LLVM  6.0.0svn
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"
23 #include "llvm/IR/ConstantRange.h"
24 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/PatternMatch.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/KnownBits.h"
30 
31 using namespace llvm;
32 using namespace PatternMatch;
33 
34 #define DEBUG_TYPE "instcombine"
35 
36 // How many times is a select replaced by one of its operands?
37 STATISTIC(NumSel, "Number of select opts");
38 
39 
40 /// Compute Result = In1+In2, returning true if the result overflowed for this
41 /// type.
42 static bool addWithOverflow(APInt &Result, const APInt &In1,
43  const APInt &In2, bool IsSigned = false) {
44  bool Overflow;
45  if (IsSigned)
46  Result = In1.sadd_ov(In2, Overflow);
47  else
48  Result = In1.uadd_ov(In2, Overflow);
49 
50  return Overflow;
51 }
52 
53 /// Compute Result = In1-In2, returning true if the result overflowed for this
54 /// type.
55 static bool subWithOverflow(APInt &Result, const APInt &In1,
56  const APInt &In2, bool IsSigned = false) {
57  bool Overflow;
58  if (IsSigned)
59  Result = In1.ssub_ov(In2, Overflow);
60  else
61  Result = In1.usub_ov(In2, Overflow);
62 
63  return Overflow;
64 }
65 
66 /// Given an icmp instruction, return true if any use of this comparison is a
67 /// branch on sign bit comparison.
68 static bool hasBranchUse(ICmpInst &I) {
69  for (auto *U : I.users())
70  if (isa<BranchInst>(U))
71  return true;
72  return false;
73 }
74 
75 /// Given an exploded icmp instruction, return true if the comparison only
76 /// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if the
77 /// result of the comparison is true when the input value is signed.
78 static bool isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
79  bool &TrueIfSigned) {
80  switch (Pred) {
81  case ICmpInst::ICMP_SLT: // True if LHS s< 0
82  TrueIfSigned = true;
83  return RHS.isNullValue();
84  case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
85  TrueIfSigned = true;
86  return RHS.isAllOnesValue();
87  case ICmpInst::ICMP_SGT: // True if LHS s> -1
88  TrueIfSigned = false;
89  return RHS.isAllOnesValue();
90  case ICmpInst::ICMP_UGT:
91  // True if LHS u> RHS and RHS == high-bit-mask - 1
92  TrueIfSigned = true;
93  return RHS.isMaxSignedValue();
94  case ICmpInst::ICMP_UGE:
95  // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
96  TrueIfSigned = true;
97  return RHS.isSignMask();
98  default:
99  return false;
100  }
101 }
102 
103 /// Returns true if the exploded icmp can be expressed as a signed comparison
104 /// to zero and updates the predicate accordingly.
105 /// The signedness of the comparison is preserved.
106 /// TODO: Refactor with decomposeBitTestICmp()?
107 static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
108  if (!ICmpInst::isSigned(Pred))
109  return false;
110 
111  if (C.isNullValue())
112  return ICmpInst::isRelational(Pred);
113 
114  if (C.isOneValue()) {
115  if (Pred == ICmpInst::ICMP_SLT) {
116  Pred = ICmpInst::ICMP_SLE;
117  return true;
118  }
119  } else if (C.isAllOnesValue()) {
120  if (Pred == ICmpInst::ICMP_SGT) {
121  Pred = ICmpInst::ICMP_SGE;
122  return true;
123  }
124  }
125 
126  return false;
127 }
128 
129 /// Given a signed integer type and a set of known zero and one bits, compute
130 /// the maximum and minimum values that could have the specified known zero and
131 /// known one bits, returning them in Min/Max.
132 /// TODO: Move to method on KnownBits struct?
134  APInt &Min, APInt &Max) {
135  assert(Known.getBitWidth() == Min.getBitWidth() &&
136  Known.getBitWidth() == Max.getBitWidth() &&
137  "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
138  APInt UnknownBits = ~(Known.Zero|Known.One);
139 
140  // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
141  // bit if it is unknown.
142  Min = Known.One;
143  Max = Known.One|UnknownBits;
144 
145  if (UnknownBits.isNegative()) { // Sign bit is unknown
146  Min.setSignBit();
147  Max.clearSignBit();
148  }
149 }
150 
151 /// Given an unsigned integer type and a set of known zero and one bits, compute
152 /// the maximum and minimum values that could have the specified known zero and
153 /// known one bits, returning them in Min/Max.
154 /// TODO: Move to method on KnownBits struct?
156  APInt &Min, APInt &Max) {
157  assert(Known.getBitWidth() == Min.getBitWidth() &&
158  Known.getBitWidth() == Max.getBitWidth() &&
159  "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
160  APInt UnknownBits = ~(Known.Zero|Known.One);
161 
162  // The minimum value is when the unknown bits are all zeros.
163  Min = Known.One;
164  // The maximum value is when the unknown bits are all ones.
165  Max = Known.One|UnknownBits;
166 }
167 
168 /// This is called when we see this pattern:
169 /// cmp pred (load (gep GV, ...)), cmpcst
170 /// where GV is a global variable with a constant initializer. Try to simplify
171 /// this into some simple computation that does not need the load. For example
172 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
173 ///
174 /// If AndCst is non-null, then the loaded value is masked with that constant
175 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
176 Instruction *InstCombiner::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
177  GlobalVariable *GV,
178  CmpInst &ICI,
179  ConstantInt *AndCst) {
180  Constant *Init = GV->getInitializer();
181  if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
182  return nullptr;
183 
184  uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
185  // Don't blow up on huge arrays.
186  if (ArrayElementCount > MaxArraySizeForCombine)
187  return nullptr;
188 
189  // There are many forms of this optimization we can handle, for now, just do
190  // the simple index into a single-dimensional array.
191  //
192  // Require: GEP GV, 0, i {{, constant indices}}
193  if (GEP->getNumOperands() < 3 ||
194  !isa<ConstantInt>(GEP->getOperand(1)) ||
195  !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
196  isa<Constant>(GEP->getOperand(2)))
197  return nullptr;
198 
199  // Check that indices after the variable are constants and in-range for the
200  // type they index. Collect the indices. This is typically for arrays of
201  // structs.
202  SmallVector<unsigned, 4> LaterIndices;
203 
204  Type *EltTy = Init->getType()->getArrayElementType();
205  for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
206  ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
207  if (!Idx) return nullptr; // Variable index.
208 
209  uint64_t IdxVal = Idx->getZExtValue();
210  if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
211 
212  if (StructType *STy = dyn_cast<StructType>(EltTy))
213  EltTy = STy->getElementType(IdxVal);
214  else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
215  if (IdxVal >= ATy->getNumElements()) return nullptr;
216  EltTy = ATy->getElementType();
217  } else {
218  return nullptr; // Unknown type.
219  }
220 
221  LaterIndices.push_back(IdxVal);
222  }
223 
224  enum { Overdefined = -3, Undefined = -2 };
225 
226  // Variables for our state machines.
227 
228  // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
229  // "i == 47 | i == 87", where 47 is the first index the condition is true for,
230  // and 87 is the second (and last) index. FirstTrueElement is -2 when
231  // undefined, otherwise set to the first true element. SecondTrueElement is
232  // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
233  int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
234 
235  // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
236  // form "i != 47 & i != 87". Same state transitions as for true elements.
237  int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
238 
239  /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
240  /// define a state machine that triggers for ranges of values that the index
241  /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
242  /// This is -2 when undefined, -3 when overdefined, and otherwise the last
243  /// index in the range (inclusive). We use -2 for undefined here because we
244  /// use relative comparisons and don't want 0-1 to match -1.
245  int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
246 
247  // MagicBitvector - This is a magic bitvector where we set a bit if the
248  // comparison is true for element 'i'. If there are 64 elements or less in
249  // the array, this will fully represent all the comparison results.
250  uint64_t MagicBitvector = 0;
251 
252  // Scan the array and see if one of our patterns matches.
253  Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
254  for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
255  Constant *Elt = Init->getAggregateElement(i);
256  if (!Elt) return nullptr;
257 
258  // If this is indexing an array of structures, get the structure element.
259  if (!LaterIndices.empty())
260  Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
261 
262  // If the element is masked, handle it.
263  if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
264 
265  // Find out if the comparison would be true or false for the i'th element.
