1 //===- InstCombineSelect.cpp ----------------------------------------------===//
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 // This file implements the visitSelect function.
12 //===----------------------------------------------------------------------===//
14 #include "InstCombineInternal.h"
15 #include "llvm/Analysis/ConstantFolding.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
17 #include "llvm/IR/PatternMatch.h"
19 using namespace PatternMatch;
21 #define DEBUG_TYPE "instcombine"
23 /// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
24 /// returning the kind and providing the out parameter results if we
25 /// successfully match.
26 static SelectPatternFlavor
27 MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
28 SelectInst *SI = dyn_cast<SelectInst>(V);
29 if (!SI) return SPF_UNKNOWN;
31 ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
32 if (!ICI) return SPF_UNKNOWN;
34 ICmpInst::Predicate Pred = ICI->getPredicate();
35 Value *CmpLHS = ICI->getOperand(0);
36 Value *CmpRHS = ICI->getOperand(1);
37 Value *TrueVal = SI->getTrueValue();
38 Value *FalseVal = SI->getFalseValue();
43 // (icmp X, Y) ? X : Y
44 if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
46 default: return SPF_UNKNOWN; // Equality.
47 case ICmpInst::ICMP_UGT:
48 case ICmpInst::ICMP_UGE: return SPF_UMAX;
49 case ICmpInst::ICMP_SGT:
50 case ICmpInst::ICMP_SGE: return SPF_SMAX;
51 case ICmpInst::ICMP_ULT:
52 case ICmpInst::ICMP_ULE: return SPF_UMIN;
53 case ICmpInst::ICMP_SLT:
54 case ICmpInst::ICMP_SLE: return SPF_SMIN;
58 // (icmp X, Y) ? Y : X
59 if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
61 default: return SPF_UNKNOWN; // Equality.
62 case ICmpInst::ICMP_UGT:
63 case ICmpInst::ICMP_UGE: return SPF_UMIN;
64 case ICmpInst::ICMP_SGT:
65 case ICmpInst::ICMP_SGE: return SPF_SMIN;
66 case ICmpInst::ICMP_ULT:
67 case ICmpInst::ICMP_ULE: return SPF_UMAX;
68 case ICmpInst::ICMP_SLT:
69 case ICmpInst::ICMP_SLE: return SPF_SMAX;
73 if (ConstantInt *C1 = dyn_cast<ConstantInt>(CmpRHS)) {
74 if ((CmpLHS == TrueVal && match(FalseVal, m_Neg(m_Specific(CmpLHS)))) ||
75 (CmpLHS == FalseVal && match(TrueVal, m_Neg(m_Specific(CmpLHS))))) {
77 // ABS(X) ==> (X >s 0) ? X : -X and (X >s -1) ? X : -X
78 // NABS(X) ==> (X >s 0) ? -X : X and (X >s -1) ? -X : X
79 if (Pred == ICmpInst::ICMP_SGT && (C1->isZero() || C1->isMinusOne())) {
80 return (CmpLHS == TrueVal) ? SPF_ABS : SPF_NABS;
83 // ABS(X) ==> (X <s 0) ? -X : X and (X <s 1) ? -X : X
84 // NABS(X) ==> (X <s 0) ? X : -X and (X <s 1) ? X : -X
85 if (Pred == ICmpInst::ICMP_SLT && (C1->isZero() || C1->isOne())) {
86 return (CmpLHS == FalseVal) ? SPF_ABS : SPF_NABS;
90 // Y >s C ? ~Y : ~C == ~Y <s ~C ? ~Y : ~C = SMIN(~Y, ~C)
91 if (const auto *C2 = dyn_cast<ConstantInt>(FalseVal)) {
92 if (C1->getType() == C2->getType() && ~C1->getValue() == C2->getValue() &&
93 (match(TrueVal, m_Not(m_Specific(CmpLHS))) ||
94 match(CmpLHS, m_Not(m_Specific(TrueVal))))) {
102 // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
108 /// GetSelectFoldableOperands - We want to turn code that looks like this:
110 /// %D = select %cond, %C, %A
112 /// %C = select %cond, %B, 0
115 /// Assuming that the specified instruction is an operand to the select, return
116 /// a bitmask indicating which operands of this instruction are foldable if they
117 /// equal the other incoming value of the select.
119 static unsigned GetSelectFoldableOperands(Instruction *I) {
120 switch (I->getOpcode()) {
121 case Instruction::Add:
122 case Instruction::Mul:
123 case Instruction::And:
124 case Instruction::Or:
125 case Instruction::Xor:
126 return 3; // Can fold through either operand.
127 case Instruction::Sub: // Can only fold on the amount subtracted.
128 case Instruction::Shl: // Can only fold on the shift amount.
129 case Instruction::LShr:
130 case Instruction::AShr:
133 return 0; // Cannot fold
137 /// GetSelectFoldableConstant - For the same transformation as the previous
138 /// function, return the identity constant that goes into the select.
