LLVM  7.0.0svn
InstCombineCompares.cpp
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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) && dyn_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 /// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2461 /// where X is some kind of instruction.
2462 Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2463  const APInt *C;
2464  if (!match(Cmp.getOperand(1), m_APInt(C)))
2465  return nullptr;
2466 
2467  if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
2468  switch (BO->getOpcode()) {
2469  case Instruction::Xor:
2470  if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
2471  return I;
2472  break;
2473  case Instruction::And:
2474  if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
2475  return I;
2476  break;
2477  case Instruction::Or:
2478  if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
2479  return I;
2480  break;
2481  case Instruction::Mul:
2482  if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
2483  return I;
2484  break;
2485  case Instruction::Shl:
2486  if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
2487  return I;
2488  break;
2489  case Instruction::LShr:
2490  case Instruction::AShr:
2491  if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
2492  return I;
2493  break;
2494  case Instruction::UDiv:
2495  if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
2496  return I;
2498  case Instruction::SDiv:
2499  if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
2500  return I;
2501  break;
2502  case Instruction::Sub:
2503  if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
2504  return I;
2505  break;
2506  case Instruction::Add:
2507  if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
2508  return I;
2509  break;
2510  default:
2511  break;
2512  }
2513  // TODO: These folds could be refactored to be part of the above calls.
2514  if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
2515  return I;
2516  }
2517 
2518  // Match against CmpInst LHS being instructions other than binary operators.
2519 
2520  if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
2521  // For now, we only support constant integers while folding the
2522  // ICMP(SELECT)) pattern. We can extend this to support vector of integers
2523  // similar to the cases handled by binary ops above.
2524  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
2525  if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
2526  return I;
2527  }
2528 
2529  if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
2530  if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
2531  return I;
2532  }
2533 
2534  if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, *C))
2535  return I;
2536 
2537  return nullptr;
2538 }
2539 
2540 /// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2541 /// icmp eq/ne BO, C.
2542 Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2543  BinaryOperator *BO,
2544  const APInt &C) {
2545  // TODO: Some of these folds could work with arbitrary constants, but this
2546  // function is limited to scalar and vector splat constants.
2547  if (!Cmp.isEquality())
2548  return nullptr;
2549 
2550  ICmpInst::Predicate Pred = Cmp.getPredicate();
2551  bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2552  Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2553  Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2554 
2555  switch (BO->getOpcode()) {
2556  case Instruction::SRem:
2557  // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2558  if (C.isNullValue() && BO->hasOneUse()) {
2559  const APInt *BOC;
2560  if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2561  Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
2562  return new ICmpInst(Pred, NewRem,
2564  }
2565  }
2566  break;
2567  case Instruction::Add: {
2568  // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2569  const APInt *BOC;
2570  if (match(BOp1, m_APInt(BOC))) {
2571  if (BO->hasOneUse()) {
2572  Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2573  return new ICmpInst(Pred, BOp0, SubC);
2574  }
2575  } else if (C.isNullValue()) {
2576  // Replace ((add A, B) != 0) with (A != -B) if A or B is
2577  // efficiently invertible, or if the add has just this one use.
2578  if (Value *NegVal = dyn_castNegVal(BOp1))
2579  return new ICmpInst(Pred, BOp0, NegVal);
2580  if (Value *NegVal = dyn_castNegVal(BOp0))
2581  return new ICmpInst(Pred, NegVal, BOp1);
2582  if (BO->hasOneUse()) {
2583  Value *Neg = Builder.CreateNeg(BOp1);
2584  Neg->takeName(BO);
2585  return new ICmpInst(Pred, BOp0, Neg);
2586  }
2587  }
2588  break;
2589  }
2590  case Instruction::Xor:
2591  if (BO->hasOneUse()) {
2592  if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2593  // For the xor case, we can xor two constants together, eliminating
2594  // the explicit xor.
2595  return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2596  } else if (C.isNullValue()) {
2597  // Replace ((xor A, B) != 0) with (A != B)
2598  return new ICmpInst(Pred, BOp0, BOp1);
2599  }
2600  }
2601  break;
2602  case Instruction::Sub:
2603  if (BO->hasOneUse()) {
2604  const APInt *BOC;
2605  if (match(BOp0, m_APInt(BOC))) {
2606  // Replace ((sub BOC, B) != C) with (B != BOC-C).
2607  Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2608  return new ICmpInst(Pred, BOp1, SubC);
2609  } else if (C.isNullValue()) {
2610  // Replace ((sub A, B) != 0) with (A != B).
2611  return new ICmpInst(Pred, BOp0, BOp1);
2612  }
2613  }
2614  break;
2615  case Instruction::Or: {
2616  const APInt *BOC;
2617  if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2618  // Comparing if all bits outside of a constant mask are set?
2619  // Replace (X | C) == -1 with (X & ~C) == ~C.
2620  // This removes the -1 constant.
2621  Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2622  Value *And = Builder.CreateAnd(BOp0, NotBOC);
2623  return new ICmpInst(Pred, And, NotBOC);
2624  }
2625  break;
2626  }
2627  case Instruction::And: {
2628  const APInt *BOC;
2629  if (match(BOp1, m_APInt(BOC))) {
2630  // If we have ((X & C) == C), turn it into ((X & C) != 0).
2631  if (C == *BOC && C.isPowerOf2())
2632  return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2633  BO, Constant::getNullValue(RHS->getType()));
2634 
2635  // Don't perform the following transforms if the AND has multiple uses
2636  if (!BO->hasOneUse())
2637  break;
2638 
2639  // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2640  if (BOC->isSignMask()) {
2641  Constant *Zero = Constant::getNullValue(BOp0->getType());
2642  auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2643  return new ICmpInst(NewPred, BOp0, Zero);
2644  }
2645 
2646  // ((X & ~7) == 0) --> X < 8
2647  if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
2648  Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2649  auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2650  return new ICmpInst(NewPred, BOp0, NegBOC);
2651  }
2652  }
2653  break;
2654  }
2655  case Instruction::Mul:
2656  if (C.isNullValue() && BO->hasNoSignedWrap()) {
2657  const APInt *BOC;
2658  if (match(BOp1, m_APInt(BOC)) && !BOC->isNullValue()) {
2659  // The trivial case (mul X, 0) is handled by InstSimplify.
2660  // General case : (mul X, C) != 0 iff X != 0
2661  // (mul X, C) == 0 iff X == 0
2662  return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2663  }
2664  }
2665  break;
2666  case Instruction::UDiv:
2667  if (C.isNullValue()) {
2668  // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2669  auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2670  return new ICmpInst(NewPred, BOp1, BOp0);
2671  }
2672  break;
2673  default:
2674  break;
2675  }
2676  return nullptr;
2677 }
2678 
2679 /// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2680 Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2681  const APInt &C) {
2683  if (!II || !Cmp.isEquality())
2684  return nullptr;
2685 
2686  // Handle icmp {eq|ne} <intrinsic>, Constant.
2687  Type *Ty = II->getType();
2688  switch (II->getIntrinsicID()) {
2689  case Intrinsic::bswap:
2690  Worklist.Add(II);
2691  Cmp.setOperand(0, II->getArgOperand(0));
2692  Cmp.setOperand(1, ConstantInt::get(Ty, C.byteSwap()));
2693  return &Cmp;
2694 
2695  case Intrinsic::ctlz:
2696  case Intrinsic::cttz:
2697  // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2698  if (C == C.getBitWidth()) {
2699  Worklist.Add(II);
2700  Cmp.setOperand(0, II->getArgOperand(0));
2702  return &Cmp;
2703  }
2704  break;
2705 
2706  case Intrinsic::ctpop: {
2707  // popcount(A) == 0 -> A == 0 and likewise for !=
2708  // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2709  bool IsZero = C.isNullValue();
2710  if (IsZero || C == C.getBitWidth()) {
2711  Worklist.Add(II);
2712  Cmp.setOperand(0, II->getArgOperand(0));
2713  auto *NewOp =
2715  Cmp.setOperand(1, NewOp);
2716  return &Cmp;
2717  }
2718  break;
2719  }
2720  default:
2721  break;
2722  }
2723 
2724  return nullptr;
2725 }
2726 
2727 /// Handle icmp with constant (but not simple integer constant) RHS.
2728 Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2729  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2730  Constant *RHSC = dyn_cast<Constant>(Op1);
2731  Instruction *LHSI = dyn_cast<Instruction>(Op0);
2732  if (!RHSC || !LHSI)
2733  return nullptr;
2734 
2735  switch (LHSI->getOpcode()) {
2736  case Instruction::GetElementPtr:
2737  // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2738  if (RHSC->isNullValue() &&
2739  cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2740  return new ICmpInst(
2741  I.getPredicate(), LHSI->getOperand(0),
2742  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2743  break;
2744  case Instruction::PHI:
2745  // Only fold icmp into the PHI if the phi and icmp are in the same
2746  // block. If in the same block, we're encouraging jump threading. If
2747  // not, we are just pessimizing the code by making an i1 phi.
2748  if (LHSI->getParent() == I.getParent())
2749  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2750  return NV;
2751  break;
2752  case Instruction::Select: {
2753  // If either operand of the select is a constant, we can fold the
2754  // comparison into the select arms, which will cause one to be
2755  // constant folded and the select turned into a bitwise or.
2756  Value *Op1 = nullptr, *Op2 = nullptr;
2757  ConstantInt *CI = nullptr;
2758  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2759  Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2760  CI = dyn_cast<ConstantInt>(Op1);
2761  }
2762  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2763  Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2764  CI = dyn_cast<ConstantInt>(Op2);
2765  }
2766 
2767  // We only want to perform this transformation if it will not lead to
2768  // additional code. This is true if either both sides of the select
2769  // fold to a constant (in which case the icmp is replaced with a select
2770  // which will usually simplify) or this is the only user of the
2771  // select (in which case we are trading a select+icmp for a simpler
2772  // select+icmp) or all uses of the select can be replaced based on
2773  // dominance information ("Global cases").
2774  bool Transform = false;
2775  if (Op1 && Op2)
2776  Transform = true;
2777  else if (Op1 || Op2) {
2778  // Local case
2779  if (LHSI->hasOneUse())
2780  Transform = true;
2781  // Global cases
2782  else if (CI && !CI->isZero())
2783  // When Op1 is constant try replacing select with second operand.
2784  // Otherwise Op2 is constant and try replacing select with first
2785  // operand.
