LLVM  3.7.0
InstCombineSelect.cpp
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1 //===- InstCombineSelect.cpp ----------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the visitSelect function.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "InstCombineInternal.h"
18 #include "llvm/IR/PatternMatch.h"
19 using namespace llvm;
20 using namespace PatternMatch;
21 
22 #define DEBUG_TYPE "instcombine"
23 
26  switch (SPF) {
27  default:
28  llvm_unreachable("unhandled!");
29 
30  case SPF_SMIN:
31  return SPF_SMAX;
32  case SPF_UMIN:
33  return SPF_UMAX;
34  case SPF_SMAX:
35  return SPF_SMIN;
36  case SPF_UMAX:
37  return SPF_UMIN;
38  }
39 }
40 
42  switch (SPF) {
43  default:
44  llvm_unreachable("unhandled!");
45 
46  case SPF_SMIN:
47  return ICmpInst::ICMP_SLT;
48  case SPF_UMIN:
49  return ICmpInst::ICMP_ULT;
50  case SPF_SMAX:
51  return ICmpInst::ICMP_SGT;
52  case SPF_UMAX:
53  return ICmpInst::ICMP_UGT;
54  }
55 }
56 
59  Value *B) {
61  return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B);
62 }
63 
64 /// GetSelectFoldableOperands - We want to turn code that looks like this:
65 /// %C = or %A, %B
66 /// %D = select %cond, %C, %A
67 /// into:
68 /// %C = select %cond, %B, 0
69 /// %D = or %A, %C
70 ///
71 /// Assuming that the specified instruction is an operand to the select, return
72 /// a bitmask indicating which operands of this instruction are foldable if they
73 /// equal the other incoming value of the select.
74 ///
76  switch (I->getOpcode()) {
77  case Instruction::Add:
78  case Instruction::Mul:
79  case Instruction::And:
80  case Instruction::Or:
81  case Instruction::Xor:
82  return 3; // Can fold through either operand.
83  case Instruction::Sub: // Can only fold on the amount subtracted.
84  case Instruction::Shl: // Can only fold on the shift amount.
85  case Instruction::LShr:
86  case Instruction::AShr:
87  return 1;
88  default:
89  return 0; // Cannot fold
90  }
91 }
92 
93 /// GetSelectFoldableConstant - For the same transformation as the previous
94 /// function, return the identity constant that goes into the select.
96  switch (I->getOpcode()) {
97  default: llvm_unreachable("This cannot happen!");
98  case Instruction::Add:
99  case Instruction::Sub:
100  case Instruction::Or:
101  case Instruction::Xor:
102  case Instruction::Shl:
103  case Instruction::LShr:
104  case Instruction::AShr:
105  return Constant::getNullValue(I->getType());
106  case Instruction::And:
107  return Constant::getAllOnesValue(I->getType());
108  case Instruction::Mul:
109  return ConstantInt::get(I->getType(), 1);
110  }
111 }
112 
113 /// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
114 /// have the same opcode and only one use each. Try to simplify this.
116  Instruction *FI) {
117  if (TI->getNumOperands() == 1) {
118  // If this is a non-volatile load or a cast from the same type,
119  // merge.
120  if (TI->isCast()) {
121  Type *FIOpndTy = FI->getOperand(0)->getType();
122  if (TI->getOperand(0)->getType() != FIOpndTy)
123  return nullptr;
124  // The select condition may be a vector. We may only change the operand
125  // type if the vector width remains the same (and matches the condition).
126  Type *CondTy = SI.getCondition()->getType();
127  if (CondTy->isVectorTy() && (!FIOpndTy->isVectorTy() ||
128  CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements()))
129  return nullptr;
130  } else {
131  return nullptr; // unknown unary op.
132  }
133 
134  // Fold this by inserting a select from the input values.
135  Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0),
136  FI->getOperand(0), SI.getName()+".v");
137  return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
138  TI->getType());
139  }
140 
141  // Only handle binary operators here.
142  if (!isa<BinaryOperator>(TI))
143  return nullptr;
144 
145  // Figure out if the operations have any operands in common.
146  Value *MatchOp, *OtherOpT, *OtherOpF;
147  bool MatchIsOpZero;
148  if (TI->getOperand(0) == FI->getOperand(0)) {
149  MatchOp = TI->getOperand(0);
150  OtherOpT = TI->getOperand(1);
151  OtherOpF = FI->getOperand(1);
152  MatchIsOpZero = true;
153  } else if (TI->getOperand(1) == FI->getOperand(1)) {
154  MatchOp = TI->getOperand(1);
155  OtherOpT = TI->getOperand(0);
156  OtherOpF = FI->getOperand(0);
157  MatchIsOpZero = false;
158  } else if (!TI->isCommutative()) {
159  return nullptr;
160  } else if (TI->getOperand(0) == FI->getOperand(1)) {
161  MatchOp = TI->getOperand(0);
162  OtherOpT = TI->getOperand(1);
163  OtherOpF = FI->getOperand(0);
164  MatchIsOpZero = true;
165  } else if (TI->getOperand(1) == FI->getOperand(0)) {
166  MatchOp = TI->getOperand(1);
167  OtherOpT = TI->getOperand(0);
168  OtherOpF = FI->getOperand(1);
169  MatchIsOpZero = true;
170  } else {
171  return nullptr;
172  }
173 
174  // If we reach here, they do have operations in common.
175  Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT,
176  OtherOpF, SI.getName()+".v");
177 
178  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
179  if (MatchIsOpZero)
180  return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
181  else
182  return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
183  }
184  llvm_unreachable("Shouldn't get here");
185 }
186 
187 static bool isSelect01(Constant *C1, Constant *C2) {
188  ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
189  if (!C1I)
190  return false;
191  ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
192  if (!C2I)
193  return false;
194  if (!C1I->isZero() && !C2I->isZero()) // One side must be zero.
195  return false;
196  return C1I->isOne() || C1I->isAllOnesValue() ||
197  C2I->isOne() || C2I->isAllOnesValue();
198 }
199 
200 /// FoldSelectIntoOp - Try fold the select into one of the operands to
201 /// facilitate further optimization.
203  Value *FalseVal) {
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)) {
212  OpToFold = 1;
213  } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
214  OpToFold = 2;
215  }
216 
217  if (OpToFold) {
219  Value *OOp = TVI->getOperand(2-OpToFold);
220  // Avoid creating select between 2 constants unless it's selecting
221  // between 0, 1 and -1.
222  if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
223  Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C);
224  NewSel->takeName(TVI);
225  BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI);
227  FalseVal, NewSel);
228  if (isa<PossiblyExactOperator>(BO))
229  BO->setIsExact(TVI_BO->isExact());
230  if (isa<OverflowingBinaryOperator>(BO)) {
231  BO->setHasNoUnsignedWrap(TVI_BO->hasNoUnsignedWrap());
232  BO->setHasNoSignedWrap(TVI_BO->hasNoSignedWrap());
233  }
234  return BO;
235  }
236  }
237  }
238  }
239  }
240 
241  if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
242  if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
243  !isa<Constant>(TrueVal)) {
244  if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
245  unsigned OpToFold = 0;
246  if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
247  OpToFold = 1;
248  } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
249  OpToFold = 2;
250  }
251 
252  if (OpToFold) {
254  Value *OOp = FVI->getOperand(2-OpToFold);
255  // Avoid creating select between 2 constants unless it's selecting
256  // between 0, 1 and -1.
