1 //===- InstructionCombining.cpp - Combine multiple instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // 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
12 // algebraic 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. Compare instructions are converted from <,>,<=,>= to ==,!= if possible
28 // 4. All cmp 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 #include "llvm/Transforms/Scalar.h"
37 #include "InstCombine.h"
38 #include "llvm-c/Initialization.h"
39 #include "llvm/ADT/SmallPtrSet.h"
40 #include "llvm/ADT/Statistic.h"
41 #include "llvm/ADT/StringSwitch.h"
42 #include "llvm/Analysis/AssumptionCache.h"
43 #include "llvm/Analysis/CFG.h"
44 #include "llvm/Analysis/ConstantFolding.h"
45 #include "llvm/Analysis/InstructionSimplify.h"
46 #include "llvm/Analysis/LoopInfo.h"
47 #include "llvm/Analysis/MemoryBuiltins.h"
48 #include "llvm/Analysis/ValueTracking.h"
49 #include "llvm/IR/CFG.h"
50 #include "llvm/IR/DataLayout.h"
51 #include "llvm/IR/Dominators.h"
52 #include "llvm/IR/GetElementPtrTypeIterator.h"
53 #include "llvm/IR/IntrinsicInst.h"
54 #include "llvm/IR/PatternMatch.h"
55 #include "llvm/IR/ValueHandle.h"
56 #include "llvm/Support/CommandLine.h"
57 #include "llvm/Support/Debug.h"
58 #include "llvm/Analysis/TargetLibraryInfo.h"
59 #include "llvm/Transforms/Utils/Local.h"
63 using namespace llvm::PatternMatch;
65 #define DEBUG_TYPE "instcombine"
67 STATISTIC(NumCombined , "Number of insts combined");
68 STATISTIC(NumConstProp, "Number of constant folds");
69 STATISTIC(NumDeadInst , "Number of dead inst eliminated");
70 STATISTIC(NumSunkInst , "Number of instructions sunk");
71 STATISTIC(NumExpand, "Number of expansions");
72 STATISTIC(NumFactor , "Number of factorizations");
73 STATISTIC(NumReassoc , "Number of reassociations");
75 // Initialization Routines
76 void llvm::initializeInstCombine(PassRegistry &Registry) {
77 initializeInstCombinerPass(Registry);
80 void LLVMInitializeInstCombine(LLVMPassRegistryRef R) {
81 initializeInstCombine(*unwrap(R));
84 char InstCombiner::ID = 0;
85 INITIALIZE_PASS_BEGIN(InstCombiner, "instcombine",
86 "Combine redundant instructions", false, false)
87 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
88 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
89 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
90 INITIALIZE_PASS_END(InstCombiner, "instcombine",
91 "Combine redundant instructions", false, false)
93 void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
95 AU.addRequired<AssumptionCacheTracker>();
96 AU.addRequired<TargetLibraryInfoWrapperPass>();
97 AU.addRequired<DominatorTreeWrapperPass>();
98 AU.addPreserved<DominatorTreeWrapperPass>();
102 Value *InstCombiner::EmitGEPOffset(User *GEP) {
103 return llvm::EmitGEPOffset(Builder, *getDataLayout(), GEP);
106 /// ShouldChangeType - Return true if it is desirable to convert a computation
107 /// from 'From' to 'To'. We don't want to convert from a legal to an illegal
108 /// type for example, or from a smaller to a larger illegal type.
109 bool InstCombiner::ShouldChangeType(Type *From, Type *To) const {
110 assert(From->isIntegerTy() && To->isIntegerTy());
112 // If we don't have DL, we don't know if the source/dest are legal.
113 if (!DL) return false;
115 unsigned FromWidth = From->getPrimitiveSizeInBits();
116 unsigned ToWidth = To->getPrimitiveSizeInBits();
117 bool FromLegal = DL->isLegalInteger(FromWidth);
118 bool ToLegal = DL->isLegalInteger(ToWidth);
120 // If this is a legal integer from type, and the result would be an illegal
121 // type, don't do the transformation.
122 if (FromLegal && !ToLegal)
125 // Otherwise, if both are illegal, do not increase the size of the result. We
126 // do allow things like i160 -> i64, but not i64 -> i160.
127 if (!FromLegal && !ToLegal && ToWidth > FromWidth)
133 // Return true, if No Signed Wrap should be maintained for I.
134 // The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C",
135 // where both B and C should be ConstantInts, results in a constant that does
136 // not overflow. This function only handles the Add and Sub opcodes. For
137 // all other opcodes, the function conservatively returns false.
138 static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) {
139 OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
140 if (!OBO || !OBO->hasNoSignedWrap()) {
144 // We reason about Add and Sub Only.
145 Instruction::BinaryOps Opcode = I.getOpcode();
146 if (Opcode != Instruction::Add &&
147 Opcode != Instruction::Sub) {
151 ConstantInt *CB = dyn_cast<ConstantInt>(B);
152 ConstantInt *CC = dyn_cast<ConstantInt>(C);
158 const APInt &BVal = CB->getValue();
159 const APInt &CVal = CC->getValue();
160 bool Overflow = false;
162 if (Opcode == Instruction::Add) {
163 BVal.sadd_ov(CVal, Overflow);
165 BVal.ssub_ov(CVal, Overflow);
171 /// Conservatively clears subclassOptionalData after a reassociation or
172 /// commutation. We preserve fast-math flags when applicable as they can be
174 static void ClearSubclassDataAfterReassociation(BinaryOperator &I) {
175 FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I);
177 I.clearSubclassOptionalData();
181 FastMathFlags FMF = I.getFastMathFlags();
182 I.clearSubclassOptionalData();
183 I.setFastMathFlags(FMF);
186 /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
187 /// operators which are associative or commutative:
189 // Commutative operators:
191 // 1. Order operands such that they are listed from right (least complex) to
192 // left (most complex). This puts constants before unary operators before
195 // Associative operators:
197 // 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
198 // 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
200 // Associative and commutative operators:
202 // 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
203 // 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
204 // 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
205 // if C1 and C2 are constants.
207 bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
208 Instruction::BinaryOps Opcode = I.getOpcode();
209 bool Changed = false;
212 // Order operands such that they are listed from right (least complex) to
213 // left (most complex). This puts constants before unary operators before
215 if (I.isCommutative() && getComplexity(I.getOperand(0)) <
216 getComplexity(I.getOperand(1)))
217 Changed = !I.swapOperands();
219 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0));
220 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1));
222 if (I.isAssociative()) {
223 // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
224 if (Op0 && Op0->getOpcode() == Opcode) {
225 Value *A = Op0->getOperand(0);
226 Value *B = Op0->getOperand(1);
227 Value *C = I.getOperand(1);
229 // Does "B op C" simplify?
230 if (Value *V = SimplifyBinOp(Opcode, B, C, DL)) {
231 // It simplifies to V. Form "A op V".
234 // Conservatively clear the optional flags, since they may not be
235 // preserved by the reassociation.
236 if (MaintainNoSignedWrap(I, B, C) &&
237 (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) {
238 // Note: this is only valid because SimplifyBinOp doesn't look at
239 // the operands to Op0.
240 I.clearSubclassOptionalData();
241 I.setHasNoSignedWrap(true);
243 ClearSubclassDataAfterReassociation(I);
252 // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
253 if (Op1 && Op1->getOpcode() == Opcode) {
254 Value *A = I.getOperand(0);
255 Value *B = Op1->getOperand(0);
256 Value *C = Op1->getOperand(1);
258 // Does "A op B" simplify?
259 if (Value *V = SimplifyBinOp(Opcode, A, B, DL)) {
260 // It simplifies to V. Form "V op C".
263 // Conservatively clear the optional flags, since they may not be
264 // preserved by the reassociation.
265 ClearSubclassDataAfterReassociation(I);
273 if (I.isAssociative() && I.isCommutative()) {
274 // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
275 if (Op0 && Op0->getOpcode() == Opcode) {
276 Value *A = Op0->getOperand(0);
277 Value *B = Op0->getOperand(1);
278 Value *C = I.getOperand(1);
280 // Does "C op A" simplify?
281 if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) {
282 // It simplifies to V. Form "V op B".
285 // Conservatively clear the optional flags, since they may not be
286 // preserved by the reassociation.
287 ClearSubclassDataAfterReassociation(I);
294 // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
295 if (Op1 && Op1->getOpcode() == Opcode) {
296 Value *A = I.getOperand(0);
297 Value *B = Op1->getOperand(0);
298 Value *C = Op1->getOperand(1);
300 // Does "C op A" simplify?
301 if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) {
302 // It simplifies to V. Form "B op V".
305 // Conservatively clear the optional flags, since they may not be
306 // preserved by the reassociation.
307 ClearSubclassDataAfterReassociation(I);
314 // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
315 // if C1 and C2 are constants.
317 Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode &&
318 isa<Constant>(Op0->getOperand(1)) &&
319 isa<Constant>(Op1->getOperand(1)) &&
320 Op0->hasOneUse() && Op1->hasOneUse()) {
321 Value *A = Op0->getOperand(0);
322 Constant *C1 = cast<Constant>(Op0->getOperand(1));
323 Value *B = Op1->getOperand(0);
324 Constant *C2 = cast<Constant>(Op1->getOperand(1));
326 Constant *Folded = ConstantExpr::get(Opcode, C1, C2);
327 BinaryOperator *New = BinaryOperator::Create(Opcode, A, B);
328 if (isa<FPMathOperator>(New)) {
329 FastMathFlags Flags = I.getFastMathFlags();
330 Flags &= Op0->getFastMathFlags();
331 Flags &= Op1->getFastMathFlags();
332 New->setFastMathFlags(Flags);
334 InsertNewInstWith(New, I);
336 I.setOperand(0, New);
337 I.setOperand(1, Folded);
338 // Conservatively clear the optional flags, since they may not be
339 // preserved by the reassociation.
340 ClearSubclassDataAfterReassociation(I);
347 // No further simplifications.
352 /// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to
353 /// "(X LOp Y) ROp (X LOp Z)".
354 static bool LeftDistributesOverRight(Instruction::BinaryOps LOp,
355 Instruction::BinaryOps ROp) {
360 case Instruction::And:
361 // And distributes over Or and Xor.
365 case Instruction::Or:
366 case Instruction::Xor:
370 case Instruction::Mul:
371 // Multiplication distributes over addition and subtraction.
375 case Instruction::Add:
376 case Instruction::Sub:
380 case Instruction::Or:
381 // Or distributes over And.
385 case Instruction::And:
391 /// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to
392 /// "(X ROp Z) LOp (Y ROp Z)".
393 static bool RightDistributesOverLeft(Instruction::BinaryOps LOp,
394 Instruction::BinaryOps ROp) {
395 if (Instruction::isCommutative(ROp))
396 return LeftDistributesOverRight(ROp, LOp);
401 // (X >> Z) & (Y >> Z) -> (X&Y) >> Z for all shifts.
402 // (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts.
403 // (X >> Z) ^ (Y >> Z) -> (X^Y) >> Z for all shifts.
404 case Instruction::And:
405 case Instruction::Or:
406 case Instruction::Xor:
410 case Instruction::Shl:
411 case Instruction::LShr:
412 case Instruction::AShr:
416 // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z",
417 // but this requires knowing that the addition does not overflow and other
422 /// This function returns identity value for given opcode, which can be used to
423 /// factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1).
424 static Value *getIdentityValue(Instruction::BinaryOps OpCode, Value *V) {
425 if (isa<Constant>(V))
428 if (OpCode == Instruction::Mul)
429 return ConstantInt::get(V->getType(), 1);
431 // TODO: We can handle other cases e.g. Instruction::And, Instruction::Or etc.
436 /// This function factors binary ops which can be combined using distributive
437 /// laws. This function tries to transform 'Op' based TopLevelOpcode to enable
438 /// factorization e.g for ADD(SHL(X , 2), MUL(X, 5)), When this function called
439 /// with TopLevelOpcode == Instruction::Add and Op = SHL(X, 2), transforms
440 /// SHL(X, 2) to MUL(X, 4) i.e. returns Instruction::Mul with LHS set to 'X' and
442 static Instruction::BinaryOps
443 getBinOpsForFactorization(Instruction::BinaryOps TopLevelOpcode,
444 BinaryOperator *Op, Value *&LHS, Value *&RHS) {
446 return Instruction::BinaryOpsEnd;
448 LHS = Op->getOperand(0);
449 RHS = Op->getOperand(1);
451 switch (TopLevelOpcode) {
453 return Op->getOpcode();
455 case Instruction::Add:
456 case Instruction::Sub:
457 if (Op->getOpcode() == Instruction::Shl) {
458 if (Constant *CST = dyn_cast<Constant>(Op->getOperand(1))) {
459 // The multiplier is really 1 << CST.