2786  Transform =
2787  replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2788  }
2789  if (Transform) {
2790  if (!Op1)
2791  Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2792  I.getName());
2793  if (!Op2)
2794  Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2795  I.getName());
2796  return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2797  }
2798  break;
2799  }
2800  case Instruction::IntToPtr:
2801  // icmp pred inttoptr(X), null -> icmp pred X, 0
2802  if (RHSC->isNullValue() &&
2803  DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2804  return new ICmpInst(
2805  I.getPredicate(), LHSI->getOperand(0),
2806  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2807  break;
2808 
2809  case Instruction::Load:
2810  // Try to optimize things like "A[i] > 4" to index computations.
2811  if (GetElementPtrInst *GEP =
2812  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2813  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2814  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2815  !cast<LoadInst>(LHSI)->isVolatile())
2816  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2817  return Res;
2818  }
2819  break;
2820  }
2821 
2822  return nullptr;
2823 }
2824 
2825 /// Try to fold icmp (binop), X or icmp X, (binop).
2826 /// TODO: A large part of this logic is duplicated in InstSimplify's
2827 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
2828 /// duplication.
2829 Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2830  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2831 
2832  // Special logic for binary operators.
2833  BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2834  BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2835  if (!BO0 && !BO1)
2836  return nullptr;
2837 
2838  const CmpInst::Predicate Pred = I.getPredicate();
2839  bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2840  if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2841  NoOp0WrapProblem =
2842  ICmpInst::isEquality(Pred) ||
2843  (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2844  (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2845  if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2846  NoOp1WrapProblem =
2847  ICmpInst::isEquality(Pred) ||
2848  (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2849  (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2850 
2851  // Analyze the case when either Op0 or Op1 is an add instruction.
2852  // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2853  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2854  if (BO0 && BO0->getOpcode() == Instruction::Add) {
2855  A = BO0->getOperand(0);
2856  B = BO0->getOperand(1);
2857  }
2858  if (BO1 && BO1->getOpcode() == Instruction::Add) {
2859  C = BO1->getOperand(0);
2860  D = BO1->getOperand(1);
2861  }
2862 
2863  // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2864  if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2865  return new ICmpInst(Pred, A == Op1 ? B : A,
2866  Constant::getNullValue(Op1->getType()));
2867 
2868  // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2869  if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2870  return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2871  C == Op0 ? D : C);
2872 
2873  // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2874  if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2875  NoOp1WrapProblem &&
2876  // Try not to increase register pressure.
2877  BO0->hasOneUse() && BO1->hasOneUse()) {
2878  // Determine Y and Z in the form icmp (X+Y), (X+Z).
2879  Value *Y, *Z;
2880  if (A == C) {
2881  // C + B == C + D -> B == D
2882  Y = B;
2883  Z = D;
2884  } else if (A == D) {
2885  // D + B == C + D -> B == C
2886  Y = B;
2887  Z = C;
2888  } else if (B == C) {
2889  // A + C == C + D -> A == D
2890  Y = A;
2891  Z = D;
2892  } else {
2893  assert(B == D);
2894  // A + D == C + D -> A == C
2895  Y = A;
2896  Z = C;
2897  }
2898  return new ICmpInst(Pred, Y, Z);
2899  }
2900 
2901  // icmp slt (X + -1), Y -> icmp sle X, Y
2902  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2903  match(B, m_AllOnes()))
2904  return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2905 
2906  // icmp sge (X + -1), Y -> icmp sgt X, Y
2907  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2908  match(B, m_AllOnes()))
2909  return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2910 
2911  // icmp sle (X + 1), Y -> icmp slt X, Y
2912  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2913  return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2914 
2915  // icmp sgt (X + 1), Y -> icmp sge X, Y
2916  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2917  return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2918 
2919  // icmp sgt X, (Y + -1) -> icmp sge X, Y
2920  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2921  match(D, m_AllOnes()))
2922  return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2923 
2924  // icmp sle X, (Y + -1) -> icmp slt X, Y
2925  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2926  match(D, m_AllOnes()))
2927  return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2928 
2929  // icmp sge X, (Y + 1) -> icmp sgt X, Y
2930  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
2931  return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
2932 
2933  // icmp slt X, (Y + 1) -> icmp sle X, Y
2934  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
2935  return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
2936 
2937  // TODO: The subtraction-related identities shown below also hold, but
2938  // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
2939  // wouldn't happen even if they were implemented.
2940  //
2941  // icmp ult (X - 1), Y -> icmp ule X, Y
2942  // icmp uge (X - 1), Y -> icmp ugt X, Y
2943  // icmp ugt X, (Y - 1) -> icmp uge X, Y
2944  // icmp ule X, (Y - 1) -> icmp ult X, Y
2945 
2946  // icmp ule (X + 1), Y -> icmp ult X, Y
2947  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
2948  return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
2949 
2950  // icmp ugt (X + 1), Y -> icmp uge X, Y
2951  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
2952  return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
2953 
2954  // icmp uge X, (Y + 1) -> icmp ugt X, Y
2955  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
2956  return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
2957 
2958  // icmp ult X, (Y + 1) -> icmp ule X, Y
2959  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
2960  return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
2961 
2962  // if C1 has greater magnitude than C2:
2963  // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
2964  // s.t. C3 = C1 - C2
2965  //
2966  // if C2 has greater magnitude than C1:
2967  // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
2968  // s.t. C3 = C2 - C1
2969  if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
2970  (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
2971  if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
2972  if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
2973  const APInt &AP1 = C1->getValue();
2974  const APInt &AP2 = C2->getValue();
2975  if (AP1.isNegative() == AP2.isNegative()) {
2976  APInt AP1Abs = C1->getValue().abs();
2977  APInt AP2Abs = C2->getValue().abs();
2978  if (AP1Abs.uge(AP2Abs)) {
2979  ConstantInt *C3 = Builder.getInt(AP1 - AP2);
2980  Value *NewAdd = Builder.CreateNSWAdd(A, C3);
2981  return new ICmpInst(Pred, NewAdd, C);
2982  } else {
2983  ConstantInt *C3 = Builder.getInt(AP2 - AP1);
2984  Value *NewAdd = Builder.CreateNSWAdd(C, C3);
2985  return new ICmpInst(Pred, A, NewAdd);
2986  }
2987  }
2988  }
2989 
2990  // Analyze the case when either Op0 or Op1 is a sub instruction.
2991  // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
2992  A = nullptr;
2993  B = nullptr;
2994  C = nullptr;
2995  D = nullptr;
2996  if (BO0 && BO0->getOpcode() == Instruction::Sub) {
2997  A = BO0->getOperand(0);
2998  B = BO0->getOperand(1);
2999  }
3000  if (BO1 && BO1->getOpcode() == Instruction::Sub) {
3001  C = BO1->getOperand(0);
3002  D = BO1->getOperand(1);
3003  }
3004 
3005  // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
3006  if (A == Op1 && NoOp0WrapProblem)
3007  return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
3008 
3009  // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
3010  if (C == Op0 && NoOp1WrapProblem)
3011  return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
3012 
3013  // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
3014  if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
3015  // Try not to increase register pressure.
3016  BO0->hasOneUse() && BO1->hasOneUse())
3017  return new ICmpInst(Pred, A, C);
3018 
3019  // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
3020  if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
3021  // Try not to increase register pressure.
3022  BO0->hasOneUse() && BO1->hasOneUse())
3023  return new ICmpInst(Pred, D, B);
3024 
3025  // icmp (0-X) < cst --> x > -cst
3026  if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
3027  Value *X;
3028  if (match(BO0, m_Neg(m_Value(X))))
3029  if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3030  if (!RHSC->isMinValue(/*isSigned=*/true))
3031  return new ICmpInst(I.getSwappedPredicate(), X,
3032  ConstantExpr::getNeg(RHSC));
3033  }
3034 
3035  BinaryOperator *SRem = nullptr;
3036  // icmp (srem X, Y), Y
3037  if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
3038  SRem = BO0;
3039  // icmp Y, (srem X, Y)
3040  else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3041  Op0 == BO1->getOperand(1))
3042  SRem = BO1;
3043  if (SRem) {
3044  // We don't check hasOneUse to avoid increasing register pressure because
3045  // the value we use is the same value this instruction was already using.
3046  switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3047  default:
3048  break;
3049  case ICmpInst::ICMP_EQ:
3050  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3051  case ICmpInst::ICMP_NE:
3052  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3053  case ICmpInst::ICMP_SGT:
3054  case ICmpInst::ICMP_SGE:
3055  return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3057  case ICmpInst::ICMP_SLT:
3058  case ICmpInst::ICMP_SLE:
3059  return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3060  Constant::getNullValue(SRem->getType()));
3061  }
3062  }
3063 
3064  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3065  BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3066  switch (BO0->getOpcode()) {
3067  default:
3068  break;
3069  case Instruction::Add:
3070  case Instruction::Sub:
3071  case Instruction::Xor: {
3072  if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3073  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3074 
3075  const APInt *C;
3076  if (match(BO0->getOperand(1), m_APInt(C))) {
3077  // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3078  if (C->isSignMask()) {
3079  ICmpInst::Predicate NewPred =
3081  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3082  }
3083 
3084  // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
3085  if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
3086  ICmpInst::Predicate NewPred =
3088  NewPred = I.getSwappedPredicate(NewPred);
3089  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3090  }
3091  }
3092  break;
3093  }
3094  case Instruction::Mul: {
3095  if (!I.isEquality())
3096  break;
3097 
3098  const APInt *C;
3099  if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
3100  !C->isOneValue()) {
3101  // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
3102  // Mask = -1 >> count-trailing-zeros(C).
3103  if (unsigned TZs = C->countTrailingZeros()) {
3105  BO0->getType(),
3106  APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
3107  Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
3108  Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
3109  return new ICmpInst(Pred, And1, And2);
3110  }
3111  // If there are no trailing zeros in the multiplier, just eliminate
3112  // the multiplies (no masking is needed):
3113  // icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
3114  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3115  }
3116  break;
3117  }
3118  case Instruction::UDiv:
3119  case Instruction::LShr:
3120  if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
3121  break;
3122  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3123 
3124  case Instruction::SDiv:
3125  if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
3126  break;
3127  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3128 
3129  case Instruction::AShr:
3130  if (!BO0->isExact() || !BO1->isExact())
3131  break;
3132  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3133 
3134  case Instruction::Shl: {
3135  bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3136  bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3137  if (!NUW && !NSW)
3138  break;
3139  if (!NSW && I.isSigned())
3140  break;
3141  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3142  }
3143  }
3144  }
3145 
3146  if (BO0) {
3147  // Transform A & (L - 1) `ult` L --> L != 0
3148  auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3149  auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
3150 
3151  if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
3152  auto *Zero = Constant::getNullValue(BO0->getType());
3153  return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3154  }
3155  }
3156 
3157  return nullptr;
3158 }
3159 
3160 /// Fold icmp Pred min|max(X, Y), X.
