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;
91 // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
97 /// GetSelectFoldableOperands - We want to turn code that looks like this:
99 /// %D = select %cond, %C, %A
101 /// %C = select %cond, %B, 0
104 /// Assuming that the specified instruction is an operand to the select, return
105 /// a bitmask indicating which operands of this instruction are foldable if they
106 /// equal the other incoming value of the select.
108 static unsigned GetSelectFoldableOperands(Instruction *I) {
109 switch (I->getOpcode()) {
110 case Instruction::Add:
111 case Instruction::Mul:
112 case Instruction::And:
113 case Instruction::Or:
114 case Instruction::Xor:
115 return 3; // Can fold through either operand.
116 case Instruction::Sub: // Can only fold on the amount subtracted.
117 case Instruction::Shl: // Can only fold on the shift amount.
118 case Instruction::LShr:
119 case Instruction::AShr:
122 return 0; // Cannot fold
126 /// GetSelectFoldableConstant - For the same transformation as the previous
127 /// function, return the identity constant that goes into the select.
128 static Constant *GetSelectFoldableConstant(Instruction *I) {
129 switch (I->getOpcode()) {
130 default: llvm_unreachable("This cannot happen!");
131 case Instruction::Add:
132 case Instruction::Sub:
133 case Instruction::Or:
134 case Instruction::Xor:
135 case Instruction::Shl:
136 case Instruction::LShr:
137 case Instruction::AShr:
138 return Constant::getNullValue(I->getType());
139 case Instruction::And:
140 return Constant::getAllOnesValue(I->getType());
141 case Instruction::Mul:
142 return ConstantInt::get(I->getType(), 1);
146 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
147 /// have the same opcode and only one use each. Try to simplify this.
148 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
150 if (TI->getNumOperands() == 1) {
151 // If this is a non-volatile load or a cast from the same type,
154 Type *FIOpndTy = FI->getOperand(0)->getType();
155 if (TI->getOperand(0)->getType() != FIOpndTy)
157 // The select condition may be a vector. We may only change the operand
158 // type if the vector width remains the same (and matches the condition).
159 Type *CondTy = SI.getCondition()->getType();
160 if (CondTy->isVectorTy() && (!FIOpndTy->isVectorTy() ||
161 CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements()))
164 return nullptr; // unknown unary op.
167 // Fold this by inserting a select from the input values.
168 Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0),
169 FI->getOperand(0), SI.getName()+".v");
170 return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
174 // Only handle binary operators here.
175 if (!isa<BinaryOperator>(TI))
178 // Figure out if the operations have any operands in common.
179 Value *MatchOp, *OtherOpT, *OtherOpF;
181 if (TI->getOperand(0) == FI->getOperand(0)) {
182 MatchOp = TI->getOperand(0);
183 OtherOpT = TI->getOperand(1);
184 OtherOpF = FI->getOperand(1);
185 MatchIsOpZero = true;
186 } else if (TI->getOperand(1) == FI->getOperand(1)) {
187 MatchOp = TI->getOperand(1);
188 OtherOpT = TI->getOperand(0);
189 OtherOpF = FI->getOperand(0);
190 MatchIsOpZero = false;
191 } else if (!TI->isCommutative()) {
193 } else if (TI->getOperand(0) == FI->getOperand(1)) {
194 MatchOp = TI->getOperand(0);
195 OtherOpT = TI->getOperand(1);
196 OtherOpF = FI->getOperand(0);
197 MatchIsOpZero = true;
198 } else if (TI->getOperand(1) == FI->getOperand(0)) {
199 MatchOp = TI->getOperand(1);
200 OtherOpT = TI->getOperand(0);
201 OtherOpF = FI->getOperand(1);
202 MatchIsOpZero = true;
207 // If we reach here, they do have operations in common.
208 Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT,
209 OtherOpF, SI.getName()+".v");
211 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
213 return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
215 return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
217 llvm_unreachable("Shouldn't get here");
220 static bool isSelect01(Constant *C1, Constant *C2) {
221 ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
224 ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
227 if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
229 return C1I->isOne() || C1I->isAllOnesValue() ||
230 C2I->isOne() || C2I->isAllOnesValue();
233 /// FoldSelectIntoOp - Try fold the select into one of the operands to
234 /// facilitate further optimization.
