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 if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
200 return C1I->isOne() || C1I->isAllOnesValue() ||
201 C2I->isOne() || C2I->isAllOnesValue();
204 /// FoldSelectIntoOp - Try fold the select into one of the operands to
205 /// facilitate further optimization.
206 Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
208 // See the comment above GetSelectFoldableOperands for a description of the
209 // transformation we are doing here.
210 if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
211 if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
212 !isa<Constant>(FalseVal)) {
213 if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
214 unsigned OpToFold = 0;
215 if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
217 } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
222 Constant *C = GetSelectFoldableConstant(TVI);
223 Value *OOp = TVI->getOperand(2-OpToFold);
224 // Avoid creating select between 2 constants unless it's selecting
225 // between 0, 1 and -1.
226 if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
227 Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
228 InsertNewInstBefore(NewSel, SI);
229 NewSel->takeName(TVI);
230 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
231 return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
232 llvm_unreachable("Unknown instruction!!");
239 if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
240 if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
241 !isa<Constant>(TrueVal)) {
242 if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
243 unsigned OpToFold = 0;
244 if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
246 } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
251 Constant *C = GetSelectFoldableConstant(FVI);
252 Value *OOp = FVI->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 Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
257 InsertNewInstBefore(NewSel, SI);
258 NewSel->takeName(FVI);
259 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
260 return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
261 llvm_unreachable("Unknown instruction!!");
271 /// visitSelectInstWithICmp - Visit a SelectInst that has an
272 /// ICmpInst as its first operand.
274 Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
276 bool Changed = false;
277 ICmpInst::Predicate Pred = ICI->getPredicate();
278 Value *CmpLHS = ICI->getOperand(0);
279 Value *CmpRHS = ICI->getOperand(1);
280 Value *TrueVal = SI.getTrueValue();
281 Value *FalseVal = SI.getFalseValue();
283 // Check cases where the comparison is with a constant that
284 // can be adjusted to fit the min/max idiom. We may edit ICI in
285 // place here, so make sure the select is the only user.
286 if (ICI->hasOneUse())
287 if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
290 case ICmpInst::ICMP_ULT:
291 case ICmpInst::ICMP_SLT: {
292 // X < MIN ? T : F --> F
293 if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
294 return ReplaceInstUsesWith(SI, FalseVal);
295 // X < C ? X : C-1 --> X > C-1 ? C-1 : X
296 Constant *AdjustedRHS =
297 ConstantInt::get(CI->getContext(), CI->getValue()-1);
298 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
299 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
300 Pred = ICmpInst::getSwappedPredicate(Pred);
301 CmpRHS = AdjustedRHS;
302 std::swap(FalseVal, TrueVal);
303 ICI->setPredicate(Pred);
304 ICI->setOperand(1, CmpRHS);
305 SI.setOperand(1, TrueVal);
306 SI.setOperand(2, FalseVal);
311 case ICmpInst::ICMP_UGT:
312 case ICmpInst::ICMP_SGT: {
313 // X > MAX ? T : F --> F
314 if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
315 return ReplaceInstUsesWith(SI, FalseVal);
316 // X > C ? X : C+1 --> X < C+1 ? C+1 : X
317 Constant *AdjustedRHS =
318 ConstantInt::get(CI->getContext(), CI->getValue()+1);
319 if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
320 (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
321 Pred = ICmpInst::getSwappedPredicate(Pred);
322 CmpRHS = AdjustedRHS;
323 std::swap(FalseVal, TrueVal);
324 ICI->setPredicate(Pred);
325 ICI->setOperand(1, CmpRHS);
326 SI.setOperand(1, TrueVal);
327 SI.setOperand(2, FalseVal);
335 // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
336 // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
337 // FIXME: Type and constness constraints could be lifted, but we have to
338 // watch code size carefully. We should consider xor instead of
339 // sub/add when we decide to do that.
340 if (const IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
341 if (TrueVal->getType() == Ty) {
342 if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
343 ConstantInt *C1 = NULL, *C2 = NULL;
344 if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
345 C1 = dyn_cast<ConstantInt>(TrueVal);
346 C2 = dyn_cast<ConstantInt>(FalseVal);
347 } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
348 C1 = dyn_cast<ConstantInt>(FalseVal);
349 C2 = dyn_cast<ConstantInt>(TrueVal);
352 // This shift results in either -1 or 0.
