LLVM  7.0.0svn
InstCombineCompares.cpp
Go to the documentation of this file.
1 //===- InstCombineCompares.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 visitICmp and visitFCmp functions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "InstCombineInternal.h"
15 #include "llvm/ADT/APSInt.h"
16 #include "llvm/ADT/SetVector.h"
17 #include "llvm/ADT/Statistic.h"
21 #include "llvm/IR/ConstantRange.h"
22 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/PatternMatch.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/KnownBits.h"
28 
29 using namespace llvm;
30 using namespace PatternMatch;
31 
32 #define DEBUG_TYPE "instcombine"
33 
34 // How many times is a select replaced by one of its operands?
35 STATISTIC(NumSel, "Number of select opts");
36 
37 
38 /// Compute Result = In1+In2, returning true if the result overflowed for this
39 /// type.
40 static bool addWithOverflow(APInt &Result, const APInt &In1,
41  const APInt &In2, bool IsSigned = false) {
42  bool Overflow;
43  if (IsSigned)
44  Result = In1.sadd_ov(In2, Overflow);
45  else
46  Result = In1.uadd_ov(In2, Overflow);
47 
48  return Overflow;
49 }
50 
51 /// Compute Result = In1-In2, returning true if the result overflowed for this
52 /// type.
53 static bool subWithOverflow(APInt &Result, const APInt &In1,
54  const APInt &In2, bool IsSigned = false) {
55  bool Overflow;
56  if (IsSigned)
57  Result = In1.ssub_ov(In2, Overflow);
58  else
59  Result = In1.usub_ov(In2, Overflow);
60 
61  return Overflow;
62 }
63 
64 /// Given an icmp instruction, return true if any use of this comparison is a
65 /// branch on sign bit comparison.
66 static bool hasBranchUse(ICmpInst &I) {
67  for (auto *U : I.users())
68  if (isa<BranchInst>(U))
69  return true;
70  return false;
71 }
72 
73 /// Given an exploded icmp instruction, return true if the comparison only
74 /// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if the
75 /// result of the comparison is true when the input value is signed.
76 static bool isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
77  bool &TrueIfSigned) {
78  switch (Pred) {
79  case ICmpInst::ICMP_SLT: // True if LHS s< 0
80  TrueIfSigned = true;
81  return RHS.isNullValue();
82  case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
83  TrueIfSigned = true;
84  return RHS.isAllOnesValue();
85  case ICmpInst::ICMP_SGT: // True if LHS s> -1
86  TrueIfSigned = false;
87  return RHS.isAllOnesValue();
88  case ICmpInst::ICMP_UGT:
89  // True if LHS u> RHS and RHS == high-bit-mask - 1
90  TrueIfSigned = true;
91  return RHS.isMaxSignedValue();
92  case ICmpInst::ICMP_UGE:
93  // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
94  TrueIfSigned = true;
95  return RHS.isSignMask();
96  default:
97  return false;
98  }
99 }
100 
101 /// Returns true if the exploded icmp can be expressed as a signed comparison
102 /// to zero and updates the predicate accordingly.
103 /// The signedness of the comparison is preserved.
104 /// TODO: Refactor with decomposeBitTestICmp()?
105 static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
106  if (!ICmpInst::isSigned(Pred))
107  return false;
108 
109  if (C.isNullValue())
110  return ICmpInst::isRelational(Pred);
111 
112  if (C.isOneValue()) {
113  if (Pred == ICmpInst::ICMP_SLT) {
114  Pred = ICmpInst::ICMP_SLE;
115  return true;
116  }
117  } else if (C.isAllOnesValue()) {
118  if (Pred == ICmpInst::ICMP_SGT) {
119  Pred = ICmpInst::ICMP_SGE;
120  return true;
121  }
122  }
123 
124  return false;
125 }
126 
127 /// Given a signed integer type and a set of known zero and one bits, compute
128 /// the maximum and minimum values that could have the specified known zero and
129 /// known one bits, returning them in Min/Max.
130 /// TODO: Move to method on KnownBits struct?
132  APInt &Min, APInt &Max) {
133  assert(Known.getBitWidth() == Min.getBitWidth() &&
134  Known.getBitWidth() == Max.getBitWidth() &&
135  "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
136  APInt UnknownBits = ~(Known.Zero|Known.One);
137 
138  // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
139  // bit if it is unknown.
140  Min = Known.One;
141  Max = Known.One|UnknownBits;
142 
143  if (UnknownBits.isNegative()) { // Sign bit is unknown
144  Min.setSignBit();
145  Max.clearSignBit();
146  }
147 }
148 
149 /// Given an unsigned integer type and a set of known zero and one bits, compute
150 /// the maximum and minimum values that could have the specified known zero and
151 /// known one bits, returning them in Min/Max.
152 /// TODO: Move to method on KnownBits struct?
154  APInt &Min, APInt &Max) {
155  assert(Known.getBitWidth() == Min.getBitWidth() &&
156  Known.getBitWidth() == Max.getBitWidth() &&
157  "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
158  APInt UnknownBits = ~(Known.Zero|Known.One);
159 
160  // The minimum value is when the unknown bits are all zeros.
161  Min = Known.One;
162  // The maximum value is when the unknown bits are all ones.
163  Max = Known.One|UnknownBits;
164 }
165 
166 /// This is called when we see this pattern:
167 /// cmp pred (load (gep GV, ...)), cmpcst
168 /// where GV is a global variable with a constant initializer. Try to simplify
169 /// this into some simple computation that does not need the load. For example
170 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
171 ///
172 /// If AndCst is non-null, then the loaded value is masked with that constant
173 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
174 Instruction *InstCombiner::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
175  GlobalVariable *GV,
176  CmpInst &ICI,
177  ConstantInt *AndCst) {
178  Constant *Init = GV->getInitializer();
179  if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
180  return nullptr;
181 
182  uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
183  // Don't blow up on huge arrays.
184  if (ArrayElementCount > MaxArraySizeForCombine)
185  return nullptr;
186 
187  // There are many forms of this optimization we can handle, for now, just do
188  // the simple index into a single-dimensional array.
189  //
190  // Require: GEP GV, 0, i {{, constant indices}}
191  if (GEP->getNumOperands() < 3 ||
192  !isa<ConstantInt>(GEP->getOperand(1)) ||
193  !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
194  isa<Constant>(GEP->getOperand(2)))
195  return nullptr;
196 
197  // Check that indices after the variable are constants and in-range for the
198  // type they index. Collect the indices. This is typically for arrays of
199  // structs.
200  SmallVector<unsigned, 4> LaterIndices;
201 
202  Type *EltTy = Init->getType()->getArrayElementType();
203  for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
204  ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
205  if (!Idx) return nullptr; // Variable index.
206 
207  uint64_t IdxVal = Idx->getZExtValue();
208  if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
209 
210  if (StructType *STy = dyn_cast<StructType>(EltTy))
211  EltTy = STy->getElementType(IdxVal);
212  else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
213  if (IdxVal >= ATy->getNumElements()) return nullptr;
214  EltTy = ATy->getElementType();
215  } else {
216  return nullptr; // Unknown type.
217  }
218 
219  LaterIndices.push_back(IdxVal);
220  }
221 
222  enum { Overdefined = -3, Undefined = -2 };
223 
224  // Variables for our state machines.
225 
226  // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
227  // "i == 47 | i == 87", where 47 is the first index the condition is true for,
228  // and 87 is the second (and last) index. FirstTrueElement is -2 when
229  // undefined, otherwise set to the first true element. SecondTrueElement is
230  // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
231  int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
232 
233  // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
234  // form "i != 47 & i != 87". Same state transitions as for true elements.
235  int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
236 
237  /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
238  /// define a state machine that triggers for ranges of values that the index
239  /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
240  /// This is -2 when undefined, -3 when overdefined, and otherwise the last
241  /// index in the range (inclusive). We use -2 for undefined here because we
242  /// use relative comparisons and don't want 0-1 to match -1.
243  int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
244 
245  // MagicBitvector - This is a magic bitvector where we set a bit if the
246  // comparison is true for element 'i'. If there are 64 elements or less in
247  // the array, this will fully represent all the comparison results.
248  uint64_t MagicBitvector = 0;
249 
250  // Scan the array and see if one of our patterns matches.
251  Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
252  for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
253  Constant *Elt = Init->getAggregateElement(i);
254  if (!Elt) return nullptr;
255 
256  // If this is indexing an array of structures, get the structure element.
257  if (!LaterIndices.empty())
258  Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
259 
260  // If the element is masked, handle it.
261  if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
262 
263  // Find out if the comparison would be true or false for the i'th element.
265  CompareRHS, DL, &TLI);
266  // If the result is undef for this element, ignore it.
267  if (isa<UndefValue>(C)) {
268  // Extend range state machines to cover this element in case there is an
269  // undef in the middle of the range.
270  if (TrueRangeEnd == (int)i-1)
271  TrueRangeEnd = i;
272  if (FalseRangeEnd == (int)i-1)
273  FalseRangeEnd = i;
274  continue;
275  }
276 
277  // If we can't compute the result for any of the elements, we have to give
278  // up evaluating the entire conditional.
279  if (!isa<ConstantInt>(C)) return nullptr;
280 
281  // Otherwise, we know if the comparison is true or false for this element,
282  // update our state machines.
283  bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
284 
285  // State machine for single/double/range index comparison.
286  if (IsTrueForElt) {
287  // Update the TrueElement state machine.
288  if (FirstTrueElement == Undefined)
289  FirstTrueElement = TrueRangeEnd = i; // First true element.
290  else {
291  // Update double-compare state machine.
292  if (SecondTrueElement == Undefined)
293  SecondTrueElement = i;
294  else
295  SecondTrueElement = Overdefined;
296 
297  // Update range state machine.
298  if (TrueRangeEnd == (int)i-1)
299  TrueRangeEnd = i;
300  else
301  TrueRangeEnd = Overdefined;
302  }
303  } else {
304  // Update the FalseElement state machine.
305  if (FirstFalseElement == Undefined)
306  FirstFalseElement = FalseRangeEnd = i; // First false element.
307  else {
308  // Update double-compare state machine.
309  if (SecondFalseElement == Undefined)
310  SecondFalseElement = i;
311  else
312  SecondFalseElement = Overdefined;
313 
314  // Update range state machine.
315  if (FalseRangeEnd == (int)i-1)
316  FalseRangeEnd = i;
317  else
318  FalseRangeEnd = Overdefined;
319  }
320  }
321 
322  // If this element is in range, update our magic bitvector.
323  if (i < 64 && IsTrueForElt)
324  MagicBitvector |= 1ULL << i;
325 
326  // If all of our states become overdefined, bail out early. Since the
327  // predicate is expensive, only check it every 8 elements. This is only
328  // really useful for really huge arrays.
329  if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
330  SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
331  FalseRangeEnd == Overdefined)
332  return nullptr;
333  }
334 
335  // Now that we've scanned the entire array, emit our new comparison(s). We
336  // order the state machines in complexity of the generated code.
337  Value *Idx = GEP->getOperand(2);
338 
339  // If the index is larger than the pointer size of the target, truncate the
340  // index down like the GEP would do implicitly. We don't have to do this for
341  // an inbounds GEP because the index can't be out of range.
342  if (!GEP->isInBounds()) {
343  Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
344  unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
345  if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
346  Idx = Builder.CreateTrunc(Idx, IntPtrTy);
347  }
348 
349  // If the comparison is only true for one or two elements, emit direct
350  // comparisons.
351  if (SecondTrueElement != Overdefined) {
352  // None true -> false.
353  if (FirstTrueElement == Undefined)
354  return replaceInstUsesWith(ICI, Builder.getFalse());
355 
356  Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
357 
358  // True for one element -> 'i == 47'.
359  if (SecondTrueElement == Undefined)
360  return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
361 
362  // True for two elements -> 'i == 47 | i == 72'.
363  Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
364  Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
365  Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
366  return BinaryOperator::CreateOr(C1, C2);
367  }
368 
369  // If the comparison is only false for one or two elements, emit direct
370  // comparisons.
371  if (SecondFalseElement != Overdefined) {
372  // None false -> true.
373  if (FirstFalseElement == Undefined)
374  return replaceInstUsesWith(ICI, Builder.getTrue());
375 
376  Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
377 
378  // False for one element -> 'i != 47'.
379  if (SecondFalseElement == Undefined)
380  return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
381 
382  // False for two elements -> 'i != 47 & i != 72'.
383  Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
384  Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
385  Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
386  return BinaryOperator::CreateAnd(C1, C2);
387  }
388 
389  // If the comparison can be replaced with a range comparison for the elements
390  // where it is true, emit the range check.
391  if (TrueRangeEnd != Overdefined) {
392  assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
393 
394  // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
395  if (FirstTrueElement) {
396  Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
397  Idx = Builder.CreateAdd(Idx, Offs);
398  }
399 
400  Value *End = ConstantInt::get(Idx->getType(),
401  TrueRangeEnd-FirstTrueElement+1);
402  return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
403  }
404 
405  // False range check.
406  if (FalseRangeEnd != Overdefined) {
407  assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
408  // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
409  if (FirstFalseElement) {
410  Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
411  Idx = Builder.CreateAdd(Idx, Offs);
412  }
413 
414  Value *End = ConstantInt::get(Idx->getType(),
415  FalseRangeEnd-FirstFalseElement);
416  return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
417  }
418 
419  // If a magic bitvector captures the entire comparison state
420  // of this load, replace it with computation that does:
421  // ((magic_cst >> i) & 1) != 0
422  {
423  Type *Ty = nullptr;
424 
425  // Look for an appropriate type:
426  // - The type of Idx if the magic fits
427  // - The smallest fitting legal type
428  if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
429  Ty = Idx->getType();
430  else
431  Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
432 
433  if (Ty) {
434  Value *V = Builder.CreateIntCast(Idx, Ty, false);
435  V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
436  V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
437  return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
438  }
439  }
440 
441  return nullptr;
442 }
443 
444 /// Return a value that can be used to compare the *offset* implied by a GEP to
445 /// zero. For example, if we have &A[i], we want to return 'i' for
446 /// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
447 /// are involved. The above expression would also be legal to codegen as
448 /// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
449 /// This latter form is less amenable to optimization though, and we are allowed
450 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
451 ///
452 /// If we can't emit an optimized form for this expression, this returns null.
453 ///
455  const DataLayout &DL) {
457 
458  // Check to see if this gep only has a single variable index. If so, and if
459  // any constant indices are a multiple of its scale, then we can compute this
460  // in terms of the scale of the variable index. For example, if the GEP
461  // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
462  // because the expression will cross zero at the same point.
463  unsigned i, e = GEP->getNumOperands();
464  int64_t Offset = 0;
465  for (i = 1; i != e; ++i, ++GTI) {
466  if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
467  // Compute the aggregate offset of constant indices.
468  if (CI->isZero()) continue;
469 
470  // Handle a struct index, which adds its field offset to the pointer.
471  if (StructType *STy = GTI.getStructTypeOrNull()) {
472  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
473  } else {
474  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
475  Offset += Size*CI->getSExtValue();
476  }
477  } else {
478  // Found our variable index.
479  break;
480  }
481  }
482 
483  // If there are no variable indices, we must have a constant offset, just
484  // evaluate it the general way.
485  if (i == e) return nullptr;
486 
487  Value *VariableIdx = GEP->getOperand(i);
488  // Determine the scale factor of the variable element. For example, this is
489  // 4 if the variable index is into an array of i32.
490  uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
491 
492  // Verify that there are no other variable indices. If so, emit the hard way.
493  for (++i, ++GTI; i != e; ++i, ++GTI) {
494  ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
495  if (!CI) return nullptr;
496 
497  // Compute the aggregate offset of constant indices.
498  if (CI->isZero()) continue;
499 
500  // Handle a struct index, which adds its field offset to the pointer.
501  if (StructType *STy = GTI.getStructTypeOrNull()) {
502  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
503  } else {
504  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
505  Offset += Size*CI->getSExtValue();
506  }
507  }
508 
509  // Okay, we know we have a single variable index, which must be a
510  // pointer/array/vector index. If there is no offset, life is simple, return
511  // the index.
512  Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
513  unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
514  if (Offset == 0) {
515  // Cast to intptrty in case a truncation occurs. If an extension is needed,
516  // we don't need to bother extending: the extension won't affect where the
517  // computation crosses zero.
518  if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
519  VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
520  }
521  return VariableIdx;
522  }
523 
524  // Otherwise, there is an index. The computation we will do will be modulo
525  // the pointer size, so get it.
526  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
527 
528  Offset &= PtrSizeMask;
529  VariableScale &= PtrSizeMask;
530 
531  // To do this transformation, any constant index must be a multiple of the
532  // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
533  // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
534  // multiple of the variable scale.
535  int64_t NewOffs = Offset / (int64_t)VariableScale;
536  if (Offset != NewOffs*(int64_t)VariableScale)
537  return nullptr;
538 
539  // Okay, we can do this evaluation. Start by converting the index to intptr.
540  if (VariableIdx->getType() != IntPtrTy)
541  VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
542  true /*Signed*/);
543  Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
544  return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
545 }
546 
547 /// Returns true if we can rewrite Start as a GEP with pointer Base
548 /// and some integer offset. The nodes that need to be re-written
549 /// for this transformation will be added to Explored.
550 static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
551  const DataLayout &DL,
552  SetVector<Value *> &Explored) {
553  SmallVector<Value *, 16> WorkList(1, Start);
554  Explored.insert(Base);
555 
556  // The following traversal gives us an order which can be used
557  // when doing the final transformation. Since in the final
558  // transformation we create the PHI replacement instructions first,
559  // we don't have to get them in any particular order.
560  //
561  // However, for other instructions we will have to traverse the
562  // operands of an instruction first, which means that we have to
563  // do a post-order traversal.
564  while (!WorkList.empty()) {
566 
567  while (!WorkList.empty()) {
568  if (Explored.size() >= 100)
569  return false;
570 
571  Value *V = WorkList.back();
572 
573  if (Explored.count(V) != 0) {
574  WorkList.pop_back();
575  continue;
576  }
577 
578  if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
579  !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
580  // We've found some value that we can't explore which is different from
581  // the base. Therefore we can't do this transformation.
582  return false;
583 
584  if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
585  auto *CI = dyn_cast<CastInst>(V);
586  if (!CI->isNoopCast(DL))
587  return false;
588 
589  if (Explored.count(CI->getOperand(0)) == 0)
590  WorkList.push_back(CI->getOperand(0));
591  }
592 
593  if (auto *GEP = dyn_cast<GEPOperator>(V)) {
594  // We're limiting the GEP to having one index. This will preserve
595  // the original pointer type. We could handle more cases in the
596  // future.
597  if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
598  GEP->getType() != Start->getType())
599  return false;
600 
601  if (Explored.count(GEP->getOperand(0)) == 0)
602  WorkList.push_back(GEP->getOperand(0));
603  }
604 
605  if (WorkList.back() == V) {
606  WorkList.pop_back();
607  // We've finished visiting this node, mark it as such.
608  Explored.insert(V);
609  }
610 
611  if (auto *PN = dyn_cast<PHINode>(V)) {
612  // We cannot transform PHIs on unsplittable basic blocks.
613  if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
614  return false;
615  Explored.insert(PN);
616  PHIs.insert(PN);
617  }
618  }
619 
620  // Explore the PHI nodes further.
621  for (auto *PN : PHIs)
622  for (Value *Op : PN->incoming_values())
623  if (Explored.count(Op) == 0)
624  WorkList.push_back(Op);
625  }
626 
627  // Make sure that we can do this. Since we can't insert GEPs in a basic
628  // block before a PHI node, we can't easily do this transformation if
629  // we have PHI node users of transformed instructions.
630  for (Value *Val : Explored) {
631  for (Value *Use : Val->uses()) {
632 
633  auto *PHI = dyn_cast<PHINode>(Use);
634  auto *Inst = dyn_cast<Instruction>(Val);
635 
636  if (Inst == Base || Inst == PHI || !Inst || !PHI ||
637  Explored.count(PHI) == 0)
638  continue;
639 
640  if (PHI->getParent() == Inst->getParent())
641  return false;
642  }
643  }
644  return true;
645 }
646 
647 // Sets the appropriate insert point on Builder where we can add
648 // a replacement Instruction for V (if that is possible).
649 static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
650  bool Before = true) {
651  if (auto *PHI = dyn_cast<PHINode>(V)) {
652  Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
653  return;
654  }
655  if (auto *I = dyn_cast<Instruction>(V)) {
656  if (!Before)
657  I = &*std::next(I->getIterator());
658  Builder.SetInsertPoint(I);
659  return;
660  }
661  if (auto *A = dyn_cast<Argument>(V)) {
662  // Set the insertion point in the entry block.
663  BasicBlock &Entry = A->getParent()->getEntryBlock();
664  Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
665  return;
666  }
667  // Otherwise, this is a constant and we don't need to set a new
668  // insertion point.
669  assert(isa<Constant>(V) && "Setting insertion point for unknown value!");
670 }
671 
672 /// Returns a re-written value of Start as an indexed GEP using Base as a
673 /// pointer.
675  const DataLayout &DL,
676  SetVector<Value *> &Explored) {
677  // Perform all the substitutions. This is a bit tricky because we can
678  // have cycles in our use-def chains.
679  // 1. Create the PHI nodes without any incoming values.
680  // 2. Create all the other values.
681  // 3. Add the edges for the PHI nodes.
