /// MulWithOverflow - Compute Result = In1*In2, returning true if the result
2197 /// overflowed for this type.
2198 static bool MulWithOverflow(ConstantInt *&Result, ConstantInt *In1,
2200 Result = cast<ConstantInt>(ConstantExpr::getMul(In1, In2));
2201 return !In2->isNullValue() && ConstantExpr::getDiv(Result, In2) != In1;
2204 static bool isPositive(ConstantInt *C) {
2205 return cast<ConstantSInt>(C)->getValue() >= 0;
2208 /// AddWithOverflow - Compute Result = In1+In2, returning true if the result
2209 /// overflowed for this type.
2210 static bool AddWithOverflow(ConstantInt *&Result, ConstantInt *In1,
2212 Result = cast<ConstantInt>(ConstantExpr::getAdd(In1, In2));
2214 if (In1->getType()->isUnsigned())
2215 return cast<ConstantUInt>(Result)->getValue() <
2216 cast<ConstantUInt>(In1)->getValue();
2217 if (isPositive(In1) != isPositive(In2))
2219 if (isPositive(In1))
2220 return cast<ConstantSInt>(Result)->getValue() <
2221 cast<ConstantSInt>(In1)->getValue();
2222 return cast<ConstantSInt>(Result)->getValue() >
2223 cast<ConstantSInt>(In1)->getValue();
2226 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
2227 /// code necessary to compute the offset from the base pointer (without adding
2228 /// in the base pointer). Return the result as a signed integer of intptr size.
2229 static Value *EmitGEPOffset(User *GEP, Instruction &I, InstCombiner &IC) {
2230 TargetData &TD = IC.getTargetData();
2231 gep_type_iterator GTI = gep_type_begin(GEP);
2232 const Type *UIntPtrTy = TD.getIntPtrType();
2233 const Type *SIntPtrTy = UIntPtrTy->getSignedVersion();
2234 Value *Result = Constant::getNullValue(SIntPtrTy);
2236 // Build a mask for high order bits.
2237 uint64_t PtrSizeMask = ~0ULL;
2238 PtrSizeMask >>= 64-(TD.getPointerSize()*8);
2240 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
2241 Value *Op = GEP->getOperand(i);
2242 uint64_t Size = TD.getTypeSize(GTI.getIndexedType()) & PtrSizeMask;
2243 Constant *Scale = ConstantExpr::getCast(ConstantUInt::get(UIntPtrTy, Size),
2245 if (Constant *OpC = dyn_cast<Constant>(Op)) {
2246 if (!OpC->isNullValue()) {
2247 OpC = ConstantExpr::getCast(OpC, SIntPtrTy);
2248 Scale = ConstantExpr::getMul(OpC, Scale);
2249 if (Constant *RC = dyn_cast<Constant>(Result))
2250 Result = ConstantExpr::getAdd(RC, Scale);
2252 // Emit an add instruction.
2253 Result = IC.InsertNewInstBefore(
2254 BinaryOperator::createAdd(Result, Scale,
2255 GEP->getName()+".offs"), I);
2259 // Convert to correct type.
2260 Op = IC.InsertNewInstBefore(new CastInst(Op, SIntPtrTy,
2261 Op->getName()+".c"), I);
2263 // We'll let instcombine(mul) convert this to a shl if possible.
2264 Op = IC.InsertNewInstBefore(BinaryOperator::createMul(Op, Scale,
2265 GEP->getName()+".idx"), I);
2267 // Emit an add instruction.
2268 Result = IC.InsertNewInstBefore(BinaryOperator::createAdd(Op, Result,
2269 GEP->getName()+".offs"), I);
2275 /// FoldGEPSetCC - Fold comparisons between a GEP instruction and something
2276 /// else. At this point we know that the GEP is on the LHS of the comparison.
2277 Instruction *InstCombiner::FoldGEPSetCC(User *GEPLHS, Value *RHS,
2278 Instruction::BinaryOps Cond,
2280 assert(dyn_castGetElementPtr(GEPLHS) && "LHS is not a getelementptr!");
2282 if (CastInst *CI = dyn_cast<CastInst>(RHS))
2283 if (isa<PointerType>(CI->getOperand(0)->getType()))
2284 RHS = CI->getOperand(0);
2286 Value *PtrBase = GEPLHS->getOperand(0);
2287 if (PtrBase == RHS) {
2288 // As an optimization, we don't actually have to compute the actual value of
2289 // OFFSET if this is a seteq or setne comparison, just return whether each
2290 // index is zero or not.
2291 if (Cond == Instruction::SetEQ || Cond == Instruction::SetNE) {
2292 Instruction *InVal = 0;
2293 gep_type_iterator GTI = gep_type_begin(GEPLHS);
2294 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i, ++GTI) {
2296 if (Constant *C = dyn_cast<Constant>(GEPLHS->getOperand(i))) {
2297 if (isa<UndefValue>(C)) // undef index -> undef.
2298 return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
2299 if (C->isNullValue())
2301 else if (TD->getTypeSize(GTI.getIndexedType()) == 0) {
2302 EmitIt = false; // This is indexing into a zero sized array?
2303 } else if (isa<ConstantInt>(C))
2304 return ReplaceInstUsesWith(I, // No comparison is needed here.
2305 ConstantBool::get(Cond == Instruction::SetNE));
2310 new SetCondInst(Cond, GEPLHS->getOperand(i),
2311 Constant::getNullValue(GEPLHS->getOperand(i)->getType()));
2315 InVal = InsertNewInstBefore(InVal, I);
2316 InsertNewInstBefore(Comp, I);
2317 if (Cond == Instruction::SetNE) // True if any are unequal
2318 InVal = BinaryOperator::createOr(InVal, Comp);
2319 else // True if all are equal
2320 InVal = BinaryOperator::createAnd(InVal, Comp);
2328 ReplaceInstUsesWith(I, // No comparison is needed here, all indexes = 0
2329 ConstantBool::get(Cond == Instruction::SetEQ));
2332 // Only lower this if the setcc is the only user of the GEP or if we expect
2333 // the result to fold to a constant!
2334 if (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) {
2335 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
2336 Value *Offset = EmitGEPOffset(GEPLHS, I, *this);
2337 return new SetCondInst(Cond, Offset,
2338 Constant::getNullValue(Offset->getType()));
2340 } else if (User *GEPRHS = dyn_castGetElementPtr(RHS)) {
2341 // If the base pointers are different, but the indices are the same, just
2342 // compare the base pointer.
2343 if (PtrBase != GEPRHS->getOperand(0)) {
2344 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
2345 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
2346 GEPRHS->getOperand(0)->getType();
2348 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
2349 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
2350 IndicesTheSame = false;
2354 // If all indices are the same, just compare the base pointers.
2356 return new SetCondInst(Cond, GEPLHS->getOperand(0),
2357 GEPRHS->getOperand(0));
2359 // Otherwise, the base pointers are different and the indices are
2360 // different, bail out.
2364 // If one of the GEPs has all zero indices, recurse.
2365 bool AllZeros = true;
2366 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
2367 if (!isa<Constant>(GEPLHS->getOperand(i)) ||
2368 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
2373 return FoldGEPSetCC(GEPRHS, GEPLHS->getOperand(0),
2374 SetCondInst::getSwappedCondition(Cond), I);
2376 // If the other GEP has all zero indices, recurse.
2378 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
2379 if (!isa<Constant>(GEPRHS->getOperand(i)) ||
2380 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
2385 return FoldGEPSetCC(GEPLHS, GEPRHS->getOperand(0), Cond, I);
2387 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
2388 // If the GEPs only differ by one index, compare it.
2389 unsigned NumDifferences = 0; // Keep track of # differences.
2390 unsigned DiffOperand = 0; // The operand that differs.
2391 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
2392 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
2393 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
2394 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
2395 // Irreconcilable differences.
2399 if (NumDifferences++) break;
2404 if (NumDifferences == 0) // SAME GEP?
2405 return ReplaceInstUsesWith(I, // No comparison is needed here.
2406 ConstantBool::get(Cond == Instruction::SetEQ));
2407 else if (NumDifferences == 1) {
2408 Value *LHSV = GEPLHS->getOperand(DiffOperand);
2409 Value *RHSV = GEPRHS->getOperand(DiffOperand);
2411 // Convert the operands to signed values to make sure to perform a
2412 // signed comparison.
2413 const Type *NewTy = LHSV->getType()->getSignedVersion();
2414 if (LHSV->getType() != NewTy)
2415 LHSV = InsertNewInstBefore(new CastInst(LHSV, NewTy,
2416 LHSV->getName()), I);
2417 if (RHSV->getType() != NewTy)
2418 RHSV = InsertNewInstBefore(new CastInst(RHSV, NewTy,
2419 RHSV->getName()), I);
2420 return new SetCondInst(Cond, LHSV, RHSV);
2424 // Only lower this if the setcc is the only user of the GEP or if we expect
2425 // the result to fold to a constant!
2426 if ((isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
2427 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
2428 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
2429 Value *L = EmitGEPOffset(GEPLHS, I, *this);
2430 Value *R = EmitGEPOffset(GEPRHS, I, *this);
2431 return new SetCondInst(Cond, L, R);
2438 Instruction *InstCombiner::visitSetCondInst(SetCondInst &I) {
2439 bool Changed = SimplifyCommutative(I);
2440 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2441 const Type *Ty = Op0->getType();
2445 return ReplaceInstUsesWith(I, ConstantBool::get(isTrueWhenEqual(I)));
2447 if (isa<UndefValue>(Op1)) // X setcc undef -> undef
2448 return ReplaceInstUsesWith(I, UndefValue::get(Type::BoolTy));
2450 // setcc <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
2451 // addresses never equal each other! We already know that Op0 != Op1.
2452 if ((isa<GlobalValue>(Op0) || isa<AllocaInst>(Op0) ||
2453 isa<ConstantPointerNull>(Op0)) &&
2454 (isa<GlobalValue>(Op1) || isa<AllocaInst>(Op1) ||
2455 isa<ConstantPointerNull>(Op1)))
2456 return ReplaceInstUsesWith(I, ConstantBool::get(!isTrueWhenEqual(I)));
2458 // setcc's with boolean values can always be turned into bitwise operations
2459 if (Ty == Type::BoolTy) {
2460 switch (I.getOpcode()) {
2461 default: assert(0 && "Invalid setcc instruction!");
2462 case Instruction::SetEQ: { // seteq bool %A, %B -> ~(A^B)
2463 Instruction *Xor = BinaryOperator::createXor(Op0, Op1, I.getName()+"tmp");
2464 InsertNewInstBefore(Xor, I);
2465 return BinaryOperator::createNot(Xor);
2467 case Instruction::SetNE:
2468 return BinaryOperator::createXor(Op0, Op1);
2470 case Instruction::SetGT:
2471 std::swap(Op0, Op1); // Change setgt -> setlt
2473 case Instruction::SetLT: { // setlt bool A, B -> ~X & Y
2474 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
2475 InsertNewInstBefore(Not, I);
2476 return BinaryOperator::createAnd(Not, Op1);
2478 case Instruction::SetGE:
2479 std::swap(Op0, Op1); // Change setge -> setle
2481 case Instruction::SetLE: { // setle bool %A, %B -> ~A | B
2482 Instruction *Not = BinaryOperator::createNot(Op0, I.getName()+"tmp");
2483 InsertNewInstBefore(Not, I);
2484 return BinaryOperator::createOr(Not, Op1);
2489 // See if we are doing a comparison between a constant and an instruction that
2490 // can be folded into the comparison.
2491 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2492 // Check to see if we are comparing against the minimum or maximum value...
2493 if (CI->isMinValue()) {
2494 if (I.getOpcode() == Instruction::SetLT) // A < MIN -> FALSE
2495 return ReplaceInstUsesWith(I, ConstantBool::False);
2496 if (I.getOpcode() == Instruction::SetGE) // A >= MIN -> TRUE
2497 return ReplaceInstUsesWith(I, ConstantBool::True);
2498 if (I.getOpcode() == Instruction::SetLE) // A <= MIN -> A == MIN
2499 return BinaryOperator::createSetEQ(Op0, Op1);
2500 if (I.getOpcode() == Instruction::SetGT) // A > MIN -> A != MIN
2501 return BinaryOperator::createSetNE(Op0, Op1);
2503 } else if (CI->isMaxValue()) {
2504 if (I.getOpcode() == Instruction::SetGT) // A > MAX -> FALSE
2505 return ReplaceInstUsesWith(I, ConstantBool::False);
2506 if (I.getOpcode() == Instruction::SetLE) // A <= MAX -> TRUE
2507 return ReplaceInstUsesWith(I, ConstantBool::True);
2508 if (I.getOpcode() == Instruction::SetGE) // A >= MAX -> A == MAX
2509 return BinaryOperator::createSetEQ(Op0, Op1);
2510 if (I.getOpcode() == Instruction::SetLT) // A < MAX -> A != MAX
2511 return BinaryOperator::createSetNE(Op0, Op1);
2513 // Comparing against a value really close to min or max?
2514 } else if (isMinValuePlusOne(CI)) {
2515 if (I.getOpcode() == Instruction::SetLT) // A < MIN+1 -> A == MIN
2516 return BinaryOperator::createSetEQ(Op0, SubOne(CI));
2517 if (I.getOpcode() == Instruction::SetGE) // A >= MIN-1 -> A != MIN
2518 return BinaryOperator::createSetNE(Op0, SubOne(CI));
2520 } else if (isMaxValueMinusOne(CI)) {
2521 if (I.getOpcode() == Instruction::SetGT) // A > MAX-1 -> A == MAX
2522 return BinaryOperator::createSetEQ(Op0, AddOne(CI));
2523 if (I.getOpcode() == Instruction::SetLE) // A <= MAX-1 -> A != MAX
2524 return BinaryOperator::createSetNE(Op0, AddOne(CI));
2527 // If we still have a setle or setge instruction, turn it into the
2528 // appropriate setlt or setgt instruction. Since the border cases have
2529 // already been handled above, this requires little checking.
2531 if (I.getOpcode() == Instruction::SetLE)
2532 return BinaryOperator::createSetLT(Op0, AddOne(CI));
2533 if (I.getOpcode() == Instruction::SetGE)
2534 return BinaryOperator::createSetGT(Op0, SubOne(CI));
2536 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2537 switch (LHSI->getOpcode()) {
2538 case Instruction::And:
2539 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
2540 LHSI->getOperand(0)->hasOneUse()) {
2541 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
2542 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
2543 // happens a LOT in code produced by the C front-end, for bitfield
2545 ShiftInst *Shift = dyn_cast<ShiftInst>(LHSI->getOperand(0));
2546 ConstantUInt *ShAmt;
2547 ShAmt = Shift ? dyn_cast<ConstantUInt>(Shift->getOperand(1)) : 0;
2548 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
2549 const Type *Ty = LHSI->getType();
2551 // We can fold this as long as we can't shift unknown bits
2552 // into the mask. This can only happen with signed shift
2553 // rights, as they sign-extend.
2555 bool CanFold = Shift->getOpcode() != Instruction::Shr ||
2556 Shift->getType()->isUnsigned();
2558 // To test for the bad case of the signed shr, see if any
2559 // of the bits shifted in could be tested after the mask.
2560 int ShAmtVal = Ty->getPrimitiveSizeInBits()-ShAmt->getValue();
2561 if (ShAmtVal < 0) ShAmtVal = 0; // Out of range shift.
2563 Constant *OShAmt = ConstantUInt::get(Type::UByteTy, ShAmtVal);
2565 ConstantExpr::getShl(ConstantInt::getAllOnesValue(Ty), OShAmt);
2566 if (ConstantExpr::getAnd(ShVal, AndCST)->isNullValue())
2572 if (Shift->getOpcode() == Instruction::Shl)
2573 NewCst = ConstantExpr::getUShr(CI, ShAmt);
2575 NewCst = ConstantExpr::getShl(CI, ShAmt);
2577 // Check to see if we are shifting out any of the bits being
2579 if (ConstantExpr::get(Shift->getOpcode(), NewCst, ShAmt) != CI){
2580 // If we shifted bits out, the fold is not going to work out.
2581 // As a special case, check to see if this means that the
2582 // result is always true or false now.