139 static Constant *GetSelectFoldableConstant(Instruction *I) {
140 switch (I->getOpcode()) {
141 default: llvm_unreachable("This cannot happen!");
142 case Instruction::Add:
143 case Instruction::Sub:
144 case Instruction::Or:
145 case Instruction::Xor:
146 case Instruction::Shl:
147 case Instruction::LShr:
148 case Instruction::AShr:
149 return Constant::getNullValue(I->getType());
150 case Instruction::And:
151 return Constant::getAllOnesValue(I->getType());
152 case Instruction::Mul:
153 return ConstantInt::get(I->getType(), 1);
157 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
158 /// have the same opcode and only one use each. Try to simplify this.
159 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
161 if (TI->getNumOperands() == 1) {
162 // If this is a non-volatile load or a cast from the same type,
165 Type *FIOpndTy = FI->getOperand(0)->getType();
166 if (TI->getOperand(0)->getType() != FIOpndTy)
168 // The select condition may be a vector. We may only change the operand
169 // type if the vector width remains the same (and matches the condition).
170 Type *CondTy = SI.getCondition()->getType();
171 if (CondTy->isVectorTy() && (!FIOpndTy->isVectorTy() ||
172 CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements()))
175 return nullptr; // unknown unary op.
178 // Fold this by inserting a select from the input values.
179 Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0),
180 FI->getOperand(0), SI.getName()+".v");
181 return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
185 // Only handle binary operators here.
186 if (!isa<BinaryOperator>(TI))
189 // Figure out if the operations have any operands in common.
190 Value *MatchOp, *OtherOpT, *OtherOpF;
192 if (TI->getOperand(0) == FI->getOperand(0)) {
193 MatchOp = TI->getOperand(0);
194 OtherOpT = TI->getOperand(1);
195 OtherOpF = FI->getOperand(1);
196 MatchIsOpZero = true;
197 } else if (TI->getOperand(1) == FI->getOperand(1)) {
198 MatchOp = TI->getOperand(1);
199 OtherOpT = TI->getOperand(0);
200 OtherOpF = FI->getOperand(0);
201 MatchIsOpZero = false;
202 } else if (!TI->isCommutative()) {
204 } else if (TI->getOperand(0) == FI->getOperand(1)) {
205 MatchOp = TI->getOperand(0);
206 OtherOpT = TI->getOperand(1);
207 OtherOpF = FI->getOperand(0);
208 MatchIsOpZero = true;
209 } else if (TI->getOperand(1) == FI->getOperand(0)) {
210 MatchOp = TI->getOperand(1);
211 OtherOpT = TI->getOperand(0);
212 OtherOpF = FI->getOperand(1);
213 MatchIsOpZero = true;
218 // If we reach here, they do have operations in common.
219 Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT,
220 OtherOpF, SI.getName()+".v");
222 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
224 return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
226 return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
228 llvm_unreachable("Shouldn't get here");
231 static bool isSelect01(Constant *C1, Constant *C2) {
232 ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
235 ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
238 if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
240 return C1I->isOne() || C1I->isAllOnesValue() ||
241 C2I->isOne() || C2I->isAllOnesValue();
244 /// FoldSelectIntoOp - Try fold the select into one of the operands to
245 /// facilitate further optimization.
246 Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
248 // See the comment above GetSelectFoldableOperands for a description of the
249 // transformation we are doing here.
250 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
251 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
252 !isa<Constant>(FalseVal)) {
253 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
254 unsigned OpToFold = 0;
255 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
257 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
262 Constant *C = GetSelectFoldableConstant(TVI);
263 Value *OOp = TVI->getOperand(2-OpToFold);
264 // Avoid creating select between 2 constants unless it's selecting
265 // between 0, 1 and -1.
266 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
267 Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C);
268 NewSel->takeName(TVI);
269 BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI);
270 BinaryOperator *BO = BinaryOperator::Create(TVI_BO->getOpcode(),
272 if (isa<PossiblyExactOperator>(BO))
273 BO->setIsExact(TVI_BO->isExact());
274 if (isa<OverflowingBinaryOperator>(BO)) {
275 BO->setHasNoUnsignedWrap(TVI_BO->hasNoUnsignedWrap());
276 BO->setHasNoSignedWrap(TVI_BO->hasNoSignedWrap());
285 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
286 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
287 !isa<Constant>(TrueVal)) {
288 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
289 unsigned OpToFold = 0;
290 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
292 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
297 Constant *C = GetSelectFoldableConstant(FVI);
298 Value *OOp = FVI->getOperand(2-OpToFold);
299 // Avoid creating select between 2 constants unless it's selecting
300 // between 0, 1 and -1.