235 Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
237 // See the comment above GetSelectFoldableOperands for a description of the
238 // transformation we are doing here.
239 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
240 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
241 !isa<Constant>(FalseVal)) {
242 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
243 unsigned OpToFold = 0;
244 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
246 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
251 Constant *C = GetSelectFoldableConstant(TVI);
252 Value *OOp = TVI->getOperand(2-OpToFold);
253 // Avoid creating select between 2 constants unless it's selecting
254 // between 0, 1 and -1.
255 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
256 Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C);
257 NewSel->takeName(TVI);
258 BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI);
259 BinaryOperator *BO = BinaryOperator::Create(TVI_BO->getOpcode(),
261 if (isa<PossiblyExactOperator>(BO))
262 BO->setIsExact(TVI_BO->isExact());
263 if (isa<OverflowingBinaryOperator>(BO)) {
264 BO->setHasNoUnsignedWrap(TVI_BO->hasNoUnsignedWrap());
265 BO->setHasNoSignedWrap(TVI_BO->hasNoSignedWrap());
274 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
275 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
276 !isa<Constant>(TrueVal)) {
277 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
278 unsigned OpToFold = 0;
279 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
281 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
286 Constant *C = GetSelectFoldableConstant(FVI);
287 Value *OOp = FVI->getOperand(2-OpToFold);
288 // Avoid creating select between 2 constants unless it's selecting
289 // between 0, 1 and -1.
290 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
291 Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp);
292 NewSel->takeName(FVI);
293 BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI);
294 BinaryOperator *BO = BinaryOperator::Create(FVI_BO->getOpcode(),
296 if (isa<PossiblyExactOperator>(BO))
297 BO->setIsExact(FVI_BO->isExact());
298 if (isa<OverflowingBinaryOperator>(BO)) {
299 BO->setHasNoUnsignedWrap(FVI_BO->hasNoUnsignedWrap());
300 BO->setHasNoSignedWrap(FVI_BO->hasNoSignedWrap());
312 /// SimplifyWithOpReplaced - See if V simplifies when its operand Op is
313 /// replaced with RepOp.
314 static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
315 const DataLayout *TD,
316 const TargetLibraryInfo *TLI,
317 DominatorTree *DT, AssumptionCache *AC) {
318 // Trivial replacement.
322 Instruction *I = dyn_cast<Instruction>(V);
326 // If this is a binary operator, try to simplify it with the replaced op.
327 if (BinaryOperator *B = dyn_cast<BinaryOperator>(I)) {
328 if (B->getOperand(0) == Op)
329 return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), TD, TLI);
330 if (B->getOperand(1) == Op)
331 return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, TD, TLI);
334 // Same for CmpInsts.
335 if (CmpInst *C = dyn_cast<CmpInst>(I)) {
336 if (C->getOperand(0) == Op)
337 return SimplifyCmpInst(C->getPredicate(), RepOp, C->getOperand(1), TD,
339 if (C->getOperand(1) == Op)
340 return SimplifyCmpInst(C->getPredicate(), C->getOperand(0), RepOp, TD,
344 // TODO: We could hand off more cases to instsimplify here.
346 // If all operands are constant after substituting Op for RepOp then we can
347 // constant fold the instruction.
348 if (Constant *CRepOp = dyn_cast<Constant>(RepOp)) {
349 // Build a list of all constant operands.
350 SmallVector<Constant*, 8> ConstOps;
351 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
352 if (I->getOperand(i) == Op)
353 ConstOps.push_back(CRepOp);
354 else if (Constant *COp = dyn_cast<Constant>(I->getOperand(i)))
355 ConstOps.push_back(COp);
360 // All operands were constants, fold it.