353 Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
355 // Check if we can express the operation with a single or.
356 if (C2->isAllOnesValue())
357 return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
359 Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
360 return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
366 if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
367 // Transform (X == Y) ? X : Y -> Y
368 if (Pred == ICmpInst::ICMP_EQ)
369 return ReplaceInstUsesWith(SI, FalseVal);
370 // Transform (X != Y) ? X : Y -> X
371 if (Pred == ICmpInst::ICMP_NE)
372 return ReplaceInstUsesWith(SI, TrueVal);
373 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
375 } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
376 // Transform (X == Y) ? Y : X -> X
377 if (Pred == ICmpInst::ICMP_EQ)
378 return ReplaceInstUsesWith(SI, FalseVal);
379 // Transform (X != Y) ? Y : X -> Y
380 if (Pred == ICmpInst::ICMP_NE)
381 return ReplaceInstUsesWith(SI, TrueVal);
382 /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
384 return Changed ? &SI : 0;
388 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
389 /// PHI node (but the two may be in different blocks). See if the true/false
390 /// values (V) are live in all of the predecessor blocks of the PHI. For
391 /// example, cases like this cannot be mapped:
393 /// X = phi [ C1, BB1], [C2, BB2]
395 /// Z = select X, Y, 0
397 /// because Y is not live in BB1/BB2.
399 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
400 const SelectInst &SI) {
401 // If the value is a non-instruction value like a constant or argument, it
402 // can always be mapped.
403 const Instruction *I = dyn_cast<Instruction>(V);
404 if (I == 0) return true;
406 // If V is a PHI node defined in the same block as the condition PHI, we can
407 // map the arguments.
408 const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
410 if (const PHINode *VP = dyn_cast<PHINode>(I))
411 if (VP->getParent() == CondPHI->getParent())
414 // Otherwise, if the PHI and select are defined in the same block and if V is
415 // defined in a different block, then we can transform it.
416 if (SI.getParent() == CondPHI->getParent() &&
417 I->getParent() != CondPHI->getParent())
420 // Otherwise we have a 'hard' case and we can't tell without doing more
421 // detailed dominator based analysis, punt.
425 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
426 /// SPF2(SPF1(A, B), C)
427 Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
428 SelectPatternFlavor SPF1,
431 SelectPatternFlavor SPF2, Value *C) {
432 if (C == A || C == B) {
433 // MAX(MAX(A, B), B) -> MAX(A, B)
434 // MIN(MIN(a, b), a) -> MIN(a, b)
436 return ReplaceInstUsesWith(Outer, Inner);
438 // MAX(MIN(a, b), a) -> a
439 // MIN(MAX(a, b), a) -> a
440 if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
441 (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
442 (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
443 (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
444 return ReplaceInstUsesWith(Outer, C);
447 // TODO: MIN(MIN(A, 23), 97)
452 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
453 /// both be) and we have an icmp instruction with zero, and we have an 'and'
454 /// with the non-constant value and a power of two we can turn the select
455 /// into a shift on the result of the 'and'.
456 static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
457 ConstantInt *FalseVal,
458 InstCombiner::BuilderTy *Builder) {
459 const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
460 if (!IC || !IC->isEquality())
463 if (ConstantInt *C = dyn_cast<ConstantInt>(IC->getOperand(1)))
468 Value *LHS = IC->getOperand(0);
469 if (LHS->getType() != SI.getType() ||
470 !match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
473 // If both select arms are non-zero see if we have a select of the form
474 // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
475 // for 'x ? 2^n : 0' and fix the thing up at the end.
476 ConstantInt *Offset = 0;
477 if (!TrueVal->isZero() && !FalseVal->isZero()) {
478 if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
480 else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
485 // Adjust TrueVal and FalseVal to the offset.
486 TrueVal = ConstantInt::get(Builder->getContext(),
487 TrueVal->getValue() - Offset->getValue());
488 FalseVal = ConstantInt::get(Builder->getContext(),
489 FalseVal->getValue() - Offset->getValue());
492 // Make sure the mask in the 'and' and one of the select arms is a power of 2.