301 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
302 Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp);
303 NewSel->takeName(FVI);
304 BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI);
305 BinaryOperator *BO = BinaryOperator::Create(FVI_BO->getOpcode(),
307 if (isa<PossiblyExactOperator>(BO))
308 BO->setIsExact(FVI_BO->isExact());
309 if (isa<OverflowingBinaryOperator>(BO)) {
310 BO->setHasNoUnsignedWrap(FVI_BO->hasNoUnsignedWrap());
311 BO->setHasNoSignedWrap(FVI_BO->hasNoSignedWrap());
323 /// SimplifyWithOpReplaced - See if V simplifies when its operand Op is
324 /// replaced with RepOp.
325 static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
326 const TargetLibraryInfo *TLI,
327 const DataLayout &DL, DominatorTree *DT,
328 AssumptionCache *AC) {
329 // Trivial replacement.
333 Instruction *I = dyn_cast<Instruction>(V);
337 // If this is a binary operator, try to simplify it with the replaced op.
338 if (BinaryOperator *B = dyn_cast<BinaryOperator>(I)) {
339 if (B->getOperand(0) == Op)
340 return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), DL, TLI);
341 if (B->getOperand(1) == Op)
342 return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, DL, TLI);
345 // Same for CmpInsts.
346 if (CmpInst *C = dyn_cast<CmpInst>(I)) {
347 if (C->getOperand(0) == Op)
348 return SimplifyCmpInst(C->getPredicate(), RepOp, C->getOperand(1), DL,
350 if (C->getOperand(1) == Op)
351 return SimplifyCmpInst(C->getPredicate(), C->getOperand(0), RepOp, DL,
355 // TODO: We could hand off more cases to instsimplify here.
357 // If all operands are constant after substituting Op for RepOp then we can
358 // constant fold the instruction.
359 if (Constant *CRepOp = dyn_cast<Constant>(RepOp)) {
360 // Build a list of all constant operands.
361 SmallVector<Constant*, 8> ConstOps;
362 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
363 if (I->getOperand(i) == Op)
364 ConstOps.push_back(CRepOp);
365 else if (Constant *COp = dyn_cast<Constant>(I->getOperand(i)))
366 ConstOps.push_back(COp);
371 // All operands were constants, fold it.
372 if (ConstOps.size() == I->getNumOperands()) {
373 if (CmpInst *C = dyn_cast<CmpInst>(I))
374 return ConstantFoldCompareInstOperands(C->getPredicate(), ConstOps[0],
375 ConstOps[1], DL, TLI);
377 if (LoadInst *LI = dyn_cast<LoadInst>(I))
378 if (!LI->isVolatile())
379 return ConstantFoldLoadFromConstPtr(ConstOps[0], DL);
381 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), ConstOps,
389 /// foldSelectICmpAndOr - We want to turn:
390 /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2))
392 /// (or (shl (and X, C1), C3), y)
394 /// C1 and C2 are both powers of 2
396 /// C3 = Log(C2) - Log(C1)
398 /// This transform handles cases where:
399 /// 1. The icmp predicate is inverted
400 /// 2. The select operands are reversed
401 /// 3. The magnitude of C2 and C1 are flipped
402 static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
404 InstCombiner::BuilderTy *Builder) {
405 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
406 if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
409 Value *CmpLHS = IC->getOperand(0);
410 Value *CmpRHS = IC->getOperand(1);
412 if (!match(CmpRHS, m_Zero()))
417 if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1))))
421 bool OrOnTrueVal = false;
422 bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
424 OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)));
426 if (!OrOnFalseVal && !OrOnTrueVal)
430 Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
432 unsigned C1Log = C1->logBase2();
433 unsigned C2Log = C2->logBase2();
435 V = Builder->CreateZExtOrTrunc(V, Y->getType());
436 V = Builder->CreateShl(V, C2Log - C1Log);
437 } else if (C1Log > C2Log) {
438 V = Builder->CreateLShr(V, C1Log - C2Log);
439 V = Builder->CreateZExtOrTrunc(V, Y->getType());
441 V = Builder->CreateZExtOrTrunc(V, Y->getType());
443 ICmpInst::Predicate Pred = IC->getPredicate();
444 if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) ||
445 (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal))
446 V = Builder->CreateXor(V, *C2);
448 return Builder->CreateOr(V, Y);
451 /// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single
452 /// call to cttz/ctlz with flag 'is_zero_undef' cleared.
454 /// For example, we can fold the following code sequence:
456 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
457 /// %1 = icmp ne i32 %x, 0
458 /// %2 = select i1 %1, i32 %0, i32 32
462 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
463 static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
464 InstCombiner::BuilderTy *Builder) {
465 ICmpInst::Predicate Pred = ICI->getPredicate();
466 Value *CmpLHS = ICI->getOperand(0);
467 Value *CmpRHS = ICI->getOperand(1);
469 // Check if the condition value compares a value for equality against zero.
470 if (!ICI->isEquality() || !match(CmpRHS, m_Zero()))
473 Value *Count = FalseVal;
474 Value *ValueOnZero = TrueVal;
475 if (Pred == ICmpInst::ICMP_NE)
476 std::swap(Count, ValueOnZero);
478 // Skip zero extend/truncate.