682  // 4. Emit GEPs to get the original pointers.
683  // 5. Remove the original instructions.
684  Type *IndexType = IntegerType::get(
685  Base->getContext(), DL.getIndexTypeSizeInBits(Start->getType()));
686 
688  NewInsts[Base] = ConstantInt::getNullValue(IndexType);
689 
690  // Create the new PHI nodes, without adding any incoming values.
691  for (Value *Val : Explored) {
692  if (Val == Base)
693  continue;
694  // Create empty phi nodes. This avoids cyclic dependencies when creating
695  // the remaining instructions.
696  if (auto *PHI = dyn_cast<PHINode>(Val))
697  NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
698  PHI->getName() + ".idx", PHI);
699  }
700  IRBuilder<> Builder(Base->getContext());
701 
702  // Create all the other instructions.
703  for (Value *Val : Explored) {
704 
705  if (NewInsts.find(Val) != NewInsts.end())
706  continue;
707 
708  if (auto *CI = dyn_cast<CastInst>(Val)) {
709  NewInsts[CI] = NewInsts[CI->getOperand(0)];
710  continue;
711  }
712  if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
713  Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
714  : GEP->getOperand(1);
715  setInsertionPoint(Builder, GEP);
716  // Indices might need to be sign extended. GEPs will magically do
717  // this, but we need to do it ourselves here.
718  if (Index->getType()->getScalarSizeInBits() !=
719  NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
720  Index = Builder.CreateSExtOrTrunc(
721  Index, NewInsts[GEP->getOperand(0)]->getType(),
722  GEP->getOperand(0)->getName() + ".sext");
723  }
724 
725  auto *Op = NewInsts[GEP->getOperand(0)];
726  if (isa<ConstantInt>(Op) && cast<ConstantInt>(Op)->isZero())
727  NewInsts[GEP] = Index;
728  else
729  NewInsts[GEP] = Builder.CreateNSWAdd(
730  Op, Index, GEP->getOperand(0)->getName() + ".add");
731  continue;
732  }
733  if (isa<PHINode>(Val))
734  continue;
735 
736  llvm_unreachable("Unexpected instruction type");
737  }
738 
739  // Add the incoming values to the PHI nodes.
740  for (Value *Val : Explored) {
741  if (Val == Base)
742  continue;
743  // All the instructions have been created, we can now add edges to the
744  // phi nodes.
745  if (auto *PHI = dyn_cast<PHINode>(Val)) {
746  PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
747  for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
748  Value *NewIncoming = PHI->getIncomingValue(I);
749 
750  if (NewInsts.find(NewIncoming) != NewInsts.end())
751  NewIncoming = NewInsts[NewIncoming];
752 
753  NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
754  }
755  }
756  }
757 
758  for (Value *Val : Explored) {
759  if (Val == Base)
760  continue;
761 
762  // Depending on the type, for external users we have to emit
763  // a GEP or a GEP + ptrtoint.
764  setInsertionPoint(Builder, Val, false);
765 
766  // If required, create an inttoptr instruction for Base.
767  Value *NewBase = Base;
768  if (!Base->getType()->isPointerTy())
769  NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
770  Start->getName() + "to.ptr");
771 
772  Value *GEP = Builder.CreateInBoundsGEP(
773  Start->getType()->getPointerElementType(), NewBase,
774  makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
775 
776  if (!Val->getType()->isPointerTy()) {
777  Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
778  Val->getName() + ".conv");
779  GEP = Cast;
780  }
781  Val->replaceAllUsesWith(GEP);
782  }
783 
784  return NewInsts[Start];
785 }
786 
787 /// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
788 /// the input Value as a constant indexed GEP. Returns a pair containing
789 /// the GEPs Pointer and Index.
790 static std::pair<Value *, Value *>
792  Type *IndexType = IntegerType::get(V->getContext(),
794 
796  while (true) {
797  if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
798  // We accept only inbouds GEPs here to exclude the possibility of
799  // overflow.
800  if (!GEP->isInBounds())
801  break;
802  if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
803  GEP->getType() == V->getType()) {
804  V = GEP->getOperand(0);
805  Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
806  Index = ConstantExpr::getAdd(
807  Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
808  continue;
809  }
810  break;
811  }
812  if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
813  if (!CI->isNoopCast(DL))
814  break;
815  V = CI->getOperand(0);
816  continue;
817  }
818  if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
819  if (!CI->isNoopCast(DL))
820  break;
821  V = CI->getOperand(0);
822  continue;
823  }
824  break;
825  }
826  return {V, Index};
827 }
828 
829 /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
830 /// We can look through PHIs, GEPs and casts in order to determine a common base
831 /// between GEPLHS and RHS.
833  ICmpInst::Predicate Cond,
834  const DataLayout &DL) {
835  if (!GEPLHS->hasAllConstantIndices())
836  return nullptr;
837 
838  // Make sure the pointers have the same type.
839  if (GEPLHS->getType() != RHS->getType())
840  return nullptr;
841 
842  Value *PtrBase, *Index;
843  std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
844 
845  // The set of nodes that will take part in this transformation.
846  SetVector<Value *> Nodes;
847 
848  if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
849  return nullptr;
850 
851  // We know we can re-write this as
852  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
853  // Since we've only looked through inbouds GEPs we know that we
854  // can't have overflow on either side. We can therefore re-write
855  // this as:
856  // OFFSET1 cmp OFFSET2
857  Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
858 
859  // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
860  // GEP having PtrBase as the pointer base, and has returned in NewRHS the
861  // offset. Since Index is the offset of LHS to the base pointer, we will now
862  // compare the offsets instead of comparing the pointers.
863  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
864 }
865 
866 /// Fold comparisons between a GEP instruction and something else. At this point
867 /// we know that the GEP is on the LHS of the comparison.
868 Instruction *InstCombiner::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
869  ICmpInst::Predicate Cond,
870  Instruction &I) {
871  // Don't transform signed compares of GEPs into index compares. Even if the
872  // GEP is inbounds, the final add of the base pointer can have signed overflow
873  // and would change the result of the icmp.
874  // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
875  // the maximum signed value for the pointer type.
876  if (ICmpInst::isSigned(Cond))
877  return nullptr;
878 
879  // Look through bitcasts and addrspacecasts. We do not however want to remove
880  // 0 GEPs.
881  if (!isa<GetElementPtrInst>(RHS))
882  RHS = RHS->stripPointerCasts();
883 
884  Value *PtrBase = GEPLHS->getOperand(0);
885  if (PtrBase == RHS && GEPLHS->isInBounds()) {
886  // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
887  // This transformation (ignoring the base and scales) is valid because we
888  // know pointers can't overflow since the gep is inbounds. See if we can
889  // output an optimized form.
890  Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
891 
892  // If not, synthesize the offset the hard way.
893  if (!Offset)
894  Offset = EmitGEPOffset(GEPLHS);
895  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
896  Constant::getNullValue(Offset->getType()));
897  } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
898  // If the base pointers are different, but the indices are the same, just
899  // compare the base pointer.
900  if (PtrBase != GEPRHS->getOperand(0)) {
901  bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
902  IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
903  GEPRHS->getOperand(0)->getType();
904  if (IndicesTheSame)
905  for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
906  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
907  IndicesTheSame = false;
908  break;
909  }
910 
911  // If all indices are the same, just compare the base pointers.
912  if (IndicesTheSame)
913  return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
914 
915  // If we're comparing GEPs with two base pointers that only differ in type
916  // and both GEPs have only constant indices or just one use, then fold
917  // the compare with the adjusted indices.
918  if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
919  (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
920  (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
921  PtrBase->stripPointerCasts() ==
922  GEPRHS->getOperand(0)->stripPointerCasts()) {
923  Value *LOffset = EmitGEPOffset(GEPLHS);
924  Value *ROffset = EmitGEPOffset(GEPRHS);
925 
926  // If we looked through an addrspacecast between different sized address
927  // spaces, the LHS and RHS pointers are different sized
928  // integers. Truncate to the smaller one.
929  Type *LHSIndexTy = LOffset->getType();
930  Type *RHSIndexTy = ROffset->getType();
931  if (LHSIndexTy != RHSIndexTy) {
932  if (LHSIndexTy->getPrimitiveSizeInBits() <
933  RHSIndexTy->getPrimitiveSizeInBits()) {
934  ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
935  } else
936  LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
937  }
938 
939  Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
940  LOffset, ROffset);
941  return replaceInstUsesWith(I, Cmp);
942  }
943 
944  // Otherwise, the base pointers are different and the indices are
945  // different. Try convert this to an indexed compare by looking through
946  // PHIs/casts.
947  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
948  }
949 
950  // If one of the GEPs has all zero indices, recurse.
951  if (GEPLHS->hasAllZeroIndices())
952  return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
954 
955  // If the other GEP has all zero indices, recurse.
956  if (GEPRHS->hasAllZeroIndices())
957  return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
958 
959  bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
960  if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
961  // If the GEPs only differ by one index, compare it.
962  unsigned NumDifferences = 0; // Keep track of # differences.
963  unsigned DiffOperand = 0; // The operand that differs.
964  for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
965  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
966  if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
967  GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
968  // Irreconcilable differences.
969  NumDifferences = 2;
970  break;
971  } else {
972  if (NumDifferences++) break;
973  DiffOperand = i;
974  }
975  }
976 
977  if (NumDifferences == 0) // SAME GEP?
978  return replaceInstUsesWith(I, // No comparison is needed here.
979  Builder.getInt1(ICmpInst::isTrueWhenEqual(Cond)));
980 
981  else if (NumDifferences == 1 && GEPsInBounds) {
982  Value *LHSV = GEPLHS->getOperand(DiffOperand);
983  Value *RHSV = GEPRHS->getOperand(DiffOperand);
984  // Make sure we do a signed comparison here.
985  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
986  }
987  }
988 
989  // Only lower this if the icmp is the only user of the GEP or if we expect
990  // the result to fold to a constant!
991  if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
992  (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
993  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
994  Value *L = EmitGEPOffset(GEPLHS);
995  Value *R = EmitGEPOffset(GEPRHS);
996  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
997  }
998  }
999 
1000  // Try convert this to an indexed compare by looking through PHIs/casts as a
1001  // last resort.
1002  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1003 }
1004 
1005 Instruction *InstCombiner::foldAllocaCmp(ICmpInst &ICI,
1006  const AllocaInst *Alloca,
1007  const Value *Other) {
1008  assert(ICI.isEquality() && "Cannot fold non-equality comparison.");
1009 
1010  // It would be tempting to fold away comparisons between allocas and any
1011  // pointer not based on that alloca (e.g. an argument). However, even
1012  // though such pointers cannot alias, they can still compare equal.
1013  //
1014  // But LLVM doesn't specify where allocas get their memory, so if the alloca
1015  // doesn't escape we can argue that it's impossible to guess its value, and we
1016  // can therefore act as if any such guesses are wrong.
1017  //
1018  // The code below checks that the alloca doesn't escape, and that it's only
1019  // used in a comparison once (the current instruction). The
1020  // single-comparison-use condition ensures that we're trivially folding all
1021  // comparisons against the alloca consistently, and avoids the risk of
1022  // erroneously folding a comparison of the pointer with itself.
1023 
1024  unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1025 
1027  for (const Use &U : Alloca->uses()) {
1028  if (Worklist.size() >= MaxIter)
1029  return nullptr;
1030  Worklist.push_back(&U);
1031  }
1032 
1033  unsigned NumCmps = 0;
1034  while (!Worklist.empty()) {
1035  assert(Worklist.size() <= MaxIter);
1036  const Use *U = Worklist.pop_back_val();
1037  const Value *V = U->getUser();
1038  --MaxIter;
1039 
1040  if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1041  isa<SelectInst>(V)) {
1042  // Track the uses.
1043  } else if (isa<LoadInst>(V)) {
1044  // Loading from the pointer doesn't escape it.
1045  continue;
1046  } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1047  // Storing *to* the pointer is fine, but storing the pointer escapes it.
1048  if (SI->getValueOperand() == U->get())
1049  return nullptr;
1050  continue;
1051  } else if (isa<ICmpInst>(V)) {
1052  if (NumCmps++)
1053  return nullptr; // Found more than one cmp.
1054  continue;
1055  } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1056  switch (Intrin->getIntrinsicID()) {
1057  // These intrinsics don't escape or compare the pointer. Memset is safe
1058  // because we don't allow ptrtoint. Memcpy and memmove are safe because
1059  // we don't allow stores, so src cannot point to V.
1060  case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1061  case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1062  continue;
1063  default:
1064  return nullptr;
1065  }
1066  } else {
1067  return nullptr;
1068  }
1069  for (const Use &U : V->uses()) {
1070  if (Worklist.size() >= MaxIter)
1071  return nullptr;
1072  Worklist.push_back(&U);
1073  }
1074  }
1075 
1076  Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1077  return replaceInstUsesWith(
1078  ICI,
1080 }
1081 
1082 /// Fold "icmp pred (X+CI), X".
1083 Instruction *InstCombiner::foldICmpAddOpConst(Value *X, ConstantInt *CI,
1084  ICmpInst::Predicate Pred) {
1085  // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1086  // so the values can never be equal. Similarly for all other "or equals"
1087  // operators.
1088 
1089  // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1090  // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1091  // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1092  if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1093  Value *R =
1095  return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1096  }
1097 
1098  // (X+1) >u X --> X <u (0-1) --> X != 255
1099  // (X+2) >u X --> X <u (0-2) --> X <u 254
1100  // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1101  if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1102  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
1103 
1104  unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
1106  APInt::getSignedMaxValue(BitWidth));
1107 
1108  // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1109  // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1110  // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1111  // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1112  // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1113  // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1114  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1115  return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
1116 
1117  // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1118  // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1119  // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1120  // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1121  // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1122  // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1123 
1124  assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
1125  Constant *C = Builder.getInt(CI->getValue() - 1);
1126  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
1127 }
1128 
1129 /// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1130 /// (icmp eq/ne A, Log2(AP2/AP1)) ->
1131 /// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1132 Instruction *InstCombiner::foldICmpShrConstConst(ICmpInst &I, Value *A,
1133  const APInt &AP1,
1134  const APInt &AP2) {
1135  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1136 
1137  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1138  if (I.getPredicate() == I.ICMP_NE)
1139  Pred = CmpInst::getInversePredicate(Pred);
1140  return new ICmpInst(Pred, LHS, RHS);
1141  };
1142 
1143  // Don't bother doing any work for cases which InstSimplify handles.
1144  if (AP2.isNullValue())
1145  return nullptr;
1146 
1147  bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1148  if (IsAShr) {
1149  if (AP2.isAllOnesValue())
1150  return nullptr;
1151  if (AP2.isNegative() != AP1.isNegative())
1152  return nullptr;
1153  if (AP2.sgt(AP1))
1154  return nullptr;
1155  }
1156 
1157  if (!AP1)
1158  // 'A' must be large enough to shift out the highest set bit.
1159  return getICmp(I.ICMP_UGT, A,
1160  ConstantInt::get(A->getType(), AP2.logBase2()));
1161 
1162  if (AP1 == AP2)
1163  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1164 
1165  int Shift;
1166  if (IsAShr && AP1.isNegative())
1167  Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1168  else
1169  Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1170 
1171  if (Shift > 0) {
1172  if (IsAShr && AP1 == AP2.ashr(Shift)) {
1173  // There are multiple solutions if we are comparing against -1 and the LHS
1174  // of the ashr is not a power of two.
1175  if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1176  return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1177  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1178  } else if (AP1 == AP2.lshr(Shift)) {
1179  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1180  }
1181  }
1182 
1183  // Shifting const2 will never be equal to const1.
1184  // FIXME: This should always be handled by InstSimplify?
1185  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1186  return replaceInstUsesWith(I, TorF);
1187 }
1188 
1189 /// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1190 /// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1191 Instruction *InstCombiner::foldICmpShlConstConst(ICmpInst &I, Value *A,
1192  const APInt &AP1,
1193  const APInt &AP2) {
1194  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1195 
1196  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1197  if (I.getPredicate() == I.ICMP_NE)
1198  Pred = CmpInst::getInversePredicate(Pred);
1199  return new ICmpInst(Pred, LHS, RHS);
1200  };
1201 
1202  // Don't bother doing any work for cases which InstSimplify handles.
1203  if (AP2.isNullValue())
1204  return nullptr;
1205 
1206  unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1207 
1208  if (!AP1 && AP2TrailingZeros != 0)
1209  return getICmp(
1210  I.ICMP_UGE, A,
1211  ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1212 
1213  if (AP1 == AP2)
1214  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1215 
1216  // Get the distance between the lowest bits that are set.
1217  int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1218 
1219  if (Shift > 0 && AP2.shl(Shift) == AP1)
1220  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1221 
1222  // Shifting const2 will never be equal to const1.
1223  // FIXME: This should always be handled by InstSimplify?
1224  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1225  return replaceInstUsesWith(I, TorF);
1226 }
1227 
1228 /// The caller has matched a pattern of the form:
1229 /// I = icmp ugt (add (add A, B), CI2), CI1
1230 /// If this is of the form:
1231 /// sum = a + b
1232 /// if (sum+128 >u 255)
1233 /// Then replace it with llvm.sadd.with.overflow.i8.
1234 ///
1236  ConstantInt *CI2, ConstantInt *CI1,
1237  InstCombiner &IC) {
1238  // The transformation we're trying to do here is to transform this into an
1239  // llvm.sadd.with.overflow. To do this, we have to replace the original add
1240  // with a narrower add, and discard the add-with-constant that is part of the
1241  // range check (if we can't eliminate it, this isn't profitable).
1242 
1243  // In order to eliminate the add-with-constant, the compare can be its only
1244  // use.
1245  Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1246  if (!AddWithCst->hasOneUse())
1247  return nullptr;
1248 
1249  // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1250  if (!CI2->getValue().isPowerOf2())
1251  return nullptr;
1252  unsigned NewWidth = CI2->getValue().countTrailingZeros();
1253  if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1254  return nullptr;
1255 
1256  // The width of the new add formed is 1 more than the bias.
1257  ++NewWidth;
1258 
1259  // Check to see that CI1 is an all-ones value with NewWidth bits.
1260  if (CI1->getBitWidth() == NewWidth ||
1261  CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1262  return nullptr;
1263 
1264  // This is only really a signed overflow check if the inputs have been
1265  // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1266  // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1267  unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1268  if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1269  IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1270  return nullptr;
1271 
1272  // In order to replace the original add with a narrower
1273  // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1274  // and truncates that discard the high bits of the add. Verify that this is
1275  // the case.
1276  Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1277  for (User *U : OrigAdd->users()) {
1278  if (U == AddWithCst)
1279  continue;
1280 
1281  // Only accept truncates for now. We would really like a nice recursive
1282  // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1283  // chain to see which bits of a value are actually demanded. If the
1284  // original add had another add which was then immediately truncated, we
1285  // could still do the transformation.
1286  TruncInst *TI = dyn_cast<TruncInst>(U);
1287  if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1288  return nullptr;
1289  }
1290 
1291  // If the pattern matches, truncate the inputs to the narrower type and
1292  // use the sadd_with_overflow intrinsic to efficiently compute both the
1293  // result and the overflow bit.
1294  Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1296  Intrinsic::sadd_with_overflow, NewType);
1297 
1298  InstCombiner::BuilderTy &Builder = IC.Builder;
1299 
1300  // Put the new code above the original add, in case there are any uses of the
1301  // add between the add and the compare.
1302  Builder.SetInsertPoint(OrigAdd);
1303 
1304  Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
1305  Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
1306  CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
1307  Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
1308  Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
1309 
1310  // The inner add was the result of the narrow add, zero extended to the
1311  // wider type. Replace it with the result computed by the intrinsic.
1312  IC.replaceInstUsesWith(*OrigAdd, ZExt);
1313 
1314  // The original icmp gets replaced with the overflow value.
1315  return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1316 }
1317 
1318 // Handle (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1319 Instruction *InstCombiner::foldICmpWithZero(ICmpInst &Cmp) {
1320  CmpInst::Predicate Pred = Cmp.getPredicate();
1321  Value *X = Cmp.getOperand(0);
1322 
1323  if (match(Cmp.getOperand(1), m_Zero()) && Pred == ICmpInst::ICMP_SGT) {
1324  Value *A, *B;
1325  SelectPatternResult SPR = matchSelectPattern(X, A, B);
1326  if (SPR.Flavor == SPF_SMIN) {
1327  if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
1328  return new ICmpInst(Pred, B, Cmp.getOperand(1));
1329  if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
1330  return new ICmpInst(Pred, A, Cmp.getOperand(1));
1331  }
1332  }
1333  return nullptr;
1334 }
1335 
1336 // Fold icmp Pred X, C.
1337 Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
1338  CmpInst::Predicate Pred = Cmp.getPredicate();
1339  Value *X = Cmp.getOperand(0);
1340 
1341  const APInt *C;
1342  if (!match(Cmp.getOperand(1), m_APInt(C)))
1343  return nullptr;
1344 
1345  Value *A = nullptr, *B = nullptr;
1346 
1347  // Match the following pattern, which is a common idiom when writing
1348  // overflow-safe integer arithmetic functions. The source performs an addition
1349  // in wider type and explicitly checks for overflow using comparisons against
1350  // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1351  //
1352  // TODO: This could probably be generalized to handle other overflow-safe
1353  // operations if we worked out the formulas to compute the appropriate magic
1354  // constants.