493 if (!AndRHS->getValue().isPowerOf2() ||
494 (!TrueVal->getValue().isPowerOf2() &&
495 !FalseVal->getValue().isPowerOf2()))
498 // Determine which shift is needed to transform result of the 'and' into the
500 ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
501 unsigned ValZeros = ValC->getValue().logBase2();
502 unsigned AndZeros = AndRHS->getValue().logBase2();
505 if (ValZeros > AndZeros)
506 V = Builder->CreateShl(V, ValZeros - AndZeros);
507 else if (ValZeros < AndZeros)
508 V = Builder->CreateLShr(V, AndZeros - ValZeros);
510 // Okay, now we know that everything is set up, we just don't know whether we
511 // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
512 bool ShouldNotVal = !TrueVal->isZero();
513 ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
515 V = Builder->CreateXor(V, ValC);
517 // Apply an offset if needed.
519 V = Builder->CreateAdd(V, Offset);
523 Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
524 Value *CondVal = SI.getCondition();
525 Value *TrueVal = SI.getTrueValue();
526 Value *FalseVal = SI.getFalseValue();
528 if (Value *V = SimplifySelectInst(CondVal, TrueVal, FalseVal, TD))
529 return ReplaceInstUsesWith(SI, V);
531 if (SI.getType()->isIntegerTy(1)) {
532 if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
533 if (C->getZExtValue()) {
534 // Change: A = select B, true, C --> A = or B, C
535 return BinaryOperator::CreateOr(CondVal, FalseVal);
537 // Change: A = select B, false, C --> A = and !B, C
539 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
540 "not."+CondVal->getName()), SI);
541 return BinaryOperator::CreateAnd(NotCond, FalseVal);
542 } else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
543 if (C->getZExtValue() == false) {
544 // Change: A = select B, C, false --> A = and B, C
545 return BinaryOperator::CreateAnd(CondVal, TrueVal);
547 // Change: A = select B, C, true --> A = or !B, C
549 InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
550 "not."+CondVal->getName()), SI);
551 return BinaryOperator::CreateOr(NotCond, TrueVal);
554 // select a, b, a -> a&b
555 // select a, a, b -> a|b
556 if (CondVal == TrueVal)
557 return BinaryOperator::CreateOr(CondVal, FalseVal);
558 else if (CondVal == FalseVal)
559 return BinaryOperator::CreateAnd(CondVal, TrueVal);
562 // Selecting between two integer constants?
563 if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
564 if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
565 // select C, 1, 0 -> zext C to int
566 if (FalseValC->isZero() && TrueValC->getValue() == 1)
567 return new ZExtInst(CondVal, SI.getType());
569 // select C, -1, 0 -> sext C to int
570 if (FalseValC->isZero() && TrueValC->isAllOnesValue())
571 return new SExtInst(CondVal, SI.getType());
573 // select C, 0, 1 -> zext !C to int
574 if (TrueValC->isZero() && FalseValC->getValue() == 1) {
575 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
576 return new ZExtInst(NotCond, SI.getType());
579 // select C, 0, -1 -> sext !C to int
580 if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
581 Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
582 return new SExtInst(NotCond, SI.getType());
585 if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
586 return ReplaceInstUsesWith(SI, V);
589 // See if we are selecting two values based on a comparison of the two values.
590 if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
591 if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
592 // Transform (X == Y) ? X : Y -> Y
593 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
594 // This is not safe in general for floating point:
595 // consider X== -0, Y== +0.
596 // It becomes safe if either operand is a nonzero constant.
597 ConstantFP *CFPt, *CFPf;
598 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
599 !CFPt->getValueAPF().isZero()) ||
600 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
601 !CFPf->getValueAPF().isZero()))
602 return ReplaceInstUsesWith(SI, FalseVal);
604 // Transform (X une Y) ? X : Y -> X
605 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
606 // This is not safe in general for floating point:
607 // consider X== -0, Y== +0.
608 // It becomes safe if either operand is a nonzero constant.
609 ConstantFP *CFPt, *CFPf;
610 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
611 !CFPt->getValueAPF().isZero()) ||
612 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
613 !CFPf->getValueAPF().isZero()))
614 return ReplaceInstUsesWith(SI, TrueVal);
616 // NOTE: if we wanted to, this is where to detect MIN/MAX
618 } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
619 // Transform (X == Y) ? Y : X -> X
620 if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
621 // This is not safe in general for floating point:
622 // consider X== -0, Y== +0.