480 if (match(Count, m_ZExt(m_Value(V))) ||
481 match(Count, m_Trunc(m_Value(V))))
484 // Check if the value propagated on zero is a constant number equal to the
485 // sizeof in bits of 'Count'.
486 unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits();
487 if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits)))
490 // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the
491 // input to the cttz/ctlz is used as LHS for the compare instruction.
492 if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) ||
493 match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) {
494 IntrinsicInst *II = cast<IntrinsicInst>(Count);
495 IRBuilder<> Builder(II);
496 // Explicitly clear the 'undef_on_zero' flag.
497 IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone());
498 Type *Ty = NewI->getArgOperand(1)->getType();
499 NewI->setArgOperand(1, Constant::getNullValue(Ty));
500 Builder.Insert(NewI);
501 return Builder.CreateZExtOrTrunc(NewI, ValueOnZero->getType());
507 /// visitSelectInstWithICmp - Visit a SelectInst that has an
508 /// ICmpInst as its first operand.
510 Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
512 bool Changed = false;
513 ICmpInst::Predicate Pred = ICI->getPredicate();
514 Value *CmpLHS = ICI->getOperand(0);
515 Value *CmpRHS = ICI->getOperand(1);
516 Value *TrueVal = SI.getTrueValue();
517 Value *FalseVal = SI.getFalseValue();
519 // Check cases where the comparison is with a constant that
520 // can be adjusted to fit the min/max idiom. We may move or edit ICI
521 // here, so make sure the select is the only user.
522 if (ICI->hasOneUse())
523 if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
524 // X < MIN ? T : F --> F
525 if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT)
526 && CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
527 return ReplaceInstUsesWith(SI, FalseVal);
528 // X > MAX ? T : F --> F
529 else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT)
530 && CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
531 return ReplaceInstUsesWith(SI, FalseVal);
534 case ICmpInst::ICMP_ULT:
535 case ICmpInst::ICMP_SLT:
536 case ICmpInst::ICMP_UGT:
537 case ICmpInst::ICMP_SGT: {
538 // These transformations only work for selects over integers.
539 IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
543 Constant *AdjustedRHS;
544 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
545 AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
546 else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
547 AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
549 // X > C ? X : C+1 --> X < C+1 ? C+1 : X
550 // X < C ? X : C-1 --> X > C-1 ? C-1 : X
551 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
552 (CmpLHS == FalseVal && AdjustedRHS == TrueVal))
553 ; // Nothing to do here. Values match without any sign/zero extension.
555 // Types do not match. Instead of calculating this with mixed types
556 // promote all to the larger type. This enables scalar evolution to
557 // analyze this expression.
558 else if (CmpRHS->getType()->getScalarSizeInBits()
559 < SelectTy->getBitWidth()) {
560 Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
562 // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
563 // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
564 // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
565 // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
566 if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
567 sextRHS == FalseVal) {
569 AdjustedRHS = sextRHS;
570 } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
571 sextRHS == TrueVal) {
573 AdjustedRHS = sextRHS;
574 } else if (ICI->isUnsigned()) {
575 Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy);
576 // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
577 // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
578 // zext + signed compare cannot be changed:
579 // 0xff <s 0x00, but 0x00ff >s 0x0000
580 if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
581 zextRHS == FalseVal) {
583 AdjustedRHS = zextRHS;
584 } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
585 zextRHS == TrueVal) {
587 AdjustedRHS = zextRHS;
595 Pred = ICmpInst::getSwappedPredicate(Pred);
596 CmpRHS = AdjustedRHS;
597 std::swap(FalseVal, TrueVal);
598 ICI->setPredicate(Pred);
599 ICI->setOperand(0, CmpLHS);
600 ICI->setOperand(1, CmpRHS);
601 SI.setOperand(1, TrueVal);
602 SI.setOperand(2, FalseVal);
604 // Move ICI instruction right before the select instruction. Otherwise
605 // the sext/zext value may be defined after the ICI instruction uses it.
606 ICI->moveBefore(&SI);
614 // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
615 // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
616 // FIXME: Type and constness constraints could be lifted, but we have to
617 // watch code size carefully. We should consider xor instead of
618 // sub/add when we decide to do that.
619 if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
620 if (TrueVal->getType() == Ty) {
621 if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
622 ConstantInt *C1 = nullptr, *C2 = nullptr;
623 if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
624 C1 = dyn_cast<ConstantInt>(TrueVal);
625 C2 = dyn_cast<ConstantInt>(FalseVal);
626 } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
627 C1 = dyn_cast<ConstantInt>(FalseVal);
628 C2 = dyn_cast<ConstantInt>(TrueVal);
631 // This shift results in either -1 or 0.
632 Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
634 // Check if we can express the operation with a single or.
635 if (C2->isAllOnesValue())
636 return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
638 Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
639 return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
645 // If we have an equality comparison then we know the value in one of the
646 // arms of the select. See if substituting this value into the arm and
647 // simplifying the result yields the same value as the other arm.