460 RHS = ConstantExpr::getShl(ConstantInt::get(Op->getType(), 1), CST);
461 return Instruction::Mul;
464 return Op->getOpcode();
467 // TODO: We can add other conversions e.g. shr => div etc.
470 /// This tries to simplify binary operations by factorizing out common terms
471 /// (e. g. "(A*B)+(A*C)" -> "A*(B+C)").
472 static Value *tryFactorization(InstCombiner::BuilderTy *Builder,
473 const DataLayout *DL, BinaryOperator &I,
474 Instruction::BinaryOps InnerOpcode, Value *A,
475 Value *B, Value *C, Value *D) {
477 // If any of A, B, C, D are null, we can not factor I, return early.
478 // Checking A and C should be enough.
479 if (!A || !C || !B || !D)
482 Value *SimplifiedInst = nullptr;
483 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
484 Instruction::BinaryOps TopLevelOpcode = I.getOpcode();
486 // Does "X op' Y" always equal "Y op' X"?
487 bool InnerCommutative = Instruction::isCommutative(InnerOpcode);
489 // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"?
490 if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode))
491 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the
492 // commutative case, "(A op' B) op (C op' A)"?
493 if (A == C || (InnerCommutative && A == D)) {
496 // Consider forming "A op' (B op D)".
497 // If "B op D" simplifies then it can be formed with no cost.
498 Value *V = SimplifyBinOp(TopLevelOpcode, B, D, DL);
499 // If "B op D" doesn't simplify then only go on if both of the existing
500 // operations "A op' B" and "C op' D" will be zapped as no longer used.
501 if (!V && LHS->hasOneUse() && RHS->hasOneUse())
502 V = Builder->CreateBinOp(TopLevelOpcode, B, D, RHS->getName());
504 SimplifiedInst = Builder->CreateBinOp(InnerOpcode, A, V);
508 // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"?
509 if (!SimplifiedInst && RightDistributesOverLeft(TopLevelOpcode, InnerOpcode))
510 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the
511 // commutative case, "(A op' B) op (B op' D)"?
512 if (B == D || (InnerCommutative && B == C)) {
515 // Consider forming "(A op C) op' B".
516 // If "A op C" simplifies then it can be formed with no cost.
517 Value *V = SimplifyBinOp(TopLevelOpcode, A, C, DL);
519 // If "A op C" doesn't simplify then only go on if both of the existing
520 // operations "A op' B" and "C op' D" will be zapped as no longer used.
521 if (!V && LHS->hasOneUse() && RHS->hasOneUse())
522 V = Builder->CreateBinOp(TopLevelOpcode, A, C, LHS->getName());
524 SimplifiedInst = Builder->CreateBinOp(InnerOpcode, V, B);
528 if (SimplifiedInst) {
530 SimplifiedInst->takeName(&I);
532 // Check if we can add NSW flag to SimplifiedInst. If so, set NSW flag.
533 // TODO: Check for NUW.
534 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(SimplifiedInst)) {
535 if (isa<OverflowingBinaryOperator>(SimplifiedInst)) {
537 if (isa<OverflowingBinaryOperator>(&I))
538 HasNSW = I.hasNoSignedWrap();
540 if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS))
541 if (isa<OverflowingBinaryOperator>(Op0))
542 HasNSW &= Op0->hasNoSignedWrap();
544 if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS))
545 if (isa<OverflowingBinaryOperator>(Op1))
546 HasNSW &= Op1->hasNoSignedWrap();
547 BO->setHasNoSignedWrap(HasNSW);
551 return SimplifiedInst;
554 /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
555 /// which some other binary operation distributes over either by factorizing
556 /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
557 /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
558 /// a win). Returns the simplified value, or null if it didn't simplify.
559 Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) {
560 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
561 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
562 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
565 Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
566 auto TopLevelOpcode = I.getOpcode();
567 auto LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B);
568 auto RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D);
570 // The instruction has the form "(A op' B) op (C op' D)". Try to factorize
572 if (LHSOpcode == RHSOpcode) {
573 if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, C, D))
577 // The instruction has the form "(A op' B) op (C)". Try to factorize common
579 if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, RHS,
580 getIdentityValue(LHSOpcode, RHS)))
583 // The instruction has the form "(B) op (C op' D)". Try to factorize common
585 if (Value *V = tryFactorization(Builder, DL, I, RHSOpcode, LHS,
586 getIdentityValue(RHSOpcode, LHS), C, D))
590 if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) {
591 // The instruction has the form "(A op' B) op C". See if expanding it out
592 // to "(A op C) op' (B op C)" results in simplifications.
593 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
594 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op'
596 // Do "A op C" and "B op C" both simplify?
597 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, DL))
598 if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, DL)) {
599 // They do! Return "L op' R".
601 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
602 if ((L == A && R == B) ||
603 (Instruction::isCommutative(InnerOpcode) && L == B && R == A))
605 // Otherwise return "L op' R" if it simplifies.
606 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL))
608 // Otherwise, create a new instruction.
609 C = Builder->CreateBinOp(InnerOpcode, L, R);
615 if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) {
616 // The instruction has the form "A op (B op' C)". See if expanding it out
617 // to "(A op B) op' (A op C)" results in simplifications.
618 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
619 Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op'
621 // Do "A op B" and "A op C" both simplify?
622 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, DL))
623 if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, DL)) {
624 // They do! Return "L op' R".
626 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
627 if ((L == B && R == C) ||
628 (Instruction::isCommutative(InnerOpcode) && L == C && R == B))
630 // Otherwise return "L op' R" if it simplifies.
631 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL))
633 // Otherwise, create a new instruction.
634 A = Builder->CreateBinOp(InnerOpcode, L, R);
643 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
644 // if the LHS is a constant zero (which is the 'negate' form).
646 Value *InstCombiner::dyn_castNegVal(Value *V) const {
647 if (BinaryOperator::isNeg(V))
648 return BinaryOperator::getNegArgument(V);
650 // Constants can be considered to be negated values if they can be folded.
651 if (ConstantInt *C = dyn_cast<ConstantInt>(V))
652 return ConstantExpr::getNeg(C);
654 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V))
655 if (C->getType()->getElementType()->isIntegerTy())
656 return ConstantExpr::getNeg(C);
661 // dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the
662 // instruction if the LHS is a constant negative zero (which is the 'negate'
665 Value *InstCombiner::dyn_castFNegVal(Value *V, bool IgnoreZeroSign) const {
666 if (BinaryOperator::isFNeg(V, IgnoreZeroSign))
667 return BinaryOperator::getFNegArgument(V);
669 // Constants can be considered to be negated values if they can be folded.
670 if (ConstantFP *C = dyn_cast<ConstantFP>(V))
671 return ConstantExpr::getFNeg(C);
673 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V))
674 if (C->getType()->getElementType()->isFloatingPointTy())
675 return ConstantExpr::getFNeg(C);
680 static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
682 if (CastInst *CI = dyn_cast<CastInst>(&I)) {
683 return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType());
686 // Figure out if the constant is the left or the right argument.
687 bool ConstIsRHS = isa<Constant>(I.getOperand(1));
688 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
690 if (Constant *SOC = dyn_cast<Constant>(SO)) {
692 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
693 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
696 Value *Op0 = SO, *Op1 = ConstOperand;
700 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) {
701 Value *RI = IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1,
702 SO->getName()+".op");
703 Instruction *FPInst = dyn_cast<Instruction>(RI);
704 if (FPInst && isa<FPMathOperator>(FPInst))
705 FPInst->copyFastMathFlags(BO);
708 if (ICmpInst *CI = dyn_cast<ICmpInst>(&I))
709 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
710 SO->getName()+".cmp");
711 if (FCmpInst *CI = dyn_cast<FCmpInst>(&I))
712 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
713 SO->getName()+".cmp");
714 llvm_unreachable("Unknown binary instruction type!");
717 // FoldOpIntoSelect - Given an instruction with a select as one operand and a
718 // constant as the other operand, try to fold the binary operator into the
719 // select arguments. This also works for Cast instructions, which obviously do
720 // not have a second operand.
721 Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) {
722 // Don't modify shared select instructions
723 if (!SI->hasOneUse()) return nullptr;
724 Value *TV = SI->getOperand(1);
725 Value *FV = SI->getOperand(2);
727 if (isa<Constant>(TV) || isa<Constant>(FV)) {
728 // Bool selects with constant operands can be folded to logical ops.
729 if (SI->getType()->isIntegerTy(1)) return nullptr;
731 // If it's a bitcast involving vectors, make sure it has the same number of
732 // elements on both sides.
733 if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) {
734 VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy());
735 VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy());
737 // Verify that either both or neither are vectors.
738 if ((SrcTy == nullptr) != (DestTy == nullptr)) return nullptr;
739 // If vectors, verify that they have the same number of elements.
740 if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements())
744 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this);
745 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this);
747 return SelectInst::Create(SI->getCondition(),
748 SelectTrueVal, SelectFalseVal);
754 /// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
755 /// has a PHI node as operand #0, see if we can fold the instruction into the
756 /// PHI (which is only possible if all operands to the PHI are constants).
758 Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
759 PHINode *PN = cast<PHINode>(I.getOperand(0));
760 unsigned NumPHIValues = PN->getNumIncomingValues();
761 if (NumPHIValues == 0)
764 // We normally only transform phis with a single use. However, if a PHI has
765 // multiple uses and they are all the same operation, we can fold *all* of the
766 // uses into the PHI.
767 if (!PN->hasOneUse()) {
768 // Walk the use list for the instruction, comparing them to I.
769 for (User *U : PN->users()) {
770 Instruction *UI = cast<Instruction>(U);
771 if (UI != &I && !I.isIdenticalTo(UI))
774 // Otherwise, we can replace *all* users with the new PHI we form.
777 // Check to see if all of the operands of the PHI are simple constants
778 // (constantint/constantfp/undef). If there is one non-constant value,
779 // remember the BB it is in. If there is more than one or if *it* is a PHI,
780 // bail out. We don't do arbitrary constant expressions here because moving
781 // their computation can be expensive without a cost model.
782 BasicBlock *NonConstBB = nullptr;
783 for (unsigned i = 0; i != NumPHIValues; ++i) {
784 Value *InVal = PN->getIncomingValue(i);
785 if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal))
788 if (isa<PHINode>(InVal)) return nullptr; // Itself a phi.
789 if (NonConstBB) return nullptr; // More than one non-const value.
791 NonConstBB = PN->getIncomingBlock(i);
793 // If the InVal is an invoke at the end of the pred block, then we can't
794 // insert a computation after it without breaking the edge.
795 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
796 if (II->getParent() == NonConstBB)
799 // If the incoming non-constant value is in I's block, we will remove one
800 // instruction, but insert another equivalent one, leading to infinite
802 if (isPotentiallyReachable(I.getParent(), NonConstBB, DT, LI))
806 // If there is exactly one non-constant value, we can insert a copy of the
807 // operation in that block. However, if this is a critical edge, we would be
808 // inserting the computation on some other paths (e.g. inside a loop). Only
809 // do this if the pred block is unconditionally branching into the phi block.
810 if (NonConstBB != nullptr) {
811 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
812 if (!BI || !BI->isUnconditional()) return nullptr;
815 // Okay, we can do the transformation: create the new PHI node.
816 PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues());
817 InsertNewInstBefore(NewPN, *PN);
820 // If we are going to have to insert a new computation, do so right before the
821 // predecessors terminator.
823 Builder->SetInsertPoint(NonConstBB->getTerminator());
825 // Next, add all of the operands to the PHI.
826 if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
827 // We only currently try to fold the condition of a select when it is a phi,
828 // not the true/false values.
829 Value *TrueV = SI->getTrueValue();
830 Value *FalseV = SI->getFalseValue();
831 BasicBlock *PhiTransBB = PN->getParent();
832 for (unsigned i = 0; i != NumPHIValues; ++i) {
833 BasicBlock *ThisBB = PN->getIncomingBlock(i);
834 Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB);
835 Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB);
836 Value *InV = nullptr;
837 // Beware of ConstantExpr: it may eventually evaluate to getNullValue,
838 // even if currently isNullValue gives false.
