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 #define DEBUG_TYPE "instcombine"
37 #include "llvm/Transforms/Scalar.h"
38 #include "InstCombine.h"
39 #include "llvm-c/Initialization.h"
40 #include "llvm/ADT/SmallPtrSet.h"
41 #include "llvm/ADT/Statistic.h"
42 #include "llvm/ADT/StringSwitch.h"
43 #include "llvm/Analysis/ConstantFolding.h"
44 #include "llvm/Analysis/InstructionSimplify.h"
45 #include "llvm/Analysis/MemoryBuiltins.h"
46 #include "llvm/IR/CFG.h"
47 #include "llvm/IR/DataLayout.h"
48 #include "llvm/IR/GetElementPtrTypeIterator.h"
49 #include "llvm/IR/IntrinsicInst.h"
50 #include "llvm/IR/PatternMatch.h"
51 #include "llvm/IR/ValueHandle.h"
52 #include "llvm/Support/CommandLine.h"
53 #include "llvm/Support/Debug.h"
54 #include "llvm/Target/TargetLibraryInfo.h"
55 #include "llvm/Transforms/Utils/Local.h"
59 using namespace llvm::PatternMatch;
61 STATISTIC(NumCombined , "Number of insts combined");
62 STATISTIC(NumConstProp, "Number of constant folds");
63 STATISTIC(NumDeadInst , "Number of dead inst eliminated");
64 STATISTIC(NumSunkInst , "Number of instructions sunk");
65 STATISTIC(NumExpand, "Number of expansions");
66 STATISTIC(NumFactor , "Number of factorizations");
67 STATISTIC(NumReassoc , "Number of reassociations");
69 static cl::opt<bool> UnsafeFPShrink("enable-double-float-shrink", cl::Hidden,
71 cl::desc("Enable unsafe double to float "
72 "shrinking for math lib calls"));
74 // Initialization Routines
75 void llvm::initializeInstCombine(PassRegistry &Registry) {
76 initializeInstCombinerPass(Registry);
79 void LLVMInitializeInstCombine(LLVMPassRegistryRef R) {
80 initializeInstCombine(*unwrap(R));
83 char InstCombiner::ID = 0;
84 INITIALIZE_PASS_BEGIN(InstCombiner, "instcombine",
85 "Combine redundant instructions", false, false)
86 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
87 INITIALIZE_PASS_END(InstCombiner, "instcombine",
88 "Combine redundant instructions", false, false)
90 void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
92 AU.addRequired<TargetLibraryInfo>();
96 Value *InstCombiner::EmitGEPOffset(User *GEP) {
97 return llvm::EmitGEPOffset(Builder, *getDataLayout(), GEP);
100 /// ShouldChangeType - Return true if it is desirable to convert a computation
101 /// from 'From' to 'To'. We don't want to convert from a legal to an illegal
102 /// type for example, or from a smaller to a larger illegal type.
103 bool InstCombiner::ShouldChangeType(Type *From, Type *To) const {
104 assert(From->isIntegerTy() && To->isIntegerTy());
106 // If we don't have DL, we don't know if the source/dest are legal.
107 if (!DL) return false;
109 unsigned FromWidth = From->getPrimitiveSizeInBits();
110 unsigned ToWidth = To->getPrimitiveSizeInBits();
111 bool FromLegal = DL->isLegalInteger(FromWidth);
112 bool ToLegal = DL->isLegalInteger(ToWidth);
114 // If this is a legal integer from type, and the result would be an illegal
115 // type, don't do the transformation.
116 if (FromLegal && !ToLegal)
119 // Otherwise, if both are illegal, do not increase the size of the result. We
120 // do allow things like i160 -> i64, but not i64 -> i160.
121 if (!FromLegal && !ToLegal && ToWidth > FromWidth)
127 // Return true, if No Signed Wrap should be maintained for I.
128 // The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C",
129 // where both B and C should be ConstantInts, results in a constant that does
130 // not overflow. This function only handles the Add and Sub opcodes. For
131 // all other opcodes, the function conservatively returns false.
132 static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) {
133 OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I);
134 if (!OBO || !OBO->hasNoSignedWrap()) {
138 // We reason about Add and Sub Only.
139 Instruction::BinaryOps Opcode = I.getOpcode();
140 if (Opcode != Instruction::Add &&
141 Opcode != Instruction::Sub) {
145 ConstantInt *CB = dyn_cast<ConstantInt>(B);
146 ConstantInt *CC = dyn_cast<ConstantInt>(C);
152 const APInt &BVal = CB->getValue();
153 const APInt &CVal = CC->getValue();
154 bool Overflow = false;
156 if (Opcode == Instruction::Add) {
157 BVal.sadd_ov(CVal, Overflow);
159 BVal.ssub_ov(CVal, Overflow);
165 /// Conservatively clears subclassOptionalData after a reassociation or
166 /// commutation. We preserve fast-math flags when applicable as they can be
168 static void ClearSubclassDataAfterReassociation(BinaryOperator &I) {
169 FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I);
171 I.clearSubclassOptionalData();
175 FastMathFlags FMF = I.getFastMathFlags();
176 I.clearSubclassOptionalData();
177 I.setFastMathFlags(FMF);
180 /// SimplifyAssociativeOrCommutative - This performs a few simplifications for
181 /// operators which are associative or commutative:
183 // Commutative operators:
185 // 1. Order operands such that they are listed from right (least complex) to
186 // left (most complex). This puts constants before unary operators before
189 // Associative operators:
191 // 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
192 // 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
194 // Associative and commutative operators:
196 // 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
197 // 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
198 // 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
199 // if C1 and C2 are constants.
201 bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
202 Instruction::BinaryOps Opcode = I.getOpcode();
203 bool Changed = false;
206 // Order operands such that they are listed from right (least complex) to
207 // left (most complex). This puts constants before unary operators before
209 if (I.isCommutative() && getComplexity(I.getOperand(0)) <
210 getComplexity(I.getOperand(1)))
211 Changed = !I.swapOperands();
213 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0));
214 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1));
216 if (I.isAssociative()) {
217 // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies.
218 if (Op0 && Op0->getOpcode() == Opcode) {
219 Value *A = Op0->getOperand(0);
220 Value *B = Op0->getOperand(1);
221 Value *C = I.getOperand(1);
223 // Does "B op C" simplify?
224 if (Value *V = SimplifyBinOp(Opcode, B, C, DL)) {
225 // It simplifies to V. Form "A op V".
228 // Conservatively clear the optional flags, since they may not be
229 // preserved by the reassociation.
230 if (MaintainNoSignedWrap(I, B, C) &&
231 (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) {
232 // Note: this is only valid because SimplifyBinOp doesn't look at
233 // the operands to Op0.
234 I.clearSubclassOptionalData();
235 I.setHasNoSignedWrap(true);
237 ClearSubclassDataAfterReassociation(I);
246 // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies.
247 if (Op1 && Op1->getOpcode() == Opcode) {
248 Value *A = I.getOperand(0);
249 Value *B = Op1->getOperand(0);
250 Value *C = Op1->getOperand(1);
252 // Does "A op B" simplify?
253 if (Value *V = SimplifyBinOp(Opcode, A, B, DL)) {
254 // It simplifies to V. Form "V op C".
257 // Conservatively clear the optional flags, since they may not be
258 // preserved by the reassociation.
259 ClearSubclassDataAfterReassociation(I);
267 if (I.isAssociative() && I.isCommutative()) {
268 // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies.
269 if (Op0 && Op0->getOpcode() == Opcode) {
270 Value *A = Op0->getOperand(0);
271 Value *B = Op0->getOperand(1);
272 Value *C = I.getOperand(1);
274 // Does "C op A" simplify?
275 if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) {
276 // It simplifies to V. Form "V op B".
279 // Conservatively clear the optional flags, since they may not be
280 // preserved by the reassociation.
281 ClearSubclassDataAfterReassociation(I);
288 // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies.
289 if (Op1 && Op1->getOpcode() == Opcode) {
290 Value *A = I.getOperand(0);
291 Value *B = Op1->getOperand(0);
292 Value *C = Op1->getOperand(1);
294 // Does "C op A" simplify?
295 if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) {
296 // It simplifies to V. Form "B op V".
299 // Conservatively clear the optional flags, since they may not be
300 // preserved by the reassociation.
301 ClearSubclassDataAfterReassociation(I);
308 // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)"
309 // if C1 and C2 are constants.
311 Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode &&
312 isa<Constant>(Op0->getOperand(1)) &&
313 isa<Constant>(Op1->getOperand(1)) &&
314 Op0->hasOneUse() && Op1->hasOneUse()) {
315 Value *A = Op0->getOperand(0);
316 Constant *C1 = cast<Constant>(Op0->getOperand(1));
317 Value *B = Op1->getOperand(0);
318 Constant *C2 = cast<Constant>(Op1->getOperand(1));
320 Constant *Folded = ConstantExpr::get(Opcode, C1, C2);
321 BinaryOperator *New = BinaryOperator::Create(Opcode, A, B);
322 if (isa<FPMathOperator>(New)) {
323 FastMathFlags Flags = I.getFastMathFlags();
324 Flags &= Op0->getFastMathFlags();
325 Flags &= Op1->getFastMathFlags();
326 New->setFastMathFlags(Flags);
328 InsertNewInstWith(New, I);
330 I.setOperand(0, New);
331 I.setOperand(1, Folded);
332 // Conservatively clear the optional flags, since they may not be
333 // preserved by the reassociation.
334 ClearSubclassDataAfterReassociation(I);
341 // No further simplifications.
346 /// LeftDistributesOverRight - Whether "X LOp (Y ROp Z)" is always equal to
347 /// "(X LOp Y) ROp (X LOp Z)".
348 static bool LeftDistributesOverRight(Instruction::BinaryOps LOp,
349 Instruction::BinaryOps ROp) {
354 case Instruction::And:
355 // And distributes over Or and Xor.
359 case Instruction::Or:
360 case Instruction::Xor:
364 case Instruction::Mul:
365 // Multiplication distributes over addition and subtraction.
369 case Instruction::Add:
370 case Instruction::Sub:
374 case Instruction::Or:
375 // Or distributes over And.
379 case Instruction::And:
385 /// RightDistributesOverLeft - Whether "(X LOp Y) ROp Z" is always equal to
386 /// "(X ROp Z) LOp (Y ROp Z)".