3162  ICmpInst::Predicate Pred = Cmp.getPredicate();
3163  Value *Op0 = Cmp.getOperand(0);
3164  Value *X = Cmp.getOperand(1);
3165 
3166  // Canonicalize minimum or maximum operand to LHS of the icmp.
3167  if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3168  match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3169  match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3170  match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3171  std::swap(Op0, X);
3172  Pred = Cmp.getSwappedPredicate();
3173  }
3174 
3175  Value *Y;
3176  if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3177  // smin(X, Y) == X --> X s<= Y
3178  // smin(X, Y) s>= X --> X s<= Y
3179  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3180  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3181 
3182  // smin(X, Y) != X --> X s> Y
3183  // smin(X, Y) s< X --> X s> Y
3184  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3185  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3186 
3187  // These cases should be handled in InstSimplify:
3188  // smin(X, Y) s<= X --> true
3189  // smin(X, Y) s> X --> false
3190  return nullptr;
3191  }
3192 
3193  if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3194  // smax(X, Y) == X --> X s>= Y
3195  // smax(X, Y) s<= X --> X s>= Y
3196  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3197  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3198 
3199  // smax(X, Y) != X --> X s< Y
3200  // smax(X, Y) s> X --> X s< Y
3201  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3202  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3203 
3204  // These cases should be handled in InstSimplify:
3205  // smax(X, Y) s>= X --> true
3206  // smax(X, Y) s< X --> false
3207  return nullptr;
3208  }
3209 
3210  if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3211  // umin(X, Y) == X --> X u<= Y
3212  // umin(X, Y) u>= X --> X u<= Y
3213  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3214  return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3215 
3216  // umin(X, Y) != X --> X u> Y
3217  // umin(X, Y) u< X --> X u> Y
3218  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3219  return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3220 
3221  // These cases should be handled in InstSimplify:
3222  // umin(X, Y) u<= X --> true
3223  // umin(X, Y) u> X --> false
3224  return nullptr;
3225  }
3226 
3227  if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3228  // umax(X, Y) == X --> X u>= Y
3229  // umax(X, Y) u<= X --> X u>= Y
3230  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3231  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3232 
3233  // umax(X, Y) != X --> X u< Y
3234  // umax(X, Y) u> X --> X u< Y
3235  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3236  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3237 
3238  // These cases should be handled in InstSimplify:
3239  // umax(X, Y) u>= X --> true
3240  // umax(X, Y) u< X --> false
3241  return nullptr;
3242  }
3243 
3244  return nullptr;
3245 }
3246 
3247 Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3248  if (!I.isEquality())
3249  return nullptr;
3250 
3251  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3252  const CmpInst::Predicate Pred = I.getPredicate();
3253  Value *A, *B, *C, *D;
3254  if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3255  if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3256  Value *OtherVal = A == Op1 ? B : A;
3257  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3258  }
3259 
3260  if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3261  // A^c1 == C^c2 --> A == C^(c1^c2)
3262  ConstantInt *C1, *C2;
3263  if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3264  Op1->hasOneUse()) {
3265  Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
3266  Value *Xor = Builder.CreateXor(C, NC);
3267  return new ICmpInst(Pred, A, Xor);
3268  }
3269 
3270  // A^B == A^D -> B == D
3271  if (A == C)
3272  return new ICmpInst(Pred, B, D);
3273  if (A == D)
3274  return new ICmpInst(Pred, B, C);
3275  if (B == C)
3276  return new ICmpInst(Pred, A, D);
3277  if (B == D)
3278  return new ICmpInst(Pred, A, C);
3279  }
3280  }
3281 
3282  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3283  // A == (A^B) -> B == 0
3284  Value *OtherVal = A == Op0 ? B : A;
3285  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3286  }
3287 
3288  // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3289  if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3290  match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3291  Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3292 
3293  if (A == C) {
3294  X = B;
3295  Y = D;
3296  Z = A;
3297  } else if (A == D) {
3298  X = B;
3299  Y = C;
3300  Z = A;
3301  } else if (B == C) {
3302  X = A;
3303  Y = D;
3304  Z = B;
3305  } else if (B == D) {
3306  X = A;
3307  Y = C;
3308  Z = B;
3309  }
3310 
3311  if (X) { // Build (X^Y) & Z
3312  Op1 = Builder.CreateXor(X, Y);
3313  Op1 = Builder.CreateAnd(Op1, Z);
3314  I.setOperand(0, Op1);
3315  I.setOperand(1, Constant::getNullValue(Op1->getType()));
3316  return &I;
3317  }
3318  }
3319 
3320  // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3321  // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3322  ConstantInt *Cst1;
3323  if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3324  match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3325  (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3326  match(Op1, m_ZExt(m_Value(A))))) {
3327  APInt Pow2 = Cst1->getValue() + 1;
3328  if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3329  Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3330  return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
3331  }
3332 
3333  // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3334  // For lshr and ashr pairs.
3335  if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3336  match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3337  (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3338  match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3339  unsigned TypeBits = Cst1->getBitWidth();
3340  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3341  if (ShAmt < TypeBits && ShAmt != 0) {
3342  ICmpInst::Predicate NewPred =
3344  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3345  APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3346  return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
3347  }
3348  }
3349 
3350  // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3351  if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3352  match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3353  unsigned TypeBits = Cst1->getBitWidth();
3354  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3355  if (ShAmt < TypeBits && ShAmt != 0) {
3356  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3357  APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3358  Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
3359  I.getName() + ".mask");
3360  return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
3361  }
3362  }
3363 
3364  // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3365  // "icmp (and X, mask), cst"
3366  uint64_t ShAmt = 0;
3367  if (Op0->hasOneUse() &&
3368  match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3369  match(Op1, m_ConstantInt(Cst1)) &&
3370  // Only do this when A has multiple uses. This is most important to do
3371  // when it exposes other optimizations.
3372  !A->hasOneUse()) {
3373  unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3374 
3375  if (ShAmt < ASize) {
3376  APInt MaskV =
3378  MaskV <<= ShAmt;
3379 
3380  APInt CmpV = Cst1->getValue().zext(ASize);
3381  CmpV <<= ShAmt;
3382 
3383  Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
3384  return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
3385  }
3386  }
3387 
3388  // If both operands are byte-swapped or bit-reversed, just compare the
3389  // original values.
3390  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
3391  // and handle more intrinsics.
3392  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
3393  (match(Op0, m_BitReverse(m_Value(A))) &&
3394  match(Op1, m_BitReverse(m_Value(B)))))
3395  return new ICmpInst(Pred, A, B);
3396 
3397  return nullptr;
3398 }
3399 
3400 /// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3401 /// far.
3402 Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3403  const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3404  Value *LHSCIOp = LHSCI->getOperand(0);
3405  Type *SrcTy = LHSCIOp->getType();
3406  Type *DestTy = LHSCI->getType();
3407  Value *RHSCIOp;
3408 
3409  // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3410  // integer type is the same size as the pointer type.
3411  if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3412  DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
3413  Value *RHSOp = nullptr;
3414  if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3415  Value *RHSCIOp = RHSC->getOperand(0);
3416  if (RHSCIOp->getType()->getPointerAddressSpace() ==
3417  LHSCIOp->getType()->getPointerAddressSpace()) {
3418  RHSOp = RHSC->getOperand(0);
3419  // If the pointer types don't match, insert a bitcast.
3420  if (LHSCIOp->getType() != RHSOp->getType())
3421  RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
3422  }
3423  } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3424  RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3425  }
3426 
3427  if (RHSOp)
3428  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3429  }
3430 
3431  // The code below only handles extension cast instructions, so far.
3432  // Enforce this.
3433  if (LHSCI->getOpcode() != Instruction::ZExt &&
3434  LHSCI->getOpcode() != Instruction::SExt)
3435  return nullptr;
3436 
3437  bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3438  bool isSignedCmp = ICmp.isSigned();
3439 
3440  if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3441  // Not an extension from the same type?
3442  RHSCIOp = CI->getOperand(0);
3443  if (RHSCIOp->getType() != LHSCIOp->getType())
3444  return nullptr;
3445 
3446  // If the signedness of the two casts doesn't agree (i.e. one is a sext
3447  // and the other is a zext), then we can't handle this.
3448  if (CI->getOpcode() != LHSCI->getOpcode())
3449  return nullptr;
3450 
3451  // Deal with equality cases early.
3452  if (ICmp.isEquality())
3453  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3454 
3455  // A signed comparison of sign extended values simplifies into a
3456  // signed comparison.
3457  if (isSignedCmp && isSignedExt)
3458  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3459 
3460  // The other three cases all fold into an unsigned comparison.
3461  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3462  }
3463 
3464  // If we aren't dealing with a constant on the RHS, exit early.
3465  auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3466  if (!C)
3467  return nullptr;
3468 
3469  // Compute the constant that would happen if we truncated to SrcTy then
3470  // re-extended to DestTy.
3471  Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3472  Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3473 
3474  // If the re-extended constant didn't change...
3475  if (Res2 == C) {
3476  // Deal with equality cases early.
3477  if (ICmp.isEquality())
3478  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3479 
3480  // A signed comparison of sign extended values simplifies into a
3481  // signed comparison.
3482  if (isSignedExt && isSignedCmp)
3483  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3484 
3485  // The other three cases all fold into an unsigned comparison.
3486  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3487  }
3488 
3489  // The re-extended constant changed, partly changed (in the case of a vector),
3490  // or could not be determined to be equal (in the case of a constant
3491  // expression), so the constant cannot be represented in the shorter type.
3492  // Consequently, we cannot emit a simple comparison.
3493  // All the cases that fold to true or false will have already been handled
3494  // by SimplifyICmpInst, so only deal with the tricky case.
3495 
3496  if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3497  return nullptr;
3498 
3499  // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3500  // should have been folded away previously and not enter in here.
3501 
3502  // We're performing an unsigned comp with a sign extended value.
3503  // This is true if the input is >= 0. [aka >s -1]
3504  Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3505  Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3506 
3507  // Finally, return the value computed.
3508  if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3509  return replaceInstUsesWith(ICmp, Result);
3510 
3511  assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
3512  return BinaryOperator::CreateNot(Result);
3513 }
3514 
3515 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3516  Value *RHS, Instruction &OrigI,
3517  Value *&Result, Constant *&Overflow) {
3518  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3519  std::swap(LHS, RHS);
3520 
3521  auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3522  Result = OpResult;
3523  Overflow = OverflowVal;
3524  if (ReuseName)
3525  Result->takeName(&OrigI);
3526  return true;
3527  };
3528 
3529  // If the overflow check was an add followed by a compare, the insertion point
3530  // may be pointing to the compare. We want to insert the new instructions
3531  // before the add in case there are uses of the add between the add and the
3532  // compare.