257  if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
258  Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp);
259  NewSel->takeName(FVI);
260  BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI);
262  TrueVal, NewSel);
263  if (isa<PossiblyExactOperator>(BO))
264  BO->setIsExact(FVI_BO->isExact());
265  if (isa<OverflowingBinaryOperator>(BO)) {
266  BO->setHasNoUnsignedWrap(FVI_BO->hasNoUnsignedWrap());
267  BO->setHasNoSignedWrap(FVI_BO->hasNoSignedWrap());
268  }
269  return BO;
270  }
271  }
272  }
273  }
274  }
275 
276  return nullptr;
277 }
278 
279 /// foldSelectICmpAndOr - We want to turn:
280 /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2))
281 /// into:
282 /// (or (shl (and X, C1), C3), y)
283 /// iff:
284 /// C1 and C2 are both powers of 2
285 /// where:
286 /// C3 = Log(C2) - Log(C1)
287 ///
288 /// This transform handles cases where:
289 /// 1. The icmp predicate is inverted
290 /// 2. The select operands are reversed
291 /// 3. The magnitude of C2 and C1 are flipped
292 static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal,
293  Value *FalseVal,
294  InstCombiner::BuilderTy *Builder) {
295  const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
296  if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
297  return nullptr;
298 
299  Value *CmpLHS = IC->getOperand(0);
300  Value *CmpRHS = IC->getOperand(1);
301 
302  if (!match(CmpRHS, m_Zero()))
303  return nullptr;
304 
305  Value *X;
306  const APInt *C1;
307  if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1))))
308  return nullptr;
309 
310  const APInt *C2;
311  bool OrOnTrueVal = false;
312  bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
313  if (!OrOnFalseVal)
314  OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)));
315 
316  if (!OrOnFalseVal && !OrOnTrueVal)
317  return nullptr;
318 
319  Value *V = CmpLHS;
320  Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
321 
322  unsigned C1Log = C1->logBase2();
323  unsigned C2Log = C2->logBase2();
324  if (C2Log > C1Log) {
325  V = Builder->CreateZExtOrTrunc(V, Y->getType());
326  V = Builder->CreateShl(V, C2Log - C1Log);
327  } else if (C1Log > C2Log) {
328  V = Builder->CreateLShr(V, C1Log - C2Log);
329  V = Builder->CreateZExtOrTrunc(V, Y->getType());
330  } else
331  V = Builder->CreateZExtOrTrunc(V, Y->getType());
332 
333  ICmpInst::Predicate Pred = IC->getPredicate();
334  if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) ||
335  (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal))
336  V = Builder->CreateXor(V, *C2);
337 
338  return Builder->CreateOr(V, Y);
339 }
340 
341 /// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single
342 /// call to cttz/ctlz with flag 'is_zero_undef' cleared.
343 ///
344 /// For example, we can fold the following code sequence:
345 /// \code
346 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
347 /// %1 = icmp ne i32 %x, 0
348 /// %2 = select i1 %1, i32 %0, i32 32
349 /// \code
350 ///
351 /// into:
352 /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false)
353 static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal,
354  InstCombiner::BuilderTy *Builder) {
355  ICmpInst::Predicate Pred = ICI->getPredicate();
356  Value *CmpLHS = ICI->getOperand(0);
357  Value *CmpRHS = ICI->getOperand(1);
358 
359  // Check if the condition value compares a value for equality against zero.
360  if (!ICI->isEquality() || !match(CmpRHS, m_Zero()))
361  return nullptr;
362 
363  Value *Count = FalseVal;
364  Value *ValueOnZero = TrueVal;
365  if (Pred == ICmpInst::ICMP_NE)
366  std::swap(Count, ValueOnZero);
367 
368  // Skip zero extend/truncate.
369  Value *V = nullptr;
370  if (match(Count, m_ZExt(m_Value(V))) ||
371  match(Count, m_Trunc(m_Value(V))))
372  Count = V;
373 
374  // Check if the value propagated on zero is a constant number equal to the
375  // sizeof in bits of 'Count'.
376  unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits();
377  if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits)))
378  return nullptr;
379 
380  // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the
381  // input to the cttz/ctlz is used as LHS for the compare instruction.
382  if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) ||
383  match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) {
384  IntrinsicInst *II = cast<IntrinsicInst>(Count);
385  IRBuilder<> Builder(II);
386  // Explicitly clear the 'undef_on_zero' flag.
387  IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone());
388  Type *Ty = NewI->getArgOperand(1)->getType();
390  Builder.Insert(NewI);
391  return Builder.CreateZExtOrTrunc(NewI, ValueOnZero->getType());
392  }
393 
394  return nullptr;
395 }
396 
397 /// visitSelectInstWithICmp - Visit a SelectInst that has an
398 /// ICmpInst as its first operand.
399 ///
401  ICmpInst *ICI) {
402  bool Changed = false;
403  ICmpInst::Predicate Pred = ICI->getPredicate();
404  Value *CmpLHS = ICI->getOperand(0);
405  Value *CmpRHS = ICI->getOperand(1);
406  Value *TrueVal = SI.getTrueValue();
407  Value *FalseVal = SI.getFalseValue();
408 
409  // Check cases where the comparison is with a constant that
410  // can be adjusted to fit the min/max idiom. We may move or edit ICI
411  // here, so make sure the select is the only user.
412  if (ICI->hasOneUse())
413  if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
414  switch (Pred) {
415  default: break;
416  case ICmpInst::ICMP_ULT:
417  case ICmpInst::ICMP_SLT:
418  case ICmpInst::ICMP_UGT:
419  case ICmpInst::ICMP_SGT: {
420  // These transformations only work for selects over integers.
421  IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType());
422  if (!SelectTy)
423  break;
424 
425  Constant *AdjustedRHS;
426  if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT)
427  AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1);
428  else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT)
429  AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1);
430 
431  // X > C ? X : C+1 --> X < C+1 ? C+1 : X
432  // X < C ? X : C-1 --> X > C-1 ? C-1 : X
433  if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
434  (CmpLHS == FalseVal && AdjustedRHS == TrueVal))
435  ; // Nothing to do here. Values match without any sign/zero extension.
436 
437  // Types do not match. Instead of calculating this with mixed types
438  // promote all to the larger type. This enables scalar evolution to
439  // analyze this expression.
