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 "InstCombine.h"
15 #include "llvm/Support/PatternMatch.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
18 using namespace PatternMatch;
20 /// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
21 /// returning the kind and providing the out parameter results if we
22 /// successfully match.
23 static SelectPatternFlavor
24 MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
25 SelectInst *SI = dyn_cast<SelectInst>(V);
26 if (SI == 0) return SPF_UNKNOWN;
28 ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
29 if (ICI == 0) return SPF_UNKNOWN;
31 LHS = ICI->getOperand(0);
32 RHS = ICI->getOperand(1);
34 // (icmp X, Y) ? X : Y
35 if (SI->getTrueValue() == ICI->getOperand(0) &&
36 SI->getFalseValue() == ICI->getOperand(1)) {
37 switch (ICI->getPredicate()) {
38 default: return SPF_UNKNOWN; // Equality.
39 case ICmpInst::ICMP_UGT:
40 case ICmpInst::ICMP_UGE: return SPF_UMAX;
41 case ICmpInst::ICMP_SGT:
42 case ICmpInst::ICMP_SGE: return SPF_SMAX;
43 case ICmpInst::ICMP_ULT:
44 case ICmpInst::ICMP_ULE: return SPF_UMIN;
45 case ICmpInst::ICMP_SLT:
46 case ICmpInst::ICMP_SLE: return SPF_SMIN;
50 // (icmp X, Y) ? Y : X
51 if (SI->getTrueValue() == ICI->getOperand(1) &&
52 SI->getFalseValue() == ICI->getOperand(0)) {
53 switch (ICI->getPredicate()) {
54 default: return SPF_UNKNOWN; // Equality.
55 case ICmpInst::ICMP_UGT:
56 case ICmpInst::ICMP_UGE: return SPF_UMIN;
57 case ICmpInst::ICMP_SGT:
58 case ICmpInst::ICMP_SGE: return SPF_SMIN;
59 case ICmpInst::ICMP_ULT:
60 case ICmpInst::ICMP_ULE: return SPF_UMAX;
61 case ICmpInst::ICMP_SLT:
62 case ICmpInst::ICMP_SLE: return SPF_SMAX;
66 // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
72 /// GetSelectFoldableOperands - We want to turn code that looks like this:
74 /// %D = select %cond, %C, %A
76 /// %C = select %cond, %B, 0
79 /// Assuming that the specified instruction is an operand to the select, return
80 /// a bitmask indicating which operands of this instruction are foldable if they
81 /// equal the other incoming value of the select.
83 static unsigned GetSelectFoldableOperands(Instruction *I) {
84 switch (I->getOpcode()) {
85 case Instruction::Add:
86 case Instruction::Mul:
87 case Instruction::And:
89 case Instruction::Xor:
90 return 3; // Can fold through either operand.
91 case Instruction::Sub: // Can only fold on the amount subtracted.
92 case Instruction::Shl: // Can only fold on the shift amount.
93 case Instruction::LShr:
94 case Instruction::AShr:
97 return 0; // Cannot fold
101 /// GetSelectFoldableConstant - For the same transformation as the previous
102 /// function, return the identity constant that goes into the select.
103 static Constant *GetSelectFoldableConstant(Instruction *I) {
104 switch (I->getOpcode()) {
105 default: llvm_unreachable("This cannot happen!");
106 case Instruction::Add:
107 case Instruction::Sub:
108 case Instruction::Or:
109 case Instruction::Xor:
110 case Instruction::Shl:
111 case Instruction::LShr:
112 case Instruction::AShr:
113 return Constant::getNullValue(I->getType());
114 case Instruction::And:
115 return Constant::getAllOnesValue(I->getType());
116 case Instruction::Mul:
117 return ConstantInt::get(I->getType(), 1);
121 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
122 /// have the same opcode and only one use each. Try to simplify this.
123 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
125 if (TI->getNumOperands() == 1) {
126 // If this is a non-volatile load or a cast from the same type,
129 if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
132 return 0; // unknown unary op.
135 // Fold this by inserting a select from the input values.
136 SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0),
137 FI->getOperand(0), SI.getName()+".v");
138 InsertNewInstBefore(NewSI, SI);
139 return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
143 // Only handle binary operators here.
144 if (!isa<BinaryOperator>(TI))
147 // Figure out if the operations have any operands in common.
