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"
17 using namespace PatternMatch;
19 /// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
20 /// returning the kind and providing the out parameter results if we
21 /// successfully match.
22 static SelectPatternFlavor
23 MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
24 SelectInst *SI = dyn_cast<SelectInst>(V);
25 if (SI == 0) return SPF_UNKNOWN;
27 ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
28 if (ICI == 0) return SPF_UNKNOWN;
30 LHS = ICI->getOperand(0);
31 RHS = ICI->getOperand(1);
33 // (icmp X, Y) ? X : Y
34 if (SI->getTrueValue() == ICI->getOperand(0) &&
35 SI->getFalseValue() == ICI->getOperand(1)) {
36 switch (ICI->getPredicate()) {
37 default: return SPF_UNKNOWN; // Equality.
38 case ICmpInst::ICMP_UGT:
39 case ICmpInst::ICMP_UGE: return SPF_UMAX;
40 case ICmpInst::ICMP_SGT:
41 case ICmpInst::ICMP_SGE: return SPF_SMAX;
42 case ICmpInst::ICMP_ULT:
43 case ICmpInst::ICMP_ULE: return SPF_UMIN;
44 case ICmpInst::ICMP_SLT:
45 case ICmpInst::ICMP_SLE: return SPF_SMIN;
49 // (icmp X, Y) ? Y : X
50 if (SI->getTrueValue() == ICI->getOperand(1) &&
51 SI->getFalseValue() == ICI->getOperand(0)) {
52 switch (ICI->getPredicate()) {
53 default: return SPF_UNKNOWN; // Equality.
54 case ICmpInst::ICMP_UGT:
55 case ICmpInst::ICMP_UGE: return SPF_UMIN;
56 case ICmpInst::ICMP_SGT:
57 case ICmpInst::ICMP_SGE: return SPF_SMIN;
58 case ICmpInst::ICMP_ULT:
59 case ICmpInst::ICMP_ULE: return SPF_UMAX;
60 case ICmpInst::ICMP_SLT:
61 case ICmpInst::ICMP_SLE: return SPF_SMAX;
65 // TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
71 /// GetSelectFoldableOperands - We want to turn code that looks like this:
73 /// %D = select %cond, %C, %A
75 /// %C = select %cond, %B, 0
78 /// Assuming that the specified instruction is an operand to the select, return
79 /// a bitmask indicating which operands of this instruction are foldable if they
80 /// equal the other incoming value of the select.
82 static unsigned GetSelectFoldableOperands(Instruction *I) {
83 switch (I->getOpcode()) {
84 case Instruction::Add:
85 case Instruction::Mul:
86 case Instruction::And:
88 case Instruction::Xor:
89 return 3; // Can fold through either operand.
90 case Instruction::Sub: // Can only fold on the amount subtracted.
91 case Instruction::Shl: // Can only fold on the shift amount.
92 case Instruction::LShr:
93 case Instruction::AShr:
96 return 0; // Cannot fold
100 /// GetSelectFoldableConstant - For the same transformation as the previous
101 /// function, return the identity constant that goes into the select.
102 static Constant *GetSelectFoldableConstant(Instruction *I) {
103 switch (I->getOpcode()) {
104 default: llvm_unreachable("This cannot happen!");
105 case Instruction::Add:
106 case Instruction::Sub:
107 case Instruction::Or:
108 case Instruction::Xor:
109 case Instruction::Shl:
110 case Instruction::LShr:
111 case Instruction::AShr:
112 return Constant::getNullValue(I->getType());
113 case Instruction::And:
114 return Constant::getAllOnesValue(I->getType());
115 case Instruction::Mul:
116 return ConstantInt::get(I->getType(), 1);
120 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
121 /// have the same opcode and only one use each. Try to simplify this.
122 Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
124 if (TI->getNumOperands() == 1) {
125 // If this is a non-volatile load or a cast from the same type,
128 if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
131 return 0; // unknown unary op.
134 // Fold this by inserting a select from the input values.
135 SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0),
136 FI->getOperand(0), SI.getName()+".v");
137 InsertNewInstBefore(NewSI, SI);
138 return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
142 // Only handle binary operators here.