387 static bool RightDistributesOverLeft(Instruction::BinaryOps LOp,
388 Instruction::BinaryOps ROp) {
389 if (Instruction::isCommutative(ROp))
390 return LeftDistributesOverRight(ROp, LOp);
391 // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z",
392 // but this requires knowing that the addition does not overflow and other
397 /// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
398 /// which some other binary operation distributes over either by factorizing
399 /// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
400 /// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
401 /// a win). Returns the simplified value, or null if it didn't simplify.
402 Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) {
403 Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
404 BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
405 BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
406 Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op
409 if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) {
410 // The instruction has the form "(A op' B) op (C op' D)". Try to factorize
412 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1);
413 Value *C = Op1->getOperand(0), *D = Op1->getOperand(1);
414 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op'
416 // Does "X op' Y" always equal "Y op' X"?
417 bool InnerCommutative = Instruction::isCommutative(InnerOpcode);
419 // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"?
420 if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode))
421 // Does the instruction have the form "(A op' B) op (A op' D)" or, in the
422 // commutative case, "(A op' B) op (C op' A)"?
423 if (A == C || (InnerCommutative && A == D)) {
426 // Consider forming "A op' (B op D)".
427 // If "B op D" simplifies then it can be formed with no cost.
428 Value *V = SimplifyBinOp(TopLevelOpcode, B, D, DL);
429 // If "B op D" doesn't simplify then only go on if both of the existing
430 // operations "A op' B" and "C op' D" will be zapped as no longer used.
431 if (!V && Op0->hasOneUse() && Op1->hasOneUse())
432 V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName());
435 V = Builder->CreateBinOp(InnerOpcode, A, V);
441 // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"?
442 if (RightDistributesOverLeft(TopLevelOpcode, InnerOpcode))
443 // Does the instruction have the form "(A op' B) op (C op' B)" or, in the
444 // commutative case, "(A op' B) op (B op' D)"?
445 if (B == D || (InnerCommutative && B == C)) {
448 // Consider forming "(A op C) op' B".
449 // If "A op C" simplifies then it can be formed with no cost.
450 Value *V = SimplifyBinOp(TopLevelOpcode, A, C, DL);
451 // If "A op C" doesn't simplify then only go on if both of the existing
452 // operations "A op' B" and "C op' D" will be zapped as no longer used.
453 if (!V && Op0->hasOneUse() && Op1->hasOneUse())
454 V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName());
457 V = Builder->CreateBinOp(InnerOpcode, V, B);
465 if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) {
466 // The instruction has the form "(A op' B) op C". See if expanding it out
467 // to "(A op C) op' (B op C)" results in simplifications.
468 Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
469 Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op'
471 // Do "A op C" and "B op C" both simplify?
472 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, DL))
473 if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, DL)) {
474 // They do! Return "L op' R".
476 // If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
477 if ((L == A && R == B) ||
478 (Instruction::isCommutative(InnerOpcode) && L == B && R == A))
480 // Otherwise return "L op' R" if it simplifies.
481 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL))
483 // Otherwise, create a new instruction.
484 C = Builder->CreateBinOp(InnerOpcode, L, R);
490 if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) {
491 // The instruction has the form "A op (B op' C)". See if expanding it out
492 // to "(A op B) op' (A op C)" results in simplifications.
493 Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
494 Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op'
496 // Do "A op B" and "A op C" both simplify?
497 if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, DL))
498 if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, DL)) {
499 // They do! Return "L op' R".
501 // If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
502 if ((L == B && R == C) ||
503 (Instruction::isCommutative(InnerOpcode) && L == C && R == B))
505 // Otherwise return "L op' R" if it simplifies.
506 if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL))
508 // Otherwise, create a new instruction.
509 A = Builder->CreateBinOp(InnerOpcode, L, R);
518 // dyn_castNegVal - Given a 'sub' instruction, return the RHS of the instruction
519 // if the LHS is a constant zero (which is the 'negate' form).
521 Value *InstCombiner::dyn_castNegVal(Value *V) const {
522 if (BinaryOperator::isNeg(V))
523 return BinaryOperator::getNegArgument(V);
525 // Constants can be considered to be negated values if they can be folded.
526 if (ConstantInt *C = dyn_cast<ConstantInt>(V))
527 return ConstantExpr::getNeg(C);
529 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V))
530 if (C->getType()->getElementType()->isIntegerTy())
531 return ConstantExpr::getNeg(C);
536 // dyn_castFNegVal - Given a 'fsub' instruction, return the RHS of the
537 // instruction if the LHS is a constant negative zero (which is the 'negate'
540 Value *InstCombiner::dyn_castFNegVal(Value *V, bool IgnoreZeroSign) const {
541 if (BinaryOperator::isFNeg(V, IgnoreZeroSign))
542 return BinaryOperator::getFNegArgument(V);
544 // Constants can be considered to be negated values if they can be folded.
545 if (ConstantFP *C = dyn_cast<ConstantFP>(V))
546 return ConstantExpr::getFNeg(C);
548 if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V))
549 if (C->getType()->getElementType()->isFloatingPointTy())
550 return ConstantExpr::getFNeg(C);
555 static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO,
557 if (CastInst *CI = dyn_cast<CastInst>(&I)) {
558 return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType());
561 // Figure out if the constant is the left or the right argument.
562 bool ConstIsRHS = isa<Constant>(I.getOperand(1));
563 Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS));
565 if (Constant *SOC = dyn_cast<Constant>(SO)) {
567 return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand);
568 return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC);
571 Value *Op0 = SO, *Op1 = ConstOperand;
575 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) {
576 Value *RI = IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1,
577 SO->getName()+".op");
578 Instruction *FPInst = dyn_cast<Instruction>(RI);
579 if (FPInst && isa<FPMathOperator>(FPInst))
580 FPInst->copyFastMathFlags(BO);
583 if (ICmpInst *CI = dyn_cast<ICmpInst>(&I))
584 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
585 SO->getName()+".cmp");
586 if (FCmpInst *CI = dyn_cast<FCmpInst>(&I))
587 return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1,
588 SO->getName()+".cmp");
589 llvm_unreachable("Unknown binary instruction type!");
592 // FoldOpIntoSelect - Given an instruction with a select as one operand and a
593 // constant as the other operand, try to fold the binary operator into the
594 // select arguments. This also works for Cast instructions, which obviously do
595 // not have a second operand.
596 Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) {
597 // Don't modify shared select instructions
598 if (!SI->hasOneUse()) return 0;
599 Value *TV = SI->getOperand(1);
600 Value *FV = SI->getOperand(2);
602 if (isa<Constant>(TV) || isa<Constant>(FV)) {
603 // Bool selects with constant operands can be folded to logical ops.
604 if (SI->getType()->isIntegerTy(1)) return 0;
606 // If it's a bitcast involving vectors, make sure it has the same number of
607 // elements on both sides.
608 if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) {
609 VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy());
610 VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy());
612 // Verify that either both or neither are vectors.
613 if ((SrcTy == NULL) != (DestTy == NULL)) return 0;
614 // If vectors, verify that they have the same number of elements.
615 if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements())
619 Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this);
620 Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this);
622 return SelectInst::Create(SI->getCondition(),
623 SelectTrueVal, SelectFalseVal);
629 /// FoldOpIntoPhi - Given a binary operator, cast instruction, or select which
630 /// has a PHI node as operand #0, see if we can fold the instruction into the
631 /// PHI (which is only possible if all operands to the PHI are constants).
633 Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) {
634 PHINode *PN = cast<PHINode>(I.getOperand(0));
635 unsigned NumPHIValues = PN->getNumIncomingValues();
636 if (NumPHIValues == 0)
639 // We normally only transform phis with a single use. However, if a PHI has
640 // multiple uses and they are all the same operation, we can fold *all* of the
641 // uses into the PHI.
642 if (!PN->hasOneUse()) {
643 // Walk the use list for the instruction, comparing them to I.
644 for (User *U : PN->users()) {
645 Instruction *UI = cast<Instruction>(U);
646 if (UI != &I && !I.isIdenticalTo(UI))
649 // Otherwise, we can replace *all* users with the new PHI we form.
652 // Check to see if all of the operands of the PHI are simple constants
653 // (constantint/constantfp/undef). If there is one non-constant value,
654 // remember the BB it is in. If there is more than one or if *it* is a PHI,
655 // bail out. We don't do arbitrary constant expressions here because moving
656 // their computation can be expensive without a cost model.
657 BasicBlock *NonConstBB = 0;
658 for (unsigned i = 0; i != NumPHIValues; ++i) {
659 Value *InVal = PN->getIncomingValue(i);
660 if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal))
663 if (isa<PHINode>(InVal)) return 0; // Itself a phi.
664 if (NonConstBB) return 0; // More than one non-const value.
666 NonConstBB = PN->getIncomingBlock(i);
668 // If the InVal is an invoke at the end of the pred block, then we can't
669 // insert a computation after it without breaking the edge.
670 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
671 if (II->getParent() == NonConstBB)
674 // If the incoming non-constant value is in I's block, we will remove one
675 // instruction, but insert another equivalent one, leading to infinite
677 if (NonConstBB == I.getParent())
681 // If there is exactly one non-constant value, we can insert a copy of the
682 // operation in that block. However, if this is a critical edge, we would be
683 // inserting the computation one some other paths (e.g. inside a loop). Only
684 // do this if the pred block is unconditionally branching into the phi block.
685 if (NonConstBB != 0) {
686 BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator());
687 if (!BI || !BI->isUnconditional()) return 0;
690 // Okay, we can do the transformation: create the new PHI node.
691 PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues());
692 InsertNewInstBefore(NewPN, *PN);
695 // If we are going to have to insert a new computation, do so right before the
696 // predecessors terminator.
698 Builder->SetInsertPoint(NonConstBB->getTerminator());
700 // Next, add all of the operands to the PHI.
701 if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
702 // We only currently try to fold the condition of a select when it is a phi,
703 // not the true/false values.
704 Value *TrueV = SI->getTrueValue();
705 Value *FalseV = SI->getFalseValue();
706 BasicBlock *PhiTransBB = PN->getParent();
707 for (unsigned i = 0; i != NumPHIValues; ++i) {
708 BasicBlock *ThisBB = PN->getIncomingBlock(i);
709 Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB);
710 Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB);
712 // Beware of ConstantExpr: it may eventually evaluate to getNullValue,
713 // even if currently isNullValue gives false.