1355  //
1356  // sum = a + b
1357  // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1358  {
1359  ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1360  if (Pred == ICmpInst::ICMP_UGT &&
1361  match(X, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1363  Cmp, A, B, CI2, cast<ConstantInt>(Cmp.getOperand(1)), *this))
1364  return Res;
1365  }
1366 
1367  // FIXME: Use m_APInt to allow folds for splat constants.
1368  ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
1369  if (!CI)
1370  return nullptr;
1371 
1372  // Canonicalize icmp instructions based on dominating conditions.
1373  BasicBlock *Parent = Cmp.getParent();
1374  BasicBlock *Dom = Parent->getSinglePredecessor();
1375  auto *BI = Dom ? dyn_cast<BranchInst>(Dom->getTerminator()) : nullptr;
1376  ICmpInst::Predicate Pred2;
1377  BasicBlock *TrueBB, *FalseBB;
1378  ConstantInt *CI2;
1379  if (BI && match(BI, m_Br(m_ICmp(Pred2, m_Specific(X), m_ConstantInt(CI2)),
1380  TrueBB, FalseBB)) &&
1381  TrueBB != FalseBB) {
1382  ConstantRange CR =
1384  ConstantRange DominatingCR =
1385  (Parent == TrueBB)
1388  CmpInst::getInversePredicate(Pred2), CI2->getValue());
1389  ConstantRange Intersection = DominatingCR.intersectWith(CR);
1390  ConstantRange Difference = DominatingCR.difference(CR);
1391  if (Intersection.isEmptySet())
1392  return replaceInstUsesWith(Cmp, Builder.getFalse());
1393  if (Difference.isEmptySet())
1394  return replaceInstUsesWith(Cmp, Builder.getTrue());
1395 
1396  // If this is a normal comparison, it demands all bits. If it is a sign
1397  // bit comparison, it only demands the sign bit.
1398  bool UnusedBit;
1399  bool IsSignBit = isSignBitCheck(Pred, CI->getValue(), UnusedBit);
1400 
1401  // Canonicalizing a sign bit comparison that gets used in a branch,
1402  // pessimizes codegen by generating branch on zero instruction instead
1403  // of a test and branch. So we avoid canonicalizing in such situations
1404  // because test and branch instruction has better branch displacement
1405  // than compare and branch instruction.
1406  if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
1407  return nullptr;
1408 
1409  if (auto *AI = Intersection.getSingleElement())
1410  return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*AI));
1411  if (auto *AD = Difference.getSingleElement())
1412  return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*AD));
1413  }
1414 
1415  return nullptr;
1416 }
1417 
1418 /// Fold icmp (trunc X, Y), C.
1419 Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
1420  TruncInst *Trunc,
1421  const APInt &C) {
1422  ICmpInst::Predicate Pred = Cmp.getPredicate();
1423  Value *X = Trunc->getOperand(0);
1424  if (C.isOneValue() && C.getBitWidth() > 1) {
1425  // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1426  Value *V = nullptr;
1427  if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1428  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1429  ConstantInt::get(V->getType(), 1));
1430  }
1431 
1432  if (Cmp.isEquality() && Trunc->hasOneUse()) {
1433  // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1434  // of the high bits truncated out of x are known.
1435  unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1436  SrcBits = X->getType()->getScalarSizeInBits();
1437  KnownBits Known = computeKnownBits(X, 0, &Cmp);
1438 
1439  // If all the high bits are known, we can do this xform.
1440  if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1441  // Pull in the high bits from known-ones set.
1442  APInt NewRHS = C.zext(SrcBits);
1443  NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1444  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1445  }
1446  }
1447 
1448  return nullptr;
1449 }
1450 
1451 /// Fold icmp (xor X, Y), C.
1452 Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp,
1453  BinaryOperator *Xor,
1454  const APInt &C) {
1455  Value *X = Xor->getOperand(0);
1456  Value *Y = Xor->getOperand(1);
1457  const APInt *XorC;
1458  if (!match(Y, m_APInt(XorC)))
1459  return nullptr;
1460 
1461  // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1462  // fold the xor.
1463  ICmpInst::Predicate Pred = Cmp.getPredicate();
1464  bool TrueIfSigned = false;
1465  if (isSignBitCheck(Cmp.getPredicate(), C, TrueIfSigned)) {
1466 
1467  // If the sign bit of the XorCst is not set, there is no change to
1468  // the operation, just stop using the Xor.
1469  if (!XorC->isNegative()) {
1470  Cmp.setOperand(0, X);
1471  Worklist.Add(Xor);
1472  return &Cmp;
1473  }
1474 
1475  // Emit the opposite comparison.
1476  if (TrueIfSigned)
1477  return new ICmpInst(ICmpInst::ICMP_SGT, X,
1479  else
1480  return new ICmpInst(ICmpInst::ICMP_SLT, X,
1482  }
1483 
1484  if (Xor->hasOneUse()) {
1485  // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1486  if (!Cmp.isEquality() && XorC->isSignMask()) {
1487  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1488  : Cmp.getSignedPredicate();
1489  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1490  }
1491 
1492  // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1493  if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1494  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1495  : Cmp.getSignedPredicate();
1496  Pred = Cmp.getSwappedPredicate(Pred);
1497  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1498  }
1499  }
1500 
1501  // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1502  // iff -C is a power of 2
1503  if (Pred == ICmpInst::ICMP_UGT && *XorC == ~C && (C + 1).isPowerOf2())
1504  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1505 
1506  // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1507  // iff -C is a power of 2
1508  if (Pred == ICmpInst::ICMP_ULT && *XorC == -C && C.isPowerOf2())
1509  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
1510 
1511  return nullptr;
1512 }
1513 
1514 /// Fold icmp (and (sh X, Y), C2), C1.
1515 Instruction *InstCombiner::foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
1516  const APInt &C1, const APInt &C2) {
1517  BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1518  if (!Shift || !Shift->isShift())
1519  return nullptr;
1520 
1521  // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1522  // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1523  // code produced by the clang front-end, for bitfield access.
1524  // This seemingly simple opportunity to fold away a shift turns out to be
1525  // rather complicated. See PR17827 for details.
1526  unsigned ShiftOpcode = Shift->getOpcode();
1527  bool IsShl = ShiftOpcode == Instruction::Shl;
1528  const APInt *C3;
1529  if (match(Shift->getOperand(1), m_APInt(C3))) {
1530  bool CanFold = false;
1531  if (ShiftOpcode == Instruction::Shl) {
1532  // For a left shift, we can fold if the comparison is not signed. We can
1533  // also fold a signed comparison if the mask value and comparison value
1534  // are not negative. These constraints may not be obvious, but we can
1535  // prove that they are correct using an SMT solver.
1536  if (!Cmp.isSigned() || (!C2.isNegative() && !C1.isNegative()))
1537  CanFold = true;
1538  } else {
1539  bool IsAshr = ShiftOpcode == Instruction::AShr;
1540  // For a logical right shift, we can fold if the comparison is not signed.
1541  // We can also fold a signed comparison if the shifted mask value and the
1542  // shifted comparison value are not negative. These constraints may not be
1543  // obvious, but we can prove that they are correct using an SMT solver.
1544  // For an arithmetic shift right we can do the same, if we ensure
1545  // the And doesn't use any bits being shifted in. Normally these would
1546  // be turned into lshr by SimplifyDemandedBits, but not if there is an
1547  // additional user.
1548  if (!IsAshr || (C2.shl(*C3).lshr(*C3) == C2)) {
1549  if (!Cmp.isSigned() ||
1550  (!C2.shl(*C3).isNegative() && !C1.shl(*C3).isNegative()))
1551  CanFold = true;
1552  }
1553  }
1554 
1555  if (CanFold) {
1556  APInt NewCst = IsShl ? C1.lshr(*C3) : C1.shl(*C3);
1557  APInt SameAsC1 = IsShl ? NewCst.shl(*C3) : NewCst.lshr(*C3);
1558  // Check to see if we are shifting out any of the bits being compared.
1559  if (SameAsC1 != C1) {
1560  // If we shifted bits out, the fold is not going to work out. As a
1561  // special case, check to see if this means that the result is always
1562  // true or false now.
1563  if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1564  return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1565  if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1566  return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1567  } else {
1568  Cmp.setOperand(1, ConstantInt::get(And->getType(), NewCst));
1569  APInt NewAndCst = IsShl ? C2.lshr(*C3) : C2.shl(*C3);
1570  And->setOperand(1, ConstantInt::get(And->getType(), NewAndCst));
1571  And->setOperand(0, Shift->getOperand(0));
1572  Worklist.Add(Shift); // Shift is dead.
1573  return &Cmp;
1574  }
1575  }
1576  }
1577 
1578  // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1579  // preferable because it allows the C2 << Y expression to be hoisted out of a
1580  // loop if Y is invariant and X is not.
1581  if (Shift->hasOneUse() && C1.isNullValue() && Cmp.isEquality() &&
1582  !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1583  // Compute C2 << Y.
1584  Value *NewShift =
1585  IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
1586  : Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
1587 
1588  // Compute X & (C2 << Y).
1589  Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
1590  Cmp.setOperand(0, NewAnd);
1591  return &Cmp;
1592  }
1593 
1594  return nullptr;
1595 }
1596 
1597 /// Fold icmp (and X, C2), C1.
1598 Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
1599  BinaryOperator *And,
1600  const APInt &C1) {
1601  const APInt *C2;
1602  if (!match(And->getOperand(1), m_APInt(C2)))
1603  return nullptr;
1604 
1605  if (!And->hasOneUse())
1606  return nullptr;
1607 
1608  // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1609  // the input width without changing the value produced, eliminate the cast:
1610  //
1611  // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1612  //
1613  // We can do this transformation if the constants do not have their sign bits
1614  // set or if it is an equality comparison. Extending a relational comparison
1615  // when we're checking the sign bit would not work.
1616  Value *W;
1617  if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
1618  (Cmp.isEquality() || (!C1.isNegative() && !C2->isNegative()))) {
1619  // TODO: Is this a good transform for vectors? Wider types may reduce
1620  // throughput. Should this transform be limited (even for scalars) by using
1621  // shouldChangeType()?
1622  if (!Cmp.getType()->isVectorTy()) {
1623  Type *WideType = W->getType();
1624  unsigned WideScalarBits = WideType->getScalarSizeInBits();
1625  Constant *ZextC1 = ConstantInt::get(WideType, C1.zext(WideScalarBits));
1626  Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1627  Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
1628  return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1629  }
1630  }
1631 
1632  if (Instruction *I = foldICmpAndShift(Cmp, And, C1, *C2))
1633  return I;
1634 
1635  // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1636  // (icmp pred (and A, (or (shl 1, B), 1), 0))
1637  //
1638  // iff pred isn't signed
1639  if (!Cmp.isSigned() && C1.isNullValue() && And->getOperand(0)->hasOneUse() &&
1640  match(And->getOperand(1), m_One())) {
1641  Constant *One = cast<Constant>(And->getOperand(1));
1642  Value *Or = And->getOperand(0);
1643  Value *A, *B, *LShr;
1644  if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1645  match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1646  unsigned UsesRemoved = 0;
1647  if (And->hasOneUse())
1648  ++UsesRemoved;
1649  if (Or->hasOneUse())
1650  ++UsesRemoved;
1651  if (LShr->hasOneUse())
1652  ++UsesRemoved;
1653 
1654  // Compute A & ((1 << B) | 1)
1655  Value *NewOr = nullptr;
1656  if (auto *C = dyn_cast<Constant>(B)) {
1657  if (UsesRemoved >= 1)
1658  NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1659  } else {
1660  if (UsesRemoved >= 3)
1661  NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
1662  /*HasNUW=*/true),
1663  One, Or->getName());
1664  }
1665  if (NewOr) {
1666  Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
1667  Cmp.setOperand(0, NewAnd);
1668  return &Cmp;
1669  }
1670  }
1671  }
1672 
1673  return nullptr;
1674 }
1675 
1676 /// Fold icmp (and X, Y), C.
1677 Instruction *InstCombiner::foldICmpAndConstant(ICmpInst &Cmp,
1678  BinaryOperator *And,
1679  const APInt &C) {
1680  if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1681  return I;
1682 
1683  // TODO: These all require that Y is constant too, so refactor with the above.
1684 
1685  // Try to optimize things like "A[i] & 42 == 0" to index computations.
1686  Value *X = And->getOperand(0);
1687  Value *Y = And->getOperand(1);
1688  if (auto *LI = dyn_cast<LoadInst>(X))
1689  if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1690  if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1691  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1692  !LI->isVolatile() && isa<ConstantInt>(Y)) {
1693  ConstantInt *C2 = cast<ConstantInt>(Y);
1694  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1695  return Res;
1696  }
1697 
1698  if (!Cmp.isEquality())
1699  return nullptr;
1700 
1701  // X & -C == -C -> X > u ~C
1702  // X & -C != -C -> X <= u ~C
1703  // iff C is a power of 2
1704  if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
1705  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
1707  return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1708  }
1709 
1710  // (X & C2) == 0 -> (trunc X) >= 0
1711  // (X & C2) != 0 -> (trunc X) < 0
1712  // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1713  const APInt *C2;
1714  if (And->hasOneUse() && C.isNullValue() && match(Y, m_APInt(C2))) {
1715  int32_t ExactLogBase2 = C2->exactLogBase2();
1716  if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1717  Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1718  if (And->getType()->isVectorTy())
1719  NTy = VectorType::get(NTy, And->getType()->getVectorNumElements());
1720  Value *Trunc = Builder.CreateTrunc(X, NTy);
1721  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
1723  return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1724  }
1725  }
1726 
1727  return nullptr;
1728 }
1729 
1730 /// Fold icmp (or X, Y), C.
1731 Instruction *InstCombiner::foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
1732  const APInt &C) {
1733  ICmpInst::Predicate Pred = Cmp.getPredicate();
1734  if (C.isOneValue()) {
1735  // icmp slt signum(V) 1 --> icmp slt V, 1
1736  Value *V = nullptr;
1737  if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1738  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1739  ConstantInt::get(V->getType(), 1));
1740  }
1741 
1742  // X | C == C --> X <=u C
1743  // X | C != C --> X >u C
1744  // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1745  if (Cmp.isEquality() && Cmp.getOperand(1) == Or->getOperand(1) &&
1746  (C + 1).isPowerOf2()) {
1748  return new ICmpInst(Pred, Or->getOperand(0), Or->getOperand(1));
1749  }
1750 
1751  if (!Cmp.isEquality() || !C.isNullValue() || !Or->hasOneUse())
1752  return nullptr;
1753 
1754  Value *P, *Q;
1755  if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1756  // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1757  // -> and (icmp eq P, null), (icmp eq Q, null).
1758  Value *CmpP =
1759  Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1760  Value *CmpQ =
1761  Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1762  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1763  return BinaryOperator::Create(BOpc, CmpP, CmpQ);
1764  }
1765 
1766  // Are we using xors to bitwise check for a pair of (in)equalities? Convert to
1767  // a shorter form that has more potential to be folded even further.
1768  Value *X1, *X2, *X3, *X4;
1769  if (match(Or->getOperand(0), m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
1770  match(Or->getOperand(1), m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
1771  // ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
1772  // ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
1773  Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
1774  Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
1775  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1776  return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
1777  }
1778 
1779  return nullptr;
1780 }
1781 
1782 /// Fold icmp (mul X, Y), C.
1783 Instruction *InstCombiner::foldICmpMulConstant(ICmpInst &Cmp,
1784  BinaryOperator *Mul,
1785  const APInt &C) {
1786  const APInt *MulC;
1787  if (!match(Mul->getOperand(1), m_APInt(MulC)))
1788  return nullptr;
1789 
1790  // If this is a test of the sign bit and the multiply is sign-preserving with
1791  // a constant operand, use the multiply LHS operand instead.
1792  ICmpInst::Predicate Pred = Cmp.getPredicate();
1793  if (isSignTest(Pred, C) && Mul->hasNoSignedWrap()) {
1794  if (MulC->isNegative())
1795  Pred = ICmpInst::getSwappedPredicate(Pred);
1796  return new ICmpInst(Pred, Mul->getOperand(0),
1798  }
1799 
1800  return nullptr;
1801 }
1802 
1803 /// Fold icmp (shl 1, Y), C.
1805  const APInt &C) {
1806  Value *Y;
1807  if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
1808  return nullptr;
1809 
1810  Type *ShiftType = Shl->getType();
1811  unsigned TypeBits = C.getBitWidth();
1812  bool CIsPowerOf2 = C.isPowerOf2();
1813  ICmpInst::Predicate Pred = Cmp.getPredicate();
1814  if (Cmp.isUnsigned()) {
1815  // (1 << Y) pred C -> Y pred Log2(C)
1816  if (!CIsPowerOf2) {
1817  // (1 << Y) < 30 -> Y <= 4
1818  // (1 << Y) <= 30 -> Y <= 4
1819  // (1 << Y) >= 30 -> Y > 4
1820  // (1 << Y) > 30 -> Y > 4
1821  if (Pred == ICmpInst::ICMP_ULT)
1822  Pred = ICmpInst::ICMP_ULE;
1823  else if (Pred == ICmpInst::ICMP_UGE)
1824  Pred = ICmpInst::ICMP_UGT;
1825  }
1826 
1827  // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
1828  // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
1829  unsigned CLog2 = C.logBase2();
1830  if (CLog2 == TypeBits - 1) {
1831  if (Pred == ICmpInst::ICMP_UGE)
1832  Pred = ICmpInst::ICMP_EQ;
1833  else if (Pred == ICmpInst::ICMP_ULT)
1834  Pred = ICmpInst::ICMP_NE;
1835  }
1836  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
1837  } else if (Cmp.isSigned()) {
1838  Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
1839  if (C.isAllOnesValue()) {
1840  // (1 << Y) <= -1 -> Y == 31
1841  if (Pred == ICmpInst::ICMP_SLE)
1842  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1843 
1844  // (1 << Y) > -1 -> Y != 31
1845  if (Pred == ICmpInst::ICMP_SGT)
1846  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1847  } else if (!C) {
1848  // (1 << Y) < 0 -> Y == 31
1849  // (1 << Y) <= 0 -> Y == 31
1850  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1851  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1852 
1853  // (1 << Y) >= 0 -> Y != 31
1854  // (1 << Y) > 0 -> Y != 31
1855  if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1856  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1857  }
1858  } else if (Cmp.isEquality() && CIsPowerOf2) {
1859  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C.logBase2()));
1860  }
1861 
1862  return nullptr;
1863 }
1864 
1865 /// Fold icmp (shl X, Y), C.
1866 Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp,
1867  BinaryOperator *Shl,
1868  const APInt &C) {
1869  const APInt *ShiftVal;
1870  if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
1871  return foldICmpShlConstConst(Cmp, Shl->getOperand(1), C, *ShiftVal);
1872 
1873  const APInt *ShiftAmt;
1874  if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
1875  return foldICmpShlOne(Cmp, Shl, C);
1876 
1877  // Check that the shift amount is in range. If not, don't perform undefined
1878  // shifts. When the shift is visited, it will be simplified.
1879  unsigned TypeBits = C.getBitWidth();
1880  if (ShiftAmt->uge(TypeBits))
1881  return nullptr;
1882 
1883  ICmpInst::Predicate Pred = Cmp.getPredicate();
1884  Value *X = Shl->getOperand(0);
1885  Type *ShType = Shl->getType();
1886 
1887  // NSW guarantees that we are only shifting out sign bits from the high bits,
1888  // so we can ASHR the compare constant without needing a mask and eliminate
1889  // the shift.
1890  if (Shl->hasNoSignedWrap()) {
1891  if (Pred == ICmpInst::ICMP_SGT) {
1892  // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
1893  APInt ShiftedC = C.ashr(*ShiftAmt);
1894  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1895  }
1896  if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
1897  C.ashr(*ShiftAmt).shl(*ShiftAmt) == C) {
1898  APInt ShiftedC = C.ashr(*ShiftAmt);
1899  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1900  }
1901  if (Pred == ICmpInst::ICMP_SLT) {
1902  // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
1903  // (X << S) <=s C is equiv to X <=s (C >> S) for all C
1904  // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
1905  // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
1906  assert(!C.isMinSignedValue() && "Unexpected icmp slt");
1907  APInt ShiftedC = (C - 1).ashr(*ShiftAmt) + 1;
1908  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1909  }
1910  // If this is a signed comparison to 0 and the shift is sign preserving,
1911  // use the shift LHS operand instead; isSignTest may change 'Pred', so only
1912  // do that if we're sure to not continue on in this function.
1913  if (isSignTest(Pred, C))
1914  return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
1915  }
1916 
1917  // NUW guarantees that we are only shifting out zero bits from the high bits,
1918  // so we can LSHR the compare constant without needing a mask and eliminate
1919  // the shift.
1920  if (Shl->hasNoUnsignedWrap()) {
1921  if (Pred == ICmpInst::ICMP_UGT) {
1922  // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
1923  APInt ShiftedC = C.lshr(*ShiftAmt);
1924  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1925  }
1926  if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) &&
1927  C.lshr(*ShiftAmt).shl(*ShiftAmt) == C) {
1928  APInt ShiftedC = C.lshr(*ShiftAmt);
1929  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1930  }
1931  if (Pred == ICmpInst::ICMP_ULT) {
1932  // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
1933  // (X << S) <=u C is equiv to X <=u (C >> S) for all C
1934  // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
1935  // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
1936  assert(C.ugt(0) && "ult 0 should have been eliminated");
1937  APInt ShiftedC = (C - 1).lshr(*ShiftAmt) + 1;
1938  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1939  }
1940  }
1941 
1942  if (Cmp.isEquality() && Shl->hasOneUse()) {
1943  // Strength-reduce the shift into an 'and'.