143 if (!isa<BinaryOperator>(TI))
146 // Figure out if the operations have any operands in common.
147 Value *MatchOp, *OtherOpT, *OtherOpF;
149 if (TI->getOperand(0) == FI->getOperand(0)) {
150 MatchOp = TI->getOperand(0);
151 OtherOpT = TI->getOperand(1);
152 OtherOpF = FI->getOperand(1);
153 MatchIsOpZero = true;
154 } else if (TI->getOperand(1) == FI->getOperand(1)) {
155 MatchOp = TI->getOperand(1);
156 OtherOpT = TI->getOperand(0);
157 OtherOpF = FI->getOperand(0);
158 MatchIsOpZero = false;
159 } else if (!TI->isCommutative()) {
161 } else if (TI->getOperand(0) == FI->getOperand(1)) {
162 MatchOp = TI->getOperand(0);
163 OtherOpT = TI->getOperand(1);
164 OtherOpF = FI->getOperand(0);
165 MatchIsOpZero = true;
166 } else if (TI->getOperand(1) == FI->getOperand(0)) {
167 MatchOp = TI->getOperand(1);
168 OtherOpT = TI->getOperand(0);
169 OtherOpF = FI->getOperand(1);
170 MatchIsOpZero = true;
175 // If we reach here, they do have operations in common.
176 SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT,
177 OtherOpF, SI.getName()+".v");
178 InsertNewInstBefore(NewSI, SI);
180 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
182 return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
184 return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
186 llvm_unreachable("Shouldn't get here");
190 static bool isSelect01(Constant *C1, Constant *C2) {
191 ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
194 ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
197 return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne());
200 /// FoldSelectIntoOp - Try fold the select into one of the operands to
201 /// facilitate further optimization.
202 Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
204 // See the comment above GetSelectFoldableOperands for a description of the
205 // transformation we are doing here.
206 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
207 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
208 !isa<Constant>(FalseVal)) {
209 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
210 unsigned OpToFold = 0;
211 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
213 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
218 Constant *C = GetSelectFoldableConstant(TVI);
219 Value *OOp = TVI->getOperand(2-OpToFold);
220 // Avoid creating select between 2 constants unless it's selecting
222 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
223 Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
224 InsertNewInstBefore(NewSel, SI);
225 NewSel->takeName(TVI);
226 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
227 return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
228 llvm_unreachable("Unknown instruction!!");
235 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
236 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
237 !isa<Constant>(TrueVal)) {
238 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
239 unsigned OpToFold = 0;
240 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
242 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
247 Constant *C = GetSelectFoldableConstant(FVI);
248 Value *OOp = FVI->getOperand(2-OpToFold);
249 // Avoid creating select between 2 constants unless it's selecting
251 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
252 Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
253 InsertNewInstBefore(NewSel, SI);
254 NewSel->takeName(FVI);
255 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
256 return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
257 llvm_unreachable("Unknown instruction!!");
267 /// visitSelectInstWithICmp - Visit a SelectInst that has an
268 /// ICmpInst as its first operand.
270 Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
272 bool Changed = false;
273 ICmpInst::Predicate Pred = ICI->getPredicate();
274 Value *CmpLHS = ICI->getOperand(0);
275 Value *CmpRHS = ICI->getOperand(1);
276 Value *TrueVal = SI.getTrueValue();
277 Value *FalseVal = SI.getFalseValue();
279 // Check cases where the comparison is with a constant that
280 // can be adjusted to fit the min/max idiom. We may edit ICI in
281 // place here, so make sure the select is the only user.