839 Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i));
840 if (InC && !isa<ConstantExpr>(InC))
841 InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
843 InV = Builder->CreateSelect(PN->getIncomingValue(i),
844 TrueVInPred, FalseVInPred, "phitmp");
845 NewPN->addIncoming(InV, ThisBB);
847 } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) {
848 Constant *C = cast<Constant>(I.getOperand(1));
849 for (unsigned i = 0; i != NumPHIValues; ++i) {
850 Value *InV = nullptr;
851 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
852 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C);
853 else if (isa<ICmpInst>(CI))
854 InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i),
857 InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i),
859 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
861 } else if (I.getNumOperands() == 2) {
862 Constant *C = cast<Constant>(I.getOperand(1));
863 for (unsigned i = 0; i != NumPHIValues; ++i) {
864 Value *InV = nullptr;
865 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
866 InV = ConstantExpr::get(I.getOpcode(), InC, C);
868 InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(),
869 PN->getIncomingValue(i), C, "phitmp");
870 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
873 CastInst *CI = cast<CastInst>(&I);
874 Type *RetTy = CI->getType();
875 for (unsigned i = 0; i != NumPHIValues; ++i) {
877 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
878 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy);
880 InV = Builder->CreateCast(CI->getOpcode(),
881 PN->getIncomingValue(i), I.getType(), "phitmp");
882 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
886 for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) {
887 Instruction *User = cast<Instruction>(*UI++);
888 if (User == &I) continue;
889 ReplaceInstUsesWith(*User, NewPN);
890 EraseInstFromFunction(*User);
892 return ReplaceInstUsesWith(I, NewPN);
895 /// FindElementAtOffset - Given a pointer type and a constant offset, determine
896 /// whether or not there is a sequence of GEP indices into the pointed type that
897 /// will land us at the specified offset. If so, fill them into NewIndices and
898 /// return the resultant element type, otherwise return null.
899 Type *InstCombiner::FindElementAtOffset(Type *PtrTy, int64_t Offset,
900 SmallVectorImpl<Value*> &NewIndices) {
901 assert(PtrTy->isPtrOrPtrVectorTy());
906 Type *Ty = PtrTy->getPointerElementType();
910 // Start with the index over the outer type. Note that the type size
911 // might be zero (even if the offset isn't zero) if the indexed type
912 // is something like [0 x {int, int}]
913 Type *IntPtrTy = DL->getIntPtrType(PtrTy);
914 int64_t FirstIdx = 0;
915 if (int64_t TySize = DL->getTypeAllocSize(Ty)) {
916 FirstIdx = Offset/TySize;
917 Offset -= FirstIdx*TySize;
919 // Handle hosts where % returns negative instead of values [0..TySize).
925 assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
928 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
930 // Index into the types. If we fail, set OrigBase to null.
932 // Indexing into tail padding between struct/array elements.
933 if (uint64_t(Offset*8) >= DL->getTypeSizeInBits(Ty))
936 if (StructType *STy = dyn_cast<StructType>(Ty)) {
937 const StructLayout *SL = DL->getStructLayout(STy);
938 assert(Offset < (int64_t)SL->getSizeInBytes() &&
939 "Offset must stay within the indexed type");
941 unsigned Elt = SL->getElementContainingOffset(Offset);
942 NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
945 Offset -= SL->getElementOffset(Elt);
946 Ty = STy->getElementType(Elt);
947 } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
948 uint64_t EltSize = DL->getTypeAllocSize(AT->getElementType());
949 assert(EltSize && "Cannot index into a zero-sized array");
950 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
952 Ty = AT->getElementType();
954 // Otherwise, we can't index into the middle of this atomic type, bail.
962 static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) {
963 // If this GEP has only 0 indices, it is the same pointer as
964 // Src. If Src is not a trivial GEP too, don't combine
966 if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() &&
972 /// Descale - Return a value X such that Val = X * Scale, or null if none. If
973 /// the multiplication is known not to overflow then NoSignedWrap is set.
974 Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) {
975 assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!");
976 assert(cast<IntegerType>(Val->getType())->getBitWidth() ==
977 Scale.getBitWidth() && "Scale not compatible with value!");
979 // If Val is zero or Scale is one then Val = Val * Scale.
980 if (match(Val, m_Zero()) || Scale == 1) {
985 // If Scale is zero then it does not divide Val.
986 if (Scale.isMinValue())
989 // Look through chains of multiplications, searching for a constant that is
990 // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4
991 // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by
992 // a factor of 4 will produce X*(Y*2). The principle of operation is to bore
995 // Val = M1 * X || Analysis starts here and works down
996 // M1 = M2 * Y || Doesn't descend into terms with more
997 // M2 = Z * 4 \/ than one use
999 // Then to modify a term at the bottom:
1002 // M1 = Z * Y || Replaced M2 with Z
1004 // Then to work back up correcting nsw flags.
1006 // Op - the term we are currently analyzing. Starts at Val then drills down.
1007 // Replaced with its descaled value before exiting from the drill down loop.
1010 // Parent - initially null, but after drilling down notes where Op came from.
1011 // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the
1012 // 0'th operand of Val.
1013 std::pair<Instruction*, unsigned> Parent;
1015 // RequireNoSignedWrap - Set if the transform requires a descaling at deeper
1016 // levels that doesn't overflow.
1017 bool RequireNoSignedWrap = false;
1019 // logScale - log base 2 of the scale. Negative if not a power of 2.
1020 int32_t logScale = Scale.exactLogBase2();
1022 for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down
1024 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
1025 // If Op is a constant divisible by Scale then descale to the quotient.
1026 APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth.
1027 APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder);
1028 if (!Remainder.isMinValue())
1029 // Not divisible by Scale.
1031 // Replace with the quotient in the parent.
1032 Op = ConstantInt::get(CI->getType(), Quotient);
1033 NoSignedWrap = true;
1037 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) {
1039 if (BO->getOpcode() == Instruction::Mul) {
1041 NoSignedWrap = BO->hasNoSignedWrap();
1042 if (RequireNoSignedWrap && !NoSignedWrap)
1045 // There are three cases for multiplication: multiplication by exactly
1046 // the scale, multiplication by a constant different to the scale, and
1047 // multiplication by something else.
1048 Value *LHS = BO->getOperand(0);
1049 Value *RHS = BO->getOperand(1);
1051 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
1052 // Multiplication by a constant.
1053 if (CI->getValue() == Scale) {
1054 // Multiplication by exactly the scale, replace the multiplication
1055 // by its left-hand side in the parent.
1060 // Otherwise drill down into the constant.
1061 if (!Op->hasOneUse())
1064 Parent = std::make_pair(BO, 1);
1068 // Multiplication by something else. Drill down into the left-hand side
1069 // since that's where the reassociate pass puts the good stuff.
1070 if (!Op->hasOneUse())
1073 Parent = std::make_pair(BO, 0);
1077 if (logScale > 0 && BO->getOpcode() == Instruction::Shl &&
1078 isa<ConstantInt>(BO->getOperand(1))) {
1079 // Multiplication by a power of 2.
1080 NoSignedWrap = BO->hasNoSignedWrap();
1081 if (RequireNoSignedWrap && !NoSignedWrap)
1084 Value *LHS = BO->getOperand(0);
1085 int32_t Amt = cast<ConstantInt>(BO->getOperand(1))->
1086 getLimitedValue(Scale.getBitWidth());
1089 if (Amt == logScale) {
1090 // Multiplication by exactly the scale, replace the multiplication
1091 // by its left-hand side in the parent.
1095 if (Amt < logScale || !Op->hasOneUse())
1098 // Multiplication by more than the scale. Reduce the multiplying amount
1099 // by the scale in the parent.
1100 Parent = std::make_pair(BO, 1);
1101 Op = ConstantInt::get(BO->getType(), Amt - logScale);
1106 if (!Op->hasOneUse())
1109 if (CastInst *Cast = dyn_cast<CastInst>(Op)) {
1110 if (Cast->getOpcode() == Instruction::SExt) {
1111 // Op is sign-extended from a smaller type, descale in the smaller type.
1112 unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
1113 APInt SmallScale = Scale.trunc(SmallSize);
1114 // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to
1115 // descale Op as (sext Y) * Scale. In order to have
1116 // sext (Y * SmallScale) = (sext Y) * Scale
1117 // some conditions need to hold however: SmallScale must sign-extend to
1118 // Scale and the multiplication Y * SmallScale should not overflow.
1119 if (SmallScale.sext(Scale.getBitWidth()) != Scale)
1120 // SmallScale does not sign-extend to Scale.
1122 assert(SmallScale.exactLogBase2() == logScale);
1123 // Require that Y * SmallScale must not overflow.
1124 RequireNoSignedWrap = true;
1126 // Drill down through the cast.
1127 Parent = std::make_pair(Cast, 0);
1132 if (Cast->getOpcode() == Instruction::Trunc) {
1133 // Op is truncated from a larger type, descale in the larger type.
1134 // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then
1135 // trunc (Y * sext Scale) = (trunc Y) * Scale
1136 // always holds. However (trunc Y) * Scale may overflow even if
1137 // trunc (Y * sext Scale) does not, so nsw flags need to be cleared
1138 // from this point up in the expression (see later).
1139 if (RequireNoSignedWrap)
1142 // Drill down through the cast.
1143 unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
1144 Parent = std::make_pair(Cast, 0);
1145 Scale = Scale.sext(LargeSize);
1146 if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits())
1148 assert(Scale.exactLogBase2() == logScale);
1153 // Unsupported expression, bail out.
1157 // If Op is zero then Val = Op * Scale.
1158 if (match(Op, m_Zero())) {
1159 NoSignedWrap = true;
1163 // We know that we can successfully descale, so from here on we can safely
1164 // modify the IR. Op holds the descaled version of the deepest term in the
1165 // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known
1169 // The expression only had one term.
1172 // Rewrite the parent using the descaled version of its operand.
1173 assert(Parent.first->hasOneUse() && "Drilled down when more than one use!");
1174 assert(Op != Parent.first->getOperand(Parent.second) &&
1175 "Descaling was a no-op?");
1176 Parent.first->setOperand(Parent.second, Op);
1177 Worklist.Add(Parent.first);
1179 // Now work back up the expression correcting nsw flags. The logic is based
1180 // on the following observation: if X * Y is known not to overflow as a signed
1181 // multiplication, and Y is replaced by a value Z with smaller absolute value,
1182 // then X * Z will not overflow as a signed multiplication either. As we work
1183 // our way up, having NoSignedWrap 'true' means that the descaled value at the
1184 // current level has strictly smaller absolute value than the original.
1185 Instruction *Ancestor = Parent.first;
1187 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) {
1188 // If the multiplication wasn't nsw then we can't say anything about the
1189 // value of the descaled multiplication, and we have to clear nsw flags
1190 // from this point on up.
1191 bool OpNoSignedWrap = BO->hasNoSignedWrap();
1192 NoSignedWrap &= OpNoSignedWrap;
1193 if (NoSignedWrap != OpNoSignedWrap) {
1194 BO->setHasNoSignedWrap(NoSignedWrap);
1195 Worklist.Add(Ancestor);
1197 } else if (Ancestor->getOpcode() == Instruction::Trunc) {
1198 // The fact that the descaled input to the trunc has smaller absolute
1199 // value than the original input doesn't tell us anything useful about
1200 // the absolute values of the truncations.
1201 NoSignedWrap = false;
1203 assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) &&
1204 "Failed to keep proper track of nsw flags while drilling down?");
1206 if (Ancestor == Val)
1207 // Got to the top, all done!
1210 // Move up one level in the expression.
1211 assert(Ancestor->hasOneUse() && "Drilled down when more than one use!");
1212 Ancestor = Ancestor->user_back();
1216 /// \brief Creates node of binary operation with the same attributes as the
1217 /// specified one but with other operands.