714 Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i));
715 if (InC && !isa<ConstantExpr>(InC))
716 InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
718 InV = Builder->CreateSelect(PN->getIncomingValue(i),
719 TrueVInPred, FalseVInPred, "phitmp");
720 NewPN->addIncoming(InV, ThisBB);
722 } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) {
723 Constant *C = cast<Constant>(I.getOperand(1));
724 for (unsigned i = 0; i != NumPHIValues; ++i) {
726 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
727 InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C);
728 else if (isa<ICmpInst>(CI))
729 InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i),
732 InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i),
734 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
736 } else if (I.getNumOperands() == 2) {
737 Constant *C = cast<Constant>(I.getOperand(1));
738 for (unsigned i = 0; i != NumPHIValues; ++i) {
740 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
741 InV = ConstantExpr::get(I.getOpcode(), InC, C);
743 InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(),
744 PN->getIncomingValue(i), C, "phitmp");
745 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
748 CastInst *CI = cast<CastInst>(&I);
749 Type *RetTy = CI->getType();
750 for (unsigned i = 0; i != NumPHIValues; ++i) {
752 if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)))
753 InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy);
755 InV = Builder->CreateCast(CI->getOpcode(),
756 PN->getIncomingValue(i), I.getType(), "phitmp");
757 NewPN->addIncoming(InV, PN->getIncomingBlock(i));
761 for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) {
762 Instruction *User = cast<Instruction>(*UI++);
763 if (User == &I) continue;
764 ReplaceInstUsesWith(*User, NewPN);
765 EraseInstFromFunction(*User);
767 return ReplaceInstUsesWith(I, NewPN);
770 /// FindElementAtOffset - Given a pointer type and a constant offset, determine
771 /// whether or not there is a sequence of GEP indices into the pointed type that
772 /// will land us at the specified offset. If so, fill them into NewIndices and
773 /// return the resultant element type, otherwise return null.
774 Type *InstCombiner::FindElementAtOffset(Type *PtrTy, int64_t Offset,
775 SmallVectorImpl<Value*> &NewIndices) {
776 assert(PtrTy->isPtrOrPtrVectorTy());
781 Type *Ty = PtrTy->getPointerElementType();
785 // Start with the index over the outer type. Note that the type size
786 // might be zero (even if the offset isn't zero) if the indexed type
787 // is something like [0 x {int, int}]
788 Type *IntPtrTy = DL->getIntPtrType(PtrTy);
789 int64_t FirstIdx = 0;
790 if (int64_t TySize = DL->getTypeAllocSize(Ty)) {
791 FirstIdx = Offset/TySize;
792 Offset -= FirstIdx*TySize;
794 // Handle hosts where % returns negative instead of values [0..TySize).
800 assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset");
803 NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx));
805 // Index into the types. If we fail, set OrigBase to null.
807 // Indexing into tail padding between struct/array elements.
808 if (uint64_t(Offset*8) >= DL->getTypeSizeInBits(Ty))
811 if (StructType *STy = dyn_cast<StructType>(Ty)) {
812 const StructLayout *SL = DL->getStructLayout(STy);
813 assert(Offset < (int64_t)SL->getSizeInBytes() &&
814 "Offset must stay within the indexed type");
816 unsigned Elt = SL->getElementContainingOffset(Offset);
817 NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
820 Offset -= SL->getElementOffset(Elt);
821 Ty = STy->getElementType(Elt);
822 } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
823 uint64_t EltSize = DL->getTypeAllocSize(AT->getElementType());
824 assert(EltSize && "Cannot index into a zero-sized array");
825 NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize));
827 Ty = AT->getElementType();
829 // Otherwise, we can't index into the middle of this atomic type, bail.
837 static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) {
838 // If this GEP has only 0 indices, it is the same pointer as
839 // Src. If Src is not a trivial GEP too, don't combine
841 if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() &&
847 /// Descale - Return a value X such that Val = X * Scale, or null if none. If
848 /// the multiplication is known not to overflow then NoSignedWrap is set.
849 Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) {
850 assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!");
851 assert(cast<IntegerType>(Val->getType())->getBitWidth() ==
852 Scale.getBitWidth() && "Scale not compatible with value!");
854 // If Val is zero or Scale is one then Val = Val * Scale.
855 if (match(Val, m_Zero()) || Scale == 1) {
860 // If Scale is zero then it does not divide Val.
861 if (Scale.isMinValue())
864 // Look through chains of multiplications, searching for a constant that is
865 // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4
866 // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by
867 // a factor of 4 will produce X*(Y*2). The principle of operation is to bore
870 // Val = M1 * X || Analysis starts here and works down
871 // M1 = M2 * Y || Doesn't descend into terms with more
872 // M2 = Z * 4 \/ than one use
874 // Then to modify a term at the bottom:
877 // M1 = Z * Y || Replaced M2 with Z
879 // Then to work back up correcting nsw flags.
881 // Op - the term we are currently analyzing. Starts at Val then drills down.
882 // Replaced with its descaled value before exiting from the drill down loop.
885 // Parent - initially null, but after drilling down notes where Op came from.
886 // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the
887 // 0'th operand of Val.
888 std::pair<Instruction*, unsigned> Parent;
890 // RequireNoSignedWrap - Set if the transform requires a descaling at deeper
891 // levels that doesn't overflow.
892 bool RequireNoSignedWrap = false;
894 // logScale - log base 2 of the scale. Negative if not a power of 2.
895 int32_t logScale = Scale.exactLogBase2();
897 for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down
899 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) {
900 // If Op is a constant divisible by Scale then descale to the quotient.
901 APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth.
902 APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder);
903 if (!Remainder.isMinValue())
904 // Not divisible by Scale.
906 // Replace with the quotient in the parent.
907 Op = ConstantInt::get(CI->getType(), Quotient);
912 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) {
914 if (BO->getOpcode() == Instruction::Mul) {
916 NoSignedWrap = BO->hasNoSignedWrap();
917 if (RequireNoSignedWrap && !NoSignedWrap)
920 // There are three cases for multiplication: multiplication by exactly
921 // the scale, multiplication by a constant different to the scale, and
922 // multiplication by something else.
923 Value *LHS = BO->getOperand(0);
924 Value *RHS = BO->getOperand(1);
926 if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
927 // Multiplication by a constant.
928 if (CI->getValue() == Scale) {
929 // Multiplication by exactly the scale, replace the multiplication
930 // by its left-hand side in the parent.
935 // Otherwise drill down into the constant.
936 if (!Op->hasOneUse())
939 Parent = std::make_pair(BO, 1);
943 // Multiplication by something else. Drill down into the left-hand side
944 // since that's where the reassociate pass puts the good stuff.
945 if (!Op->hasOneUse())
948 Parent = std::make_pair(BO, 0);
952 if (logScale > 0 && BO->getOpcode() == Instruction::Shl &&
953 isa<ConstantInt>(BO->getOperand(1))) {
954 // Multiplication by a power of 2.
955 NoSignedWrap = BO->hasNoSignedWrap();
956 if (RequireNoSignedWrap && !NoSignedWrap)
959 Value *LHS = BO->getOperand(0);
960 int32_t Amt = cast<ConstantInt>(BO->getOperand(1))->
961 getLimitedValue(Scale.getBitWidth());
964 if (Amt == logScale) {
965 // Multiplication by exactly the scale, replace the multiplication
966 // by its left-hand side in the parent.
970 if (Amt < logScale || !Op->hasOneUse())
973 // Multiplication by more than the scale. Reduce the multiplying amount
974 // by the scale in the parent.
975 Parent = std::make_pair(BO, 1);
976 Op = ConstantInt::get(BO->getType(), Amt - logScale);
981 if (!Op->hasOneUse())
984 if (CastInst *Cast = dyn_cast<CastInst>(Op)) {
985 if (Cast->getOpcode() == Instruction::SExt) {
986 // Op is sign-extended from a smaller type, descale in the smaller type.
987 unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
988 APInt SmallScale = Scale.trunc(SmallSize);
989 // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to
990 // descale Op as (sext Y) * Scale. In order to have
991 // sext (Y * SmallScale) = (sext Y) * Scale
992 // some conditions need to hold however: SmallScale must sign-extend to
993 // Scale and the multiplication Y * SmallScale should not overflow.
994 if (SmallScale.sext(Scale.getBitWidth()) != Scale)
995 // SmallScale does not sign-extend to Scale.
997 assert(SmallScale.exactLogBase2() == logScale);
998 // Require that Y * SmallScale must not overflow.
999 RequireNoSignedWrap = true;
1001 // Drill down through the cast.
1002 Parent = std::make_pair(Cast, 0);
1007 if (Cast->getOpcode() == Instruction::Trunc) {
1008 // Op is truncated from a larger type, descale in the larger type.
1009 // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then
1010 // trunc (Y * sext Scale) = (trunc Y) * Scale
1011 // always holds. However (trunc Y) * Scale may overflow even if
1012 // trunc (Y * sext Scale) does not, so nsw flags need to be cleared
1013 // from this point up in the expression (see later).
1014 if (RequireNoSignedWrap)
1017 // Drill down through the cast.
1018 unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits();
1019 Parent = std::make_pair(Cast, 0);
1020 Scale = Scale.sext(LargeSize);
1021 if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits())
1023 assert(Scale.exactLogBase2() == logScale);
1028 // Unsupported expression, bail out.
1032 // We know that we can successfully descale, so from here on we can safely
1033 // modify the IR. Op holds the descaled version of the deepest term in the
1034 // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known
1038 // The expression only had one term.
1041 // Rewrite the parent using the descaled version of its operand.
1042 assert(Parent.first->hasOneUse() && "Drilled down when more than one use!");
1043 assert(Op != Parent.first->getOperand(Parent.second) &&
1044 "Descaling was a no-op?");
1045 Parent.first->setOperand(Parent.second, Op);
1046 Worklist.Add(Parent.first);
1048 // Now work back up the expression correcting nsw flags. The logic is based
1049 // on the following observation: if X * Y is known not to overflow as a signed
1050 // multiplication, and Y is replaced by a value Z with smaller absolute value,
1051 // then X * Z will not overflow as a signed multiplication either. As we work
1052 // our way up, having NoSignedWrap 'true' means that the descaled value at the
1053 // current level has strictly smaller absolute value than the original.