267  CompareRHS, DL, &TLI);
268  // If the result is undef for this element, ignore it.
269  if (isa<UndefValue>(C)) {
270  // Extend range state machines to cover this element in case there is an
271  // undef in the middle of the range.
272  if (TrueRangeEnd == (int)i-1)
273  TrueRangeEnd = i;
274  if (FalseRangeEnd == (int)i-1)
275  FalseRangeEnd = i;
276  continue;
277  }
278 
279  // If we can't compute the result for any of the elements, we have to give
280  // up evaluating the entire conditional.
281  if (!isa<ConstantInt>(C)) return nullptr;
282 
283  // Otherwise, we know if the comparison is true or false for this element,
284  // update our state machines.
285  bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
286 
287  // State machine for single/double/range index comparison.
288  if (IsTrueForElt) {
289  // Update the TrueElement state machine.
290  if (FirstTrueElement == Undefined)
291  FirstTrueElement = TrueRangeEnd = i; // First true element.
292  else {
293  // Update double-compare state machine.
294  if (SecondTrueElement == Undefined)
295  SecondTrueElement = i;
296  else
297  SecondTrueElement = Overdefined;
298 
299  // Update range state machine.
300  if (TrueRangeEnd == (int)i-1)
301  TrueRangeEnd = i;
302  else
303  TrueRangeEnd = Overdefined;
304  }
305  } else {
306  // Update the FalseElement state machine.
307  if (FirstFalseElement == Undefined)
308  FirstFalseElement = FalseRangeEnd = i; // First false element.
309  else {
310  // Update double-compare state machine.
311  if (SecondFalseElement == Undefined)
312  SecondFalseElement = i;
313  else
314  SecondFalseElement = Overdefined;
315 
316  // Update range state machine.
317  if (FalseRangeEnd == (int)i-1)
318  FalseRangeEnd = i;
319  else
320  FalseRangeEnd = Overdefined;
321  }
322  }
323 
324  // If this element is in range, update our magic bitvector.
325  if (i < 64 && IsTrueForElt)
326  MagicBitvector |= 1ULL << i;
327 
328  // If all of our states become overdefined, bail out early. Since the
329  // predicate is expensive, only check it every 8 elements. This is only
330  // really useful for really huge arrays.
331  if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
332  SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
333  FalseRangeEnd == Overdefined)
334  return nullptr;
335  }
336 
337  // Now that we've scanned the entire array, emit our new comparison(s). We
338  // order the state machines in complexity of the generated code.
339  Value *Idx = GEP->getOperand(2);
340 
341  // If the index is larger than the pointer size of the target, truncate the
342  // index down like the GEP would do implicitly. We don't have to do this for
343  // an inbounds GEP because the index can't be out of range.
344  if (!GEP->isInBounds()) {
345  Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
346  unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
347  if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
348  Idx = Builder.CreateTrunc(Idx, IntPtrTy);
349  }
350 
351  // If the comparison is only true for one or two elements, emit direct
352  // comparisons.
353  if (SecondTrueElement != Overdefined) {
354  // None true -> false.
355  if (FirstTrueElement == Undefined)
356  return replaceInstUsesWith(ICI, Builder.getFalse());
357 
358  Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
359 
360  // True for one element -> 'i == 47'.
361  if (SecondTrueElement == Undefined)
362  return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
363 
364  // True for two elements -> 'i == 47 | i == 72'.
365  Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
366  Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
367  Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
368  return BinaryOperator::CreateOr(C1, C2);
369  }
370 
371  // If the comparison is only false for one or two elements, emit direct
372  // comparisons.
373  if (SecondFalseElement != Overdefined) {
374  // None false -> true.
375  if (FirstFalseElement == Undefined)
376  return replaceInstUsesWith(ICI, Builder.getTrue());
377 
378  Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
379 
380  // False for one element -> 'i != 47'.
381  if (SecondFalseElement == Undefined)
382  return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
383 
384  // False for two elements -> 'i != 47 & i != 72'.
385  Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
386  Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
387  Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
388  return BinaryOperator::CreateAnd(C1, C2);
389  }
390 
391  // If the comparison can be replaced with a range comparison for the elements
392  // where it is true, emit the range check.
393  if (TrueRangeEnd != Overdefined) {
394  assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
395 
396  // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
397  if (FirstTrueElement) {
398  Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
399  Idx = Builder.CreateAdd(Idx, Offs);
400  }
401 
402  Value *End = ConstantInt::get(Idx->getType(),
403  TrueRangeEnd-FirstTrueElement+1);
404  return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
405  }
406 
407  // False range check.
408  if (FalseRangeEnd != Overdefined) {
409  assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
410  // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
411  if (FirstFalseElement) {
412  Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
413  Idx = Builder.CreateAdd(Idx, Offs);
414  }
415 
416  Value *End = ConstantInt::get(Idx->getType(),
417  FalseRangeEnd-FirstFalseElement);
418  return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
419  }
420 
421  // If a magic bitvector captures the entire comparison state
422  // of this load, replace it with computation that does:
423  // ((magic_cst >> i) & 1) != 0
424  {
425  Type *Ty = nullptr;
426 
427  // Look for an appropriate type:
428  // - The type of Idx if the magic fits
429  // - The smallest fitting legal type
430  if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
431  Ty = Idx->getType();
432  else
433  Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
434 
435  if (Ty) {
436  Value *V = Builder.CreateIntCast(Idx, Ty, false);
437  V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
438  V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
439  return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
440  }
441  }
442 
443  return nullptr;
444 }
445 
446 /// Return a value that can be used to compare the *offset* implied by a GEP to
447 /// zero. For example, if we have &A[i], we want to return 'i' for
448 /// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
449 /// are involved. The above expression would also be legal to codegen as
450 /// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
451 /// This latter form is less amenable to optimization though, and we are allowed
452 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
453 ///
454 /// If we can't emit an optimized form for this expression, this returns null.
455 ///
457  const DataLayout &DL) {
459 
460  // Check to see if this gep only has a single variable index. If so, and if
461  // any constant indices are a multiple of its scale, then we can compute this
462  // in terms of the scale of the variable index. For example, if the GEP
463  // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
464  // because the expression will cross zero at the same point.
465  unsigned i, e = GEP->getNumOperands();
466  int64_t Offset = 0;
467  for (i = 1; i != e; ++i, ++GTI) {
468  if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
469  // Compute the aggregate offset of constant indices.
470  if (CI->isZero()) continue;
471 
472  // Handle a struct index, which adds its field offset to the pointer.
473  if (StructType *STy = GTI.getStructTypeOrNull()) {
474  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
475  } else {
476  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
477  Offset += Size*CI->getSExtValue();
478  }
479  } else {
480  // Found our variable index.
481  break;
482  }
483  }
484 
485  // If there are no variable indices, we must have a constant offset, just
486  // evaluate it the general way.
487  if (i == e) return nullptr;
488 
489  Value *VariableIdx = GEP->getOperand(i);
490  // Determine the scale factor of the variable element. For example, this is
491  // 4 if the variable index is into an array of i32.
492  uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
493 
494  // Verify that there are no other variable indices. If so, emit the hard way.
495  for (++i, ++GTI; i != e; ++i, ++GTI) {
496  ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
497  if (!CI) return nullptr;
498 
499  // Compute the aggregate offset of constant indices.
500  if (CI->isZero()) continue;
501 
502  // Handle a struct index, which adds its field offset to the pointer.
503  if (StructType *STy = GTI.getStructTypeOrNull()) {
504  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
505  } else {
506  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
507  Offset += Size*CI->getSExtValue();
508  }
509  }
510 
511  // Okay, we know we have a single variable index, which must be a
512  // pointer/array/vector index. If there is no offset, life is simple, return
513  // the index.
514  Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
515  unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
516  if (Offset == 0) {
517  // Cast to intptrty in case a truncation occurs. If an extension is needed,
518  // we don't need to bother extending: the extension won't affect where the
519  // computation crosses zero.
520  if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
521  VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
522  }
523  return VariableIdx;
524  }
525 
526  // Otherwise, there is an index. The computation we will do will be modulo
527  // the pointer size, so get it.
528  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
529 
530  Offset &= PtrSizeMask;
531  VariableScale &= PtrSizeMask;
532 
533  // To do this transformation, any constant index must be a multiple of the
534  // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
535  // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
536  // multiple of the variable scale.