282 if (ICI->hasOneUse())
283 if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
286 case ICmpInst::ICMP_ULT:
287 case ICmpInst::ICMP_SLT: {
288 // X < MIN ? T : F --> F
289 if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
290 return ReplaceInstUsesWith(SI, FalseVal);
291 // X < C ? X : C-1 --> X > C-1 ? C-1 : X
292 Constant *AdjustedRHS =
293 ConstantInt::get(CI->getContext(), CI->getValue()-1);
294 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
295 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
296 Pred = ICmpInst::getSwappedPredicate(Pred);
297 CmpRHS = AdjustedRHS;
298 std::swap(FalseVal, TrueVal);
299 ICI->setPredicate(Pred);
300 ICI->setOperand(1, CmpRHS);
301 SI.setOperand(1, TrueVal);
302 SI.setOperand(2, FalseVal);
307 case ICmpInst::ICMP_UGT:
308 case ICmpInst::ICMP_SGT: {
309 // X > MAX ? T : F --> F
310 if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
311 return ReplaceInstUsesWith(SI, FalseVal);
312 // X > C ? X : C+1 --> X < C+1 ? C+1 : X
313 Constant *AdjustedRHS =
314 ConstantInt::get(CI->getContext(), CI->getValue()+1);
315 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
316 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
317 Pred = ICmpInst::getSwappedPredicate(Pred);
318 CmpRHS = AdjustedRHS;
319 std::swap(FalseVal, TrueVal);
320 ICI->setPredicate(Pred);
321 ICI->setOperand(1, CmpRHS);
322 SI.setOperand(1, TrueVal);
323 SI.setOperand(2, FalseVal);
331 if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
332 // Transform (X == Y) ? X : Y -> Y
333 if (Pred == ICmpInst::ICMP_EQ)
334 return ReplaceInstUsesWith(SI, FalseVal);
335 // Transform (X != Y) ? X : Y -> X
336 if (Pred == ICmpInst::ICMP_NE)
337 return ReplaceInstUsesWith(SI, TrueVal);
338 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
340 } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
341 // Transform (X == Y) ? Y : X -> X
342 if (Pred == ICmpInst::ICMP_EQ)
343 return ReplaceInstUsesWith(SI, FalseVal);
344 // Transform (X != Y) ? Y : X -> Y
345 if (Pred == ICmpInst::ICMP_NE)
346 return ReplaceInstUsesWith(SI, TrueVal);
347 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
349 return Changed ? &SI : 0;
353 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
354 /// PHI node (but the two may be in different blocks). See if the true/false
355 /// values (V) are live in all of the predecessor blocks of the PHI. For
356 /// example, cases like this cannot be mapped:
358 /// X = phi [ C1, BB1], [C2, BB2]
360 /// Z = select X, Y, 0
362 /// because Y is not live in BB1/BB2.
364 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
365 const SelectInst &SI) {
366 // If the value is a non-instruction value like a constant or argument, it
367 // can always be mapped.
368 const Instruction *I = dyn_cast<Instruction>(V);
369 if (I == 0) return true;
371 // If V is a PHI node defined in the same block as the condition PHI, we can
372 // map the arguments.
373 const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
375 if (const PHINode *VP = dyn_cast<PHINode>(I))
376 if (VP->getParent() == CondPHI->getParent())
379 // Otherwise, if the PHI and select are defined in the same block and if V is
380 // defined in a different block, then we can transform it.
381 if (SI.getParent() == CondPHI->getParent() &&
382 I->getParent() != CondPHI->getParent())
385 // Otherwise we have a 'hard' case and we can't tell without doing more
386 // detailed dominator based analysis, punt.