361 if (ConstOps.size() == I->getNumOperands()) {
362 if (CmpInst *C = dyn_cast<CmpInst>(I))
363 return ConstantFoldCompareInstOperands(C->getPredicate(), ConstOps[0],
364 ConstOps[1], TD, TLI);
366 if (LoadInst *LI = dyn_cast<LoadInst>(I))
367 if (!LI->isVolatile())
368 return ConstantFoldLoadFromConstPtr(ConstOps[0], TD);
370 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
378 /// foldSelectICmpAndOr - We want to turn:
379 /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2))
381 /// (or (shl (and X, C1), C3), y)
383 /// C1 and C2 are both powers of 2
385 /// C3 = Log(C2) - Log(C1)
387 /// This transform handles cases where:
388 /// 1. The icmp predicate is inverted
389 /// 2. The select operands are reversed
390 /// 3. The magnitude of C2 and C1 are flipped
391 static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
393 InstCombiner::BuilderTy *Builder) {
394 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
395 if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
398 Value *CmpLHS = IC->getOperand(0);
399 Value *CmpRHS = IC->getOperand(1);
401 if (!match(CmpRHS, m_Zero()))
406 if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1))))
410 bool OrOnTrueVal = false;
411 bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
413 OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)));
415 if (!OrOnFalseVal && !OrOnTrueVal)
419 Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
421 unsigned C1Log = C1->logBase2();
422 unsigned C2Log = C2->logBase2();
424 V = Builder->CreateZExtOrTrunc(V, Y->getType());
425 V = Builder->CreateShl(V, C2Log - C1Log);
426 } else if (C1Log > C2Log) {
427 V = Builder->CreateLShr(V, C1Log - C2Log);
428 V = Builder->CreateZExtOrTrunc(V, Y->getType());
430 V = Builder->CreateZExtOrTrunc(V, Y->getType());
432 ICmpInst::Predicate Pred = IC->getPredicate();
433 if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) ||
434 (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal))
435 V = Builder->CreateXor(V, *C2);
437 return Builder->CreateOr(V, Y);
440 /// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single
441 /// call to cttz/ctlz with flag 'is_zero_undef' cleared.
443 /// For example, we can fold the following code sequence:
445 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
446 /// %1 = icmp ne i32 %x, 0
447 /// %2 = select i1 %1, i32 %0, i32 32
451 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
452 static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
453 InstCombiner::BuilderTy *Builder) {
454 ICmpInst::Predicate Pred = ICI->getPredicate();
455 Value *CmpLHS = ICI->getOperand(0);
456 Value *CmpRHS = ICI->getOperand(1);
458 // Check if the condition value compares a value for equality against zero.
459 if (!ICI->isEquality() || !match(CmpRHS, m_Zero()))
462 Value *Count = FalseVal;
463 Value *ValueOnZero = TrueVal;
464 if (Pred == ICmpInst::ICMP_NE)
465 std::swap(Count, ValueOnZero);
467 // Skip zero extend/truncate.
469 if (match(Count, m_ZExt(m_Value(V))) ||
470 match(Count, m_Trunc(m_Value(V))))
473 // Check if the value propagated on zero is a constant number equal to the
474 // sizeof in bits of 'Count'.
475 unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits();
476 if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits)))
479 // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the
480 // input to the cttz/ctlz is used as LHS for the compare instruction.
481 if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) ||
482 match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) {
483 IntrinsicInst *II = cast<IntrinsicInst>(Count);
484 IRBuilder<> Builder(II);
485 if (cast<ConstantInt>(II->getArgOperand(1))->isOne()) {
486 // Explicitly clear the 'undef_on_zero' flag.
487 IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone());
488 Type *Ty = NewI->getArgOperand(1)->getType();
489 NewI->setArgOperand(1, Constant::getNullValue(Ty));
490 Builder.Insert(NewI);
494 return Builder.CreateZExtOrTrunc(Count, ValueOnZero->getType());
500 /// visitSelectInstWithICmp - Visit a SelectInst that has an
501 /// ICmpInst as its first operand.
503 Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
505 bool Changed = false;
506 ICmpInst::Predicate Pred = ICI->getPredicate();
507 Value *CmpLHS = ICI->getOperand(0);
508 Value *CmpRHS = ICI->getOperand(1);
509 Value *TrueVal = SI.getTrueValue();
510 Value *FalseVal = SI.getFalseValue();
512 // Check cases where the comparison is with a constant that
513 // can be adjusted to fit the min/max idiom. We may move or edit ICI
514 // here, so make sure the select is the only user.
515 if (ICI->hasOneUse())
516 if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
517 // X < MIN ? T : F --> F
518 if ((Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_ULT)
519 && CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
520 return ReplaceInstUsesWith(SI, FalseVal);
521 // X > MAX ? T : F --> F
522 else if ((Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_UGT)
523 && CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
524 return ReplaceInstUsesWith(SI, FalseVal);
527 case ICmpInst::ICMP_ULT:
528 case ICmpInst::ICMP_SLT:
529 case ICmpInst::ICMP_UGT:
530 case ICmpInst::ICMP_SGT: {
531 // These transformations only work for selects over integers.