1054 Instruction *Ancestor = Parent.first;
1056 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) {
1057 // If the multiplication wasn't nsw then we can't say anything about the
1058 // value of the descaled multiplication, and we have to clear nsw flags
1059 // from this point on up.
1060 bool OpNoSignedWrap = BO->hasNoSignedWrap();
1061 NoSignedWrap &= OpNoSignedWrap;
1062 if (NoSignedWrap != OpNoSignedWrap) {
1063 BO->setHasNoSignedWrap(NoSignedWrap);
1064 Worklist.Add(Ancestor);
1066 } else if (Ancestor->getOpcode() == Instruction::Trunc) {
1067 // The fact that the descaled input to the trunc has smaller absolute
1068 // value than the original input doesn't tell us anything useful about
1069 // the absolute values of the truncations.
1070 NoSignedWrap = false;
1072 assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) &&
1073 "Failed to keep proper track of nsw flags while drilling down?");
1075 if (Ancestor == Val)
1076 // Got to the top, all done!
1079 // Move up one level in the expression.
1080 assert(Ancestor->hasOneUse() && "Drilled down when more than one use!");
1081 Ancestor = Ancestor->user_back();
1085 Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
1086 SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end());
1088 if (Value *V = SimplifyGEPInst(Ops, DL))
1089 return ReplaceInstUsesWith(GEP, V);
1091 Value *PtrOp = GEP.getOperand(0);
1093 // Eliminate unneeded casts for indices, and replace indices which displace
1094 // by multiples of a zero size type with zero.
1096 bool MadeChange = false;
1097 Type *IntPtrTy = DL->getIntPtrType(GEP.getPointerOperandType());
1099 gep_type_iterator GTI = gep_type_begin(GEP);
1100 for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end();
1101 I != E; ++I, ++GTI) {
1102 // Skip indices into struct types.
1103 SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI);
1104 if (!SeqTy) continue;
1106 // If the element type has zero size then any index over it is equivalent
1107 // to an index of zero, so replace it with zero if it is not zero already.
1108 if (SeqTy->getElementType()->isSized() &&
1109 DL->getTypeAllocSize(SeqTy->getElementType()) == 0)
1110 if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) {
1111 *I = Constant::getNullValue(IntPtrTy);
1115 Type *IndexTy = (*I)->getType();
1116 if (IndexTy != IntPtrTy) {
1117 // If we are using a wider index than needed for this platform, shrink
1118 // it to what we need. If narrower, sign-extend it to what we need.
1119 // This explicit cast can make subsequent optimizations more obvious.
1120 *I = Builder->CreateIntCast(*I, IntPtrTy, true);
1124 if (MadeChange) return &GEP;
1127 // Combine Indices - If the source pointer to this getelementptr instruction
1128 // is a getelementptr instruction, combine the indices of the two
1129 // getelementptr instructions into a single instruction.
1131 if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) {
1132 if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src))
1135 // Note that if our source is a gep chain itself then we wait for that
1136 // chain to be resolved before we perform this transformation. This
1137 // avoids us creating a TON of code in some cases.
1138 if (GEPOperator *SrcGEP =
1139 dyn_cast<GEPOperator>(Src->getOperand(0)))
1140 if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP))
1141 return 0; // Wait until our source is folded to completion.
1143 SmallVector<Value*, 8> Indices;
1145 // Find out whether the last index in the source GEP is a sequential idx.
1146 bool EndsWithSequential = false;
1147 for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src);
1149 EndsWithSequential = !(*I)->isStructTy();
1151 // Can we combine the two pointer arithmetics offsets?
1152 if (EndsWithSequential) {
1153 // Replace: gep (gep %P, long B), long A, ...
1154 // With: T = long A+B; gep %P, T, ...
1157 Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
1158 Value *GO1 = GEP.getOperand(1);
1159 if (SO1 == Constant::getNullValue(SO1->getType())) {
1161 } else if (GO1 == Constant::getNullValue(GO1->getType())) {
1164 // If they aren't the same type, then the input hasn't been processed
1165 // by the loop above yet (which canonicalizes sequential index types to
1166 // intptr_t). Just avoid transforming this until the input has been
1168 if (SO1->getType() != GO1->getType())
1170 Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum");
1173 // Update the GEP in place if possible.
1174 if (Src->getNumOperands() == 2) {
1175 GEP.setOperand(0, Src->getOperand(0));
1176 GEP.setOperand(1, Sum);
1179 Indices.append(Src->op_begin()+1, Src->op_end()-1);
1180 Indices.push_back(Sum);
1181 Indices.append(GEP.op_begin()+2, GEP.op_end());
1182 } else if (isa<Constant>(*GEP.idx_begin()) &&
1183 cast<Constant>(*GEP.idx_begin())->isNullValue() &&
1184 Src->getNumOperands() != 1) {
1185 // Otherwise we can do the fold if the first index of the GEP is a zero
1186 Indices.append(Src->op_begin()+1, Src->op_end());
1187 Indices.append(GEP.idx_begin()+1, GEP.idx_end());
1190 if (!Indices.empty())
1191 return (GEP.isInBounds() && Src->isInBounds()) ?
1192 GetElementPtrInst::CreateInBounds(Src->getOperand(0), Indices,
1194 GetElementPtrInst::Create(Src->getOperand(0), Indices, GEP.getName());
1197 // Canonicalize (gep i8* X, -(ptrtoint Y)) to (sub (ptrtoint X), (ptrtoint Y))
1198 // The GEP pattern is emitted by the SCEV expander for certain kinds of
1199 // pointer arithmetic.
1200 if (DL && GEP.getNumIndices() == 1 &&
1201 match(GEP.getOperand(1), m_Neg(m_PtrToInt(m_Value())))) {
1202 unsigned AS = GEP.getPointerAddressSpace();
1203 if (GEP.getType() == Builder->getInt8PtrTy(AS) &&
1204 GEP.getOperand(1)->getType()->getScalarSizeInBits() ==
1205 DL->getPointerSizeInBits(AS)) {
1206 Operator *Index = cast<Operator>(GEP.getOperand(1));
1207 Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType());
1208 Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1));
1209 return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType());
1213 // Handle gep(bitcast x) and gep(gep x, 0, 0, 0).
1214 Value *StrippedPtr = PtrOp->stripPointerCasts();
1215 PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType());
1217 // We do not handle pointer-vector geps here.
1221 if (StrippedPtr != PtrOp) {
1222 bool HasZeroPointerIndex = false;
1223 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1)))
1224 HasZeroPointerIndex = C->isZero();
1226 // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ...
1227 // into : GEP [10 x i8]* X, i32 0, ...
1229 // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ...
1230 // into : GEP i8* X, ...
1232 // This occurs when the program declares an array extern like "int X[];"
1233 if (HasZeroPointerIndex) {
1234 PointerType *CPTy = cast<PointerType>(PtrOp->getType());
1235 if (ArrayType *CATy =
1236 dyn_cast<ArrayType>(CPTy->getElementType())) {
1237 // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ?
1238 if (CATy->getElementType() == StrippedPtrTy->getElementType()) {
1239 // -> GEP i8* X, ...
1240 SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end());
1241 GetElementPtrInst *Res =
1242 GetElementPtrInst::Create(StrippedPtr, Idx, GEP.getName());
1243 Res->setIsInBounds(GEP.isInBounds());
1247 if (ArrayType *XATy =
1248 dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){
1249 // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ?
1250 if (CATy->getElementType() == XATy->getElementType()) {
1251 // -> GEP [10 x i8]* X, i32 0, ...
1252 // At this point, we know that the cast source type is a pointer
1253 // to an array of the same type as the destination pointer
1254 // array. Because the array type is never stepped over (there
1255 // is a leading zero) we can fold the cast into this GEP.
1256 GEP.setOperand(0, StrippedPtr);
1261 } else if (GEP.getNumOperands() == 2) {
1262 // Transform things like:
1263 // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V
1264 // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast
1265 Type *SrcElTy = StrippedPtrTy->getElementType();
1266 Type *ResElTy = PtrOp->getType()->getPointerElementType();
1267 if (DL && SrcElTy->isArrayTy() &&
1268 DL->getTypeAllocSize(SrcElTy->getArrayElementType()) ==
1269 DL->getTypeAllocSize(ResElTy)) {
1270 Type *IdxType = DL->getIntPtrType(GEP.getType());
1271 Value *Idx[2] = { Constant::getNullValue(IdxType), GEP.getOperand(1) };
1272 Value *NewGEP = GEP.isInBounds() ?
1273 Builder->CreateInBoundsGEP(StrippedPtr, Idx, GEP.getName()) :
1274 Builder->CreateGEP(StrippedPtr, Idx, GEP.getName());
1276 // V and GEP are both pointer types --> BitCast
1277 if (StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace())
1278 return new BitCastInst(NewGEP, GEP.getType());
1279 return new AddrSpaceCastInst(NewGEP, GEP.getType());
1282 // Transform things like:
1283 // %V = mul i64 %N, 4
1284 // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
1285 // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast
1286 if (DL && ResElTy->isSized() && SrcElTy->isSized()) {
1287 // Check that changing the type amounts to dividing the index by a scale
1289 uint64_t ResSize = DL->getTypeAllocSize(ResElTy);
1290 uint64_t SrcSize = DL->getTypeAllocSize(SrcElTy);
1291 if (ResSize && SrcSize % ResSize == 0) {
1292 Value *Idx = GEP.getOperand(1);
1293 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
1294 uint64_t Scale = SrcSize / ResSize;
1296 // Earlier transforms ensure that the index has type IntPtrType, which
1297 // considerably simplifies the logic by eliminating implicit casts.
1298 assert(Idx->getType() == DL->getIntPtrType(GEP.getType()) &&
1299 "Index not cast to pointer width?");
1302 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
1303 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
1304 // If the multiplication NewIdx * Scale may overflow then the new
1305 // GEP may not be "inbounds".
1306 Value *NewGEP = GEP.isInBounds() && NSW ?
1307 Builder->CreateInBoundsGEP(StrippedPtr, NewIdx, GEP.getName()) :
1308 Builder->CreateGEP(StrippedPtr, NewIdx, GEP.getName());
1310 // The NewGEP must be pointer typed, so must the old one -> BitCast
1311 if (StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace())
1312 return new BitCastInst(NewGEP, GEP.getType());
1313 return new AddrSpaceCastInst(NewGEP, GEP.getType());
1318 // Similarly, transform things like:
1319 // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp
1320 // (where tmp = 8*tmp2) into:
1321 // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast
1322 if (DL && ResElTy->isSized() && SrcElTy->isSized() &&
1323 SrcElTy->isArrayTy()) {
1324 // Check that changing to the array element type amounts to dividing the
1325 // index by a scale factor.