2583 if (I.getOpcode() == Instruction::SetEQ)
2584 return ReplaceInstUsesWith(I, ConstantBool::False);
2585 if (I.getOpcode() == Instruction::SetNE)
2586 return ReplaceInstUsesWith(I, ConstantBool::True);
2588 I.setOperand(1, NewCst);
2589 Constant *NewAndCST;
2590 if (Shift->getOpcode() == Instruction::Shl)
2591 NewAndCST = ConstantExpr::getUShr(AndCST, ShAmt);
2593 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
2594 LHSI->setOperand(1, NewAndCST);
2595 LHSI->setOperand(0, Shift->getOperand(0));
2596 WorkList.push_back(Shift); // Shift is dead.
2597 AddUsesToWorkList(I);
2605 case Instruction::Shl: // (setcc (shl X, ShAmt), CI)
2606 if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
2607 switch (I.getOpcode()) {
2609 case Instruction::SetEQ:
2610 case Instruction::SetNE: {
2611 unsigned TypeBits = CI->getType()->getPrimitiveSizeInBits();
2613 // Check that the shift amount is in range. If not, don't perform
2614 // undefined shifts. When the shift is visited it will be
2616 if (ShAmt->getValue() >= TypeBits)
2619 // If we are comparing against bits always shifted out, the
2620 // comparison cannot succeed.
2622 ConstantExpr::getShl(ConstantExpr::getShr(CI, ShAmt), ShAmt);
2623 if (Comp != CI) {// Comparing against a bit that we know is zero.
2624 bool IsSetNE = I.getOpcode() == Instruction::SetNE;
2625 Constant *Cst = ConstantBool::get(IsSetNE);
2626 return ReplaceInstUsesWith(I, Cst);
2629 if (LHSI->hasOneUse()) {
2630 // Otherwise strength reduce the shift into an and.
2631 unsigned ShAmtVal = (unsigned)ShAmt->getValue();
2632 uint64_t Val = (1ULL << (TypeBits-ShAmtVal))-1;
2635 if (CI->getType()->isUnsigned()) {
2636 Mask = ConstantUInt::get(CI->getType(), Val);
2637 } else if (ShAmtVal != 0) {
2638 Mask = ConstantSInt::get(CI->getType(), Val);
2640 Mask = ConstantInt::getAllOnesValue(CI->getType());
2644 BinaryOperator::createAnd(LHSI->getOperand(0),
2645 Mask, LHSI->getName()+".mask");
2646 Value *And = InsertNewInstBefore(AndI, I);
2647 return new SetCondInst(I.getOpcode(), And,
2648 ConstantExpr::getUShr(CI, ShAmt));
2655 case Instruction::Shr: // (setcc (shr X, ShAmt), CI)
2656 if (ConstantUInt *ShAmt = dyn_cast<ConstantUInt>(LHSI->getOperand(1))) {
2657 switch (I.getOpcode()) {
2659 case Instruction::SetEQ:
2660 case Instruction::SetNE: {
2662 // Check that the shift amount is in range. If not, don't perform
2663 // undefined shifts. When the shift is visited it will be
2665 unsigned TypeBits = CI->getType()->getPrimitiveSizeInBits();
2666 if (ShAmt->getValue() >= TypeBits)
2669 // If we are comparing against bits always shifted out, the
2670 // comparison cannot succeed.
2672 ConstantExpr::getShr(ConstantExpr::getShl(CI, ShAmt), ShAmt);
2674 if (Comp != CI) {// Comparing against a bit that we know is zero.
2675 bool IsSetNE = I.getOpcode() == Instruction::SetNE;
2676 Constant *Cst = ConstantBool::get(IsSetNE);
2677 return ReplaceInstUsesWith(I, Cst);
2680 if (LHSI->hasOneUse() || CI->isNullValue()) {
2681 unsigned ShAmtVal = (unsigned)ShAmt->getValue();
2683 // Otherwise strength reduce the shift into an and.
2684 uint64_t Val = ~0ULL; // All ones.
2685 Val <<= ShAmtVal; // Shift over to the right spot.
2688 if (CI->getType()->isUnsigned()) {
2689 Val &= ~0ULL >> (64-TypeBits);
2690 Mask = ConstantUInt::get(CI->getType(), Val);
2692 Mask = ConstantSInt::get(CI->getType(), Val);
2696 BinaryOperator::createAnd(LHSI->getOperand(0),
2697 Mask, LHSI->getName()+".mask");
2698 Value *And = InsertNewInstBefore(AndI, I);
2699 return new SetCondInst(I.getOpcode(), And,
2700 ConstantExpr::getShl(CI, ShAmt));
2708 case Instruction::Div:
2709 // Fold: (div X, C1) op C2 -> range check
2710 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
2711 // Fold this div into the comparison, producing a range check.
2712 // Determine, based on the divide type, what the range is being
2713 // checked. If there is an overflow on the low or high side, remember
2714 // it, otherwise compute the range [low, hi) bounding the new value.
2715 bool LoOverflow = false, HiOverflow = 0;
2716 ConstantInt *LoBound = 0, *HiBound = 0;
2719 bool ProdOV = MulWithOverflow(Prod, CI, DivRHS);
2721 Instruction::BinaryOps Opcode = I.getOpcode();
2723 if (DivRHS->isNullValue()) { // Don't hack on divide by zeros.
2724 } else if (LHSI->getType()->isUnsigned()) { // udiv
2726 LoOverflow = ProdOV;
2727 HiOverflow = ProdOV || AddWithOverflow(HiBound, LoBound, DivRHS);
2728 } else if (isPositive(DivRHS)) { // Divisor is > 0.
2729 if (CI->isNullValue()) { // (X / pos) op 0
2731 LoBound = cast<ConstantInt>(ConstantExpr::getNeg(SubOne(DivRHS)));
2733 } else if (isPositive(CI)) { // (X / pos) op pos
2735 LoOverflow = ProdOV;
2736 HiOverflow = ProdOV || AddWithOverflow(HiBound, Prod, DivRHS);
2737 } else { // (X / pos) op neg
2738 Constant *DivRHSH = ConstantExpr::getNeg(SubOne(DivRHS));
2739 LoOverflow = AddWithOverflow(LoBound, Prod,
2740 cast<ConstantInt>(DivRHSH));
2742 HiOverflow = ProdOV;
2744 } else { // Divisor is < 0.
2745 if (CI->isNullValue()) { // (X / neg) op 0
2746 LoBound = AddOne(DivRHS);
2747 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(DivRHS));
2748 if (HiBound == DivRHS)
2749 LoBound = 0; // - INTMIN = INTMIN
2750 } else if (isPositive(CI)) { // (X / neg) op pos
2751 HiOverflow = LoOverflow = ProdOV;
2753 LoOverflow = AddWithOverflow(LoBound, Prod, AddOne(DivRHS));
2754 HiBound = AddOne(Prod);
2755 } else { // (X / neg) op neg
2757 LoOverflow = HiOverflow = ProdOV;
2758 HiBound = cast<ConstantInt>(ConstantExpr::getSub(Prod, DivRHS));
2761 // Dividing by a negate swaps the condition.
2762 Opcode = SetCondInst::getSwappedCondition(Opcode);
2766 Value *X = LHSI->getOperand(0);
2768 default: assert(0 && "Unhandled setcc opcode!");
2769 case Instruction::SetEQ:
2770 if (LoOverflow && HiOverflow)
2771 return ReplaceInstUsesWith(I, ConstantBool::False);
2772 else if (HiOverflow)
2773 return new SetCondInst(Instruction::SetGE, X, LoBound);
2774 else if (LoOverflow)
2775 return new SetCondInst(Instruction::SetLT, X, HiBound);
2777 return InsertRangeTest(X, LoBound, HiBound, true, I);
2778 case Instruction::SetNE:
2779 if (LoOverflow && HiOverflow)
2780 return ReplaceInstUsesWith(I, ConstantBool::True);
2781 else if (HiOverflow)
2782 return new SetCondInst(Instruction::SetLT, X, LoBound);
2783 else if (LoOverflow)
2784 return new SetCondInst(Instruction::SetGE, X, HiBound);
2786 return InsertRangeTest(X, LoBound, HiBound, false, I);
2787 case Instruction::SetLT:
2789 return ReplaceInstUsesWith(I, ConstantBool::False);
2790 return new SetCondInst(Instruction::SetLT, X, LoBound);
2791 case Instruction::SetGT:
2793 return ReplaceInstUsesWith(I, ConstantBool::False);
2794 return new SetCondInst(Instruction::SetGE, X, HiBound);
2801 // Simplify seteq and setne instructions...
2802 if (I.getOpcode() == Instruction::SetEQ ||
2803 I.getOpcode() == Instruction::SetNE) {
2804 bool isSetNE = I.getOpcode() == Instruction::SetNE;
2806 // If the first operand is (and|or|xor) with a constant, and the second
2807 // operand is a constant, simplify a bit.
2808 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0)) {
2809 switch (BO->getOpcode()) {
2810 case Instruction::Rem:
2811 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2812 if (CI->isNullValue() && isa<ConstantSInt>(BO->getOperand(1)) &&
2814 cast<ConstantSInt>(BO->getOperand(1))->getValue() > 1) {
2815 int64_t V = cast<ConstantSInt>(BO->getOperand(1))->getValue();
2816 if (isPowerOf2_64(V)) {
2817 unsigned L2 = Log2_64(V);
2818 const Type *UTy = BO->getType()->getUnsignedVersion();
2819 Value *NewX = InsertNewInstBefore(new CastInst(BO->getOperand(0),
2821 Constant *RHSCst = ConstantUInt::get(UTy, 1ULL << L2);
2822 Value *NewRem =InsertNewInstBefore(BinaryOperator::createRem(NewX,
2823 RHSCst, BO->getName()), I);
2824 return BinaryOperator::create(I.getOpcode(), NewRem,
2825 Constant::getNullValue(UTy));
2830 case Instruction::Add:
2831 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2832 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
2833 if (BO->hasOneUse())
2834 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
2835 ConstantExpr::getSub(CI, BOp1C));
2836 } else if (CI->isNullValue()) {
2837 // Replace ((add A, B) != 0) with (A != -B) if A or B is
2838 // efficiently invertible, or if the add has just this one use.
2839 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2841 if (Value *NegVal = dyn_castNegVal(BOp1))
2842 return new SetCondInst(I.getOpcode(), BOp0, NegVal);
2843 else if (Value *NegVal = dyn_castNegVal(BOp0))
2844 return new SetCondInst(I.getOpcode(), NegVal, BOp1);
2845 else if (BO->hasOneUse()) {
2846 Instruction *Neg = BinaryOperator::createNeg(BOp1, BO->getName());
2848 InsertNewInstBefore(Neg, I);
2849 return new SetCondInst(I.getOpcode(), BOp0, Neg);
2853 case Instruction::Xor:
2854 // For the xor case, we can xor two constants together, eliminating
2855 // the explicit xor.
2856 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1)))
2857 return BinaryOperator::create(I.getOpcode(), BO->getOperand(0),
2858 ConstantExpr::getXor(CI, BOC));
2861 case Instruction::Sub:
2862 // Replace (([sub|xor] A, B) != 0) with (A != B)
2863 if (CI->isNullValue())
2864 return new SetCondInst(I.getOpcode(), BO->getOperand(0),
2868 case Instruction::Or:
2869 // If bits are being or'd in that are not present in the constant we
2870 // are comparing against, then the comparison could never succeed!
2871 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
2872 Constant *NotCI = ConstantExpr::getNot(CI);
2873 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
2874 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
2878 case Instruction::And:
2879 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
2880 // If bits are being compared against that are and'd out, then the
2881 // comparison can never succeed!
2882 if (!ConstantExpr::getAnd(CI,
2883 ConstantExpr::getNot(BOC))->isNullValue())
2884 return ReplaceInstUsesWith(I, ConstantBool::get(isSetNE));
2886 // If we have ((X & C) == C), turn it into ((X & C) != 0).
2887 if (CI == BOC && isOneBitSet(CI))
2888 return new SetCondInst(isSetNE ? Instruction::SetEQ :
2889 Instruction::SetNE, Op0,
2890 Constant::getNullValue(CI->getType()));
2892 // Replace (and X, (1 << size(X)-1) != 0) with x < 0, converting X
2893 // to be a signed value as appropriate.
2894 if (isSignBit(BOC)) {
2895 Value *X = BO->getOperand(0);
2896 // If 'X' is not signed, insert a cast now...
2897 if (!BOC->getType()->isSigned()) {
2898 const Type *DestTy = BOC->getType()->getSignedVersion();
2899 X = InsertCastBefore(X, DestTy, I);
2901 return new SetCondInst(isSetNE ? Instruction::SetLT :
2902 Instruction::SetGE, X,
2903 Constant::getNullValue(X->getType()));
2906 // ((X & ~7) == 0) --> X < 8
2907 if (CI->isNullValue() && isHighOnes(BOC)) {
2908 Value *X = BO->getOperand(0);
2909 Constant *NegX = ConstantExpr::getNeg(BOC);
2911 // If 'X' is signed, insert a cast now.
2912 if (NegX->getType()->isSigned()) {
2913 const Type *DestTy = NegX->getType()->getUnsignedVersion();
2914 X = InsertCastBefore(X, DestTy, I);
2915 NegX = ConstantExpr::getCast(NegX, DestTy);
2918 return new SetCondInst(isSetNE ? Instruction::SetGE :
2919 Instruction::SetLT, X, NegX);
2926 } else { // Not a SetEQ/SetNE
2927 // If the LHS is a cast from an integral value of the same size,
2928 if (CastInst *Cast = dyn_cast<CastInst>(Op0)) {
2929 Value *CastOp = Cast->getOperand(0);
2930 const Type *SrcTy = CastOp->getType();
2931 unsigned SrcTySize = SrcTy->getPrimitiveSizeInBits();
2932 if (SrcTy != Cast->getType() && SrcTy->isInteger() &&
2933 SrcTySize == Cast->getType()->getPrimitiveSizeInBits()) {
2934 assert((SrcTy->isSigned() ^ Cast->getType()->isSigned()) &&
2935 "Source and destination signednesses should differ!");
2936 if (Cast->getType()->isSigned()) {
2937 // If this is a signed comparison, check for comparisons in the
2938 // vicinity of zero.
2939 if (I.getOpcode() == Instruction::SetLT && CI->isNullValue())
2941 return BinaryOperator::createSetGT(CastOp,
2942 ConstantUInt::get(SrcTy, (1ULL << (SrcTySize-1))-1));
2943 else if (I.getOpcode() == Instruction::SetGT &&
2944 cast<ConstantSInt>(CI)->getValue() == -1)
2945 // X > -1 => x < 128
2946 return BinaryOperator::createSetLT(CastOp,
2947 ConstantUInt::get(SrcTy, 1ULL << (SrcTySize-1)));
2949 ConstantUInt *CUI = cast<ConstantUInt>(CI);
2950 if (I.getOpcode() == Instruction::SetLT &&
2951 CUI->getValue() == 1ULL << (SrcTySize-1))
2952 // X < 128 => X > -1
2953 return BinaryOperator::createSetGT(CastOp,
2954 ConstantSInt::get(SrcTy, -1));
2955 else if (I.getOpcode() == Instruction::SetGT &&
2956 CUI->getValue() == (1ULL << (SrcTySize-1))-1)
2958 return BinaryOperator::createSetLT(CastOp,
2959 Constant::getNullValue(SrcTy));
2966 // Handle setcc with constant RHS's that can be integer, FP or pointer.
2967 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
2968 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2969 switch (LHSI->getOpcode()) {
2970 case Instruction::GetElementPtr:
2971 if (RHSC->isNullValue()) {
2972 // Transform setcc GEP P, int 0, int 0, int 0, null -> setcc P, null
2973 bool isAllZeros = true;
2974 for (unsigned i = 1, e = LHSI->getNumOperands(); i != e; ++i)
2975 if (!isa<Constant>(LHSI->getOperand(i)) ||
2976 !cast<Constant>(LHSI->getOperand(i))->isNullValue()) {
2981 return new SetCondInst(I.getOpcode(), LHSI->getOperand(0),
2982 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2986 case Instruction::PHI:
2987 if (Instruction *NV = FoldOpIntoPhi(I))
2990 case Instruction::Select:
2991 // If either operand of the select is a constant, we can fold the
2992 // comparison into the select arms, which will cause one to be
2993 // constant folded and the select turned into a bitwise or.
2994 Value *Op1 = 0, *Op2 = 0;
2995 if (LHSI->hasOneUse()) {
2996 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2997 // Fold the known value into the constant operand.