3533  Builder.SetInsertPoint(&OrigI);
3534 
3535  switch (OCF) {
3536  case OCF_INVALID:
3537  llvm_unreachable("bad overflow check kind!");
3538 
3539  case OCF_UNSIGNED_ADD: {
3540  OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3542  return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
3543  true);
3544 
3546  return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
3547 
3548  // Fall through uadd into sadd
3550  }
3551  case OCF_SIGNED_ADD: {
3552  // X + 0 -> {X, false}
3553  if (match(RHS, m_Zero()))
3554  return SetResult(LHS, Builder.getFalse(), false);
3555 
3556  // We can strength reduce this signed add into a regular add if we can prove
3557  // that it will never overflow.
3558  if (OCF == OCF_SIGNED_ADD)
3559  if (willNotOverflowSignedAdd(LHS, RHS, OrigI))
3560  return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
3561  true);
3562  break;
3563  }
3564 
3565  case OCF_UNSIGNED_SUB:
3566  case OCF_SIGNED_SUB: {
3567  // X - 0 -> {X, false}
3568  if (match(RHS, m_Zero()))
3569  return SetResult(LHS, Builder.getFalse(), false);
3570 
3571  if (OCF == OCF_SIGNED_SUB) {
3572  if (willNotOverflowSignedSub(LHS, RHS, OrigI))
3573  return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
3574  true);
3575  } else {
3576  if (willNotOverflowUnsignedSub(LHS, RHS, OrigI))
3577  return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
3578  true);
3579  }
3580  break;
3581  }
3582 
3583  case OCF_UNSIGNED_MUL: {
3584  OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3586  return SetResult(Builder.CreateNUWMul(LHS, RHS), Builder.getFalse(),
3587  true);
3589  return SetResult(Builder.CreateMul(LHS, RHS), Builder.getTrue(), true);
3591  }
3592  case OCF_SIGNED_MUL:
3593  // X * undef -> undef
3594  if (isa<UndefValue>(RHS))
3595  return SetResult(RHS, UndefValue::get(Builder.getInt1Ty()), false);
3596 
3597  // X * 0 -> {0, false}
3598  if (match(RHS, m_Zero()))
3599  return SetResult(RHS, Builder.getFalse(), false);
3600 
3601  // X * 1 -> {X, false}
3602  if (match(RHS, m_One()))
3603  return SetResult(LHS, Builder.getFalse(), false);
3604 
3605  if (OCF == OCF_SIGNED_MUL)
3606  if (willNotOverflowSignedMul(LHS, RHS, OrigI))
3607  return SetResult(Builder.CreateNSWMul(LHS, RHS), Builder.getFalse(),
3608  true);
3609  break;
3610  }
3611 
3612  return false;
3613 }
3614 
3615 /// \brief Recognize and process idiom involving test for multiplication
3616 /// overflow.
3617 ///
3618 /// The caller has matched a pattern of the form:
3619 /// I = cmp u (mul(zext A, zext B), V
3620 /// The function checks if this is a test for overflow and if so replaces
3621 /// multiplication with call to 'mul.with.overflow' intrinsic.
3622 ///
3623 /// \param I Compare instruction.
3624 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3625 /// the compare instruction. Must be of integer type.
3626 /// \param OtherVal The other argument of compare instruction.
3627 /// \returns Instruction which must replace the compare instruction, NULL if no
3628 /// replacement required.
3630  Value *OtherVal, InstCombiner &IC) {
3631  // Don't bother doing this transformation for pointers, don't do it for
3632  // vectors.
3633  if (!isa<IntegerType>(MulVal->getType()))
3634  return nullptr;
3635 
3636  assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
3637  assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
3638  auto *MulInstr = dyn_cast<Instruction>(MulVal);
3639  if (!MulInstr)
3640  return nullptr;
3641  assert(MulInstr->getOpcode() == Instruction::Mul);
3642 
3643  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3644  *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3645  assert(LHS->getOpcode() == Instruction::ZExt);
3646  assert(RHS->getOpcode() == Instruction::ZExt);
3647  Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3648 
3649  // Calculate type and width of the result produced by mul.with.overflow.
3650  Type *TyA = A->getType(), *TyB = B->getType();
3651  unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3652  WidthB = TyB->getPrimitiveSizeInBits();
3653  unsigned MulWidth;
3654  Type *MulType;
3655  if (WidthB > WidthA) {
3656  MulWidth = WidthB;
3657  MulType = TyB;
3658  } else {
3659  MulWidth = WidthA;
3660  MulType = TyA;
3661  }
3662 
3663  // In order to replace the original mul with a narrower mul.with.overflow,
3664  // all uses must ignore upper bits of the product. The number of used low
3665  // bits must be not greater than the width of mul.with.overflow.
3666  if (MulVal->hasNUsesOrMore(2))
3667  for (User *U : MulVal->users()) {
3668  if (U == &I)
3669  continue;
3670  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3671  // Check if truncation ignores bits above MulWidth.
3672  unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3673  if (TruncWidth > MulWidth)
3674  return nullptr;
3675  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3676  // Check if AND ignores bits above MulWidth.
3677  if (BO->getOpcode() != Instruction::And)
3678  return nullptr;
3679  if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3680  const APInt &CVal = CI->getValue();
3681  if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3682  return nullptr;
3683  } else {
3684  // In this case we could have the operand of the binary operation
3685  // being defined in another block, and performing the replacement
3686  // could break the dominance relation.
3687  return nullptr;
3688  }
3689  } else {
3690  // Other uses prohibit this transformation.
3691  return nullptr;
3692  }
3693  }
3694 
3695  // Recognize patterns
3696  switch (I.getPredicate()) {
3697  case ICmpInst::ICMP_EQ:
3698  case ICmpInst::ICMP_NE:
3699  // Recognize pattern:
3700  // mulval = mul(zext A, zext B)
3701  // cmp eq/neq mulval, zext trunc mulval
3702  if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3703  if (Zext->hasOneUse()) {
3704  Value *ZextArg = Zext->getOperand(0);
3705  if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3706  if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3707  break; //Recognized
3708  }
3709 
3710  // Recognize pattern:
3711  // mulval = mul(zext A, zext B)
3712  // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3713  ConstantInt *CI;
3714  Value *ValToMask;
3715  if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3716  if (ValToMask != MulVal)
3717  return nullptr;
3718  const APInt &CVal = CI->getValue() + 1;
3719  if (CVal.isPowerOf2()) {
3720  unsigned MaskWidth = CVal.logBase2();
3721  if (MaskWidth == MulWidth)
3722  break; // Recognized
3723  }
3724  }
3725  return nullptr;
3726 
3727  case ICmpInst::ICMP_UGT:
3728  // Recognize pattern:
3729  // mulval = mul(zext A, zext B)
3730  // cmp ugt mulval, max
3731  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3732  APInt MaxVal = APInt::getMaxValue(MulWidth);
3733  MaxVal = MaxVal.zext(CI->getBitWidth());
3734  if (MaxVal.eq(CI->getValue()))
3735  break; // Recognized
3736  }
3737  return nullptr;
3738 
3739  case ICmpInst::ICMP_UGE:
3740  // Recognize pattern:
3741  // mulval = mul(zext A, zext B)
3742  // cmp uge mulval, max+1
3743  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3744  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3745  if (MaxVal.eq(CI->getValue()))
3746  break; // Recognized
3747  }
3748  return nullptr;
3749 
3750  case ICmpInst::ICMP_ULE:
3751  // Recognize pattern:
3752  // mulval = mul(zext A, zext B)
3753  // cmp ule mulval, max
3754  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3755  APInt MaxVal = APInt::getMaxValue(MulWidth);
3756  MaxVal = MaxVal.zext(CI->getBitWidth());
3757  if (MaxVal.eq(CI->getValue()))
3758  break; // Recognized
3759  }
3760  return nullptr;
3761 
3762  case ICmpInst::ICMP_ULT:
3763  // Recognize pattern:
3764  // mulval = mul(zext A, zext B)
3765  // cmp ule mulval, max + 1
3766  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3767  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3768  if (MaxVal.eq(CI->getValue()))
3769  break; // Recognized
3770  }
3771  return nullptr;
3772 
3773  default:
3774  return nullptr;
3775  }
3776 
3777  InstCombiner::BuilderTy &Builder = IC.Builder;
3778  Builder.SetInsertPoint(MulInstr);
3779 
3780  // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3781  Value *MulA = A, *MulB = B;
3782  if (WidthA < MulWidth)
3783  MulA = Builder.CreateZExt(A, MulType);
3784  if (WidthB < MulWidth)
3785  MulB = Builder.CreateZExt(B, MulType);
3787  Intrinsic::umul_with_overflow, MulType);
3788  CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
3789  IC.Worklist.Add(MulInstr);
3790 
3791  // If there are uses of mul result other than the comparison, we know that
3792  // they are truncation or binary AND. Change them to use result of
3793  // mul.with.overflow and adjust properly mask/size.
3794  if (MulVal->hasNUsesOrMore(2)) {
3795  Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
3796  for (User *U : MulVal->users()) {
3797  if (U == &I || U == OtherVal)
3798  continue;
3799  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3800  if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3801  IC.replaceInstUsesWith(*TI, Mul);
3802  else
3803  TI->setOperand(0, Mul);
3804  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3805  assert(BO->getOpcode() == Instruction::And);
3806  // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3807  ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3808  APInt ShortMask = CI->getValue().trunc(MulWidth);
3809  Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
3810  Instruction *Zext =
3811  cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
3812  IC.Worklist.Add(Zext);
3813  IC.replaceInstUsesWith(*BO, Zext);
3814  } else {
3815  llvm_unreachable("Unexpected Binary operation");
3816  }
3817  IC.Worklist.Add(cast<Instruction>(U));
3818  }
3819  }
3820  if (isa<Instruction>(OtherVal))
3821  IC.Worklist.Add(cast<Instruction>(OtherVal));
3822 
3823  // The original icmp gets replaced with the overflow value, maybe inverted
3824  // depending on predicate.