148 Value *MatchOp, *OtherOpT, *OtherOpF;
150 if (TI->getOperand(0) == FI->getOperand(0)) {
151 MatchOp = TI->getOperand(0);
152 OtherOpT = TI->getOperand(1);
153 OtherOpF = FI->getOperand(1);
154 MatchIsOpZero = true;
155 } else if (TI->getOperand(1) == FI->getOperand(1)) {
156 MatchOp = TI->getOperand(1);
157 OtherOpT = TI->getOperand(0);
158 OtherOpF = FI->getOperand(0);
159 MatchIsOpZero = false;
160 } else if (!TI->isCommutative()) {
162 } else if (TI->getOperand(0) == FI->getOperand(1)) {
163 MatchOp = TI->getOperand(0);
164 OtherOpT = TI->getOperand(1);
165 OtherOpF = FI->getOperand(0);
166 MatchIsOpZero = true;
167 } else if (TI->getOperand(1) == FI->getOperand(0)) {
168 MatchOp = TI->getOperand(1);
169 OtherOpT = TI->getOperand(0);
170 OtherOpF = FI->getOperand(1);
171 MatchIsOpZero = true;
176 // If we reach here, they do have operations in common.
177 SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT,
178 OtherOpF, SI.getName()+".v");
179 InsertNewInstBefore(NewSI, SI);
181 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
183 return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
185 return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
187 llvm_unreachable("Shouldn't get here");
191 static bool isSelect01(Constant *C1, Constant *C2) {
192 ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
195 ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
198 return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne());
201 /// FoldSelectIntoOp - Try fold the select into one of the operands to
202 /// facilitate further optimization.
203 Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
205 // See the comment above GetSelectFoldableOperands for a description of the
206 // transformation we are doing here.
207 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
208 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
209 !isa<Constant>(FalseVal)) {
210 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
211 unsigned OpToFold = 0;
212 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
214 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
219 Constant *C = GetSelectFoldableConstant(TVI);
220 Value *OOp = TVI->getOperand(2-OpToFold);
221 // Avoid creating select between 2 constants unless it's selecting
223 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
224 Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
225 InsertNewInstBefore(NewSel, SI);
226 NewSel->takeName(TVI);
227 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
228 return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
229 llvm_unreachable("Unknown instruction!!");
236 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
237 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
238 !isa<Constant>(TrueVal)) {
239 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
240 unsigned OpToFold = 0;
241 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
243 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
248 Constant *C = GetSelectFoldableConstant(FVI);
249 Value *OOp = FVI->getOperand(2-OpToFold);
250 // Avoid creating select between 2 constants unless it's selecting
252 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
253 Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
254 InsertNewInstBefore(NewSel, SI);
255 NewSel->takeName(FVI);
256 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
257 return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
258 llvm_unreachable("Unknown instruction!!");
268 /// visitSelectInstWithICmp - Visit a SelectInst that has an
269 /// ICmpInst as its first operand.
271 Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
273 bool Changed = false;
274 ICmpInst::Predicate Pred = ICI->getPredicate();
275 Value *CmpLHS = ICI->getOperand(0);
276 Value *CmpRHS = ICI->getOperand(1);
277 Value *TrueVal = SI.getTrueValue();
278 Value *FalseVal = SI.getFalseValue();
280 // Check cases where the comparison is with a constant that
281 // can be adjusted to fit the min/max idiom. We may edit ICI in
282 // place here, so make sure the select is the only user.
283 if (ICI->hasOneUse())
284 if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
287 case ICmpInst::ICMP_ULT:
288 case ICmpInst::ICMP_SLT: {
289 // X < MIN ? T : F --> F
290 if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
291 return ReplaceInstUsesWith(SI, FalseVal);
292 // X < C ? X : C-1 --> X > C-1 ? C-1 : X
293 Constant *AdjustedRHS =
294 ConstantInt::get(CI->getContext(), CI->getValue()-1);
295 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
296 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
297 Pred = ICmpInst::getSwappedPredicate(Pred);
298 CmpRHS = AdjustedRHS;
299 std::swap(FalseVal, TrueVal);
300 ICI->setPredicate(Pred);
301 ICI->setOperand(1, CmpRHS);
302 SI.setOperand(1, TrueVal);
303 SI.setOperand(2, FalseVal);
308 case ICmpInst::ICMP_UGT:
309 case ICmpInst::ICMP_SGT: {
310 // X > MAX ? T : F --> F
311 if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
312 return ReplaceInstUsesWith(SI, FalseVal);
313 // X > C ? X : C+1 --> X < C+1 ? C+1 : X
314 Constant *AdjustedRHS =
315 ConstantInt::get(CI->getContext(), CI->getValue()+1);
316 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
317 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
318 Pred = ICmpInst::getSwappedPredicate(Pred);
319 CmpRHS = AdjustedRHS;
320 std::swap(FalseVal, TrueVal);
321 ICI->setPredicate(Pred);
322 ICI->setOperand(1, CmpRHS);
323 SI.setOperand(1, TrueVal);
324 SI.setOperand(2, FalseVal);
332 // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
333 // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
334 // FIXME: Type and constness constraints could be lifted, but we have to
335 // watch code size carefully. We should consider xor instead of
336 // sub/add when we decide to do that.