532 IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
536 Constant *AdjustedRHS;
537 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
538 AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
539 else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
540 AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
542 // X > C ? X : C+1 --> X < C+1 ? C+1 : X
543 // X < C ? X : C-1 --> X > C-1 ? C-1 : X
544 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
545 (CmpLHS == FalseVal && AdjustedRHS == TrueVal))
546 ; // Nothing to do here. Values match without any sign/zero extension.
548 // Types do not match. Instead of calculating this with mixed types
549 // promote all to the larger type. This enables scalar evolution to
550 // analyze this expression.
551 else if (CmpRHS->getType()->getScalarSizeInBits()
552 < SelectTy->getBitWidth()) {
553 Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
555 // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
556 // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
557 // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
558 // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
559 if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
560 sextRHS == FalseVal) {
562 AdjustedRHS = sextRHS;
563 } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
564 sextRHS == TrueVal) {
566 AdjustedRHS = sextRHS;
567 } else if (ICI->isUnsigned()) {
568 Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy);
569 // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
570 // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
571 // zext + signed compare cannot be changed:
572 // 0xff <s 0x00, but 0x00ff >s 0x0000
573 if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
574 zextRHS == FalseVal) {
576 AdjustedRHS = zextRHS;
577 } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
578 zextRHS == TrueVal) {
580 AdjustedRHS = zextRHS;
588 Pred = ICmpInst::getSwappedPredicate(Pred);
589 CmpRHS = AdjustedRHS;
590 std::swap(FalseVal, TrueVal);
591 ICI->setPredicate(Pred);
592 ICI->setOperand(0, CmpLHS);
593 ICI->setOperand(1, CmpRHS);
594 SI.setOperand(1, TrueVal);
595 SI.setOperand(2, FalseVal);
597 // Move ICI instruction right before the select instruction. Otherwise
598 // the sext/zext value may be defined after the ICI instruction uses it.
599 ICI->moveBefore(&SI);
607 // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
608 // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
609 // FIXME: Type and constness constraints could be lifted, but we have to
610 // watch code size carefully. We should consider xor instead of
611 // sub/add when we decide to do that.
612 if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
613 if (TrueVal->getType() == Ty) {
614 if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
615 ConstantInt *C1 = nullptr, *C2 = nullptr;
616 if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
617 C1 = dyn_cast<ConstantInt>(TrueVal);
618 C2 = dyn_cast<ConstantInt>(FalseVal);
619 } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
620 C1 = dyn_cast<ConstantInt>(FalseVal);
621 C2 = dyn_cast<ConstantInt>(TrueVal);
624 // This shift results in either -1 or 0.
625 Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
627 // Check if we can express the operation with a single or.
628 if (C2->isAllOnesValue())
629 return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
631 Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
632 return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
638 // If we have an equality comparison then we know the value in one of the
639 // arms of the select. See if substituting this value into the arm and
640 // simplifying the result yields the same value as the other arm.