3825  bool Inverse = false;
3826  switch (I.getPredicate()) {
3827  case ICmpInst::ICMP_NE:
3828  break;
3829  case ICmpInst::ICMP_EQ:
3830  Inverse = true;
3831  break;
3832  case ICmpInst::ICMP_UGT:
3833  case ICmpInst::ICMP_UGE:
3834  if (I.getOperand(0) == MulVal)
3835  break;
3836  Inverse = true;
3837  break;
3838  case ICmpInst::ICMP_ULT:
3839  case ICmpInst::ICMP_ULE:
3840  if (I.getOperand(1) == MulVal)
3841  break;
3842  Inverse = true;
3843  break;
3844  default:
3845  llvm_unreachable("Unexpected predicate");
3846  }
3847  if (Inverse) {
3848  Value *Res = Builder.CreateExtractValue(Call, 1);
3849  return BinaryOperator::CreateNot(Res);
3850  }
3851 
3852  return ExtractValueInst::Create(Call, 1);
3853 }
3854 
3855 /// When performing a comparison against a constant, it is possible that not all
3856 /// the bits in the LHS are demanded. This helper method computes the mask that
3857 /// IS demanded.
3858 static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
3859  const APInt *RHS;
3860  if (!match(I.getOperand(1), m_APInt(RHS)))
3861  return APInt::getAllOnesValue(BitWidth);
3862 
3863  // If this is a normal comparison, it demands all bits. If it is a sign bit
3864  // comparison, it only demands the sign bit.
3865  bool UnusedBit;
3866  if (isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
3867  return APInt::getSignMask(BitWidth);
3868 
3869  switch (I.getPredicate()) {
3870  // For a UGT comparison, we don't care about any bits that
3871  // correspond to the trailing ones of the comparand. The value of these
3872  // bits doesn't impact the outcome of the comparison, because any value
3873  // greater than the RHS must differ in a bit higher than these due to carry.
3874  case ICmpInst::ICMP_UGT:
3875  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
3876 
3877  // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3878  // Any value less than the RHS must differ in a higher bit because of carries.
3879  case ICmpInst::ICMP_ULT:
3880  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
3881 
3882  default:
3883  return APInt::getAllOnesValue(BitWidth);
3884  }
3885 }
3886 
3887 /// Check if the order of \p Op0 and \p Op1 as operands in an ICmpInst
3888 /// should be swapped.
3889 /// The decision is based on how many times these two operands are reused
3890 /// as subtract operands and their positions in those instructions.
3891 /// The rationale is that several architectures use the same instruction for
3892 /// both subtract and cmp. Thus, it is better if the order of those operands
3893 /// match.
3894 /// \return true if Op0 and Op1 should be swapped.
3895 static bool swapMayExposeCSEOpportunities(const Value *Op0, const Value *Op1) {
3896  // Filter out pointer values as those cannot appear directly in subtract.
3897  // FIXME: we may want to go through inttoptrs or bitcasts.
3898  if (Op0->getType()->isPointerTy())
3899  return false;
3900  // If a subtract already has the same operands as a compare, swapping would be
3901  // bad. If a subtract has the same operands as a compare but in reverse order,
3902  // then swapping is good.
3903  int GoodToSwap = 0;
3904  for (const User *U : Op0->users()) {
3905  if (match(U, m_Sub(m_Specific(Op1), m_Specific(Op0))))
3906  GoodToSwap++;
3907  else if (match(U, m_Sub(m_Specific(Op0), m_Specific(Op1))))
3908  GoodToSwap--;
3909  }
3910  return GoodToSwap > 0;
3911 }
3912 
3913 /// \brief Check that one use is in the same block as the definition and all
3914 /// other uses are in blocks dominated by a given block.
3915 ///
3916 /// \param DI Definition
3917 /// \param UI Use
3918 /// \param DB Block that must dominate all uses of \p DI outside
3919 /// the parent block
3920 /// \return true when \p UI is the only use of \p DI in the parent block
3921 /// and all other uses of \p DI are in blocks dominated by \p DB.
3922 ///
3924  const Instruction *UI,
3925  const BasicBlock *DB) const {
3926  assert(DI && UI && "Instruction not defined\n");
3927  // Ignore incomplete definitions.
3928  if (!DI->getParent())
3929  return false;
3930  // DI and UI must be in the same block.
3931  if (DI->getParent() != UI->getParent())
3932  return false;
3933  // Protect from self-referencing blocks.
3934  if (DI->getParent() == DB)
3935  return false;
3936  for (const User *U : DI->users()) {
3937  auto *Usr = cast<Instruction>(U);
3938  if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
3939  return false;
3940  }
3941  return true;
3942 }
3943 
3944 /// Return true when the instruction sequence within a block is select-cmp-br.
3945 static bool isChainSelectCmpBranch(const SelectInst *SI) {
3946  const BasicBlock *BB = SI->getParent();
3947  if (!BB)
3948  return false;
3949  auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
3950  if (!BI || BI->getNumSuccessors() != 2)
3951  return false;
3952  auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
3953  if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
3954  return false;
3955  return true;
3956 }
3957 
3958 /// \brief True when a select result is replaced by one of its operands
3959 /// in select-icmp sequence. This will eventually result in the elimination
3960 /// of the select.
3961 ///
3962 /// \param SI Select instruction
3963 /// \param Icmp Compare instruction
3964 /// \param SIOpd Operand that replaces the select
3965 ///
3966 /// Notes:
3967 /// - The replacement is global and requires dominator information
3968 /// - The caller is responsible for the actual replacement
3969 ///
3970 /// Example:
3971 ///
3972 /// entry:
3973 /// %4 = select i1 %3, %C* %0, %C* null
3974 /// %5 = icmp eq %C* %4, null
3975 /// br i1 %5, label %9, label %7
3976 /// ...
3977 /// ; <label>:7 ; preds = %entry
3978 /// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
3979 /// ...
3980 ///
3981 /// can be transformed to
3982 ///
3983 /// %5 = icmp eq %C* %0, null
3984 /// %6 = select i1 %3, i1 %5, i1 true
3985 /// br i1 %6, label %9, label %7
3986 /// ...
3987 /// ; <label>:7 ; preds = %entry
3988 /// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
3989 ///
3990 /// Similar when the first operand of the select is a constant or/and
3991 /// the compare is for not equal rather than equal.
3992 ///
3993 /// NOTE: The function is only called when the select and compare constants
3994 /// are equal, the optimization can work only for EQ predicates. This is not a
3995 /// major restriction since a NE compare should be 'normalized' to an equal
3996 /// compare, which usually happens in the combiner and test case
3997 /// select-cmp-br.ll checks for it.
3999  const ICmpInst *Icmp,
4000  const unsigned SIOpd) {
4001  assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
4002  if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
4003  BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
4004  // The check for the single predecessor is not the best that can be
4005  // done. But it protects efficiently against cases like when SI's
4006  // home block has two successors, Succ and Succ1, and Succ1 predecessor
4007  // of Succ. Then SI can't be replaced by SIOpd because the use that gets
4008  // replaced can be reached on either path. So the uniqueness check
4009  // guarantees that the path all uses of SI (outside SI's parent) are on
4010  // is disjoint from all other paths out of SI. But that information
4011  // is more expensive to compute, and the trade-off here is in favor
4012  // of compile-time. It should also be noticed that we check for a single
4013  // predecessor and not only uniqueness. This to handle the situation when
4014  // Succ and Succ1 points to the same basic block.
4015  if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
4016  NumSel++;
4017  SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
4018  return true;
4019  }
4020  }
4021  return false;
4022 }
4023 
4024 /// Try to fold the comparison based on range information we can get by checking
4025 /// whether bits are known to be zero or one in the inputs.
4026 Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
4027  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4028  Type *Ty = Op0->getType();
4029  ICmpInst::Predicate Pred = I.getPredicate();
4030 
4031  // Get scalar or pointer size.
4032  unsigned BitWidth = Ty->isIntOrIntVectorTy()
4033  ? Ty->getScalarSizeInBits()
4034  : DL.getIndexTypeSizeInBits(Ty->getScalarType());
4035 
4036  if (!BitWidth)
4037  return nullptr;
4038 
4039  KnownBits Op0Known(BitWidth);
4040  KnownBits Op1Known(BitWidth);
4041 
4042  if (SimplifyDemandedBits(&I, 0,
4043  getDemandedBitsLHSMask(I, BitWidth),
4044  Op0Known, 0))
4045  return &I;
4046 
4047  if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4048  Op1Known, 0))
4049  return &I;
4050 
4051  // Given the known and unknown bits, compute a range that the LHS could be
4052  // in. Compute the Min, Max and RHS values based on the known bits. For the
4053  // EQ and NE we use unsigned values.
4054  APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4055  APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4056  if (I.isSigned()) {
4057  computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4058  computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4059  } else {
4060  computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4061  computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4062  }
4063 
4064  // If Min and Max are known to be the same, then SimplifyDemandedBits figured
4065  // out that the LHS or RHS is a constant. Constant fold this now, so that
4066  // code below can assume that Min != Max.
4067  if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4068  return new ICmpInst(Pred, ConstantExpr::getIntegerValue(Ty, Op0Min), Op1);
4069  if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4070  return new ICmpInst(Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Min));
4071 
4072  // Based on the range information we know about the LHS, see if we can
4073  // simplify this comparison. For example, (x&4) < 8 is always true.
4074  switch (Pred) {
4075  default:
4076  llvm_unreachable("Unknown icmp opcode!");
4077  case ICmpInst::ICMP_EQ:
4078  case ICmpInst::ICMP_NE: {
4079  if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4080  return Pred == CmpInst::ICMP_EQ
4081  ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4082  : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4083  }
4084 
4085  // If all bits are known zero except for one, then we know at most one bit
4086  // is set. If the comparison is against zero, then this is a check to see if
4087  // *that* bit is set.
4088  APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4089  if (Op1Known.isZero()) {
4090  // If the LHS is an AND with the same constant, look through it.