440  else if (CmpRHS->getType()->getScalarSizeInBits()
441  < SelectTy->getBitWidth()) {
442  Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy);
443 
444  // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X
445  // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X
446  // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X
447  // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X
448  if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) &&
449  sextRHS == FalseVal) {
450  CmpLHS = TrueVal;
451  AdjustedRHS = sextRHS;
452  } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) &&
453  sextRHS == TrueVal) {
454  CmpLHS = FalseVal;
455  AdjustedRHS = sextRHS;
456  } else if (ICI->isUnsigned()) {
457  Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy);
458  // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X
459  // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X
460  // zext + signed compare cannot be changed:
461  // 0xff <s 0x00, but 0x00ff >s 0x0000
462  if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) &&
463  zextRHS == FalseVal) {
464  CmpLHS = TrueVal;
465  AdjustedRHS = zextRHS;
466  } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) &&
467  zextRHS == TrueVal) {
468  CmpLHS = FalseVal;
469  AdjustedRHS = zextRHS;
470  } else
471  break;
472  } else
473  break;
474  } else
475  break;
476 
477  Pred = ICmpInst::getSwappedPredicate(Pred);
478  CmpRHS = AdjustedRHS;
479  std::swap(FalseVal, TrueVal);
480  ICI->setPredicate(Pred);
481  ICI->setOperand(0, CmpLHS);
482  ICI->setOperand(1, CmpRHS);
483  SI.setOperand(1, TrueVal);
484  SI.setOperand(2, FalseVal);
485 
486  // Move ICI instruction right before the select instruction. Otherwise
487  // the sext/zext value may be defined after the ICI instruction uses it.
488  ICI->moveBefore(&SI);
489 
490  Changed = true;
491  break;
492  }
493  }
494  }
495 
496  // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1
497  // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1
498  // FIXME: Type and constness constraints could be lifted, but we have to
499  // watch code size carefully. We should consider xor instead of
500  // sub/add when we decide to do that.
501  if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) {
502  if (TrueVal->getType() == Ty) {
503  if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) {
504  ConstantInt *C1 = nullptr, *C2 = nullptr;
505  if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) {
506  C1 = dyn_cast<ConstantInt>(TrueVal);
507  C2 = dyn_cast<ConstantInt>(FalseVal);
508  } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) {
509  C1 = dyn_cast<ConstantInt>(FalseVal);
510  C2 = dyn_cast<ConstantInt>(TrueVal);
511  }
512  if (C1 && C2) {
513  // This shift results in either -1 or 0.
514  Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1);
515 
516  // Check if we can express the operation with a single or.
517  if (C2->isAllOnesValue())
518  return ReplaceInstUsesWith(SI, Builder->CreateOr(AShr, C1));
519 
520  Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue());
521  return ReplaceInstUsesWith(SI, Builder->CreateAdd(And, C1));
522  }
523  }
524  }
525  }
526 
527  // NOTE: if we wanted to, this is where to detect integer MIN/MAX
528 
529  if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) {
530  if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
531  // Transform (X == C) ? X : Y -> (X == C) ? C : Y
532  SI.setOperand(1, CmpRHS);
533  Changed = true;
534  } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) {
535  // Transform (X != C) ? Y : X -> (X != C) ? Y : C
536  SI.setOperand(2, CmpRHS);
537  Changed = true;
538  }
539  }
540 
541  {
542  unsigned BitWidth = DL.getTypeSizeInBits(TrueVal->getType());
543  APInt MinSignedValue = APInt::getSignBit(BitWidth);
544  Value *X;
545  const APInt *Y, *C;
546  bool TrueWhenUnset;
547  bool IsBitTest = false;
548  if (ICmpInst::isEquality(Pred) &&
549  match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) &&
550  match(CmpRHS, m_Zero())) {
551  IsBitTest = true;
552  TrueWhenUnset = Pred == ICmpInst::ICMP_EQ;
553  } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) {
554  X = CmpLHS;
555  Y = &MinSignedValue;
556  IsBitTest = true;
557  TrueWhenUnset = false;
558  } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) {
559  X = CmpLHS;
560  Y = &MinSignedValue;
561  IsBitTest = true;
562  TrueWhenUnset = true;
563  }
564  if (IsBitTest) {
565  Value *V = nullptr;
566  // (X & Y) == 0 ? X : X ^ Y --> X & ~Y
567  if (TrueWhenUnset && TrueVal == X &&
568  match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
569  V = Builder->CreateAnd(X, ~(*Y));
570  // (X & Y) != 0 ? X ^ Y : X --> X & ~Y
571  else if (!TrueWhenUnset && FalseVal == X &&
572  match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
573  V = Builder->CreateAnd(X, ~(*Y));
574  // (X & Y) == 0 ? X ^ Y : X --> X | Y
575  else if (TrueWhenUnset && FalseVal == X &&
576  match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
577  V = Builder->CreateOr(X, *Y);
578  // (X & Y) != 0 ? X : X ^ Y --> X | Y
579  else if (!TrueWhenUnset && TrueVal == X &&
580  match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C)
581  V = Builder->CreateOr(X, *Y);
582 
583  if (V)
584  return ReplaceInstUsesWith(SI, V);
585  }
586  }
587 
588  if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder))
589  return ReplaceInstUsesWith(SI, V);
590 
591  if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder))
592  return ReplaceInstUsesWith(SI, V);
593 
594  return Changed ? &SI : nullptr;
595 }
596 
597 
598 /// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
599 /// PHI node (but the two may be in different blocks). See if the true/false
600 /// values (V) are live in all of the predecessor blocks of the PHI. For
601 /// example, cases like this cannot be mapped:
602 ///
603 /// X = phi [ C1, BB1], [C2, BB2]
604 /// Y = add
605 /// Z = select X, Y, 0
606 ///
607 /// because Y is not live in BB1/BB2.
608 ///
609 static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
610  const SelectInst &SI) {
611  // If the value is a non-instruction value like a constant or argument, it
612  // can always be mapped.
613  const Instruction *I = dyn_cast<Instruction>(V);
614  if (!I) return true;
615 
616  // If V is a PHI node defined in the same block as the condition PHI, we can
617  // map the arguments.
618  const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
619 
620  if (const PHINode *VP = dyn_cast<PHINode>(I))
621  if (VP->getParent() == CondPHI->getParent())
622  return true;
623 
624  // Otherwise, if the PHI and select are defined in the same block and if V is
625  // defined in a different block, then we can transform it.
626  if (SI.getParent() == CondPHI->getParent() &&
627  I->getParent() != CondPHI->getParent())
628  return true;
629 
630  // Otherwise we have a 'hard' case and we can't tell without doing more
631  // detailed dominator based analysis, punt.