337 if (const IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
338 if (TrueVal->getType() == Ty) {
339 if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
340 ConstantInt *C1 = NULL, *C2 = NULL;
341 if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
342 C1 = dyn_cast<ConstantInt>(TrueVal);
343 C2 = dyn_cast<ConstantInt>(FalseVal);
344 } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
345 C1 = dyn_cast<ConstantInt>(FalseVal);
346 C2 = dyn_cast<ConstantInt>(TrueVal);
349 // This shift results in either -1 or 0.
350 Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
352 // Check if we can express the operation with a single or.
353 if (C2->isAllOnesValue())
354 return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
356 Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
357 return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
363 if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
364 // Transform (X == Y) ? X : Y -> Y
365 if (Pred == ICmpInst::ICMP_EQ)
366 return ReplaceInstUsesWith(SI, FalseVal);
367 // Transform (X != Y) ? X : Y -> X
368 if (Pred == ICmpInst::ICMP_NE)
369 return ReplaceInstUsesWith(SI, TrueVal);
370 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
372 } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
373 // Transform (X == Y) ? Y : X -> X
374 if (Pred == ICmpInst::ICMP_EQ)
375 return ReplaceInstUsesWith(SI, FalseVal);
376 // Transform (X != Y) ? Y : X -> Y
377 if (Pred == ICmpInst::ICMP_NE)
378 return ReplaceInstUsesWith(SI, TrueVal);
379 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
381 return Changed ? &SI : 0;
385 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
386 /// PHI node (but the two may be in different blocks). See if the true/false
387 /// values (V) are live in all of the predecessor blocks of the PHI. For
388 /// example, cases like this cannot be mapped:
390 /// X = phi [ C1, BB1], [C2, BB2]
392 /// Z = select X, Y, 0
394 /// because Y is not live in BB1/BB2.
396 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
397 const SelectInst &SI) {
398 // If the value is a non-instruction value like a constant or argument, it
399 // can always be mapped.
400 const Instruction *I = dyn_cast<Instruction>(V);
401 if (I == 0) return true;
403 // If V is a PHI node defined in the same block as the condition PHI, we can
404 // map the arguments.
405 const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
407 if (const PHINode *VP = dyn_cast<PHINode>(I))
408 if (VP->getParent() == CondPHI->getParent())
411 // Otherwise, if the PHI and select are defined in the same block and if V is
412 // defined in a different block, then we can transform it.
413 if (SI.getParent() == CondPHI->getParent() &&
414 I->getParent() != CondPHI->getParent())
417 // Otherwise we have a 'hard' case and we can't tell without doing more
418 // detailed dominator based analysis, punt.
422 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
423 /// SPF2(SPF1(A, B), C)
424 Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
425 SelectPatternFlavor SPF1,
428 SelectPatternFlavor SPF2, Value *C) {
429 if (C == A || C == B) {
430 // MAX(MAX(A, B), B) -> MAX(A, B)
431 // MIN(MIN(a, b), a) -> MIN(a, b)
433 return ReplaceInstUsesWith(Outer, Inner);
435 // MAX(MIN(a, b), a) -> a
436 // MIN(MAX(a, b), a) -> a
437 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
438 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
439 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
440 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
441 return ReplaceInstUsesWith(Outer, C);
444 // TODO: MIN(MIN(A, 23), 97)
449 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
450 /// both be) and we have an icmp instruction with zero, and we have an 'and'
451 /// with the non-constant value and a power of two we can turn the select
452 /// into a shift on the result of the 'and'.
453 static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
454 ConstantInt *FalseVal,
455 InstCombiner::BuilderTy *Builder) {
456 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
457 if (!IC || !IC->isEquality())
460 if (ConstantInt *C = dyn_cast<ConstantInt>(IC->getOperand(1)))
465 Value *LHS = IC->getOperand(0);
466 if (LHS->getType() != SI.getType() ||
467 !match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
470 // If both select arms are non-zero see if we have a select of the form
471 // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
472 // for 'x ? 2^n : 0' and fix the thing up at the end.
