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)
451 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
452 Value *CondVal = SI.getCondition();
453 Value *TrueVal = SI.getTrueValue();
454 Value *FalseVal = SI.getFalseValue();
456 if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
457 return ReplaceInstUsesWith(SI, V);
459 if (SI.getType()->isIntegerTy(1)) {
460 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
461 if (C->getZExtValue()) {
462 // Change: A = select B, true, C --> A = or B, C
463 return BinaryOperator::CreateOr(CondVal, FalseVal);
465 // Change: A = select B, false, C --> A = and !B, C
467 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
468 "not."+CondVal->getName()), SI);
469 return BinaryOperator::CreateAnd(NotCond, FalseVal);
470 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
471 if (C->getZExtValue() == false) {
472 // Change: A = select B, C, false --> A = and B, C
473 return BinaryOperator::CreateAnd(CondVal, TrueVal);
475 // Change: A = select B, C, true --> A = or !B, C
477 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
478 "not."+CondVal->getName()), SI);
479 return BinaryOperator::CreateOr(NotCond, TrueVal);
482 // select a, b, a -> a&b
483 // select a, a, b -> a|b
484 if (CondVal == TrueVal)
485 return BinaryOperator::CreateOr(CondVal, FalseVal);
486 else if (CondVal == FalseVal)
487 return BinaryOperator::CreateAnd(CondVal, TrueVal);
490 // Selecting between two integer constants?
491 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
492 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
493 // select C, 1, 0 -> zext C to int
494 if (FalseValC->isZero() && TrueValC->getValue() == 1)
495 return new ZExtInst(CondVal, SI.getType());
497 // select C, -1, 0 -> sext C to int
498 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
499 return new SExtInst(CondVal, SI.getType());
501 // select C, 0, 1 -> zext !C to int
502 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
503 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
504 return new ZExtInst(NotCond, SI.getType());
507 // select C, 0, -1 -> sext !C to int
508 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
509 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
510 return new SExtInst(NotCond, SI.getType());
513 if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
514 // If one of the constants is zero (we know they can't both be) and we
515 // have an icmp instruction with zero, and we have an 'and' with the
516 // non-constant value, eliminate this whole mess. This corresponds to
517 // cases like this: ((X & 27) ? 27 : 0)
518 if (TrueValC->isZero() || FalseValC->isZero())
519 if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
520 cast<Constant>(IC->getOperand(1))->isNullValue())
521 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
522 if (ICA->getOpcode() == Instruction::And &&
523 isa<ConstantInt>(ICA->getOperand(1)) &&
524 (ICA->getOperand(1) == TrueValC ||
525 ICA->getOperand(1) == FalseValC) &&
526 cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) {
527 // Okay, now we know that everything is set up, we just don't
528 // know whether we have a icmp_ne or icmp_eq and whether the
529 // true or false val is the zero.
530 bool ShouldNotVal = !TrueValC->isZero();
531 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
534 V = Builder->CreateXor(V, ICA->getOperand(1));
535 return ReplaceInstUsesWith(SI, V);
540 // See if we are selecting two values based on a comparison of the two values.
541 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
542 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
543 // Transform (X == Y) ? X : Y -> Y
544 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
545 // This is not safe in general for floating point:
546 // consider X== -0, Y== +0.
547 // It becomes safe if either operand is a nonzero constant.
548 ConstantFP *CFPt, *CFPf;
549 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
550 !CFPt->getValueAPF().isZero()) ||
551 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
552 !CFPf->getValueAPF().isZero()))
553 return ReplaceInstUsesWith(SI, FalseVal);
555 // Transform (X une Y) ? X : Y -> X
556 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
557 // This is not safe in general for floating point:
558 // consider X== -0, Y== +0.
559 // It becomes safe if either operand is a nonzero constant.
560 ConstantFP *CFPt, *CFPf;
561 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
562 !CFPt->getValueAPF().isZero()) ||
563 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
564 !CFPf->getValueAPF().isZero()))
565 return ReplaceInstUsesWith(SI, TrueVal);
567 // NOTE: if we wanted to, this is where to detect MIN/MAX
569 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
570 // Transform (X == Y) ? Y : X -> X
571 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
572 // This is not safe in general for floating point:
573 // consider X== -0, Y== +0.
574 // It becomes safe if either operand is a nonzero constant.
575 ConstantFP *CFPt, *CFPf;
576 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
577 !CFPt->getValueAPF().isZero()) ||
578 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
579 !CFPf->getValueAPF().isZero()))
580 return ReplaceInstUsesWith(SI, FalseVal);
582 // Transform (X une Y) ? Y : X -> Y
583 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
584 // This is not safe in general for floating point:
585 // consider X== -0, Y== +0.
586 // It becomes safe if either operand is a nonzero constant.