1945  ShType,
1946  APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
1947  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1948  Constant *LShrC = ConstantInt::get(ShType, C.lshr(*ShiftAmt));
1949  return new ICmpInst(Pred, And, LShrC);
1950  }
1951 
1952  // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
1953  bool TrueIfSigned = false;
1954  if (Shl->hasOneUse() && isSignBitCheck(Pred, C, TrueIfSigned)) {
1955  // (X << 31) <s 0 --> (X & 1) != 0
1957  ShType,
1958  APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
1959  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1960  return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
1961  And, Constant::getNullValue(ShType));
1962  }
1963 
1964  // Transform (icmp pred iM (shl iM %v, N), C)
1965  // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
1966  // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
1967  // This enables us to get rid of the shift in favor of a trunc that may be
1968  // free on the target. It has the additional benefit of comparing to a
1969  // smaller constant that may be more target-friendly.
1970  unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
1971  if (Shl->hasOneUse() && Amt != 0 && C.countTrailingZeros() >= Amt &&
1972  DL.isLegalInteger(TypeBits - Amt)) {
1973  Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
1974  if (ShType->isVectorTy())
1975  TruncTy = VectorType::get(TruncTy, ShType->getVectorNumElements());
1976  Constant *NewC =
1977  ConstantInt::get(TruncTy, C.ashr(*ShiftAmt).trunc(TypeBits - Amt));
1978  return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
1979  }
1980 
1981  return nullptr;
1982 }
1983 
1984 /// Fold icmp ({al}shr X, Y), C.
1985 Instruction *InstCombiner::foldICmpShrConstant(ICmpInst &Cmp,
1986  BinaryOperator *Shr,
1987  const APInt &C) {
1988  // An exact shr only shifts out zero bits, so:
1989  // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
1990  Value *X = Shr->getOperand(0);
1991  CmpInst::Predicate Pred = Cmp.getPredicate();
1992  if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
1993  C.isNullValue())
1994  return new ICmpInst(Pred, X, Cmp.getOperand(1));
1995 
1996  const APInt *ShiftVal;
1997  if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
1998  return foldICmpShrConstConst(Cmp, Shr->getOperand(1), C, *ShiftVal);
1999 
2000  const APInt *ShiftAmt;
2001  if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2002  return nullptr;
2003 
2004  // Check that the shift amount is in range. If not, don't perform undefined
2005  // shifts. When the shift is visited it will be simplified.
2006  unsigned TypeBits = C.getBitWidth();
2007  unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2008  if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2009  return nullptr;
2010 
2011  bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2012  bool IsExact = Shr->isExact();
2013  Type *ShrTy = Shr->getType();
2014  // TODO: If we could guarantee that InstSimplify would handle all of the
2015  // constant-value-based preconditions in the folds below, then we could assert
2016  // those conditions rather than checking them. This is difficult because of
2017  // undef/poison (PR34838).
2018  if (IsAShr) {
2019  if (Pred == CmpInst::ICMP_SLT || (Pred == CmpInst::ICMP_SGT && IsExact)) {
2020  // icmp slt (ashr X, ShAmtC), C --> icmp slt X, (C << ShAmtC)
2021  // icmp sgt (ashr exact X, ShAmtC), C --> icmp sgt X, (C << ShAmtC)
2022  APInt ShiftedC = C.shl(ShAmtVal);
2023  if (ShiftedC.ashr(ShAmtVal) == C)
2024  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2025  }
2026  if (Pred == CmpInst::ICMP_SGT) {
2027  // icmp sgt (ashr X, ShAmtC), C --> icmp sgt X, ((C + 1) << ShAmtC) - 1
2028  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2029  if (!C.isMaxSignedValue() && !(C + 1).shl(ShAmtVal).isMinSignedValue() &&
2030  (ShiftedC + 1).ashr(ShAmtVal) == (C + 1))
2031  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2032  }
2033  } else {
2034  if (Pred == CmpInst::ICMP_ULT || (Pred == CmpInst::ICMP_UGT && IsExact)) {
2035  // icmp ult (lshr X, ShAmtC), C --> icmp ult X, (C << ShAmtC)
2036  // icmp ugt (lshr exact X, ShAmtC), C --> icmp ugt X, (C << ShAmtC)
2037  APInt ShiftedC = C.shl(ShAmtVal);
2038  if (ShiftedC.lshr(ShAmtVal) == C)
2039  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2040  }
2041  if (Pred == CmpInst::ICMP_UGT) {
2042  // icmp ugt (lshr X, ShAmtC), C --> icmp ugt X, ((C + 1) << ShAmtC) - 1
2043  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2044  if ((ShiftedC + 1).lshr(ShAmtVal) == (C + 1))
2045  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2046  }
2047  }
2048 
2049  if (!Cmp.isEquality())
2050  return nullptr;
2051 
2052  // Handle equality comparisons of shift-by-constant.
2053 
2054  // If the comparison constant changes with the shift, the comparison cannot
2055  // succeed (bits of the comparison constant cannot match the shifted value).
2056  // This should be known by InstSimplify and already be folded to true/false.
2057  assert(((IsAShr && C.shl(ShAmtVal).ashr(ShAmtVal) == C) ||
2058  (!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&
2059  "Expected icmp+shr simplify did not occur.");
2060 
2061  // If the bits shifted out are known zero, compare the unshifted value:
2062  // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2063  if (Shr->isExact())
2064  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, C << ShAmtVal));
2065 
2066  if (Shr->hasOneUse()) {
2067  // Canonicalize the shift into an 'and':
2068  // icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
2069  APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2070  Constant *Mask = ConstantInt::get(ShrTy, Val);
2071  Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
2072  return new ICmpInst(Pred, And, ConstantInt::get(ShrTy, C << ShAmtVal));
2073  }
2074 
2075  return nullptr;
2076 }
2077 
2078 /// Fold icmp (udiv X, Y), C.
2079 Instruction *InstCombiner::foldICmpUDivConstant(ICmpInst &Cmp,
2080  BinaryOperator *UDiv,
2081  const APInt &C) {
2082  const APInt *C2;
2083  if (!match(UDiv->getOperand(0), m_APInt(C2)))
2084  return nullptr;
2085 
2086  assert(*C2 != 0 && "udiv 0, X should have been simplified already.");
2087 
2088  // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2089  Value *Y = UDiv->getOperand(1);
2090  if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2091  assert(!C.isMaxValue() &&
2092  "icmp ugt X, UINT_MAX should have been simplified already.");
2093  return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2094  ConstantInt::get(Y->getType(), C2->udiv(C + 1)));
2095  }
2096 
2097  // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2098  if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2099  assert(C != 0 && "icmp ult X, 0 should have been simplified already.");
2100  return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2101  ConstantInt::get(Y->getType(), C2->udiv(C)));
2102  }
2103 
2104  return nullptr;
2105 }
2106 
2107 /// Fold icmp ({su}div X, Y), C.
2108 Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
2109  BinaryOperator *Div,
2110  const APInt &C) {
2111  // Fold: icmp pred ([us]div X, C2), C -> range test
2112  // Fold this div into the comparison, producing a range check.
2113  // Determine, based on the divide type, what the range is being
2114  // checked. If there is an overflow on the low or high side, remember
2115  // it, otherwise compute the range [low, hi) bounding the new value.
2116  // See: InsertRangeTest above for the kinds of replacements possible.
2117  const APInt *C2;
2118  if (!match(Div->getOperand(1), m_APInt(C2)))
2119  return nullptr;
2120 
2121  // FIXME: If the operand types don't match the type of the divide
2122  // then don't attempt this transform. The code below doesn't have the
2123  // logic to deal with a signed divide and an unsigned compare (and
2124  // vice versa). This is because (x /s C2) <s C produces different
2125  // results than (x /s C2) <u C or (x /u C2) <s C or even
2126  // (x /u C2) <u C. Simply casting the operands and result won't
2127  // work. :( The if statement below tests that condition and bails
2128  // if it finds it.
2129  bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2130  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2131  return nullptr;
2132 
2133  // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2134  // INT_MIN will also fail if the divisor is 1. Although folds of all these
2135  // division-by-constant cases should be present, we can not assert that they
2136  // have happened before we reach this icmp instruction.
2137  if (C2->isNullValue() || C2->isOneValue() ||
2138  (DivIsSigned && C2->isAllOnesValue()))
2139  return nullptr;
2140 
2141  // Compute Prod = C * C2. We are essentially solving an equation of
2142  // form X / C2 = C. We solve for X by multiplying C2 and C.
2143  // By solving for X, we can turn this into a range check instead of computing
2144  // a divide.
2145  APInt Prod = C * *C2;
2146 
2147  // Determine if the product overflows by seeing if the product is not equal to
2148  // the divide. Make sure we do the same kind of divide as in the LHS
2149  // instruction that we're folding.
2150  bool ProdOV = (DivIsSigned ? Prod.sdiv(*C2) : Prod.udiv(*C2)) != C;
2151 
2152  ICmpInst::Predicate Pred = Cmp.getPredicate();
2153 
2154  // If the division is known to be exact, then there is no remainder from the
2155  // divide, so the covered range size is unit, otherwise it is the divisor.
2156  APInt RangeSize = Div->isExact() ? APInt(C2->getBitWidth(), 1) : *C2;
2157 
2158  // Figure out the interval that is being checked. For example, a comparison
2159  // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2160  // Compute this interval based on the constants involved and the signedness of
2161  // the compare/divide. This computes a half-open interval, keeping track of
2162  // whether either value in the interval overflows. After analysis each
2163  // overflow variable is set to 0 if it's corresponding bound variable is valid
2164  // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2165  int LoOverflow = 0, HiOverflow = 0;
2166  APInt LoBound, HiBound;
2167 
2168  if (!DivIsSigned) { // udiv
2169  // e.g. X/5 op 3 --> [15, 20)
2170  LoBound = Prod;
2171  HiOverflow = LoOverflow = ProdOV;
2172  if (!HiOverflow) {
2173  // If this is not an exact divide, then many values in the range collapse
2174  // to the same result value.
2175  HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2176  }
2177  } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
2178  if (C.isNullValue()) { // (X / pos) op 0
2179  // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2180  LoBound = -(RangeSize - 1);
2181  HiBound = RangeSize;
2182  } else if (C.isStrictlyPositive()) { // (X / pos) op pos
2183  LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2184  HiOverflow = LoOverflow = ProdOV;
2185  if (!HiOverflow)
2186  HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2187  } else { // (X / pos) op neg
2188  // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2189  HiBound = Prod + 1;
2190  LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2191  if (!LoOverflow) {
2192  APInt DivNeg = -RangeSize;
2193  LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2194  }
2195  }
2196  } else if (C2->isNegative()) { // Divisor is < 0.
2197  if (Div->isExact())
2198  RangeSize.negate();
2199  if (C.isNullValue()) { // (X / neg) op 0
2200  // e.g. X/-5 op 0 --> [-4, 5)
2201  LoBound = RangeSize + 1;
2202  HiBound = -RangeSize;
2203  if (HiBound == *C2) { // -INTMIN = INTMIN
2204  HiOverflow = 1; // [INTMIN+1, overflow)
2205  HiBound = APInt(); // e.g. X/INTMIN = 0 --> X > INTMIN
2206  }
2207  } else if (C.isStrictlyPositive()) { // (X / neg) op pos
2208  // e.g. X/-5 op 3 --> [-19, -14)
2209  HiBound = Prod + 1;
2210  HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2211  if (!LoOverflow)
2212  LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2213  } else { // (X / neg) op neg
2214  LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2215  LoOverflow = HiOverflow = ProdOV;
2216  if (!HiOverflow)
2217  HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2218  }
2219 
2220  // Dividing by a negative swaps the condition. LT <-> GT
2221  Pred = ICmpInst::getSwappedPredicate(Pred);
2222  }
2223 
2224  Value *X = Div->getOperand(0);
2225  switch (Pred) {
2226  default: llvm_unreachable("Unhandled icmp opcode!");
2227  case ICmpInst::ICMP_EQ:
2228  if (LoOverflow && HiOverflow)
2229  return replaceInstUsesWith(Cmp, Builder.getFalse());
2230  if (HiOverflow)
2231  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2232  ICmpInst::ICMP_UGE, X,
2233  ConstantInt::get(Div->getType(), LoBound));
2234  if (LoOverflow)
2235  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2236  ICmpInst::ICMP_ULT, X,
2237  ConstantInt::get(Div->getType(), HiBound));
2238  return replaceInstUsesWith(
2239  Cmp, insertRangeTest(X, LoBound, HiBound, DivIsSigned, true));
2240  case ICmpInst::ICMP_NE:
2241  if (LoOverflow && HiOverflow)
2242  return replaceInstUsesWith(Cmp, Builder.getTrue());
2243  if (HiOverflow)
2244  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2245  ICmpInst::ICMP_ULT, X,
2246  ConstantInt::get(Div->getType(), LoBound));
2247  if (LoOverflow)
2248  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2249  ICmpInst::ICMP_UGE, X,
2250  ConstantInt::get(Div->getType(), HiBound));
2251  return replaceInstUsesWith(Cmp,
2252  insertRangeTest(X, LoBound, HiBound,
2253  DivIsSigned, false));
2254  case ICmpInst::ICMP_ULT:
2255  case ICmpInst::ICMP_SLT:
2256  if (LoOverflow == +1) // Low bound is greater than input range.
2257  return replaceInstUsesWith(Cmp, Builder.getTrue());
2258  if (LoOverflow == -1) // Low bound is less than input range.
2259  return replaceInstUsesWith(Cmp, Builder.getFalse());
2260  return new ICmpInst(Pred, X, ConstantInt::get(Div->getType(), LoBound));
2261  case ICmpInst::ICMP_UGT:
2262  case ICmpInst::ICMP_SGT:
2263  if (HiOverflow == +1) // High bound greater than input range.
2264  return replaceInstUsesWith(Cmp, Builder.getFalse());
2265  if (HiOverflow == -1) // High bound less than input range.
2266  return replaceInstUsesWith(Cmp, Builder.getTrue());
2267  if (Pred == ICmpInst::ICMP_UGT)
2268  return new ICmpInst(ICmpInst::ICMP_UGE, X,
2269  ConstantInt::get(Div->getType(), HiBound));
2270  return new ICmpInst(ICmpInst::ICMP_SGE, X,
2271  ConstantInt::get(Div->getType(), HiBound));
2272  }
2273 
2274  return nullptr;
2275 }
2276 
2277 /// Fold icmp (sub X, Y), C.
2278 Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
2279  BinaryOperator *Sub,
2280  const APInt &C) {
2281  Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2282  ICmpInst::Predicate Pred = Cmp.getPredicate();
2283 
2284  // The following transforms are only worth it if the only user of the subtract
2285  // is the icmp.
2286  if (!Sub->hasOneUse())
2287  return nullptr;
2288 
2289  if (Sub->hasNoSignedWrap()) {
2290  // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2291  if (Pred == ICmpInst::ICMP_SGT && C.isAllOnesValue())
2292  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2293 
2294  // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2295  if (Pred == ICmpInst::ICMP_SGT && C.isNullValue())
2296  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2297 
2298  // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2299  if (Pred == ICmpInst::ICMP_SLT && C.isNullValue())
2300  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2301 
2302  // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2303  if (Pred == ICmpInst::ICMP_SLT && C.isOneValue())
2304  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2305  }
2306 
2307  const APInt *C2;
2308  if (!match(X, m_APInt(C2)))
2309  return nullptr;
2310 
2311  // C2 - Y <u C -> (Y | (C - 1)) == C2
2312  // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2313  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() &&
2314  (*C2 & (C - 1)) == (C - 1))
2315  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, C - 1), X);
2316 
2317  // C2 - Y >u C -> (Y | C) != C2
2318  // iff C2 & C == C and C + 1 is a power of 2
2319  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == C)
2320  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, C), X);
2321 
2322  return nullptr;
2323 }
2324 
2325 /// Fold icmp (add X, Y), C.
2326 Instruction *InstCombiner::foldICmpAddConstant(ICmpInst &Cmp,
2328  const APInt &C) {
2329  Value *Y = Add->getOperand(1);
2330  const APInt *C2;
2331  if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2332  return nullptr;
2333 
2334  // Fold icmp pred (add X, C2), C.
2335  Value *X = Add->getOperand(0);
2336  Type *Ty = Add->getType();
2337  CmpInst::Predicate Pred = Cmp.getPredicate();
2338 
2339  // If the add does not wrap, we can always adjust the compare by subtracting
2340  // the constants. Equality comparisons are handled elsewhere. SGE/SLE are
2341  // canonicalized to SGT/SLT.
2342  if (Add->hasNoSignedWrap() &&
2343  (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) {
2344  bool Overflow;
2345  APInt NewC = C.ssub_ov(*C2, Overflow);
2346  // If there is overflow, the result must be true or false.
2347  // TODO: Can we assert there is no overflow because InstSimplify always
2348  // handles those cases?
2349  if (!Overflow)
2350  // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2351  return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2352  }
2353 
2354  auto CR = ConstantRange::makeExactICmpRegion(Pred, C).subtract(*C2);
2355  const APInt &Upper = CR.getUpper();
2356  const APInt &Lower = CR.getLower();
2357  if (Cmp.isSigned()) {
2358  if (Lower.isSignMask())
2359  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2360  if (Upper.isSignMask())
2361  return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2362  } else {
2363  if (Lower.isMinValue())
2364  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2365  if (Upper.isMinValue())
2366  return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2367  }
2368 
2369  if (!Add->hasOneUse())
2370  return nullptr;
2371 
2372  // X+C <u C2 -> (X & -C2) == C
2373  // iff C & (C2-1) == 0
2374  // C2 is a power of 2
2375  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() && (*C2 & (C - 1)) == 0)
2376  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
2377  ConstantExpr::getNeg(cast<Constant>(Y)));
2378 
2379  // X+C >u C2 -> (X & ~C2) != C
2380  // iff C & C2 == 0
2381  // C2+1 is a power of 2
2382  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == 0)
2383  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~C),
2384  ConstantExpr::getNeg(cast<Constant>(Y)));
2385 
2386  return nullptr;
2387 }
2388 
2389 bool InstCombiner::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
2390  Value *&RHS, ConstantInt *&Less,
2391  ConstantInt *&Equal,
2392  ConstantInt *&Greater) {
2393  // TODO: Generalize this to work with other comparison idioms or ensure
2394  // they get canonicalized into this form.
2395 
2396  // select i1 (a == b), i32 Equal, i32 (select i1 (a < b), i32 Less, i32
2397  // Greater), where Equal, Less and Greater are placeholders for any three
2398  // constants.
2399  ICmpInst::Predicate PredA, PredB;
2400  if (match(SI->getTrueValue(), m_ConstantInt(Equal)) &&
2401  match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) &&
2402  PredA == ICmpInst::ICMP_EQ &&
2403  match(SI->getFalseValue(),
2404  m_Select(m_ICmp(PredB, m_Specific(LHS), m_Specific(RHS)),
2405  m_ConstantInt(Less), m_ConstantInt(Greater))) &&
2406  PredB == ICmpInst::ICMP_SLT) {
2407  return true;
2408  }
2409  return false;
2410 }
2411 
2412 Instruction *InstCombiner::foldICmpSelectConstant(ICmpInst &Cmp,
2413  SelectInst *Select,
2414  ConstantInt *C) {
2415 
2416  assert(C && "Cmp RHS should be a constant int!");
2417  // If we're testing a constant value against the result of a three way
2418  // comparison, the result can be expressed directly in terms of the
2419  // original values being compared. Note: We could possibly be more
2420  // aggressive here and remove the hasOneUse test. The original select is
2421  // really likely to simplify or sink when we remove a test of the result.
2422  Value *OrigLHS, *OrigRHS;
2423  ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
2424  if (Cmp.hasOneUse() &&
2425  matchThreeWayIntCompare(Select, OrigLHS, OrigRHS, C1LessThan, C2Equal,
2426  C3GreaterThan)) {
2427  assert(C1LessThan && C2Equal && C3GreaterThan);
2428 
2429  bool TrueWhenLessThan =
2430  ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
2431  ->isAllOnesValue();
2432  bool TrueWhenEqual =
2433  ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
2434  ->isAllOnesValue();
2435  bool TrueWhenGreaterThan =
2436  ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
2437  ->isAllOnesValue();
2438 
2439  // This generates the new instruction that will replace the original Cmp
2440  // Instruction. Instead of enumerating the various combinations when
2441  // TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
2442  // false, we rely on chaining of ORs and future passes of InstCombine to
2443  // simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
2444 
2445  // When none of the three constants satisfy the predicate for the RHS (C),
2446  // the entire original Cmp can be simplified to a false.