4091  Value *LHS = nullptr;
4092  const APInt *LHSC;
4093  if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4094  *LHSC != Op0KnownZeroInverted)
4095  LHS = Op0;
4096 
4097  Value *X;
4098  if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4099  APInt ValToCheck = Op0KnownZeroInverted;
4100  Type *XTy = X->getType();
4101  if (ValToCheck.isPowerOf2()) {
4102  // ((1 << X) & 8) == 0 -> X != 3
4103  // ((1 << X) & 8) != 0 -> X == 3
4104  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4105  auto NewPred = ICmpInst::getInversePredicate(Pred);
4106  return new ICmpInst(NewPred, X, CmpC);
4107  } else if ((++ValToCheck).isPowerOf2()) {
4108  // ((1 << X) & 7) == 0 -> X >= 3
4109  // ((1 << X) & 7) != 0 -> X < 3
4110  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4111  auto NewPred =
4113  return new ICmpInst(NewPred, X, CmpC);
4114  }
4115  }
4116 
4117  // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4118  const APInt *CI;
4119  if (Op0KnownZeroInverted.isOneValue() &&
4120  match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4121  // ((8 >>u X) & 1) == 0 -> X != 3
4122  // ((8 >>u X) & 1) != 0 -> X == 3
4123  unsigned CmpVal = CI->countTrailingZeros();
4124  auto NewPred = ICmpInst::getInversePredicate(Pred);
4125  return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4126  }
4127  }
4128  break;
4129  }
4130  case ICmpInst::ICMP_ULT: {
4131  if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4132  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4133  if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4134  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4135  if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4136  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4137 
4138  const APInt *CmpC;
4139  if (match(Op1, m_APInt(CmpC))) {
4140  // A <u C -> A == C-1 if min(A)+1 == C
4141  if (*CmpC == Op0Min + 1)
4142  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4143  ConstantInt::get(Op1->getType(), *CmpC - 1));
4144  // X <u C --> X == 0, if the number of zero bits in the bottom of X
4145  // exceeds the log2 of C.
4146  if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
4147  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4148  Constant::getNullValue(Op1->getType()));
4149  }
4150  break;
4151  }
4152  case ICmpInst::ICMP_UGT: {
4153  if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4154  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4155  if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4156  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4157  if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4158  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4159 
4160  const APInt *CmpC;
4161  if (match(Op1, m_APInt(CmpC))) {
4162  // A >u C -> A == C+1 if max(a)-1 == C
4163  if (*CmpC == Op0Max - 1)
4164  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4165  ConstantInt::get(Op1->getType(), *CmpC + 1));
4166  // X >u C --> X != 0, if the number of zero bits in the bottom of X
4167  // exceeds the log2 of C.
4168  if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
4169  return new ICmpInst(ICmpInst::ICMP_NE, Op0,
4170  Constant::getNullValue(Op1->getType()));
4171  }
4172  break;
4173  }
4174  case ICmpInst::ICMP_SLT: {
4175  if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4176  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4177  if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4178  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4179  if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4180  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4181  const APInt *CmpC;
4182  if (match(Op1, m_APInt(CmpC))) {
4183  if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4184  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4185  ConstantInt::get(Op1->getType(), *CmpC - 1));
4186  }
4187  break;
4188  }
4189  case ICmpInst::ICMP_SGT: {
4190  if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4191  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4192  if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4193  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4194  if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4195  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4196  const APInt *CmpC;
4197  if (match(Op1, m_APInt(CmpC))) {
4198  if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4199  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4200  ConstantInt::get(Op1->getType(), *CmpC + 1));
4201  }
4202  break;
4203  }
4204  case ICmpInst::ICMP_SGE:
4205  assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
4206  if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4207  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4208  if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4209  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4210  if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
4211  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4212  break;
4213  case ICmpInst::ICMP_SLE:
4214  assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
4215  if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4216  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4217  if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4218  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4219  if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
4220  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4221  break;
4222  case ICmpInst::ICMP_UGE:
4223  assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
4224  if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4225  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4226  if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4227  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4228  if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
4229  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4230  break;
4231  case ICmpInst::ICMP_ULE:
4232  assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
4233  if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4234  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4235  if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4236  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4237  if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
4238  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4239  break;
4240  }
4241 
4242  // Turn a signed comparison into an unsigned one if both operands are known to
4243  // have the same sign.
4244  if (I.isSigned() &&
4245  ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4246  (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4247  return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4248 
4249  return nullptr;
4250 }
4251 
4252 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
4253 /// it into the appropriate icmp lt or icmp gt instruction. This transform
4254 /// allows them to be folded in visitICmpInst.
4256  ICmpInst::Predicate Pred = I.getPredicate();
4257  if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4258  Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4259  return nullptr;
4260 
4261  Value *Op0 = I.getOperand(0);
4262  Value *Op1 = I.getOperand(1);
4263  auto *Op1C = dyn_cast<Constant>(Op1);
4264  if (!Op1C)
4265  return nullptr;
4266 
4267  // Check if the constant operand can be safely incremented/decremented without
4268  // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4269  // the edge cases for us, so we just assert on them. For vectors, we must
4270  // handle the edge cases.
4271  Type *Op1Type = Op1->getType();
4272  bool IsSigned = I.isSigned();
4273  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4274  auto *CI = dyn_cast<ConstantInt>(Op1C);
4275  if (CI) {
4276  // A <= MAX -> TRUE ; A >= MIN -> TRUE
4277  assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
4278  } else if (Op1Type->isVectorTy()) {
4279  // TODO? If the edge cases for vectors were guaranteed to be handled as they
4280  // are for scalar, we could remove the min/max checks. However, to do that,
4281  // we would have to use insertelement/shufflevector to replace edge values.
4282  unsigned NumElts = Op1Type->getVectorNumElements();
4283  for (unsigned i = 0; i != NumElts; ++i) {
4284  Constant *Elt = Op1C->getAggregateElement(i);
4285  if (!Elt)
4286  return nullptr;
4287 
4288  if (isa<UndefValue>(Elt))
4289  continue;
4290 
4291  // Bail out if we can't determine if this constant is min/max or if we
4292  // know that this constant is min/max.
4293  auto *CI = dyn_cast<ConstantInt>(Elt);
4294  if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4295  return nullptr;
4296  }
4297  } else {
4298  // ConstantExpr?
4299  return nullptr;
4300  }
4301 
4302  // Increment or decrement the constant and set the new comparison predicate:
4303  // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4304  Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4306  NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4307  return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4308 }
4309 
4310 /// Integer compare with boolean values can always be turned into bitwise ops.
4312  InstCombiner::BuilderTy &Builder) {
4313  Value *A = I.getOperand(0), *B = I.getOperand(1);
4314  assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
4315 
4316  // A boolean compared to true/false can be simplified to Op0/true/false in
4317  // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
4318  // Cases not handled by InstSimplify are always 'not' of Op0.
4319  if (match(B, m_Zero())) {
4320  switch (I.getPredicate()) {
4321  case CmpInst::ICMP_EQ: // A == 0 -> !A
4322  case CmpInst::ICMP_ULE: // A <=u 0 -> !A
4323  case CmpInst::ICMP_SGE: // A >=s 0 -> !A
4324  return BinaryOperator::CreateNot(A);
4325  default:
4326  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4327  }
4328  } else if (match(B, m_One())) {
4329  switch (I.getPredicate()) {
4330  case CmpInst::ICMP_NE: // A != 1 -> !A
4331  case CmpInst::ICMP_ULT: // A <u 1 -> !A
4332  case CmpInst::ICMP_SGT: // A >s -1 -> !A
4333  return BinaryOperator::CreateNot(A);
4334  default:
4335  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4336  }
4337  }
4338 
4339  switch (I.getPredicate()) {
4340  default:
4341  llvm_unreachable("Invalid icmp instruction!");
4342  case ICmpInst::ICMP_EQ:
4343  // icmp eq i1 A, B -> ~(A ^ B)
4344  return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
4345 
4346  case ICmpInst::ICMP_NE:
4347  // icmp ne i1 A, B -> A ^ B
4348  return BinaryOperator::CreateXor(A, B);
4349 
4350  case ICmpInst::ICMP_UGT:
4351  // icmp ugt -> icmp ult
4352  std::swap(A, B);
4354  case ICmpInst::ICMP_ULT:
4355  // icmp ult i1 A, B -> ~A & B
4356  return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
4357 
4358  case ICmpInst::ICMP_SGT:
4359  // icmp sgt -> icmp slt
4360  std::swap(A, B);
4362  case ICmpInst::ICMP_SLT:
4363  // icmp slt i1 A, B -> A & ~B
4364  return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
4365 
4366  case ICmpInst::ICMP_UGE:
4367  // icmp uge -> icmp ule
4368  std::swap(A, B);
4370  case ICmpInst::ICMP_ULE:
4371  // icmp ule i1 A, B -> ~A | B
4372  return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
4373 
4374  case ICmpInst::ICMP_SGE:
4375  // icmp sge -> icmp sle
4376  std::swap(A, B);
4378  case ICmpInst::ICMP_SLE:
4379  // icmp sle i1 A, B -> A | ~B
4380  return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
4381  }
4382 }
4383 
4385  bool Changed = false;
4386  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4387  unsigned Op0Cplxity = getComplexity(Op0);
4388  unsigned Op1Cplxity = getComplexity(Op1);
4389 
4390  /// Orders the operands of the compare so that they are listed from most
4391  /// complex to least complex. This puts constants before unary operators,
4392  /// before binary operators.
4393  if (Op0Cplxity < Op1Cplxity ||
4394  (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4395  I.swapOperands();
4396  std::swap(Op0, Op1);
4397  Changed = true;
4398  }
4399 
4400  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4401  SQ.getWithInstruction(&I)))
4402  return replaceInstUsesWith(I, V);
4403 
4404  // Comparing -val or val with non-zero is the same as just comparing val
4405  // ie, abs(val) != 0 -> val != 0
4406  if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4407  Value *Cond, *SelectTrue, *SelectFalse;
4408  if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4409  m_Value(SelectFalse)))) {
4410  if (Value *V = dyn_castNegVal(SelectTrue)) {
4411  if (V == SelectFalse)
4412  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4413  }
4414  else if (Value *V = dyn_castNegVal(SelectFalse)) {
4415  if (V == SelectTrue)
4416  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4417  }
4418  }
4419  }
4420 
4421  if (Op0->getType()->isIntOrIntVectorTy(1))
4422  if (Instruction *Res = canonicalizeICmpBool(I, Builder))
4423  return Res;
4424 
4425  if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4426  return NewICmp;
4427 
4428  if (Instruction *Res = foldICmpWithConstant(I))
4429  return Res;
4430 
4431  if (Instruction *Res = foldICmpUsingKnownBits(I))
4432  return Res;
4433 
4434  // Test if the ICmpInst instruction is used exclusively by a select as
4435  // part of a minimum or maximum operation. If so, refrain from doing
4436  // any other folding. This helps out other analyses which understand
4437  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4438  // and CodeGen. And in this case, at least one of the comparison
4439  // operands has at least one user besides the compare (the select),
4440  // which would often largely negate the benefit of folding anyway.
4441  //
4442  // Do the same for the other patterns recognized by matchSelectPattern.
4443  if (I.hasOneUse())
4444  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4445  Value *A, *B;
4446  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4447  if (SPR.Flavor != SPF_UNKNOWN)
4448  return nullptr;
4449  }
4450 
4451  // Do this after checking for min/max to prevent infinite looping.