2998 Op1 = ConstantExpr::get(I.getOpcode(), C, RHSC);
2999 // Insert a new SetCC of the other select operand.
3000 Op2 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
3001 LHSI->getOperand(2), RHSC,
3003 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
3004 // Fold the known value into the constant operand.
3005 Op2 = ConstantExpr::get(I.getOpcode(), C, RHSC);
3006 // Insert a new SetCC of the other select operand.
3007 Op1 = InsertNewInstBefore(new SetCondInst(I.getOpcode(),
3008 LHSI->getOperand(1), RHSC,
3014 return new SelectInst(LHSI->getOperand(0), Op1, Op2);
3019 // If we can optimize a 'setcc GEP, P' or 'setcc P, GEP', do so now.
3020 if (User *GEP = dyn_castGetElementPtr(Op0))
3021 if (Instruction *NI = FoldGEPSetCC(GEP, Op1, I.getOpcode(), I))
3023 if (User *GEP = dyn_castGetElementPtr(Op1))
3024 if (Instruction *NI = FoldGEPSetCC(GEP, Op0,
3025 SetCondInst::getSwappedCondition(I.getOpcode()), I))
3028 // Test to see if the operands of the setcc are casted versions of other
3029 // values. If the cast can be stripped off both arguments, we do so now.
3030 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
3031 Value *CastOp0 = CI->getOperand(0);
3032 if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
3033 (isa<Constant>(Op1) || isa<CastInst>(Op1)) &&
3034 (I.getOpcode() == Instruction::SetEQ ||
3035 I.getOpcode() == Instruction::SetNE)) {
3036 // We keep moving the cast from the left operand over to the right
3037 // operand, where it can often be eliminated completely.
3040 // If operand #1 is a cast instruction, see if we can eliminate it as
3042 if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
3043 if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
3045 Op1 = CI2->getOperand(0);
3047 // If Op1 is a constant, we can fold the cast into the constant.
3048 if (Op1->getType() != Op0->getType())
3049 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
3050 Op1 = ConstantExpr::getCast(Op1C, Op0->getType());
3052 // Otherwise, cast the RHS right before the setcc
3053 Op1 = new CastInst(Op1, Op0->getType(), Op1->getName());
3054 InsertNewInstBefore(cast<Instruction>(Op1), I);
3056 return BinaryOperator::create(I.getOpcode(), Op0, Op1);
3059 // Handle the special case of: setcc (cast bool to X), <cst>
3060 // This comes up when you have code like
3063 // For generality, we handle any zero-extension of any operand comparison
3064 // with a constant or another cast from the same type.
3065 if (isa<ConstantInt>(Op1) || isa<CastInst>(Op1))
3066 if (Instruction *R = visitSetCondInstWithCastAndCast(I))
3069 return Changed ? &I : 0;
3072 // visitSetCondInstWithCastAndCast - Handle setcond (cast x to y), (cast/cst).
3073 // We only handle extending casts so far.
3075 Instruction *InstCombiner::visitSetCondInstWithCastAndCast(SetCondInst &SCI) {
3076 Value *LHSCIOp = cast<CastInst>(SCI.getOperand(0))->getOperand(0);
3077 const Type *SrcTy = LHSCIOp->getType();
3078 const Type *DestTy = SCI.getOperand(0)->getType();
3081 if (!DestTy->isIntegral() || !SrcTy->isIntegral())
3084 unsigned SrcBits = SrcTy->getPrimitiveSizeInBits();
3085 unsigned DestBits = DestTy->getPrimitiveSizeInBits();
3086 if (SrcBits >= DestBits) return 0; // Only handle extending cast.
3088 // Is this a sign or zero extension?
3089 bool isSignSrc = SrcTy->isSigned();
3090 bool isSignDest = DestTy->isSigned();
3092 if (CastInst *CI = dyn_cast<CastInst>(SCI.getOperand(1))) {
3093 // Not an extension from the same type?
3094 RHSCIOp = CI->getOperand(0);
3095 if (RHSCIOp->getType() != LHSCIOp->getType()) return 0;
3096 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(SCI.getOperand(1))) {
3097 // Compute the constant that would happen if we truncated to SrcTy then
3098 // reextended to DestTy.
3099 Constant *Res = ConstantExpr::getCast(CI, SrcTy);
3101 if (ConstantExpr::getCast(Res, DestTy) == CI) {
3104 // If the value cannot be represented in the shorter type, we cannot emit
3105 // a simple comparison.
3106 if (SCI.getOpcode() == Instruction::SetEQ)
3107 return ReplaceInstUsesWith(SCI, ConstantBool::False);
3108 if (SCI.getOpcode() == Instruction::SetNE)
3109 return ReplaceInstUsesWith(SCI, ConstantBool::True);
3111 // Evaluate the comparison for LT.
3113 if (DestTy->isSigned()) {
3114 // We're performing a signed comparison.
3116 // Signed extend and signed comparison.
3117 if (cast<ConstantSInt>(CI)->getValue() < 0) // X < (small) --> false
3118 Result = ConstantBool::False;
3120 Result = ConstantBool::True; // X < (large) --> true
3122 // Unsigned extend and signed comparison.
3123 if (cast<ConstantSInt>(CI)->getValue() < 0)
3124 Result = ConstantBool::False;
3126 Result = ConstantBool::True;
3129 // We're performing an unsigned comparison.
3131 // Unsigned extend & compare -> always true.
3132 Result = ConstantBool::True;
3134 // We're performing an unsigned comp with a sign extended value.
3135 // This is true if the input is >= 0. [aka >s -1]
3136 Constant *NegOne = ConstantIntegral::getAllOnesValue(SrcTy);
3137 Result = InsertNewInstBefore(BinaryOperator::createSetGT(LHSCIOp,
3138 NegOne, SCI.getName()), SCI);
3142 // Finally, return the value computed.
3143 if (SCI.getOpcode() == Instruction::SetLT) {
3144 return ReplaceInstUsesWith(SCI, Result);
3146 assert(SCI.getOpcode()==Instruction::SetGT &&"SetCC should be folded!");
3147 if (Constant *CI = dyn_cast<Constant>(Result))
3148 return ReplaceInstUsesWith(SCI, ConstantExpr::getNot(CI));
3150 return BinaryOperator::createNot(Result);
3157 // Okay, just insert a compare of the reduced operands now!
3158 return BinaryOperator::create(SCI.getOpcode(), LHSCIOp, RHSCIOp);
3161 Instruction *InstCombiner::visitShiftInst(ShiftInst &I) {
3162 assert(I.getOperand(1)->getType() == Type::UByteTy);
3163 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3164 bool isLeftShift = I.getOpcode() == Instruction::Shl;
3166 // shl X, 0 == X and shr X, 0 == X
3167 // shl 0, X == 0 and shr 0, X == 0
3168 if (Op1 == Constant::getNullValue(Type::UByteTy) ||
3169 Op0 == Constant::getNullValue(Op0->getType()))
3170 return ReplaceInstUsesWith(I, Op0);
3172 if (isa<UndefValue>(Op0)) { // undef >>s X -> undef
3173 if (!isLeftShift && I.getType()->isSigned())
3174 return ReplaceInstUsesWith(I, Op0);
3175 else // undef << X -> 0 AND undef >>u X -> 0
3176 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
3178 if (isa<UndefValue>(Op1)) {
3179 if (isLeftShift || I.getType()->isUnsigned())// X << undef, X >>u undef -> 0
3180 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
3182 return ReplaceInstUsesWith(I, Op0); // X >>s undef -> X
3185 // shr int -1, X = -1 (for any arithmetic shift rights of ~0)
3187 if (ConstantSInt *CSI = dyn_cast<ConstantSInt>(Op0))
3188 if (CSI->isAllOnesValue())
3189 return ReplaceInstUsesWith(I, CSI);
3191 // Try to fold constant and into select arguments.
3192 if (isa<Constant>(Op0))
3193 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
3194 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
3197 // See if we can turn a signed shr into an unsigned shr.
3198 if (!isLeftShift && I.getType()->isSigned()) {
3199 if (MaskedValueIsZero(Op0, ConstantInt::getMinValue(I.getType()))) {
3200 Value *V = InsertCastBefore(Op0, I.getType()->getUnsignedVersion(), I);
3201 V = InsertNewInstBefore(new ShiftInst(Instruction::Shr, V, Op1,
3203 return new CastInst(V, I.getType());
3207 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op1)) {
3208 // shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
3209 // of a signed value.
3211 unsigned TypeBits = Op0->getType()->getPrimitiveSizeInBits();
3212 if (CUI->getValue() >= TypeBits) {
3213 if (!Op0->getType()->isSigned() || isLeftShift)
3214 return ReplaceInstUsesWith(I, Constant::getNullValue(Op0->getType()));
3216 I.setOperand(1, ConstantUInt::get(Type::UByteTy, TypeBits-1));
3221 // ((X*C1) << C2) == (X * (C1 << C2))
3222 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0))
3223 if (BO->getOpcode() == Instruction::Mul && isLeftShift)
3224 if (Constant *BOOp = dyn_cast<Constant>(BO->getOperand(1)))
3225 return BinaryOperator::createMul(BO->getOperand(0),
3226 ConstantExpr::getShl(BOOp, CUI));
3228 // Try to fold constant and into select arguments.
3229 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
3230 if (Instruction *R = FoldOpIntoSelect(I, SI, this))
3232 if (isa<PHINode>(Op0))
3233 if (Instruction *NV = FoldOpIntoPhi(I))
3236 if (Op0->hasOneUse()) {
3237 // If this is a SHL of a sign-extending cast, see if we can turn the input
3238 // into a zero extending cast (a simple strength reduction).
3239 if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
3240 const Type *SrcTy = CI->getOperand(0)->getType();
3241 if (isLeftShift && SrcTy->isInteger() && SrcTy->isSigned() &&
3242 SrcTy->getPrimitiveSizeInBits() <
3243 CI->getType()->getPrimitiveSizeInBits()) {
3244 // We can change it to a zero extension if we are shifting out all of
3245 // the sign extended bits. To check this, form a mask of all of the
3246 // sign extend bits, then shift them left and see if we have anything
3248 Constant *Mask = ConstantIntegral::getAllOnesValue(SrcTy); // 1111
3249 Mask = ConstantExpr::getZeroExtend(Mask, CI->getType()); // 00001111
3250 Mask = ConstantExpr::getNot(Mask); // 1's in the sign bits: 11110000
3251 if (ConstantExpr::getShl(Mask, CUI)->isNullValue()) {
3252 // If the shift is nuking all of the sign bits, change this to a
3253 // zero extension cast. To do this, cast the cast input to
3254 // unsigned, then to the requested size.
3255 Value *CastOp = CI->getOperand(0);
3257 new CastInst(CastOp, CastOp->getType()->getUnsignedVersion(),
3258 CI->getName()+".uns");
3259 NC = InsertNewInstBefore(NC, I);
3260 // Finally, insert a replacement for CI.
3261 NC = new CastInst(NC, CI->getType(), CI->getName());
3263 NC = InsertNewInstBefore(NC, I);
3264 WorkList.push_back(CI); // Delete CI later.
3265 I.setOperand(0, NC);
3266 return &I; // The SHL operand was modified.
3271 // If the operand is an bitwise operator with a constant RHS, and the
3272 // shift is the only use, we can pull it out of the shift.
3273 if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
3274 if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
3275 bool isValid = true; // Valid only for And, Or, Xor
3276 bool highBitSet = false; // Transform if high bit of constant set?
3278 switch (Op0BO->getOpcode()) {
3279 default: isValid = false; break; // Do not perform transform!
3280 case Instruction::Add:
3281 isValid = isLeftShift;
3283 case Instruction::Or:
3284 case Instruction::Xor:
3287 case Instruction::And:
3292 // If this is a signed shift right, and the high bit is modified
3293 // by the logical operation, do not perform the transformation.
3294 // The highBitSet boolean indicates the value of the high bit of
3295 // the constant which would cause it to be modified for this
3298 if (isValid && !isLeftShift && !I.getType()->isUnsigned()) {
3299 uint64_t Val = Op0C->getRawValue();
3300 isValid = ((Val & (1 << (TypeBits-1))) != 0) == highBitSet;
3304 Constant *NewRHS = ConstantExpr::get(I.getOpcode(), Op0C, CUI);
3306 Instruction *NewShift =
3307 new ShiftInst(I.getOpcode(), Op0BO->getOperand(0), CUI,
3310 InsertNewInstBefore(NewShift, I);
3312 return BinaryOperator::create(Op0BO->getOpcode(), NewShift,
3318 // If this is a shift of a shift, see if we can fold the two together...
3319 if (ShiftInst *Op0SI = dyn_cast<ShiftInst>(Op0))
3320 if (ConstantUInt *ShiftAmt1C =
3321 dyn_cast<ConstantUInt>(Op0SI->getOperand(1))) {
3322 unsigned ShiftAmt1 = (unsigned)ShiftAmt1C->getValue();
3323 unsigned ShiftAmt2 = (unsigned)CUI->getValue();
3325 // Check for (A << c1) << c2 and (A >> c1) >> c2
3326 if (I.getOpcode() == Op0SI->getOpcode()) {
3327 unsigned Amt = ShiftAmt1+ShiftAmt2; // Fold into one big shift...
3328 if (Op0->getType()->getPrimitiveSizeInBits() < Amt)
3329 Amt = Op0->getType()->getPrimitiveSizeInBits();
3330 return new ShiftInst(I.getOpcode(), Op0SI->getOperand(0),
3331 ConstantUInt::get(Type::UByteTy, Amt));
3334 // Check for (A << c1) >> c2 or visaversa. If we are dealing with
3335 // signed types, we can only support the (A >> c1) << c2 configuration,
3336 // because it can not turn an arbitrary bit of A into a sign bit.
3337 if (I.getType()->isUnsigned() || isLeftShift) {
3338 // Calculate bitmask for what gets shifted off the edge...
3339 Constant *C = ConstantIntegral::getAllOnesValue(I.getType());
3341 C = ConstantExpr::getShl(C, ShiftAmt1C);
3343 C = ConstantExpr::getShr(C, ShiftAmt1C);
3346 BinaryOperator::createAnd(Op0SI->getOperand(0), C,
3347 Op0SI->getOperand(0)->getName()+".mask");
3348 InsertNewInstBefore(Mask, I);
3350 // Figure out what flavor of shift we should use...
3351 if (ShiftAmt1 == ShiftAmt2)
3352 return ReplaceInstUsesWith(I, Mask); // (A << c) >> c === A & c2
3353 else if (ShiftAmt1 < ShiftAmt2) {
3354 return new ShiftInst(I.getOpcode(), Mask,
3355 ConstantUInt::get(Type::UByteTy, ShiftAmt2-ShiftAmt1));
3357 return new ShiftInst(Op0SI->getOpcode(), Mask,
3358 ConstantUInt::get(Type::UByteTy, ShiftAmt1-ShiftAmt2));
3374 /// getCastType - In the future, we will split the cast instruction into these
3375 /// various types. Until then, we have to do the analysis here.
3376 static CastType getCastType(const Type *Src, const Type *Dest) {
3377 assert(Src->isIntegral() && Dest->isIntegral() &&
3378 "Only works on integral types!");
3379 unsigned SrcSize = Src->getPrimitiveSizeInBits();
3380 unsigned DestSize = Dest->getPrimitiveSizeInBits();
3382 if (SrcSize == DestSize) return Noop;
3383 if (SrcSize > DestSize) return Truncate;
3384 if (Src->isSigned()) return Signext;
3389 // isEliminableCastOfCast - Return true if it is valid to eliminate the CI
3392 static inline bool isEliminableCastOfCast(const Type *SrcTy, const Type *MidTy,
3393 const Type *DstTy, TargetData *TD) {
3395 // It is legal to eliminate the instruction if casting A->B->A if the sizes
3396 // are identical and the bits don't get reinterpreted (for example
3397 // int->float->int would not be allowed).
3398 if (SrcTy == DstTy && SrcTy->isLosslesslyConvertibleTo(MidTy))
3401 // If we are casting between pointer and integer types, treat pointers as
3402 // integers of the appropriate size for the code below.