1218 static Value *CreateBinOpAsGiven(BinaryOperator &Inst, Value *LHS, Value *RHS,
1219 InstCombiner::BuilderTy *B) {
1220 Value *BORes = B->CreateBinOp(Inst.getOpcode(), LHS, RHS);
1221 if (BinaryOperator *NewBO = dyn_cast<BinaryOperator>(BORes)) {
1222 if (isa<OverflowingBinaryOperator>(NewBO)) {
1223 NewBO->setHasNoSignedWrap(Inst.hasNoSignedWrap());
1224 NewBO->setHasNoUnsignedWrap(Inst.hasNoUnsignedWrap());
1226 if (isa<PossiblyExactOperator>(NewBO))
1227 NewBO->setIsExact(Inst.isExact());
1232 /// \brief Makes transformation of binary operation specific for vector types.
1233 /// \param Inst Binary operator to transform.
1234 /// \return Pointer to node that must replace the original binary operator, or
1235 /// null pointer if no transformation was made.
1236 Value *InstCombiner::SimplifyVectorOp(BinaryOperator &Inst) {
1237 if (!Inst.getType()->isVectorTy()) return nullptr;
1239 // It may not be safe to reorder shuffles and things like div, urem, etc.
1240 // because we may trap when executing those ops on unknown vector elements.
1242 if (!isSafeToSpeculativelyExecute(&Inst, DL)) return nullptr;
1244 unsigned VWidth = cast<VectorType>(Inst.getType())->getNumElements();
1245 Value *LHS = Inst.getOperand(0), *RHS = Inst.getOperand(1);
1246 assert(cast<VectorType>(LHS->getType())->getNumElements() == VWidth);
1247 assert(cast<VectorType>(RHS->getType())->getNumElements() == VWidth);
1249 // If both arguments of binary operation are shuffles, which use the same
1250 // mask and shuffle within a single vector, it is worthwhile to move the
1251 // shuffle after binary operation:
1252 // Op(shuffle(v1, m), shuffle(v2, m)) -> shuffle(Op(v1, v2), m)
1253 if (isa<ShuffleVectorInst>(LHS) && isa<ShuffleVectorInst>(RHS)) {
1254 ShuffleVectorInst *LShuf = cast<ShuffleVectorInst>(LHS);
1255 ShuffleVectorInst *RShuf = cast<ShuffleVectorInst>(RHS);
1256 if (isa<UndefValue>(LShuf->getOperand(1)) &&
1257 isa<UndefValue>(RShuf->getOperand(1)) &&
1258 LShuf->getOperand(0)->getType() == RShuf->getOperand(0)->getType() &&
1259 LShuf->getMask() == RShuf->getMask()) {
1260 Value *NewBO = CreateBinOpAsGiven(Inst, LShuf->getOperand(0),
1261 RShuf->getOperand(0), Builder);
1262 Value *Res = Builder->CreateShuffleVector(NewBO,
1263 UndefValue::get(NewBO->getType()), LShuf->getMask());
1268 // If one argument is a shuffle within one vector, the other is a constant,
1269 // try moving the shuffle after the binary operation.
1270 ShuffleVectorInst *Shuffle = nullptr;
1271 Constant *C1 = nullptr;
1272 if (isa<ShuffleVectorInst>(LHS)) Shuffle = cast<ShuffleVectorInst>(LHS);
1273 if (isa<ShuffleVectorInst>(RHS)) Shuffle = cast<ShuffleVectorInst>(RHS);
1274 if (isa<Constant>(LHS)) C1 = cast<Constant>(LHS);
1275 if (isa<Constant>(RHS)) C1 = cast<Constant>(RHS);
1276 if (Shuffle && C1 &&
1277 (isa<ConstantVector>(C1) || isa<ConstantDataVector>(C1)) &&
1278 isa<UndefValue>(Shuffle->getOperand(1)) &&
1279 Shuffle->getType() == Shuffle->getOperand(0)->getType()) {
1280 SmallVector<int, 16> ShMask = Shuffle->getShuffleMask();
1281 // Find constant C2 that has property:
1282 // shuffle(C2, ShMask) = C1
1283 // If such constant does not exist (example: ShMask=<0,0> and C1=<1,2>)
1284 // reorder is not possible.
1285 SmallVector<Constant*, 16> C2M(VWidth,
1286 UndefValue::get(C1->getType()->getScalarType()));
1287 bool MayChange = true;
1288 for (unsigned I = 0; I < VWidth; ++I) {
1289 if (ShMask[I] >= 0) {
1290 assert(ShMask[I] < (int)VWidth);
1291 if (!isa<UndefValue>(C2M[ShMask[I]])) {
1295 C2M[ShMask[I]] = C1->getAggregateElement(I);
1299 Constant *C2 = ConstantVector::get(C2M);
1300 Value *NewLHS, *NewRHS;
1301 if (isa<Constant>(LHS)) {
1303 NewRHS = Shuffle->getOperand(0);
1305 NewLHS = Shuffle->getOperand(0);
1308 Value *NewBO = CreateBinOpAsGiven(Inst, NewLHS, NewRHS, Builder);
1309 Value *Res = Builder->CreateShuffleVector(NewBO,
1310 UndefValue::get(Inst.getType()), Shuffle->getMask());
1318 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1319 SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
1321 if (Value *V = SimplifyGEPInst(Ops, DL, TLI, DT, AC))
1322 return ReplaceInstUsesWith(GEP, V);
1324 Value *PtrOp = GEP.getOperand(0);
1326 // Eliminate unneeded casts for indices, and replace indices which displace
1327 // by multiples of a zero size type with zero.
1329 bool MadeChange = false;
1330 Type *IntPtrTy = DL->getIntPtrType(GEP.getPointerOperandType());
1332 gep_type_iterator GTI = gep_type_begin(GEP);
1333 for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end();
1334 I != E; ++I, ++GTI) {
1335 // Skip indices into struct types.
1336 SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI);
1337 if (!SeqTy) continue;
1339 // If the element type has zero size then any index over it is equivalent
1340 // to an index of zero, so replace it with zero if it is not zero already.
1341 if (SeqTy->getElementType()->isSized() &&
1342 DL->getTypeAllocSize(SeqTy->getElementType()) == 0)
1343 if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) {
1344 *I = Constant::getNullValue(IntPtrTy);
1348 Type *IndexTy = (*I)->getType();
1349 if (IndexTy != IntPtrTy) {
1350 // If we are using a wider index than needed for this platform, shrink
1351 // it to what we need. If narrower, sign-extend it to what we need.
1352 // This explicit cast can make subsequent optimizations more obvious.
1353 *I = Builder->CreateIntCast(*I, IntPtrTy, true);
1357 if (MadeChange) return &GEP;
1360 // Check to see if the inputs to the PHI node are getelementptr instructions.
1361 if (PHINode *PN = dyn_cast<PHINode>(PtrOp)) {
1362 GetElementPtrInst *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0));
1368 for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) {
1369 GetElementPtrInst *Op2 = dyn_cast<GetElementPtrInst>(*I);
1370 if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands())
1373 // Keep track of the type as we walk the GEP.
1374 Type *CurTy = Op1->getOperand(0)->getType()->getScalarType();
1376 for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) {
1377 if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType())
1380 if (Op1->getOperand(J) != Op2->getOperand(J)) {
1382 // We have not seen any differences yet in the GEPs feeding the
1383 // PHI yet, so we record this one if it is allowed to be a
1386 // The first two arguments can vary for any GEP, the rest have to be
1387 // static for struct slots
1388 if (J > 1 && CurTy->isStructTy())
1393 // The GEP is different by more than one input. While this could be
1394 // extended to support GEPs that vary by more than one variable it
1395 // doesn't make sense since it greatly increases the complexity and
1396 // would result in an R+R+R addressing mode which no backend
1397 // directly supports and would need to be broken into several
1398 // simpler instructions anyway.
1403 // Sink down a layer of the type for the next iteration.
1405 if (CompositeType *CT = dyn_cast<CompositeType>(CurTy)) {
1406 CurTy = CT->getTypeAtIndex(Op1->getOperand(J));
1414 GetElementPtrInst *NewGEP = cast<GetElementPtrInst>(Op1->clone());
1417 // All the GEPs feeding the PHI are identical. Clone one down into our
1418 // BB so that it can be merged with the current GEP.
1419 GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
1422 // All the GEPs feeding the PHI differ at a single offset. Clone a GEP
1423 // into the current block so it can be merged, and create a new PHI to
1425 Instruction *InsertPt = Builder->GetInsertPoint();
1426 Builder->SetInsertPoint(PN);
1427 PHINode *NewPN = Builder->CreatePHI(Op1->getOperand(DI)->getType(),
1428 PN->getNumOperands());
1429 Builder->SetInsertPoint(InsertPt);
1431 for (auto &I : PN->operands())
1432 NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI),
1433 PN->getIncomingBlock(I));
1435 NewGEP->setOperand(DI, NewPN);
1436 GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
1438 NewGEP->setOperand(DI, NewPN);
1441 GEP.setOperand(0, NewGEP);
1445 // Combine Indices - If the source pointer to this getelementptr instruction
1446 // is a getelementptr instruction, combine the indices of the two
1447 // getelementptr instructions into a single instruction.
1449 if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
1450 if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src))
1453 // Note that if our source is a gep chain itself then we wait for that
1454 // chain to be resolved before we perform this transformation. This
1455 // avoids us creating a TON of code in some cases.
1456 if (GEPOperator *SrcGEP =
1457 dyn_cast<GEPOperator>(Src->getOperand(0)))
1458 if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP))
1459 return nullptr; // Wait until our source is folded to completion.
1461 SmallVector<Value*, 8> Indices;
1463 // Find out whether the last index in the source GEP is a sequential idx.
1464 bool EndsWithSequential = false;
1465 for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
1467 EndsWithSequential = !(*I)->isStructTy();
1469 // Can we combine the two pointer arithmetics offsets?
1470 if (EndsWithSequential) {
1471 // Replace: gep (gep %P, long B), long A, ...
1472 // With: T = long A+B; gep %P, T, ...
1475 Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
1476 Value *GO1 = GEP.getOperand(1);
1477 if (SO1 == Constant::getNullValue(SO1->getType())) {
1479 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
1482 // If they aren't the same type, then the input hasn't been processed
1483 // by the loop above yet (which canonicalizes sequential index types to
1484 // intptr_t). Just avoid transforming this until the input has been
1486 if (SO1->getType() != GO1->getType())
1488 Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum");
1491 // Update the GEP in place if possible.
1492 if (Src->getNumOperands() == 2) {
1493 GEP.setOperand(0, Src->getOperand(0));
1494 GEP.setOperand(1, Sum);
1497 Indices.append(Src->op_begin()+1, Src->op_end()-1);
1498 Indices.push_back(Sum);
1499 Indices.append(GEP.op_begin()+2, GEP.op_end());
1500 } else if (isa<Constant>(*GEP.idx_begin()) &&
1501 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
1502 Src->getNumOperands() != 1) {
1503 // Otherwise we can do the fold if the first index of the GEP is a zero
1504 Indices.append(Src->op_begin()+1, Src->op_end());
1505 Indices.append(GEP.idx_begin()+1, GEP.idx_end());
1508 if (!Indices.empty())
1509 return (GEP.isInBounds() && Src->isInBounds()) ?
1510 GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices,
1512 GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName());
1515 if (DL && GEP.getNumIndices() == 1) {
1516 unsigned AS = GEP.getPointerAddressSpace();
1517 if (GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
1518 DL->getPointerSizeInBits(AS)) {
1519 Type *PtrTy = GEP.getPointerOperandType();
1520 Type *Ty = PtrTy->getPointerElementType();
1521 uint64_t TyAllocSize = DL->getTypeAllocSize(Ty);
1523 bool Matched = false;
1526 if (TyAllocSize == 1) {
1527 V = GEP.getOperand(1);
1529 } else if (match(GEP.getOperand(1),
1530 m_AShr(m_Value(V), m_ConstantInt(C)))) {
1531 if (TyAllocSize == 1ULL << C)
1533 } else if (match(GEP.getOperand(1),
1534 m_SDiv(m_Value(V), m_ConstantInt(C)))) {
1535 if (TyAllocSize == C)
1540 // Canonicalize (gep i8* X, -(ptrtoint Y))
1541 // to (inttoptr (sub (ptrtoint X), (ptrtoint Y)))
1542 // The GEP pattern is emitted by the SCEV expander for certain kinds of
1543 // pointer arithmetic.