1326 uint64_t ResSize = DL->getTypeAllocSize(ResElTy);
1327 uint64_t ArrayEltSize
1328 = DL->getTypeAllocSize(SrcElTy->getArrayElementType());
1329 if (ResSize && ArrayEltSize % ResSize == 0) {
1330 Value *Idx = GEP.getOperand(1);
1331 unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits();
1332 uint64_t Scale = ArrayEltSize / ResSize;
1334 // Earlier transforms ensure that the index has type IntPtrType, which
1335 // considerably simplifies the logic by eliminating implicit casts.
1336 assert(Idx->getType() == DL->getIntPtrType(GEP.getType()) &&
1337 "Index not cast to pointer width?");
1340 if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) {
1341 // Successfully decomposed Idx as NewIdx * Scale, form a new GEP.
1342 // If the multiplication NewIdx * Scale may overflow then the new
1343 // GEP may not be "inbounds".
1345 Constant::getNullValue(DL->getIntPtrType(GEP.getType())),
1349 Value *NewGEP = GEP.isInBounds() && NSW ?
1350 Builder->CreateInBoundsGEP(StrippedPtr, Off, GEP.getName()) :
1351 Builder->CreateGEP(StrippedPtr, Off, GEP.getName());
1352 // The NewGEP must be pointer typed, so must the old one -> BitCast
1353 if (StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace())
1354 return new BitCastInst(NewGEP, GEP.getType());
1355 return new AddrSpaceCastInst(NewGEP, GEP.getType());
1365 /// See if we can simplify:
1366 /// X = bitcast A* to B*
1367 /// Y = gep X, <...constant indices...>
1368 /// into a gep of the original struct. This is important for SROA and alias
1369 /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged.
1370 if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) {
1371 Value *Operand = BCI->getOperand(0);
1372 PointerType *OpType = cast<PointerType>(Operand->getType());
1373 unsigned OffsetBits = DL->getPointerTypeSizeInBits(OpType);
1374 APInt Offset(OffsetBits, 0);
1375 if (!isa<BitCastInst>(Operand) &&
1376 GEP.accumulateConstantOffset(*DL, Offset) &&
1377 StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) {
1379 // If this GEP instruction doesn't move the pointer, just replace the GEP
1380 // with a bitcast of the real input to the dest type.
1382 // If the bitcast is of an allocation, and the allocation will be
1383 // converted to match the type of the cast, don't touch this.
1384 if (isa<AllocaInst>(Operand) || isAllocationFn(Operand, TLI)) {
1385 // See if the bitcast simplifies, if so, don't nuke this GEP yet.
1386 if (Instruction *I = visitBitCast(*BCI)) {
1389 BCI->getParent()->getInstList().insert(BCI, I);
1390 ReplaceInstUsesWith(*BCI, I);
1395 return new BitCastInst(Operand, GEP.getType());
1398 // Otherwise, if the offset is non-zero, we need to find out if there is a
1399 // field at Offset in 'A's type. If so, we can pull the cast through the
1401 SmallVector<Value*, 8> NewIndices;
1402 if (FindElementAtOffset(OpType, Offset.getSExtValue(), NewIndices)) {
1403 Value *NGEP = GEP.isInBounds() ?
1404 Builder->CreateInBoundsGEP(Operand, NewIndices) :
1405 Builder->CreateGEP(Operand, NewIndices);
1407 if (NGEP->getType() == GEP.getType())
1408 return ReplaceInstUsesWith(GEP, NGEP);
1409 NGEP->takeName(&GEP);
1410 return new BitCastInst(NGEP, GEP.getType());
1419 isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users,
1420 const TargetLibraryInfo *TLI) {
1421 SmallVector<Instruction*, 4> Worklist;
1422 Worklist.push_back(AI);
1425 Instruction *PI = Worklist.pop_back_val();
1426 for (User *U : PI->users()) {
1427 Instruction *I = cast<Instruction>(U);
1428 switch (I->getOpcode()) {
1430 // Give up the moment we see something we can't handle.
1433 case Instruction::BitCast:
1434 case Instruction::GetElementPtr:
1436 Worklist.push_back(I);
1439 case Instruction::ICmp: {
1440 ICmpInst *ICI = cast<ICmpInst>(I);
1441 // We can fold eq/ne comparisons with null to false/true, respectively.
1442 if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1)))
1448 case Instruction::Call:
1449 // Ignore no-op and store intrinsics.
1450 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1451 switch (II->getIntrinsicID()) {
1455 case Intrinsic::memmove:
1456 case Intrinsic::memcpy:
1457 case Intrinsic::memset: {
1458 MemIntrinsic *MI = cast<MemIntrinsic>(II);
1459 if (MI->isVolatile() || MI->getRawDest() != PI)
1463 case Intrinsic::dbg_declare:
1464 case Intrinsic::dbg_value:
1465 case Intrinsic::invariant_start:
1466 case Intrinsic::invariant_end:
1467 case Intrinsic::lifetime_start:
1468 case Intrinsic::lifetime_end:
1469 case Intrinsic::objectsize:
1475 if (isFreeCall(I, TLI)) {
1481 case Instruction::Store: {
1482 StoreInst *SI = cast<StoreInst>(I);
1483 if (SI->isVolatile() || SI->getPointerOperand() != PI)
1489 llvm_unreachable("missing a return?");
1491 } while (!Worklist.empty());
1495 Instruction *InstCombiner::visitAllocSite(Instruction &MI) {
1496 // If we have a malloc call which is only used in any amount of comparisons
1497 // to null and free calls, delete the calls and replace the comparisons with
1498 // true or false as appropriate.
1499 SmallVector<WeakVH, 64> Users;
1500 if (isAllocSiteRemovable(&MI, Users, TLI)) {
1501 for (unsigned i = 0, e = Users.size(); i != e; ++i) {
1502 Instruction *I = cast_or_null<Instruction>(&*Users[i]);
1505 if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
1506 ReplaceInstUsesWith(*C,
1507 ConstantInt::get(Type::getInt1Ty(C->getContext()),
1508 C->isFalseWhenEqual()));
1509 } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
1510 ReplaceInstUsesWith(*I, UndefValue::get(I->getType()));
1511 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
1512 if (II->getIntrinsicID() == Intrinsic::objectsize) {
1513 ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1));
1514 uint64_t DontKnow = CI->isZero() ? -1ULL : 0;
1515 ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow));
1518 EraseInstFromFunction(*I);
1521 if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) {
1522 // Replace invoke with a NOP intrinsic to maintain the original CFG
1523 Module *M = II->getParent()->getParent()->getParent();
1524 Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing);
1525 InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(),
1526 None, "", II->getParent());
1528 return EraseInstFromFunction(MI);
1533 /// \brief Move the call to free before a NULL test.
1535 /// Check if this free is accessed after its argument has been test
1536 /// against NULL (property 0).
1537 /// If yes, it is legal to move this call in its predecessor block.
1539 /// The move is performed only if the block containing the call to free
1540 /// will be removed, i.e.:
1541 /// 1. it has only one predecessor P, and P has two successors
1542 /// 2. it contains the call and an unconditional branch
1543 /// 3. its successor is the same as its predecessor's successor
1545 /// The profitability is out-of concern here and this function should
1546 /// be called only if the caller knows this transformation would be
1547 /// profitable (e.g., for code size).
1548 static Instruction *
1549 tryToMoveFreeBeforeNullTest(CallInst &FI) {
1550 Value *Op = FI.getArgOperand(0);
1551 BasicBlock *FreeInstrBB = FI.getParent();
1552 BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor();
1554 // Validate part of constraint #1: Only one predecessor
1555 // FIXME: We can extend the number of predecessor, but in that case, we
1556 // would duplicate the call to free in each predecessor and it may
1557 // not be profitable even for code size.
1561 // Validate constraint #2: Does this block contains only the call to
1562 // free and an unconditional branch?
1563 // FIXME: We could check if we can speculate everything in the
1564 // predecessor block
1565 if (FreeInstrBB->size() != 2)
1568 if (!match(FreeInstrBB->getTerminator(), m_UnconditionalBr(SuccBB)))
1571 // Validate the rest of constraint #1 by matching on the pred branch.
1572 TerminatorInst *TI = PredBB->getTerminator();
1573 BasicBlock *TrueBB, *FalseBB;
1574 ICmpInst::Predicate Pred;
1575 if (!match(TI, m_Br(m_ICmp(Pred, m_Specific(Op), m_Zero()), TrueBB, FalseBB)))
1577 if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE)
1580 // Validate constraint #3: Ensure the null case just falls through.
1581 if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB))
1583 assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) &&
1584 "Broken CFG: missing edge from predecessor to successor");
1591 Instruction *InstCombiner::visitFree(CallInst &FI) {
1592 Value *Op = FI.getArgOperand(0);
1594 // free undef -> unreachable.
1595 if (isa<UndefValue>(Op)) {
1596 // Insert a new store to null because we cannot modify the CFG here.
1597 Builder->CreateStore(ConstantInt::getTrue(FI.getContext()),
1598 UndefValue::get(Type::getInt1PtrTy(FI.getContext())));
1599 return EraseInstFromFunction(FI);
1602 // If we have 'free null' delete the instruction. This can happen in stl code
1603 // when lots of inlining happens.
1604 if (isa<ConstantPointerNull>(Op))
1605 return EraseInstFromFunction(FI);
1607 // If we optimize for code size, try to move the call to free before the null
1608 // test so that simplify cfg can remove the empty block and dead code
1609 // elimination the branch. I.e., helps to turn something like:
1610 // if (foo) free(foo);
1614 if (Instruction *I = tryToMoveFreeBeforeNullTest(FI))
1622 Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
1623 // Change br (not X), label True, label False to: br X, label False, True
1625 BasicBlock *TrueDest;
1626 BasicBlock *FalseDest;
1627 if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) &&
1628 !isa<Constant>(X)) {
1629 // Swap Destinations and condition...