3403 if (isa<PointerType>(SrcTy)) SrcTy = TD->getIntPtrType();
3404 if (isa<PointerType>(MidTy)) MidTy = TD->getIntPtrType();
3405 if (isa<PointerType>(DstTy)) DstTy = TD->getIntPtrType();
3407 // Allow free casting and conversion of sizes as long as the sign doesn't
3409 if (SrcTy->isIntegral() && MidTy->isIntegral() && DstTy->isIntegral()) {
3410 CastType FirstCast = getCastType(SrcTy, MidTy);
3411 CastType SecondCast = getCastType(MidTy, DstTy);
3413 // Capture the effect of these two casts. If the result is a legal cast,
3414 // the CastType is stored here, otherwise a special code is used.
3415 static const unsigned CastResult[] = {
3416 // First cast is noop
3418 // First cast is a truncate
3419 1, 1, 4, 4, // trunc->extend is not safe to eliminate
3420 // First cast is a sign ext
3421 2, 5, 2, 4, // signext->zeroext never ok
3422 // First cast is a zero ext
3426 unsigned Result = CastResult[FirstCast*4+SecondCast];
3428 default: assert(0 && "Illegal table value!");
3433 // FIXME: in the future, when LLVM has explicit sign/zeroextends and
3434 // truncates, we could eliminate more casts.
3435 return (unsigned)getCastType(SrcTy, DstTy) == Result;
3437 return false; // Not possible to eliminate this here.
3439 // Sign or zero extend followed by truncate is always ok if the result
3440 // is a truncate or noop.
3441 CastType ResultCast = getCastType(SrcTy, DstTy);
3442 if (ResultCast == Noop || ResultCast == Truncate)
3444 // Otherwise we are still growing the value, we are only safe if the
3445 // result will match the sign/zeroextendness of the result.
3446 return ResultCast == FirstCast;
3452 static bool ValueRequiresCast(const Value *V, const Type *Ty, TargetData *TD) {
3453 if (V->getType() == Ty || isa<Constant>(V)) return false;
3454 if (const CastInst *CI = dyn_cast<CastInst>(V))
3455 if (isEliminableCastOfCast(CI->getOperand(0)->getType(), CI->getType(), Ty,
3461 /// InsertOperandCastBefore - This inserts a cast of V to DestTy before the
3462 /// InsertBefore instruction. This is specialized a bit to avoid inserting
3463 /// casts that are known to not do anything...
3465 Value *InstCombiner::InsertOperandCastBefore(Value *V, const Type *DestTy,
3466 Instruction *InsertBefore) {
3467 if (V->getType() == DestTy) return V;
3468 if (Constant *C = dyn_cast<Constant>(V))
3469 return ConstantExpr::getCast(C, DestTy);
3471 CastInst *CI = new CastInst(V, DestTy, V->getName());
3472 InsertNewInstBefore(CI, *InsertBefore);
3476 // CastInst simplification
3478 Instruction *InstCombiner::visitCastInst(CastInst &CI) {
3479 Value *Src = CI.getOperand(0);
3481 // If the user is casting a value to the same type, eliminate this cast
3483 if (CI.getType() == Src->getType())
3484 return ReplaceInstUsesWith(CI, Src);
3486 if (isa<UndefValue>(Src)) // cast undef -> undef
3487 return ReplaceInstUsesWith(CI, UndefValue::get(CI.getType()));
3489 // If casting the result of another cast instruction, try to eliminate this
3492 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast
3493 Value *A = CSrc->getOperand(0);
3494 if (isEliminableCastOfCast(A->getType(), CSrc->getType(),
3495 CI.getType(), TD)) {
3496 // This instruction now refers directly to the cast's src operand. This
3497 // has a good chance of making CSrc dead.
3498 CI.setOperand(0, CSrc->getOperand(0));
3502 // If this is an A->B->A cast, and we are dealing with integral types, try
3503 // to convert this into a logical 'and' instruction.
3505 if (A->getType()->isInteger() &&
3506 CI.getType()->isInteger() && CSrc->getType()->isInteger() &&
3507 CSrc->getType()->isUnsigned() && // B->A cast must zero extend
3508 CSrc->getType()->getPrimitiveSizeInBits() <
3509 CI.getType()->getPrimitiveSizeInBits()&&
3510 A->getType()->getPrimitiveSizeInBits() ==
3511 CI.getType()->getPrimitiveSizeInBits()) {
3512 assert(CSrc->getType() != Type::ULongTy &&
3513 "Cannot have type bigger than ulong!");
3514 uint64_t AndValue = ~0ULL>>(64-CSrc->getType()->getPrimitiveSizeInBits());
3515 Constant *AndOp = ConstantUInt::get(A->getType()->getUnsignedVersion(),
3517 AndOp = ConstantExpr::getCast(AndOp, A->getType());
3518 Instruction *And = BinaryOperator::createAnd(CSrc->getOperand(0), AndOp);
3519 if (And->getType() != CI.getType()) {
3520 And->setName(CSrc->getName()+".mask");
3521 InsertNewInstBefore(And, CI);
3522 And = new CastInst(And, CI.getType());
3528 // If this is a cast to bool, turn it into the appropriate setne instruction.
3529 if (CI.getType() == Type::BoolTy)
3530 return BinaryOperator::createSetNE(CI.getOperand(0),
3531 Constant::getNullValue(CI.getOperand(0)->getType()));
3533 // If casting the result of a getelementptr instruction with no offset, turn
3534 // this into a cast of the original pointer!
3536 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) {
3537 bool AllZeroOperands = true;
3538 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
3539 if (!isa<Constant>(GEP->getOperand(i)) ||
3540 !cast<Constant>(GEP->getOperand(i))->isNullValue()) {
3541 AllZeroOperands = false;
3544 if (AllZeroOperands) {
3545 CI.setOperand(0, GEP->getOperand(0));
3550 // If we are casting a malloc or alloca to a pointer to a type of the same
3551 // size, rewrite the allocation instruction to allocate the "right" type.
3553 if (AllocationInst *AI = dyn_cast<AllocationInst>(Src))
3554 if (AI->hasOneUse() && !AI->isArrayAllocation())
3555 if (const PointerType *PTy = dyn_cast<PointerType>(CI.getType())) {
3556 // Get the type really allocated and the type casted to...
3557 const Type *AllocElTy = AI->getAllocatedType();
3558 const Type *CastElTy = PTy->getElementType();
3559 if (AllocElTy->isSized() && CastElTy->isSized()) {
3560 uint64_t AllocElTySize = TD->getTypeSize(AllocElTy);
3561 uint64_t CastElTySize = TD->getTypeSize(CastElTy);
3563 // If the allocation is for an even multiple of the cast type size
3564 if (CastElTySize && (AllocElTySize % CastElTySize == 0)) {
3565 Value *Amt = ConstantUInt::get(Type::UIntTy,
3566 AllocElTySize/CastElTySize);
3567 std::string Name = AI->getName(); AI->setName("");
3568 AllocationInst *New;
3569 if (isa<MallocInst>(AI))
3570 New = new MallocInst(CastElTy, Amt, Name);
3572 New = new AllocaInst(CastElTy, Amt, Name);
3573 InsertNewInstBefore(New, *AI);
3574 return ReplaceInstUsesWith(CI, New);
3579 if (SelectInst *SI = dyn_cast<SelectInst>(Src))
3580 if (Instruction *NV = FoldOpIntoSelect(CI, SI, this))
3582 if (isa<PHINode>(Src))
3583 if (Instruction *NV = FoldOpIntoPhi(CI))
3586 // If the source value is an instruction with only this use, we can attempt to
3587 // propagate the cast into the instruction. Also, only handle integral types
3589 if (Instruction *SrcI = dyn_cast<Instruction>(Src))
3590 if (SrcI->hasOneUse() && Src->getType()->isIntegral() &&
3591 CI.getType()->isInteger()) { // Don't mess with casts to bool here
3592 const Type *DestTy = CI.getType();
3593 unsigned SrcBitSize = Src->getType()->getPrimitiveSizeInBits();
3594 unsigned DestBitSize = DestTy->getPrimitiveSizeInBits();
3596 Value *Op0 = SrcI->getNumOperands() > 0 ? SrcI->getOperand(0) : 0;
3597 Value *Op1 = SrcI->getNumOperands() > 1 ? SrcI->getOperand(1) : 0;
3599 switch (SrcI->getOpcode()) {
3600 case Instruction::Add:
3601 case Instruction::Mul:
3602 case Instruction::And:
3603 case Instruction::Or:
3604 case Instruction::Xor:
3605 // If we are discarding information, or just changing the sign, rewrite.
3606 if (DestBitSize <= SrcBitSize && DestBitSize != 1) {
3607 // Don't insert two casts if they cannot be eliminated. We allow two
3608 // casts to be inserted if the sizes are the same. This could only be
3609 // converting signedness, which is a noop.
3610 if (DestBitSize == SrcBitSize || !ValueRequiresCast(Op1, DestTy,TD) ||
3611 !ValueRequiresCast(Op0, DestTy, TD)) {
3612 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
3613 Value *Op1c = InsertOperandCastBefore(Op1, DestTy, SrcI);
3614 return BinaryOperator::create(cast<BinaryOperator>(SrcI)
3615 ->getOpcode(), Op0c, Op1c);
3619 // cast (xor bool X, true) to int --> xor (cast bool X to int), 1
3620 if (SrcBitSize == 1 && SrcI->getOpcode() == Instruction::Xor &&
3621 Op1 == ConstantBool::True &&
3622 (!Op0->hasOneUse() || !isa<SetCondInst>(Op0))) {
3623 Value *New = InsertOperandCastBefore(Op0, DestTy, &CI);
3624 return BinaryOperator::createXor(New,
3625 ConstantInt::get(CI.getType(), 1));
3628 case Instruction::Shl:
3629 // Allow changing the sign of the source operand. Do not allow changing
3630 // the size of the shift, UNLESS the shift amount is a constant. We
3631 // mush not change variable sized shifts to a smaller size, because it
3632 // is undefined to shift more bits out than exist in the value.
3633 if (DestBitSize == SrcBitSize ||
3634 (DestBitSize < SrcBitSize && isa<Constant>(Op1))) {
3635 Value *Op0c = InsertOperandCastBefore(Op0, DestTy, SrcI);
3636 return new ShiftInst(Instruction::Shl, Op0c, Op1);
3639 case Instruction::Shr:
3640 // If this is a signed shr, and if all bits shifted in are about to be
3641 // truncated off, turn it into an unsigned shr to allow greater
3643 if (DestBitSize < SrcBitSize && Src->getType()->isSigned() &&
3644 isa<ConstantInt>(Op1)) {
3645 unsigned ShiftAmt = cast<ConstantUInt>(Op1)->getValue();
3646 if (SrcBitSize > ShiftAmt && SrcBitSize-ShiftAmt >= DestBitSize) {
3647 // Convert to unsigned.
3648 Value *N1 = InsertOperandCastBefore(Op0,
3649 Op0->getType()->getUnsignedVersion(), &CI);
3650 // Insert the new shift, which is now unsigned.
3651 N1 = InsertNewInstBefore(new ShiftInst(Instruction::Shr, N1,
3652 Op1, Src->getName()), CI);
3653 return new CastInst(N1, CI.getType());
3658 case Instruction::SetNE:
3659 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
3660 if (Op1C->getRawValue() == 0) {
3661 // If the input only has the low bit set, simplify directly.
3663 ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
3664 // cast (X != 0) to int --> X if X&~1 == 0
3665 if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
3666 if (CI.getType() == Op0->getType())
3667 return ReplaceInstUsesWith(CI, Op0);
3669 return new CastInst(Op0, CI.getType());
3672 // If the input is an and with a single bit, shift then simplify.
3673 ConstantInt *AndRHS;
3674 if (match(Op0, m_And(m_Value(), m_ConstantInt(AndRHS))))
3675 if (AndRHS->getRawValue() &&
3676 (AndRHS->getRawValue() & (AndRHS->getRawValue()-1)) == 0) {
3677 unsigned ShiftAmt = Log2_64(AndRHS->getRawValue());
3678 // Perform an unsigned shr by shiftamt. Convert input to
3679 // unsigned if it is signed.
3681 if (In->getType()->isSigned())
3682 In = InsertNewInstBefore(new CastInst(In,
3683 In->getType()->getUnsignedVersion(), In->getName()),CI);
3684 // Insert the shift to put the result in the low bit.
3685 In = InsertNewInstBefore(new ShiftInst(Instruction::Shr, In,
3686 ConstantInt::get(Type::UByteTy, ShiftAmt),
3687 In->getName()+".lobit"), CI);
3688 if (CI.getType() == In->getType())
3689 return ReplaceInstUsesWith(CI, In);
3691 return new CastInst(In, CI.getType());
3696 case Instruction::SetEQ:
3697 // We if we are just checking for a seteq of a single bit and casting it
3698 // to an integer. If so, shift the bit to the appropriate place then
3699 // cast to integer to avoid the comparison.
3700 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
3701 // Is Op1C a power of two or zero?
3702 if ((Op1C->getRawValue() & Op1C->getRawValue()-1) == 0) {
3703 // cast (X == 1) to int -> X iff X has only the low bit set.
3704 if (Op1C->getRawValue() == 1) {
3706 ConstantExpr::getNot(ConstantInt::get(Op0->getType(), 1));
3707 if (MaskedValueIsZero(Op0, cast<ConstantIntegral>(Not1))) {
3708 if (CI.getType() == Op0->getType())
3709 return ReplaceInstUsesWith(CI, Op0);
3711 return new CastInst(Op0, CI.getType());
3722 /// GetSelectFoldableOperands - We want to turn code that looks like this:
3724 /// %D = select %cond, %C, %A
3726 /// %C = select %cond, %B, 0
3729 /// Assuming that the specified instruction is an operand to the select, return
3730 /// a bitmask indicating which operands of this instruction are foldable if they
3731 /// equal the other incoming value of the select.
3733 static unsigned GetSelectFoldableOperands(Instruction *I) {
3734 switch (I->getOpcode()) {
3735 case Instruction::Add:
3736 case Instruction::Mul:
3737 case Instruction::And:
3738 case Instruction::Or:
3739 case Instruction::Xor:
3740 return 3; // Can fold through either operand.
3741 case Instruction::Sub: // Can only fold on the amount subtracted.
3742 case Instruction::Shl: // Can only fold on the shift amount.
3743 case Instruction::Shr:
3746 return 0; // Cannot fold
3750 /// GetSelectFoldableConstant - For the same transformation as the previous
3751 /// function, return the identity constant that goes into the select.
3752 static Constant *GetSelectFoldableConstant(Instruction *I) {
3753 switch (I->getOpcode()) {
3754 default: assert(0 && "This cannot happen!"); abort();
3755 case Instruction::Add:
3756 case Instruction::Sub:
3757 case Instruction::Or:
3758 case Instruction::Xor:
3759 return Constant::getNullValue(I->getType());
3760 case Instruction::Shl:
3761 case Instruction::Shr:
3762 return Constant::getNullValue(Type::UByteTy);
3763 case Instruction::And:
3764 return ConstantInt::getAllOnesValue(I->getType());
3765 case Instruction::Mul:
3766 return ConstantInt::get(I->getType(), 1);
3770 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
3771 /// have the same opcode and only one use each. Try to simplify this.
3772 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
3774 if (TI->getNumOperands() == 1) {
3775 // If this is a non-volatile load or a cast from the same type,
3777 if (TI->getOpcode() == Instruction::Cast) {
3778 if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
3781 return 0; // unknown unary op.
3784 // Fold this by inserting a select from the input values.
3785 SelectInst *NewSI = new SelectInst(SI.getCondition(), TI->getOperand(0),
3786 FI->getOperand(0), SI.getName()+".v");
3787 InsertNewInstBefore(NewSI, SI);
3788 return new CastInst(NewSI, TI->getType());
3791 // Only handle binary operators here.
3792 if (!isa<ShiftInst>(TI) && !isa<BinaryOperator>(TI))
3795 // Figure out if the operations have any operands in common.