632  return false;
633 }
634 
635 /// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
636 /// SPF2(SPF1(A, B), C)
638  SelectPatternFlavor SPF1,
639  Value *A, Value *B,
640  Instruction &Outer,
641  SelectPatternFlavor SPF2, Value *C) {
642  if (C == A || C == B) {
643  // MAX(MAX(A, B), B) -> MAX(A, B)
644  // MIN(MIN(a, b), a) -> MIN(a, b)
645  if (SPF1 == SPF2)
646  return ReplaceInstUsesWith(Outer, Inner);
647 
648  // MAX(MIN(a, b), a) -> a
649  // MIN(MAX(a, b), a) -> a
650  if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
651  (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
652  (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
653  (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
654  return ReplaceInstUsesWith(Outer, C);
655  }
656 
657  if (SPF1 == SPF2) {
658  if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) {
659  if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) {
660  APInt ACB = CB->getValue();
661  APInt ACC = CC->getValue();
662 
663  // MIN(MIN(A, 23), 97) -> MIN(A, 23)
664  // MAX(MAX(A, 97), 23) -> MAX(A, 97)
665  if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) ||
666  (SPF1 == SPF_SMIN && ACB.sle(ACC)) ||
667  (SPF1 == SPF_UMAX && ACB.uge(ACC)) ||
668  (SPF1 == SPF_SMAX && ACB.sge(ACC)))
669  return ReplaceInstUsesWith(Outer, Inner);
670 
671  // MIN(MIN(A, 97), 23) -> MIN(A, 23)
672  // MAX(MAX(A, 23), 97) -> MAX(A, 97)
673  if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) ||
674  (SPF1 == SPF_SMIN && ACB.sgt(ACC)) ||
675  (SPF1 == SPF_UMAX && ACB.ult(ACC)) ||
676  (SPF1 == SPF_SMAX && ACB.slt(ACC))) {
677  Outer.replaceUsesOfWith(Inner, A);
678  return &Outer;
679  }
680  }
681  }
682  }
683 
684  // ABS(ABS(X)) -> ABS(X)
685  // NABS(NABS(X)) -> NABS(X)
686  if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) {
687  return ReplaceInstUsesWith(Outer, Inner);
688  }
689 
690  // ABS(NABS(X)) -> ABS(X)
691  // NABS(ABS(X)) -> NABS(X)
692  if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) ||
693  (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) {
694  SelectInst *SI = cast<SelectInst>(Inner);
695  Value *NewSI = Builder->CreateSelect(
696  SI->getCondition(), SI->getFalseValue(), SI->getTrueValue());
697  return ReplaceInstUsesWith(Outer, NewSI);
698  }
699 
700  auto IsFreeOrProfitableToInvert =
701  [&](Value *V, Value *&NotV, bool &ElidesXor) {
702  if (match(V, m_Not(m_Value(NotV)))) {
703  // If V has at most 2 uses then we can get rid of the xor operation
704  // entirely.
705  ElidesXor |= !V->hasNUsesOrMore(3);
706  return true;
707  }
708 
709  if (IsFreeToInvert(V, !V->hasNUsesOrMore(3))) {
710  NotV = nullptr;
711  return true;
712  }
713 
714  return false;
715  };
716 
717  Value *NotA, *NotB, *NotC;
718  bool ElidesXor = false;
719 
720  // MIN(MIN(~A, ~B), ~C) == ~MAX(MAX(A, B), C)
721  // MIN(MAX(~A, ~B), ~C) == ~MAX(MIN(A, B), C)
722  // MAX(MIN(~A, ~B), ~C) == ~MIN(MAX(A, B), C)
723  // MAX(MAX(~A, ~B), ~C) == ~MIN(MIN(A, B), C)
724  //
725  // This transform is performance neutral if we can elide at least one xor from
726  // the set of three operands, since we'll be tacking on an xor at the very
727  // end.
728  if (IsFreeOrProfitableToInvert(A, NotA, ElidesXor) &&
729  IsFreeOrProfitableToInvert(B, NotB, ElidesXor) &&
730  IsFreeOrProfitableToInvert(C, NotC, ElidesXor) && ElidesXor) {
731  if (!NotA)
732  NotA = Builder->CreateNot(A);
733  if (!NotB)
734  NotB = Builder->CreateNot(B);
735  if (!NotC)
736  NotC = Builder->CreateNot(C);
737 
739  Builder, getInverseMinMaxSelectPattern(SPF1), NotA, NotB);
740  Value *NewOuter = Builder->CreateNot(generateMinMaxSelectPattern(
741  Builder, getInverseMinMaxSelectPattern(SPF2), NewInner, NotC));
742  return ReplaceInstUsesWith(Outer, NewOuter);
743  }
744 
745  return nullptr;
746 }
747 
748 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
749 /// both be) and we have an icmp instruction with zero, and we have an 'and'
750 /// with the non-constant value and a power of two we can turn the select
751 /// into a shift on the result of the 'and'.
752 static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal,
753  ConstantInt *FalseVal,
754  InstCombiner::BuilderTy *Builder) {
755  const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
756  if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
757  return nullptr;
758 
759  if (!match(IC->getOperand(1), m_Zero()))
760  return nullptr;
761 
762  ConstantInt *AndRHS;
763  Value *LHS = IC->getOperand(0);
764  if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
765  return nullptr;
766 
767  // If both select arms are non-zero see if we have a select of the form
768  // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic
769  // for 'x ? 2^n : 0' and fix the thing up at the end.
770  ConstantInt *Offset = nullptr;
771  if (!TrueVal->isZero() && !FalseVal->isZero()) {
772  if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2())
773  Offset = FalseVal;
774  else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2())
775  Offset = TrueVal;
776  else
777  return nullptr;
778 
779  // Adjust TrueVal and FalseVal to the offset.
780  TrueVal = ConstantInt::get(Builder->getContext(),
781  TrueVal->getValue() - Offset->getValue());
782  FalseVal = ConstantInt::get(Builder->getContext(),
783  FalseVal->getValue() - Offset->getValue());
784  }
785 
786  // Make sure the mask in the 'and' and one of the select arms is a power of 2.
787  if (!AndRHS->getValue().isPowerOf2() ||
788  (!TrueVal->getValue().isPowerOf2() &&
789  !FalseVal->getValue().isPowerOf2()))
790  return nullptr;
791 
792  // Determine which shift is needed to transform result of the 'and' into the
793  // desired result.
794  ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal;
795  unsigned ValZeros = ValC->getValue().logBase2();
796  unsigned AndZeros = AndRHS->getValue().logBase2();
797 
798  // If types don't match we can still convert the select by introducing a zext
799  // or a trunc of the 'and'. The trunc case requires that all of the truncated
800  // bits are zero, we can figure that out by looking at the 'and' mask.
801  if (AndZeros >= ValC->getBitWidth())
802  return nullptr;
803 
804  Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
805  if (ValZeros > AndZeros)
806  V = Builder->CreateShl(V, ValZeros - AndZeros);
807  else if (ValZeros < AndZeros)
808  V = Builder->CreateLShr(V, AndZeros - ValZeros);
809 
810  // Okay, now we know that everything is set up, we just don't know whether we
811  // have a icmp_ne or icmp_eq and whether the true or false val is the zero.
812  bool ShouldNotVal = !TrueVal->isZero();
813  ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
814  if (ShouldNotVal)
815  V = Builder->CreateXor(V, ValC);
816 
817  // Apply an offset if needed.