4452  if (Instruction *Res = foldICmpWithZero(I))
4453  return Res;
4454 
4455  // FIXME: We only do this after checking for min/max to prevent infinite
4456  // looping caused by a reverse canonicalization of these patterns for min/max.
4457  // FIXME: The organization of folds is a mess. These would naturally go into
4458  // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4459  // down here after the min/max restriction.
4460  ICmpInst::Predicate Pred = I.getPredicate();
4461  const APInt *C;
4462  if (match(Op1, m_APInt(C))) {
4463  // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4464  if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4465  Constant *Zero = Constant::getNullValue(Op0->getType());
4466  return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4467  }
4468 
4469  // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4470  if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4471  Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4472  return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4473  }
4474  }
4475 
4476  if (Instruction *Res = foldICmpInstWithConstant(I))
4477  return Res;
4478 
4479  if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4480  return Res;
4481 
4482  // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4483  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4484  if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4485  return NI;
4486  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4487  if (Instruction *NI = foldGEPICmp(GEP, Op0,
4489  return NI;
4490 
4491  // Try to optimize equality comparisons against alloca-based pointers.
4492  if (Op0->getType()->isPointerTy() && I.isEquality()) {
4493  assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
4494  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4495  if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4496  return New;
4497  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4498  if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4499  return New;
4500  }
4501 
4502  // Test to see if the operands of the icmp are casted versions of other
4503  // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4504  // now.
4505  if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4506  if (Op0->getType()->isPointerTy() &&
4507  (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4508  // We keep moving the cast from the left operand over to the right
4509  // operand, where it can often be eliminated completely.
4510  Op0 = CI->getOperand(0);
4511 
4512  // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4513  // so eliminate it as well.
4514  if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4515  Op1 = CI2->getOperand(0);
4516 
4517  // If Op1 is a constant, we can fold the cast into the constant.
4518  if (Op0->getType() != Op1->getType()) {
4519  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4520  Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4521  } else {
4522  // Otherwise, cast the RHS right before the icmp
4523  Op1 = Builder.CreateBitCast(Op1, Op0->getType());
4524  }
4525  }
4526  return new ICmpInst(I.getPredicate(), Op0, Op1);
4527  }
4528  }
4529 
4530  if (isa<CastInst>(Op0)) {
4531  // Handle the special case of: icmp (cast bool to X), <cst>
4532  // This comes up when you have code like
4533  // int X = A < B;
4534  // if (X) ...
4535  // For generality, we handle any zero-extension of any operand comparison
4536  // with a constant or another cast from the same type.
4537  if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4538  if (Instruction *R = foldICmpWithCastAndCast(I))
4539  return R;
4540  }
4541 
4542  if (Instruction *Res = foldICmpBinOp(I))
4543  return Res;
4544 
4545  if (Instruction *Res = foldICmpWithMinMax(I))
4546  return Res;
4547 
4548  {
4549  Value *A, *B;
4550  // Transform (A & ~B) == 0 --> (A & B) != 0
4551  // and (A & ~B) != 0 --> (A & B) == 0
4552  // if A is a power of 2.
4553  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4554  match(Op1, m_Zero()) &&
4555  isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
4556  return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
4557  Op1);
4558 
4559  // ~X < ~Y --> Y < X
4560  // ~X < C --> X > ~C
4561  if (match(Op0, m_Not(m_Value(A)))) {
4562  if (match(Op1, m_Not(m_Value(B))))
4563  return new ICmpInst(I.getPredicate(), B, A);
4564 
4565  const APInt *C;
4566  if (match(Op1, m_APInt(C)))
4567  return new ICmpInst(I.getSwappedPredicate(), A,
4568  ConstantInt::get(Op1->getType(), ~(*C)));
4569  }
4570 
4571  Instruction *AddI = nullptr;
4572  if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4573  m_Instruction(AddI))) &&
4574  isa<IntegerType>(A->getType())) {
4575  Value *Result;
4576  Constant *Overflow;
4577  if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4578  Overflow)) {
4579  replaceInstUsesWith(*AddI, Result);
4580  return replaceInstUsesWith(I, Overflow);
4581  }
4582  }
4583 
4584  // (zext a) * (zext b) --> llvm.umul.with.overflow.
4585  if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4586  if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4587  return R;
4588  }
4589  if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4590  if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4591  return R;
4592  }
4593  }
4594 
4595  if (Instruction *Res = foldICmpEquality(I))
4596  return Res;
4597 
4598  // The 'cmpxchg' instruction returns an aggregate containing the old value and
4599  // an i1 which indicates whether or not we successfully did the swap.
4600  //
4601  // Replace comparisons between the old value and the expected value with the
4602  // indicator that 'cmpxchg' returns.
4603  //
4604  // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4605  // spuriously fail. In those cases, the old value may equal the expected
4606  // value but it is possible for the swap to not occur.
4607  if (I.getPredicate() == ICmpInst::ICMP_EQ)
4608  if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4609  if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4610  if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4611  !ACXI->isWeak())
4612  return ExtractValueInst::Create(ACXI, 1);
4613 
4614  {
4615  Value *X; ConstantInt *Cst;
4616  // icmp X+Cst, X
4617  if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4618  return foldICmpAddOpConst(X, Cst, I.getPredicate());
4619 
4620  // icmp X, X+Cst
4621  if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4622  return foldICmpAddOpConst(X, Cst, I.getSwappedPredicate());
4623  }
4624  return Changed ? &I : nullptr;
4625 }
4626 
4627 /// Fold fcmp ([us]itofp x, cst) if possible.
4628 Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4629  Constant *RHSC) {
4630  if (!isa<ConstantFP>(RHSC)) return nullptr;
4631  const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4632 
4633  // Get the width of the mantissa. We don't want to hack on conversions that
4634  // might lose information from the integer, e.g. "i64 -> float"
4635  int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4636  if (MantissaWidth == -1) return nullptr; // Unknown.
4637 
4638  IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4639 
4640  bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4641 
4642  if (I.isEquality()) {
4644  bool IsExact = false;
4645  APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4646  RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4647 
4648  // If the floating point constant isn't an integer value, we know if we will
4649  // ever compare equal / not equal to it.
4650  if (!IsExact) {
4651  // TODO: Can never be -0.0 and other non-representable values
4652  APFloat RHSRoundInt(RHS);
4654  if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4655  if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4656  return replaceInstUsesWith(I, Builder.getFalse());
4657 
4659  return replaceInstUsesWith(I, Builder.getTrue());
4660  }
4661  }
4662 
4663  // TODO: If the constant is exactly representable, is it always OK to do
4664  // equality compares as integer?
4665  }
4666 
4667  // Check to see that the input is converted from an integer type that is small
4668  // enough that preserves all bits. TODO: check here for "known" sign bits.
4669  // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4670  unsigned InputSize = IntTy->getScalarSizeInBits();
4671 
4672  // Following test does NOT adjust InputSize downwards for signed inputs,
4673  // because the most negative value still requires all the mantissa bits
4674  // to distinguish it from one less than that value.
4675  if ((int)InputSize > MantissaWidth) {
4676  // Conversion would lose accuracy. Check if loss can impact comparison.
4677  int Exp = ilogb(RHS);
4678  if (Exp == APFloat::IEK_Inf) {
4679  int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4680  if (MaxExponent < (int)InputSize - !LHSUnsigned)
4681  // Conversion could create infinity.
4682  return nullptr;
4683  } else {
4684  // Note that if RHS is zero or NaN, then Exp is negative
4685  // and first condition is trivially false.
4686  if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4687  // Conversion could affect comparison.
4688  return nullptr;
4689  }
4690  }
4691 
4692  // Otherwise, we can potentially simplify the comparison. We know that it
4693  // will always come through as an integer value and we know the constant is
4694  // not a NAN (it would have been previously simplified).
4695  assert(!RHS.isNaN() && "NaN comparison not already folded!");
4696 
4697  ICmpInst::Predicate Pred;
4698  switch (I.getPredicate()) {
4699  default: llvm_unreachable("Unexpected predicate!");
4700  case FCmpInst::FCMP_UEQ:
4701  case FCmpInst::FCMP_OEQ:
4702  Pred = ICmpInst::ICMP_EQ;
4703  break;
4704  case FCmpInst::FCMP_UGT:
4705  case FCmpInst::FCMP_OGT:
4706  Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4707  break;
4708  case FCmpInst::FCMP_UGE:
4709  case FCmpInst::FCMP_OGE:
4710  Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4711  break;
4712  case FCmpInst::FCMP_ULT:
4713  case FCmpInst::FCMP_OLT:
4714  Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4715  break;
4716  case FCmpInst::FCMP_ULE:
4717  case FCmpInst::FCMP_OLE:
4718  Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4719  break;
4720  case FCmpInst::FCMP_UNE:
4721  case FCmpInst::FCMP_ONE:
4722  Pred = ICmpInst::ICMP_NE;
4723  break;
4724  case FCmpInst::FCMP_ORD:
4725  return replaceInstUsesWith(I, Builder.getTrue());
4726  case FCmpInst::FCMP_UNO:
4727  return replaceInstUsesWith(I, Builder.getFalse());
4728  }
4729 
4730  // Now we know that the APFloat is a normal number, zero or inf.
4731 
4732  // See if the FP constant is too large for the integer. For example,
4733  // comparing an i8 to 300.0.
4734  unsigned IntWidth = IntTy->getScalarSizeInBits();
4735 
4736  if (!LHSUnsigned) {
4737  // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4738  // and large values.
4739  APFloat SMax(RHS.getSemantics());
4740  SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4742  if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4743  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4744  Pred == ICmpInst::ICMP_SLE)
4745  return replaceInstUsesWith(I, Builder.getTrue());
4746  return replaceInstUsesWith(I, Builder.getFalse());
4747  }
4748  } else {
4749  // If the RHS value is > UnsignedMax, fold the comparison. This handles
4750  // +INF and large values.
4751  APFloat UMax(RHS.getSemantics());
4752  UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4754  if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4755  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4756  Pred == ICmpInst::ICMP_ULE)
4757  return replaceInstUsesWith(I, Builder.getTrue());
4758  return replaceInstUsesWith(I, Builder.getFalse());
4759  }
4760  }
4761 
4762  if (!LHSUnsigned) {
4763  // See if the RHS value is < SignedMin.
4764  APFloat SMin(RHS.getSemantics());
4765  SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4767  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4768  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4769  Pred == ICmpInst::ICMP_SGE)
4770  return replaceInstUsesWith(I, Builder.getTrue());
4771  return replaceInstUsesWith(I, Builder.getFalse());
4772  }
4773  } else {
4774  // See if the RHS value is < UnsignedMin.