3796 Value *MatchOp, *OtherOpT, *OtherOpF;
3798 if (TI->getOperand(0) == FI->getOperand(0)) {
3799 MatchOp = TI->getOperand(0);
3800 OtherOpT = TI->getOperand(1);
3801 OtherOpF = FI->getOperand(1);
3802 MatchIsOpZero = true;
3803 } else if (TI->getOperand(1) == FI->getOperand(1)) {
3804 MatchOp = TI->getOperand(1);
3805 OtherOpT = TI->getOperand(0);
3806 OtherOpF = FI->getOperand(0);
3807 MatchIsOpZero = false;
3808 } else if (!TI->isCommutative()) {
3810 } else if (TI->getOperand(0) == FI->getOperand(1)) {
3811 MatchOp = TI->getOperand(0);
3812 OtherOpT = TI->getOperand(1);
3813 OtherOpF = FI->getOperand(0);
3814 MatchIsOpZero = true;
3815 } else if (TI->getOperand(1) == FI->getOperand(0)) {
3816 MatchOp = TI->getOperand(1);
3817 OtherOpT = TI->getOperand(0);
3818 OtherOpF = FI->getOperand(1);
3819 MatchIsOpZero = true;
3824 // If we reach here, they do have operations in common.
3825 SelectInst *NewSI = new SelectInst(SI.getCondition(), OtherOpT,
3826 OtherOpF, SI.getName()+".v");
3827 InsertNewInstBefore(NewSI, SI);
3829 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
3831 return BinaryOperator::create(BO->getOpcode(), MatchOp, NewSI);
3833 return BinaryOperator::create(BO->getOpcode(), NewSI, MatchOp);
3836 return new ShiftInst(cast<ShiftInst>(TI)->getOpcode(), MatchOp, NewSI);
3838 return new ShiftInst(cast<ShiftInst>(TI)->getOpcode(), NewSI, MatchOp);
3842 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
3843 Value *CondVal = SI.getCondition();
3844 Value *TrueVal = SI.getTrueValue();
3845 Value *FalseVal = SI.getFalseValue();
3847 // select true, X, Y -> X
3848 // select false, X, Y -> Y
3849 if (ConstantBool *C = dyn_cast<ConstantBool>(CondVal))
3850 if (C == ConstantBool::True)
3851 return ReplaceInstUsesWith(SI, TrueVal);
3853 assert(C == ConstantBool::False);
3854 return ReplaceInstUsesWith(SI, FalseVal);
3857 // select C, X, X -> X
3858 if (TrueVal == FalseVal)
3859 return ReplaceInstUsesWith(SI, TrueVal);
3861 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
3862 return ReplaceInstUsesWith(SI, FalseVal);
3863 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
3864 return ReplaceInstUsesWith(SI, TrueVal);
3865 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
3866 if (isa<Constant>(TrueVal))
3867 return ReplaceInstUsesWith(SI, TrueVal);
3869 return ReplaceInstUsesWith(SI, FalseVal);
3872 if (SI.getType() == Type::BoolTy)
3873 if (ConstantBool *C = dyn_cast<ConstantBool>(TrueVal)) {
3874 if (C == ConstantBool::True) {
3875 // Change: A = select B, true, C --> A = or B, C
3876 return BinaryOperator::createOr(CondVal, FalseVal);
3878 // Change: A = select B, false, C --> A = and !B, C
3880 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3881 "not."+CondVal->getName()), SI);
3882 return BinaryOperator::createAnd(NotCond, FalseVal);
3884 } else if (ConstantBool *C = dyn_cast<ConstantBool>(FalseVal)) {
3885 if (C == ConstantBool::False) {
3886 // Change: A = select B, C, false --> A = and B, C
3887 return BinaryOperator::createAnd(CondVal, TrueVal);
3889 // Change: A = select B, C, true --> A = or !B, C
3891 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3892 "not."+CondVal->getName()), SI);
3893 return BinaryOperator::createOr(NotCond, TrueVal);
3897 // Selecting between two integer constants?
3898 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
3899 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
3900 // select C, 1, 0 -> cast C to int
3901 if (FalseValC->isNullValue() && TrueValC->getRawValue() == 1) {
3902 return new CastInst(CondVal, SI.getType());
3903 } else if (TrueValC->isNullValue() && FalseValC->getRawValue() == 1) {
3904 // select C, 0, 1 -> cast !C to int
3906 InsertNewInstBefore(BinaryOperator::createNot(CondVal,
3907 "not."+CondVal->getName()), SI);
3908 return new CastInst(NotCond, SI.getType());
3911 // If one of the constants is zero (we know they can't both be) and we
3912 // have a setcc instruction with zero, and we have an 'and' with the
3913 // non-constant value, eliminate this whole mess. This corresponds to
3914 // cases like this: ((X & 27) ? 27 : 0)
3915 if (TrueValC->isNullValue() || FalseValC->isNullValue())
3916 if (Instruction *IC = dyn_cast<Instruction>(SI.getCondition()))
3917 if ((IC->getOpcode() == Instruction::SetEQ ||
3918 IC->getOpcode() == Instruction::SetNE) &&
3919 isa<ConstantInt>(IC->getOperand(1)) &&
3920 cast<Constant>(IC->getOperand(1))->isNullValue())
3921 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
3922 if (ICA->getOpcode() == Instruction::And &&
3923 isa<ConstantInt>(ICA->getOperand(1)) &&
3924 (ICA->getOperand(1) == TrueValC ||
3925 ICA->getOperand(1) == FalseValC) &&
3926 isOneBitSet(cast<ConstantInt>(ICA->getOperand(1)))) {
3927 // Okay, now we know that everything is set up, we just don't
3928 // know whether we have a setne or seteq and whether the true or
3929 // false val is the zero.
3930 bool ShouldNotVal = !TrueValC->isNullValue();
3931 ShouldNotVal ^= IC->getOpcode() == Instruction::SetNE;
3934 V = InsertNewInstBefore(BinaryOperator::create(
3935 Instruction::Xor, V, ICA->getOperand(1)), SI);
3936 return ReplaceInstUsesWith(SI, V);
3940 // See if we are selecting two values based on a comparison of the two values.
3941 if (SetCondInst *SCI = dyn_cast<SetCondInst>(CondVal)) {
3942 if (SCI->getOperand(0) == TrueVal && SCI->getOperand(1) == FalseVal) {
3943 // Transform (X == Y) ? X : Y -> Y
3944 if (SCI->getOpcode() == Instruction::SetEQ)
3945 return ReplaceInstUsesWith(SI, FalseVal);
3946 // Transform (X != Y) ? X : Y -> X
3947 if (SCI->getOpcode() == Instruction::SetNE)
3948 return ReplaceInstUsesWith(SI, TrueVal);
3949 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
3951 } else if (SCI->getOperand(0) == FalseVal && SCI->getOperand(1) == TrueVal){
3952 // Transform (X == Y) ? Y : X -> X
3953 if (SCI->getOpcode() == Instruction::SetEQ)
3954 return ReplaceInstUsesWith(SI, FalseVal);
3955 // Transform (X != Y) ? Y : X -> Y
3956 if (SCI->getOpcode() == Instruction::SetNE)
3957 return ReplaceInstUsesWith(SI, TrueVal);
3958 // NOTE: if we wanted to, this is where to detect MIN/MAX/ABS/etc.
3962 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
3963 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
3964 if (TI->hasOneUse() && FI->hasOneUse()) {
3965 bool isInverse = false;
3966 Instruction *AddOp = 0, *SubOp = 0;
3968 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
3969 if (TI->getOpcode() == FI->getOpcode())
3970 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
3973 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
3974 // even legal for FP.
3975 if (TI->getOpcode() == Instruction::Sub &&
3976 FI->getOpcode() == Instruction::Add) {
3977 AddOp = FI; SubOp = TI;
3978 } else if (FI->getOpcode() == Instruction::Sub &&
3979 TI->getOpcode() == Instruction::Add) {
3980 AddOp = TI; SubOp = FI;
3984 Value *OtherAddOp = 0;
3985 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
3986 OtherAddOp = AddOp->getOperand(1);
3987 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
3988 OtherAddOp = AddOp->getOperand(0);
3992 // So at this point we know we have:
3993 // select C, (add X, Y), (sub X, ?)
3994 // We can do the transform profitably if either 'Y' = '?' or '?' is
3996 if (SubOp->getOperand(1) == AddOp ||
3997 isa<Constant>(SubOp->getOperand(1))) {
3999 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
4000 NegVal = ConstantExpr::getNeg(C);
4002 NegVal = InsertNewInstBefore(
4003 BinaryOperator::createNeg(SubOp->getOperand(1)), SI);
4006 Value *NewTrueOp = OtherAddOp;
4007 Value *NewFalseOp = NegVal;
4009 std::swap(NewTrueOp, NewFalseOp);
4010 Instruction *NewSel =
4011 new SelectInst(CondVal, NewTrueOp,NewFalseOp,SI.getName()+".p");
4013 NewSel = InsertNewInstBefore(NewSel, SI);
4014 return BinaryOperator::createAdd(SubOp->getOperand(0), NewSel);
4020 // See if we can fold the select into one of our operands.
4021 if (SI.getType()->isInteger()) {
4022 // See the comment above GetSelectFoldableOperands for a description of the
4023 // transformation we are doing here.
4024 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal))
4025 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
4026 !isa<Constant>(FalseVal))
4027 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
4028 unsigned OpToFold = 0;
4029 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
4031 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
4036 Constant *C = GetSelectFoldableConstant(TVI);
4037 std::string Name = TVI->getName(); TVI->setName("");
4038 Instruction *NewSel =
4039 new SelectInst(SI.getCondition(), TVI->getOperand(2-OpToFold), C,
4041 InsertNewInstBefore(NewSel, SI);
4042 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
4043 return BinaryOperator::create(BO->getOpcode(), FalseVal, NewSel);
4044 else if (ShiftInst *SI = dyn_cast<ShiftInst>(TVI))
4045 return new ShiftInst(SI->getOpcode(), FalseVal, NewSel);
4047 assert(0 && "Unknown instruction!!");
4052 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal))
4053 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
4054 !isa<Constant>(TrueVal))
4055 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
4056 unsigned OpToFold = 0;
4057 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
4059 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
4064 Constant *C = GetSelectFoldableConstant(FVI);
4065 std::string Name = FVI->getName(); FVI->setName("");
4066 Instruction *NewSel =
4067 new SelectInst(SI.getCondition(), C, FVI->getOperand(2-OpToFold),
4069 InsertNewInstBefore(NewSel, SI);
4070 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
4071 return BinaryOperator::create(BO->getOpcode(), TrueVal, NewSel);
4072 else if (ShiftInst *SI = dyn_cast<ShiftInst>(FVI))
4073 return new ShiftInst(SI->getOpcode(), TrueVal, NewSel);
4075 assert(0 && "Unknown instruction!!");
4081 if (BinaryOperator::isNot(CondVal)) {
4082 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
4083 SI.setOperand(1, FalseVal);
4084 SI.setOperand(2, TrueVal);
4092 // CallInst simplification
4094 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
4095 // Intrinsics cannot occur in an invoke, so handle them here instead of in
4097 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&CI)) {
4098 bool Changed = false;
4100 // memmove/cpy/set of zero bytes is a noop.
4101 if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
4102 if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
4104 // FIXME: Increase alignment here.
4106 if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
4107 if (CI->getRawValue() == 1) {
4108 // Replace the instruction with just byte operations. We would
4109 // transform other cases to loads/stores, but we don't know if
4110 // alignment is sufficient.
4114 // If we have a memmove and the source operation is a constant global,
4115 // then the source and dest pointers can't alias, so we can change this
4116 // into a call to memcpy.
4117 if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI))
4118 if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
4119 if (GVSrc->isConstant()) {
4120 Module *M = CI.getParent()->getParent()->getParent();
4121 Function *MemCpy = M->getOrInsertFunction("llvm.memcpy",
4122 CI.getCalledFunction()->getFunctionType());
4123 CI.setOperand(0, MemCpy);
4127 if (Changed) return &CI;
4128 } else if (DbgStopPointInst *SPI = dyn_cast<DbgStopPointInst>(&CI)) {
4129 // If this stoppoint is at the same source location as the previous
4130 // stoppoint in the chain, it is not needed.
4131 if (DbgStopPointInst *PrevSPI =
4132 dyn_cast<DbgStopPointInst>(SPI->getChain()))
4133 if (SPI->getLineNo() == PrevSPI->getLineNo() &&
4134 SPI->getColNo() == PrevSPI->getColNo()) {
4135 SPI->replaceAllUsesWith(PrevSPI);
4136 return EraseInstFromFunction(CI);
4140 return visitCallSite(&CI);
4143 // InvokeInst simplification
4145 Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
4146 return visitCallSite(&II);
4149 // visitCallSite - Improvements for call and invoke instructions.
4151 Instruction *InstCombiner::visitCallSite(CallSite CS) {
4152 bool Changed = false;
4154 // If the callee is a constexpr cast of a function, attempt to move the cast
4155 // to the arguments of the call/invoke.
4156 if (transformConstExprCastCall(CS)) return 0;
4158 Value *Callee = CS.getCalledValue();
4160 if (Function *CalleeF = dyn_cast<Function>(Callee))
4161 if (CalleeF->getCallingConv() != CS.getCallingConv()) {
4162 Instruction *OldCall = CS.getInstruction();
4163 // If the call and callee calling conventions don't match, this call must
4164 // be unreachable, as the call is undefined.
4165 new StoreInst(ConstantBool::True,
4166 UndefValue::get(PointerType::get(Type::BoolTy)), OldCall);
4167 if (!OldCall->use_empty())
4168 OldCall->replaceAllUsesWith(UndefValue::get(OldCall->getType()));
4169 if (isa<CallInst>(OldCall)) // Not worth removing an invoke here.
4170 return EraseInstFromFunction(*OldCall);
4174 if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
4175 // This instruction is not reachable, just remove it. We insert a store to
4176 // undef so that we know that this code is not reachable, despite the fact
4177 // that we can't modify the CFG here.
4178 new StoreInst(ConstantBool::True,
4179 UndefValue::get(PointerType::get(Type::BoolTy)),
4180 CS.getInstruction());
4182 if (!CS.getInstruction()->use_empty())
4183 CS.getInstruction()->
4184 replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
4186 if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
4187 // Don't break the CFG, insert a dummy cond branch.
4188 new BranchInst(II->getNormalDest(), II->getUnwindDest(),
4189 ConstantBool::True, II);
4191 return EraseInstFromFunction(*CS.getInstruction());
4194 const PointerType *PTy = cast<PointerType>(Callee->getType());
4195 const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
4196 if (FTy->isVarArg()) {
4197 // See if we can optimize any arguments passed through the varargs area of
4199 for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
4200 E = CS.arg_end(); I != E; ++I)
4201 if (CastInst *CI = dyn_cast<CastInst>(*I)) {
4202 // If this cast does not effect the value passed through the varargs
4203 // area, we can eliminate the use of the cast.
4204 Value *Op = CI->getOperand(0);
4205 if (CI->getType()->isLosslesslyConvertibleTo(Op->getType())) {
4212 return Changed ? CS.getInstruction() : 0;
4215 // transformConstExprCastCall - If the callee is a constexpr cast of a function,
4216 // attempt to move the cast to the arguments of the call/invoke.
4218 bool InstCombiner::transformConstExprCastCall(CallSite CS) {
4219 if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
4220 ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
4221 if (CE->getOpcode() != Instruction::Cast || !isa<Function>(CE->getOperand(0)))
4223 Function *Callee = cast<Function>(CE->getOperand(0));
4224 Instruction *Caller = CS.getInstruction();
4226 // Okay, this is a cast from a function to a different type. Unless doing so
4227 // would cause a type conversion of one of our arguments, change this call to
4228 // be a direct call with arguments casted to the appropriate types.
4230 const FunctionType *FT = Callee->getFunctionType();
4231 const Type *OldRetTy = Caller->getType();
4233 // Check to see if we are changing the return type...
4234 if (OldRetTy != FT->getReturnType()) {
4235 if (Callee->isExternal() &&
4236 !OldRetTy->isLosslesslyConvertibleTo(FT->getReturnType()) &&
4237 !Caller->use_empty())
4238 return false; // Cannot transform this return value...
4240 // If the callsite is an invoke instruction, and the return value is used by
4241 // a PHI node in a successor, we cannot change the return type of the call
4242 // because there is no place to put the cast instruction (without breaking
4243 // the critical edge). Bail out in this case.
4244 if (!Caller->use_empty())
4245 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
4246 for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
4248 if (PHINode *PN = dyn_cast<PHINode>(*UI))
4249 if (PN->getParent() == II->getNormalDest() ||
4250 PN->getParent() == II->getUnwindDest())
4254 unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
4255 unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
4257 CallSite::arg_iterator AI = CS.arg_begin();
4258 for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
4259 const Type *ParamTy = FT->getParamType(i);
4260 bool isConvertible = (*AI)->getType()->isLosslesslyConvertibleTo(ParamTy);
4261 if (Callee->isExternal() && !isConvertible) return false;
4264 if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
4265 Callee->isExternal())
4266 return false; // Do not delete arguments unless we have a function body...