473 ConstantInt *Offset = 0;
474 if (!TrueVal->isZero() && !FalseVal->isZero()) {
475 if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
477 else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
482 // Adjust TrueVal and FalseVal to the offset.
483 TrueVal = ConstantInt::get(Builder->getContext(),
484 TrueVal->getValue() - Offset->getValue());
485 FalseVal = ConstantInt::get(Builder->getContext(),
486 FalseVal->getValue() - Offset->getValue());
489 // Make sure the mask in the 'and' and one of the select arms is a power of 2.
490 if (!AndRHS->getValue().isPowerOf2() ||
491 (!TrueVal->getValue().isPowerOf2() &&
492 !FalseVal->getValue().isPowerOf2()))
495 // Determine which shift is needed to transform result of the 'and' into the
497 ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
498 unsigned ValZeros = ValC->getValue().logBase2();
499 unsigned AndZeros = AndRHS->getValue().logBase2();
502 if (ValZeros > AndZeros)
503 V = Builder->CreateShl(V, ValZeros - AndZeros);
504 else if (ValZeros < AndZeros)
505 V = Builder->CreateLShr(V, AndZeros - ValZeros);
507 // Okay, now we know that everything is set up, we just don't know whether we
508 // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
509 bool ShouldNotVal = !TrueVal->isZero();
510 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
512 V = Builder->CreateXor(V, ValC);
514 // Apply an offset if needed.
516 V = Builder->CreateAdd(V, Offset);
520 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
521 Value *CondVal = SI.getCondition();
522 Value *TrueVal = SI.getTrueValue();
523 Value *FalseVal = SI.getFalseValue();
525 if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
526 return ReplaceInstUsesWith(SI, V);
528 if (SI.getType()->isIntegerTy(1)) {
529 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
530 if (C->getZExtValue()) {
531 // Change: A = select B, true, C --> A = or B, C
532 return BinaryOperator::CreateOr(CondVal, FalseVal);
534 // Change: A = select B, false, C --> A = and !B, C
536 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
537 "not."+CondVal->getName()), SI);
538 return BinaryOperator::CreateAnd(NotCond, FalseVal);
539 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
540 if (C->getZExtValue() == false) {
541 // Change: A = select B, C, false --> A = and B, C
542 return BinaryOperator::CreateAnd(CondVal, TrueVal);
544 // Change: A = select B, C, true --> A = or !B, C
546 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
547 "not."+CondVal->getName()), SI);
548 return BinaryOperator::CreateOr(NotCond, TrueVal);
551 // select a, b, a -> a&b
552 // select a, a, b -> a|b
553 if (CondVal == TrueVal)
554 return BinaryOperator::CreateOr(CondVal, FalseVal);
555 else if (CondVal == FalseVal)
556 return BinaryOperator::CreateAnd(CondVal, TrueVal);
559 // Selecting between two integer constants?
560 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
561 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
562 // select C, 1, 0 -> zext C to int
563 if (FalseValC->isZero() && TrueValC->getValue() == 1)
564 return new ZExtInst(CondVal, SI.getType());
566 // select C, -1, 0 -> sext C to int
567 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
568 return new SExtInst(CondVal, SI.getType());
570 // select C, 0, 1 -> zext !C to int
571 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
572 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
573 return new ZExtInst(NotCond, SI.getType());
576 // select C, 0, -1 -> sext !C to int
577 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
578 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
579 return new SExtInst(NotCond, SI.getType());
582 if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
583 return ReplaceInstUsesWith(SI, V);
586 // See if we are selecting two values based on a comparison of the two values.
587 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
588 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
589 // Transform (X == Y) ? X : Y -> Y
590 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
591 // This is not safe in general for floating point:
592 // consider X== -0, Y== +0.
593 // It becomes safe if either operand is a nonzero constant.
594 ConstantFP *CFPt, *CFPf;
595 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
596 !CFPt->getValueAPF().isZero()) ||
597 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
598 !CFPf->getValueAPF().isZero()))
599 return ReplaceInstUsesWith(SI, FalseVal);
601 // Transform (X une Y) ? X : Y -> X
602 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
603 // This is not safe in general for floating point:
604 // consider X== -0, Y== +0.
605 // It becomes safe if either operand is a nonzero constant.