1544 if (match(V, m_Neg(m_PtrToInt(m_Value())))) {
1545 Operator *Index = cast<Operator>(V);
1546 Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType());
1547 Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1));
1548 return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
1550 // Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X))
1553 if (match(V, m_Sub(m_PtrToInt(m_Value(Y)),
1554 m_PtrToInt(m_Specific(GEP.getOperand(0)))))) {
1555 return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y,
1562 // Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
1563 Value *StrippedPtr = PtrOp->stripPointerCasts();
1564 PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType());
1566 // We do not handle pointer-vector geps here.
1570 if (StrippedPtr != PtrOp) {
1571 bool HasZeroPointerIndex = false;
1572 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
1573 HasZeroPointerIndex = C->isZero();
1575 // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
1576 // into : GEP [10 x i8]* X, i32 0, ...
1578 // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ...
1579 // into : GEP i8* X, ...
1581 // This occurs when the program declares an array extern like "int X[];"
1582 if (HasZeroPointerIndex) {
1583 PointerType *CPTy = cast<PointerType>(PtrOp->getType());
1584 if (ArrayType *CATy =
1585 dyn_cast<ArrayType>(CPTy->getElementType())) {
1586 // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ?
1587 if (CATy->getElementType() == StrippedPtrTy->getElementType()) {
1588 // -> GEP i8* X, ...
1589 SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end());
1590 GetElementPtrInst *Res =
1591 GetElementPtrInst::Create(StrippedPtr, Idx, GEP.getName());
1592 Res->setIsInBounds(GEP.isInBounds());
1593 if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace())
1595 // Insert Res, and create an addrspacecast.
1597 // GEP (addrspacecast i8 addrspace(1)* X to [0 x i8]*), i32 0, ...
1599 // %0 = GEP i8 addrspace(1)* X, ...
1600 // addrspacecast i8 addrspace(1)* %0 to i8*
1601 return new AddrSpaceCastInst(Builder->Insert(Res), GEP.getType());
1604 if (ArrayType *XATy =
1605 dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){
1606 // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ?
1607 if (CATy->getElementType() == XATy->getElementType()) {
1608 // -> GEP [10 x i8]* X, i32 0, ...
1609 // At this point, we know that the cast source type is a pointer
1610 // to an array of the same type as the destination pointer
1611 // array. Because the array type is never stepped over (there
1612 // is a leading zero) we can fold the cast into this GEP.
1613 if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) {
1614 GEP.setOperand(0, StrippedPtr);
1617 // Cannot replace the base pointer directly because StrippedPtr's
1618 // address space is different. Instead, create a new GEP followed by
1619 // an addrspacecast.
1621 // GEP (addrspacecast [10 x i8] addrspace(1)* X to [0 x i8]*),
1624 // %0 = GEP [10 x i8] addrspace(1)* X, ...
1625 // addrspacecast i8 addrspace(1)* %0 to i8*
1626 SmallVector<Value*, 8> Idx(GEP.idx_begin(), GEP.idx_end());
1627 Value *NewGEP = GEP.isInBounds() ?
1628 Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) :
1629 Builder->CreateGEP(StrippedPtr, Idx, GEP.getName());
1630 return new AddrSpaceCastInst(NewGEP, GEP.getType());
1634 } else if (GEP.getNumOperands() == 2) {
1635 // Transform things like:
1636 // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V
1637 // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast
1638 Type *SrcElTy = StrippedPtrTy->getElementType();
1639 Type *ResElTy = PtrOp->getType()->getPointerElementType();
1640 if (DL && SrcElTy->isArrayTy() &&
1641 DL->getTypeAllocSize(SrcElTy->getArrayElementType()) ==
1642 DL->getTypeAllocSize(ResElTy)) {
1643 Type *IdxType = DL->getIntPtrType(GEP.getType());
1644 Value *Idx[2] = { Constant::getNullValue(IdxType), GEP.getOperand(1) };
1645 Value *NewGEP = GEP.isInBounds() ?
1646 Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) :
1647 Builder->CreateGEP(StrippedPtr, Idx, GEP.getName());
1649 // V and GEP are both pointer types --> BitCast
1650 return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP,
1654 // Transform things like:
1655 // %V = mul i64 %N, 4
1656 // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
1657 // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast
1658 if (DL && ResElTy->isSized() && SrcElTy->isSized()) {
1659 // Check that changing the type amounts to dividing the index by a scale
1661 uint64_t ResSize = DL->getTypeAllocSize(ResElTy);
1662 uint64_t SrcSize = DL->getTypeAllocSize(SrcElTy);
1663 if (ResSize && SrcSize % ResSize == 0) {
1664 Value *Idx = GEP.getOperand(1);
1665 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
1666 uint64_t Scale = SrcSize / ResSize;
1668 // Earlier transforms ensure that the index has type IntPtrType, which
1669 // considerably simplifies the logic by eliminating implicit casts.
1670 assert(Idx->getType() == DL->getIntPtrType(GEP.getType()) &&
1671 "Index not cast to pointer width?");
1674 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
1675 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
1676 // If the multiplication NewIdx * Scale may overflow then the new
1677 // GEP may not be "inbounds".
1678 Value *NewGEP = GEP.isInBounds() && NSW ?
1679 Builder->CreateInBoundsGEP(StrippedPtr, NewIdx, GEP.getName()) :
1680 Builder->CreateGEP(StrippedPtr, NewIdx, GEP.getName());
1682 // The NewGEP must be pointer typed, so must the old one -> BitCast
1683 return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP,
1689 // Similarly, transform things like:
1690 // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp
1691 // (where tmp = 8*tmp2) into:
1692 // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast
1693 if (DL && ResElTy->isSized() && SrcElTy->isSized() &&
1694 SrcElTy->isArrayTy()) {
1695 // Check that changing to the array element type amounts to dividing the
1696 // index by a scale factor.
1697 uint64_t ResSize = DL->getTypeAllocSize(ResElTy);
1698 uint64_t ArrayEltSize
1699 = DL->getTypeAllocSize(SrcElTy->getArrayElementType());
1700 if (ResSize && ArrayEltSize % ResSize == 0) {
1701 Value *Idx = GEP.getOperand(1);
1702 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
1703 uint64_t Scale = ArrayEltSize / ResSize;
1705 // Earlier transforms ensure that the index has type IntPtrType, which
1706 // considerably simplifies the logic by eliminating implicit casts.
1707 assert(Idx->getType() == DL->getIntPtrType(GEP.getType()) &&
1708 "Index not cast to pointer width?");
1711 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
1712 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
1713 // If the multiplication NewIdx * Scale may overflow then the new
1714 // GEP may not be "inbounds".
1716 Constant::getNullValue(DL->getIntPtrType(GEP.getType())),
1720 Value *NewGEP = GEP.isInBounds() && NSW ?
1721 Builder->CreateInBoundsGEP(StrippedPtr, Off, GEP.getName()) :
1722 Builder->CreateGEP(StrippedPtr, Off, GEP.getName());
1723 // The NewGEP must be pointer typed, so must the old one -> BitCast
1724 return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP,
1735 // addrspacecast between types is canonicalized as a bitcast, then an
1736 // addrspacecast. To take advantage of the below bitcast + struct GEP, look
1737 // through the addrspacecast.
1738 if (AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(PtrOp)) {
1739 // X = bitcast A addrspace(1)* to B addrspace(1)*
1740 // Y = addrspacecast A addrspace(1)* to B addrspace(2)*
1741 // Z = gep Y, <...constant indices...>
1742 // Into an addrspacecasted GEP of the struct.
1743 if (BitCastInst *BC = dyn_cast<BitCastInst>(ASC->getOperand(0)))
1747 /// See if we can simplify:
1748 /// X = bitcast A* to B*
1749 /// Y = gep X, <...constant indices...>
1750 /// into a gep of the original struct. This is important for SROA and alias
1751 /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
1752 if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
1753 Value *Operand = BCI->getOperand(0);
1754 PointerType *OpType = cast<PointerType>(Operand->getType());
1755 unsigned OffsetBits = DL->getPointerTypeSizeInBits(GEP.getType());
1756 APInt Offset(OffsetBits, 0);
1757 if (!isa<BitCastInst>(Operand) &&
1758 GEP.accumulateConstantOffset(*DL, Offset)) {
1760 // If this GEP instruction doesn't move the pointer, just replace the GEP
1761 // with a bitcast of the real input to the dest type.
1763 // If the bitcast is of an allocation, and the allocation will be
1764 // converted to match the type of the cast, don't touch this.
1765 if (isa<AllocaInst>(Operand) || isAllocationFn(Operand, TLI)) {
1766 // See if the bitcast simplifies, if so, don't nuke this GEP yet.
1767 if (Instruction *I = visitBitCast(*BCI)) {
1770 BCI->getParent()->getInstList().insert(BCI, I);
1771 ReplaceInstUsesWith(*BCI, I);
1777 if (Operand->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
1778 return new AddrSpaceCastInst(Operand, GEP.getType());
1779 return new BitCastInst(Operand, GEP.getType());
1782 // Otherwise, if the offset is non-zero, we need to find out if there is a
1783 // field at Offset in 'A's type. If so, we can pull the cast through the
1785 SmallVector<Value*, 8> NewIndices;
1786 if (FindElementAtOffset(OpType, Offset.getSExtValue(), NewIndices)) {
1787 Value *NGEP = GEP.isInBounds() ?
1788 Builder->CreateInBoundsGEP(Operand, NewIndices) :
1789 Builder->CreateGEP(Operand, NewIndices);
1791 if (NGEP->getType() == GEP.getType())
1792 return ReplaceInstUsesWith(GEP, NGEP);
1793 NGEP->takeName(&GEP);
1795 if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
1796 return new AddrSpaceCastInst(NGEP, GEP.getType());
1797 return new BitCastInst(NGEP, GEP.getType());
1806 isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users,
1807 const TargetLibraryInfo *TLI) {
1808 SmallVector<Instruction*, 4> Worklist;
1809 Worklist.push_back(AI);
1812 Instruction *PI = Worklist.pop_back_val();
1813 for (User *U : PI->users()) {
1814 Instruction *I = cast<Instruction>(U);
1815 switch (I->getOpcode()) {
1817 // Give up the moment we see something we can't handle.
1820 case Instruction::BitCast:
1821 case Instruction::GetElementPtr:
1823 Worklist.push_back(I);
1826 case Instruction::ICmp: {
1827 ICmpInst *ICI = cast<ICmpInst>(I);
1828 // We can fold eq/ne comparisons with null to false/true, respectively.
1829 if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1)))
1835 case Instruction::Call:
1836 // Ignore no-op and store intrinsics.
1837 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1838 switch (II->getIntrinsicID()) {
1842 case Intrinsic::memmove:
1843 case Intrinsic::memcpy:
1844 case Intrinsic::memset: {
1845 MemIntrinsic *MI = cast<MemIntrinsic>(II);
1846 if (MI->isVolatile() || MI->getRawDest() != PI)
1850 case Intrinsic::dbg_declare:
1851 case Intrinsic::dbg_value:
1852 case Intrinsic::invariant_start:
1853 case Intrinsic::invariant_end:
1854 case Intrinsic::lifetime_start:
1855 case Intrinsic::lifetime_end:
1856 case Intrinsic::objectsize:
1862 if (isFreeCall(I, TLI)) {
1868 case Instruction::Store: {
1869 StoreInst *SI = cast<StoreInst>(I);
1870 if (SI->isVolatile() || SI->getPointerOperand() != PI)
1876 llvm_unreachable("missing a return?");
1878 } while (!Worklist.empty());
1882 Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
1883 // If we have a malloc call which is only used in any amount of comparisons
1884 // to null and free calls, delete the calls and replace the comparisons with
1885 // true or false as appropriate.
1886 SmallVector<WeakVH, 64> Users;
1887 if (isAllocSiteRemovable(&MI, Users, TLI)) {
1888 for (unsigned i = 0, e = Users.size(); i != e; ++i) {
1889 Instruction *I = cast_or_null<Instruction>(&*Users[i]);
1892 if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
1893 ReplaceInstUsesWith(*C,
1894 ConstantInt::get(Type::getInt1Ty(C->getContext()),
1895 C->isFalseWhenEqual()));
1896 } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
1897 ReplaceInstUsesWith(*I, UndefValue::get(I->getType()));
1898 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1899 if (II->getIntrinsicID() == Intrinsic::objectsize) {
1900 ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1));
1901 uint64_t DontKnow = CI->isZero() ? -1ULL : 0;
1902 ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow));
1905 EraseInstFromFunction(*I);
1908 if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
1909 // Replace invoke with a NOP intrinsic to maintain the original CFG
1910 Module *M = II->getParent()->getParent()->getParent();
1911 Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing);
1912 InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(),
1913 None, "", II->getParent());
1915 return EraseInstFromFunction(MI);
1920 /// \brief Move the call to free before a NULL test.