4268 // Okay, we decided that this is a safe thing to do: go ahead and start
4269 // inserting cast instructions as necessary...
4270 std::vector<Value*> Args;
4271 Args.reserve(NumActualArgs);
4273 AI = CS.arg_begin();
4274 for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
4275 const Type *ParamTy = FT->getParamType(i);
4276 if ((*AI)->getType() == ParamTy) {
4277 Args.push_back(*AI);
4279 Args.push_back(InsertNewInstBefore(new CastInst(*AI, ParamTy, "tmp"),
4284 // If the function takes more arguments than the call was taking, add them
4286 for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
4287 Args.push_back(Constant::getNullValue(FT->getParamType(i)));
4289 // If we are removing arguments to the function, emit an obnoxious warning...
4290 if (FT->getNumParams() < NumActualArgs)
4291 if (!FT->isVarArg()) {
4292 std::cerr << "WARNING: While resolving call to function '"
4293 << Callee->getName() << "' arguments were dropped!\n";
4295 // Add all of the arguments in their promoted form to the arg list...
4296 for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
4297 const Type *PTy = getPromotedType((*AI)->getType());
4298 if (PTy != (*AI)->getType()) {
4299 // Must promote to pass through va_arg area!
4300 Instruction *Cast = new CastInst(*AI, PTy, "tmp");
4301 InsertNewInstBefore(Cast, *Caller);
4302 Args.push_back(Cast);
4304 Args.push_back(*AI);
4309 if (FT->getReturnType() == Type::VoidTy)
4310 Caller->setName(""); // Void type should not have a name...
4313 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
4314 NC = new InvokeInst(Callee, II->getNormalDest(), II->getUnwindDest(),
4315 Args, Caller->getName(), Caller);
4316 cast<InvokeInst>(II)->setCallingConv(II->getCallingConv());
4318 NC = new CallInst(Callee, Args, Caller->getName(), Caller);
4319 if (cast<CallInst>(Caller)->isTailCall())
4320 cast<CallInst>(NC)->setTailCall();
4321 cast<CallInst>(NC)->setCallingConv(cast<CallInst>(Caller)->getCallingConv());
4324 // Insert a cast of the return type as necessary...
4326 if (Caller->getType() != NV->getType() && !Caller->use_empty()) {
4327 if (NV->getType() != Type::VoidTy) {
4328 NV = NC = new CastInst(NC, Caller->getType(), "tmp");
4330 // If this is an invoke instruction, we should insert it after the first
4331 // non-phi, instruction in the normal successor block.
4332 if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
4333 BasicBlock::iterator I = II->getNormalDest()->begin();
4334 while (isa<PHINode>(I)) ++I;
4335 InsertNewInstBefore(NC, *I);
4337 // Otherwise, it's a call, just insert cast right after the call instr
4338 InsertNewInstBefore(NC, *Caller);
4340 AddUsersToWorkList(*Caller);
4342 NV = UndefValue::get(Caller->getType());
4346 if (Caller->getType() != Type::VoidTy && !Caller->use_empty())
4347 Caller->replaceAllUsesWith(NV);
4348 Caller->getParent()->getInstList().erase(Caller);
4349 removeFromWorkList(Caller);
4354 // FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
4355 // operator and they all are only used by the PHI, PHI together their
4356 // inputs, and do the operation once, to the result of the PHI.
4357 Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
4358 Instruction *FirstInst = cast<Instruction>(PN.getIncomingValue(0));
4360 // Scan the instruction, looking for input operations that can be folded away.
4361 // If all input operands to the phi are the same instruction (e.g. a cast from
4362 // the same type or "+42") we can pull the operation through the PHI, reducing
4363 // code size and simplifying code.
4364 Constant *ConstantOp = 0;
4365 const Type *CastSrcTy = 0;
4366 if (isa<CastInst>(FirstInst)) {
4367 CastSrcTy = FirstInst->getOperand(0)->getType();
4368 } else if (isa<BinaryOperator>(FirstInst) || isa<ShiftInst>(FirstInst)) {
4369 // Can fold binop or shift if the RHS is a constant.
4370 ConstantOp = dyn_cast<Constant>(FirstInst->getOperand(1));
4371 if (ConstantOp == 0) return 0;
4373 return 0; // Cannot fold this operation.
4376 // Check to see if all arguments are the same operation.
4377 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
4378 if (!isa<Instruction>(PN.getIncomingValue(i))) return 0;
4379 Instruction *I = cast<Instruction>(PN.getIncomingValue(i));
4380 if (!I->hasOneUse() || I->getOpcode() != FirstInst->getOpcode())
4383 if (I->getOperand(0)->getType() != CastSrcTy)
4384 return 0; // Cast operation must match.
4385 } else if (I->getOperand(1) != ConstantOp) {
4390 // Okay, they are all the same operation. Create a new PHI node of the
4391 // correct type, and PHI together all of the LHS's of the instructions.
4392 PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(),
4393 PN.getName()+".in");
4394 NewPN->reserveOperandSpace(PN.getNumOperands()/2);
4396 Value *InVal = FirstInst->getOperand(0);
4397 NewPN->addIncoming(InVal, PN.getIncomingBlock(0));
4399 // Add all operands to the new PHI.
4400 for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) {
4401 Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0);
4402 if (NewInVal != InVal)
4404 NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i));
4409 // The new PHI unions all of the same values together. This is really
4410 // common, so we handle it intelligently here for compile-time speed.
4414 InsertNewInstBefore(NewPN, PN);
4418 // Insert and return the new operation.
4419 if (isa<CastInst>(FirstInst))
4420 return new CastInst(PhiVal, PN.getType());
4421 else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
4422 return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
4424 return new ShiftInst(cast<ShiftInst>(FirstInst)->getOpcode(),
4425 PhiVal, ConstantOp);
4428 /// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
4430 static bool DeadPHICycle(PHINode *PN, std::set<PHINode*> &PotentiallyDeadPHIs) {
4431 if (PN->use_empty()) return true;
4432 if (!PN->hasOneUse()) return false;
4434 // Remember this node, and if we find the cycle, return.
4435 if (!PotentiallyDeadPHIs.insert(PN).second)
4438 if (PHINode *PU = dyn_cast<PHINode>(PN->use_back()))
4439 return DeadPHICycle(PU, PotentiallyDeadPHIs);
4444 // PHINode simplification
4446 Instruction *InstCombiner::visitPHINode(PHINode &PN) {
4447 if (Value *V = PN.hasConstantValue())
4448 return ReplaceInstUsesWith(PN, V);
4450 // If the only user of this instruction is a cast instruction, and all of the
4451 // incoming values are constants, change this PHI to merge together the casted
4454 if (CastInst *CI = dyn_cast<CastInst>(PN.use_back()))
4455 if (CI->getType() != PN.getType()) { // noop casts will be folded
4456 bool AllConstant = true;
4457 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
4458 if (!isa<Constant>(PN.getIncomingValue(i))) {
4459 AllConstant = false;
4463 // Make a new PHI with all casted values.
4464 PHINode *New = new PHINode(CI->getType(), PN.getName(), &PN);
4465 for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
4466 Constant *OldArg = cast<Constant>(PN.getIncomingValue(i));
4467 New->addIncoming(ConstantExpr::getCast(OldArg, New->getType()),
4468 PN.getIncomingBlock(i));
4471 // Update the cast instruction.
4472 CI->setOperand(0, New);
4473 WorkList.push_back(CI); // revisit the cast instruction to fold.
4474 WorkList.push_back(New); // Make sure to revisit the new Phi
4475 return &PN; // PN is now dead!
4479 // If all PHI operands are the same operation, pull them through the PHI,
4480 // reducing code size.
4481 if (isa<Instruction>(PN.getIncomingValue(0)) &&
4482 PN.getIncomingValue(0)->hasOneUse())
4483 if (Instruction *Result = FoldPHIArgOpIntoPHI(PN))
4486 // If this is a trivial cycle in the PHI node graph, remove it. Basically, if
4487 // this PHI only has a single use (a PHI), and if that PHI only has one use (a
4488 // PHI)... break the cycle.
4490 if (PHINode *PU = dyn_cast<PHINode>(PN.use_back())) {
4491 std::set<PHINode*> PotentiallyDeadPHIs;
4492 PotentiallyDeadPHIs.insert(&PN);
4493 if (DeadPHICycle(PU, PotentiallyDeadPHIs))
4494 return ReplaceInstUsesWith(PN, UndefValue::get(PN.getType()));
4500 static Value *InsertSignExtendToPtrTy(Value *V, const Type *DTy,
4501 Instruction *InsertPoint,
4503 unsigned PS = IC->getTargetData().getPointerSize();
4504 const Type *VTy = V->getType();
4505 if (!VTy->isSigned() && VTy->getPrimitiveSize() < PS)
4506 // We must insert a cast to ensure we sign-extend.
4507 V = IC->InsertNewInstBefore(new CastInst(V, VTy->getSignedVersion(),
4508 V->getName()), *InsertPoint);
4509 return IC->InsertNewInstBefore(new CastInst(V, DTy, V->getName()),
4514 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
4515 Value *PtrOp = GEP.getOperand(0);
4516 // Is it 'getelementptr %P, long 0' or 'getelementptr %P'
4517 // If so, eliminate the noop.
4518 if (GEP.getNumOperands() == 1)
4519 return ReplaceInstUsesWith(GEP, PtrOp);
4521 if (isa<UndefValue>(GEP.getOperand(0)))
4522 return ReplaceInstUsesWith(GEP, UndefValue::get(GEP.getType()));
4524 bool HasZeroPointerIndex = false;
4525 if (Constant *C = dyn_cast<Constant>(GEP.getOperand(1)))
4526 HasZeroPointerIndex = C->isNullValue();
4528 if (GEP.getNumOperands() == 2 && HasZeroPointerIndex)
4529 return ReplaceInstUsesWith(GEP, PtrOp);
4531 // Eliminate unneeded casts for indices.
4532 bool MadeChange = false;
4533 gep_type_iterator GTI = gep_type_begin(GEP);
4534 for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i, ++GTI)
4535 if (isa<SequentialType>(*GTI)) {
4536 if (CastInst *CI = dyn_cast<CastInst>(GEP.getOperand(i))) {
4537 Value *Src = CI->getOperand(0);
4538 const Type *SrcTy = Src->getType();
4539 const Type *DestTy = CI->getType();
4540 if (Src->getType()->isInteger()) {
4541 if (SrcTy->getPrimitiveSizeInBits() ==
4542 DestTy->getPrimitiveSizeInBits()) {
4543 // We can always eliminate a cast from ulong or long to the other.
4544 // We can always eliminate a cast from uint to int or the other on
4545 // 32-bit pointer platforms.
4546 if (DestTy->getPrimitiveSizeInBits() >= TD->getPointerSizeInBits()){
4548 GEP.setOperand(i, Src);
4550 } else if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
4551 SrcTy->getPrimitiveSize() == 4) {
4552 // We can always eliminate a cast from int to [u]long. We can
4553 // eliminate a cast from uint to [u]long iff the target is a 32-bit
4555 if (SrcTy->isSigned() ||
4556 SrcTy->getPrimitiveSizeInBits() >= TD->getPointerSizeInBits()) {
4558 GEP.setOperand(i, Src);
4563 // If we are using a wider index than needed for this platform, shrink it
4564 // to what we need. If the incoming value needs a cast instruction,
4565 // insert it. This explicit cast can make subsequent optimizations more
4567 Value *Op = GEP.getOperand(i);
4568 if (Op->getType()->getPrimitiveSize() > TD->getPointerSize())
4569 if (Constant *C = dyn_cast<Constant>(Op)) {
4570 GEP.setOperand(i, ConstantExpr::getCast(C,
4571 TD->getIntPtrType()->getSignedVersion()));
4574 Op = InsertNewInstBefore(new CastInst(Op, TD->getIntPtrType(),
4575 Op->getName()), GEP);
4576 GEP.setOperand(i, Op);
4580 // If this is a constant idx, make sure to canonicalize it to be a signed
4581 // operand, otherwise CSE and other optimizations are pessimized.
4582 if (ConstantUInt *CUI = dyn_cast<ConstantUInt>(Op)) {
4583 GEP.setOperand(i, ConstantExpr::getCast(CUI,
4584 CUI->getType()->getSignedVersion()));
4588 if (MadeChange) return &GEP;
4590 // Combine Indices - If the source pointer to this getelementptr instruction
4591 // is a getelementptr instruction, combine the indices of the two
4592 // getelementptr instructions into a single instruction.
4594 std::vector<Value*> SrcGEPOperands;
4595 if (User *Src = dyn_castGetElementPtr(PtrOp))
4596 SrcGEPOperands.assign(Src->op_begin(), Src->op_end());
4598 if (!SrcGEPOperands.empty()) {
4599 // Note that if our source is a gep chain itself that we wait for that
4600 // chain to be resolved before we perform this transformation. This
4601 // avoids us creating a TON of code in some cases.
4603 if (isa<GetElementPtrInst>(SrcGEPOperands[0]) &&
4604 cast<Instruction>(SrcGEPOperands[0])->getNumOperands() == 2)
4605 return 0; // Wait until our source is folded to completion.
4607 std::vector<Value *> Indices;
4609 // Find out whether the last index in the source GEP is a sequential idx.
4610 bool EndsWithSequential = false;
4611 for (gep_type_iterator I = gep_type_begin(*cast<User>(PtrOp)),
4612 E = gep_type_end(*cast<User>(PtrOp)); I != E; ++I)
4613 EndsWithSequential = !isa<StructType>(*I);
4615 // Can we combine the two pointer arithmetics offsets?
4616 if (EndsWithSequential) {
4617 // Replace: gep (gep %P, long B), long A, ...
4618 // With: T = long A+B; gep %P, T, ...
4620 Value *Sum, *SO1 = SrcGEPOperands.back(), *GO1 = GEP.getOperand(1);
4621 if (SO1 == Constant::getNullValue(SO1->getType())) {
4623 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
4626 // If they aren't the same type, convert both to an integer of the
4627 // target's pointer size.
4628 if (SO1->getType() != GO1->getType()) {
4629 if (Constant *SO1C = dyn_cast<Constant>(SO1)) {
4630 SO1 = ConstantExpr::getCast(SO1C, GO1->getType());
4631 } else if (Constant *GO1C = dyn_cast<Constant>(GO1)) {
4632 GO1 = ConstantExpr::getCast(GO1C, SO1->getType());
4634 unsigned PS = TD->getPointerSize();
4635 if (SO1->getType()->getPrimitiveSize() == PS) {
4636 // Convert GO1 to SO1's type.
4637 GO1 = InsertSignExtendToPtrTy(GO1, SO1->getType(), &GEP, this);
4639 } else if (GO1->getType()->getPrimitiveSize() == PS) {
4640 // Convert SO1 to GO1's type.
4641 SO1 = InsertSignExtendToPtrTy(SO1, GO1->getType(), &GEP, this);
4643 const Type *PT = TD->getIntPtrType();
4644 SO1 = InsertSignExtendToPtrTy(SO1, PT, &GEP, this);
4645 GO1 = InsertSignExtendToPtrTy(GO1, PT, &GEP, this);
4649 if (isa<Constant>(SO1) && isa<Constant>(GO1))
4650 Sum = ConstantExpr::getAdd(cast<Constant>(SO1), cast<Constant>(GO1));
4652 Sum = BinaryOperator::createAdd(SO1, GO1, PtrOp->getName()+".sum");
4653 InsertNewInstBefore(cast<Instruction>(Sum), GEP);
4657 // Recycle the GEP we already have if possible.