818  if (Offset)
819  V = Builder->CreateAdd(V, Offset);
820  return V;
821 }
822 
824  Value *CondVal = SI.getCondition();
825  Value *TrueVal = SI.getTrueValue();
826  Value *FalseVal = SI.getFalseValue();
827 
828  if (Value *V =
829  SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC))
830  return ReplaceInstUsesWith(SI, V);
831 
832  if (SI.getType()->isIntegerTy(1)) {
833  if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
834  if (C->getZExtValue()) {
835  // Change: A = select B, true, C --> A = or B, C
836  return BinaryOperator::CreateOr(CondVal, FalseVal);
837  }
838  // Change: A = select B, false, C --> A = and !B, C
839  Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
840  return BinaryOperator::CreateAnd(NotCond, FalseVal);
841  }
842  if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
843  if (!C->getZExtValue()) {
844  // Change: A = select B, C, false --> A = and B, C
845  return BinaryOperator::CreateAnd(CondVal, TrueVal);
846  }
847  // Change: A = select B, C, true --> A = or !B, C
848  Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
849  return BinaryOperator::CreateOr(NotCond, TrueVal);
850  }
851 
852  // select a, b, a -> a&b
853  // select a, a, b -> a|b
854  if (CondVal == TrueVal)
855  return BinaryOperator::CreateOr(CondVal, FalseVal);
856  if (CondVal == FalseVal)
857  return BinaryOperator::CreateAnd(CondVal, TrueVal);
858 
859  // select a, ~a, b -> (~a)&b
860  // select a, b, ~a -> (~a)|b
861  if (match(TrueVal, m_Not(m_Specific(CondVal))))
862  return BinaryOperator::CreateAnd(TrueVal, FalseVal);
863  if (match(FalseVal, m_Not(m_Specific(CondVal))))
864  return BinaryOperator::CreateOr(TrueVal, FalseVal);
865  }
866 
867  // Selecting between two integer constants?
868  if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
869  if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
870  // select C, 1, 0 -> zext C to int
871  if (FalseValC->isZero() && TrueValC->getValue() == 1)
872  return new ZExtInst(CondVal, SI.getType());
873 
874  // select C, -1, 0 -> sext C to int
875  if (FalseValC->isZero() && TrueValC->isAllOnesValue())
876  return new SExtInst(CondVal, SI.getType());
877 
878  // select C, 0, 1 -> zext !C to int
879  if (TrueValC->isZero() && FalseValC->getValue() == 1) {
880  Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
881  return new ZExtInst(NotCond, SI.getType());
882  }
883 
884  // select C, 0, -1 -> sext !C to int
885  if (TrueValC->isZero() && FalseValC->isAllOnesValue()) {
886  Value *NotCond = Builder->CreateNot(CondVal, "not."+CondVal->getName());
887  return new SExtInst(NotCond, SI.getType());
888  }
889 
890  if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder))
891  return ReplaceInstUsesWith(SI, V);
892  }
893 
894  // See if we are selecting two values based on a comparison of the two values.
895  if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
896  if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
897  // Transform (X == Y) ? X : Y -> Y
898  if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
899  // This is not safe in general for floating point:
900  // consider X== -0, Y== +0.
901  // It becomes safe if either operand is a nonzero constant.
902  ConstantFP *CFPt, *CFPf;
903  if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
904  !CFPt->getValueAPF().isZero()) ||
905  ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
906  !CFPf->getValueAPF().isZero()))
907  return ReplaceInstUsesWith(SI, FalseVal);
908  }
909  // Transform (X une Y) ? X : Y -> X
910  if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
911  // This is not safe in general for floating point:
912  // consider X== -0, Y== +0.
913  // It becomes safe if either operand is a nonzero constant.
914  ConstantFP *CFPt, *CFPf;
915  if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
916  !CFPt->getValueAPF().isZero()) ||
917  ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
918  !CFPf->getValueAPF().isZero()))
919  return ReplaceInstUsesWith(SI, TrueVal);
920  }
921 
922  // Canonicalize to use ordered comparisons by swapping the select
923  // operands.
924  //
925  // e.g.
926  // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
927  if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
928  FCmpInst::Predicate InvPred = FCI->getInversePredicate();
929  Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
930  FCI->getName() + ".inv");
931 
932  return SelectInst::Create(NewCond, FalseVal, TrueVal,
933  SI.getName() + ".p");
934  }
935 
936  // NOTE: if we wanted to, this is where to detect MIN/MAX
937  } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
938  // Transform (X == Y) ? Y : X -> X
939  if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
940  // This is not safe in general for floating point:
941  // consider X== -0, Y== +0.
942  // It becomes safe if either operand is a nonzero constant.
943  ConstantFP *CFPt, *CFPf;
944  if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
945  !CFPt->getValueAPF().isZero()) ||
946  ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
947  !CFPf->getValueAPF().isZero()))
948  return ReplaceInstUsesWith(SI, FalseVal);
949  }
950  // Transform (X une Y) ? Y : X -> Y
951  if (FCI->getPredicate() == FCmpInst::FCMP_UNE) {
952  // This is not safe in general for floating point:
953  // consider X== -0, Y== +0.
954  // It becomes safe if either operand is a nonzero constant.
955  ConstantFP *CFPt, *CFPf;
956  if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
957  !CFPt->getValueAPF().isZero()) ||
958  ((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
959  !CFPf->getValueAPF().isZero()))
960  return ReplaceInstUsesWith(SI, TrueVal);
961  }
962 
963  // Canonicalize to use ordered comparisons by swapping the select
964  // operands.
965  //
966  // e.g.
967  // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
968  if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
969  FCmpInst::Predicate InvPred = FCI->getInversePredicate();
970  Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
971  FCI->getName() + ".inv");
972 
973  return SelectInst::Create(NewCond, FalseVal, TrueVal,
974  SI.getName() + ".p");
975  }
976 
977  // NOTE: if we wanted to, this is where to detect MIN/MAX
978  }
979  // NOTE: if we wanted to, this is where to detect ABS
980  }
981 
982  // See if we are selecting two values based on a comparison of the two values.
983  if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
984  if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
985  return Result;
986 
987  if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
988  if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
989  if (TI->hasOneUse() && FI->hasOneUse()) {
990  Instruction *AddOp = nullptr, *SubOp = nullptr;
991 
992  // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
993  if (TI->getOpcode() == FI->getOpcode())
994  if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
995  return IV;
996 
997  // Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
998  // even legal for FP.
999  if ((TI->getOpcode() == Instruction::Sub &&
1000  FI->getOpcode() == Instruction::Add) ||
1001  (TI->getOpcode() == Instruction::FSub &&
1002  FI->getOpcode() == Instruction::FAdd)) {
1003  AddOp = FI; SubOp = TI;
1004  } else if ((FI->getOpcode() == Instruction::Sub &&
1005  TI->getOpcode() == Instruction::Add) ||
1006  (FI->getOpcode() == Instruction::FSub &&
1007  TI->getOpcode() == Instruction::FAdd)) {
1008  AddOp = TI; SubOp = FI;
1009  }
1010 
1011  if (AddOp) {
1012  Value *OtherAddOp = nullptr;
1013  if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
1014  OtherAddOp = AddOp->getOperand(1);
1015  } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
1016  OtherAddOp = AddOp->getOperand(0);
1017  }
1018 
1019  if (OtherAddOp) {
1020  // So at this point we know we have (Y -> OtherAddOp):
1021  // select C, (add X, Y), (sub X, Z)
1022  Value *NegVal; // Compute -Z
1023  if (SI.getType()->isFPOrFPVectorTy()) {
1024  NegVal = Builder->CreateFNeg(SubOp->getOperand(1));
1025  if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) {
1027  Flags &= SubOp->getFastMathFlags();
1028  NegInst->setFastMathFlags(Flags);
1029  }
1030  } else {
1031  NegVal = Builder->CreateNeg(SubOp->getOperand(1));
1032  }
1033 
1034  Value *NewTrueOp = OtherAddOp;
1035  Value *NewFalseOp = NegVal;
1036  if (AddOp != TI)
1037  std::swap(NewTrueOp, NewFalseOp);
1038  Value *NewSel =
1039  Builder->CreateSelect(CondVal, NewTrueOp,
1040  NewFalseOp, SI.getName() + ".p");
1041 
1042  if (SI.getType()->isFPOrFPVectorTy()) {
1043  Instruction *RI =
1044  BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel);
1045 
1046  FastMathFlags Flags = AddOp->getFastMathFlags();
1047  Flags &= SubOp->getFastMathFlags();
1048  RI->setFastMathFlags(Flags);
1049  return RI;
1050  } else
1051  return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
1052  }
1053  }
1054  }
1055 
1056  // See if we can fold the select into one of our operands.