606 ConstantFP *CFPt, *CFPf;
607 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
608 !CFPt->getValueAPF().isZero()) ||
609 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
610 !CFPf->getValueAPF().isZero()))
611 return ReplaceInstUsesWith(SI, TrueVal);
613 // NOTE: if we wanted to, this is where to detect MIN/MAX
615 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
616 // Transform (X == Y) ? Y : X -> X
617 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
618 // This is not safe in general for floating point:
619 // consider X== -0, Y== +0.
620 // It becomes safe if either operand is a nonzero constant.
621 ConstantFP *CFPt, *CFPf;
622 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
623 !CFPt->getValueAPF().isZero()) ||
624 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
625 !CFPf->getValueAPF().isZero()))
626 return ReplaceInstUsesWith(SI, FalseVal);
628 // Transform (X une Y) ? Y : X -> Y
629 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
630 // This is not safe in general for floating point:
631 // consider X== -0, Y== +0.
632 // It becomes safe if either operand is a nonzero constant.
633 ConstantFP *CFPt, *CFPf;
634 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
635 !CFPt->getValueAPF().isZero()) ||
636 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
637 !CFPf->getValueAPF().isZero()))
638 return ReplaceInstUsesWith(SI, TrueVal);
640 // NOTE: if we wanted to, this is where to detect MIN/MAX
642 // NOTE: if we wanted to, this is where to detect ABS
645 // See if we are selecting two values based on a comparison of the two values.
646 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
647 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
650 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
651 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
652 if (TI->hasOneUse() && FI->hasOneUse()) {
653 Instruction *AddOp = 0, *SubOp = 0;
655 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
656 if (TI->getOpcode() == FI->getOpcode())
657 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
660 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
661 // even legal for FP.
662 if ((TI->getOpcode() == Instruction::Sub &&
663 FI->getOpcode() == Instruction::Add) ||
664 (TI->getOpcode() == Instruction::FSub &&
665 FI->getOpcode() == Instruction::FAdd)) {
666 AddOp = FI; SubOp = TI;
667 } else if ((FI->getOpcode() == Instruction::Sub &&
668 TI->getOpcode() == Instruction::Add) ||
669 (FI->getOpcode() == Instruction::FSub &&
670 TI->getOpcode() == Instruction::FAdd)) {
671 AddOp = TI; SubOp = FI;
675 Value *OtherAddOp = 0;
676 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
677 OtherAddOp = AddOp->getOperand(1);
678 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
679 OtherAddOp = AddOp->getOperand(0);
683 // So at this point we know we have (Y -> OtherAddOp):
684 // select C, (add X, Y), (sub X, Z)
685 Value *NegVal; // Compute -Z
686 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
687 NegVal = ConstantExpr::getNeg(C);
688 } else if (SI.getType()->isFloatingPointTy()) {
689 NegVal = InsertNewInstBefore(
690 BinaryOperator::CreateFNeg(SubOp->getOperand(1),
693 NegVal = InsertNewInstBefore(
694 BinaryOperator::CreateNeg(SubOp->getOperand(1),
698 Value *NewTrueOp = OtherAddOp;
699 Value *NewFalseOp = NegVal;
701 std::swap(NewTrueOp, NewFalseOp);
702 Instruction *NewSel =
703 SelectInst::Create(CondVal, NewTrueOp,
704 NewFalseOp, SI.getName() + ".p");
706 NewSel = InsertNewInstBefore(NewSel, SI);
707 if (SI.getType()->isFloatingPointTy())
708 return BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
710 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
715 // See if we can fold the select into one of our operands.
716 if (SI.getType()->isIntegerTy()) {
717 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
720 // MAX(MAX(a, b), a) -> MAX(a, b)
721 // MIN(MIN(a, b), a) -> MIN(a, b)
722 // MAX(MIN(a, b), a) -> a
723 // MIN(MAX(a, b), a) -> a
724 Value *LHS, *RHS, *LHS2, *RHS2;
725 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
726 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
727 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
730 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
731 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
738 // ABS(ABS(X)) -> ABS(X)
741 // See if we can fold the select into a phi node if the condition is a select.
742 if (isa<PHINode>(SI.getCondition()))
743 // The true/false values have to be live in the PHI predecessor's blocks.
744 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
745 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
746 if (Instruction *NV = FoldOpIntoPhi(SI))
749 if (BinaryOperator::isNot(CondVal)) {
750 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
751 SI.setOperand(1, FalseVal);
752 SI.setOperand(2, TrueVal);