641 if (Pred == ICmpInst::ICMP_EQ) {
642 if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
644 SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
646 return ReplaceInstUsesWith(SI, FalseVal);
647 if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
649 SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
651 return ReplaceInstUsesWith(SI, FalseVal);
652 } else if (Pred == ICmpInst::ICMP_NE) {
653 if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
655 SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
657 return ReplaceInstUsesWith(SI, TrueVal);
658 if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, DL, TLI, DT, AC) ==
660 SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, DL, TLI, DT, AC) ==
662 return ReplaceInstUsesWith(SI, TrueVal);
665 // NOTE: if we wanted to, this is where to detect integer MIN/MAX
667 if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) {
668 if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
669 // Transform (X == C) ? X : Y -> (X == C) ? C : Y
670 SI.setOperand(1, CmpRHS);
672 } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) {
673 // Transform (X != C) ? Y : X -> (X != C) ? Y : C
674 SI.setOperand(2, CmpRHS);
679 if (unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits()) {
680 APInt MinSignedValue = APInt::getSignBit(BitWidth);
684 bool IsBitTest = false;
685 if (ICmpInst::isEquality(Pred) &&
686 match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
687 match(CmpRHS, m_Zero())) {
689 TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
690 } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
694 TrueWhenUnset = false;
695 } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
699 TrueWhenUnset = true;
703 // (X & Y) == 0 ? X : X ^ Y --> X & ~Y
704 if (TrueWhenUnset && TrueVal == X &&
705 match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
706 V = Builder->CreateAnd(X, ~(*Y));
707 // (X & Y) != 0 ? X ^ Y : X --> X & ~Y
708 else if (!TrueWhenUnset && FalseVal == X &&
709 match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
710 V = Builder->CreateAnd(X, ~(*Y));
711 // (X & Y) == 0 ? X ^ Y : X --> X | Y
712 else if (TrueWhenUnset && FalseVal == X &&
713 match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
714 V = Builder->CreateOr(X, *Y);
715 // (X & Y) != 0 ? X : X ^ Y --> X | Y
716 else if (!TrueWhenUnset && TrueVal == X &&
717 match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
718 V = Builder->CreateOr(X, *Y);
721 return ReplaceInstUsesWith(SI, V);
725 if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
726 return ReplaceInstUsesWith(SI, V);
728 if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder))
729 return ReplaceInstUsesWith(SI, V);
731 return Changed ? &SI : nullptr;
735 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
736 /// PHI node (but the two may be in different blocks). See if the true/false
737 /// values (V) are live in all of the predecessor blocks of the PHI. For
738 /// example, cases like this cannot be mapped:
740 /// X = phi [ C1, BB1], [C2, BB2]
742 /// Z = select X, Y, 0
744 /// because Y is not live in BB1/BB2.
746 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
747 const SelectInst &SI) {
748 // If the value is a non-instruction value like a constant or argument, it
749 // can always be mapped.
750 const Instruction *I = dyn_cast<Instruction>(V);
753 // If V is a PHI node defined in the same block as the condition PHI, we can
754 // map the arguments.
755 const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
757 if (const PHINode *VP = dyn_cast<PHINode>(I))
758 if (VP->getParent() == CondPHI->getParent())
761 // Otherwise, if the PHI and select are defined in the same block and if V is
762 // defined in a different block, then we can transform it.
763 if (SI.getParent() == CondPHI->getParent() &&
764 I->getParent() != CondPHI->getParent())
767 // Otherwise we have a 'hard' case and we can't tell without doing more
768 // detailed dominator based analysis, punt.
772 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
773 /// SPF2(SPF1(A, B), C)
774 Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
775 SelectPatternFlavor SPF1,
778 SelectPatternFlavor SPF2, Value *C) {
779 if (C == A || C == B) {
780 // MAX(MAX(A, B), B) -> MAX(A, B)
781 // MIN(MIN(a, b), a) -> MIN(a, b)
783 return ReplaceInstUsesWith(Outer, Inner);
785 // MAX(MIN(a, b), a) -> a
786 // MIN(MAX(a, b), a) -> a
787 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
788 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
789 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
790 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
791 return ReplaceInstUsesWith(Outer, C);
795 if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) {
796 if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) {
797 APInt ACB = CB->getValue();
798 APInt ACC = CC->getValue();
800 // MIN(MIN(A, 23), 97) -> MIN(A, 23)
801 // MAX(MAX(A, 97), 23) -> MAX(A, 97)
802 if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) ||
803 (SPF1 == SPF_SMIN && ACB.sle(ACC)) ||
804 (SPF1 == SPF_UMAX && ACB.uge(ACC)) ||
805 (SPF1 == SPF_SMAX && ACB.sge(ACC)))
806 return ReplaceInstUsesWith(Outer, Inner);
808 // MIN(MIN(A, 97), 23) -> MIN(A, 23)
809 // MAX(MAX(A, 23), 97) -> MAX(A, 97)
810 if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) ||
811 (SPF1 == SPF_SMIN && ACB.sgt(ACC)) ||
812 (SPF1 == SPF_UMAX && ACB.ult(ACC)) ||
813 (SPF1 == SPF_SMAX && ACB.slt(ACC))) {
814 Outer.replaceUsesOfWith(Inner, A);
821 // ABS(ABS(X)) -> ABS(X)
822 // NABS(NABS(X)) -> NABS(X)
823 if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) {
824 return ReplaceInstUsesWith(Outer, Inner);
827 // ABS(NABS(X)) -> ABS(X)
828 // NABS(ABS(X)) -> NABS(X)
829 if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) ||
830 (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) {
831 SelectInst *SI = cast<SelectInst>(Inner);
832 Value *NewSI = Builder->CreateSelect(
833 SI->getCondition(), SI->getFalseValue(), SI->getTrueValue());
834 return ReplaceInstUsesWith(Outer, NewSI);
839 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
840 /// both be) and we have an icmp instruction with zero, and we have an 'and'
841 /// with the non-constant value and a power of two we can turn the select
842 /// into a shift on the result of the 'and'.