537  int64_t NewOffs = Offset / (int64_t)VariableScale;
538  if (Offset != NewOffs*(int64_t)VariableScale)
539  return nullptr;
540 
541  // Okay, we can do this evaluation. Start by converting the index to intptr.
542  if (VariableIdx->getType() != IntPtrTy)
543  VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
544  true /*Signed*/);
545  Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
546  return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
547 }
548 
549 /// Returns true if we can rewrite Start as a GEP with pointer Base
550 /// and some integer offset. The nodes that need to be re-written
551 /// for this transformation will be added to Explored.
552 static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
553  const DataLayout &DL,
554  SetVector<Value *> &Explored) {
555  SmallVector<Value *, 16> WorkList(1, Start);
556  Explored.insert(Base);
557 
558  // The following traversal gives us an order which can be used
559  // when doing the final transformation. Since in the final
560  // transformation we create the PHI replacement instructions first,
561  // we don't have to get them in any particular order.
562  //
563  // However, for other instructions we will have to traverse the
564  // operands of an instruction first, which means that we have to
565  // do a post-order traversal.
566  while (!WorkList.empty()) {
568 
569  while (!WorkList.empty()) {
570  if (Explored.size() >= 100)
571  return false;
572 
573  Value *V = WorkList.back();
574 
575  if (Explored.count(V) != 0) {
576  WorkList.pop_back();
577  continue;
578  }
579 
580  if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
581  !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
582  // We've found some value that we can't explore which is different from
583  // the base. Therefore we can't do this transformation.
584  return false;
585 
586  if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
587  auto *CI = dyn_cast<CastInst>(V);
588  if (!CI->isNoopCast(DL))
589  return false;
590 
591  if (Explored.count(CI->getOperand(0)) == 0)
592  WorkList.push_back(CI->getOperand(0));
593  }
594 
595  if (auto *GEP = dyn_cast<GEPOperator>(V)) {
596  // We're limiting the GEP to having one index. This will preserve
597  // the original pointer type. We could handle more cases in the
598  // future.
599  if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
600  GEP->getType() != Start->getType())
601  return false;
602 
603  if (Explored.count(GEP->getOperand(0)) == 0)
604  WorkList.push_back(GEP->getOperand(0));
605  }
606 
607  if (WorkList.back() == V) {
608  WorkList.pop_back();
609  // We've finished visiting this node, mark it as such.
610  Explored.insert(V);
611  }
612 
613  if (auto *PN = dyn_cast<PHINode>(V)) {
614  // We cannot transform PHIs on unsplittable basic blocks.
615  if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
616  return false;
617  Explored.insert(PN);
618  PHIs.insert(PN);
619  }
620  }
621 
622  // Explore the PHI nodes further.
623  for (auto *PN : PHIs)
624  for (Value *Op : PN->incoming_values())
625  if (Explored.count(Op) == 0)
626  WorkList.push_back(Op);
627  }
628 
629  // Make sure that we can do this. Since we can't insert GEPs in a basic
630  // block before a PHI node, we can't easily do this transformation if
631  // we have PHI node users of transformed instructions.
632  for (Value *Val : Explored) {
633  for (Value *Use : Val->uses()) {
634 
635  auto *PHI = dyn_cast<PHINode>(Use);
636  auto *Inst = dyn_cast<Instruction>(Val);
637 
638  if (Inst == Base || Inst == PHI || !Inst || !PHI ||
639  Explored.count(PHI) == 0)
640  continue;
641 
642  if (PHI->getParent() == Inst->getParent())
643  return false;
644  }
645  }
646  return true;
647 }
648 
649 // Sets the appropriate insert point on Builder where we can add
650 // a replacement Instruction for V (if that is possible).
651 static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
652  bool Before = true) {
653  if (auto *PHI = dyn_cast<PHINode>(V)) {
654  Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
655  return;
656  }
657  if (auto *I = dyn_cast<Instruction>(V)) {
658  if (!Before)
659  I = &*std::next(I->getIterator());
660  Builder.SetInsertPoint(I);
661  return;
662  }
663  if (auto *A = dyn_cast<Argument>(V)) {
664  // Set the insertion point in the entry block.
665  BasicBlock &Entry = A->getParent()->getEntryBlock();
666  Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
667  return;
668  }
669  // Otherwise, this is a constant and we don't need to set a new
670  // insertion point.
671  assert(isa<Constant>(V) && "Setting insertion point for unknown value!");
672 }
673 
674 /// Returns a re-written value of Start as an indexed GEP using Base as a
675 /// pointer.
677  const DataLayout &DL,
678  SetVector<Value *> &Explored) {
679  // Perform all the substitutions. This is a bit tricky because we can
680  // have cycles in our use-def chains.
681  // 1. Create the PHI nodes without any incoming values.
682  // 2. Create all the other values.
683  // 3. Add the edges for the PHI nodes.
684  // 4. Emit GEPs to get the original pointers.
685  // 5. Remove the original instructions.
686  Type *IndexType = IntegerType::get(
687  Base->getContext(), DL.getPointerTypeSizeInBits(Start->getType()));
688 
690  NewInsts[Base] = ConstantInt::getNullValue(IndexType);
691 
692  // Create the new PHI nodes, without adding any incoming values.
693  for (Value *Val : Explored) {
694  if (Val == Base)
695  continue;
696  // Create empty phi nodes. This avoids cyclic dependencies when creating
697  // the remaining instructions.
698  if (auto *PHI = dyn_cast<PHINode>(Val))
699  NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
700  PHI->getName() + ".idx", PHI);
701  }
702  IRBuilder<> Builder(Base->getContext());
703 
704  // Create all the other instructions.
705  for (Value *Val : Explored) {
706 
707  if (NewInsts.find(Val) != NewInsts.end())
708  continue;
709 
710  if (auto *CI = dyn_cast<CastInst>(Val)) {
711  NewInsts[CI] = NewInsts[CI->getOperand(0)];
712  continue;
713  }
714  if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
715  Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
716  : GEP->getOperand(1);
717  setInsertionPoint(Builder, GEP);
718  // Indices might need to be sign extended. GEPs will magically do
719  // this, but we need to do it ourselves here.
720  if (Index->getType()->getScalarSizeInBits() !=
721  NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
722  Index = Builder.CreateSExtOrTrunc(
723  Index, NewInsts[GEP->getOperand(0)]->getType(),
724  GEP->getOperand(0)->getName() + ".sext");
725  }
726 
727  auto *Op = NewInsts[GEP->getOperand(0)];
728  if (isa<ConstantInt>(Op) && dyn_cast<ConstantInt>(Op)->isZero())
729  NewInsts[GEP] = Index;
730  else
731  NewInsts[GEP] = Builder.CreateNSWAdd(
732  Op, Index, GEP->getOperand(0)->getName() + ".add");
733  continue;
734  }
735  if (isa<PHINode>(Val))
736  continue;
737 
738  llvm_unreachable("Unexpected instruction type");
739  }
740 
741  // Add the incoming values to the PHI nodes.
742  for (Value *Val : Explored) {
743  if (Val == Base)
744  continue;
745  // All the instructions have been created, we can now add edges to the
746  // phi nodes.
747  if (auto *PHI = dyn_cast<PHINode>(Val)) {
748  PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
749  for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
750  Value *NewIncoming = PHI->getIncomingValue(I);
751 
752  if (NewInsts.find(NewIncoming) != NewInsts.end())
753  NewIncoming = NewInsts[NewIncoming];
754 
755  NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
756  }
757  }
758  }
759 
760  for (Value *Val : Explored) {
761  if (Val == Base)
762  continue;
763 
764  // Depending on the type, for external users we have to emit
765  // a GEP or a GEP + ptrtoint.
766  setInsertionPoint(Builder, Val, false);
767 
768  // If required, create an inttoptr instruction for Base.
769  Value *NewBase = Base;
770  if (!Base->getType()->isPointerTy())
771  NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
772  Start->getName() + "to.ptr");
773 
774  Value *GEP = Builder.CreateInBoundsGEP(
775  Start->getType()->getPointerElementType(), NewBase,
776  makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
777 
778  if (!Val->getType()->isPointerTy()) {
779  Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
780  Val->getName() + ".conv");
781  GEP = Cast;
782  }
783  Val->replaceAllUsesWith(GEP);
784  }
785 
786  return NewInsts[Start];
787 }
788 
789 /// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
790 /// the input Value as a constant indexed GEP. Returns a pair containing
791 /// the GEPs Pointer and Index.