1057  if (SI.getType()->isIntOrIntVectorTy()) {
1058  if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
1059  return FoldI;
1060 
1061  Value *LHS, *RHS, *LHS2, *RHS2;
1062  Instruction::CastOps CastOp;
1063  SelectPatternFlavor SPF = matchSelectPattern(&SI, LHS, RHS, &CastOp);
1064 
1065  if (SPF) {
1066  // Canonicalize so that type casts are outside select patterns.
1067  if (LHS->getType()->getPrimitiveSizeInBits() !=
1068  SI.getType()->getPrimitiveSizeInBits()) {
1070  Value *Cmp = Builder->CreateICmp(Pred, LHS, RHS);
1071  Value *NewSI = Builder->CreateCast(CastOp,
1072  Builder->CreateSelect(Cmp, LHS, RHS),
1073  SI.getType());
1074  return ReplaceInstUsesWith(SI, NewSI);
1075  }
1076 
1077  // MAX(MAX(a, b), a) -> MAX(a, b)
1078  // MIN(MIN(a, b), a) -> MIN(a, b)
1079  // MAX(MIN(a, b), a) -> a
1080  // MIN(MAX(a, b), a) -> a
1081  if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2))
1082  if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
1083  SI, SPF, RHS))
1084  return R;
1085  if (SelectPatternFlavor SPF2 = matchSelectPattern(RHS, LHS2, RHS2))
1086  if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
1087  SI, SPF, LHS))
1088  return R;
1089  }
1090 
1091  // MAX(~a, ~b) -> ~MIN(a, b)
1092  if (SPF == SPF_SMAX || SPF == SPF_UMAX) {
1093  if (IsFreeToInvert(LHS, LHS->hasNUses(2)) &&
1094  IsFreeToInvert(RHS, RHS->hasNUses(2))) {
1095 
1096  // This transform adds a xor operation and that extra cost needs to be
1097  // justified. We look for simplifications that will result from
1098  // applying this rule:
1099 
1100  bool Profitable =
1101  (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) ||
1102  (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) ||
1103  (SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value())));
1104 
1105  if (Profitable) {
1106  Value *NewLHS = Builder->CreateNot(LHS);
1107  Value *NewRHS = Builder->CreateNot(RHS);
1108  Value *NewCmp = SPF == SPF_SMAX
1109  ? Builder->CreateICmpSLT(NewLHS, NewRHS)
1110  : Builder->CreateICmpULT(NewLHS, NewRHS);
1111  Value *NewSI =
1112  Builder->CreateNot(Builder->CreateSelect(NewCmp, NewLHS, NewRHS));
1113  return ReplaceInstUsesWith(SI, NewSI);
1114  }
1115  }
1116  }
1117 
1118  // TODO.
1119  // ABS(-X) -> ABS(X)
1120  }
1121 
1122  // See if we can fold the select into a phi node if the condition is a select.
1123  if (isa<PHINode>(SI.getCondition()))
1124  // The true/false values have to be live in the PHI predecessor's blocks.
1125  if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
1126  CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
1127  if (Instruction *NV = FoldOpIntoPhi(SI))
1128  return NV;
1129 
1130  if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
1131  if (TrueSI->getCondition()->getType() == CondVal->getType()) {
1132  // select(C, select(C, a, b), c) -> select(C, a, c)
1133  if (TrueSI->getCondition() == CondVal) {
1134  if (SI.getTrueValue() == TrueSI->getTrueValue())
1135  return nullptr;
1136  SI.setOperand(1, TrueSI->getTrueValue());
1137  return &SI;
1138  }
1139  // select(C0, select(C1, a, b), b) -> select(C0&C1, a, b)
1140  // We choose this as normal form to enable folding on the And and shortening
1141  // paths for the values (this helps GetUnderlyingObjects() for example).
1142  if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) {
1143  Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition());
1144  SI.setOperand(0, And);
1145  SI.setOperand(1, TrueSI->getTrueValue());
1146  return &SI;
1147  }
1148  }
1149  }
1150  if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
1151  if (FalseSI->getCondition()->getType() == CondVal->getType()) {
1152  // select(C, a, select(C, b, c)) -> select(C, a, c)
1153  if (FalseSI->getCondition() == CondVal) {
1154  if (SI.getFalseValue() == FalseSI->getFalseValue())
1155  return nullptr;
1156  SI.setOperand(2, FalseSI->getFalseValue());
1157  return &SI;
1158  }
1159  // select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b)
1160  if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) {
1161  Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition());
1162  SI.setOperand(0, Or);
1163  SI.setOperand(2, FalseSI->getFalseValue());
1164  return &SI;
1165  }
1166  }
1167  }
1168 
1169  if (BinaryOperator::isNot(CondVal)) {
1171  SI.setOperand(1, FalseVal);
1172  SI.setOperand(2, TrueVal);
1173  return &SI;
1174  }
1175 
1176  if (VectorType* VecTy = dyn_cast<VectorType>(SI.getType())) {
1177  unsigned VWidth = VecTy->getNumElements();
1178  APInt UndefElts(VWidth, 0);
1179  APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth));
1180  if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) {
1181  if (V != &SI)
1182  return ReplaceInstUsesWith(SI, V);
1183  return &SI;
1184  }
1185 
1186  if (isa<ConstantAggregateZero>(CondVal)) {
1187  return ReplaceInstUsesWith(SI, FalseVal);
1188  }
1189  }
1190 
1191  return nullptr;
1192 }
Value * CreateLShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:842
BinaryOp_match< LHS, RHS, Instruction::And > m_And(const LHS &L, const RHS &R)
Definition: PatternMatch.h:506
Instruction * FoldSPFofSPF(Instruction *Inner, SelectPatternFlavor SPF1, Value *A, Value *B, Instruction &Outer, SelectPatternFlavor SPF2, Value *C)
class_match< Value > m_Value()
Match an arbitrary value and ignore it.
Definition: PatternMatch.h:64
Value * CreateCast(Instruction::CastOps Op, Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:1285
static APInt getSignBit(unsigned BitWidth)
Get the SignBit for a specific bit width.