4658 if (SrcGEPOperands.size() == 2) {
4659 GEP.setOperand(0, SrcGEPOperands[0]);
4660 GEP.setOperand(1, Sum);
4663 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
4664 SrcGEPOperands.end()-1);
4665 Indices.push_back(Sum);
4666 Indices.insert(Indices.end(), GEP.op_begin()+2, GEP.op_end());
4668 } else if (isa<Constant>(*GEP.idx_begin()) &&
4669 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
4670 SrcGEPOperands.size() != 1) {
4671 // Otherwise we can do the fold if the first index of the GEP is a zero
4672 Indices.insert(Indices.end(), SrcGEPOperands.begin()+1,
4673 SrcGEPOperands.end());
4674 Indices.insert(Indices.end(), GEP.idx_begin()+1, GEP.idx_end());
4677 if (!Indices.empty())
4678 return new GetElementPtrInst(SrcGEPOperands[0], Indices, GEP.getName());
4680 } else if (GlobalValue *GV = dyn_cast<GlobalValue>(PtrOp)) {
4681 // GEP of global variable. If all of the indices for this GEP are
4682 // constants, we can promote this to a constexpr instead of an instruction.
4684 // Scan for nonconstants...
4685 std::vector<Constant*> Indices;
4686 User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
4687 for (; I != E && isa<Constant>(*I); ++I)
4688 Indices.push_back(cast<Constant>(*I));
4690 if (I == E) { // If they are all constants...
4691 Constant *CE = ConstantExpr::getGetElementPtr(GV, Indices);
4693 // Replace all uses of the GEP with the new constexpr...
4694 return ReplaceInstUsesWith(GEP, CE);
4696 } else if (Value *X = isCast(PtrOp)) { // Is the operand a cast?
4697 if (!isa<PointerType>(X->getType())) {
4698 // Not interesting. Source pointer must be a cast from pointer.
4699 } else if (HasZeroPointerIndex) {
4700 // transform: GEP (cast [10 x ubyte]* X to [0 x ubyte]*), long 0, ...
4701 // into : GEP [10 x ubyte]* X, long 0, ...
4703 // This occurs when the program declares an array extern like "int X[];"
4705 const PointerType *CPTy = cast<PointerType>(PtrOp->getType());
4706 const PointerType *XTy = cast<PointerType>(X->getType());
4707 if (const ArrayType *XATy =
4708 dyn_cast<ArrayType>(XTy->getElementType()))
4709 if (const ArrayType *CATy =
4710 dyn_cast<ArrayType>(CPTy->getElementType()))
4711 if (CATy->getElementType() == XATy->getElementType()) {
4712 // At this point, we know that the cast source type is a pointer
4713 // to an array of the same type as the destination pointer
4714 // array. Because the array type is never stepped over (there
4715 // is a leading zero) we can fold the cast into this GEP.
4716 GEP.setOperand(0, X);
4719 } else if (GEP.getNumOperands() == 2) {
4720 // Transform things like:
4721 // %t = getelementptr ubyte* cast ([2 x int]* %str to uint*), uint %V
4722 // into: %t1 = getelementptr [2 x int*]* %str, int 0, uint %V; cast
4723 const Type *SrcElTy = cast<PointerType>(X->getType())->getElementType();
4724 const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType();
4725 if (isa<ArrayType>(SrcElTy) &&
4726 TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType()) ==
4727 TD->getTypeSize(ResElTy)) {
4728 Value *V = InsertNewInstBefore(
4729 new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
4730 GEP.getOperand(1), GEP.getName()), GEP);
4731 return new CastInst(V, GEP.getType());
4734 // Transform things like:
4735 // getelementptr sbyte* cast ([100 x double]* X to sbyte*), int %tmp
4736 // (where tmp = 8*tmp2) into:
4737 // getelementptr [100 x double]* %arr, int 0, int %tmp.2
4739 if (isa<ArrayType>(SrcElTy) &&
4740 (ResElTy == Type::SByteTy || ResElTy == Type::UByteTy)) {
4741 uint64_t ArrayEltSize =
4742 TD->getTypeSize(cast<ArrayType>(SrcElTy)->getElementType());
4744 // Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We
4745 // allow either a mul, shift, or constant here.
4747 ConstantInt *Scale = 0;
4748 if (ArrayEltSize == 1) {
4749 NewIdx = GEP.getOperand(1);
4750 Scale = ConstantInt::get(NewIdx->getType(), 1);
4751 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) {
4752 NewIdx = ConstantInt::get(NewIdx->getType(), 1);
4754 } else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){
4755 if (Inst->getOpcode() == Instruction::Shl &&
4756 isa<ConstantInt>(Inst->getOperand(1))) {
4757 unsigned ShAmt =cast<ConstantUInt>(Inst->getOperand(1))->getValue();
4758 if (Inst->getType()->isSigned())
4759 Scale = ConstantSInt::get(Inst->getType(), 1ULL << ShAmt);
4761 Scale = ConstantUInt::get(Inst->getType(), 1ULL << ShAmt);
4762 NewIdx = Inst->getOperand(0);
4763 } else if (Inst->getOpcode() == Instruction::Mul &&
4764 isa<ConstantInt>(Inst->getOperand(1))) {
4765 Scale = cast<ConstantInt>(Inst->getOperand(1));
4766 NewIdx = Inst->getOperand(0);
4770 // If the index will be to exactly the right offset with the scale taken
4771 // out, perform the transformation.
4772 if (Scale && Scale->getRawValue() % ArrayEltSize == 0) {
4773 if (ConstantSInt *C = dyn_cast<ConstantSInt>(Scale))
4774 Scale = ConstantSInt::get(C->getType(),
4775 C->getRawValue()/(int64_t)ArrayEltSize);
4777 Scale = ConstantUInt::get(Scale->getType(),
4778 Scale->getRawValue() / ArrayEltSize);
4779 if (Scale->getRawValue() != 1) {
4780 Constant *C = ConstantExpr::getCast(Scale, NewIdx->getType());
4781 Instruction *Sc = BinaryOperator::createMul(NewIdx, C, "idxscale");
4782 NewIdx = InsertNewInstBefore(Sc, GEP);
4785 // Insert the new GEP instruction.
4787 new GetElementPtrInst(X, Constant::getNullValue(Type::IntTy),
4788 NewIdx, GEP.getName());
4789 Idx = InsertNewInstBefore(Idx, GEP);
4790 return new CastInst(Idx, GEP.getType());
4799 Instruction *InstCombiner::visitAllocationInst(AllocationInst &AI) {
4800 // Convert: malloc Ty, C - where C is a constant != 1 into: malloc [C x Ty], 1
4801 if (AI.isArrayAllocation()) // Check C != 1
4802 if (const ConstantUInt *C = dyn_cast<ConstantUInt>(AI.getArraySize())) {
4803 const Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getValue());
4804 AllocationInst *New = 0;
4806 // Create and insert the replacement instruction...
4807 if (isa<MallocInst>(AI))
4808 New = new MallocInst(NewTy, 0, AI.getName());
4810 assert(isa<AllocaInst>(AI) && "Unknown type of allocation inst!");
4811 New = new AllocaInst(NewTy, 0, AI.getName());
4814 InsertNewInstBefore(New, AI);
4816 // Scan to the end of the allocation instructions, to skip over a block of
4817 // allocas if possible...
4819 BasicBlock::iterator It = New;
4820 while (isa<AllocationInst>(*It)) ++It;
4822 // Now that I is pointing to the first non-allocation-inst in the block,
4823 // insert our getelementptr instruction...
4825 Value *NullIdx = Constant::getNullValue(Type::IntTy);
4826 Value *V = new GetElementPtrInst(New, NullIdx, NullIdx,
4827 New->getName()+".sub", It);
4829 // Now make everything use the getelementptr instead of the original
4831 return ReplaceInstUsesWith(AI, V);
4832 } else if (isa<UndefValue>(AI.getArraySize())) {
4833 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
4836 // If alloca'ing a zero byte object, replace the alloca with a null pointer.
4837 // Note that we only do this for alloca's, because malloc should allocate and
4838 // return a unique pointer, even for a zero byte allocation.
4839 if (isa<AllocaInst>(AI) && AI.getAllocatedType()->isSized() &&
4840 TD->getTypeSize(AI.getAllocatedType()) == 0)
4841 return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType()));
4846 Instruction *InstCombiner::visitFreeInst(FreeInst &FI) {
4847 Value *Op = FI.getOperand(0);
4849 // Change free <ty>* (cast <ty2>* X to <ty>*) into free <ty2>* X
4850 if (CastInst *CI = dyn_cast<CastInst>(Op))
4851 if (isa<PointerType>(CI->getOperand(0)->getType())) {
4852 FI.setOperand(0, CI->getOperand(0));
4856 // free undef -> unreachable.
4857 if (isa<UndefValue>(Op)) {
4858 // Insert a new store to null because we cannot modify the CFG here.
4859 new StoreInst(ConstantBool::True,
4860 UndefValue::get(PointerType::get(Type::BoolTy)), &FI);
4861 return EraseInstFromFunction(FI);
4864 // If we have 'free null' delete the instruction. This can happen in stl code
4865 // when lots of inlining happens.
4866 if (isa<ConstantPointerNull>(Op))
4867 return EraseInstFromFunction(FI);
4873 /// GetGEPGlobalInitializer - Given a constant, and a getelementptr
4874 /// constantexpr, return the constant value being addressed by the constant
4875 /// expression, or null if something is funny.
4877 static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
4878 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
4879 return 0; // Do not allow stepping over the value!
4881 // Loop over all of the operands, tracking down which value we are
4883 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
4884 for (++I; I != E; ++I)
4885 if (const StructType *STy = dyn_cast<StructType>(*I)) {
4886 ConstantUInt *CU = cast<ConstantUInt>(I.getOperand());
4887 assert(CU->getValue() < STy->getNumElements() &&
4888 "Struct index out of range!");
4889 unsigned El = (unsigned)CU->getValue();
4890 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
4891 C = CS->getOperand(El);
4892 } else if (isa<ConstantAggregateZero>(C)) {
4893 C = Constant::getNullValue(STy->getElementType(El));
4894 } else if (isa<UndefValue>(C)) {
4895 C = UndefValue::get(STy->getElementType(El));
4899 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
4900 const ArrayType *ATy = cast<ArrayType>(*I);
4901 if ((uint64_t)CI->getRawValue() >= ATy->getNumElements()) return 0;
4902 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
4903 C = CA->getOperand((unsigned)CI->getRawValue());
4904 else if (isa<ConstantAggregateZero>(C))
4905 C = Constant::getNullValue(ATy->getElementType());
4906 else if (isa<UndefValue>(C))
4907 C = UndefValue::get(ATy->getElementType());
4916 /// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible.
4917 static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
4918 User *CI = cast<User>(LI.getOperand(0));
4919 Value *CastOp = CI->getOperand(0);
4921 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
4922 if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
4923 const Type *SrcPTy = SrcTy->getElementType();
4925 if (DestPTy->isInteger() || isa<PointerType>(DestPTy)) {
4926 // If the source is an array, the code below will not succeed. Check to
4927 // see if a trivial 'gep P, 0, 0' will help matters. Only do this for
4929 if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
4930 if (Constant *CSrc = dyn_cast<Constant>(CastOp))
4931 if (ASrcTy->getNumElements() != 0) {
4932 std::vector<Value*> Idxs(2, Constant::getNullValue(Type::IntTy));
4933 CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs);
4934 SrcTy = cast<PointerType>(CastOp->getType());
4935 SrcPTy = SrcTy->getElementType();
4938 if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
4939 // Do not allow turning this into a load of an integer, which is then
4940 // casted to a pointer, this pessimizes pointer analysis a lot.
4941 (isa<PointerType>(SrcPTy) == isa<PointerType>(LI.getType())) &&
4942 IC.getTargetData().getTypeSize(SrcPTy) ==
4943 IC.getTargetData().getTypeSize(DestPTy)) {
4945 // Okay, we are casting from one integer or pointer type to another of
4946 // the same size. Instead of casting the pointer before the load, cast
4947 // the result of the loaded value.
4948 Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CastOp,
4950 LI.isVolatile()),LI);
4951 // Now cast the result of the load.
4952 return new CastInst(NewLoad, LI.getType());
4959 /// isSafeToLoadUnconditionally - Return true if we know that executing a load
4960 /// from this value cannot trap. If it is not obviously safe to load from the
4961 /// specified pointer, we do a quick local scan of the basic block containing
4962 /// ScanFrom, to determine if the address is already accessed.
4963 static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
4964 // If it is an alloca or global variable, it is always safe to load from.
4965 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
4967 // Otherwise, be a little bit agressive by scanning the local block where we
4968 // want to check to see if the pointer is already being loaded or stored
4969 // from/to. If so, the previous load or store would have already trapped,
4970 // so there is no harm doing an extra load (also, CSE will later eliminate
4971 // the load entirely).
4972 BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
4977 if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
4978 if (LI->getOperand(0) == V) return true;
4979 } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
4980 if (SI->getOperand(1) == V) return true;
4986 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
4987 Value *Op = LI.getOperand(0);
4989 // load (cast X) --> cast (load X) iff safe
4990 if (CastInst *CI = dyn_cast<CastInst>(Op))
4991 if (Instruction *Res = InstCombineLoadCast(*this, LI))
4994 // None of the following transforms are legal for volatile loads.
4995 if (LI.isVolatile()) return 0;
4997 if (&LI.getParent()->front() != &LI) {
4998 BasicBlock::iterator BBI = &LI; --BBI;
4999 // If the instruction immediately before this is a store to the same
5000 // address, do a simple form of store->load forwarding.
5001 if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
5002 if (SI->getOperand(1) == LI.getOperand(0))
5003 return ReplaceInstUsesWith(LI, SI->getOperand(0));
5004 if (LoadInst *LIB = dyn_cast<LoadInst>(BBI))
5005 if (LIB->getOperand(0) == LI.getOperand(0))
5006 return ReplaceInstUsesWith(LI, LIB);
5009 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op))
5010 if (isa<ConstantPointerNull>(GEPI->getOperand(0)) ||
5011 isa<UndefValue>(GEPI->getOperand(0))) {
5012 // Insert a new store to null instruction before the load to indicate
5013 // that this code is not reachable. We do this instead of inserting
5014 // an unreachable instruction directly because we cannot modify the
5016 new StoreInst(UndefValue::get(LI.getType()),
5017 Constant::getNullValue(Op->getType()), &LI);
5018 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
5021 if (Constant *C = dyn_cast<Constant>(Op)) {
5022 // load null/undef -> undef
5023 if ((C->isNullValue() || isa<UndefValue>(C))) {
5024 // Insert a new store to null instruction before the load to indicate that
5025 // this code is not reachable. We do this instead of inserting an
5026 // unreachable instruction directly because we cannot modify the CFG.
5027 new StoreInst(UndefValue::get(LI.getType()),
5028 Constant::getNullValue(Op->getType()), &LI);
5029 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
5032 // Instcombine load (constant global) into the value loaded.
5033 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
5034 if (GV->isConstant() && !GV->isExternal())
5035 return ReplaceInstUsesWith(LI, GV->getInitializer());
5037 // Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
5038 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
5039 if (CE->getOpcode() == Instruction::GetElementPtr) {
5040 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
5041 if (GV->isConstant() && !GV->isExternal())
5042 if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
5043 return ReplaceInstUsesWith(LI, V);
5044 if (CE->getOperand(0)->isNullValue()) {
5045 // Insert a new store to null instruction before the load to indicate
5046 // that this code is not reachable. We do this instead of inserting
5047 // an unreachable instruction directly because we cannot modify the
5049 new StoreInst(UndefValue::get(LI.getType()),
5050 Constant::getNullValue(Op->getType()), &LI);
5051 return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
5054 } else if (CE->getOpcode() == Instruction::Cast) {
5055 if (Instruction *Res = InstCombineLoadCast(*this, LI))
5060 if (Op->hasOneUse()) {
5061 // Change select and PHI nodes to select values instead of addresses: this
5062 // helps alias analysis out a lot, allows many others simplifications, and
5063 // exposes redundancy in the code.
5065 // Note that we cannot do the transformation unless we know that the
5066 // introduced loads cannot trap! Something like this is valid as long as
5067 // the condition is always false: load (select bool %C, int* null, int* %G),
5068 // but it would not be valid if we transformed it to load from null
5071 if (SelectInst *SI = dyn_cast<SelectInst>(Op)) {
5072 // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2).