648 if (Pred == ICmpInst::ICMP_EQ) {
649 if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, TLI, DL, DT, AC) ==
651 SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, TLI, DL, DT, AC) ==
653 return ReplaceInstUsesWith(SI, FalseVal);
654 if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, TLI, DL, DT, AC) ==
656 SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, TLI, DL, DT, AC) ==
658 return ReplaceInstUsesWith(SI, FalseVal);
659 } else if (Pred == ICmpInst::ICMP_NE) {
660 if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, TLI, DL, DT, AC) ==
662 SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, TLI, DL, DT, AC) ==
664 return ReplaceInstUsesWith(SI, TrueVal);
665 if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, TLI, DL, DT, AC) ==
667 SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, TLI, DL, DT, AC) ==
669 return ReplaceInstUsesWith(SI, TrueVal);
672 // NOTE: if we wanted to, this is where to detect integer MIN/MAX
674 if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) {
675 if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
676 // Transform (X == C) ? X : Y -> (X == C) ? C : Y
677 SI.setOperand(1, CmpRHS);
679 } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) {
680 // Transform (X != C) ? Y : X -> (X != C) ? Y : C
681 SI.setOperand(2, CmpRHS);
686 if (unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits()) {
687 APInt MinSignedValue = APInt::getSignBit(BitWidth);
691 bool IsBitTest = false;
692 if (ICmpInst::isEquality(Pred) &&
693 match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
694 match(CmpRHS, m_Zero())) {
696 TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
697 } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
701 TrueWhenUnset = false;
702 } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
706 TrueWhenUnset = true;
710 // (X & Y) == 0 ? X : X ^ Y --> X & ~Y
711 if (TrueWhenUnset && TrueVal == X &&
712 match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
713 V = Builder->CreateAnd(X, ~(*Y));
714 // (X & Y) != 0 ? X ^ Y : X --> X & ~Y
715 else if (!TrueWhenUnset && FalseVal == X &&
716 match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
717 V = Builder->CreateAnd(X, ~(*Y));
718 // (X & Y) == 0 ? X ^ Y : X --> X | Y
719 else if (TrueWhenUnset && FalseVal == X &&
720 match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
721 V = Builder->CreateOr(X, *Y);
722 // (X & Y) != 0 ? X : X ^ Y --> X | Y
723 else if (!TrueWhenUnset && TrueVal == X &&
724 match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
725 V = Builder->CreateOr(X, *Y);
728 return ReplaceInstUsesWith(SI, V);
732 if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
733 return ReplaceInstUsesWith(SI, V);
735 if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder))
736 return ReplaceInstUsesWith(SI, V);
738 return Changed ? &SI : nullptr;
742 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
743 /// PHI node (but the two may be in different blocks). See if the true/false
744 /// values (V) are live in all of the predecessor blocks of the PHI. For
745 /// example, cases like this cannot be mapped:
747 /// X = phi [ C1, BB1], [C2, BB2]
749 /// Z = select X, Y, 0
751 /// because Y is not live in BB1/BB2.
753 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
754 const SelectInst &SI) {
755 // If the value is a non-instruction value like a constant or argument, it
756 // can always be mapped.
757 const Instruction *I = dyn_cast<Instruction>(V);
760 // If V is a PHI node defined in the same block as the condition PHI, we can
761 // map the arguments.
762 const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
764 if (const PHINode *VP = dyn_cast<PHINode>(I))
765 if (VP->getParent() == CondPHI->getParent())
768 // Otherwise, if the PHI and select are defined in the same block and if V is
769 // defined in a different block, then we can transform it.
770 if (SI.getParent() == CondPHI->getParent() &&
771 I->getParent() != CondPHI->getParent())
774 // Otherwise we have a 'hard' case and we can't tell without doing more
775 // detailed dominator based analysis, punt.