792 static std::pair<Value *, Value *>
794  Type *IndexType = IntegerType::get(V->getContext(),
796 
797  Constant *Index = ConstantInt::getNullValue(IndexType);
798  while (true) {
799  if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
800  // We accept only inbouds GEPs here to exclude the possibility of
801  // overflow.
802  if (!GEP->isInBounds())
803  break;
804  if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
805  GEP->getType() == V->getType()) {
806  V = GEP->getOperand(0);
807  Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
808  Index = ConstantExpr::getAdd(
809  Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
810  continue;
811  }
812  break;
813  }
814  if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
815  if (!CI->isNoopCast(DL))
816  break;
817  V = CI->getOperand(0);
818  continue;
819  }
820  if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
821  if (!CI->isNoopCast(DL))
822  break;
823  V = CI->getOperand(0);
824  continue;
825  }
826  break;
827  }
828  return {V, Index};
829 }
830 
831 /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
832 /// We can look through PHIs, GEPs and casts in order to determine a common base
833 /// between GEPLHS and RHS.
835  ICmpInst::Predicate Cond,
836  const DataLayout &DL) {
837  if (!GEPLHS->hasAllConstantIndices())
838  return nullptr;
839 
840  // Make sure the pointers have the same type.
841  if (GEPLHS->getType() != RHS->getType())
842  return nullptr;
843 
844  Value *PtrBase, *Index;
845  std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
846 
847  // The set of nodes that will take part in this transformation.
848  SetVector<Value *> Nodes;
849 
850  if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
851  return nullptr;
852 
853  // We know we can re-write this as
854  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
855  // Since we've only looked through inbouds GEPs we know that we
856  // can't have overflow on either side. We can therefore re-write
857  // this as:
858  // OFFSET1 cmp OFFSET2
859  Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
860 
861  // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
862  // GEP having PtrBase as the pointer base, and has returned in NewRHS the
863  // offset. Since Index is the offset of LHS to the base pointer, we will now
864  // compare the offsets instead of comparing the pointers.
865  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
866 }
867 
868 /// Fold comparisons between a GEP instruction and something else. At this point
869 /// we know that the GEP is on the LHS of the comparison.
870 Instruction *InstCombiner::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
871  ICmpInst::Predicate Cond,
872  Instruction &I) {
873  // Don't transform signed compares of GEPs into index compares. Even if the
874  // GEP is inbounds, the final add of the base pointer can have signed overflow
875  // and would change the result of the icmp.
876  // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
877  // the maximum signed value for the pointer type.
878  if (ICmpInst::isSigned(Cond))
879  return nullptr;
880 
881  // Look through bitcasts and addrspacecasts. We do not however want to remove
882  // 0 GEPs.
883  if (!isa<GetElementPtrInst>(RHS))
884  RHS = RHS->stripPointerCasts();
885 
886  Value *PtrBase = GEPLHS->getOperand(0);
887  if (PtrBase == RHS && GEPLHS->isInBounds()) {
888  // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
889  // This transformation (ignoring the base and scales) is valid because we
890  // know pointers can't overflow since the gep is inbounds. See if we can
891  // output an optimized form.
892  Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
893 
894  // If not, synthesize the offset the hard way.
895  if (!Offset)
896  Offset = EmitGEPOffset(GEPLHS);
897  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
898  Constant::getNullValue(Offset->getType()));
899  } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
900  // If the base pointers are different, but the indices are the same, just
901  // compare the base pointer.
902  if (PtrBase != GEPRHS->getOperand(0)) {
903  bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
904  IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
905  GEPRHS->getOperand(0)->getType();
906  if (IndicesTheSame)
907  for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
908  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
909  IndicesTheSame = false;
910  break;
911  }
912 
913  // If all indices are the same, just compare the base pointers.
914  if (IndicesTheSame)
915  return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
916 
917  // If we're comparing GEPs with two base pointers that only differ in type
918  // and both GEPs have only constant indices or just one use, then fold
919  // the compare with the adjusted indices.
920  if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
921  (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
922  (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
923  PtrBase->stripPointerCasts() ==
924  GEPRHS->getOperand(0)->stripPointerCasts()) {
925  Value *LOffset = EmitGEPOffset(GEPLHS);
926  Value *ROffset = EmitGEPOffset(GEPRHS);
927 
928  // If we looked through an addrspacecast between different sized address
929  // spaces, the LHS and RHS pointers are different sized
930  // integers. Truncate to the smaller one.
931  Type *LHSIndexTy = LOffset->getType();
932  Type *RHSIndexTy = ROffset->getType();
933  if (LHSIndexTy != RHSIndexTy) {
934  if (LHSIndexTy->getPrimitiveSizeInBits() <
935  RHSIndexTy->getPrimitiveSizeInBits()) {
936  ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
937  } else
938  LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
939  }
940 
941  Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
942  LOffset, ROffset);
943  return replaceInstUsesWith(I, Cmp);
944  }
945 
946  // Otherwise, the base pointers are different and the indices are
947  // different. Try convert this to an indexed compare by looking through
948  // PHIs/casts.
949  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
950  }
951 
952  // If one of the GEPs has all zero indices, recurse.
953  if (GEPLHS->hasAllZeroIndices())
954  return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
956 
957  // If the other GEP has all zero indices, recurse.
958  if (GEPRHS->hasAllZeroIndices())
959  return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
960 
961  bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
962  if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
963  // If the GEPs only differ by one index, compare it.
964  unsigned NumDifferences = 0; // Keep track of # differences.
965  unsigned DiffOperand = 0; // The operand that differs.
966  for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
967  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
968  if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
969  GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
970  // Irreconcilable differences.
971  NumDifferences = 2;
972  break;
973  } else {
974  if (NumDifferences++) break;
975  DiffOperand = i;
976  }
977  }
978 
979  if (NumDifferences == 0) // SAME GEP?
980  return replaceInstUsesWith(I, // No comparison is needed here.
981  Builder.getInt1(ICmpInst::isTrueWhenEqual(Cond)));
982 
983  else if (NumDifferences == 1 && GEPsInBounds) {
984  Value *LHSV = GEPLHS->getOperand(DiffOperand);
985  Value *RHSV = GEPRHS->getOperand(DiffOperand);
986  // Make sure we do a signed comparison here.
987  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
988  }
989  }
990 
991  // Only lower this if the icmp is the only user of the GEP or if we expect
992  // the result to fold to a constant!
993  if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
994  (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
995  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
996  Value *L = EmitGEPOffset(GEPLHS);
997  Value *R = EmitGEPOffset(GEPRHS);
998  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
999  }
1000  }
1001 
1002  // Try convert this to an indexed compare by looking through PHIs/casts as a
1003  // last resort.
1004  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1005 }
1006 
1007 Instruction *InstCombiner::foldAllocaCmp(ICmpInst &ICI,
1008  const AllocaInst *Alloca,
1009  const Value *Other) {
1010  assert(ICI.isEquality() && "Cannot fold non-equality comparison.");
1011 
1012  // It would be tempting to fold away comparisons between allocas and any
1013  // pointer not based on that alloca (e.g. an argument). However, even
1014  // though such pointers cannot alias, they can still compare equal.
1015  //
1016  // But LLVM doesn't specify where allocas get their memory, so if the alloca
1017  // doesn't escape we can argue that it's impossible to guess its value, and we
1018  // can therefore act as if any such guesses are wrong.
1019  //
1020  // The code below checks that the alloca doesn't escape, and that it's only
1021  // used in a comparison once (the current instruction). The
1022  // single-comparison-use condition ensures that we're trivially folding all
1023  // comparisons against the alloca consistently, and avoids the risk of
1024  // erroneously folding a comparison of the pointer with itself.
1025 
1026  unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1027 
1029  for (const Use &U : Alloca->uses()) {
1030  if (Worklist.size() >= MaxIter)
1031  return nullptr;
1032  Worklist.push_back(&U);
1033  }
1034 
1035  unsigned NumCmps = 0;
1036  while (!Worklist.empty()) {
1037  assert(Worklist.size() <= MaxIter);
1038  const Use *U = Worklist.pop_back_val();
1039  const Value *V = U->getUser();
1040  --MaxIter;
1041 
1042  if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1043  isa<SelectInst>(V)) {
1044  // Track the uses.