2447  Value *Cond = Builder.getFalse();
2448  if (TrueWhenLessThan)
2449  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT, OrigLHS, OrigRHS));
2450  if (TrueWhenEqual)
2451  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ, OrigLHS, OrigRHS));
2452  if (TrueWhenGreaterThan)
2453  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT, OrigLHS, OrigRHS));
2454 
2455  return replaceInstUsesWith(Cmp, Cond);
2456  }
2457  return nullptr;
2458 }
2459 
2460 Instruction *InstCombiner::foldICmpBitCastConstant(ICmpInst &Cmp,
2462  const APInt &C) {
2463  // Folding: icmp <pred> iN X, C
2464  // where X = bitcast <M x iK> (shufflevector <M x iK> %vec, undef, SC)) to iN
2465  // and C is a splat of a K-bit pattern
2466  // and SC is a constant vector = <C', C', C', ..., C'>
2467  // Into:
2468  // %E = extractelement <M x iK> %vec, i32 C'
2469  // icmp <pred> iK %E, trunc(C)
2470  if (!Bitcast->getType()->isIntegerTy() ||
2471  !Bitcast->getSrcTy()->isIntOrIntVectorTy())
2472  return nullptr;
2473 
2474  Value *BCIOp = Bitcast->getOperand(0);
2475  Value *Vec = nullptr; // 1st vector arg of the shufflevector
2476  Constant *Mask = nullptr; // Mask arg of the shufflevector
2477  if (match(BCIOp,
2478  m_ShuffleVector(m_Value(Vec), m_Undef(), m_Constant(Mask)))) {
2479  // Check whether every element of Mask is the same constant
2480  if (auto *Elem = dyn_cast_or_null<ConstantInt>(Mask->getSplatValue())) {
2481  auto *VecTy = cast<VectorType>(BCIOp->getType());
2482  auto *EltTy = cast<IntegerType>(VecTy->getElementType());
2483  auto Pred = Cmp.getPredicate();
2484  if (C.isSplat(EltTy->getBitWidth())) {
2485  // Fold the icmp based on the value of C
2486  // If C is M copies of an iK sized bit pattern,
2487  // then:
2488  // => %E = extractelement <N x iK> %vec, i32 Elem
2489  // icmp <pred> iK %SplatVal, <pattern>
2490  Value *Extract = Builder.CreateExtractElement(Vec, Elem);
2491  Value *NewC = ConstantInt::get(EltTy, C.trunc(EltTy->getBitWidth()));
2492  return new ICmpInst(Pred, Extract, NewC);
2493  }
2494  }
2495  }
2496  return nullptr;
2497 }
2498 
2499 /// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2500 /// where X is some kind of instruction.
2501 Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2502  const APInt *C;
2503  if (!match(Cmp.getOperand(1), m_APInt(C)))
2504  return nullptr;
2505 
2506  if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
2507  switch (BO->getOpcode()) {
2508  case Instruction::Xor:
2509  if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
2510  return I;
2511  break;
2512  case Instruction::And:
2513  if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
2514  return I;
2515  break;
2516  case Instruction::Or:
2517  if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
2518  return I;
2519  break;
2520  case Instruction::Mul:
2521  if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
2522  return I;
2523  break;
2524  case Instruction::Shl:
2525  if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
2526  return I;
2527  break;
2528  case Instruction::LShr:
2529  case Instruction::AShr:
2530  if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
2531  return I;
2532  break;
2533  case Instruction::UDiv:
2534  if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
2535  return I;
2537  case Instruction::SDiv:
2538  if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
2539  return I;
2540  break;
2541  case Instruction::Sub:
2542  if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
2543  return I;
2544  break;
2545  case Instruction::Add:
2546  if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
2547  return I;
2548  break;
2549  default:
2550  break;
2551  }
2552  // TODO: These folds could be refactored to be part of the above calls.
2553  if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
2554  return I;
2555  }
2556 
2557  // Match against CmpInst LHS being instructions other than binary operators.
2558 
2559  if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
2560  // For now, we only support constant integers while folding the
2561  // ICMP(SELECT)) pattern. We can extend this to support vector of integers
2562  // similar to the cases handled by binary ops above.
2563  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
2564  if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
2565  return I;
2566  }
2567 
2568  if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
2569  if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
2570  return I;
2571  }
2572 
2573  if (auto *BCI = dyn_cast<BitCastInst>(Cmp.getOperand(0))) {
2574  if (Instruction *I = foldICmpBitCastConstant(Cmp, BCI, *C))
2575  return I;
2576  }
2577 
2578  if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, *C))
2579  return I;
2580 
2581  return nullptr;
2582 }
2583 
2584 /// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2585 /// icmp eq/ne BO, C.
2586 Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2587  BinaryOperator *BO,
2588  const APInt &C) {
2589  // TODO: Some of these folds could work with arbitrary constants, but this
2590  // function is limited to scalar and vector splat constants.
2591  if (!Cmp.isEquality())
2592  return nullptr;
2593 
2594  ICmpInst::Predicate Pred = Cmp.getPredicate();
2595  bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2596  Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2597  Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2598 
2599  switch (BO->getOpcode()) {
2600  case Instruction::SRem:
2601  // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2602  if (C.isNullValue() && BO->hasOneUse()) {
2603  const APInt *BOC;
2604  if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2605  Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
2606  return new ICmpInst(Pred, NewRem,
2608  }
2609  }
2610  break;
2611  case Instruction::Add: {
2612  // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2613  const APInt *BOC;
2614  if (match(BOp1, m_APInt(BOC))) {
2615  if (BO->hasOneUse()) {
2616  Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2617  return new ICmpInst(Pred, BOp0, SubC);
2618  }
2619  } else if (C.isNullValue()) {
2620  // Replace ((add A, B) != 0) with (A != -B) if A or B is
2621  // efficiently invertible, or if the add has just this one use.
2622  if (Value *NegVal = dyn_castNegVal(BOp1))
2623  return new ICmpInst(Pred, BOp0, NegVal);
2624  if (Value *NegVal = dyn_castNegVal(BOp0))
2625  return new ICmpInst(Pred, NegVal, BOp1);
2626  if (BO->hasOneUse()) {
2627  Value *Neg = Builder.CreateNeg(BOp1);
2628  Neg->takeName(BO);
2629  return new ICmpInst(Pred, BOp0, Neg);
2630  }
2631  }
2632  break;
2633  }
2634  case Instruction::Xor:
2635  if (BO->hasOneUse()) {
2636  if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2637  // For the xor case, we can xor two constants together, eliminating
2638  // the explicit xor.
2639  return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2640  } else if (C.isNullValue()) {
2641  // Replace ((xor A, B) != 0) with (A != B)
2642  return new ICmpInst(Pred, BOp0, BOp1);
2643  }
2644  }
2645  break;
2646  case Instruction::Sub:
2647  if (BO->hasOneUse()) {
2648  const APInt *BOC;
2649  if (match(BOp0, m_APInt(BOC))) {
2650  // Replace ((sub BOC, B) != C) with (B != BOC-C).
2651  Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2652  return new ICmpInst(Pred, BOp1, SubC);
2653  } else if (C.isNullValue()) {
2654  // Replace ((sub A, B) != 0) with (A != B).
2655  return new ICmpInst(Pred, BOp0, BOp1);
2656  }
2657  }
2658  break;
2659  case Instruction::Or: {
2660  const APInt *BOC;
2661  if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2662  // Comparing if all bits outside of a constant mask are set?
2663  // Replace (X | C) == -1 with (X & ~C) == ~C.
2664  // This removes the -1 constant.
2665  Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2666  Value *And = Builder.CreateAnd(BOp0, NotBOC);
2667  return new ICmpInst(Pred, And, NotBOC);
2668  }
2669  break;
2670  }
2671  case Instruction::And: {
2672  const APInt *BOC;
2673  if (match(BOp1, m_APInt(BOC))) {
2674  // If we have ((X & C) == C), turn it into ((X & C) != 0).
2675  if (C == *BOC && C.isPowerOf2())
2676  return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2677  BO, Constant::getNullValue(RHS->getType()));
2678 
2679  // Don't perform the following transforms if the AND has multiple uses
2680  if (!BO->hasOneUse())
2681  break;
2682 
2683  // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2684  if (BOC->isSignMask()) {
2685  Constant *Zero = Constant::getNullValue(BOp0->getType());
2686  auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2687  return new ICmpInst(NewPred, BOp0, Zero);
2688  }
2689 
2690  // ((X & ~7) == 0) --> X < 8
2691  if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
2692  Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2693  auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2694  return new ICmpInst(NewPred, BOp0, NegBOC);
2695  }
2696  }
2697  break;
2698  }
2699  case Instruction::Mul:
2700  if (C.isNullValue() && BO->hasNoSignedWrap()) {
2701  const APInt *BOC;
2702  if (match(BOp1, m_APInt(BOC)) && !BOC->isNullValue()) {
2703  // The trivial case (mul X, 0) is handled by InstSimplify.
2704  // General case : (mul X, C) != 0 iff X != 0
2705  // (mul X, C) == 0 iff X == 0
2706  return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2707  }
2708  }
2709  break;
2710  case Instruction::UDiv:
2711  if (C.isNullValue()) {
2712  // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2713  auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2714  return new ICmpInst(NewPred, BOp1, BOp0);
2715  }
2716  break;
2717  default:
2718  break;
2719  }
2720  return nullptr;
2721 }
2722 
2723 /// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2724 Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2725  const APInt &C) {
2727  if (!II || !Cmp.isEquality())
2728  return nullptr;
2729 
2730  // Handle icmp {eq|ne} <intrinsic>, Constant.
2731  Type *Ty = II->getType();
2732  switch (II->getIntrinsicID()) {
2733  case Intrinsic::bswap:
2734  Worklist.Add(II);
2735  Cmp.setOperand(0, II->getArgOperand(0));
2736  Cmp.setOperand(1, ConstantInt::get(Ty, C.byteSwap()));
2737  return &Cmp;
2738 
2739  case Intrinsic::ctlz:
2740  case Intrinsic::cttz:
2741  // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2742  if (C == C.getBitWidth()) {
2743  Worklist.Add(II);
2744  Cmp.setOperand(0, II->getArgOperand(0));
2746  return &Cmp;
2747  }
2748  break;
2749 
2750  case Intrinsic::ctpop: {
2751  // popcount(A) == 0 -> A == 0 and likewise for !=
2752  // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2753  bool IsZero = C.isNullValue();
2754  if (IsZero || C == C.getBitWidth()) {
2755  Worklist.Add(II);
2756  Cmp.setOperand(0, II->getArgOperand(0));
2757  auto *NewOp =
2759  Cmp.setOperand(1, NewOp);
2760  return &Cmp;
2761  }
2762  break;
2763  }
2764  default:
2765  break;
2766  }
2767 
2768  return nullptr;
2769 }
2770 
2771 /// Handle icmp with constant (but not simple integer constant) RHS.
2772 Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2773  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2774  Constant *RHSC = dyn_cast<Constant>(Op1);
2775  Instruction *LHSI = dyn_cast<Instruction>(Op0);
2776  if (!RHSC || !LHSI)
2777  return nullptr;
2778 
2779  switch (LHSI->getOpcode()) {
2780  case Instruction::GetElementPtr:
2781  // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2782  if (RHSC->isNullValue() &&
2783  cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2784  return new ICmpInst(
2785  I.getPredicate(), LHSI->getOperand(0),
2786  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2787  break;
2788  case Instruction::PHI:
2789  // Only fold icmp into the PHI if the phi and icmp are in the same
2790  // block. If in the same block, we're encouraging jump threading. If
2791  // not, we are just pessimizing the code by making an i1 phi.
2792  if (LHSI->getParent() == I.getParent())
2793  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2794  return NV;
2795  break;
2796  case Instruction::Select: {
2797  // If either operand of the select is a constant, we can fold the
2798  // comparison into the select arms, which will cause one to be
2799  // constant folded and the select turned into a bitwise or.
2800  Value *Op1 = nullptr, *Op2 = nullptr;
2801  ConstantInt *CI = nullptr;
2802  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2803  Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2804  CI = dyn_cast<ConstantInt>(Op1);
2805  }
2806  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2807  Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2808  CI = dyn_cast<ConstantInt>(Op2);
2809  }
2810 
2811  // We only want to perform this transformation if it will not lead to
2812  // additional code. This is true if either both sides of the select
2813  // fold to a constant (in which case the icmp is replaced with a select
2814  // which will usually simplify) or this is the only user of the
2815  // select (in which case we are trading a select+icmp for a simpler
2816  // select+icmp) or all uses of the select can be replaced based on
2817  // dominance information ("Global cases").
2818  bool Transform = false;
2819  if (Op1 && Op2)
2820  Transform = true;
2821  else if (Op1 || Op2) {
2822  // Local case
2823  if (LHSI->hasOneUse())
2824  Transform = true;
2825  // Global cases
2826  else if (CI && !CI->isZero())
2827  // When Op1 is constant try replacing select with second operand.
2828  // Otherwise Op2 is constant and try replacing select with first
2829  // operand.
2830  Transform =
2831  replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2832  }
2833  if (Transform) {
2834  if (!Op1)
2835  Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2836  I.getName());
2837  if (!Op2)
2838  Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2839  I.getName());
2840  return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2841  }
2842  break;
2843  }
2844  case Instruction::IntToPtr:
2845  // icmp pred inttoptr(X), null -> icmp pred X, 0
2846  if (RHSC->isNullValue() &&
2847  DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2848  return new ICmpInst(
2849  I.getPredicate(), LHSI->getOperand(0),
2850  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2851  break;
2852 
2853  case Instruction::Load:
2854  // Try to optimize things like "A[i] > 4" to index computations.
2855  if (GetElementPtrInst *GEP =
2856  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2857  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2858  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2859  !cast<LoadInst>(LHSI)->isVolatile())
2860  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2861  return Res;
2862  }
2863  break;
2864  }
2865 
2866  return nullptr;
2867 }
2868 
2869 /// Try to fold icmp (binop), X or icmp X, (binop).
2870 /// TODO: A large part of this logic is duplicated in InstSimplify's
2871 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
2872 /// duplication.
2873 Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2874  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2875 
2876  // Special logic for binary operators.
2877  BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2878  BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2879  if (!BO0 && !BO1)
2880  return nullptr;
2881 
2882  const CmpInst::Predicate Pred = I.getPredicate();
2883  bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2884  if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2885  NoOp0WrapProblem =
2886  ICmpInst::isEquality(Pred) ||
2887  (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2888  (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2889  if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2890  NoOp1WrapProblem =
2891  ICmpInst::isEquality(Pred) ||
2892  (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2893  (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2894 
2895  // Analyze the case when either Op0 or Op1 is an add instruction.
2896  // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2897  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2898  if (BO0 && BO0->getOpcode() == Instruction::Add) {
2899  A = BO0->getOperand(0);
2900  B = BO0->getOperand(1);
2901  }
2902  if (BO1 && BO1->getOpcode() == Instruction::Add) {
2903  C = BO1->getOperand(0);
2904  D = BO1->getOperand(1);
2905  }
2906 
2907  // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2908  if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2909  return new ICmpInst(Pred, A == Op1 ? B : A,
2910  Constant::getNullValue(Op1->getType()));
2911 
2912  // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2913  if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2914  return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2915  C == Op0 ? D : C);
2916 
2917  // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2918  if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2919  NoOp1WrapProblem &&
2920  // Try not to increase register pressure.
2921  BO0->hasOneUse() && BO1->hasOneUse()) {
2922  // Determine Y and Z in the form icmp (X+Y), (X+Z).
2923  Value *Y, *Z;
2924  if (A == C) {
2925  // C + B == C + D -> B == D
2926  Y = B;
2927  Z = D;
2928  } else if (A == D) {
2929  // D + B == C + D -> B == C
2930  Y = B;
2931  Z = C;
2932  } else if (B == C) {
2933  // A + C == C + D -> A == D
2934  Y = A;
2935  Z = D;
2936  } else {
2937  assert(B == D);
2938  // A + D == C + D -> A == C
2939  Y = A;
2940  Z = C;
2941  }
2942  return new ICmpInst(Pred, Y, Z);
2943  }
2944 
2945  // icmp slt (X + -1), Y -> icmp sle X, Y
2946  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2947  match(B, m_AllOnes()))
2948  return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2949 
2950  // icmp sge (X + -1), Y -> icmp sgt X, Y
2951  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2952  match(B, m_AllOnes()))
2953  return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2954 
2955  // icmp sle (X + 1), Y -> icmp slt X, Y
2956  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2957  return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2958 
2959  // icmp sgt (X + 1), Y -> icmp sge X, Y
2960  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2961  return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2962 
2963  // icmp sgt X, (Y + -1) -> icmp sge X, Y
2964  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2965  match(D, m_AllOnes()))
2966  return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2967 
2968  // icmp sle X, (Y + -1) -> icmp slt X, Y
2969  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2970  match(D, m_AllOnes()))
2971  return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2972 
2973  // icmp sge X, (Y + 1) -> icmp sgt X, Y
2974  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
2975  return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
2976 
2977  // icmp slt X, (Y + 1) -> icmp sle X, Y
2978  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
2979  return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
2980 
2981  // TODO: The subtraction-related identities shown below also hold, but
2982  // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
2983  // wouldn't happen even if they were implemented.
2984  //
2985  // icmp ult (X - 1), Y -> icmp ule X, Y
2986  // icmp uge (X - 1), Y -> icmp ugt X, Y
2987  // icmp ugt X, (Y - 1) -> icmp uge X, Y
2988  // icmp ule X, (Y - 1) -> icmp ult X, Y
2989 
2990  // icmp ule (X + 1), Y -> icmp ult X, Y
2991  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
2992  return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
2993 
2994  // icmp ugt (X + 1), Y -> icmp uge X, Y
2995  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
2996  return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
2997 
2998  // icmp uge X, (Y + 1) -> icmp ugt X, Y
2999  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
3000  return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
3001 
3002  // icmp ult X, (Y + 1) -> icmp ule X, Y
3003  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
3004  return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
3005 
3006  // if C1 has greater magnitude than C2:
3007  // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
3008  // s.t. C3 = C1 - C2
3009  //
3010  // if C2 has greater magnitude than C1:
3011  // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
3012  // s.t. C3 = C2 - C1
3013  if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
3014  (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
3015  if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
3016  if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
3017  const APInt &AP1 = C1->getValue();
3018  const APInt &AP2 = C2->getValue();
3019  if (AP1.isNegative() == AP2.isNegative()) {
3020  APInt AP1Abs = C1->getValue().abs();
3021  APInt AP2Abs = C2->getValue().abs();
3022  if (AP1Abs.uge(AP2Abs)) {
3023  ConstantInt *C3 = Builder.getInt(AP1 - AP2);
3024  Value *NewAdd = Builder.CreateNSWAdd(A, C3);
3025  return new ICmpInst(Pred, NewAdd, C);
3026  } else {
3027  ConstantInt *C3 = Builder.getInt(AP2 - AP1);
3028  Value *NewAdd = Builder.CreateNSWAdd(C, C3);
3029  return new ICmpInst(Pred, A, NewAdd);
3030  }
3031  }
3032  }
3033 
3034  // Analyze the case when either Op0 or Op1 is a sub instruction.
3035  // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
3036  A = nullptr;
3037  B = nullptr;
3038  C = nullptr;
3039  D = nullptr;
3040  if (BO0 && BO0->getOpcode() == Instruction::Sub) {
3041  A = BO0->getOperand(0);
3042  B = BO0->getOperand(1);
3043  }
3044  if (BO1 && BO1->getOpcode() == Instruction::Sub) {
3045  C = BO1->getOperand(0);
3046  D = BO1->getOperand(1);
3047  }
3048 
3049  // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
3050  if (A == Op1 && NoOp0WrapProblem)
3051  return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
3052  // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
3053  if (C == Op0 && NoOp1WrapProblem)
3054  return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
3055 
3056  // (A - B) >u A --> A <u B
3057  if (A == Op1 && Pred == ICmpInst::ICMP_UGT)
3058  return new ICmpInst(ICmpInst::ICMP_ULT, A, B);
3059  // C <u (C - D) --> C <u D
3060  if (C == Op0 && Pred == ICmpInst::ICMP_ULT)
3061  return new ICmpInst(ICmpInst::ICMP_ULT, C, D);
3062 
3063  // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
3064  if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
3065  // Try not to increase register pressure.
3066  BO0->hasOneUse() && BO1->hasOneUse())
3067  return new ICmpInst(Pred, A, C);
3068  // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
3069  if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
3070  // Try not to increase register pressure.
3071  BO0->hasOneUse() && BO1->hasOneUse())
3072  return new ICmpInst(Pred, D, B);
3073 
3074  // icmp (0-X) < cst --> x > -cst
3075  if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
3076  Value *X;
3077  if (match(BO0, m_Neg(m_Value(X))))
3078  if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3079  if (!RHSC->isMinValue(/*isSigned=*/true))
3080  return new ICmpInst(I.getSwappedPredicate(), X,
3081  ConstantExpr::getNeg(RHSC));
3082  }
3083 
3084  BinaryOperator *SRem = nullptr;
3085  // icmp (srem X, Y), Y
3086  if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
3087  SRem = BO0;
3088  // icmp Y, (srem X, Y)
3089  else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3090  Op0 == BO1->getOperand(1))
3091  SRem = BO1;
3092  if (SRem) {
3093  // We don't check hasOneUse to avoid increasing register pressure because
3094  // the value we use is the same value this instruction was already using.