779 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
780 /// SPF2(SPF1(A, B), C)
781 Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
782 SelectPatternFlavor SPF1,
785 SelectPatternFlavor SPF2, Value *C) {
786 if (C == A || C == B) {
787 // MAX(MAX(A, B), B) -> MAX(A, B)
788 // MIN(MIN(a, b), a) -> MIN(a, b)
790 return ReplaceInstUsesWith(Outer, Inner);
792 // MAX(MIN(a, b), a) -> a
793 // MIN(MAX(a, b), a) -> a
794 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
795 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
796 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
797 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
798 return ReplaceInstUsesWith(Outer, C);
802 if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) {
803 if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) {
804 APInt ACB = CB->getValue();
805 APInt ACC = CC->getValue();
807 // MIN(MIN(A, 23), 97) -> MIN(A, 23)
808 // MAX(MAX(A, 97), 23) -> MAX(A, 97)
809 if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) ||
810 (SPF1 == SPF_SMIN && ACB.sle(ACC)) ||
811 (SPF1 == SPF_UMAX && ACB.uge(ACC)) ||
812 (SPF1 == SPF_SMAX && ACB.sge(ACC)))
813 return ReplaceInstUsesWith(Outer, Inner);
815 // MIN(MIN(A, 97), 23) -> MIN(A, 23)
816 // MAX(MAX(A, 23), 97) -> MAX(A, 97)
817 if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) ||
818 (SPF1 == SPF_SMIN && ACB.sgt(ACC)) ||
819 (SPF1 == SPF_UMAX && ACB.ult(ACC)) ||
820 (SPF1 == SPF_SMAX && ACB.slt(ACC))) {
821 Outer.replaceUsesOfWith(Inner, A);
828 // ABS(ABS(X)) -> ABS(X)
829 // NABS(NABS(X)) -> NABS(X)
830 if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) {
831 return ReplaceInstUsesWith(Outer, Inner);
834 // ABS(NABS(X)) -> ABS(X)
835 // NABS(ABS(X)) -> NABS(X)
836 if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) ||
837 (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) {
838 SelectInst *SI = cast<SelectInst>(Inner);
839 Value *NewSI = Builder->CreateSelect(
840 SI->getCondition(), SI->getFalseValue(), SI->getTrueValue());
841 return ReplaceInstUsesWith(Outer, NewSI);
846 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
847 /// both be) and we have an icmp instruction with zero, and we have an 'and'
848 /// with the non-constant value and a power of two we can turn the select
849 /// into a shift on the result of the 'and'.
850 static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
851 ConstantInt *FalseVal,
852 InstCombiner::BuilderTy *Builder) {
853 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
854 if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
857 if (!match(IC->getOperand(1), m_Zero()))
861 Value *LHS = IC->getOperand(0);
862 if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
865 // If both select arms are non-zero see if we have a select of the form
866 // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
867 // for 'x ? 2^n : 0' and fix the thing up at the end.
868 ConstantInt *Offset = nullptr;
869 if (!TrueVal->isZero() && !FalseVal->isZero()) {
870 if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
872 else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
877 // Adjust TrueVal and FalseVal to the offset.
878 TrueVal = ConstantInt::get(Builder->getContext(),
879 TrueVal->getValue() - Offset->getValue());
880 FalseVal = ConstantInt::get(Builder->getContext(),
881 FalseVal->getValue() - Offset->getValue());
884 // Make sure the mask in the 'and' and one of the select arms is a power of 2.
885 if (!AndRHS->getValue().isPowerOf2() ||
886 (!TrueVal->getValue().isPowerOf2() &&
887 !FalseVal->getValue().isPowerOf2()))
890 // Determine which shift is needed to transform result of the 'and' into the
892 ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
893 unsigned ValZeros = ValC->getValue().logBase2();
894 unsigned AndZeros = AndRHS->getValue().logBase2();
896 // If types don't match we can still convert the select by introducing a zext
897 // or a trunc of the 'and'. The trunc case requires that all of the truncated
898 // bits are zero, we can figure that out by looking at the 'and' mask.
899 if (AndZeros >= ValC->getBitWidth())
902 Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
903 if (ValZeros > AndZeros)
904 V = Builder->CreateShl(V, ValZeros - AndZeros);
905 else if (ValZeros < AndZeros)
906 V = Builder->CreateLShr(V, AndZeros - ValZeros);
908 // Okay, now we know that everything is set up, we just don't know whether we
909 // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
910 bool ShouldNotVal = !TrueVal->isZero();
911 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
913 V = Builder->CreateXor(V, ValC);
915 // Apply an offset if needed.
917 V = Builder->CreateAdd(V, Offset);
921 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
922 Value *CondVal = SI.getCondition();
923 Value *TrueVal = SI.getTrueValue();
924 Value *FalseVal = SI.getFalseValue();
927 SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC))
928 return ReplaceInstUsesWith(SI, V);
930 if (SI.getType()->isIntegerTy(1)) {
931 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
932 if (C->getZExtValue()) {
933 // Change: A = select B, true, C --> A = or B, C
934 return BinaryOperator::CreateOr(CondVal, FalseVal);
936 // Change: A = select B, false, C --> A = and !B, C
937 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
938 return BinaryOperator::CreateAnd(NotCond, FalseVal);
940 if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
941 if (!C->getZExtValue()) {
942 // Change: A = select B, C, false --> A = and B, C
943 return BinaryOperator::CreateAnd(CondVal, TrueVal);
945 // Change: A = select B, C, true --> A = or !B, C
946 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
947 return BinaryOperator::CreateOr(NotCond, TrueVal);
950 // select a, b, a -> a&b
951 // select a, a, b -> a|b
952 if (CondVal == TrueVal)
953 return BinaryOperator::CreateOr(CondVal, FalseVal);
954 if (CondVal == FalseVal)
955 return BinaryOperator::CreateAnd(CondVal, TrueVal);
957 // select a, ~a, b -> (~a)&b
958 // select a, b, ~a -> (~a)|b
959 if (match(TrueVal, m_Not(m_Specific(CondVal))))
960 return BinaryOperator::CreateAnd(TrueVal, FalseVal);
961 if (match(FalseVal, m_Not(m_Specific(CondVal))))
962 return BinaryOperator::CreateOr(TrueVal, FalseVal);
965 // Selecting between two integer constants?