1631 BI.swapSuccessors();
1635 // Canonicalize fcmp_one -> fcmp_oeq
1636 FCmpInst::Predicate FPred; Value *Y;
1637 if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)),
1638 TrueDest, FalseDest)) &&
1639 BI.getCondition()->hasOneUse())
1640 if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE ||
1641 FPred == FCmpInst::FCMP_OGE) {
1642 FCmpInst *Cond = cast<FCmpInst>(BI.getCondition());
1643 Cond->setPredicate(FCmpInst::getInversePredicate(FPred));
1645 // Swap Destinations and condition.
1646 BI.swapSuccessors();
1651 // Canonicalize icmp_ne -> icmp_eq
1652 ICmpInst::Predicate IPred;
1653 if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)),
1654 TrueDest, FalseDest)) &&
1655 BI.getCondition()->hasOneUse())
1656 if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE ||
1657 IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE ||
1658 IPred == ICmpInst::ICMP_SGE) {
1659 ICmpInst *Cond = cast<ICmpInst>(BI.getCondition());
1660 Cond->setPredicate(ICmpInst::getInversePredicate(IPred));
1661 // Swap Destinations and condition.
1662 BI.swapSuccessors();
1670 Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
1671 Value *Cond = SI.getCondition();
1672 if (Instruction *I = dyn_cast<Instruction>(Cond)) {
1673 if (I->getOpcode() == Instruction::Add)
1674 if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
1675 // change 'switch (X+4) case 1:' into 'switch (X) case -3'
1676 // Skip the first item since that's the default case.
1677 for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end();
1679 ConstantInt* CaseVal = i.getCaseValue();
1680 Constant* NewCaseVal = ConstantExpr::getSub(cast<Constant>(CaseVal),
1682 assert(isa<ConstantInt>(NewCaseVal) &&
1683 "Result of expression should be constant");
1684 i.setValue(cast<ConstantInt>(NewCaseVal));
1686 SI.setCondition(I->getOperand(0));
1694 Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) {
1695 Value *Agg = EV.getAggregateOperand();
1697 if (!EV.hasIndices())
1698 return ReplaceInstUsesWith(EV, Agg);
1700 if (Constant *C = dyn_cast<Constant>(Agg)) {
1701 if (Constant *C2 = C->getAggregateElement(*EV.idx_begin())) {
1702 if (EV.getNumIndices() == 0)
1703 return ReplaceInstUsesWith(EV, C2);
1704 // Extract the remaining indices out of the constant indexed by the
1706 return ExtractValueInst::Create(C2, EV.getIndices().slice(1));
1708 return 0; // Can't handle other constants
1711 if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
1712 // We're extracting from an insertvalue instruction, compare the indices
1713 const unsigned *exti, *exte, *insi, *inse;
1714 for (exti = EV.idx_begin(), insi = IV->idx_begin(),
1715 exte = EV.idx_end(), inse = IV->idx_end();
1716 exti != exte && insi != inse;
1719 // The insert and extract both reference distinctly different elements.
1720 // This means the extract is not influenced by the insert, and we can
1721 // replace the aggregate operand of the extract with the aggregate
1722 // operand of the insert. i.e., replace
1723 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
1724 // %E = extractvalue { i32, { i32 } } %I, 0
1726 // %E = extractvalue { i32, { i32 } } %A, 0
1727 return ExtractValueInst::Create(IV->getAggregateOperand(),
1730 if (exti == exte && insi == inse)
1731 // Both iterators are at the end: Index lists are identical. Replace
1732 // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
1733 // %C = extractvalue { i32, { i32 } } %B, 1, 0
1735 return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand());
1737 // The extract list is a prefix of the insert list. i.e. replace
1738 // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
1739 // %E = extractvalue { i32, { i32 } } %I, 1
1741 // %X = extractvalue { i32, { i32 } } %A, 1
1742 // %E = insertvalue { i32 } %X, i32 42, 0
1743 // by switching the order of the insert and extract (though the
1744 // insertvalue should be left in, since it may have other uses).
1745 Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(),
1747 return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
1748 makeArrayRef(insi, inse));
1751 // The insert list is a prefix of the extract list
1752 // We can simply remove the common indices from the extract and make it
1753 // operate on the inserted value instead of the insertvalue result.
1755 // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
1756 // %E = extractvalue { i32, { i32 } } %I, 1, 0
1758 // %E extractvalue { i32 } { i32 42 }, 0
1759 return ExtractValueInst::Create(IV->getInsertedValueOperand(),
1760 makeArrayRef(exti, exte));
1762 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) {
1763 // We're extracting from an intrinsic, see if we're the only user, which
1764 // allows us to simplify multiple result intrinsics to simpler things that
1765 // just get one value.
1766 if (II->hasOneUse()) {
1767 // Check if we're grabbing the overflow bit or the result of a 'with
1768 // overflow' intrinsic. If it's the latter we can remove the intrinsic
1769 // and replace it with a traditional binary instruction.
1770 switch (II->getIntrinsicID()) {
1771 case Intrinsic::uadd_with_overflow:
1772 case Intrinsic::sadd_with_overflow:
1773 if (*EV.idx_begin() == 0) { // Normal result.
1774 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
1775 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
1776 EraseInstFromFunction(*II);
1777 return BinaryOperator::CreateAdd(LHS, RHS);
1780 // If the normal result of the add is dead, and the RHS is a constant,
1781 // we can transform this into a range comparison.
1782 // overflow = uadd a, -4 --> overflow = icmp ugt a, 3
1783 if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow)
1784 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1)))
1785 return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0),
1786 ConstantExpr::getNot(CI));
1788 case Intrinsic::usub_with_overflow:
1789 case Intrinsic::ssub_with_overflow:
1790 if (*EV.idx_begin() == 0) { // Normal result.
1791 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
1792 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
1793 EraseInstFromFunction(*II);
1794 return BinaryOperator::CreateSub(LHS, RHS);
1797 case Intrinsic::umul_with_overflow:
1798 case Intrinsic::smul_with_overflow:
1799 if (*EV.idx_begin() == 0) { // Normal result.
1800 Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
1801 ReplaceInstUsesWith(*II, UndefValue::get(II->getType()));
1802 EraseInstFromFunction(*II);
1803 return BinaryOperator::CreateMul(LHS, RHS);
1811 if (LoadInst *L = dyn_cast<LoadInst>(Agg))
1812 // If the (non-volatile) load only has one use, we can rewrite this to a
1813 // load from a GEP. This reduces the size of the load.
1814 // FIXME: If a load is used only by extractvalue instructions then this
1815 // could be done regardless of having multiple uses.
1816 if (L->isSimple() && L->hasOneUse()) {
1817 // extractvalue has integer indices, getelementptr has Value*s. Convert.
1818 SmallVector<Value*, 4> Indices;
1819 // Prefix an i32 0 since we need the first element.
1820 Indices.push_back(Builder->getInt32(0));
1821 for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end();
1823 Indices.push_back(Builder->getInt32(*I));
1825 // We need to insert these at the location of the old load, not at that of
1826 // the extractvalue.
1827 Builder->SetInsertPoint(L->getParent(), L);
1828 Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), Indices);
1829 // Returning the load directly will cause the main loop to insert it in
1830 // the wrong spot, so use ReplaceInstUsesWith().
1831 return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP));
1833 // We could simplify extracts from other values. Note that nested extracts may
1834 // already be simplified implicitly by the above: extract (extract (insert) )
1835 // will be translated into extract ( insert ( extract ) ) first and then just
1836 // the value inserted, if appropriate. Similarly for extracts from single-use
1837 // loads: extract (extract (load)) will be translated to extract (load (gep))
1838 // and if again single-use then via load (gep (gep)) to load (gep).
1839 // However, double extracts from e.g. function arguments or return values
1840 // aren't handled yet.
1844 enum Personality_Type {
1845 Unknown_Personality,
1846 GNU_Ada_Personality,
1847 GNU_CXX_Personality,
1848 GNU_ObjC_Personality
1851 /// RecognizePersonality - See if the given exception handling personality
1852 /// function is one that we understand. If so, return a description of it;
1853 /// otherwise return Unknown_Personality.
1854 static Personality_Type RecognizePersonality(Value *Pers) {
1855 Function *F = dyn_cast<Function>(Pers->stripPointerCasts());
1857 return Unknown_Personality;
1858 return StringSwitch<Personality_Type>(F->getName())
1859 .Case("__gnat_eh_personality", GNU_Ada_Personality)
1860 .Case("__gxx_personality_v0", GNU_CXX_Personality)
1861 .Case("__objc_personality_v0", GNU_ObjC_Personality)
1862 .Default(Unknown_Personality);
1865 /// isCatchAll - Return 'true' if the given typeinfo will match anything.
1866 static bool isCatchAll(Personality_Type Personality, Constant *TypeInfo) {
1867 switch (Personality) {
1868 case Unknown_Personality:
1870 case GNU_Ada_Personality:
1871 // While __gnat_all_others_value will match any Ada exception, it doesn't
1872 // match foreign exceptions (or didn't, before gcc-4.7).
1874 case GNU_CXX_Personality:
1875 case GNU_ObjC_Personality:
1876 return TypeInfo->isNullValue();
1878 llvm_unreachable("Unknown personality!");
1881 static bool shorter_filter(const Value *LHS, const Value *RHS) {
1883 cast<ArrayType>(LHS->getType())->getNumElements()
1885 cast<ArrayType>(RHS->getType())->getNumElements();
1888 Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) {
1889 // The logic here should be correct for any real-world personality function.
1890 // However if that turns out not to be true, the offending logic can always
1891 // be conditioned on the personality function, like the catch-all logic is.
1892 Personality_Type Personality = RecognizePersonality(LI.getPersonalityFn());
1894 // Simplify the list of clauses, eg by removing repeated catch clauses
1895 // (these are often created by inlining).
1896 bool MakeNewInstruction = false; // If true, recreate using the following:
1897 SmallVector<Value *, 16> NewClauses; // - Clauses for the new instruction;
1898 bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup.
1900 SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already.
1901 for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) {
1902 bool isLastClause = i + 1 == e;
1903 if (LI.isCatch(i)) {
1905 Value *CatchClause = LI.getClause(i);
1906 Constant *TypeInfo = cast<Constant>(CatchClause->stripPointerCasts());
1908 // If we already saw this clause, there is no point in having a second
1910 if (AlreadyCaught.insert(TypeInfo)) {
1911 // This catch clause was not already seen.