623 // It becomes safe if either operand is a nonzero constant.
624 ConstantFP *CFPt, *CFPf;
625 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
626 !CFPt->getValueAPF().isZero()) ||
627 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
628 !CFPf->getValueAPF().isZero()))
629 return ReplaceInstUsesWith(SI, FalseVal);
631 // Transform (X une Y) ? Y : X -> Y
632 if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
633 // This is not safe in general for floating point:
634 // consider X== -0, Y== +0.
635 // It becomes safe if either operand is a nonzero constant.
636 ConstantFP *CFPt, *CFPf;
637 if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
638 !CFPt->getValueAPF().isZero()) ||
639 ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
640 !CFPf->getValueAPF().isZero()))
641 return ReplaceInstUsesWith(SI, TrueVal);
643 // NOTE: if we wanted to, this is where to detect MIN/MAX
645 // NOTE: if we wanted to, this is where to detect ABS
648 // See if we are selecting two values based on a comparison of the two values.
649 if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
650 if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
653 if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
654 if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
655 if (TI->hasOneUse() && FI->hasOneUse()) {
656 Instruction *AddOp = 0, *SubOp = 0;
658 // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
659 if (TI->getOpcode() == FI->getOpcode())
660 if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
663 // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
664 // even legal for FP.
665 if ((TI->getOpcode() == Instruction::Sub &&
666 FI->getOpcode() == Instruction::Add) ||
667 (TI->getOpcode() == Instruction::FSub &&
668 FI->getOpcode() == Instruction::FAdd)) {
669 AddOp = FI; SubOp = TI;
670 } else if ((FI->getOpcode() == Instruction::Sub &&
671 TI->getOpcode() == Instruction::Add) ||
672 (FI->getOpcode() == Instruction::FSub &&
673 TI->getOpcode() == Instruction::FAdd)) {
674 AddOp = TI; SubOp = FI;
678 Value *OtherAddOp = 0;
679 if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
680 OtherAddOp = AddOp->getOperand(1);
681 } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
682 OtherAddOp = AddOp->getOperand(0);
686 // So at this point we know we have (Y -> OtherAddOp):
687 // select C, (add X, Y), (sub X, Z)
688 Value *NegVal; // Compute -Z
689 if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
690 NegVal = ConstantExpr::getNeg(C);
691 } else if (SI.getType()->isFloatingPointTy()) {
692 NegVal = InsertNewInstBefore(
693 BinaryOperator::CreateFNeg(SubOp->getOperand(1),
696 NegVal = InsertNewInstBefore(
697 BinaryOperator::CreateNeg(SubOp->getOperand(1),
701 Value *NewTrueOp = OtherAddOp;
702 Value *NewFalseOp = NegVal;
704 std::swap(NewTrueOp, NewFalseOp);
705 Instruction *NewSel =
706 SelectInst::Create(CondVal, NewTrueOp,
707 NewFalseOp, SI.getName() + ".p");
709 NewSel = InsertNewInstBefore(NewSel, SI);
710 if (SI.getType()->isFloatingPointTy())
711 return BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
713 return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
718 // See if we can fold the select into one of our operands.
719 if (SI.getType()->isIntegerTy()) {
720 if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
723 // MAX(MAX(a, b), a) -> MAX(a, b)
724 // MIN(MIN(a, b), a) -> MIN(a, b)
725 // MAX(MIN(a, b), a) -> a
726 // MIN(MAX(a, b), a) -> a
727 Value *LHS, *RHS, *LHS2, *RHS2;
728 if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
729 if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
730 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
733 if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
734 if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
741 // ABS(ABS(X)) -> ABS(X)
744 // See if we can fold the select into a phi node if the condition is a select.
745 if (isa<PHINode>(SI.getCondition()))
746 // The true/false values have to be live in the PHI predecessor's blocks.
747 if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
748 CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
749 if (Instruction *NV = FoldOpIntoPhi(SI))
752 if (BinaryOperator::isNot(CondVal)) {
753 SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
754 SI.setOperand(1, FalseVal);
755 SI.setOperand(2, TrueVal);