587 ConstantFP *CFPt, *CFPf;
588 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
589 !CFPt->getValueAPF().isZero()) ||
590 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
591 !CFPf->getValueAPF().isZero()))
592 return ReplaceInstUsesWith(SI, TrueVal);
594 // NOTE: if we wanted to, this is where to detect MIN/MAX
596 // NOTE: if we wanted to, this is where to detect ABS
599 // See if we are selecting two values based on a comparison of the two values.
600 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
601 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
604 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
605 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
606 if (TI->hasOneUse() && FI->hasOneUse()) {
607 Instruction *AddOp = 0, *SubOp = 0;
609 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
610 if (TI->getOpcode() == FI->getOpcode())
611 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
614 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
615 // even legal for FP.
616 if ((TI->getOpcode() == Instruction::Sub &&
617 FI->getOpcode() == Instruction::Add) ||
618 (TI->getOpcode() == Instruction::FSub &&
619 FI->getOpcode() == Instruction::FAdd)) {
620 AddOp = FI; SubOp = TI;
621 } else if ((FI->getOpcode() == Instruction::Sub &&
622 TI->getOpcode() == Instruction::Add) ||
623 (FI->getOpcode() == Instruction::FSub &&
624 TI->getOpcode() == Instruction::FAdd)) {
625 AddOp = TI; SubOp = FI;
629 Value *OtherAddOp = 0;
630 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
631 OtherAddOp = AddOp->getOperand(1);
632 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
633 OtherAddOp = AddOp->getOperand(0);
637 // So at this point we know we have (Y -> OtherAddOp):
638 // select C, (add X, Y), (sub X, Z)
639 Value *NegVal; // Compute -Z
640 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
641 NegVal = ConstantExpr::getNeg(C);
643 NegVal = InsertNewInstBefore(
644 BinaryOperator::CreateNeg(SubOp->getOperand(1),
648 Value *NewTrueOp = OtherAddOp;
649 Value *NewFalseOp = NegVal;
651 std::swap(NewTrueOp, NewFalseOp);
652 Instruction *NewSel =
653 SelectInst::Create(CondVal, NewTrueOp,
654 NewFalseOp, SI.getName() + ".p");
656 NewSel = InsertNewInstBefore(NewSel, SI);
657 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
662 // See if we can fold the select into one of our operands.
663 if (SI.getType()->isIntegerTy()) {
664 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
667 // MAX(MAX(a, b), a) -> MAX(a, b)
668 // MIN(MIN(a, b), a) -> MIN(a, b)
669 // MAX(MIN(a, b), a) -> a
670 // MIN(MAX(a, b), a) -> a
671 Value *LHS, *RHS, *LHS2, *RHS2;
672 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
673 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
674 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
677 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
678 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
685 // ABS(ABS(X)) -> ABS(X)
688 // See if we can fold the select into a phi node if the condition is a select.
689 if (isa<PHINode>(SI.getCondition()))
690 // The true/false values have to be live in the PHI predecessor's blocks.
691 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
692 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
693 if (Instruction *NV = FoldOpIntoPhi(SI))
696 if (BinaryOperator::isNot(CondVal)) {
697 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
698 SI.setOperand(1, FalseVal);
699 SI.setOperand(2, TrueVal);
703 // select (or (A == 0) (B == 0)) T, F--> select (and (A != 0) (B != 0)) F, T
704 // Note: This is a canonicalization rather than an optimization, and is used
705 // to expose opportunities to other instcombine transforms.
706 Instruction* CondInst = dyn_cast<Instruction>(CondVal);
707 if (CondInst && CondInst->getOpcode() == Instruction::Or) {
708 ICmpInst *LHSCmp = dyn_cast<ICmpInst>(CondInst->getOperand(0));
709 ICmpInst *RHSCmp = dyn_cast<ICmpInst>(CondInst->getOperand(1));
710 if (LHSCmp && LHSCmp->getPredicate() == ICmpInst::ICMP_EQ &&
711 RHSCmp && RHSCmp->getPredicate() == ICmpInst::ICMP_EQ) {
712 ConstantInt* C1 = dyn_cast<ConstantInt>(LHSCmp->getOperand(1));
713 ConstantInt* C2 = dyn_cast<ConstantInt>(RHSCmp->getOperand(1));
714 if (C1 && C1->isZero() && C2 && C2->isZero()) {
715 LHSCmp->setPredicate(ICmpInst::ICMP_NE);
716 RHSCmp->setPredicate(ICmpInst::ICMP_NE);
718 InsertNewInstBefore(BinaryOperator::CreateAnd(LHSCmp, RHSCmp,
719 "and."+CondVal->getName()), SI);
720 SI.setOperand(0, And);
721 SI.setOperand(1, FalseVal);
722 SI.setOperand(2, TrueVal);