1912 NewClauses.push_back(CatchClause);
1914 // Repeated catch clause - drop the redundant copy.
1915 MakeNewInstruction = true;
1918 // If this is a catch-all then there is no point in keeping any following
1919 // clauses or marking the landingpad as having a cleanup.
1920 if (isCatchAll(Personality, TypeInfo)) {
1922 MakeNewInstruction = true;
1923 CleanupFlag = false;
1927 // A filter clause. If any of the filter elements were already caught
1928 // then they can be dropped from the filter. It is tempting to try to
1929 // exploit the filter further by saying that any typeinfo that does not
1930 // occur in the filter can't be caught later (and thus can be dropped).
1931 // However this would be wrong, since typeinfos can match without being
1932 // equal (for example if one represents a C++ class, and the other some
1933 // class derived from it).
1934 assert(LI.isFilter(i) && "Unsupported landingpad clause!");
1935 Value *FilterClause = LI.getClause(i);
1936 ArrayType *FilterType = cast<ArrayType>(FilterClause->getType());
1937 unsigned NumTypeInfos = FilterType->getNumElements();
1939 // An empty filter catches everything, so there is no point in keeping any
1940 // following clauses or marking the landingpad as having a cleanup. By
1941 // dealing with this case here the following code is made a bit simpler.
1942 if (!NumTypeInfos) {
1943 NewClauses.push_back(FilterClause);
1945 MakeNewInstruction = true;
1946 CleanupFlag = false;
1950 bool MakeNewFilter = false; // If true, make a new filter.
1951 SmallVector<Constant *, 16> NewFilterElts; // New elements.
1952 if (isa<ConstantAggregateZero>(FilterClause)) {
1953 // Not an empty filter - it contains at least one null typeinfo.
1954 assert(NumTypeInfos > 0 && "Should have handled empty filter already!");
1955 Constant *TypeInfo =
1956 Constant::getNullValue(FilterType->getElementType());
1957 // If this typeinfo is a catch-all then the filter can never match.
1958 if (isCatchAll(Personality, TypeInfo)) {
1959 // Throw the filter away.
1960 MakeNewInstruction = true;
1964 // There is no point in having multiple copies of this typeinfo, so
1965 // discard all but the first copy if there is more than one.
1966 NewFilterElts.push_back(TypeInfo);
1967 if (NumTypeInfos > 1)
1968 MakeNewFilter = true;
1970 ConstantArray *Filter = cast<ConstantArray>(FilterClause);
1971 SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements.
1972 NewFilterElts.reserve(NumTypeInfos);
1974 // Remove any filter elements that were already caught or that already
1975 // occurred in the filter. While there, see if any of the elements are
1976 // catch-alls. If so, the filter can be discarded.
1977 bool SawCatchAll = false;
1978 for (unsigned j = 0; j != NumTypeInfos; ++j) {
1979 Value *Elt = Filter->getOperand(j);
1980 Constant *TypeInfo = cast<Constant>(Elt->stripPointerCasts());
1981 if (isCatchAll(Personality, TypeInfo)) {
1982 // This element is a catch-all. Bail out, noting this fact.
1986 if (AlreadyCaught.count(TypeInfo))
1987 // Already caught by an earlier clause, so having it in the filter
1990 // There is no point in having multiple copies of the same typeinfo in
1991 // a filter, so only add it if we didn't already.
1992 if (SeenInFilter.insert(TypeInfo))
1993 NewFilterElts.push_back(cast<Constant>(Elt));
1995 // A filter containing a catch-all cannot match anything by definition.
1997 // Throw the filter away.
1998 MakeNewInstruction = true;
2002 // If we dropped something from the filter, make a new one.
2003 if (NewFilterElts.size() < NumTypeInfos)
2004 MakeNewFilter = true;
2006 if (MakeNewFilter) {
2007 FilterType = ArrayType::get(FilterType->getElementType(),
2008 NewFilterElts.size());
2009 FilterClause = ConstantArray::get(FilterType, NewFilterElts);
2010 MakeNewInstruction = true;
2013 NewClauses.push_back(FilterClause);
2015 // If the new filter is empty then it will catch everything so there is
2016 // no point in keeping any following clauses or marking the landingpad
2017 // as having a cleanup. The case of the original filter being empty was
2018 // already handled above.
2019 if (MakeNewFilter && !NewFilterElts.size()) {
2020 assert(MakeNewInstruction && "New filter but not a new instruction!");
2021 CleanupFlag = false;
2027 // If several filters occur in a row then reorder them so that the shortest
2028 // filters come first (those with the smallest number of elements). This is
2029 // advantageous because shorter filters are more likely to match, speeding up
2030 // unwinding, but mostly because it increases the effectiveness of the other
2031 // filter optimizations below.
2032 for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) {
2034 // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters.
2035 for (j = i; j != e; ++j)
2036 if (!isa<ArrayType>(NewClauses[j]->getType()))
2039 // Check whether the filters are already sorted by length. We need to know
2040 // if sorting them is actually going to do anything so that we only make a
2041 // new landingpad instruction if it does.
2042 for (unsigned k = i; k + 1 < j; ++k)
2043 if (shorter_filter(NewClauses[k+1], NewClauses[k])) {
2044 // Not sorted, so sort the filters now. Doing an unstable sort would be
2045 // correct too but reordering filters pointlessly might confuse users.
2046 std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j,
2048 MakeNewInstruction = true;
2052 // Look for the next batch of filters.
2056 // If typeinfos matched if and only if equal, then the elements of a filter L
2057 // that occurs later than a filter F could be replaced by the intersection of
2058 // the elements of F and L. In reality two typeinfos can match without being
2059 // equal (for example if one represents a C++ class, and the other some class
2060 // derived from it) so it would be wrong to perform this transform in general.
2061 // However the transform is correct and useful if F is a subset of L. In that
2062 // case L can be replaced by F, and thus removed altogether since repeating a
2063 // filter is pointless. So here we look at all pairs of filters F and L where
2064 // L follows F in the list of clauses, and remove L if every element of F is
2065 // an element of L. This can occur when inlining C++ functions with exception
2067 for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) {
2068 // Examine each filter in turn.
2069 Value *Filter = NewClauses[i];
2070 ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType());
2072 // Not a filter - skip it.
2074 unsigned FElts = FTy->getNumElements();
2075 // Examine each filter following this one. Doing this backwards means that
2076 // we don't have to worry about filters disappearing under us when removed.
2077 for (unsigned j = NewClauses.size() - 1; j != i; --j) {
2078 Value *LFilter = NewClauses[j];
2079 ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType());
2081 // Not a filter - skip it.
2083 // If Filter is a subset of LFilter, i.e. every element of Filter is also
2084 // an element of LFilter, then discard LFilter.
2085 SmallVectorImpl<Value *>::iterator J = NewClauses.begin() + j;
2086 // If Filter is empty then it is a subset of LFilter.
2089 NewClauses.erase(J);
2090 MakeNewInstruction = true;
2091 // Move on to the next filter.
2094 unsigned LElts = LTy->getNumElements();
2095 // If Filter is longer than LFilter then it cannot be a subset of it.
2097 // Move on to the next filter.
2099 // At this point we know that LFilter has at least one element.
2100 if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros.
2101 // Filter is a subset of LFilter iff Filter contains only zeros (as we
2102 // already know that Filter is not longer than LFilter).
2103 if (isa<ConstantAggregateZero>(Filter)) {
2104 assert(FElts <= LElts && "Should have handled this case earlier!");
2106 NewClauses.erase(J);
2107 MakeNewInstruction = true;
2109 // Move on to the next filter.
2112 ConstantArray *LArray = cast<ConstantArray>(LFilter);
2113 if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros.
2114 // Since Filter is non-empty and contains only zeros, it is a subset of
2115 // LFilter iff LFilter contains a zero.
2116 assert(FElts > 0 && "Should have eliminated the empty filter earlier!");
2117 for (unsigned l = 0; l != LElts; ++l)
2118 if (LArray->getOperand(l)->isNullValue()) {
2119 // LFilter contains a zero - discard it.
2120 NewClauses.erase(J);
2121 MakeNewInstruction = true;
2124 // Move on to the next filter.
2127 // At this point we know that both filters are ConstantArrays. Loop over
2128 // operands to see whether every element of Filter is also an element of
2129 // LFilter. Since filters tend to be short this is probably faster than
2130 // using a method that scales nicely.
2131 ConstantArray *FArray = cast<ConstantArray>(Filter);
2132 bool AllFound = true;
2133 for (unsigned f = 0; f != FElts; ++f) {
2134 Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts();
2136 for (unsigned l = 0; l != LElts; ++l) {
2137 Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts();
2138 if (LTypeInfo == FTypeInfo) {
2148 NewClauses.erase(J);
2149 MakeNewInstruction = true;
2151 // Move on to the next filter.
2155 // If we changed any of the clauses, replace the old landingpad instruction
2157 if (MakeNewInstruction) {
2158 LandingPadInst *NLI = LandingPadInst::Create(LI.getType(),
2159 LI.getPersonalityFn(),
2161 for (unsigned i = 0, e = NewClauses.size(); i != e; ++i)
2162 NLI->addClause(NewClauses[i]);
2163 // A landing pad with no clauses must have the cleanup flag set. It is
2164 // theoretically possible, though highly unlikely, that we eliminated all
2165 // clauses. If so, force the cleanup flag to true.
2166 if (NewClauses.empty())
2168 NLI->setCleanup(CleanupFlag);
2172 // Even if none of the clauses changed, we may nonetheless have understood
2173 // that the cleanup flag is pointless. Clear it if so.
2174 if (LI.isCleanup() != CleanupFlag) {
2175 assert(!CleanupFlag && "Adding a cleanup, not removing one?!");
2176 LI.setCleanup(CleanupFlag);
2186 /// TryToSinkInstruction - Try to move the specified instruction from its
2187 /// current block into the beginning of DestBlock, which can only happen if it's
2188 /// safe to move the instruction past all of the instructions between it and the
2189 /// end of its block.
2190 static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) {
2191 assert(I->hasOneUse() && "Invariants didn't hold!");
2193 // Cannot move control-flow-involving, volatile loads, vaarg, etc.
2194 if (isa<PHINode>(I) || isa<LandingPadInst>(I) || I->mayHaveSideEffects() ||
2195 isa<TerminatorInst>(I))
2198 // Do not sink alloca instructions out of the entry block.