5073 if (isSafeToLoadUnconditionally(SI->getOperand(1), SI) &&
5074 isSafeToLoadUnconditionally(SI->getOperand(2), SI)) {
5075 Value *V1 = InsertNewInstBefore(new LoadInst(SI->getOperand(1),
5076 SI->getOperand(1)->getName()+".val"), LI);
5077 Value *V2 = InsertNewInstBefore(new LoadInst(SI->getOperand(2),
5078 SI->getOperand(2)->getName()+".val"), LI);
5079 return new SelectInst(SI->getCondition(), V1, V2);
5082 // load (select (cond, null, P)) -> load P
5083 if (Constant *C = dyn_cast<Constant>(SI->getOperand(1)))
5084 if (C->isNullValue()) {
5085 LI.setOperand(0, SI->getOperand(2));
5089 // load (select (cond, P, null)) -> load P
5090 if (Constant *C = dyn_cast<Constant>(SI->getOperand(2)))
5091 if (C->isNullValue()) {
5092 LI.setOperand(0, SI->getOperand(1));
5096 } else if (PHINode *PN = dyn_cast<PHINode>(Op)) {
5097 // load (phi (&V1, &V2, &V3)) --> phi(load &V1, load &V2, load &V3)
5098 bool Safe = PN->getParent() == LI.getParent();
5100 // Scan all of the instructions between the PHI and the load to make
5101 // sure there are no instructions that might possibly alter the value
5102 // loaded from the PHI.
5104 BasicBlock::iterator I = &LI;
5105 for (--I; !isa<PHINode>(I); --I)
5106 if (isa<StoreInst>(I) || isa<CallInst>(I)) {
5112 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e && Safe; ++i)
5113 if (!isSafeToLoadUnconditionally(PN->getIncomingValue(i),
5114 PN->getIncomingBlock(i)->getTerminator()))
5119 PHINode *NewPN = new PHINode(LI.getType(), PN->getName());
5120 InsertNewInstBefore(NewPN, *PN);
5121 std::map<BasicBlock*,Value*> LoadMap; // Don't insert duplicate loads
5123 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
5124 BasicBlock *BB = PN->getIncomingBlock(i);
5125 Value *&TheLoad = LoadMap[BB];
5127 Value *InVal = PN->getIncomingValue(i);
5128 TheLoad = InsertNewInstBefore(new LoadInst(InVal,
5129 InVal->getName()+".val"),
5130 *BB->getTerminator());
5132 NewPN->addIncoming(TheLoad, BB);
5134 return ReplaceInstUsesWith(LI, NewPN);
5141 /// InstCombineStoreToCast - Fold 'store V, (cast P)' -> store (cast V), P'
5143 static Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) {
5144 User *CI = cast<User>(SI.getOperand(1));
5145 Value *CastOp = CI->getOperand(0);
5147 const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
5148 if (const PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) {
5149 const Type *SrcPTy = SrcTy->getElementType();
5151 if (DestPTy->isInteger() || isa<PointerType>(DestPTy)) {
5152 // If the source is an array, the code below will not succeed. Check to
5153 // see if a trivial 'gep P, 0, 0' will help matters. Only do this for
5155 if (const ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy))
5156 if (Constant *CSrc = dyn_cast<Constant>(CastOp))
5157 if (ASrcTy->getNumElements() != 0) {
5158 std::vector<Value*> Idxs(2, Constant::getNullValue(Type::IntTy));
5159 CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs);
5160 SrcTy = cast<PointerType>(CastOp->getType());
5161 SrcPTy = SrcTy->getElementType();
5164 if ((SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
5165 IC.getTargetData().getTypeSize(SrcPTy) ==
5166 IC.getTargetData().getTypeSize(DestPTy)) {
5168 // Okay, we are casting from one integer or pointer type to another of
5169 // the same size. Instead of casting the pointer before the store, cast
5170 // the value to be stored.
5172 if (Constant *C = dyn_cast<Constant>(SI.getOperand(0)))
5173 NewCast = ConstantExpr::getCast(C, SrcPTy);
5175 NewCast = IC.InsertNewInstBefore(new CastInst(SI.getOperand(0),
5177 SI.getOperand(0)->getName()+".c"), SI);
5179 return new StoreInst(NewCast, CastOp);
5186 Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
5187 Value *Val = SI.getOperand(0);
5188 Value *Ptr = SI.getOperand(1);
5190 if (isa<UndefValue>(Ptr)) { // store X, undef -> noop (even if volatile)
5191 removeFromWorkList(&SI);
5192 SI.eraseFromParent();
5197 if (SI.isVolatile()) return 0; // Don't hack volatile loads.
5199 // store X, null -> turns into 'unreachable' in SimplifyCFG
5200 if (isa<ConstantPointerNull>(Ptr)) {
5201 if (!isa<UndefValue>(Val)) {
5202 SI.setOperand(0, UndefValue::get(Val->getType()));
5203 if (Instruction *U = dyn_cast<Instruction>(Val))
5204 WorkList.push_back(U); // Dropped a use.
5207 return 0; // Do not modify these!
5210 // store undef, Ptr -> noop
5211 if (isa<UndefValue>(Val)) {
5212 removeFromWorkList(&SI);
5213 SI.eraseFromParent();
5218 // If the pointer destination is a cast, see if we can fold the cast into the
5220 if (CastInst *CI = dyn_cast<CastInst>(Ptr))
5221 if (Instruction *Res = InstCombineStoreToCast(*this, SI))
5223 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
5224 if (CE->getOpcode() == Instruction::Cast)
5225 if (Instruction *Res = InstCombineStoreToCast(*this, SI))
5229 // If this store is the last instruction in the basic block, and if the block
5230 // ends with an unconditional branch, try to move it to the successor block.
5231 BasicBlock::iterator BBI = &SI; ++BBI;
5232 if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
5233 if (BI->isUnconditional()) {
5234 // Check to see if the successor block has exactly two incoming edges. If
5235 // so, see if the other predecessor contains a store to the same location.
5236 // if so, insert a PHI node (if needed) and move the stores down.
5237 BasicBlock *Dest = BI->getSuccessor(0);
5239 pred_iterator PI = pred_begin(Dest);
5240 BasicBlock *Other = 0;
5241 if (*PI != BI->getParent())
5244 if (PI != pred_end(Dest)) {
5245 if (*PI != BI->getParent())
5250 if (++PI != pred_end(Dest))
5253 if (Other) { // If only one other pred...
5254 BBI = Other->getTerminator();
5255 // Make sure this other block ends in an unconditional branch and that
5256 // there is an instruction before the branch.
5257 if (isa<BranchInst>(BBI) && cast<BranchInst>(BBI)->isUnconditional() &&
5258 BBI != Other->begin()) {
5260 StoreInst *OtherStore = dyn_cast<StoreInst>(BBI);
5262 // If this instruction is a store to the same location.
5263 if (OtherStore && OtherStore->getOperand(1) == SI.getOperand(1)) {
5264 // Okay, we know we can perform this transformation. Insert a PHI
5265 // node now if we need it.
5266 Value *MergedVal = OtherStore->getOperand(0);
5267 if (MergedVal != SI.getOperand(0)) {
5268 PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
5269 PN->reserveOperandSpace(2);
5270 PN->addIncoming(SI.getOperand(0), SI.getParent());
5271 PN->addIncoming(OtherStore->getOperand(0), Other);
5272 MergedVal = InsertNewInstBefore(PN, Dest->front());
5275 // Advance to a place where it is safe to insert the new store and
5277 BBI = Dest->begin();
5278 while (isa<PHINode>(BBI)) ++BBI;
5279 InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
5280 OtherStore->isVolatile()), *BBI);
5282 // Nuke the old stores.
5283 removeFromWorkList(&SI);
5284 removeFromWorkList(OtherStore);
5285 SI.eraseFromParent();
5286 OtherStore->eraseFromParent();
5298 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
5299 // Change br (not X), label True, label False to: br X, label False, True
5301 BasicBlock *TrueDest;
5302 BasicBlock *FalseDest;
5303 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
5304 !isa<Constant>(X)) {
5305 // Swap Destinations and condition...
5307 BI.setSuccessor(0, FalseDest);
5308 BI.setSuccessor(1, TrueDest);
5312 // Cannonicalize setne -> seteq
5313 Instruction::BinaryOps Op; Value *Y;
5314 if (match(&BI, m_Br(m_SetCond(Op, m_Value(X), m_Value(Y)),
5315 TrueDest, FalseDest)))
5316 if ((Op == Instruction::SetNE || Op == Instruction::SetLE ||
5317 Op == Instruction::SetGE) && BI.getCondition()->hasOneUse()) {
5318 SetCondInst *I = cast<SetCondInst>(BI.getCondition());
5319 std::string Name = I->getName(); I->setName("");
5320 Instruction::BinaryOps NewOpcode = SetCondInst::getInverseCondition(Op);
5321 Value *NewSCC = BinaryOperator::create(NewOpcode, X, Y, Name, I);
5322 // Swap Destinations and condition...
5323 BI.setCondition(NewSCC);
5324 BI.setSuccessor(0, FalseDest);
5325 BI.setSuccessor(1, TrueDest);
5326 removeFromWorkList(I);
5327 I->getParent()->getInstList().erase(I);
5328 WorkList.push_back(cast<Instruction>(NewSCC));
5335 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
5336 Value *Cond = SI.getCondition();
5337 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
5338 if (I->getOpcode() == Instruction::Add)
5339 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
5340 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
5341 for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2)
5342 SI.setOperand(i,ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)),
5344 SI.setOperand(0, I->getOperand(0));
5345 WorkList.push_back(I);
5353 void InstCombiner::removeFromWorkList(Instruction *I) {
5354 WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
5359 /// TryToSinkInstruction - Try to move the specified instruction from its
5360 /// current block into the beginning of DestBlock, which can only happen if it's
5361 /// safe to move the instruction past all of the instructions between it and the
5362 /// end of its block.
5363 static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
5364 assert(I->hasOneUse() && "Invariants didn't hold!");
5366 // Cannot move control-flow-involving instructions.
5367 if (isa<PHINode>(I) || isa<InvokeInst>(I) || isa<CallInst>(I)) return false;
5369 // Do not sink alloca instructions out of the entry block.
5370 if (isa<AllocaInst>(I) && I->getParent() == &DestBlock->getParent()->front())
5373 // We can only sink load instructions if there is nothing between the load and
5374 // the end of block that could change the value.
5375 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
5376 if (LI->isVolatile()) return false; // Don't sink volatile loads.
5378 for (BasicBlock::iterator Scan = LI, E = LI->getParent()->end();
5380 if (Scan->mayWriteToMemory())
5384 BasicBlock::iterator InsertPos = DestBlock->begin();
5385 while (isa<PHINode>(InsertPos)) ++InsertPos;
5387 I->moveBefore(InsertPos);
5392 bool InstCombiner::runOnFunction(Function &F) {
5393 bool Changed = false;
5394 TD = &getAnalysis<TargetData>();
5397 // Populate the worklist with the reachable instructions.
5398 std::set<BasicBlock*> Visited;
5399 for (df_ext_iterator<BasicBlock*> BB = df_ext_begin(&F.front(), Visited),
5400 E = df_ext_end(&F.front(), Visited); BB != E; ++BB)
5401 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
5402 WorkList.push_back(I);
5404 // Do a quick scan over the function. If we find any blocks that are
5405 // unreachable, remove any instructions inside of them. This prevents
5406 // the instcombine code from having to deal with some bad special cases.
5407 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
5408 if (!Visited.count(BB)) {
5409 Instruction *Term = BB->getTerminator();
5410 while (Term != BB->begin()) { // Remove instrs bottom-up
5411 BasicBlock::iterator I = Term; --I;
5413 DEBUG(std::cerr << "IC: DCE: " << *I);
5416 if (!I->use_empty())
5417 I->replaceAllUsesWith(UndefValue::get(I->getType()));
5418 I->eraseFromParent();
5423 while (!WorkList.empty()) {
5424 Instruction *I = WorkList.back(); // Get an instruction from the worklist
5425 WorkList.pop_back();
5427 // Check to see if we can DCE or ConstantPropagate the instruction...
5428 // Check to see if we can DIE the instruction...
5429 if (isInstructionTriviallyDead(I)) {
5430 // Add operands to the worklist...
5431 if (I->getNumOperands() < 4)
5432 AddUsesToWorkList(*I);
5435 DEBUG(std::cerr << "IC: DCE: " << *I);
5437 I->eraseFromParent();
5438 removeFromWorkList(I);
5442 // Instruction isn't dead, see if we can constant propagate it...
5443 if (Constant *C = ConstantFoldInstruction(I)) {
5444 Value* Ptr = I->getOperand(0);
5445 if (isa<GetElementPtrInst>(I) &&
5446 cast<Constant>(Ptr)->isNullValue() &&
5447 !isa<ConstantPointerNull>(C) &&
5448 cast<PointerType>(Ptr->getType())->getElementType()->isSized()) {
5449 // If this is a constant expr gep that is effectively computing an
5450 // "offsetof", fold it into 'cast int X to T*' instead of 'gep 0, 0, 12'
5451 bool isFoldableGEP = true;
5452 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
5453 if (!isa<ConstantInt>(I->getOperand(i)))
5454 isFoldableGEP = false;
5455 if (isFoldableGEP) {
5456 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
5457 std::vector<Value*>(I->op_begin()+1, I->op_end()));
5458 C = ConstantUInt::get(Type::ULongTy, Offset);
5459 C = ConstantExpr::getCast(C, TD->getIntPtrType());
5460 C = ConstantExpr::getCast(C, I->getType());
5464 DEBUG(std::cerr << "IC: ConstFold to: " << *C << " from: " << *I);
5466 // Add operands to the worklist...
5467 AddUsesToWorkList(*I);
5468 ReplaceInstUsesWith(*I, C);
5471 I->getParent()->getInstList().erase(I);
5472 removeFromWorkList(I);
5476 // See if we can trivially sink this instruction to a successor basic block.
5477 if (I->hasOneUse()) {
5478 BasicBlock *BB = I->getParent();
5479 BasicBlock *UserParent = cast<Instruction>(I->use_back())->getParent();
5480 if (UserParent != BB) {
5481 bool UserIsSuccessor = false;
5482 // See if the user is one of our successors.
5483 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
5484 if (*SI == UserParent) {
5485 UserIsSuccessor = true;
5489 // If the user is one of our immediate successors, and if that successor
5490 // only has us as a predecessors (we'd have to split the critical edge
5491 // otherwise), we can keep going.
5492 if (UserIsSuccessor && !isa<PHINode>(I->use_back()) &&
5493 next(pred_begin(UserParent)) == pred_end(UserParent))
5494 // Okay, the CFG is simple enough, try to sink this instruction.
5495 Changed |= TryToSinkInstruction(I, UserParent);
5499 // Now that we have an instruction, try combining it to simplify it...
5500 if (Instruction *Result = visit(*I)) {
5502 // Should we replace the old instruction with a new one?
5504 DEBUG(std::cerr << "IC: Old = " << *I
5505 << " New = " << *Result);
5507 // Everything uses the new instruction now.
5508 I->replaceAllUsesWith(Result);
5510 // Push the new instruction and any users onto the worklist.
5511 WorkList.push_back(Result);
5512 AddUsersToWorkList(*Result);
5514 // Move the name to the new instruction first...
5515 std::string OldName = I->getName(); I->setName("");
5516 Result->setName(OldName);
5518 // Insert the new instruction into the basic block...
5519 BasicBlock *InstParent = I->getParent();
5520 BasicBlock::iterator InsertPos = I;
5522 if (!isa<PHINode>(Result)) // If combining a PHI, don't insert
5523 while (isa<PHINode>(InsertPos)) // middle of a block of PHIs.
5526 InstParent->getInstList().insert(InsertPos, Result);
5528 // Make sure that we reprocess all operands now that we reduced their
5530 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
5531 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
5532 WorkList.push_back(OpI);
5534 // Instructions can end up on the worklist more than once. Make sure
5535 // we do not process an instruction that has been deleted.
5536 removeFromWorkList(I);
5538 // Erase the old instruction.
5539 InstParent->getInstList().erase(I);
5541 DEBUG(std::cerr << "IC: MOD = " << *I);
5543 // If the instruction was modified, it's possible that it is now dead.
5544 // if so, remove it.
5545 if (isInstructionTriviallyDead(I)) {
5546 // Make sure we process all operands now that we are reducing their
5548 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
5549 if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(i)))
5550 WorkList.push_back(OpI);
5552 // Instructions may end up in the worklist more than once. Erase all
5553 // occurrances of this instruction.
5554 removeFromWorkList(I);
5555 I->eraseFromParent();
5557 WorkList.push_back(Result);
5558 AddUsersToWorkList(*Result);
5568 FunctionPass *llvm::createInstructionCombiningPass() {
5569 return new InstCombiner();