390 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
391 /// SPF2(SPF1(A, B), C)
392 Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
393 SelectPatternFlavor SPF1,
396 SelectPatternFlavor SPF2, Value *C) {
397 if (C == A || C == B) {
398 // MAX(MAX(A, B), B) -> MAX(A, B)
399 // MIN(MIN(a, b), a) -> MIN(a, b)
401 return ReplaceInstUsesWith(Outer, Inner);
403 // MAX(MIN(a, b), a) -> a
404 // MIN(MAX(a, b), a) -> a
405 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
406 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
407 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
408 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
409 return ReplaceInstUsesWith(Outer, C);
412 // TODO: MIN(MIN(A, 23), 97)
419 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
420 Value *CondVal = SI.getCondition();
421 Value *TrueVal = SI.getTrueValue();
422 Value *FalseVal = SI.getFalseValue();
424 // select true, X, Y -> X
425 // select false, X, Y -> Y
426 if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
427 return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
429 // select C, X, X -> X
430 if (TrueVal == FalseVal)
431 return ReplaceInstUsesWith(SI, TrueVal);
433 if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
434 return ReplaceInstUsesWith(SI, FalseVal);
435 if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
436 return ReplaceInstUsesWith(SI, TrueVal);
437 if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
438 if (isa<Constant>(TrueVal))
439 return ReplaceInstUsesWith(SI, TrueVal);
441 return ReplaceInstUsesWith(SI, FalseVal);
444 if (SI.getType()->isIntegerTy(1)) {
445 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
446 if (C->getZExtValue()) {
447 // Change: A = select B, true, C --> A = or B, C
448 return BinaryOperator::CreateOr(CondVal, FalseVal);
450 // Change: A = select B, false, C --> A = and !B, C
452 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
453 "not."+CondVal->getName()), SI);
454 return BinaryOperator::CreateAnd(NotCond, FalseVal);
456 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
457 if (C->getZExtValue() == false) {
458 // Change: A = select B, C, false --> A = and B, C
459 return BinaryOperator::CreateAnd(CondVal, TrueVal);
461 // Change: A = select B, C, true --> A = or !B, C
463 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
464 "not."+CondVal->getName()), SI);
465 return BinaryOperator::CreateOr(NotCond, TrueVal);
469 // select a, b, a -> a&b
470 // select a, a, b -> a|b
471 if (CondVal == TrueVal)
472 return BinaryOperator::CreateOr(CondVal, FalseVal);
473 else if (CondVal == FalseVal)
474 return BinaryOperator::CreateAnd(CondVal, TrueVal);
477 // Selecting between two integer constants?
478 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
479 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
480 // select C, 1, 0 -> zext C to int
481 if (FalseValC->isZero() && TrueValC->getValue() == 1)
482 return new ZExtInst(CondVal, SI.getType());
484 // select C, -1, 0 -> sext C to int
485 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
486 return new SExtInst(CondVal, SI.getType());
488 // select C, 0, 1 -> zext !C to int
489 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
490 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
491 return new ZExtInst(NotCond, SI.getType());
494 // select C, 0, -1 -> sext !C to int
495 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
496 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
497 return new SExtInst(NotCond, SI.getType());
500 if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
501 // If one of the constants is zero (we know they can't both be) and we
502 // have an icmp instruction with zero, and we have an 'and' with the
503 // non-constant value, eliminate this whole mess. This corresponds to
504 // cases like this: ((X & 27) ? 27 : 0)
505 if (TrueValC->isZero() || FalseValC->isZero())
506 if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
507 cast<Constant>(IC->getOperand(1))->isNullValue())
508 if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
509 if (ICA->getOpcode() == Instruction::And &&
510 isa<ConstantInt>(ICA->getOperand(1)) &&
511 (ICA->getOperand(1) == TrueValC ||
512 ICA->getOperand(1) == FalseValC) &&
513 cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) {
514 // Okay, now we know that everything is set up, we just don't
515 // know whether we have a icmp_ne or icmp_eq and whether the
516 // true or false val is the zero.
517 bool ShouldNotVal = !TrueValC->isZero();
518 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
521 V = Builder->CreateXor(V, ICA->getOperand(1));
522 return ReplaceInstUsesWith(SI, V);
527 // See if we are selecting two values based on a comparison of the two values.
528 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
529 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
530 // Transform (X == Y) ? X : Y -> Y
531 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
532 // This is not safe in general for floating point:
533 // consider X== -0, Y== +0.
534 // It becomes safe if either operand is a nonzero constant.
535 ConstantFP *CFPt, *CFPf;
536 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
537 !CFPt->getValueAPF().isZero()) ||
538 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
539 !CFPf->getValueAPF().isZero()))
540 return ReplaceInstUsesWith(SI, FalseVal);
542 // Transform (X une Y) ? X : Y -> X
543 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
544 // This is not safe in general for floating point:
545 // consider X== -0, Y== +0.
546 // It becomes safe if either operand is a nonzero constant.