2199 if (isa<AllocaInst>(I) && I->getParent() ==
2200 &DestBlock->getParent()->getEntryBlock())
2203 // We can only sink load instructions if there is nothing between the load and
2204 // the end of block that could change the value.
2205 if (I->mayReadFromMemory()) {
2206 for (BasicBlock::iterator Scan = I, E = I->getParent()->end();
2208 if (Scan->mayWriteToMemory())
2212 BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt();
2213 I->moveBefore(InsertPos);
2219 /// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
2220 /// all reachable code to the worklist.
2222 /// This has a couple of tricks to make the code faster and more powerful. In
2223 /// particular, we constant fold and DCE instructions as we go, to avoid adding
2224 /// them to the worklist (this significantly speeds up instcombine on code where
2225 /// many instructions are dead or constant). Additionally, if we find a branch
2226 /// whose condition is a known constant, we only visit the reachable successors.
2228 static bool AddReachableCodeToWorklist(BasicBlock *BB,
2229 SmallPtrSet<BasicBlock*, 64> &Visited,
2231 const DataLayout *DL,
2232 const TargetLibraryInfo *TLI) {
2233 bool MadeIRChange = false;
2234 SmallVector<BasicBlock*, 256> Worklist;
2235 Worklist.push_back(BB);
2237 SmallVector<Instruction*, 128> InstrsForInstCombineWorklist;
2238 DenseMap<ConstantExpr*, Constant*> FoldedConstants;
2241 BB = Worklist.pop_back_val();
2243 // We have now visited this block! If we've already been here, ignore it.
2244 if (!Visited.insert(BB)) continue;
2246 for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
2247 Instruction *Inst = BBI++;
2249 // DCE instruction if trivially dead.
2250 if (isInstructionTriviallyDead(Inst, TLI)) {
2252 DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
2253 Inst->eraseFromParent();
2257 // ConstantProp instruction if trivially constant.
2258 if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0)))
2259 if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) {
2260 DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: "
2262 Inst->replaceAllUsesWith(C);
2264 Inst->eraseFromParent();
2269 // See if we can constant fold its operands.
2270 for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end();
2272 ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
2273 if (CE == 0) continue;
2275 Constant*& FoldRes = FoldedConstants[CE];
2277 FoldRes = ConstantFoldConstantExpression(CE, DL, TLI);
2281 if (FoldRes != CE) {
2283 MadeIRChange = true;
2288 InstrsForInstCombineWorklist.push_back(Inst);
2291 // Recursively visit successors. If this is a branch or switch on a
2292 // constant, only visit the reachable successor.
2293 TerminatorInst *TI = BB->getTerminator();
2294 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
2295 if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
2296 bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
2297 BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
2298 Worklist.push_back(ReachableBB);
2301 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
2302 if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
2303 // See if this is an explicit destination.
2304 for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
2306 if (i.getCaseValue() == Cond) {
2307 BasicBlock *ReachableBB = i.getCaseSuccessor();
2308 Worklist.push_back(ReachableBB);
2312 // Otherwise it is the default destination.
2313 Worklist.push_back(SI->getDefaultDest());
2318 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
2319 Worklist.push_back(TI->getSuccessor(i));
2320 } while (!Worklist.empty());
2322 // Once we've found all of the instructions to add to instcombine's worklist,
2323 // add them in reverse order. This way instcombine will visit from the top
2324 // of the function down. This jives well with the way that it adds all uses
2325 // of instructions to the worklist after doing a transformation, thus avoiding
2326 // some N^2 behavior in pathological cases.
2327 IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
2328 InstrsForInstCombineWorklist.size());
2330 return MadeIRChange;
2333 bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
2334 MadeIRChange = false;
2336 DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
2337 << F.getName() << "\n");
2340 // Do a depth-first traversal of the function, populate the worklist with
2341 // the reachable instructions. Ignore blocks that are not reachable. Keep
2342 // track of which blocks we visit.
2343 SmallPtrSet<BasicBlock*, 64> Visited;
2344 MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, DL,
2347 // Do a quick scan over the function. If we find any blocks that are
2348 // unreachable, remove any instructions inside of them. This prevents
2349 // the instcombine code from having to deal with some bad special cases.
2350 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
2351 if (Visited.count(BB)) continue;
2353 // Delete the instructions backwards, as it has a reduced likelihood of
2354 // having to update as many def-use and use-def chains.
2355 Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
2356 while (EndInst != BB->begin()) {
2357 // Delete the next to last instruction.
2358 BasicBlock::iterator I = EndInst;
2359 Instruction *Inst = --I;
2360 if (!Inst->use_empty())
2361 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
2362 if (isa<LandingPadInst>(Inst)) {
2366 if (!isa<DbgInfoIntrinsic>(Inst)) {
2368 MadeIRChange = true;
2370 Inst->eraseFromParent();
2375 while (!Worklist.isEmpty()) {
2376 Instruction *I = Worklist.RemoveOne();
2377 if (I == 0) continue; // skip null values.
2379 // Check to see if we can DCE the instruction.
2380 if (isInstructionTriviallyDead(I, TLI)) {
2381 DEBUG(dbgs() << "IC: DCE: " << *I << '\n');
2382 EraseInstFromFunction(*I);
2384 MadeIRChange = true;
2388 // Instruction isn't dead, see if we can constant propagate it.
2389 if (!I->use_empty() && isa<Constant>(I->getOperand(0)))
2390 if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) {
2391 DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n');
2393 // Add operands to the worklist.
2394 ReplaceInstUsesWith(*I, C);
2396 EraseInstFromFunction(*I);
2397 MadeIRChange = true;
2401 // See if we can trivially sink this instruction to a successor basic block.
2402 if (I->hasOneUse()) {
2403 BasicBlock *BB = I->getParent();
2404 Instruction *UserInst = cast<Instruction>(*I->user_begin());
2405 BasicBlock *UserParent;
2407 // Get the block the use occurs in.
2408 if (PHINode *PN = dyn_cast<PHINode>(UserInst))
2409 UserParent = PN->getIncomingBlock(*I->use_begin());
2411 UserParent = UserInst->getParent();
2413 if (UserParent != BB) {
2414 bool UserIsSuccessor = false;
2415 // See if the user is one of our successors.
2416 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
2417 if (*SI == UserParent) {
2418 UserIsSuccessor = true;
2422 // If the user is one of our immediate successors, and if that successor
2423 // only has us as a predecessors (we'd have to split the critical edge
2424 // otherwise), we can keep going.
2425 if (UserIsSuccessor && UserParent->getSinglePredecessor())
2426 // Okay, the CFG is simple enough, try to sink this instruction.
2427 MadeIRChange |= TryToSinkInstruction(I, UserParent);
2431 // Now that we have an instruction, try combining it to simplify it.
2432 Builder->SetInsertPoint(I->getParent(), I);
2433 Builder->SetCurrentDebugLocation(I->getDebugLoc());
2438 DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str(););
2439 DEBUG(dbgs() << "IC: Visiting: " << OrigI << '\n');
2441 if (Instruction *Result = visit(*I)) {
2443 // Should we replace the old instruction with a new one?
2445 DEBUG(dbgs() << "IC: Old = " << *I << '\n'
2446 << " New = " << *Result << '\n');
2448 if (!I->getDebugLoc().isUnknown())
2449 Result->setDebugLoc(I->getDebugLoc());
2450 // Everything uses the new instruction now.
2451 I->replaceAllUsesWith(Result);
2453 // Move the name to the new instruction first.
2454 Result->takeName(I);
2456 // Push the new instruction and any users onto the worklist.
2457 Worklist.Add(Result);
2458 Worklist.AddUsersToWorkList(*Result);
2460 // Insert the new instruction into the basic block...
2461 BasicBlock *InstParent = I->getParent();
2462 BasicBlock::iterator InsertPos = I;
2464 // If we replace a PHI with something that isn't a PHI, fix up the
2466 if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos))
2467 InsertPos = InstParent->getFirstInsertionPt();
2469 InstParent->getInstList().insert(InsertPos, Result);
2471 EraseInstFromFunction(*I);
2474 DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n'
2475 << " New = " << *I << '\n');
2478 // If the instruction was modified, it's possible that it is now dead.
2479 // if so, remove it.
2480 if (isInstructionTriviallyDead(I, TLI)) {
2481 EraseInstFromFunction(*I);
2484 Worklist.AddUsersToWorkList(*I);
2487 MadeIRChange = true;
2492 return MadeIRChange;
2496 class InstCombinerLibCallSimplifier : public LibCallSimplifier {
2499 InstCombinerLibCallSimplifier(const DataLayout *DL,
2500 const TargetLibraryInfo *TLI,
2502 : LibCallSimplifier(DL, TLI, UnsafeFPShrink) {
2506 /// replaceAllUsesWith - override so that instruction replacement
2507 /// can be defined in terms of the instruction combiner framework.
2508 void replaceAllUsesWith(Instruction *I, Value *With) const override {
2509 IC->ReplaceInstUsesWith(*I, With);
2514 bool InstCombiner::runOnFunction(Function &F) {
2515 if (skipOptnoneFunction(F))
2518 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
2519 DL = DLP ? &DLP->getDataLayout() : 0;
2520 TLI = &getAnalysis<TargetLibraryInfo>();
2522 MinimizeSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
2523 Attribute::MinSize);
2525 /// Builder - This is an IRBuilder that automatically inserts new
2526 /// instructions into the worklist when they are created.
2527 IRBuilder<true, TargetFolder, InstCombineIRInserter>
2528 TheBuilder(F.getContext(), TargetFolder(DL),
2529 InstCombineIRInserter(Worklist));
2530 Builder = &TheBuilder;
2532 InstCombinerLibCallSimplifier TheSimplifier(DL, TLI, this);
2533 Simplifier = &TheSimplifier;
2535 bool EverMadeChange = false;
2537 // Lower dbg.declare intrinsics otherwise their value may be clobbered
2539 EverMadeChange = LowerDbgDeclare(F);
2541 // Iterate while there is work to do.
2542 unsigned Iteration = 0;
2543 while (DoOneIteration(F, Iteration++))
2544 EverMadeChange = true;
2547 return EverMadeChange;
2550 FunctionPass *llvm::createInstructionCombiningPass() {
2551 return new InstCombiner();