966 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
967 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
968 // select C, 1, 0 -> zext C to int
969 if (FalseValC->isZero() && TrueValC->getValue() == 1)
970 return new ZExtInst(CondVal, SI.getType());
972 // select C, -1, 0 -> sext C to int
973 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
974 return new SExtInst(CondVal, SI.getType());
976 // select C, 0, 1 -> zext !C to int
977 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
978 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
979 return new ZExtInst(NotCond, SI.getType());
982 // select C, 0, -1 -> sext !C to int
983 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
984 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
985 return new SExtInst(NotCond, SI.getType());
988 if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
989 return ReplaceInstUsesWith(SI, V);
992 // See if we are selecting two values based on a comparison of the two values.
993 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
994 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
995 // Transform (X == Y) ? X : Y -> Y
996 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
997 // This is not safe in general for floating point:
998 // consider X== -0, Y== +0.
999 // It becomes safe if either operand is a nonzero constant.
1000 ConstantFP *CFPt, *CFPf;
1001 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1002 !CFPt->getValueAPF().isZero()) ||
1003 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1004 !CFPf->getValueAPF().isZero()))
1005 return ReplaceInstUsesWith(SI, FalseVal);
1007 // Transform (X une Y) ? X : Y -> X
1008 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
1009 // This is not safe in general for floating point:
1010 // consider X== -0, Y== +0.
1011 // It becomes safe if either operand is a nonzero constant.
1012 ConstantFP *CFPt, *CFPf;
1013 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1014 !CFPt->getValueAPF().isZero()) ||
1015 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1016 !CFPf->getValueAPF().isZero()))
1017 return ReplaceInstUsesWith(SI, TrueVal);
1020 // Canonicalize to use ordered comparisons by swapping the select
1024 // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
1025 if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
1026 FCmpInst::Predicate InvPred = FCI->getInversePredicate();
1027 Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
1028 FCI->getName() + ".inv");
1030 return SelectInst::Create(NewCond, FalseVal, TrueVal,
1031 SI.getName() + ".p");
1034 // NOTE: if we wanted to, this is where to detect MIN/MAX
1035 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
1036 // Transform (X == Y) ? Y : X -> X
1037 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
1038 // This is not safe in general for floating point:
1039 // consider X== -0, Y== +0.
1040 // It becomes safe if either operand is a nonzero constant.
1041 ConstantFP *CFPt, *CFPf;
1042 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1043 !CFPt->getValueAPF().isZero()) ||
1044 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1045 !CFPf->getValueAPF().isZero()))
1046 return ReplaceInstUsesWith(SI, FalseVal);
1048 // Transform (X une Y) ? Y : X -> Y
1049 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
1050 // This is not safe in general for floating point:
1051 // consider X== -0, Y== +0.
1052 // It becomes safe if either operand is a nonzero constant.
1053 ConstantFP *CFPt, *CFPf;
1054 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1055 !CFPt->getValueAPF().isZero()) ||
1056 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1057 !CFPf->getValueAPF().isZero()))
1058 return ReplaceInstUsesWith(SI, TrueVal);
1061 // Canonicalize to use ordered comparisons by swapping the select
1065 // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
1066 if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
1067 FCmpInst::Predicate InvPred = FCI->getInversePredicate();
1068 Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
1069 FCI->getName() + ".inv");
1071 return SelectInst::Create(NewCond, FalseVal, TrueVal,
1072 SI.getName() + ".p");
1075 // NOTE: if we wanted to, this is where to detect MIN/MAX
1077 // NOTE: if we wanted to, this is where to detect ABS
1080 // See if we are selecting two values based on a comparison of the two values.
1081 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
1082 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
1085 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
1086 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
1087 if (TI->hasOneUse() && FI->hasOneUse()) {
1088 Instruction *AddOp = nullptr, *SubOp = nullptr;
1090 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
1091 if (TI->getOpcode() == FI->getOpcode())
1092 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
1095 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
1096 // even legal for FP.