3095  switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3096  default:
3097  break;
3098  case ICmpInst::ICMP_EQ:
3099  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3100  case ICmpInst::ICMP_NE:
3101  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3102  case ICmpInst::ICMP_SGT:
3103  case ICmpInst::ICMP_SGE:
3104  return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3106  case ICmpInst::ICMP_SLT:
3107  case ICmpInst::ICMP_SLE:
3108  return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3109  Constant::getNullValue(SRem->getType()));
3110  }
3111  }
3112 
3113  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3114  BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3115  switch (BO0->getOpcode()) {
3116  default:
3117  break;
3118  case Instruction::Add:
3119  case Instruction::Sub:
3120  case Instruction::Xor: {
3121  if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3122  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3123 
3124  const APInt *C;
3125  if (match(BO0->getOperand(1), m_APInt(C))) {
3126  // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3127  if (C->isSignMask()) {
3128  ICmpInst::Predicate NewPred =
3130  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3131  }
3132 
3133  // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
3134  if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
3135  ICmpInst::Predicate NewPred =
3137  NewPred = I.getSwappedPredicate(NewPred);
3138  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3139  }
3140  }
3141  break;
3142  }
3143  case Instruction::Mul: {
3144  if (!I.isEquality())
3145  break;
3146 
3147  const APInt *C;
3148  if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
3149  !C->isOneValue()) {
3150  // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
3151  // Mask = -1 >> count-trailing-zeros(C).
3152  if (unsigned TZs = C->countTrailingZeros()) {
3154  BO0->getType(),
3155  APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
3156  Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
3157  Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
3158  return new ICmpInst(Pred, And1, And2);
3159  }
3160  // If there are no trailing zeros in the multiplier, just eliminate
3161  // the multiplies (no masking is needed):
3162  // icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
3163  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3164  }
3165  break;
3166  }
3167  case Instruction::UDiv:
3168  case Instruction::LShr:
3169  if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
3170  break;
3171  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3172 
3173  case Instruction::SDiv:
3174  if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
3175  break;
3176  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3177 
3178  case Instruction::AShr:
3179  if (!BO0->isExact() || !BO1->isExact())
3180  break;
3181  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3182 
3183  case Instruction::Shl: {
3184  bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3185  bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3186  if (!NUW && !NSW)
3187  break;
3188  if (!NSW && I.isSigned())
3189  break;
3190  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3191  }
3192  }
3193  }
3194 
3195  if (BO0) {
3196  // Transform A & (L - 1) `ult` L --> L != 0
3197  auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3198  auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
3199 
3200  if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
3201  auto *Zero = Constant::getNullValue(BO0->getType());
3202  return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3203  }
3204  }
3205 
3206  return nullptr;
3207 }
3208 
3209 /// Fold icmp Pred min|max(X, Y), X.
3211  ICmpInst::Predicate Pred = Cmp.getPredicate();
3212  Value *Op0 = Cmp.getOperand(0);
3213  Value *X = Cmp.getOperand(1);
3214 
3215  // Canonicalize minimum or maximum operand to LHS of the icmp.
3216  if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3217  match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3218  match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3219  match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3220  std::swap(Op0, X);
3221  Pred = Cmp.getSwappedPredicate();
3222  }
3223 
3224  Value *Y;
3225  if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3226  // smin(X, Y) == X --> X s<= Y
3227  // smin(X, Y) s>= X --> X s<= Y
3228  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3229  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3230 
3231  // smin(X, Y) != X --> X s> Y
3232  // smin(X, Y) s< X --> X s> Y
3233  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3234  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3235 
3236  // These cases should be handled in InstSimplify:
3237  // smin(X, Y) s<= X --> true
3238  // smin(X, Y) s> X --> false
3239  return nullptr;
3240  }
3241 
3242  if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3243  // smax(X, Y) == X --> X s>= Y
3244  // smax(X, Y) s<= X --> X s>= Y
3245  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3246  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3247 
3248  // smax(X, Y) != X --> X s< Y
3249  // smax(X, Y) s> X --> X s< Y
3250  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3251  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3252 
3253  // These cases should be handled in InstSimplify:
3254  // smax(X, Y) s>= X --> true
3255  // smax(X, Y) s< X --> false
3256  return nullptr;
3257  }
3258 
3259  if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3260  // umin(X, Y) == X --> X u<= Y
3261  // umin(X, Y) u>= X --> X u<= Y
3262  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3263  return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3264 
3265  // umin(X, Y) != X --> X u> Y
3266  // umin(X, Y) u< X --> X u> Y
3267  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3268  return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3269 
3270  // These cases should be handled in InstSimplify:
3271  // umin(X, Y) u<= X --> true
3272  // umin(X, Y) u> X --> false
3273  return nullptr;
3274  }
3275 
3276  if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3277  // umax(X, Y) == X --> X u>= Y
3278  // umax(X, Y) u<= X --> X u>= Y
3279  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3280  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3281 
3282  // umax(X, Y) != X --> X u< Y
3283  // umax(X, Y) u> X --> X u< Y
3284  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3285  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3286 
3287  // These cases should be handled in InstSimplify:
3288  // umax(X, Y) u>= X --> true
3289  // umax(X, Y) u< X --> false
3290  return nullptr;
3291  }
3292 
3293  return nullptr;
3294 }
3295 
3296 Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3297  if (!I.isEquality())
3298  return nullptr;
3299 
3300  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3301  const CmpInst::Predicate Pred = I.getPredicate();
3302  Value *A, *B, *C, *D;
3303  if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3304  if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3305  Value *OtherVal = A == Op1 ? B : A;
3306  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3307  }
3308 
3309  if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3310  // A^c1 == C^c2 --> A == C^(c1^c2)
3311  ConstantInt *C1, *C2;
3312  if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3313  Op1->hasOneUse()) {
3314  Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
3315  Value *Xor = Builder.CreateXor(C, NC);
3316  return new ICmpInst(Pred, A, Xor);
3317  }
3318 
3319  // A^B == A^D -> B == D
3320  if (A == C)
3321  return new ICmpInst(Pred, B, D);
3322  if (A == D)
3323  return new ICmpInst(Pred, B, C);
3324  if (B == C)
3325  return new ICmpInst(Pred, A, D);
3326  if (B == D)
3327  return new ICmpInst(Pred, A, C);
3328  }
3329  }
3330 
3331  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3332  // A == (A^B) -> B == 0
3333  Value *OtherVal = A == Op0 ? B : A;
3334  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3335  }
3336 
3337  // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3338  if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3339  match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3340  Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3341 
3342  if (A == C) {
3343  X = B;
3344  Y = D;
3345  Z = A;
3346  } else if (A == D) {
3347  X = B;
3348  Y = C;
3349  Z = A;
3350  } else if (B == C) {
3351  X = A;
3352  Y = D;
3353  Z = B;
3354  } else if (B == D) {
3355  X = A;
3356  Y = C;
3357  Z = B;
3358  }
3359 
3360  if (X) { // Build (X^Y) & Z
3361  Op1 = Builder.CreateXor(X, Y);
3362  Op1 = Builder.CreateAnd(Op1, Z);
3363  I.setOperand(0, Op1);
3364  I.setOperand(1, Constant::getNullValue(Op1->getType()));
3365  return &I;
3366  }
3367  }
3368 
3369  // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3370  // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3371  ConstantInt *Cst1;
3372  if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3373  match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3374  (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3375  match(Op1, m_ZExt(m_Value(A))))) {
3376  APInt Pow2 = Cst1->getValue() + 1;
3377  if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3378  Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3379  return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
3380  }
3381 
3382  // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3383  // For lshr and ashr pairs.
3384  if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3385  match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3386  (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3387  match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3388  unsigned TypeBits = Cst1->getBitWidth();
3389  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3390  if (ShAmt < TypeBits && ShAmt != 0) {
3391  ICmpInst::Predicate NewPred =
3393  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3394  APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3395  return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
3396  }
3397  }
3398 
3399  // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3400  if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3401  match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3402  unsigned TypeBits = Cst1->getBitWidth();
3403  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3404  if (ShAmt < TypeBits && ShAmt != 0) {
3405  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3406  APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3407  Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
3408  I.getName() + ".mask");
3409  return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
3410  }
3411  }
3412 
3413  // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3414  // "icmp (and X, mask), cst"
3415  uint64_t ShAmt = 0;
3416  if (Op0->hasOneUse() &&
3417  match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3418  match(Op1, m_ConstantInt(Cst1)) &&
3419  // Only do this when A has multiple uses. This is most important to do
3420  // when it exposes other optimizations.
3421  !A->hasOneUse()) {
3422  unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3423 
3424  if (ShAmt < ASize) {
3425  APInt MaskV =
3427  MaskV <<= ShAmt;
3428 
3429  APInt CmpV = Cst1->getValue().zext(ASize);
3430  CmpV <<= ShAmt;
3431 
3432  Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
3433  return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
3434  }
3435  }
3436 
3437  // If both operands are byte-swapped or bit-reversed, just compare the
3438  // original values.
3439  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
3440  // and handle more intrinsics.
3441  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
3442  (match(Op0, m_BitReverse(m_Value(A))) &&
3443  match(Op1, m_BitReverse(m_Value(B)))))
3444  return new ICmpInst(Pred, A, B);
3445 
3446  return nullptr;
3447 }
3448 
3449 /// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3450 /// far.
3451 Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3452  const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3453  Value *LHSCIOp = LHSCI->getOperand(0);
3454  Type *SrcTy = LHSCIOp->getType();
3455  Type *DestTy = LHSCI->getType();
3456  Value *RHSCIOp;
3457 
3458  // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3459  // integer type is the same size as the pointer type.
3460  const auto& CompatibleSizes = [&](Type* SrcTy, Type* DestTy) -> bool {
3461  if (isa<VectorType>(SrcTy)) {
3462  SrcTy = cast<VectorType>(SrcTy)->getElementType();
3463  DestTy = cast<VectorType>(DestTy)->getElementType();
3464  }
3465  return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
3466  };
3467  if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3468  CompatibleSizes(SrcTy, DestTy)) {
3469  Value *RHSOp = nullptr;
3470  if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3471  Value *RHSCIOp = RHSC->getOperand(0);
3472  if (RHSCIOp->getType()->getPointerAddressSpace() ==
3473  LHSCIOp->getType()->getPointerAddressSpace()) {
3474  RHSOp = RHSC->getOperand(0);
3475  // If the pointer types don't match, insert a bitcast.
3476  if (LHSCIOp->getType() != RHSOp->getType())
3477  RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
3478  }
3479  } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3480  RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3481  }
3482 
3483  if (RHSOp)
3484  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3485  }
3486 
3487  // The code below only handles extension cast instructions, so far.
3488  // Enforce this.
3489  if (LHSCI->getOpcode() != Instruction::ZExt &&
3490  LHSCI->getOpcode() != Instruction::SExt)
3491  return nullptr;
3492 
3493  bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3494  bool isSignedCmp = ICmp.isSigned();
3495 
3496  if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3497  // Not an extension from the same type?
3498  RHSCIOp = CI->getOperand(0);
3499  if (RHSCIOp->getType() != LHSCIOp->getType())
3500  return nullptr;
3501 
3502  // If the signedness of the two casts doesn't agree (i.e. one is a sext
3503  // and the other is a zext), then we can't handle this.
3504  if (CI->getOpcode() != LHSCI->getOpcode())
3505  return nullptr;
3506 
3507  // Deal with equality cases early.
3508  if (ICmp.isEquality())
3509  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3510 
3511  // A signed comparison of sign extended values simplifies into a
3512  // signed comparison.
3513  if (isSignedCmp && isSignedExt)
3514  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3515 
3516  // The other three cases all fold into an unsigned comparison.
3517  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3518  }
3519 
3520  // If we aren't dealing with a constant on the RHS, exit early.
3521  auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3522  if (!C)
3523  return nullptr;
3524 
3525  // Compute the constant that would happen if we truncated to SrcTy then
3526  // re-extended to DestTy.
3527  Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3528  Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3529 
3530  // If the re-extended constant didn't change...
3531  if (Res2 == C) {
3532  // Deal with equality cases early.
3533  if (ICmp.isEquality())
3534  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3535 
3536  // A signed comparison of sign extended values simplifies into a
3537  // signed comparison.
3538  if (isSignedExt && isSignedCmp)
3539  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3540 
3541  // The other three cases all fold into an unsigned comparison.
3542  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3543  }
3544 
3545  // The re-extended constant changed, partly changed (in the case of a vector),
3546  // or could not be determined to be equal (in the case of a constant
3547  // expression), so the constant cannot be represented in the shorter type.
3548  // Consequently, we cannot emit a simple comparison.
3549  // All the cases that fold to true or false will have already been handled
3550  // by SimplifyICmpInst, so only deal with the tricky case.
3551 
3552  if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3553  return nullptr;
3554 
3555  // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3556  // should have been folded away previously and not enter in here.
3557 
3558  // We're performing an unsigned comp with a sign extended value.
3559  // This is true if the input is >= 0. [aka >s -1]
3560  Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3561  Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3562 
3563  // Finally, return the value computed.
3564  if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3565  return replaceInstUsesWith(ICmp, Result);
3566 
3567  assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
3568  return BinaryOperator::CreateNot(Result);
3569 }
3570 
3571 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3572  Value *RHS, Instruction &OrigI,
3573  Value *&Result, Constant *&Overflow) {
3574  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3575  std::swap(LHS, RHS);
3576 
3577  auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3578  Result = OpResult;
3579  Overflow = OverflowVal;
3580  if (ReuseName)
3581  Result->takeName(&OrigI);
3582  return true;
3583  };
3584 
3585  // If the overflow check was an add followed by a compare, the insertion point
3586  // may be pointing to the compare. We want to insert the new instructions
3587  // before the add in case there are uses of the add between the add and the
3588  // compare.
3589  Builder.SetInsertPoint(&OrigI);
3590 
3591  switch (OCF) {
3592  case OCF_INVALID:
3593  llvm_unreachable("bad overflow check kind!");
3594 
3595  case OCF_UNSIGNED_ADD: {
3596  OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3598  return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
3599  true);
3600 
3602  return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
3603 
3604  // Fall through uadd into sadd
3606  }
3607  case OCF_SIGNED_ADD: {
3608  // X + 0 -> {X, false}
3609  if (match(RHS, m_Zero()))
3610  return SetResult(LHS, Builder.getFalse(), false);
3611 
3612  // We can strength reduce this signed add into a regular add if we can prove
3613  // that it will never overflow.
3614  if (OCF == OCF_SIGNED_ADD)
3615  if (willNotOverflowSignedAdd(LHS, RHS, OrigI))
3616  return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
3617  true);
3618  break;
3619  }
3620 
3621  case OCF_UNSIGNED_SUB:
3622  case OCF_SIGNED_SUB: {
3623  // X - 0 -> {X, false}
3624  if (match(RHS, m_Zero()))
3625  return SetResult(LHS, Builder.getFalse(), false);
3626 
3627  if (OCF == OCF_SIGNED_SUB) {
3628  if (willNotOverflowSignedSub(LHS, RHS, OrigI))
3629  return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
3630  true);
3631  } else {
3632  if (willNotOverflowUnsignedSub(LHS, RHS, OrigI))
3633  return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
3634  true);
3635  }
3636  break;
3637  }
3638 
3639  case OCF_UNSIGNED_MUL: {
3640  OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3642  return SetResult(Builder.CreateNUWMul(LHS, RHS), Builder.getFalse(),
3643  true);
3645  return SetResult(Builder.CreateMul(LHS, RHS), Builder.getTrue(), true);
3647  }
3648  case OCF_SIGNED_MUL:
3649  // X * undef -> undef
3650  if (isa<UndefValue>(RHS))
3651  return SetResult(RHS, UndefValue::get(Builder.getInt1Ty()), false);
3652 
3653  // X * 0 -> {0, false}
3654  if (match(RHS, m_Zero()))
3655  return SetResult(RHS, Builder.getFalse(), false);
3656 
3657  // X * 1 -> {X, false}
3658  if (match(RHS, m_One()))
3659  return SetResult(LHS, Builder.getFalse(), false);
3660 
3661  if (OCF == OCF_SIGNED_MUL)
3662  if (willNotOverflowSignedMul(LHS, RHS, OrigI))
3663  return SetResult(Builder.CreateNSWMul(LHS, RHS), Builder.getFalse(),
3664  true);
3665  break;
3666  }
3667 
3668  return false;
3669 }
3670 
3671 /// Recognize and process idiom involving test for multiplication
3672 /// overflow.
3673 ///
3674 /// The caller has matched a pattern of the form:
3675 /// I = cmp u (mul(zext A, zext B), V
3676 /// The function checks if this is a test for overflow and if so replaces
3677 /// multiplication with call to 'mul.with.overflow' intrinsic.
3678 ///
3679 /// \param I Compare instruction.
3680 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3681 /// the compare instruction. Must be of integer type.
3682 /// \param OtherVal The other argument of compare instruction.
3683 /// \returns Instruction which must replace the compare instruction, NULL if no
3684 /// replacement required.
3686  Value *OtherVal, InstCombiner &IC) {
3687  // Don't bother doing this transformation for pointers, don't do it for
3688  // vectors.
3689  if (!isa<IntegerType>(MulVal->getType()))
3690  return nullptr;
3691 
3692  assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
3693  assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
3694  auto *MulInstr = dyn_cast<Instruction>(MulVal);
3695  if (!MulInstr)
3696  return nullptr;
3697  assert(MulInstr->getOpcode() == Instruction::Mul);
3698 
3699  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3700  *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3701  assert(LHS->getOpcode() == Instruction::ZExt);
3702  assert(RHS->getOpcode() == Instruction::ZExt);
3703  Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3704 
3705  // Calculate type and width of the result produced by mul.with.overflow.
3706  Type *TyA = A->getType(), *TyB = B->getType();
3707  unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3708  WidthB = TyB->getPrimitiveSizeInBits();
3709  unsigned MulWidth;
3710  Type *MulType;
3711  if (WidthB > WidthA) {
3712  MulWidth = WidthB;
3713  MulType = TyB;
3714  } else {
3715  MulWidth = WidthA;
3716  MulType = TyA;
3717  }
3718 
3719  // In order to replace the original mul with a narrower mul.with.overflow,
3720  // all uses must ignore upper bits of the product. The number of used low
3721  // bits must be not greater than the width of mul.with.overflow.
3722  if (MulVal->hasNUsesOrMore(2))
3723  for (User *U : MulVal->users()) {
3724  if (U == &I)
3725  continue;
3726  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3727  // Check if truncation ignores bits above MulWidth.
3728  unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3729  if (TruncWidth > MulWidth)
3730  return nullptr;
3731  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3732  // Check if AND ignores bits above MulWidth.
3733  if (BO->getOpcode() != Instruction::And)
3734  return nullptr;
3735  if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3736  const APInt &CVal = CI->getValue();
3737  if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3738  return nullptr;
3739  } else {
3740  // In this case we could have the operand of the binary operation
3741  // being defined in another block, and performing the replacement
3742  // could break the dominance relation.
3743  return nullptr;
3744  }
3745  } else {
3746  // Other uses prohibit this transformation.
3747  return nullptr;
3748  }
3749  }
3750 
3751  // Recognize patterns
3752  switch (I.getPredicate()) {
3753  case ICmpInst::ICMP_EQ:
3754  case ICmpInst::ICMP_NE:
3755  // Recognize pattern:
3756  // mulval = mul(zext A, zext B)
3757  // cmp eq/neq mulval, zext trunc mulval
3758  if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3759  if (Zext->hasOneUse()) {
3760  Value *ZextArg = Zext->getOperand(0);
3761  if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3762  if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3763  break; //Recognized
3764  }
3765 
3766  // Recognize pattern:
3767  // mulval = mul(zext A, zext B)
3768  // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3769  ConstantInt *CI;
3770  Value *ValToMask;
3771  if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3772  if (ValToMask != MulVal)
3773  return nullptr;
3774  const APInt &CVal = CI->getValue() + 1;
3775  if (CVal.isPowerOf2()) {
3776  unsigned MaskWidth = CVal.logBase2();
3777  if (MaskWidth == MulWidth)
3778  break; // Recognized
3779  }
3780  }
3781  return nullptr;
3782 
3783  case ICmpInst::ICMP_UGT:
3784  // Recognize pattern:
3785  // mulval = mul(zext A, zext B)
3786  // cmp ugt mulval, max
3787  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3788  APInt MaxVal = APInt::getMaxValue(MulWidth);
3789  MaxVal = MaxVal.zext(CI->getBitWidth());
3790  if (MaxVal.eq(CI->getValue()))
3791  break; // Recognized
3792  }
3793  return nullptr;
3794 
3795  case ICmpInst::ICMP_UGE:
3796  // Recognize pattern:
3797  // mulval = mul(zext A, zext B)
3798  // cmp uge mulval, max+1
3799  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3800  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3801  if (MaxVal.eq(CI->getValue()))
3802  break; // Recognized
3803  }
3804  return nullptr;
3805 
3806  case ICmpInst::ICMP_ULE:
3807  // Recognize pattern:
3808  // mulval = mul(zext A, zext B)
3809  // cmp ule mulval, max
3810  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3811  APInt MaxVal = APInt::getMaxValue(MulWidth);
3812  MaxVal = MaxVal.zext(CI->getBitWidth());
3813  if (MaxVal.eq(CI->getValue()))
3814  break; // Recognized
3815  }
3816  return nullptr;
3817 
3818  case ICmpInst::ICMP_ULT:
3819  // Recognize pattern:
3820  // mulval = mul(zext A, zext B)
3821  // cmp ule mulval, max + 1
3822  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3823  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3824  if (MaxVal.eq(CI->getValue()))
3825  break; // Recognized
3826  }
3827  return nullptr;
3828 
3829  default:
3830  return nullptr;
3831  }
3832 
3833  InstCombiner::BuilderTy &Builder = IC.Builder;
3834  Builder.SetInsertPoint(MulInstr);
3835 
3836  // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3837  Value *MulA = A, *MulB = B;
3838  if (WidthA < MulWidth)
3839  MulA = Builder.CreateZExt(A, MulType);
3840  if (WidthB < MulWidth)
3841  MulB = Builder.CreateZExt(B, MulType);
3843  Intrinsic::umul_with_overflow, MulType);
3844  CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
3845  IC.Worklist.Add(MulInstr);
3846 
3847  // If there are uses of mul result other than the comparison, we know that
3848  // they are truncation or binary AND. Change them to use result of
3849  // mul.with.overflow and adjust properly mask/size.