1045  } else if (isa<LoadInst>(V)) {
1046  // Loading from the pointer doesn't escape it.
1047  continue;
1048  } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1049  // Storing *to* the pointer is fine, but storing the pointer escapes it.
1050  if (SI->getValueOperand() == U->get())
1051  return nullptr;
1052  continue;
1053  } else if (isa<ICmpInst>(V)) {
1054  if (NumCmps++)
1055  return nullptr; // Found more than one cmp.
1056  continue;
1057  } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1058  switch (Intrin->getIntrinsicID()) {
1059  // These intrinsics don't escape or compare the pointer. Memset is safe
1060  // because we don't allow ptrtoint. Memcpy and memmove are safe because
1061  // we don't allow stores, so src cannot point to V.
1062  case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1063  case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1064  continue;
1065  default:
1066  return nullptr;
1067  }
1068  } else {
1069  return nullptr;
1070  }
1071  for (const Use &U : V->uses()) {
1072  if (Worklist.size() >= MaxIter)
1073  return nullptr;
1074  Worklist.push_back(&U);
1075  }
1076  }
1077 
1078  Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1079  return replaceInstUsesWith(
1080  ICI,
1082 }
1083 
1084 /// Fold "icmp pred (X+CI), X".
1085 Instruction *InstCombiner::foldICmpAddOpConst(Value *X, ConstantInt *CI,
1086  ICmpInst::Predicate Pred) {
1087  // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1088  // so the values can never be equal. Similarly for all other "or equals"
1089  // operators.
1090 
1091  // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1092  // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1093  // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1094  if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1095  Value *R =
1097  return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1098  }
1099 
1100  // (X+1) >u X --> X <u (0-1) --> X != 255
1101  // (X+2) >u X --> X <u (0-2) --> X <u 254
1102  // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1103  if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1104  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
1105 
1106  unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
1108  APInt::getSignedMaxValue(BitWidth));
1109 
1110  // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1111  // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1112  // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1113  // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1114  // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1115  // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1116  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1117  return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
1118 
1119  // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1120  // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1121  // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1122  // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1123  // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1124  // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1125 
1126  assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
1127  Constant *C = Builder.getInt(CI->getValue() - 1);
1128  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
1129 }
1130 
1131 /// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1132 /// (icmp eq/ne A, Log2(AP2/AP1)) ->
1133 /// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1134 Instruction *InstCombiner::foldICmpShrConstConst(ICmpInst &I, Value *A,
1135  const APInt &AP1,
1136  const APInt &AP2) {
1137  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1138 
1139  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1140  if (I.getPredicate() == I.ICMP_NE)
1141  Pred = CmpInst::getInversePredicate(Pred);
1142  return new ICmpInst(Pred, LHS, RHS);
1143  };
1144 
1145  // Don't bother doing any work for cases which InstSimplify handles.
1146  if (AP2.isNullValue())
1147  return nullptr;
1148 
1149  bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1150  if (IsAShr) {
1151  if (AP2.isAllOnesValue())
1152  return nullptr;
1153  if (AP2.isNegative() != AP1.isNegative())
1154  return nullptr;
1155  if (AP2.sgt(AP1))
1156  return nullptr;
1157  }
1158 
1159  if (!AP1)
1160  // 'A' must be large enough to shift out the highest set bit.
1161  return getICmp(I.ICMP_UGT, A,
1162  ConstantInt::get(A->getType(), AP2.logBase2()));
1163 
1164  if (AP1 == AP2)
1165  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1166 
1167  int Shift;
1168  if (IsAShr && AP1.isNegative())
1169  Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1170  else
1171  Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1172 
1173  if (Shift > 0) {
1174  if (IsAShr && AP1 == AP2.ashr(Shift)) {
1175  // There are multiple solutions if we are comparing against -1 and the LHS
1176  // of the ashr is not a power of two.
1177  if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1178  return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1179  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1180  } else if (AP1 == AP2.lshr(Shift)) {
1181  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1182  }
1183  }
1184 
1185  // Shifting const2 will never be equal to const1.
1186  // FIXME: This should always be handled by InstSimplify?
1187  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1188  return replaceInstUsesWith(I, TorF);
1189 }
1190 
1191 /// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1192 /// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1193 Instruction *InstCombiner::foldICmpShlConstConst(ICmpInst &I, Value *A,
1194  const APInt &AP1,
1195  const APInt &AP2) {
1196  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1197 
1198  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1199  if (I.getPredicate() == I.ICMP_NE)
1200  Pred = CmpInst::getInversePredicate(Pred);
1201  return new ICmpInst(Pred, LHS, RHS);
1202  };
1203 
1204  // Don't bother doing any work for cases which InstSimplify handles.
1205  if (AP2.isNullValue())
1206  return nullptr;
1207 
1208  unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1209 
1210  if (!AP1 && AP2TrailingZeros != 0)
1211  return getICmp(
1212  I.ICMP_UGE, A,
1213  ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1214 
1215  if (AP1 == AP2)
1216  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1217 
1218  // Get the distance between the lowest bits that are set.
1219  int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1220 
1221  if (Shift > 0 && AP2.shl(Shift) == AP1)
1222  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1223 
1224  // Shifting const2 will never be equal to const1.
1225  // FIXME: This should always be handled by InstSimplify?
1226  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1227  return replaceInstUsesWith(I, TorF);
1228 }
1229 
1230 /// The caller has matched a pattern of the form:
1231 /// I = icmp ugt (add (add A, B), CI2), CI1
1232 /// If this is of the form:
1233 /// sum = a + b
1234 /// if (sum+128 >u 255)
1235 /// Then replace it with llvm.sadd.with.overflow.i8.
1236 ///
1238  ConstantInt *CI2, ConstantInt *CI1,
1239  InstCombiner &IC) {
1240  // The transformation we're trying to do here is to transform this into an
1241  // llvm.sadd.with.overflow. To do this, we have to replace the original add
1242  // with a narrower add, and discard the add-with-constant that is part of the
1243  // range check (if we can't eliminate it, this isn't profitable).
1244 
1245  // In order to eliminate the add-with-constant, the compare can be its only
1246  // use.
1247  Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1248  if (!AddWithCst->hasOneUse())
1249  return nullptr;
1250 
1251  // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1252  if (!CI2->getValue().isPowerOf2())
1253  return nullptr;
1254  unsigned NewWidth = CI2->getValue().countTrailingZeros();
1255  if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1256  return nullptr;
1257 
1258  // The width of the new add formed is 1 more than the bias.
1259  ++NewWidth;
1260 
1261  // Check to see that CI1 is an all-ones value with NewWidth bits.
1262  if (CI1->getBitWidth() == NewWidth ||
1263  CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1264  return nullptr;
1265 
1266  // This is only really a signed overflow check if the inputs have been
1267  // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1268  // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1269  unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1270  if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1271  IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1272  return nullptr;
1273 
1274  // In order to replace the original add with a narrower
1275  // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1276  // and truncates that discard the high bits of the add. Verify that this is
1277  // the case.
1278  Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1279  for (User *U : OrigAdd->users()) {
1280  if (U == AddWithCst)
1281  continue;
1282 
1283  // Only accept truncates for now. We would really like a nice recursive
1284  // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1285  // chain to see which bits of a value are actually demanded. If the
1286  // original add had another add which was then immediately truncated, we
1287  // could still do the transformation.
1288  TruncInst *TI = dyn_cast<TruncInst>(U);
1289  if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1290  return nullptr;
1291  }
1292 
1293  // If the pattern matches, truncate the inputs to the narrower type and
1294  // use the sadd_with_overflow intrinsic to efficiently compute both the
1295  // result and the overflow bit.
1296  Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1298  Intrinsic::sadd_with_overflow, NewType);
1299 
1300  InstCombiner::BuilderTy &Builder = IC.Builder;
1301 
1302  // Put the new code above the original add, in case there are any uses of the
1303  // add between the add and the compare.
1304  Builder.SetInsertPoint(OrigAdd);
1305 
1306  Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
1307  Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
1308  CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
1309  Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
1310  Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
1311 
1312  // The inner add was the result of the narrow add, zero extended to the
1313  // wider type. Replace it with the result computed by the intrinsic.
1314  IC.replaceInstUsesWith(*OrigAdd, ZExt);
1315 
1316  // The original icmp gets replaced with the overflow value.