1922 /// Check if this free is accessed after its argument has been test
1923 /// against NULL (property 0).
1924 /// If yes, it is legal to move this call in its predecessor block.
1926 /// The move is performed only if the block containing the call to free
1927 /// will be removed, i.e.:
1928 /// 1. it has only one predecessor P, and P has two successors
1929 /// 2. it contains the call and an unconditional branch
1930 /// 3. its successor is the same as its predecessor's successor
1932 /// The profitability is out-of concern here and this function should
1933 /// be called only if the caller knows this transformation would be
1934 /// profitable (e.g., for code size).
1935 static Instruction *
1936 tryToMoveFreeBeforeNullTest(CallInst &FI) {
1937 Value *Op = FI.getArgOperand(0);
1938 BasicBlock *FreeInstrBB = FI.getParent();
1939 BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor();
1941 // Validate part of constraint #1: Only one predecessor
1942 // FIXME: We can extend the number of predecessor, but in that case, we
1943 // would duplicate the call to free in each predecessor and it may
1944 // not be profitable even for code size.
1948 // Validate constraint #2: Does this block contains only the call to
1949 // free and an unconditional branch?
1950 // FIXME: We could check if we can speculate everything in the
1951 // predecessor block
1952 if (FreeInstrBB->size() != 2)
1955 if (!match(FreeInstrBB->getTerminator(), m_UnconditionalBr(SuccBB)))
1958 // Validate the rest of constraint #1 by matching on the pred branch.
1959 TerminatorInst *TI = PredBB->getTerminator();
1960 BasicBlock *TrueBB, *FalseBB;
1961 ICmpInst::Predicate Pred;
1962 if (!match(TI, m_Br(m_ICmp(Pred, m_Specific(Op), m_Zero()), TrueBB, FalseBB)))
1964 if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE)
1967 // Validate constraint #3: Ensure the null case just falls through.
1968 if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB))
1970 assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) &&
1971 "Broken CFG: missing edge from predecessor to successor");
1978 Instruction *InstCombiner::visitFree(CallInst &FI) {
1979 Value *Op = FI.getArgOperand(0);
1981 // free undef -> unreachable.
1982 if (isa<UndefValue>(Op)) {
1983 // Insert a new store to null because we cannot modify the CFG here.
1984 Builder->CreateStore(ConstantInt::getTrue(FI.getContext()),
1985 UndefValue::get(Type::getInt1PtrTy(FI.getContext())));
1986 return EraseInstFromFunction(FI);
1989 // If we have 'free null' delete the instruction. This can happen in stl code
1990 // when lots of inlining happens.
1991 if (isa<ConstantPointerNull>(Op))
1992 return EraseInstFromFunction(FI);
1994 // If we optimize for code size, try to move the call to free before the null
1995 // test so that simplify cfg can remove the empty block and dead code
1996 // elimination the branch. I.e., helps to turn something like:
1997 // if (foo) free(foo);
2001 if (Instruction *I = tryToMoveFreeBeforeNullTest(FI))
2007 Instruction *InstCombiner::visitReturnInst(ReturnInst &RI) {
2008 if (RI.getNumOperands() == 0) // ret void
2011 Value *ResultOp = RI.getOperand(0);
2012 Type *VTy = ResultOp->getType();
2013 if (!VTy->isIntegerTy())
2016 // There might be assume intrinsics dominating this return that completely
2017 // determine the value. If so, constant fold it.
2018 unsigned BitWidth = VTy->getPrimitiveSizeInBits();
2019 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
2020 computeKnownBits(ResultOp, KnownZero, KnownOne, 0, &RI);
2021 if ((KnownZero|KnownOne).isAllOnesValue())
2022 RI.setOperand(0, Constant::getIntegerValue(VTy, KnownOne));
2027 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
2028 // Change br (not X), label True, label False to: br X, label False, True
2030 BasicBlock *TrueDest;
2031 BasicBlock *FalseDest;
2032 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
2033 !isa<Constant>(X)) {
2034 // Swap Destinations and condition...
2036 BI.swapSuccessors();
2040 // Canonicalize fcmp_one -> fcmp_oeq
2041 FCmpInst::Predicate FPred; Value *Y;
2042 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)),
2043 TrueDest, FalseDest)) &&
2044 BI.getCondition()->hasOneUse())
2045 if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE ||
2046 FPred == FCmpInst::FCMP_OGE) {
2047 FCmpInst *Cond = cast<FCmpInst>(BI.getCondition());
2048 Cond->setPredicate(FCmpInst::getInversePredicate(FPred));
2050 // Swap Destinations and condition.
2051 BI.swapSuccessors();
2056 // Canonicalize icmp_ne -> icmp_eq
2057 ICmpInst::Predicate IPred;
2058 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)),
2059 TrueDest, FalseDest)) &&
2060 BI.getCondition()->hasOneUse())
2061 if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE ||
2062 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE ||
2063 IPred == ICmpInst::ICMP_SGE) {
2064 ICmpInst *Cond = cast<ICmpInst>(BI.getCondition());
2065 Cond->setPredicate(ICmpInst::getInversePredicate(IPred));
2066 // Swap Destinations and condition.
2067 BI.swapSuccessors();
2075 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
2076 Value *Cond = SI.getCondition();
2077 unsigned BitWidth = cast<IntegerType>(Cond->getType())->getBitWidth();
2078 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
2079 computeKnownBits(Cond, KnownZero, KnownOne);
2080 unsigned LeadingKnownZeros = KnownZero.countLeadingOnes();
2081 unsigned LeadingKnownOnes = KnownOne.countLeadingOnes();
2083 // Compute the number of leading bits we can ignore.
2084 for (auto &C : SI.cases()) {
2085 LeadingKnownZeros = std::min(
2086 LeadingKnownZeros, C.getCaseValue()->getValue().countLeadingZeros());
2087 LeadingKnownOnes = std::min(
2088 LeadingKnownOnes, C.getCaseValue()->getValue().countLeadingOnes());
2091 unsigned NewWidth = BitWidth - std::max(LeadingKnownZeros, LeadingKnownOnes);
2093 // Truncate the condition operand if the new type is equal to or larger than
2094 // the largest legal integer type. We need to be conservative here since
2095 // x86 generates redundant zero-extenstion instructions if the operand is
2096 // truncated to i8 or i16.
2097 bool TruncCond = false;
2098 if (DL && BitWidth > NewWidth &&
2099 NewWidth >= DL->getLargestLegalIntTypeSize()) {
2101 IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth);
2102 Builder->SetInsertPoint(&SI);
2103 Value *NewCond = Builder->CreateTrunc(SI.getCondition(), Ty, "trunc");
2104 SI.setCondition(NewCond);
2106 for (auto &C : SI.cases())
2107 static_cast<SwitchInst::CaseIt *>(&C)->setValue(ConstantInt::get(
2108 SI.getContext(), C.getCaseValue()->getValue().trunc(NewWidth)));
2111 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
2112 if (I->getOpcode() == Instruction::Add)
2113 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
2114 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
2115 // Skip the first item since that's the default case.
2116 for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
2118 ConstantInt* CaseVal = i.getCaseValue();
2119 Constant *LHS = CaseVal;
2121 LHS = LeadingKnownZeros
2122 ? ConstantExpr::getZExt(CaseVal, Cond->getType())
2123 : ConstantExpr::getSExt(CaseVal, Cond->getType());
2124 Constant* NewCaseVal = ConstantExpr::getSub(LHS, AddRHS);
2125 assert(isa<ConstantInt>(NewCaseVal) &&
2126 "Result of expression should be constant");
2127 i.setValue(cast<ConstantInt>(NewCaseVal));
2129 SI.setCondition(I->getOperand(0));
2135 return TruncCond ? &SI : nullptr;
2138 Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {
2139 Value *Agg = EV.getAggregateOperand();
2141 if (!EV.hasIndices())
2142 return ReplaceInstUsesWith(EV, Agg);
2144 if (Constant *C = dyn_cast<Constant>(Agg)) {
2145 if (Constant *C2 = C->getAggregateElement(*EV.idx_begin())) {
2146 if (EV.getNumIndices() == 0)
2147 return ReplaceInstUsesWith(EV, C2);
2148 // Extract the remaining indices out of the constant indexed by the
2150 return ExtractValueInst::Create(C2, EV.getIndices().slice(1));
2152 return nullptr; // Can't handle other constants
2155 if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
2156 // We're extracting from an insertvalue instruction, compare the indices
2157 const unsigned *exti, *exte, *insi, *inse;
2158 for (exti = EV.idx_begin(), insi = IV->idx_begin(),
2159 exte = EV.idx_end(), inse = IV->idx_end();
2160 exti != exte && insi != inse;
2163 // The insert and extract both reference distinctly different elements.
2164 // This means the extract is not influenced by the insert, and we can
2165 // replace the aggregate operand of the extract with the aggregate
2166 // operand of the insert. i.e., replace
2167 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
2168 // %E = extractvalue { i32, { i32 } } %I, 0
2170 // %E = extractvalue { i32, { i32 } } %A, 0
2171 return ExtractValueInst::Create(IV->getAggregateOperand(),
2174 if (exti == exte && insi == inse)
2175 // Both iterators are at the end: Index lists are identical. Replace
2176 // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
2177 // %C = extractvalue { i32, { i32 } } %B, 1, 0
2179 return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand());
2181 // The extract list is a prefix of the insert list. i.e. replace
2182 // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
2183 // %E = extractvalue { i32, { i32 } } %I, 1
2185 // %X = extractvalue { i32, { i32 } } %A, 1
2186 // %E = insertvalue { i32 } %X, i32 42, 0
2187 // by switching the order of the insert and extract (though the
2188 // insertvalue should be left in, since it may have other uses).
2189 Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(),
2191 return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
2192 makeArrayRef(insi, inse));
2195 // The insert list is a prefix of the extract list
2196 // We can simply remove the common indices from the extract and make it
2197 // operate on the inserted value instead of the insertvalue result.
2199 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
2200 // %E = extractvalue { i32, { i32 } } %I, 1, 0
2202 // %E extractvalue { i32 } { i32 42 }, 0
2203 return ExtractValueInst::Create(IV->getInsertedValueOperand(),
2204 makeArrayRef(exti, exte));
2206 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) {
2207 // We're extracting from an intrinsic, see if we're the only user, which
2208 // allows us to simplify multiple result intrinsics to simpler things that
2209 // just get one value.
2210 if (II->hasOneUse()) {
2211 // Check if we're grabbing the overflow bit or the result of a 'with
2212 // overflow' intrinsic. If it's the latter we can remove the intrinsic
2213 // and replace it with a traditional binary instruction.
2214 switch (II->getIntrinsicID()) {
2215 case Intrinsic::uadd_with_overflow:
2216 case Intrinsic::sadd_with_overflow:
2217 if (*EV.idx_begin() == 0) { // Normal result.
2218 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
2219 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
2220 EraseInstFromFunction(*II);
2221 return BinaryOperator::CreateAdd(LHS, RHS);
2224 // If the normal result of the add is dead, and the RHS is a constant,
2225 // we can transform this into a range comparison.
2226 // overflow = uadd a, -4 --> overflow = icmp ugt a, 3
2227 if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow)
2228 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1)))
2229 return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0),
2230 ConstantExpr::getNot(CI));
2232 case Intrinsic::usub_with_overflow:
2233 case Intrinsic::ssub_with_overflow:
2234 if (*EV.idx_begin() == 0) { // Normal result.
2235 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
2236 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
2237 EraseInstFromFunction(*II);
2238 return BinaryOperator::CreateSub(LHS, RHS);
2241 case Intrinsic::umul_with_overflow:
2242 case Intrinsic::smul_with_overflow:
2243 if (*EV.idx_begin() == 0) { // Normal result.
2244 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
2245 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
2246 EraseInstFromFunction(*II);
2247 return BinaryOperator::CreateMul(LHS, RHS);
2255 if (LoadInst *L = dyn_cast<LoadInst>(Agg))
2256 // If the (non-volatile) load only has one use, we can rewrite this to a
2257 // load from a GEP. This reduces the size of the load.