3850  if (MulVal->hasNUsesOrMore(2)) {
3851  Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
3852  for (auto UI = MulVal->user_begin(), UE = MulVal->user_end(); UI != UE;) {
3853  User *U = *UI++;
3854  if (U == &I || U == OtherVal)
3855  continue;
3856  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3857  if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3858  IC.replaceInstUsesWith(*TI, Mul);
3859  else
3860  TI->setOperand(0, Mul);
3861  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3862  assert(BO->getOpcode() == Instruction::And);
3863  // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3864  ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3865  APInt ShortMask = CI->getValue().trunc(MulWidth);
3866  Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
3867  Instruction *Zext =
3868  cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
3869  IC.Worklist.Add(Zext);
3870  IC.replaceInstUsesWith(*BO, Zext);
3871  } else {
3872  llvm_unreachable("Unexpected Binary operation");
3873  }
3874  IC.Worklist.Add(cast<Instruction>(U));
3875  }
3876  }
3877  if (isa<Instruction>(OtherVal))
3878  IC.Worklist.Add(cast<Instruction>(OtherVal));
3879 
3880  // The original icmp gets replaced with the overflow value, maybe inverted
3881  // depending on predicate.
3882  bool Inverse = false;
3883  switch (I.getPredicate()) {
3884  case ICmpInst::ICMP_NE:
3885  break;
3886  case ICmpInst::ICMP_EQ:
3887  Inverse = true;
3888  break;
3889  case ICmpInst::ICMP_UGT:
3890  case ICmpInst::ICMP_UGE:
3891  if (I.getOperand(0) == MulVal)
3892  break;
3893  Inverse = true;
3894  break;
3895  case ICmpInst::ICMP_ULT:
3896  case ICmpInst::ICMP_ULE:
3897  if (I.getOperand(1) == MulVal)
3898  break;
3899  Inverse = true;
3900  break;
3901  default:
3902  llvm_unreachable("Unexpected predicate");
3903  }
3904  if (Inverse) {
3905  Value *Res = Builder.CreateExtractValue(Call, 1);
3906  return BinaryOperator::CreateNot(Res);
3907  }
3908 
3909  return ExtractValueInst::Create(Call, 1);
3910 }
3911 
3912 /// When performing a comparison against a constant, it is possible that not all
3913 /// the bits in the LHS are demanded. This helper method computes the mask that
3914 /// IS demanded.
3915 static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
3916  const APInt *RHS;
3917  if (!match(I.getOperand(1), m_APInt(RHS)))
3918  return APInt::getAllOnesValue(BitWidth);
3919 
3920  // If this is a normal comparison, it demands all bits. If it is a sign bit
3921  // comparison, it only demands the sign bit.
3922  bool UnusedBit;
3923  if (isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
3924  return APInt::getSignMask(BitWidth);
3925 
3926  switch (I.getPredicate()) {
3927  // For a UGT comparison, we don't care about any bits that
3928  // correspond to the trailing ones of the comparand. The value of these
3929  // bits doesn't impact the outcome of the comparison, because any value
3930  // greater than the RHS must differ in a bit higher than these due to carry.
3931  case ICmpInst::ICMP_UGT:
3932  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
3933 
3934  // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3935  // Any value less than the RHS must differ in a higher bit because of carries.
3936  case ICmpInst::ICMP_ULT:
3937  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
3938 
3939  default:
3940  return APInt::getAllOnesValue(BitWidth);
3941  }
3942 }
3943 
3944 /// Check if the order of \p Op0 and \p Op1 as operands in an ICmpInst
3945 /// should be swapped.
3946 /// The decision is based on how many times these two operands are reused
3947 /// as subtract operands and their positions in those instructions.
3948 /// The rationale is that several architectures use the same instruction for
3949 /// both subtract and cmp. Thus, it is better if the order of those operands
3950 /// match.
3951 /// \return true if Op0 and Op1 should be swapped.
3952 static bool swapMayExposeCSEOpportunities(const Value *Op0, const Value *Op1) {
3953  // Filter out pointer values as those cannot appear directly in subtract.
3954  // FIXME: we may want to go through inttoptrs or bitcasts.
3955  if (Op0->getType()->isPointerTy())
3956  return false;
3957  // If a subtract already has the same operands as a compare, swapping would be
3958  // bad. If a subtract has the same operands as a compare but in reverse order,
3959  // then swapping is good.
3960  int GoodToSwap = 0;
3961  for (const User *U : Op0->users()) {
3962  if (match(U, m_Sub(m_Specific(Op1), m_Specific(Op0))))
3963  GoodToSwap++;
3964  else if (match(U, m_Sub(m_Specific(Op0), m_Specific(Op1))))
3965  GoodToSwap--;
3966  }
3967  return GoodToSwap > 0;
3968 }
3969 
3970 /// Check that one use is in the same block as the definition and all
3971 /// other uses are in blocks dominated by a given block.
3972 ///
3973 /// \param DI Definition
3974 /// \param UI Use
3975 /// \param DB Block that must dominate all uses of \p DI outside
3976 /// the parent block
3977 /// \return true when \p UI is the only use of \p DI in the parent block
3978 /// and all other uses of \p DI are in blocks dominated by \p DB.
3979 ///
3981  const Instruction *UI,
3982  const BasicBlock *DB) const {
3983  assert(DI && UI && "Instruction not defined\n");
3984  // Ignore incomplete definitions.
3985  if (!DI->getParent())
3986  return false;
3987  // DI and UI must be in the same block.
3988  if (DI->getParent() != UI->getParent())
3989  return false;
3990  // Protect from self-referencing blocks.
3991  if (DI->getParent() == DB)
3992  return false;
3993  for (const User *U : DI->users()) {
3994  auto *Usr = cast<Instruction>(U);
3995  if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
3996  return false;
3997  }
3998  return true;
3999 }
4000 
4001 /// Return true when the instruction sequence within a block is select-cmp-br.
4002 static bool isChainSelectCmpBranch(const SelectInst *SI) {
4003  const BasicBlock *BB = SI->getParent();
4004  if (!BB)
4005  return false;
4006  auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
4007  if (!BI || BI->getNumSuccessors() != 2)
4008  return false;
4009  auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
4010  if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
4011  return false;
4012  return true;
4013 }
4014 
4015 /// True when a select result is replaced by one of its operands
4016 /// in select-icmp sequence. This will eventually result in the elimination
4017 /// of the select.
4018 ///
4019 /// \param SI Select instruction
4020 /// \param Icmp Compare instruction
4021 /// \param SIOpd Operand that replaces the select
4022 ///
4023 /// Notes:
4024 /// - The replacement is global and requires dominator information
4025 /// - The caller is responsible for the actual replacement
4026 ///
4027 /// Example:
4028 ///
4029 /// entry:
4030 /// %4 = select i1 %3, %C* %0, %C* null
4031 /// %5 = icmp eq %C* %4, null
4032 /// br i1 %5, label %9, label %7
4033 /// ...
4034 /// ; <label>:7 ; preds = %entry
4035 /// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
4036 /// ...
4037 ///
4038 /// can be transformed to
4039 ///
4040 /// %5 = icmp eq %C* %0, null
4041 /// %6 = select i1 %3, i1 %5, i1 true
4042 /// br i1 %6, label %9, label %7
4043 /// ...
4044 /// ; <label>:7 ; preds = %entry
4045 /// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
4046 ///
4047 /// Similar when the first operand of the select is a constant or/and
4048 /// the compare is for not equal rather than equal.
4049 ///
4050 /// NOTE: The function is only called when the select and compare constants
4051 /// are equal, the optimization can work only for EQ predicates. This is not a
4052 /// major restriction since a NE compare should be 'normalized' to an equal
4053 /// compare, which usually happens in the combiner and test case
4054 /// select-cmp-br.ll checks for it.
4056  const ICmpInst *Icmp,
4057  const unsigned SIOpd) {
4058  assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
4059  if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
4060  BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
4061  // The check for the single predecessor is not the best that can be
4062  // done. But it protects efficiently against cases like when SI's
4063  // home block has two successors, Succ and Succ1, and Succ1 predecessor
4064  // of Succ. Then SI can't be replaced by SIOpd because the use that gets
4065  // replaced can be reached on either path. So the uniqueness check
4066  // guarantees that the path all uses of SI (outside SI's parent) are on
4067  // is disjoint from all other paths out of SI. But that information
4068  // is more expensive to compute, and the trade-off here is in favor
4069  // of compile-time. It should also be noticed that we check for a single
4070  // predecessor and not only uniqueness. This to handle the situation when
4071  // Succ and Succ1 points to the same basic block.
4072  if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
4073  NumSel++;
4074  SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
4075  return true;
4076  }
4077  }
4078  return false;
4079 }
4080 
4081 /// Try to fold the comparison based on range information we can get by checking
4082 /// whether bits are known to be zero or one in the inputs.
4083 Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
4084  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4085  Type *Ty = Op0->getType();
4086  ICmpInst::Predicate Pred = I.getPredicate();
4087 
4088  // Get scalar or pointer size.
4089  unsigned BitWidth = Ty->isIntOrIntVectorTy()
4090  ? Ty->getScalarSizeInBits()
4091  : DL.getIndexTypeSizeInBits(Ty->getScalarType());
4092 
4093  if (!BitWidth)
4094  return nullptr;
4095 
4096  KnownBits Op0Known(BitWidth);
4097  KnownBits Op1Known(BitWidth);
4098 
4099  if (SimplifyDemandedBits(&I, 0,
4100  getDemandedBitsLHSMask(I, BitWidth),
4101  Op0Known, 0))
4102  return &I;
4103 
4104  if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4105  Op1Known, 0))
4106  return &I;
4107 
4108  // Given the known and unknown bits, compute a range that the LHS could be
4109  // in. Compute the Min, Max and RHS values based on the known bits. For the
4110  // EQ and NE we use unsigned values.
4111  APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4112  APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4113  if (I.isSigned()) {
4114  computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4115  computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4116  } else {
4117  computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4118  computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4119  }
4120 
4121  // If Min and Max are known to be the same, then SimplifyDemandedBits figured
4122  // out that the LHS or RHS is a constant. Constant fold this now, so that
4123  // code below can assume that Min != Max.
4124  if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4125  return new ICmpInst(Pred, ConstantExpr::getIntegerValue(Ty, Op0Min), Op1);
4126  if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4127  return new ICmpInst(Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Min));
4128 
4129  // Based on the range information we know about the LHS, see if we can
4130  // simplify this comparison. For example, (x&4) < 8 is always true.
4131  switch (Pred) {
4132  default:
4133  llvm_unreachable("Unknown icmp opcode!");
4134  case ICmpInst::ICMP_EQ:
4135  case ICmpInst::ICMP_NE: {
4136  if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4137  return Pred == CmpInst::ICMP_EQ
4138  ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4139  : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4140  }
4141 
4142  // If all bits are known zero except for one, then we know at most one bit
4143  // is set. If the comparison is against zero, then this is a check to see if
4144  // *that* bit is set.
4145  APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4146  if (Op1Known.isZero()) {
4147  // If the LHS is an AND with the same constant, look through it.
4148  Value *LHS = nullptr;
4149  const APInt *LHSC;
4150  if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4151  *LHSC != Op0KnownZeroInverted)
4152  LHS = Op0;
4153 
4154  Value *X;
4155  if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4156  APInt ValToCheck = Op0KnownZeroInverted;
4157  Type *XTy = X->getType();
4158  if (ValToCheck.isPowerOf2()) {
4159  // ((1 << X) & 8) == 0 -> X != 3
4160  // ((1 << X) & 8) != 0 -> X == 3
4161  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4162  auto NewPred = ICmpInst::getInversePredicate(Pred);
4163  return new ICmpInst(NewPred, X, CmpC);
4164  } else if ((++ValToCheck).isPowerOf2()) {
4165  // ((1 << X) & 7) == 0 -> X >= 3
4166  // ((1 << X) & 7) != 0 -> X < 3
4167  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4168  auto NewPred =
4170  return new ICmpInst(NewPred, X, CmpC);
4171  }
4172  }
4173 
4174  // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4175  const APInt *CI;
4176  if (Op0KnownZeroInverted.isOneValue() &&
4177  match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4178  // ((8 >>u X) & 1) == 0 -> X != 3
4179  // ((8 >>u X) & 1) != 0 -> X == 3
4180  unsigned CmpVal = CI->countTrailingZeros();
4181  auto NewPred = ICmpInst::getInversePredicate(Pred);
4182  return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4183  }
4184  }
4185  break;
4186  }
4187  case ICmpInst::ICMP_ULT: {
4188  if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4189  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4190  if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4191  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4192  if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4193  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4194 
4195  const APInt *CmpC;
4196  if (match(Op1, m_APInt(CmpC))) {
4197  // A <u C -> A == C-1 if min(A)+1 == C
4198  if (*CmpC == Op0Min + 1)
4199  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4200  ConstantInt::get(Op1->getType(), *CmpC - 1));
4201  // X <u C --> X == 0, if the number of zero bits in the bottom of X
4202  // exceeds the log2 of C.
4203  if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
4204  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4205  Constant::getNullValue(Op1->getType()));
4206  }
4207  break;
4208  }
4209  case ICmpInst::ICMP_UGT: {
4210  if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4211  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4212  if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4213  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4214  if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4215  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4216 
4217  const APInt *CmpC;
4218  if (match(Op1, m_APInt(CmpC))) {
4219  // A >u C -> A == C+1 if max(a)-1 == C
4220  if (*CmpC == Op0Max - 1)
4221  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4222  ConstantInt::get(Op1->getType(), *CmpC + 1));
4223  // X >u C --> X != 0, if the number of zero bits in the bottom of X
4224  // exceeds the log2 of C.
4225  if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
4226  return new ICmpInst(ICmpInst::ICMP_NE, Op0,
4227  Constant::getNullValue(Op1->getType()));
4228  }
4229  break;
4230  }
4231  case ICmpInst::ICMP_SLT: {
4232  if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4233  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4234  if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4235  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4236  if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4237  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4238  const APInt *CmpC;
4239  if (match(Op1, m_APInt(CmpC))) {
4240  if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4241  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4242  ConstantInt::get(Op1->getType(), *CmpC - 1));
4243  }
4244  break;
4245  }
4246  case ICmpInst::ICMP_SGT: {
4247  if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4248  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4249  if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4250  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4251  if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4252  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4253  const APInt *CmpC;
4254  if (match(Op1, m_APInt(CmpC))) {
4255  if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4256  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4257  ConstantInt::get(Op1->getType(), *CmpC + 1));
4258  }
4259  break;
4260  }
4261  case ICmpInst::ICMP_SGE:
4262  assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
4263  if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4264  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4265  if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4266  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4267  if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
4268  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4269  break;
4270  case ICmpInst::ICMP_SLE:
4271  assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
4272  if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4273  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4274  if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4275  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4276  if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
4277  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4278  break;
4279  case ICmpInst::ICMP_UGE:
4280  assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
4281  if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4282  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4283  if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4284  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4285  if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
4286  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4287  break;
4288  case ICmpInst::ICMP_ULE:
4289  assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
4290  if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4291  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4292  if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4293  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4294  if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
4295  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4296  break;
4297  }
4298 
4299  // Turn a signed comparison into an unsigned one if both operands are known to
4300  // have the same sign.
4301  if (I.isSigned() &&
4302  ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4303  (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4304  return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4305 
4306  return nullptr;
4307 }
4308 
4309 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
4310 /// it into the appropriate icmp lt or icmp gt instruction. This transform
4311 /// allows them to be folded in visitICmpInst.
4313  ICmpInst::Predicate Pred = I.getPredicate();
4314  if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4315  Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4316  return nullptr;
4317 
4318  Value *Op0 = I.getOperand(0);
4319  Value *Op1 = I.getOperand(1);
4320  auto *Op1C = dyn_cast<Constant>(Op1);
4321  if (!Op1C)
4322  return nullptr;
4323 
4324  // Check if the constant operand can be safely incremented/decremented without
4325  // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4326  // the edge cases for us, so we just assert on them. For vectors, we must
4327  // handle the edge cases.
4328  Type *Op1Type = Op1->getType();
4329  bool IsSigned = I.isSigned();
4330  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4331  auto *CI = dyn_cast<ConstantInt>(Op1C);
4332  if (CI) {
4333  // A <= MAX -> TRUE ; A >= MIN -> TRUE
4334  assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
4335  } else if (Op1Type->isVectorTy()) {
4336  // TODO? If the edge cases for vectors were guaranteed to be handled as they
4337  // are for scalar, we could remove the min/max checks. However, to do that,
4338  // we would have to use insertelement/shufflevector to replace edge values.
4339  unsigned NumElts = Op1Type->getVectorNumElements();
4340  for (unsigned i = 0; i != NumElts; ++i) {
4341  Constant *Elt = Op1C->getAggregateElement(i);
4342  if (!Elt)
4343  return nullptr;
4344 
4345  if (isa<UndefValue>(Elt))
4346  continue;
4347 
4348  // Bail out if we can't determine if this constant is min/max or if we
4349  // know that this constant is min/max.
4350  auto *CI = dyn_cast<ConstantInt>(Elt);
4351  if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4352  return nullptr;
4353  }
4354  } else {
4355  // ConstantExpr?
4356  return nullptr;
4357  }
4358 
4359  // Increment or decrement the constant and set the new comparison predicate:
4360  // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4361  Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4363  NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4364  return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4365 }
4366 
4367 /// Integer compare with boolean values can always be turned into bitwise ops.
4369  InstCombiner::BuilderTy &Builder) {
4370  Value *A = I.getOperand(0), *B = I.getOperand(1);
4371  assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
4372 
4373  // A boolean compared to true/false can be simplified to Op0/true/false in
4374  // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
4375  // Cases not handled by InstSimplify are always 'not' of Op0.
4376  if (match(B, m_Zero())) {
4377  switch (I.getPredicate()) {
4378  case CmpInst::ICMP_EQ: // A == 0 -> !A
4379  case CmpInst::ICMP_ULE: // A <=u 0 -> !A
4380  case CmpInst::ICMP_SGE: // A >=s 0 -> !A
4381  return BinaryOperator::CreateNot(A);
4382  default:
4383  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4384  }
4385  } else if (match(B, m_One())) {
4386  switch (I.getPredicate()) {
4387  case CmpInst::ICMP_NE: // A != 1 -> !A
4388  case CmpInst::ICMP_ULT: // A <u 1 -> !A
4389  case CmpInst::ICMP_SGT: // A >s -1 -> !A
4390  return BinaryOperator::CreateNot(A);
4391  default:
4392  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4393  }
4394  }
4395 
4396  switch (I.getPredicate()) {
4397  default:
4398  llvm_unreachable("Invalid icmp instruction!");
4399  case ICmpInst::ICMP_EQ:
4400  // icmp eq i1 A, B -> ~(A ^ B)
4401  return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
4402 
4403  case ICmpInst::ICMP_NE:
4404  // icmp ne i1 A, B -> A ^ B
4405  return BinaryOperator::CreateXor(A, B);
4406 
4407  case ICmpInst::ICMP_UGT:
4408  // icmp ugt -> icmp ult
4409  std::swap(A, B);
4411  case ICmpInst::ICMP_ULT:
4412  // icmp ult i1 A, B -> ~A & B
4413  return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
4414 
4415  case ICmpInst::ICMP_SGT:
4416  // icmp sgt -> icmp slt
4417  std::swap(A, B);
4419  case ICmpInst::ICMP_SLT:
4420  // icmp slt i1 A, B -> A & ~B
4421  return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
4422 
4423  case ICmpInst::ICMP_UGE:
4424  // icmp uge -> icmp ule
4425  std::swap(A, B);
4427  case ICmpInst::ICMP_ULE:
4428  // icmp ule i1 A, B -> ~A | B
4429  return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
4430 
4431  case ICmpInst::ICMP_SGE:
4432  // icmp sge -> icmp sle
4433  std::swap(A, B);
4435  case ICmpInst::ICMP_SLE:
4436  // icmp sle i1 A, B -> A | ~B
4437  return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
4438  }
4439 }
4440 
4442  bool Changed = false;
4443  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4444  unsigned Op0Cplxity = getComplexity(Op0);
4445  unsigned Op1Cplxity = getComplexity(Op1);
4446 
4447  /// Orders the operands of the compare so that they are listed from most
4448  /// complex to least complex. This puts constants before unary operators,
4449  /// before binary operators.