1317  return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1318 }
1319 
1320 // Handle (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1321 Instruction *InstCombiner::foldICmpWithZero(ICmpInst &Cmp) {
1322  CmpInst::Predicate Pred = Cmp.getPredicate();
1323  Value *X = Cmp.getOperand(0);
1324 
1325  if (match(Cmp.getOperand(1), m_Zero()) && Pred == ICmpInst::ICMP_SGT) {
1326  Value *A, *B;
1327  SelectPatternResult SPR = matchSelectPattern(X, A, B);
1328  if (SPR.Flavor == SPF_SMIN) {
1329  if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
1330  return new ICmpInst(Pred, B, Cmp.getOperand(1));
1331  if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
1332  return new ICmpInst(Pred, A, Cmp.getOperand(1));
1333  }
1334  }
1335  return nullptr;
1336 }
1337 
1338 // Fold icmp Pred X, C.
1339 Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
1340  CmpInst::Predicate Pred = Cmp.getPredicate();
1341  Value *X = Cmp.getOperand(0);
1342 
1343  const APInt *C;
1344  if (!match(Cmp.getOperand(1), m_APInt(C)))
1345  return nullptr;
1346 
1347  Value *A = nullptr, *B = nullptr;
1348 
1349  // Match the following pattern, which is a common idiom when writing
1350  // overflow-safe integer arithmetic functions. The source performs an addition
1351  // in wider type and explicitly checks for overflow using comparisons against
1352  // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1353  //
1354  // TODO: This could probably be generalized to handle other overflow-safe
1355  // operations if we worked out the formulas to compute the appropriate magic
1356  // constants.
1357  //
1358  // sum = a + b
1359  // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1360  {
1361  ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1362  if (Pred == ICmpInst::ICMP_UGT &&
1363  match(X, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1365  Cmp, A, B, CI2, cast<ConstantInt>(Cmp.getOperand(1)), *this))
1366  return Res;
1367  }
1368 
1369  // FIXME: Use m_APInt to allow folds for splat constants.
1370  ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
1371  if (!CI)
1372  return nullptr;
1373 
1374  // Canonicalize icmp instructions based on dominating conditions.
1375  BasicBlock *Parent = Cmp.getParent();
1376  BasicBlock *Dom = Parent->getSinglePredecessor();
1377  auto *BI = Dom ? dyn_cast<BranchInst>(Dom->getTerminator()) : nullptr;
1378  ICmpInst::Predicate Pred2;
1379  BasicBlock *TrueBB, *FalseBB;
1380  ConstantInt *CI2;
1381  if (BI && match(BI, m_Br(m_ICmp(Pred2, m_Specific(X), m_ConstantInt(CI2)),
1382  TrueBB, FalseBB)) &&
1383  TrueBB != FalseBB) {
1384  ConstantRange CR =
1386  ConstantRange DominatingCR =
1387  (Parent == TrueBB)
1390  CmpInst::getInversePredicate(Pred2), CI2->getValue());
1391  ConstantRange Intersection = DominatingCR.intersectWith(CR);
1392  ConstantRange Difference = DominatingCR.difference(CR);
1393  if (Intersection.isEmptySet())
1394  return replaceInstUsesWith(Cmp, Builder.getFalse());
1395  if (Difference.isEmptySet())
1396  return replaceInstUsesWith(Cmp, Builder.getTrue());
1397 
1398  // If this is a normal comparison, it demands all bits. If it is a sign
1399  // bit comparison, it only demands the sign bit.
1400  bool UnusedBit;
1401  bool IsSignBit = isSignBitCheck(Pred, CI->getValue(), UnusedBit);
1402 
1403  // Canonicalizing a sign bit comparison that gets used in a branch,
1404  // pessimizes codegen by generating branch on zero instruction instead
1405  // of a test and branch. So we avoid canonicalizing in such situations
1406  // because test and branch instruction has better branch displacement
1407  // than compare and branch instruction.
1408  if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
1409  return nullptr;
1410 
1411  if (auto *AI = Intersection.getSingleElement())
1412  return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*AI));
1413  if (auto *AD = Difference.getSingleElement())
1414  return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*AD));
1415  }
1416 
1417  return nullptr;
1418 }
1419 
1420 /// Fold icmp (trunc X, Y), C.
1421 Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
1422  TruncInst *Trunc,
1423  const APInt &C) {
1424  ICmpInst::Predicate Pred = Cmp.getPredicate();
1425  Value *X = Trunc->getOperand(0);
1426  if (C.isOneValue() && C.getBitWidth() > 1) {
1427  // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1428  Value *V = nullptr;
1429  if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1430  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1431  ConstantInt::get(V->getType(), 1));
1432  }
1433 
1434  if (Cmp.isEquality() && Trunc->hasOneUse()) {
1435  // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1436  // of the high bits truncated out of x are known.
1437  unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1438  SrcBits = X->getType()->getScalarSizeInBits();
1439  KnownBits Known = computeKnownBits(X, 0, &Cmp);
1440 
1441  // If all the high bits are known, we can do this xform.
1442  if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1443  // Pull in the high bits from known-ones set.
1444  APInt NewRHS = C.zext(SrcBits);
1445  NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1446  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1447  }
1448  }
1449 
1450  return nullptr;
1451 }
1452 
1453 /// Fold icmp (xor X, Y), C.
1454 Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp,
1455  BinaryOperator *Xor,
1456  const APInt &C) {
1457  Value *X = Xor->getOperand(0);
1458  Value *Y = Xor->getOperand(1);
1459  const APInt *XorC;
1460  if (!match(Y, m_APInt(XorC)))
1461  return nullptr;
1462 
1463  // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1464  // fold the xor.
1465  ICmpInst::Predicate Pred = Cmp.getPredicate();
1466  bool TrueIfSigned = false;
1467  if (isSignBitCheck(Cmp.getPredicate(), C, TrueIfSigned)) {
1468 
1469  // If the sign bit of the XorCst is not set, there is no change to
1470  // the operation, just stop using the Xor.
1471  if (!XorC->isNegative()) {
1472  Cmp.setOperand(0, X);
1473  Worklist.Add(Xor);
1474  return &Cmp;
1475  }
1476 
1477  // Emit the opposite comparison.
1478  if (TrueIfSigned)
1479  return new ICmpInst(ICmpInst::ICMP_SGT, X,
1481  else
1482  return new ICmpInst(ICmpInst::ICMP_SLT, X,
1484  }
1485 
1486  if (Xor->hasOneUse()) {
1487  // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1488  if (!Cmp.isEquality() && XorC->isSignMask()) {
1489  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1490  : Cmp.getSignedPredicate();
1491  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1492  }
1493 
1494  // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1495  if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1496  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1497  : Cmp.getSignedPredicate();
1498  Pred = Cmp.getSwappedPredicate(Pred);
1499  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1500  }
1501  }
1502 
1503  // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1504  // iff -C is a power of 2
1505  if (Pred == ICmpInst::ICMP_UGT && *XorC == ~C && (C + 1).isPowerOf2())
1506  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1507 
1508  // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1509  // iff -C is a power of 2
1510  if (Pred == ICmpInst::ICMP_ULT && *XorC == -C && C.isPowerOf2())
1511  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
1512 
1513  return nullptr;
1514 }
1515 
1516 /// Fold icmp (and (sh X, Y), C2), C1.
1517 Instruction *InstCombiner::foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
1518  const APInt &C1, const APInt &C2) {
1519  BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1520  if (!Shift || !Shift->isShift())
1521  return nullptr;
1522 
1523  // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1524  // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1525  // code produced by the clang front-end, for bitfield access.
1526  // This seemingly simple opportunity to fold away a shift turns out to be
1527  // rather complicated. See PR17827 for details.
1528  unsigned ShiftOpcode = Shift->getOpcode();
1529  bool IsShl = ShiftOpcode == Instruction::Shl;
1530  const APInt *C3;
1531  if (match(Shift->getOperand(1), m_APInt(C3))) {
1532  bool CanFold = false;
1533  if (ShiftOpcode == Instruction::Shl) {
1534  // For a left shift, we can fold if the comparison is not signed. We can
1535  // also fold a signed comparison if the mask value and comparison value
1536  // are not negative. These constraints may not be obvious, but we can
1537  // prove that they are correct using an SMT solver.