4775  APFloat SMin(RHS.getSemantics());
4776  SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4778  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4779  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4780  Pred == ICmpInst::ICMP_UGE)
4781  return replaceInstUsesWith(I, Builder.getTrue());
4782  return replaceInstUsesWith(I, Builder.getFalse());
4783  }
4784  }
4785 
4786  // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4787  // [0, UMAX], but it may still be fractional. See if it is fractional by
4788  // casting the FP value to the integer value and back, checking for equality.
4789  // Don't do this for zero, because -0.0 is not fractional.
4790  Constant *RHSInt = LHSUnsigned
4791  ? ConstantExpr::getFPToUI(RHSC, IntTy)
4792  : ConstantExpr::getFPToSI(RHSC, IntTy);
4793  if (!RHS.isZero()) {
4794  bool Equal = LHSUnsigned
4795  ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4796  : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4797  if (!Equal) {
4798  // If we had a comparison against a fractional value, we have to adjust
4799  // the compare predicate and sometimes the value. RHSC is rounded towards
4800  // zero at this point.
4801  switch (Pred) {
4802  default: llvm_unreachable("Unexpected integer comparison!");
4803  case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4804  return replaceInstUsesWith(I, Builder.getTrue());
4805  case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4806  return replaceInstUsesWith(I, Builder.getFalse());
4807  case ICmpInst::ICMP_ULE:
4808  // (float)int <= 4.4 --> int <= 4
4809  // (float)int <= -4.4 --> false
4810  if (RHS.isNegative())
4811  return replaceInstUsesWith(I, Builder.getFalse());
4812  break;
4813  case ICmpInst::ICMP_SLE:
4814  // (float)int <= 4.4 --> int <= 4
4815  // (float)int <= -4.4 --> int < -4
4816  if (RHS.isNegative())
4817  Pred = ICmpInst::ICMP_SLT;
4818  break;
4819  case ICmpInst::ICMP_ULT:
4820  // (float)int < -4.4 --> false
4821  // (float)int < 4.4 --> int <= 4
4822  if (RHS.isNegative())
4823  return replaceInstUsesWith(I, Builder.getFalse());
4824  Pred = ICmpInst::ICMP_ULE;
4825  break;
4826  case ICmpInst::ICMP_SLT:
4827  // (float)int < -4.4 --> int < -4
4828  // (float)int < 4.4 --> int <= 4
4829  if (!RHS.isNegative())
4830  Pred = ICmpInst::ICMP_SLE;
4831  break;
4832  case ICmpInst::ICMP_UGT:
4833  // (float)int > 4.4 --> int > 4
4834  // (float)int > -4.4 --> true
4835  if (RHS.isNegative())
4836  return replaceInstUsesWith(I, Builder.getTrue());
4837  break;
4838  case ICmpInst::ICMP_SGT:
4839  // (float)int > 4.4 --> int > 4
4840  // (float)int > -4.4 --> int >= -4
4841  if (RHS.isNegative())
4842  Pred = ICmpInst::ICMP_SGE;
4843  break;
4844  case ICmpInst::ICMP_UGE:
4845  // (float)int >= -4.4 --> true
4846  // (float)int >= 4.4 --> int > 4
4847  if (RHS.isNegative())
4848  return replaceInstUsesWith(I, Builder.getTrue());
4849  Pred = ICmpInst::ICMP_UGT;
4850  break;
4851  case ICmpInst::ICMP_SGE:
4852  // (float)int >= -4.4 --> int >= -4
4853  // (float)int >= 4.4 --> int > 4
4854  if (!RHS.isNegative())
4855  Pred = ICmpInst::ICMP_SGT;
4856  break;
4857  }
4858  }
4859  }
4860 
4861  // Lower this FP comparison into an appropriate integer version of the
4862  // comparison.
4863  return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4864 }
4865 
4867  bool Changed = false;
4868 
4869  /// Orders the operands of the compare so that they are listed from most
4870  /// complex to least complex. This puts constants before unary operators,
4871  /// before binary operators.
4872  if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4873  I.swapOperands();
4874  Changed = true;
4875  }
4876 
4877  const CmpInst::Predicate Pred = I.getPredicate();
4878  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4879  if (Value *V = SimplifyFCmpInst(Pred, Op0, Op1, I.getFastMathFlags(),
4880  SQ.getWithInstruction(&I)))
4881  return replaceInstUsesWith(I, V);
4882 
4883  // Simplify 'fcmp pred X, X'
4884  if (Op0 == Op1) {
4885  switch (Pred) {
4886  default: break;
4887  case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4888  case FCmpInst::FCMP_ULT: // True if unordered or less than
4889  case FCmpInst::FCMP_UGT: // True if unordered or greater than
4890  case FCmpInst::FCMP_UNE: // True if unordered or not equal
4891  // Canonicalize these to be 'fcmp uno %X, 0.0'.
4894  return &I;
4895 
4896  case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4897  case FCmpInst::FCMP_OEQ: // True if ordered and equal
4898  case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4899  case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4900  // Canonicalize these to be 'fcmp ord %X, 0.0'.
4903  return &I;
4904  }
4905  }
4906 
4907  // If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
4908  // then canonicalize the operand to 0.0.
4909  if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
4910  if (!match(Op0, m_Zero()) && isKnownNeverNaN(Op0)) {
4912  return &I;
4913  }
4914  if (!match(Op1, m_Zero()) && isKnownNeverNaN(Op1)) {
4916  return &I;
4917  }
4918  }
4919 
4920  // Test if the FCmpInst instruction is used exclusively by a select as
4921  // part of a minimum or maximum operation. If so, refrain from doing
4922  // any other folding. This helps out other analyses which understand
4923  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4924  // and CodeGen. And in this case, at least one of the comparison
4925  // operands has at least one user besides the compare (the select),
4926  // which would often largely negate the benefit of folding anyway.
4927  if (I.hasOneUse())
4928  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4929  Value *A, *B;
4930  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4931  if (SPR.Flavor != SPF_UNKNOWN)
4932  return nullptr;
4933  }
4934 
4935  // Handle fcmp with constant RHS
4936  if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4937  if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4938  switch (LHSI->getOpcode()) {
4939  case Instruction::FPExt: {
4940  // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
4941  FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
4942  ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
4943  if (!RHSF)
4944  break;
4945 
4946  const fltSemantics *Sem;
4947  // FIXME: This shouldn't be here.
4948  if (LHSExt->getSrcTy()->isHalfTy())
4949  Sem = &APFloat::IEEEhalf();
4950  else if (LHSExt->getSrcTy()->isFloatTy())
4951  Sem = &APFloat::IEEEsingle();
4952  else if (LHSExt->getSrcTy()->isDoubleTy())
4953  Sem = &APFloat::IEEEdouble();
4954  else if (LHSExt->getSrcTy()->isFP128Ty())
4955  Sem = &APFloat::IEEEquad();
4956  else if (LHSExt->getSrcTy()->isX86_FP80Ty())
4957  Sem = &APFloat::x87DoubleExtended();
4958  else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
4959  Sem = &APFloat::PPCDoubleDouble();
4960  else
4961  break;
4962 
4963  bool Lossy;
4964  APFloat F = RHSF->getValueAPF();
4965  F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
4966 
4967  // Avoid lossy conversions and denormals. Zero is a special case
4968  // that's OK to convert.
4969  APFloat Fabs = F;
4970  Fabs.clearSign();
4971  if (!Lossy &&
4972  ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
4973  APFloat::cmpLessThan) || Fabs.isZero()))
4974 
4975  return new FCmpInst(Pred, LHSExt->getOperand(0),
4976  ConstantFP::get(RHSC->getContext(), F));
4977  break;
4978  }
4979  case Instruction::PHI:
4980  // Only fold fcmp into the PHI if the phi and fcmp are in the same
4981  // block. If in the same block, we're encouraging jump threading. If
4982  // not, we are just pessimizing the code by making an i1 phi.
4983  if (LHSI->getParent() == I.getParent())
4984  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
4985  return NV;
4986  break;
4987  case Instruction::SIToFP:
4988  case Instruction::UIToFP:
4989  if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
4990  return NV;
4991  break;
4992  case Instruction::FSub: {
4993  // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
4994  Value *Op;
4995  if (match(LHSI, m_FNeg(m_Value(Op))))
4996  return new FCmpInst(I.getSwappedPredicate(), Op,
4997  ConstantExpr::getFNeg(RHSC));
4998  break;
4999  }
5000  case Instruction::Load:
5001  if (GetElementPtrInst *GEP =
5002  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
5003  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
5004  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
5005  !cast<LoadInst>(LHSI)->isVolatile())
5006  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
5007  return Res;
5008  }
5009  break;
5010  case Instruction::Call: {
5011  if (!RHSC->isNullValue())
5012  break;
5013 
5014  CallInst *CI = cast<CallInst>(LHSI);
5015  Intrinsic::ID IID = getIntrinsicForCallSite(CI, &TLI);
5016  if (IID != Intrinsic::fabs)
5017  break;
5018 
5019  // Various optimization for fabs compared with zero.
5020  switch (Pred) {
5021  default:
5022  break;
5023  // fabs(x) < 0 --> false
5024  case FCmpInst::FCMP_OLT:
5025  llvm_unreachable("handled by SimplifyFCmpInst");
5026  // fabs(x) > 0 --> x != 0
5027  case FCmpInst::FCMP_OGT:
5028  return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC);
5029  // fabs(x) <= 0 --> x == 0
5030  case FCmpInst::FCMP_OLE:
5031  return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC);
5032  // fabs(x) >= 0 --> !isnan(x)
5033  case FCmpInst::FCMP_OGE:
5034  return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC);
5035  // fabs(x) == 0 --> x == 0
5036  // fabs(x) != 0 --> x != 0
5037  case FCmpInst::FCMP_OEQ:
5038  case FCmpInst::FCMP_UEQ:
5039  case FCmpInst::FCMP_ONE:
5040  case FCmpInst::FCMP_UNE:
5041  return new FCmpInst(Pred, CI->getArgOperand(0), RHSC);
5042  }
5043  }
5044  }
5045  }
5046 
5047  // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
5048  Value *X, *Y;
5049  if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
5050  return new FCmpInst(I.getSwappedPredicate(), X, Y);
5051 
5052  // fcmp (fpext x), (fpext y) -> fcmp x, y
5053  if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0))
5054  if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1))
5055  if (LHSExt->getSrcTy() == RHSExt->getSrcTy())
5056  return new FCmpInst(Pred, LHSExt->getOperand(0), RHSExt->getOperand(0));
5057 
5058  return Changed ? &I : nullptr;
5059 }
static unsigned getBitWidth(