4450  if (Op0Cplxity < Op1Cplxity ||
4451  (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4452  I.swapOperands();
4453  std::swap(Op0, Op1);
4454  Changed = true;
4455  }
4456 
4457  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4458  SQ.getWithInstruction(&I)))
4459  return replaceInstUsesWith(I, V);
4460 
4461  // Comparing -val or val with non-zero is the same as just comparing val
4462  // ie, abs(val) != 0 -> val != 0
4463  if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4464  Value *Cond, *SelectTrue, *SelectFalse;
4465  if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4466  m_Value(SelectFalse)))) {
4467  if (Value *V = dyn_castNegVal(SelectTrue)) {
4468  if (V == SelectFalse)
4469  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4470  }
4471  else if (Value *V = dyn_castNegVal(SelectFalse)) {
4472  if (V == SelectTrue)
4473  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4474  }
4475  }
4476  }
4477 
4478  if (Op0->getType()->isIntOrIntVectorTy(1))
4479  if (Instruction *Res = canonicalizeICmpBool(I, Builder))
4480  return Res;
4481 
4482  if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4483  return NewICmp;
4484 
4485  if (Instruction *Res = foldICmpWithConstant(I))
4486  return Res;
4487 
4488  if (Instruction *Res = foldICmpUsingKnownBits(I))
4489  return Res;
4490 
4491  // Test if the ICmpInst instruction is used exclusively by a select as
4492  // part of a minimum or maximum operation. If so, refrain from doing
4493  // any other folding. This helps out other analyses which understand
4494  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4495  // and CodeGen. And in this case, at least one of the comparison
4496  // operands has at least one user besides the compare (the select),
4497  // which would often largely negate the benefit of folding anyway.
4498  //
4499  // Do the same for the other patterns recognized by matchSelectPattern.
4500  if (I.hasOneUse())
4501  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4502  Value *A, *B;
4503  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4504  if (SPR.Flavor != SPF_UNKNOWN)
4505  return nullptr;
4506  }
4507 
4508  // Do this after checking for min/max to prevent infinite looping.
4509  if (Instruction *Res = foldICmpWithZero(I))
4510  return Res;
4511 
4512  // FIXME: We only do this after checking for min/max to prevent infinite
4513  // looping caused by a reverse canonicalization of these patterns for min/max.
4514  // FIXME: The organization of folds is a mess. These would naturally go into
4515  // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4516  // down here after the min/max restriction.
4517  ICmpInst::Predicate Pred = I.getPredicate();
4518  const APInt *C;
4519  if (match(Op1, m_APInt(C))) {
4520  // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4521  if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4522  Constant *Zero = Constant::getNullValue(Op0->getType());
4523  return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4524  }
4525 
4526  // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4527  if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4528  Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4529  return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4530  }
4531  }
4532 
4533  if (Instruction *Res = foldICmpInstWithConstant(I))
4534  return Res;
4535 
4536  if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4537  return Res;
4538 
4539  // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4540  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4541  if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4542  return NI;
4543  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4544  if (Instruction *NI = foldGEPICmp(GEP, Op0,
4546  return NI;
4547 
4548  // Try to optimize equality comparisons against alloca-based pointers.
4549  if (Op0->getType()->isPointerTy() && I.isEquality()) {
4550  assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
4551  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4552  if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4553  return New;
4554  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4555  if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4556  return New;
4557  }
4558 
4559  // Zero-equality and sign-bit checks are preserved through sitofp + bitcast.
4560  Value *X;
4561  if (match(Op0, m_BitCast(m_SIToFP(m_Value(X))))) {
4562  // icmp eq (bitcast (sitofp X)), 0 --> icmp eq X, 0
4563  // icmp ne (bitcast (sitofp X)), 0 --> icmp ne X, 0
4564  // icmp slt (bitcast (sitofp X)), 0 --> icmp slt X, 0
4565  // icmp sgt (bitcast (sitofp X)), 0 --> icmp sgt X, 0
4566  if ((Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_SLT ||
4567  Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT) &&
4568  match(Op1, m_Zero()))
4569  return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
4570 
4571  // icmp slt (bitcast (sitofp X)), 1 --> icmp slt X, 1
4572  if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_One()))
4573  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), 1));
4574 
4575  // icmp sgt (bitcast (sitofp X)), -1 --> icmp sgt X, -1
4576  if (Pred == ICmpInst::ICMP_SGT && match(Op1, m_AllOnes()))
4577  return new ICmpInst(Pred, X, ConstantInt::getAllOnesValue(X->getType()));
4578  }
4579 
4580  // Zero-equality checks are preserved through unsigned floating-point casts:
4581  // icmp eq (bitcast (uitofp X)), 0 --> icmp eq X, 0
4582  // icmp ne (bitcast (uitofp X)), 0 --> icmp ne X, 0
4583  if (match(Op0, m_BitCast(m_UIToFP(m_Value(X)))))
4584  if (I.isEquality() && match(Op1, m_Zero()))
4585  return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
4586 
4587  // Test to see if the operands of the icmp are casted versions of other
4588  // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4589  // now.
4590  if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4591  if (Op0->getType()->isPointerTy() &&
4592  (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4593  // We keep moving the cast from the left operand over to the right
4594  // operand, where it can often be eliminated completely.
4595  Op0 = CI->getOperand(0);
4596 
4597  // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4598  // so eliminate it as well.
4599  if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4600  Op1 = CI2->getOperand(0);
4601 
4602  // If Op1 is a constant, we can fold the cast into the constant.
4603  if (Op0->getType() != Op1->getType()) {
4604  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4605  Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4606  } else {
4607  // Otherwise, cast the RHS right before the icmp
4608  Op1 = Builder.CreateBitCast(Op1, Op0->getType());
4609  }
4610  }
4611  return new ICmpInst(I.getPredicate(), Op0, Op1);
4612  }
4613  }
4614 
4615  if (isa<CastInst>(Op0)) {
4616  // Handle the special case of: icmp (cast bool to X), <cst>
4617  // This comes up when you have code like
4618  // int X = A < B;
4619  // if (X) ...
4620  // For generality, we handle any zero-extension of any operand comparison
4621  // with a constant or another cast from the same type.
4622  if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4623  if (Instruction *R = foldICmpWithCastAndCast(I))
4624  return R;
4625  }
4626 
4627  if (Instruction *Res = foldICmpBinOp(I))
4628  return Res;
4629 
4630  if (Instruction *Res = foldICmpWithMinMax(I))
4631  return Res;
4632 
4633  {
4634  Value *A, *B;
4635  // Transform (A & ~B) == 0 --> (A & B) != 0
4636  // and (A & ~B) != 0 --> (A & B) == 0
4637  // if A is a power of 2.
4638  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4639  match(Op1, m_Zero()) &&
4640  isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
4641  return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
4642  Op1);
4643 
4644  // ~X < ~Y --> Y < X
4645  // ~X < C --> X > ~C
4646  if (match(Op0, m_Not(m_Value(A)))) {
4647  if (match(Op1, m_Not(m_Value(B))))
4648  return new ICmpInst(I.getPredicate(), B, A);
4649 
4650  const APInt *C;
4651  if (match(Op1, m_APInt(C)))
4652  return new ICmpInst(I.getSwappedPredicate(), A,
4653  ConstantInt::get(Op1->getType(), ~(*C)));
4654  }
4655 
4656  Instruction *AddI = nullptr;
4657  if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4658  m_Instruction(AddI))) &&
4659  isa<IntegerType>(A->getType())) {
4660  Value *Result;
4661  Constant *Overflow;
4662  if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4663  Overflow)) {
4664  replaceInstUsesWith(*AddI, Result);
4665  return replaceInstUsesWith(I, Overflow);
4666  }
4667  }
4668 
4669  // (zext a) * (zext b) --> llvm.umul.with.overflow.
4670  if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4671  if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4672  return R;
4673  }
4674  if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4675  if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4676  return R;
4677  }
4678  }
4679 
4680  if (Instruction *Res = foldICmpEquality(I))
4681  return Res;
4682 
4683  // The 'cmpxchg' instruction returns an aggregate containing the old value and
4684  // an i1 which indicates whether or not we successfully did the swap.
4685  //
4686  // Replace comparisons between the old value and the expected value with the
4687  // indicator that 'cmpxchg' returns.
4688  //
4689  // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4690  // spuriously fail. In those cases, the old value may equal the expected
4691  // value but it is possible for the swap to not occur.
4692  if (I.getPredicate() == ICmpInst::ICMP_EQ)
4693  if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4694  if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4695  if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4696  !ACXI->isWeak())
4697  return ExtractValueInst::Create(ACXI, 1);
4698 
4699  {
4700  Value *X; ConstantInt *Cst;
4701  // icmp X+Cst, X
4702  if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4703  return foldICmpAddOpConst(X, Cst, I.getPredicate());
4704 
4705  // icmp X, X+Cst
4706  if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4707  return foldICmpAddOpConst(X, Cst, I.getSwappedPredicate());
4708  }
4709  return Changed ? &I : nullptr;
4710 }
4711 
4712 /// Fold fcmp ([us]itofp x, cst) if possible.
4713 Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4714  Constant *RHSC) {
4715  if (!isa<ConstantFP>(RHSC)) return nullptr;
4716  const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4717 
4718  // Get the width of the mantissa. We don't want to hack on conversions that
4719  // might lose information from the integer, e.g. "i64 -> float"
4720  int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4721  if (MantissaWidth == -1) return nullptr; // Unknown.
4722 
4723  IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4724 
4725  bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4726 
4727  if (I.isEquality()) {
4729  bool IsExact = false;
4730  APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4731  RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4732 
4733  // If the floating point constant isn't an integer value, we know if we will
4734  // ever compare equal / not equal to it.
4735  if (!IsExact) {
4736  // TODO: Can never be -0.0 and other non-representable values
4737  APFloat RHSRoundInt(RHS);
4739  if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4740  if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4741  return replaceInstUsesWith(I, Builder.getFalse());
4742 
4744  return replaceInstUsesWith(I, Builder.getTrue());
4745  }
4746  }
4747 
4748  // TODO: If the constant is exactly representable, is it always OK to do
4749  // equality compares as integer?
4750  }
4751 
4752  // Check to see that the input is converted from an integer type that is small
4753  // enough that preserves all bits. TODO: check here for "known" sign bits.
4754  // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4755  unsigned InputSize = IntTy->getScalarSizeInBits();
4756 
4757  // Following test does NOT adjust InputSize downwards for signed inputs,
4758  // because the most negative value still requires all the mantissa bits
4759  // to distinguish it from one less than that value.
4760  if ((int)InputSize > MantissaWidth) {
4761  // Conversion would lose accuracy. Check if loss can impact comparison.
4762  int Exp = ilogb(RHS);
4763  if (Exp == APFloat::IEK_Inf) {
4764  int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4765  if (MaxExponent < (int)InputSize - !LHSUnsigned)
4766  // Conversion could create infinity.
4767  return nullptr;
4768  } else {
4769  // Note that if RHS is zero or NaN, then Exp is negative
4770  // and first condition is trivially false.
4771  if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4772  // Conversion could affect comparison.
4773  return nullptr;
4774  }
4775  }
4776 
4777  // Otherwise, we can potentially simplify the comparison. We know that it
4778  // will always come through as an integer value and we know the constant is
4779  // not a NAN (it would have been previously simplified).
4780  assert(!RHS.isNaN() && "NaN comparison not already folded!");
4781 
4782  ICmpInst::Predicate Pred;
4783  switch (I.getPredicate()) {
4784  default: llvm_unreachable("Unexpected predicate!");
4785  case FCmpInst::FCMP_UEQ:
4786  case FCmpInst::FCMP_OEQ:
4787  Pred = ICmpInst::ICMP_EQ;
4788  break;
4789  case FCmpInst::FCMP_UGT:
4790  case FCmpInst::FCMP_OGT:
4791  Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4792  break;
4793  case FCmpInst::FCMP_UGE:
4794  case FCmpInst::FCMP_OGE:
4795  Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4796  break;
4797  case FCmpInst::FCMP_ULT:
4798  case FCmpInst::FCMP_OLT:
4799  Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4800  break;
4801  case FCmpInst::FCMP_ULE:
4802  case FCmpInst::FCMP_OLE:
4803  Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4804  break;
4805  case FCmpInst::FCMP_UNE:
4806  case FCmpInst::FCMP_ONE:
4807  Pred = ICmpInst::ICMP_NE;
4808  break;
4809  case FCmpInst::FCMP_ORD:
4810  return replaceInstUsesWith(I, Builder.getTrue());
4811  case FCmpInst::FCMP_UNO:
4812  return replaceInstUsesWith(I, Builder.getFalse());
4813  }
4814 
4815  // Now we know that the APFloat is a normal number, zero or inf.
4816 
4817  // See if the FP constant is too large for the integer. For example,
4818  // comparing an i8 to 300.0.
4819  unsigned IntWidth = IntTy->getScalarSizeInBits();
4820 
4821  if (!LHSUnsigned) {
4822  // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4823  // and large values.
4824  APFloat SMax(RHS.getSemantics());
4825  SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4827  if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4828  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4829  Pred == ICmpInst::ICMP_SLE)
4830  return replaceInstUsesWith(I, Builder.getTrue());
4831  return replaceInstUsesWith(I, Builder.getFalse());
4832  }
4833  } else {
4834  // If the RHS value is > UnsignedMax, fold the comparison. This handles
4835  // +INF and large values.
4836  APFloat UMax(RHS.getSemantics());
4837  UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4839  if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4840  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4841  Pred == ICmpInst::ICMP_ULE)
4842  return replaceInstUsesWith(I, Builder.getTrue());
4843  return replaceInstUsesWith(I, Builder.getFalse());
4844  }
4845  }
4846 
4847  if (!LHSUnsigned) {
4848  // See if the RHS value is < SignedMin.
4849  APFloat SMin(RHS.getSemantics());
4850  SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4852  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4853  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4854  Pred == ICmpInst::ICMP_SGE)
4855  return replaceInstUsesWith(I, Builder.getTrue());
4856  return replaceInstUsesWith(I, Builder.getFalse());
4857  }
4858  } else {
4859  // See if the RHS value is < UnsignedMin.
4860  APFloat SMin(RHS.getSemantics());
4861  SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4863  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4864  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4865  Pred == ICmpInst::ICMP_UGE)
4866  return replaceInstUsesWith(I, Builder.getTrue());
4867  return replaceInstUsesWith(I, Builder.getFalse());
4868  }
4869  }
4870 
4871  // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4872  // [0, UMAX], but it may still be fractional. See if it is fractional by
4873  // casting the FP value to the integer value and back, checking for equality.
4874  // Don't do this for zero, because -0.0 is not fractional.
4875  Constant *RHSInt = LHSUnsigned
4876  ? ConstantExpr::getFPToUI(RHSC, IntTy)
4877  : ConstantExpr::getFPToSI(RHSC, IntTy);
4878  if (!RHS.isZero()) {
4879  bool Equal = LHSUnsigned
4880  ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4881  : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4882  if (!Equal) {
4883  // If we had a comparison against a fractional value, we have to adjust
4884  // the compare predicate and sometimes the value. RHSC is rounded towards
4885  // zero at this point.
4886  switch (Pred) {
4887  default: llvm_unreachable("Unexpected integer comparison!");
4888  case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4889  return replaceInstUsesWith(I, Builder.getTrue());
4890  case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4891  return replaceInstUsesWith(I, Builder.getFalse());
4892  case ICmpInst::ICMP_ULE:
4893  // (float)int <= 4.4 --> int <= 4
4894  // (float)int <= -4.4 --> false
4895  if (RHS.isNegative())
4896  return replaceInstUsesWith(I, Builder.getFalse());
4897  break;
4898  case ICmpInst::ICMP_SLE:
4899  // (float)int <= 4.4 --> int <= 4
4900  // (float)int <= -4.4 --> int < -4
4901  if (RHS.isNegative())
4902  Pred = ICmpInst::ICMP_SLT;
4903  break;
4904  case ICmpInst::ICMP_ULT:
4905  // (float)int < -4.4 --> false
4906  // (float)int < 4.4 --> int <= 4
4907  if (RHS.isNegative())
4908  return replaceInstUsesWith(I, Builder.getFalse());
4909  Pred = ICmpInst::ICMP_ULE;
4910  break;
4911  case ICmpInst::ICMP_SLT:
4912  // (float)int < -4.4 --> int < -4
4913  // (float)int < 4.4 --> int <= 4
4914  if (!RHS.isNegative())
4915  Pred = ICmpInst::ICMP_SLE;
4916  break;
4917  case ICmpInst::ICMP_UGT:
4918  // (float)int > 4.4 --> int > 4
4919  // (float)int > -4.4 --> true
4920  if (RHS.isNegative())
4921  return replaceInstUsesWith(I, Builder.getTrue());
4922  break;
4923  case ICmpInst::ICMP_SGT:
4924  // (float)int > 4.4 --> int > 4
4925  // (float)int > -4.4 --> int >= -4
4926  if (RHS.isNegative())
4927  Pred = ICmpInst::ICMP_SGE;
4928  break;
4929  case ICmpInst::ICMP_UGE:
4930  // (float)int >= -4.4 --> true
4931  // (float)int >= 4.4 --> int > 4
4932  if (RHS.isNegative())
4933  return replaceInstUsesWith(I, Builder.getTrue());
4934  Pred = ICmpInst::ICMP_UGT;
4935  break;
4936  case ICmpInst::ICMP_SGE:
4937  // (float)int >= -4.4 --> int >= -4
4938  // (float)int >= 4.4 --> int > 4
4939  if (!RHS.isNegative())
4940  Pred = ICmpInst::ICMP_SGT;
4941  break;
4942  }
4943  }
4944  }
4945 
4946  // Lower this FP comparison into an appropriate integer version of the
4947  // comparison.
4948  return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4949 }
4950 
4952  bool Changed = false;
4953 
4954  /// Orders the operands of the compare so that they are listed from most
4955  /// complex to least complex. This puts constants before unary operators,
4956  /// before binary operators.
4957  if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4958  I.swapOperands();
4959  Changed = true;
4960  }
4961 
4962  const CmpInst::Predicate Pred = I.getPredicate();
4963  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4964  if (Value *V = SimplifyFCmpInst(Pred, Op0, Op1, I.getFastMathFlags(),
4965  SQ.getWithInstruction(&I)))
4966  return replaceInstUsesWith(I, V);
4967 
4968  // Simplify 'fcmp pred X, X'
4969  if (Op0 == Op1) {
4970  switch (Pred) {
4971  default: break;
4972  case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4973  case FCmpInst::FCMP_ULT: // True if unordered or less than
4974  case FCmpInst::FCMP_UGT: // True if unordered or greater than
4975  case FCmpInst::FCMP_UNE: // True if unordered or not equal
4976  // Canonicalize these to be 'fcmp uno %X, 0.0'.
4979  return &I;
4980 
4981  case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4982  case FCmpInst::FCMP_OEQ: // True if ordered and equal
4983  case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4984  case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4985  // Canonicalize these to be 'fcmp ord %X, 0.0'.
4988  return &I;
4989  }
4990  }
4991 
4992  // If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
4993  // then canonicalize the operand to 0.0.
4994  if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
4995  if (!match(Op0, m_PosZeroFP()) && isKnownNeverNaN(Op0)) {
4997  return &I;
4998  }
4999  if (!match(Op1, m_PosZeroFP()) && isKnownNeverNaN(Op1)) {
5001  return &I;
5002  }
5003  }
5004 
5005  // Test if the FCmpInst instruction is used exclusively by a select as
5006  // part of a minimum or maximum operation. If so, refrain from doing
5007  // any other folding. This helps out other analyses which understand
5008  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
5009  // and CodeGen. And in this case, at least one of the comparison
5010  // operands has at least one user besides the compare (the select),
5011  // which would often largely negate the benefit of folding anyway.
5012  if (I.hasOneUse())
5013  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
5014  Value *A, *B;
5015  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
5016  if (SPR.Flavor != SPF_UNKNOWN)
5017  return nullptr;
5018  }
5019 
5020  // Handle fcmp with constant RHS
5021  if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
5022  if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
5023  switch (LHSI->getOpcode()) {
5024  case Instruction::FPExt: {
5025  // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
5026  FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
5027  ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
5028  if (!RHSF)
5029  break;
5030 
5031  const fltSemantics *Sem;
5032  // FIXME: This shouldn't be here.
5033  if (LHSExt->getSrcTy()->isHalfTy())
5034  Sem = &APFloat::IEEEhalf();
5035  else if (LHSExt->getSrcTy()->isFloatTy())
5036  Sem = &APFloat::IEEEsingle();
5037  else if (LHSExt->getSrcTy()->isDoubleTy())
5038  Sem = &APFloat::IEEEdouble();
5039  else if (LHSExt->getSrcTy()->isFP128Ty())
5040  Sem = &APFloat::IEEEquad();
5041  else if (LHSExt->getSrcTy()->isX86_FP80Ty())
5042  Sem = &APFloat::x87DoubleExtended();
5043  else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
5044  Sem = &APFloat::PPCDoubleDouble();
5045  else
5046  break;
5047 
5048  bool Lossy;
5049  APFloat F = RHSF->getValueAPF();
5050  F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
5051 
5052  // Avoid lossy conversions and denormals. Zero is a special case
5053  // that's OK to convert.
5054  APFloat Fabs = F;
5055  Fabs.clearSign();
5056  if (!Lossy &&
5057