1538  if (!Cmp.isSigned() || (!C2.isNegative() && !C1.isNegative()))
1539  CanFold = true;
1540  } else {
1541  bool IsAshr = ShiftOpcode == Instruction::AShr;
1542  // For a logical right shift, we can fold if the comparison is not signed.
1543  // We can also fold a signed comparison if the shifted mask value and the
1544  // shifted comparison value are not negative. These constraints may not be
1545  // obvious, but we can prove that they are correct using an SMT solver.
1546  // For an arithmetic shift right we can do the same, if we ensure
1547  // the And doesn't use any bits being shifted in. Normally these would
1548  // be turned into lshr by SimplifyDemandedBits, but not if there is an
1549  // additional user.
1550  if (!IsAshr || (C2.shl(*C3).lshr(*C3) == C2)) {
1551  if (!Cmp.isSigned() ||
1552  (!C2.shl(*C3).isNegative() && !C1.shl(*C3).isNegative()))
1553  CanFold = true;
1554  }
1555  }
1556 
1557  if (CanFold) {
1558  APInt NewCst = IsShl ? C1.lshr(*C3) : C1.shl(*C3);
1559  APInt SameAsC1 = IsShl ? NewCst.shl(*C3) : NewCst.lshr(*C3);
1560  // Check to see if we are shifting out any of the bits being compared.
1561  if (SameAsC1 != C1) {
1562  // If we shifted bits out, the fold is not going to work out. As a
1563  // special case, check to see if this means that the result is always
1564  // true or false now.
1565  if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1566  return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1567  if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1568  return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1569  } else {
1570  Cmp.setOperand(1, ConstantInt::get(And->getType(), NewCst));
1571  APInt NewAndCst = IsShl ? C2.lshr(*C3) : C2.shl(*C3);
1572  And->setOperand(1, ConstantInt::get(And->getType(), NewAndCst));
1573  And->setOperand(0, Shift->getOperand(0));
1574  Worklist.Add(Shift); // Shift is dead.
1575  return &Cmp;
1576  }
1577  }
1578  }
1579 
1580  // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1581  // preferable because it allows the C2 << Y expression to be hoisted out of a
1582  // loop if Y is invariant and X is not.
1583  if (Shift->hasOneUse() && C1.isNullValue() && Cmp.isEquality() &&
1584  !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1585  // Compute C2 << Y.
1586  Value *NewShift =
1587  IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
1588  : Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
1589 
1590  // Compute X & (C2 << Y).
1591  Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
1592  Cmp.setOperand(0, NewAnd);
1593  return &Cmp;
1594  }
1595 
1596  return nullptr;
1597 }
1598 
1599 /// Fold icmp (and X, C2), C1.
1600 Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
1601  BinaryOperator *And,
1602  const APInt &C1) {
1603  const APInt *C2;
1604  if (!match(And->getOperand(1), m_APInt(C2)))
1605  return nullptr;
1606 
1607  if (!And->hasOneUse())
1608  return nullptr;
1609 
1610  // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1611  // the input width without changing the value produced, eliminate the cast:
1612  //
1613  // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1614  //
1615  // We can do this transformation if the constants do not have their sign bits
1616  // set or if it is an equality comparison. Extending a relational comparison
1617  // when we're checking the sign bit would not work.
1618  Value *W;
1619  if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
1620  (Cmp.isEquality() || (!C1.isNegative() && !C2->isNegative()))) {
1621  // TODO: Is this a good transform for vectors? Wider types may reduce
1622  // throughput. Should this transform be limited (even for scalars) by using
1623  // shouldChangeType()?
1624  if (!Cmp.getType()->isVectorTy()) {
1625  Type *WideType = W->getType();
1626  unsigned WideScalarBits = WideType->getScalarSizeInBits();
1627  Constant *ZextC1 = ConstantInt::get(WideType, C1.zext(WideScalarBits));
1628  Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1629  Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
1630  return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1631  }
1632  }
1633 
1634  if (Instruction *I = foldICmpAndShift(Cmp, And, C1, *C2))
1635  return I;
1636 
1637  // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1638  // (icmp pred (and A, (or (shl 1, B), 1), 0))
1639  //
1640  // iff pred isn't signed
1641  if (!Cmp.isSigned() && C1.isNullValue() && And->getOperand(0)->hasOneUse() &&
1642  match(And->getOperand(1), m_One())) {
1643  Constant *One = cast<Constant>(And->getOperand(1));
1644  Value *Or = And->getOperand(0);
1645  Value *A, *B, *LShr;
1646  if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1647  match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1648  unsigned UsesRemoved = 0;
1649  if (And->hasOneUse())
1650  ++UsesRemoved;
1651  if (Or->hasOneUse())
1652  ++UsesRemoved;
1653  if (LShr->hasOneUse())
1654  ++UsesRemoved;
1655 
1656  // Compute A & ((1 << B) | 1)
1657  Value *NewOr = nullptr;
1658  if (auto *C = dyn_cast<Constant>(B)) {
1659  if (UsesRemoved >= 1)
1660  NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1661  } else {
1662  if (UsesRemoved >= 3)
1663  NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
1664  /*HasNUW=*/true),
1665  One, Or->getName());
1666  }
1667  if (NewOr) {
1668  Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
1669  Cmp.setOperand(0, NewAnd);
1670  return &Cmp;
1671  }
1672  }
1673  }
1674 
1675  return nullptr;
1676 }
1677 
1678 /// Fold icmp (and X, Y), C.
1679 Instruction *InstCombiner::foldICmpAndConstant(ICmpInst &Cmp,
1680  BinaryOperator *And,
1681  const APInt &C) {
1682  if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1683  return I;
1684 
1685  // TODO: These all require that Y is constant too, so refactor with the above.
1686 
1687  // Try to optimize things like "A[i] & 42 == 0" to index computations.
1688  Value *X = And->getOperand(0);
1689  Value *Y = And->getOperand(1);
1690  if (auto *LI = dyn_cast<LoadInst>(X))
1691  if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1692  if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1693  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1694  !LI->isVolatile() && isa<ConstantInt>(Y)) {
1695  ConstantInt *C2 = cast<ConstantInt>(Y);
1696  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1697  return Res;
1698  }
1699 
1700  if (!Cmp.isEquality())
1701  return nullptr;
1702 
1703  // X & -C == -C -> X > u ~C
1704  // X & -C != -C -> X <= u ~C
1705  // iff C is a power of 2
1706  if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
1707  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
1709  return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1710  }
1711 
1712  // (X & C2) == 0 -> (trunc X) >= 0
1713  // (X & C2) != 0 -> (trunc X) < 0
1714  // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1715  const APInt *C2;
1716  if (And->hasOneUse() && C.isNullValue() && match(Y, m_APInt(C2))) {
1717  int32_t ExactLogBase2 = C2->exactLogBase2();
1718  if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1719  Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1720  if (And->getType()->isVectorTy())
1721  NTy = VectorType::get(NTy, And->getType()->getVectorNumElements());
1722  Value *Trunc = Builder.CreateTrunc(X, NTy);
1723  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
1725  return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1726  }
1727  }
1728 
1729  return nullptr;
1730 }
1731 
1732 /// Fold icmp (or X, Y), C.
1733 Instruction *InstCombiner::foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
1734  const APInt &C) {
1735  ICmpInst::Predicate Pred = Cmp.getPredicate();
1736  if (C.isOneValue()) {
1737  // icmp slt signum(V) 1 --> icmp slt V, 1
1738  Value *V = nullptr;
1739  if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1740  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1741  ConstantInt::get(V->getType(), 1));
1742  }
1743 
1744  // X | C == C --> X <=u C
1745  // X | C != C --> X >u C
1746  // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1747  if (Cmp.isEquality() && Cmp.getOperand(1) == Or->getOperand(1) &&
1748  (C + 1).isPowerOf2()) {
1750  return new ICmpInst(Pred, Or->getOperand(0), Or->getOperand(1));
1751  }
1752 
1753  if (!Cmp.isEquality() || !C.isNullValue() || !Or->hasOneUse())
1754  return nullptr;
1755 
1756  Value *P, *Q;
1757  if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1758  // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1759  // -> and (icmp eq P, null), (icmp eq Q, null).
1760  Value *CmpP =
1761  Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1762  Value *CmpQ =
1763  Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1764  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1765  return BinaryOperator::Create(BOpc, CmpP, CmpQ);
1766  }
1767 
1768  // Are we using xors to bitwise check for a pair of (in)equalities? Convert to
1769  // a shorter form that has more potential to be folded even further.