2258 // FIXME: If a load is used only by extractvalue instructions then this
2259 // could be done regardless of having multiple uses.
2260 if (L->isSimple() && L->hasOneUse()) {
2261 // extractvalue has integer indices, getelementptr has Value*s. Convert.
2262 SmallVector<Value*, 4> Indices;
2263 // Prefix an i32 0 since we need the first element.
2264 Indices.push_back(Builder->getInt32(0));
2265 for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end();
2267 Indices.push_back(Builder->getInt32(*I));
2269 // We need to insert these at the location of the old load, not at that of
2270 // the extractvalue.
2271 Builder->SetInsertPoint(L->getParent(), L);
2272 Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), Indices);
2273 // Returning the load directly will cause the main loop to insert it in
2274 // the wrong spot, so use ReplaceInstUsesWith().
2275 return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP));
2277 // We could simplify extracts from other values. Note that nested extracts may
2278 // already be simplified implicitly by the above: extract (extract (insert) )
2279 // will be translated into extract ( insert ( extract ) ) first and then just
2280 // the value inserted, if appropriate. Similarly for extracts from single-use
2281 // loads: extract (extract (load)) will be translated to extract (load (gep))
2282 // and if again single-use then via load (gep (gep)) to load (gep).
2283 // However, double extracts from e.g. function arguments or return values
2284 // aren't handled yet.
2288 enum Personality_Type {
2289 Unknown_Personality,
2290 GNU_Ada_Personality,
2291 GNU_CXX_Personality,
2292 GNU_ObjC_Personality
2295 /// RecognizePersonality - See if the given exception handling personality
2296 /// function is one that we understand. If so, return a description of it;
2297 /// otherwise return Unknown_Personality.
2298 static Personality_Type RecognizePersonality(Value *Pers) {
2299 Function *F = dyn_cast<Function>(Pers->stripPointerCasts());
2301 return Unknown_Personality;
2302 return StringSwitch<Personality_Type>(F->getName())
2303 .Case("__gnat_eh_personality", GNU_Ada_Personality)
2304 .Case("__gxx_personality_v0", GNU_CXX_Personality)
2305 .Case("__objc_personality_v0", GNU_ObjC_Personality)
2306 .Default(Unknown_Personality);
2309 /// isCatchAll - Return 'true' if the given typeinfo will match anything.
2310 static bool isCatchAll(Personality_Type Personality, Constant *TypeInfo) {
2311 switch (Personality) {
2312 case Unknown_Personality:
2314 case GNU_Ada_Personality:
2315 // While __gnat_all_others_value will match any Ada exception, it doesn't
2316 // match foreign exceptions (or didn't, before gcc-4.7).
2318 case GNU_CXX_Personality:
2319 case GNU_ObjC_Personality:
2320 return TypeInfo->isNullValue();
2322 llvm_unreachable("Unknown personality!");
2325 static bool shorter_filter(const Value *LHS, const Value *RHS) {
2327 cast<ArrayType>(LHS->getType())->getNumElements()
2329 cast<ArrayType>(RHS->getType())->getNumElements();
2332 Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) {
2333 // The logic here should be correct for any real-world personality function.
2334 // However if that turns out not to be true, the offending logic can always
2335 // be conditioned on the personality function, like the catch-all logic is.
2336 Personality_Type Personality = RecognizePersonality(LI.getPersonalityFn());
2338 // Simplify the list of clauses, eg by removing repeated catch clauses
2339 // (these are often created by inlining).
2340 bool MakeNewInstruction = false; // If true, recreate using the following:
2341 SmallVector<Constant *, 16> NewClauses; // - Clauses for the new instruction;
2342 bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup.
2344 SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already.
2345 for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) {
2346 bool isLastClause = i + 1 == e;
2347 if (LI.isCatch(i)) {
2349 Constant *CatchClause = LI.getClause(i);
2350 Constant *TypeInfo = CatchClause->stripPointerCasts();
2352 // If we already saw this clause, there is no point in having a second
2354 if (AlreadyCaught.insert(TypeInfo).second) {
2355 // This catch clause was not already seen.
2356 NewClauses.push_back(CatchClause);
2358 // Repeated catch clause - drop the redundant copy.
2359 MakeNewInstruction = true;
2362 // If this is a catch-all then there is no point in keeping any following
2363 // clauses or marking the landingpad as having a cleanup.
2364 if (isCatchAll(Personality, TypeInfo)) {
2366 MakeNewInstruction = true;
2367 CleanupFlag = false;
2371 // A filter clause. If any of the filter elements were already caught
2372 // then they can be dropped from the filter. It is tempting to try to
2373 // exploit the filter further by saying that any typeinfo that does not
2374 // occur in the filter can't be caught later (and thus can be dropped).
2375 // However this would be wrong, since typeinfos can match without being
2376 // equal (for example if one represents a C++ class, and the other some
2377 // class derived from it).
2378 assert(LI.isFilter(i) && "Unsupported landingpad clause!");
2379 Constant *FilterClause = LI.getClause(i);
2380 ArrayType *FilterType = cast<ArrayType>(FilterClause->getType());
2381 unsigned NumTypeInfos = FilterType->getNumElements();
2383 // An empty filter catches everything, so there is no point in keeping any
2384 // following clauses or marking the landingpad as having a cleanup. By
2385 // dealing with this case here the following code is made a bit simpler.
2386 if (!NumTypeInfos) {
2387 NewClauses.push_back(FilterClause);
2389 MakeNewInstruction = true;
2390 CleanupFlag = false;
2394 bool MakeNewFilter = false; // If true, make a new filter.
2395 SmallVector<Constant *, 16> NewFilterElts; // New elements.
2396 if (isa<ConstantAggregateZero>(FilterClause)) {
2397 // Not an empty filter - it contains at least one null typeinfo.
2398 assert(NumTypeInfos > 0 && "Should have handled empty filter already!");
2399 Constant *TypeInfo =
2400 Constant::getNullValue(FilterType->getElementType());
2401 // If this typeinfo is a catch-all then the filter can never match.
2402 if (isCatchAll(Personality, TypeInfo)) {
2403 // Throw the filter away.
2404 MakeNewInstruction = true;
2408 // There is no point in having multiple copies of this typeinfo, so
2409 // discard all but the first copy if there is more than one.
2410 NewFilterElts.push_back(TypeInfo);
2411 if (NumTypeInfos > 1)
2412 MakeNewFilter = true;
2414 ConstantArray *Filter = cast<ConstantArray>(FilterClause);
2415 SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements.
2416 NewFilterElts.reserve(NumTypeInfos);
2418 // Remove any filter elements that were already caught or that already
2419 // occurred in the filter. While there, see if any of the elements are
2420 // catch-alls. If so, the filter can be discarded.
2421 bool SawCatchAll = false;
2422 for (unsigned j = 0; j != NumTypeInfos; ++j) {
2423 Constant *Elt = Filter->getOperand(j);
2424 Constant *TypeInfo = Elt->stripPointerCasts();
2425 if (isCatchAll(Personality, TypeInfo)) {
2426 // This element is a catch-all. Bail out, noting this fact.
2430 if (AlreadyCaught.count(TypeInfo))
2431 // Already caught by an earlier clause, so having it in the filter
2434 // There is no point in having multiple copies of the same typeinfo in
2435 // a filter, so only add it if we didn't already.
2436 if (SeenInFilter.insert(TypeInfo).second)
2437 NewFilterElts.push_back(cast<Constant>(Elt));
2439 // A filter containing a catch-all cannot match anything by definition.
2441 // Throw the filter away.
2442 MakeNewInstruction = true;
2446 // If we dropped something from the filter, make a new one.
2447 if (NewFilterElts.size() < NumTypeInfos)
2448 MakeNewFilter = true;
2450 if (MakeNewFilter) {
2451 FilterType = ArrayType::get(FilterType->getElementType(),
2452 NewFilterElts.size());
2453 FilterClause = ConstantArray::get(FilterType, NewFilterElts);
2454 MakeNewInstruction = true;
2457 NewClauses.push_back(FilterClause);
2459 // If the new filter is empty then it will catch everything so there is
2460 // no point in keeping any following clauses or marking the landingpad
2461 // as having a cleanup. The case of the original filter being empty was
2462 // already handled above.
2463 if (MakeNewFilter && !NewFilterElts.size()) {
2464 assert(MakeNewInstruction && "New filter but not a new instruction!");
2465 CleanupFlag = false;
2471 // If several filters occur in a row then reorder them so that the shortest
2472 // filters come first (those with the smallest number of elements). This is
2473 // advantageous because shorter filters are more likely to match, speeding up
2474 // unwinding, but mostly because it increases the effectiveness of the other
2475 // filter optimizations below.
2476 for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) {
2478 // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters.
2479 for (j = i; j != e; ++j)
2480 if (!isa<ArrayType>(NewClauses[j]->getType()))
2483 // Check whether the filters are already sorted by length. We need to know
2484 // if sorting them is actually going to do anything so that we only make a
2485 // new landingpad instruction if it does.
2486 for (unsigned k = i; k + 1 < j; ++k)
2487 if (shorter_filter(NewClauses[k+1], NewClauses[k])) {
2488 // Not sorted, so sort the filters now. Doing an unstable sort would be
2489 // correct too but reordering filters pointlessly might confuse users.
2490 std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j,
2492 MakeNewInstruction = true;
2496 // Look for the next batch of filters.
2500 // If typeinfos matched if and only if equal, then the elements of a filter L
2501 // that occurs later than a filter F could be replaced by the intersection of
2502 // the elements of F and L. In reality two typeinfos can match without being
2503 // equal (for example if one represents a C++ class, and the other some class
2504 // derived from it) so it would be wrong to perform this transform in general.
2505 // However the transform is correct and useful if F is a subset of L. In that
2506 // case L can be replaced by F, and thus removed altogether since repeating a
2507 // filter is pointless. So here we look at all pairs of filters F and L where
2508 // L follows F in the list of clauses, and remove L if every element of F is
2509 // an element of L. This can occur when inlining C++ functions with exception
2511 for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) {
2512 // Examine each filter in turn.
2513 Value *Filter = NewClauses[i];
2514 ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType());
2516 // Not a filter - skip it.
2518 unsigned FElts = FTy->getNumElements();
2519 // Examine each filter following this one. Doing this backwards means that
2520 // we don't have to worry about filters disappearing under us when removed.
2521 for (unsigned j = NewClauses.size() - 1; j != i; --j) {
2522 Value *LFilter = NewClauses[j];
2523 ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType());
2525 // Not a filter - skip it.
2527 // If Filter is a subset of LFilter, i.e. every element of Filter is also
2528 // an element of LFilter, then discard LFilter.
2529 SmallVectorImpl<Constant *>::iterator J = NewClauses.begin() + j;
2530 // If Filter is empty then it is a subset of LFilter.
2533 NewClauses.erase(J);
2534 MakeNewInstruction = true;
2535 // Move on to the next filter.
2538 unsigned LElts = LTy->getNumElements();
2539 // If Filter is longer than LFilter then it cannot be a subset of it.
2541 // Move on to the next filter.
2543 // At this point we know that LFilter has at least one element.
2544 if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros.
2545 // Filter is a subset of LFilter iff Filter contains only zeros (as we
2546 // already know that Filter is not longer than LFilter).
2547 if (isa<ConstantAggregateZero>(Filter)) {
2548 assert(FElts <= LElts && "Should have handled this case earlier!");
2550 NewClauses.erase(J);
2551 MakeNewInstruction = true;
2553 // Move on to the next filter.
2556 ConstantArray *LArray = cast<ConstantArray>(LFilter);
2557 if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros.
2558 // Since Filter is non-empty and contains only zeros, it is a subset of
2559 // LFilter iff LFilter contains a zero.
2560 assert(FElts > 0 && "Should have eliminated the empty filter earlier!");
2561 for (unsigned l = 0; l != LElts; ++l)
2562 if (LArray->getOperand(l)->isNullValue()) {
2563 // LFilter contains a zero - discard it.
2564 NewClauses.erase(J);
2565 MakeNewInstruction = true;
2568 // Move on to the next filter.
2571 // At this point we know that both filters are ConstantArrays. Loop over
2572 // operands to see whether every element of Filter is also an element of
2573 // LFilter. Since filters tend to be short this is probably faster than
2574 // using a method that scales nicely.