843 static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
844 ConstantInt *FalseVal,
845 InstCombiner::BuilderTy *Builder) {
846 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
847 if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
850 if (!match(IC->getOperand(1), m_Zero()))
854 Value *LHS = IC->getOperand(0);
855 if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
858 // If both select arms are non-zero see if we have a select of the form
859 // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
860 // for 'x ? 2^n : 0' and fix the thing up at the end.
861 ConstantInt *Offset = nullptr;
862 if (!TrueVal->isZero() && !FalseVal->isZero()) {
863 if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
865 else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
870 // Adjust TrueVal and FalseVal to the offset.
871 TrueVal = ConstantInt::get(Builder->getContext(),
872 TrueVal->getValue() - Offset->getValue());
873 FalseVal = ConstantInt::get(Builder->getContext(),
874 FalseVal->getValue() - Offset->getValue());
877 // Make sure the mask in the 'and' and one of the select arms is a power of 2.
878 if (!AndRHS->getValue().isPowerOf2() ||
879 (!TrueVal->getValue().isPowerOf2() &&
880 !FalseVal->getValue().isPowerOf2()))
883 // Determine which shift is needed to transform result of the 'and' into the
885 ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
886 unsigned ValZeros = ValC->getValue().logBase2();
887 unsigned AndZeros = AndRHS->getValue().logBase2();
889 // If types don't match we can still convert the select by introducing a zext
890 // or a trunc of the 'and'. The trunc case requires that all of the truncated
891 // bits are zero, we can figure that out by looking at the 'and' mask.
892 if (AndZeros >= ValC->getBitWidth())
895 Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
896 if (ValZeros > AndZeros)
897 V = Builder->CreateShl(V, ValZeros - AndZeros);
898 else if (ValZeros < AndZeros)
899 V = Builder->CreateLShr(V, AndZeros - ValZeros);
901 // Okay, now we know that everything is set up, we just don't know whether we
902 // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
903 bool ShouldNotVal = !TrueVal->isZero();
904 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
906 V = Builder->CreateXor(V, ValC);
908 // Apply an offset if needed.
910 V = Builder->CreateAdd(V, Offset);
914 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
915 Value *CondVal = SI.getCondition();
916 Value *TrueVal = SI.getTrueValue();
917 Value *FalseVal = SI.getFalseValue();
920 SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC))
921 return ReplaceInstUsesWith(SI, V);
923 if (SI.getType()->isIntegerTy(1)) {
924 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
925 if (C->getZExtValue()) {
926 // Change: A = select B, true, C --> A = or B, C
927 return BinaryOperator::CreateOr(CondVal, FalseVal);
929 // Change: A = select B, false, C --> A = and !B, C
930 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
931 return BinaryOperator::CreateAnd(NotCond, FalseVal);
933 if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
934 if (C->getZExtValue() == false) {
935 // Change: A = select B, C, false --> A = and B, C
936 return BinaryOperator::CreateAnd(CondVal, TrueVal);
938 // Change: A = select B, C, true --> A = or !B, C
939 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
940 return BinaryOperator::CreateOr(NotCond, TrueVal);
943 // select a, b, a -> a&b
944 // select a, a, b -> a|b
945 if (CondVal == TrueVal)
946 return BinaryOperator::CreateOr(CondVal, FalseVal);
947 if (CondVal == FalseVal)
948 return BinaryOperator::CreateAnd(CondVal, TrueVal);
950 // select a, ~a, b -> (~a)&b
951 // select a, b, ~a -> (~a)|b
952 if (match(TrueVal, m_Not(m_Specific(CondVal))))
953 return BinaryOperator::CreateAnd(TrueVal, FalseVal);
954 if (match(FalseVal, m_Not(m_Specific(CondVal))))
955 return BinaryOperator::CreateOr(TrueVal, FalseVal);
958 // Selecting between two integer constants?