Definition: APInt.h:446
void setFastMathFlags(FastMathFlags FMF)
Convenience function for setting multiple fast-math flags on this instruction, which must be an opera...
static bool IsFreeToInvert(Value *V, bool WillInvertAllUses)
Return true if the specified value is free to invert (apply ~ to).
static APInt getAllOnesValue(unsigned numBits)
Get the all-ones value.
Definition: APInt.h:453
Value * CreateICmp(CmpInst::Predicate P, Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1442
Value * CreateICmpSLT(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1378
match_zero m_Zero()
Match an arbitrary zero/null constant.
Definition: PatternMatch.h:137
bool hasNUses(unsigned N) const
Return true if this Value has exactly N users.
Definition: Value.cpp:96
unsigned getBitWidth() const
getBitWidth - Return the bitwidth of this constant.
Definition: Constants.h:111
This class represents zero extension of integer types.
unsigned getNumOperands() const
Definition: User.h:138
static Constant * GetSelectFoldableConstant(Instruction *I)
GetSelectFoldableConstant - For the same transformation as the previous function, return the identity...
unsigned less than
Definition: InstrTypes.h:722
Value * CreateICmpULT(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1366
1 1 1 0 True if unordered or not equal
Definition: InstrTypes.h:713
static bool isEquality(Predicate P)
isEquality - Return true if this predicate is either EQ or NE.
FastMathFlags getFastMathFlags() const
Convenience function for getting all the fast-math flags, which must be an operator which supports th...
This class represents a sign extension of integer types.
unsigned getBitWidth() const
Get the number of bits in this IntegerType.
Definition: DerivedTypes.h:61
static CmpInst::Predicate getICmpPredicateForMinMax(SelectPatternFlavor SPF)
InstTy * Insert(InstTy *I, const Twine &Name="") const
Insert and return the specified instruction.
Definition: IRBuilder.h:565
static Constant * getNullValue(Type *Ty)
Definition: Constants.cpp:178
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:188
bool isCast() const
Definition: Instruction.h:118
SelectPatternFlavor matchSelectPattern(Value *V, Value *&LHS, Value *&RHS, Instruction::CastOps *CastOp=nullptr)
Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind and providing the out param...
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:41
Value * CreateXor(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:910
BinaryOp_match< LHS, RHS, Instruction::Xor > m_Xor(const LHS &L, const RHS &R)
Definition: PatternMatch.h:518
SelectInst - This class represents the LLVM 'select' instruction.
const APInt & getValue() const
Return the constant as an APInt value reference.
Definition: Constants.h:106
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
Definition: ErrorHandling.h:98
CastClass_match< OpTy, Instruction::Trunc > m_Trunc(const OpTy &Op)
Matches Trunc.
Definition: PatternMatch.h:801
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:517
static Constant * getSExt(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1713
static SelectPatternFlavor getInverseMinMaxSelectPattern(SelectPatternFlavor SPF)
Instruction * clone() const
clone() - Create a copy of 'this' instruction that is identical in all ways except the following: ...
not_match< LHS > m_Not(const LHS &L)
Definition: PatternMatch.h:854
static Constant * getZExt(Constant *C, Type *Ty, bool OnlyIfReduced=false)
Definition: Constants.cpp:1727
Value * CreateFCmp(CmpInst::Predicate P, Value *LHS, Value *RHS, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:1449
Value * CreateAnd(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:878
static SelectInst * Create(Value *C, Value *S1, Value *S2, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
Value * CreateOr(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:894
CastClass_match< OpTy, Instruction::ZExt > m_ZExt(const OpTy &Op)
Matches ZExt.
Definition: PatternMatch.h:813
This instruction compares its operands according to the predicate given to the constructor.
bool sgt(const APInt &RHS) const
Signed greather than comparison.
Definition: APInt.h:1119
class_match< ConstantInt > m_ConstantInt()
Match an arbitrary ConstantInt and ignore it.
Definition: PatternMatch.h:75
cst_pred_ty< is_power2 > m_Power2()
Match an integer or vector power of 2.
Definition: PatternMatch.h:272
Value * CreateAShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:860
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:256
static BinaryOperator * CreateAdd(Value *S1, Value *S2, const Twine &Name, Instruction *InsertBefore, Value *FlagsOp)
static const Value * getNotArgument(const Value *BinOp)
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.cpp:520
void replaceUsesOfWith(Value *From, Value *To)
Replace uses of one Value with another.
Definition: User.cpp:24
bool isIntOrIntVectorTy() const
isIntOrIntVectorTy - Return true if this is an integer type or a vector of integer types...
Definition: Type.h:201
apint_match m_APInt(const APInt *&Res)
Match a ConstantInt or splatted ConstantVector, binding the specified pointer to the contained APInt...
Definition: PatternMatch.h:180
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
BinaryOp_match< LHS, RHS, Instruction::Or > m_Or(const LHS &L, const RHS &R)
Definition: PatternMatch.h:512
bool isVectorTy() const
isVectorTy - True if this is an instance of VectorType.
Definition: Type.h:226
Value * CreateNot(Value *V, const Twine &Name="")
Definition: IRBuilder.h:957
bool sge(const APInt &RHS) const
Signed greather or equal comparison.
Definition: APInt.h:1153
bool isEquality() const
isEquality - Return true if this predicate is either EQ or NE.
Value * CreateAdd(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:704
This is an important base class in LLVM.
Definition: Constant.h:41
const Value * getCondition() const
APInt Or(const APInt &LHS, const APInt &RHS)
Bitwise OR function for APInt.
Definition: APInt.h:1895
ConstantFP - Floating Point Values [float, double].
Definition: Constants.h:233
APInt Xor(const APInt &LHS, const APInt &RHS)
Bitwise XOR function for APInt.
Definition: APInt.h:1900
cst_pred_ty< is_all_ones > m_AllOnes()
Match an integer or vector with all bits set to true.
Definition: PatternMatch.h:252
specificval_ty m_Specific(const Value *V)
Match if we have a specific specified value.
Definition: PatternMatch.h:322
bool sle(const APInt &RHS) const
Signed less or equal comparison.
Definition: APInt.h:1085
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang","erlang-compatible garbage collector")
This instruction compares its operands according to the predicate given to the constructor.
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:697
bool uge(const APInt &RHS) const
Unsigned greater or equal comparison.
Definition: APInt.h:1137
Instruction * FoldSelectIntoOp(SelectInst &SI, Value *, Value *)
FoldSelectIntoOp - Try fold the select into one of the operands to facilitate further optimization...
Value * getOperand(unsigned i) const
Definition: User.h:118
bool isCommutative() const
isCommutative - Return true if the instruction is commutative:
Definition: Instruction.h:327
static bool isNot(const Value *V)
static Value * foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal, Value *FalseVal, InstCombiner::BuilderTy *Builder)
foldSelectICmpAndOr - We want to turn: (select (icmp eq (and X, C1), 0), Y, (or Y, C2)) into: (or (shl (and X, C1), C3), y) iff: C1 and C2 are both powers of 2 where: C3 = Log(C2) - Log(C1)
Class to represent integer types.