1097 if ((TI->getOpcode() == Instruction::Sub &&
1098 FI->getOpcode() == Instruction::Add) ||
1099 (TI->getOpcode() == Instruction::FSub &&
1100 FI->getOpcode() == Instruction::FAdd)) {
1101 AddOp = FI; SubOp = TI;
1102 } else if ((FI->getOpcode() == Instruction::Sub &&
1103 TI->getOpcode() == Instruction::Add) ||
1104 (FI->getOpcode() == Instruction::FSub &&
1105 TI->getOpcode() == Instruction::FAdd)) {
1106 AddOp = TI; SubOp = FI;
1110 Value *OtherAddOp = nullptr;
1111 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
1112 OtherAddOp = AddOp->getOperand(1);
1113 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
1114 OtherAddOp = AddOp->getOperand(0);
1118 // So at this point we know we have (Y -> OtherAddOp):
1119 // select C, (add X, Y), (sub X, Z)
1120 Value *NegVal; // Compute -Z
1121 if (SI.getType()->isFPOrFPVectorTy()) {
1122 NegVal = Builder->CreateFNeg(SubOp->getOperand(1));
1123 if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) {
1124 FastMathFlags Flags = AddOp->getFastMathFlags();
1125 Flags &= SubOp->getFastMathFlags();
1126 NegInst->setFastMathFlags(Flags);
1129 NegVal = Builder->CreateNeg(SubOp->getOperand(1));
1132 Value *NewTrueOp = OtherAddOp;
1133 Value *NewFalseOp = NegVal;
1135 std::swap(NewTrueOp, NewFalseOp);
1137 Builder->CreateSelect(CondVal, NewTrueOp,
1138 NewFalseOp, SI.getName() + ".p");
1140 if (SI.getType()->isFPOrFPVectorTy()) {
1142 BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
1144 FastMathFlags Flags = AddOp->getFastMathFlags();
1145 Flags &= SubOp->getFastMathFlags();
1146 RI->setFastMathFlags(Flags);
1149 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
1154 // See if we can fold the select into one of our operands.
1155 if (SI.getType()->isIntegerTy()) {
1156 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
1159 Value *LHS, *RHS, *LHS2, *RHS2;
1160 SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS);
1162 // MAX(MAX(a, b), a) -> MAX(a, b)
1163 // MIN(MIN(a, b), a) -> MIN(a, b)
1164 // MAX(MIN(a, b), a) -> a
1165 // MIN(MAX(a, b), a) -> a
1167 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
1168 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
1171 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
1172 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
1177 // MAX(~a, ~b) -> ~MIN(a, b)
1178 if (SPF == SPF_SMAX || SPF == SPF_UMAX) {
1179 if (IsFreeToInvert(LHS, LHS->hasNUses(2)) &&
1180 IsFreeToInvert(RHS, RHS->hasNUses(2))) {
1182 // This transform adds a xor operation and that extra cost needs to be
1183 // justified. We look for simplifications that will result from
1184 // applying this rule:
1187 (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) ||
1188 (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) ||
1189 (SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value())));
1192 Value *NewLHS = Builder->CreateNot(LHS);
1193 Value *NewRHS = Builder->CreateNot(RHS);
1194 Value *NewCmp = SPF == SPF_SMAX
1195 ? Builder->CreateICmpSLT(NewLHS, NewRHS)
1196 : Builder->CreateICmpULT(NewLHS, NewRHS);
1198 Builder->CreateNot(Builder->CreateSelect(NewCmp, NewLHS, NewRHS));
1199 return ReplaceInstUsesWith(SI, NewSI);
1205 // ABS(-X) -> ABS(X)
1208 // See if we can fold the select into a phi node if the condition is a select.
1209 if (isa<PHINode>(SI.getCondition()))
1210 // The true/false values have to be live in the PHI predecessor's blocks.
1211 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
1212 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
1213 if (Instruction *NV = FoldOpIntoPhi(SI))
1216 if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
1217 if (TrueSI->getCondition()->getType() == CondVal->getType()) {
1218 // select(C, select(C, a, b), c) -> select(C, a, c)
1219 if (TrueSI->getCondition() == CondVal) {
1220 if (SI.getTrueValue() == TrueSI->getTrueValue())
1222 SI.setOperand(1, TrueSI->getTrueValue());
1225 // select(C0, select(C1, a, b), b) -> select(C0&C1, a, b)
1226 // We choose this as normal form to enable folding on the And and shortening
1227 // paths for the values (this helps GetUnderlyingObjects() for example).
1228 if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) {
1229 Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition());
1230 SI.setOperand(0, And);
1231 SI.setOperand(1, TrueSI->getTrueValue());
1236 if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
1237 if (FalseSI->getCondition()->getType() == CondVal->getType()) {
1238 // select(C, a, select(C, b, c)) -> select(C, a, c)
1239 if (FalseSI->getCondition() == CondVal) {
1240 if (SI.getFalseValue() == FalseSI->getFalseValue())
1242 SI.setOperand(2, FalseSI->getFalseValue());
1245 // select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b)
1246 if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) {
1247 Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition());
1248 SI.setOperand(0, Or);
1249 SI.setOperand(2, FalseSI->getFalseValue());
1255 if (BinaryOperator::isNot(CondVal)) {
1256 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
1257 SI.setOperand(1, FalseVal);
1258 SI.setOperand(2, TrueVal);
1262 if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) {
1263 unsigned VWidth = VecTy->getNumElements();
1264 APInt UndefElts(VWidth, 0);
1265 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
1266 if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
1268 return ReplaceInstUsesWith(SI, V);
1272 if (isa<ConstantAggregateZero>(CondVal)) {
1273 return ReplaceInstUsesWith(SI, FalseVal);