959 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
960 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
961 // select C, 1, 0 -> zext C to int
962 if (FalseValC->isZero() && TrueValC->getValue() == 1)
963 return new ZExtInst(CondVal, SI.getType());
965 // select C, -1, 0 -> sext C to int
966 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
967 return new SExtInst(CondVal, SI.getType());
969 // select C, 0, 1 -> zext !C to int
970 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
971 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
972 return new ZExtInst(NotCond, SI.getType());
975 // select C, 0, -1 -> sext !C to int
976 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
977 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
978 return new SExtInst(NotCond, SI.getType());
981 if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
982 return ReplaceInstUsesWith(SI, V);
985 // See if we are selecting two values based on a comparison of the two values.
986 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
987 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
988 // Transform (X == Y) ? X : Y -> Y
989 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
990 // This is not safe in general for floating point:
991 // consider X== -0, Y== +0.
992 // It becomes safe if either operand is a nonzero constant.
993 ConstantFP *CFPt, *CFPf;
994 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
995 !CFPt->getValueAPF().isZero()) ||
996 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
997 !CFPf->getValueAPF().isZero()))
998 return ReplaceInstUsesWith(SI, FalseVal);
1000 // Transform (X une Y) ? X : Y -> X
1001 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
1002 // This is not safe in general for floating point:
1003 // consider X== -0, Y== +0.
1004 // It becomes safe if either operand is a nonzero constant.
1005 ConstantFP *CFPt, *CFPf;
1006 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1007 !CFPt->getValueAPF().isZero()) ||
1008 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1009 !CFPf->getValueAPF().isZero()))
1010 return ReplaceInstUsesWith(SI, TrueVal);
1013 // Canonicalize to use ordered comparisons by swapping the select
1017 // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
1018 if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
1019 FCmpInst::Predicate InvPred = FCI->getInversePredicate();
1020 Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
1021 FCI->getName() + ".inv");
1023 return SelectInst::Create(NewCond, FalseVal, TrueVal,
1024 SI.getName() + ".p");
1027 // NOTE: if we wanted to, this is where to detect MIN/MAX
1028 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
1029 // Transform (X == Y) ? Y : X -> X
1030 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
1031 // This is not safe in general for floating point:
1032 // consider X== -0, Y== +0.
1033 // It becomes safe if either operand is a nonzero constant.
1034 ConstantFP *CFPt, *CFPf;
1035 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1036 !CFPt->getValueAPF().isZero()) ||
1037 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1038 !CFPf->getValueAPF().isZero()))
1039 return ReplaceInstUsesWith(SI, FalseVal);
1041 // Transform (X une Y) ? Y : X -> Y
1042 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
1043 // This is not safe in general for floating point:
1044 // consider X== -0, Y== +0.
1045 // It becomes safe if either operand is a nonzero constant.
1046 ConstantFP *CFPt, *CFPf;
1047 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
1048 !CFPt->getValueAPF().isZero()) ||
1049 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
1050 !CFPf->getValueAPF().isZero()))
1051 return ReplaceInstUsesWith(SI, TrueVal);
1054 // Canonicalize to use ordered comparisons by swapping the select
1058 // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
1059 if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
1060 FCmpInst::Predicate InvPred = FCI->getInversePredicate();
1061 Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
1062 FCI->getName() + ".inv");
1064 return SelectInst::Create(NewCond, FalseVal, TrueVal,
1065 SI.getName() + ".p");
1068 // NOTE: if we wanted to, this is where to detect MIN/MAX
1070 // NOTE: if we wanted to, this is where to detect ABS
1073 // See if we are selecting two values based on a comparison of the two values.
1074 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
1075 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
1078 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
1079 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
1080 if (TI->hasOneUse() && FI->hasOneUse()) {
1081 Instruction *AddOp = nullptr, *SubOp = nullptr;
1083 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
1084 if (TI->getOpcode() == FI->getOpcode())
1085 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
1088 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
1089 // even legal for FP.