Definition: DerivedTypes.h:37
Predicate getPredicate() const
Return the predicate for this instruction.
Definition: InstrTypes.h:760
Instruction * FoldSelectOpOp(SelectInst &SI, Instruction *TI, Instruction *FI)
FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI have the same opcode and...
static Constant * getAllOnesValue(Type *Ty)
Get the all ones value.
Definition: Constants.cpp:230
Value * SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, const DataLayout &DL, const TargetLibraryInfo *TLI=nullptr, const DominatorTree *DT=nullptr, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr)
SimplifySelectInst - Given operands for a SelectInst, see if we can fold the result.
LLVMContext & getContext() const
Definition: IRBuilder.h:81
bool isFPOrFPVectorTy() const
isFPOrFPVectorTy - Return true if this is a FP type or a vector of FP.
Definition: Type.h:183
bool hasNoSignedWrap() const
Determine whether the no signed wrap flag is set.
const Value * getTrueValue() const
bool isPowerOf2() const
Check if this APInt's value is a power of two greater than zero.
Definition: APInt.h:386
signed greater than
Definition: InstrTypes.h:724
void setIsExact(bool b=true)
Set or clear the exact flag on this instruction, which must be an operator which supports this flag...
CastClass_match< OpTy, Instruction::SExt > m_SExt(const OpTy &Op)
Matches SExt.
Definition: PatternMatch.h:807
bool ugt(const APInt &RHS) const
Unsigned greather than comparison.
Definition: APInt.h:1101
BinaryOps getOpcode() const
Definition: InstrTypes.h:323
Instruction * visitSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI)
This is the shared class of boolean and integer constants.
Definition: Constants.h:47
bool slt(const APInt &RHS) const
Signed less than comparison.
Definition: APInt.cpp:552
unsigned getVectorNumElements() const
Definition: Type.cpp:212
unsigned getScalarSizeInBits() const LLVM_READONLY
getScalarSizeInBits - If this is a vector type, return the getPrimitiveSizeInBits value for the eleme...
Definition: Type.cpp:139
static Value * generateMinMaxSelectPattern(InstCombiner::BuilderTy *Builder, SelectPatternFlavor SPF, Value *A, Value *B)
unsigned logBase2() const
Definition: APInt.h:1521
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:222
SelectPatternFlavor
Specific patterns of select instructions we can match.
signed less than
Definition: InstrTypes.h:726
Predicate getSwappedPredicate() const
For example, EQ->EQ, SLE->SGE, ULT->UGT, OEQ->OEQ, ULE->UGE, OLT->OGT, etc.
Definition: InstrTypes.h:799
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:582
bool isZero() const
This is just a convenience method to make client code smaller for a common code.
Definition: Constants.h:161
bool isExact() const
Determine whether the exact flag is set.
Instruction * visitSelectInst(SelectInst &SI)
void setPredicate(Predicate P)
Set the predicate for this instruction to the specified value.
Definition: InstrTypes.h:765
void setOperand(unsigned i, Value *Val)
Definition: User.h:122
bool isAllOnesValue() const
isAllOnesValue - Return true if this is the value that would be returned by getAllOnesValue.
Definition: Constants.cpp:88
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:576
Value * getArgOperand(unsigned i) const
getArgOperand/setArgOperand - Return/set the i-th call argument.
VectorType - Class to represent vector types.
Definition: DerivedTypes.h:362
Class for arbitrary precision integers.
Definition: APInt.h:73
bool isIntegerTy() const
isIntegerTy - True if this is an instance of IntegerType.
Definition: Type.h:193
static BinaryOperator * Create(BinaryOps Op, Value *S1, Value *S2, const Twine &Name=Twine(), Instruction *InsertBefore=nullptr)
Construct a binary instruction, given the opcode and the two operands.
Value * CreateSelect(Value *C, Value *True, Value *False, const Twine &Name="")
Definition: IRBuilder.h:1482
LLVM_ATTRIBUTE_UNUSED_RESULT std::enable_if< !is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:285
APInt And(const APInt &LHS, const APInt &RHS)
Bitwise AND function for APInt.
Definition: APInt.h:1890
Value * CreateShl(Value *LHS, Value *RHS, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:823
static CastInst * Create(Instruction::CastOps, Value *S, Type *Ty, const Twine &Name="", Instruction *InsertBefore=nullptr)
Provides a way to construct any of the CastInst subclasses using an opcode instead of the subclass's ...
Value * CreateZExtOrTrunc(Value *V, Type *DestTy, const Twine &Name="")
Create a ZExt or Trunc from the integer value V to DestTy.
Definition: IRBuilder.h:1200
#define I(x, y, z)
Definition: MD5.cpp:54
bool hasOneUse() const
Return true if there is exactly one user of this value.
Definition: Value.h:311
void setArgOperand(unsigned i, Value *v)
bool hasNUsesOrMore(unsigned N) const
Return true if this value has N users or more.
Definition: Value.cpp:104
const APFloat & getValueAPF() const
Definition: Constants.h:270
bool isUnsigned() const
Determine if this instruction is using an unsigned comparison.
Definition: InstrTypes.h:832
user_iterator user_begin()
Definition: Value.h:294
Value * CreateNeg(Value *V, const Twine &Name="", bool HasNUW=false, bool HasNSW=false)
Definition: IRBuilder.h:935
unsigned getPrimitiveSizeInBits() const LLVM_READONLY
getPrimitiveSizeInBits - Return the basic size of this type if it is a primitive type.
Definition: Type.cpp:121
0 0 0 1 True if ordered and equal
Definition: InstrTypes.h:700
LLVM Value Representation.
Definition: Value.h:69
bool hasNoUnsignedWrap() const
Determine whether the no unsigned wrap flag is set.
This file provides internal interfaces used to implement the InstCombine.
unsigned getOpcode() const
getOpcode() returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:112
bool isZero() const
Returns true if and only if the float is plus or minus zero.
Definition: APFloat.h:414
static bool isUnordered(unsigned short predicate)
Determine if the predicate is an unordered operation.
void moveBefore(Instruction *MovePos)
moveBefore - Unlink this instruction from its current basic block and insert it into the basic block ...
Definition: Instruction.cpp:89
static bool isSelect01(Constant *C1, Constant *C2)
static unsigned GetSelectFoldableOperands(Instruction *I)
GetSelectFoldableOperands - We want to turn code that looks like this: C = or A, B D = select cond...
C - The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
const Value * getFalseValue() const
Convenience struct for specifying and reasoning about fast-math flags.
Definition: Operator.h:164
unsigned greater than
Definition: InstrTypes.h:720
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml","ocaml 3.10-compatible collector")
specific_intval m_SpecificInt(uint64_t V)
Match a specific integer value or vector with all elements equal to the value.
Definition: PatternMatch.h:383
Value * CreateFNeg(Value *V, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:950
bool ule(const APInt &RHS) const
Unsigned less or equal comparison.
Definition: APInt.h:1069
const BasicBlock * getParent() const
Definition: Instruction.h:72
bool isOne() const
This is just a convenience method to make client code smaller for a common case.
Definition: Constants.h:169
IntrinsicInst - A useful wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:37