2575 ConstantArray *FArray = cast<ConstantArray>(Filter);
2576 bool AllFound = true;
2577 for (unsigned f = 0; f != FElts; ++f) {
2578 Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts();
2580 for (unsigned l = 0; l != LElts; ++l) {
2581 Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts();
2582 if (LTypeInfo == FTypeInfo) {
2592 NewClauses.erase(J);
2593 MakeNewInstruction = true;
2595 // Move on to the next filter.
2599 // If we changed any of the clauses, replace the old landingpad instruction
2601 if (MakeNewInstruction) {
2602 LandingPadInst *NLI = LandingPadInst::Create(LI.getType(),
2603 LI.getPersonalityFn(),
2605 for (unsigned i = 0, e = NewClauses.size(); i != e; ++i)
2606 NLI->addClause(NewClauses[i]);
2607 // A landing pad with no clauses must have the cleanup flag set. It is
2608 // theoretically possible, though highly unlikely, that we eliminated all
2609 // clauses. If so, force the cleanup flag to true.
2610 if (NewClauses.empty())
2612 NLI->setCleanup(CleanupFlag);
2616 // Even if none of the clauses changed, we may nonetheless have understood
2617 // that the cleanup flag is pointless. Clear it if so.
2618 if (LI.isCleanup() != CleanupFlag) {
2619 assert(!CleanupFlag && "Adding a cleanup, not removing one?!");
2620 LI.setCleanup(CleanupFlag);
2630 /// TryToSinkInstruction - Try to move the specified instruction from its
2631 /// current block into the beginning of DestBlock, which can only happen if it's
2632 /// safe to move the instruction past all of the instructions between it and the
2633 /// end of its block.
2634 static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
2635 assert(I->hasOneUse() && "Invariants didn't hold!");
2637 // Cannot move control-flow-involving, volatile loads, vaarg, etc.
2638 if (isa<PHINode>(I) || isa<LandingPadInst>(I) || I->mayHaveSideEffects() ||
2639 isa<TerminatorInst>(I))
2642 // Do not sink alloca instructions out of the entry block.
2643 if (isa<AllocaInst>(I) && I->getParent() ==
2644 &DestBlock->getParent()->getEntryBlock())
2647 // We can only sink load instructions if there is nothing between the load and
2648 // the end of block that could change the value.
2649 if (I->mayReadFromMemory()) {
2650 for (BasicBlock::iterator Scan = I, E = I->getParent()->end();
2652 if (Scan->mayWriteToMemory())
2656 BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt();
2657 I->moveBefore(InsertPos);
2663 /// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
2664 /// all reachable code to the worklist.
2666 /// This has a couple of tricks to make the code faster and more powerful. In
2667 /// particular, we constant fold and DCE instructions as we go, to avoid adding
2668 /// them to the worklist (this significantly speeds up instcombine on code where
2669 /// many instructions are dead or constant). Additionally, if we find a branch
2670 /// whose condition is a known constant, we only visit the reachable successors.
2672 static bool AddReachableCodeToWorklist(BasicBlock *BB,
2673 SmallPtrSetImpl<BasicBlock*> &Visited,
2675 const DataLayout *DL,
2676 const TargetLibraryInfo *TLI) {
2677 bool MadeIRChange = false;
2678 SmallVector<BasicBlock*, 256> Worklist;
2679 Worklist.push_back(BB);
2681 SmallVector<Instruction*, 128> InstrsForInstCombineWorklist;
2682 DenseMap<ConstantExpr*, Constant*> FoldedConstants;
2685 BB = Worklist.pop_back_val();
2687 // We have now visited this block! If we've already been here, ignore it.
2688 if (!Visited.insert(BB).second)
2691 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
2692 Instruction *Inst = BBI++;
2694 // DCE instruction if trivially dead.
2695 if (isInstructionTriviallyDead(Inst, TLI)) {
2697 DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
2698 Inst->eraseFromParent();
2702 // ConstantProp instruction if trivially constant.
2703 if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0)))
2704 if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) {
2705 DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: "
2707 Inst->replaceAllUsesWith(C);
2709 Inst->eraseFromParent();
2714 // See if we can constant fold its operands.
2715 for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end();
2717 ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
2718 if (CE == nullptr) continue;
2720 Constant*& FoldRes = FoldedConstants[CE];
2722 FoldRes = ConstantFoldConstantExpression(CE, DL, TLI);
2726 if (FoldRes != CE) {
2728 MadeIRChange = true;
2733 InstrsForInstCombineWorklist.push_back(Inst);
2736 // Recursively visit successors. If this is a branch or switch on a
2737 // constant, only visit the reachable successor.
2738 TerminatorInst *TI = BB->getTerminator();
2739 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
2740 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
2741 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
2742 BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
2743 Worklist.push_back(ReachableBB);
2746 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
2747 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
2748 // See if this is an explicit destination.
2749 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
2751 if (i.getCaseValue() == Cond) {
2752 BasicBlock *ReachableBB = i.getCaseSuccessor();
2753 Worklist.push_back(ReachableBB);
2757 // Otherwise it is the default destination.
2758 Worklist.push_back(SI->getDefaultDest());
2763 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
2764 Worklist.push_back(TI->getSuccessor(i));
2765 } while (!Worklist.empty());
2767 // Once we've found all of the instructions to add to instcombine's worklist,
2768 // add them in reverse order. This way instcombine will visit from the top
2769 // of the function down. This jives well with the way that it adds all uses
2770 // of instructions to the worklist after doing a transformation, thus avoiding
2771 // some N^2 behavior in pathological cases.
2772 IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
2773 InstrsForInstCombineWorklist.size());
2775 return MadeIRChange;
2778 bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
2779 MadeIRChange = false;
2781 DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
2782 << F.getName() << "\n");
2785 // Do a depth-first traversal of the function, populate the worklist with
2786 // the reachable instructions. Ignore blocks that are not reachable. Keep
2787 // track of which blocks we visit.
2788 SmallPtrSet<BasicBlock*, 64> Visited;
2789 MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, DL,
2792 // Do a quick scan over the function. If we find any blocks that are
2793 // unreachable, remove any instructions inside of them. This prevents
2794 // the instcombine code from having to deal with some bad special cases.
2795 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2796 if (Visited.count(BB)) continue;
2798 // Delete the instructions backwards, as it has a reduced likelihood of
2799 // having to update as many def-use and use-def chains.
2800 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
2801 while (EndInst != BB->begin()) {
2802 // Delete the next to last instruction.
2803 BasicBlock::iterator I = EndInst;
2804 Instruction *Inst = --I;
2805 if (!Inst->use_empty())
2806 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
2807 if (isa<LandingPadInst>(Inst)) {
2811 if (!isa<DbgInfoIntrinsic>(Inst)) {
2813 MadeIRChange = true;
2815 Inst->eraseFromParent();
2820 while (!Worklist.isEmpty()) {
2821 Instruction *I = Worklist.RemoveOne();
2822 if (I == nullptr) continue; // skip null values.
2824 // Check to see if we can DCE the instruction.
2825 if (isInstructionTriviallyDead(I, TLI)) {
2826 DEBUG(dbgs() << "IC: DCE: " << *I << '\n');
2827 EraseInstFromFunction(*I);
2829 MadeIRChange = true;
2833 // Instruction isn't dead, see if we can constant propagate it.
2834 if (!I->use_empty() && isa<Constant>(I->getOperand(0)))
2835 if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) {
2836 DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n');
2838 // Add operands to the worklist.
2839 ReplaceInstUsesWith(*I, C);
2841 EraseInstFromFunction(*I);
2842 MadeIRChange = true;
2846 // See if we can trivially sink this instruction to a successor basic block.
2847 if (I->hasOneUse()) {
2848 BasicBlock *BB = I->getParent();
2849 Instruction *UserInst = cast<Instruction>(*I->user_begin());
2850 BasicBlock *UserParent;
2852 // Get the block the use occurs in.
2853 if (PHINode *PN = dyn_cast<PHINode>(UserInst))
2854 UserParent = PN->getIncomingBlock(*I->use_begin());
2856 UserParent = UserInst->getParent();
2858 if (UserParent != BB) {
2859 bool UserIsSuccessor = false;
2860 // See if the user is one of our successors.
2861 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
2862 if (*SI == UserParent) {
2863 UserIsSuccessor = true;
2867 // If the user is one of our immediate successors, and if that successor
2868 // only has us as a predecessors (we'd have to split the critical edge
2869 // otherwise), we can keep going.
2870 if (UserIsSuccessor && UserParent->getSinglePredecessor()) {
2871 // Okay, the CFG is simple enough, try to sink this instruction.
2872 if (TryToSinkInstruction(I, UserParent)) {
2873 MadeIRChange = true;
2874 // We'll add uses of the sunk instruction below, but since sinking
2875 // can expose opportunities for it's *operands* add them to the
2877 for (Use &U : I->operands())
2878 if (Instruction *OpI = dyn_cast<Instruction>(U.get()))
2885 // Now that we have an instruction, try combining it to simplify it.
2886 Builder->SetInsertPoint(I->getParent(), I);
2887 Builder->SetCurrentDebugLocation(I->getDebugLoc());
2892 DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str(););
2893 DEBUG(dbgs() << "IC: Visiting: " << OrigI << '\n');
2895 if (Instruction *Result = visit(*I)) {
2897 // Should we replace the old instruction with a new one?
2899 DEBUG(dbgs() << "IC: Old = " << *I << '\n'
2900 << " New = " << *Result << '\n');
2902 if (!I->getDebugLoc().isUnknown())
2903 Result->setDebugLoc(I->getDebugLoc());
2904 // Everything uses the new instruction now.
2905 I->replaceAllUsesWith(Result);
2907 // Move the name to the new instruction first.
2908 Result->takeName(I);
2910 // Push the new instruction and any users onto the worklist.
2911 Worklist.Add(Result);
2912 Worklist.AddUsersToWorkList(*Result);
2914 // Insert the new instruction into the basic block...
2915 BasicBlock *InstParent = I->getParent();
2916 BasicBlock::iterator InsertPos = I;
2918 // If we replace a PHI with something that isn't a PHI, fix up the
2920 if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos))
2921 InsertPos = InstParent->getFirstInsertionPt();
2923 InstParent->getInstList().insert(InsertPos, Result);
2925 EraseInstFromFunction(*I);
2928 DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n'
2929 << " New = " << *I << '\n');
2932 // If the instruction was modified, it's possible that it is now dead.
2933 // if so, remove it.
2934 if (isInstructionTriviallyDead(I, TLI)) {
2935 EraseInstFromFunction(*I);
2938 Worklist.AddUsersToWorkList(*I);
2941 MadeIRChange = true;
2946 return MadeIRChange;
2950 class InstCombinerLibCallSimplifier final : public LibCallSimplifier {
2953 InstCombinerLibCallSimplifier(const DataLayout *DL,
2954 const TargetLibraryInfo *TLI,
2956 : LibCallSimplifier(DL, TLI) {
2960 /// replaceAllUsesWith - override so that instruction replacement
2961 /// can be defined in terms of the instruction combiner framework.
2962 void replaceAllUsesWith(Instruction *I, Value *With) const override {
2963 IC->ReplaceInstUsesWith(*I, With);
2968 bool InstCombiner::runOnFunction(Function &F) {
2969 if (skipOptnoneFunction(F))
2972 AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
2973 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
2974 DL = DLP ? &DLP->getDataLayout() : nullptr;
2975 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2976 auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
2977 LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
2978 TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
2981 MinimizeSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
2982 Attribute::MinSize);
2984 /// Builder - This is an IRBuilder that automatically inserts new
2985 /// instructions into the worklist when they are created.
2986 IRBuilder<true, TargetFolder, InstCombineIRInserter> TheBuilder(
2987 F.getContext(), TargetFolder(DL), InstCombineIRInserter(Worklist, AC));
2988 Builder = &TheBuilder;
2990 InstCombinerLibCallSimplifier TheSimplifier(DL, TLI, this);
2991 Simplifier = &TheSimplifier;
2993 bool EverMadeChange = false;
2995 // Lower dbg.declare intrinsics otherwise their value may be clobbered
2997 EverMadeChange = LowerDbgDeclare(F);
2999 // Iterate while there is work to do.
3000 unsigned Iteration = 0;
3001 while (DoOneIteration(F, Iteration++))
3002 EverMadeChange = true;
3005 return EverMadeChange;
3008 FunctionPass *llvm::createInstructionCombiningPass() {
3009 return new InstCombiner();