1090 if ((TI->getOpcode() == Instruction::Sub &&
1091 FI->getOpcode() == Instruction::Add) ||
1092 (TI->getOpcode() == Instruction::FSub &&
1093 FI->getOpcode() == Instruction::FAdd)) {
1094 AddOp = FI; SubOp = TI;
1095 } else if ((FI->getOpcode() == Instruction::Sub &&
1096 TI->getOpcode() == Instruction::Add) ||
1097 (FI->getOpcode() == Instruction::FSub &&
1098 TI->getOpcode() == Instruction::FAdd)) {
1099 AddOp = TI; SubOp = FI;
1103 Value *OtherAddOp = nullptr;
1104 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
1105 OtherAddOp = AddOp->getOperand(1);
1106 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
1107 OtherAddOp = AddOp->getOperand(0);
1111 // So at this point we know we have (Y -> OtherAddOp):
1112 // select C, (add X, Y), (sub X, Z)
1113 Value *NegVal; // Compute -Z
1114 if (SI.getType()->isFPOrFPVectorTy()) {
1115 NegVal = Builder->CreateFNeg(SubOp->getOperand(1));
1116 if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) {
1117 FastMathFlags Flags = AddOp->getFastMathFlags();
1118 Flags &= SubOp->getFastMathFlags();
1119 NegInst->setFastMathFlags(Flags);
1122 NegVal = Builder->CreateNeg(SubOp->getOperand(1));
1125 Value *NewTrueOp = OtherAddOp;
1126 Value *NewFalseOp = NegVal;
1128 std::swap(NewTrueOp, NewFalseOp);
1130 Builder->CreateSelect(CondVal, NewTrueOp,
1131 NewFalseOp, SI.getName() + ".p");
1133 if (SI.getType()->isFPOrFPVectorTy()) {
1135 BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
1137 FastMathFlags Flags = AddOp->getFastMathFlags();
1138 Flags &= SubOp->getFastMathFlags();
1139 RI->setFastMathFlags(Flags);
1142 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
1147 // See if we can fold the select into one of our operands.
1148 if (SI.getType()->isIntegerTy()) {
1149 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
1152 // MAX(MAX(a, b), a) -> MAX(a, b)
1153 // MIN(MIN(a, b), a) -> MIN(a, b)
1154 // MAX(MIN(a, b), a) -> a
1155 // MIN(MAX(a, b), a) -> a
1156 Value *LHS, *RHS, *LHS2, *RHS2;
1157 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
1158 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
1159 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
1162 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
1163 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
1169 // ABS(-X) -> ABS(X)
1172 // See if we can fold the select into a phi node if the condition is a select.
1173 if (isa<PHINode>(SI.getCondition()))
1174 // The true/false values have to be live in the PHI predecessor's blocks.
1175 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
1176 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
1177 if (Instruction *NV = FoldOpIntoPhi(SI))
1180 if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
1181 // select(C, select(C, a, b), c) -> select(C, a, c)
1182 if (TrueSI->getCondition() == CondVal) {
1183 if (SI.getTrueValue() == TrueSI->getTrueValue())
1185 SI.setOperand(1, TrueSI->getTrueValue());
1188 // select(C0, select(C1, a, b), b) -> select(C0&C1, a, b)
1189 // We choose this as normal form to enable folding on the And and shortening
1190 // paths for the values (this helps GetUnderlyingObjects() for example).
1191 if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) {
1192 Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition());
1193 SI.setOperand(0, And);
1194 SI.setOperand(1, TrueSI->getTrueValue());
1198 if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
1199 // select(C, a, select(C, b, c)) -> select(C, a, c)
1200 if (FalseSI->getCondition() == CondVal) {
1201 if (SI.getFalseValue() == FalseSI->getFalseValue())
1203 SI.setOperand(2, FalseSI->getFalseValue());
1206 // select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b)
1207 if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) {
1208 Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition());
1209 SI.setOperand(0, Or);
1210 SI.setOperand(2, FalseSI->getFalseValue());
1215 if (BinaryOperator::isNot(CondVal)) {
1216 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
1217 SI.setOperand(1, FalseVal);
1218 SI.setOperand(2, TrueVal);
1222 if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) {
1223 unsigned VWidth = VecTy->getNumElements();
1224 APInt UndefElts(VWidth, 0);
1225 APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
1226 if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
1228 return ReplaceInstUsesWith(SI, V);
1232 if (isa<ConstantAggregateZero>(CondVal)) {
1233 return ReplaceInstUsesWith(SI, FalseVal);