547 ConstantFP *CFPt, *CFPf;
548 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
549 !CFPt->getValueAPF().isZero()) ||
550 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
551 !CFPf->getValueAPF().isZero()))
552 return ReplaceInstUsesWith(SI, TrueVal);
554 // NOTE: if we wanted to, this is where to detect MIN/MAX
556 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
557 // Transform (X == Y) ? Y : X -> X
558 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
559 // This is not safe in general for floating point:
560 // consider X== -0, Y== +0.
561 // It becomes safe if either operand is a nonzero constant.
562 ConstantFP *CFPt, *CFPf;
563 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
564 !CFPt->getValueAPF().isZero()) ||
565 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
566 !CFPf->getValueAPF().isZero()))
567 return ReplaceInstUsesWith(SI, FalseVal);
569 // Transform (X une Y) ? Y : X -> Y
570 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
571 // This is not safe in general for floating point:
572 // consider X== -0, Y== +0.
573 // It becomes safe if either operand is a nonzero constant.
574 ConstantFP *CFPt, *CFPf;
575 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
576 !CFPt->getValueAPF().isZero()) ||
577 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
578 !CFPf->getValueAPF().isZero()))
579 return ReplaceInstUsesWith(SI, TrueVal);
581 // NOTE: if we wanted to, this is where to detect MIN/MAX
583 // NOTE: if we wanted to, this is where to detect ABS
586 // See if we are selecting two values based on a comparison of the two values.
587 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
588 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
591 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
592 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
593 if (TI->hasOneUse() && FI->hasOneUse()) {
594 Instruction *AddOp = 0, *SubOp = 0;
596 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
597 if (TI->getOpcode() == FI->getOpcode())
598 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
601 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
602 // even legal for FP.
603 if ((TI->getOpcode() == Instruction::Sub &&
604 FI->getOpcode() == Instruction::Add) ||
605 (TI->getOpcode() == Instruction::FSub &&
606 FI->getOpcode() == Instruction::FAdd)) {
607 AddOp = FI; SubOp = TI;
608 } else if ((FI->getOpcode() == Instruction::Sub &&
609 TI->getOpcode() == Instruction::Add) ||
610 (FI->getOpcode() == Instruction::FSub &&
611 TI->getOpcode() == Instruction::FAdd)) {
612 AddOp = TI; SubOp = FI;
616 Value *OtherAddOp = 0;
617 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
618 OtherAddOp = AddOp->getOperand(1);
619 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
620 OtherAddOp = AddOp->getOperand(0);
624 // So at this point we know we have (Y -> OtherAddOp):
625 // select C, (add X, Y), (sub X, Z)
626 Value *NegVal; // Compute -Z
627 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
628 NegVal = ConstantExpr::getNeg(C);
630 NegVal = InsertNewInstBefore(
631 BinaryOperator::CreateNeg(SubOp->getOperand(1),
635 Value *NewTrueOp = OtherAddOp;
636 Value *NewFalseOp = NegVal;
638 std::swap(NewTrueOp, NewFalseOp);
639 Instruction *NewSel =
640 SelectInst::Create(CondVal, NewTrueOp,
641 NewFalseOp, SI.getName() + ".p");
643 NewSel = InsertNewInstBefore(NewSel, SI);
644 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
649 // See if we can fold the select into one of our operands.
650 if (SI.getType()->isIntegerTy()) {
651 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
654 // MAX(MAX(a, b), a) -> MAX(a, b)
655 // MIN(MIN(a, b), a) -> MIN(a, b)
656 // MAX(MIN(a, b), a) -> a
657 // MIN(MAX(a, b), a) -> a
658 Value *LHS, *RHS, *LHS2, *RHS2;
659 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
660 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
661 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
664 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
665 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
672 // ABS(ABS(X)) -> ABS(X)
675 // See if we can fold the select into a phi node if the condition is a select.
676 if (isa<PHINode>(SI.getCondition()))
677 // The true/false values have to be live in the PHI predecessor's blocks.
678 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
679 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
680 if (Instruction *NV = FoldOpIntoPhi(SI))
683 if (BinaryOperator::isNot(CondVal)) {
684 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
685 SI.setOperand(1, FalseVal);
686 SI.setOperand(2, TrueVal);