1770  Value *X1, *X2, *X3, *X4;
1771  if (match(Or->getOperand(0), m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
1772  match(Or->getOperand(1), m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
1773  // ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
1774  // ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
1775  Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
1776  Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
1777  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1778  return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
1779  }
1780 
1781  return nullptr;
1782 }
1783 
1784 /// Fold icmp (mul X, Y), C.
1785 Instruction *InstCombiner::foldICmpMulConstant(ICmpInst &Cmp,
1786  BinaryOperator *Mul,
1787  const APInt &C) {
1788  const APInt *MulC;
1789  if (!match(Mul->getOperand(1), m_APInt(MulC)))
1790  return nullptr;
1791 
1792  // If this is a test of the sign bit and the multiply is sign-preserving with
1793  // a constant operand, use the multiply LHS operand instead.
1794  ICmpInst::Predicate Pred = Cmp.getPredicate();
1795  if (isSignTest(Pred, C) && Mul->hasNoSignedWrap()) {
1796  if (MulC->isNegative())
1797  Pred = ICmpInst::getSwappedPredicate(Pred);
1798  return new ICmpInst(Pred, Mul->getOperand(0),
1800  }
1801 
1802  return nullptr;
1803 }
1804 
1805 /// Fold icmp (shl 1, Y), C.
1807  const APInt &C) {
1808  Value *Y;
1809  if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
1810  return nullptr;
1811 
1812  Type *ShiftType = Shl->getType();
1813  unsigned TypeBits = C.getBitWidth();
1814  bool CIsPowerOf2 = C.isPowerOf2();
1815  ICmpInst::Predicate Pred = Cmp.getPredicate();
1816  if (Cmp.isUnsigned()) {
1817  // (1 << Y) pred C -> Y pred Log2(C)
1818  if (!CIsPowerOf2) {
1819  // (1 << Y) < 30 -> Y <= 4
1820  // (1 << Y) <= 30 -> Y <= 4
1821  // (1 << Y) >= 30 -> Y > 4
1822  // (1 << Y) > 30 -> Y > 4
1823  if (Pred == ICmpInst::ICMP_ULT)
1824  Pred = ICmpInst::ICMP_ULE;
1825  else if (Pred == ICmpInst::ICMP_UGE)
1826  Pred = ICmpInst::ICMP_UGT;
1827  }
1828 
1829  // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
1830  // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
1831  unsigned CLog2 = C.logBase2();
1832  if (CLog2 == TypeBits - 1) {
1833  if (Pred == ICmpInst::ICMP_UGE)
1834  Pred = ICmpInst::ICMP_EQ;
1835  else if (Pred == ICmpInst::ICMP_ULT)
1836  Pred = ICmpInst::ICMP_NE;
1837  }
1838  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
1839  } else if (Cmp.isSigned()) {
1840  Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
1841  if (C.isAllOnesValue()) {
1842  // (1 << Y) <= -1 -> Y == 31
1843  if (Pred == ICmpInst::ICMP_SLE)
1844  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1845 
1846  // (1 << Y) > -1 -> Y != 31
1847  if (Pred == ICmpInst::ICMP_SGT)
1848  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1849  } else if (!C) {
1850  // (1 << Y) < 0 -> Y == 31
1851  // (1 << Y) <= 0 -> Y == 31
1852  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1853  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1854 
1855  // (1 << Y) >= 0 -> Y != 31
1856  // (1 << Y) > 0 -> Y != 31
1857  if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1858  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1859  }
1860  } else if (Cmp.isEquality() && CIsPowerOf2) {
1861  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C.logBase2()));
1862  }
1863 
1864  return nullptr;
1865 }
1866 
1867 /// Fold icmp (shl X, Y), C.
1868 Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp,
1869  BinaryOperator *Shl,
1870  const APInt &C) {
1871  const APInt *ShiftVal;
1872  if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
1873  return foldICmpShlConstConst(Cmp, Shl->getOperand(1), C, *ShiftVal);
1874 
1875  const APInt *ShiftAmt;
1876  if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
1877  return foldICmpShlOne(Cmp, Shl, C);
1878 
1879  // Check that the shift amount is in range. If not, don't perform undefined
1880  // shifts. When the shift is visited, it will be simplified.
1881  unsigned TypeBits = C.getBitWidth();
1882  if (ShiftAmt->uge(TypeBits))
1883  return nullptr;
1884 
1885  ICmpInst::Predicate Pred = Cmp.getPredicate();
1886  Value *X = Shl->getOperand(0);
1887  Type *ShType = Shl->getType();
1888 
1889  // NSW guarantees that we are only shifting out sign bits from the high bits,
1890  // so we can ASHR the compare constant without needing a mask and eliminate
1891  // the shift.
1892  if (Shl->hasNoSignedWrap()) {
1893  if (Pred == ICmpInst::ICMP_SGT) {
1894  // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
1895  APInt ShiftedC = C.ashr(*ShiftAmt);
1896  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1897  }
1898  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1899  // This is the same code as the SGT case, but assert the pre-condition
1900  // that is needed for this to work with equality predicates.
1901  assert(C.ashr(*ShiftAmt).shl(*ShiftAmt) == C &&
1902  "Compare known true or false was not folded");
1903  APInt ShiftedC = C.ashr(*ShiftAmt);
1904  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1905  }
1906  if (Pred == ICmpInst::ICMP_SLT) {
1907  // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
1908  // (X << S) <=s C is equiv to X <=s (C >> S) for all C
1909  // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
1910  // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
1911  assert(!C.isMinSignedValue() && "Unexpected icmp slt");
1912  APInt ShiftedC = (C - 1).ashr(*ShiftAmt) + 1;
1913  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1914  }
1915  // If this is a signed comparison to 0 and the shift is sign preserving,
1916  // use the shift LHS operand instead; isSignTest may change 'Pred', so only
1917  // do that if we're sure to not continue on in this function.
1918  if (isSignTest(Pred, C))
1919  return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
1920  }
1921 
1922  // NUW guarantees that we are only shifting out zero bits from the high bits,
1923  // so we can LSHR the compare constant without needing a mask and eliminate
1924  // the shift.
1925  if (Shl->hasNoUnsignedWrap()) {
1926  if (Pred == ICmpInst::ICMP_UGT) {
1927  // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
1928  APInt ShiftedC = C.lshr(*ShiftAmt);
1929  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1930  }
1931  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1932  // This is the same code as the UGT case, but assert the pre-condition
1933  // that is needed for this to work with equality predicates.
1934  assert(C.lshr(*ShiftAmt).shl(*ShiftAmt) == C &&
1935  "Compare known true or false was not folded");
1936  APInt ShiftedC = C.lshr(*ShiftAmt);
1937  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1938  }
1939  if (Pred == ICmpInst::ICMP_ULT) {
1940  // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
1941  // (X << S) <=u C is equiv to X <=u (C >> S) for all C
1942  // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
1943  // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
1944  assert(C.ugt(0) && "ult 0 should have been eliminated");
1945  APInt ShiftedC = (C - 1).lshr(*ShiftAmt) + 1;
1946  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1947  }
1948  }
1949 
1950  if (Cmp.isEquality() && Shl->hasOneUse()) {
1951  // Strength-reduce the shift into an 'and'.
1953  ShType,
1954  APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
1955  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1956  Constant *LShrC = ConstantInt::get(ShType, C.lshr(*ShiftAmt));
1957  return new ICmpInst(Pred, And, LShrC);
1958  }
1959 
1960  // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
1961  bool TrueIfSigned = false;
1962  if (Shl->hasOneUse() && isSignBitCheck(Pred, C, TrueIfSigned)) {
1963  // (X << 31) <s 0 --> (X & 1) != 0
1965  ShType,
1966  APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
1967  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1968  return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
1969  And, Constant::getNullValue(ShType));
1970  }
1971 
1972  // Transform (icmp pred iM (shl iM %v, N), C)
1973  // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
1974  // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
1975  // This enables us to get rid of the shift in favor of a trunc that may be
1976  // free on the target. It has the additional benefit of comparing to a
1977  // smaller constant that may be more target-friendly.
1978  unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
1979  if (Shl->hasOneUse() && Amt != 0 && C.countTrailingZeros() >= Amt &&
1980  DL.isLegalInteger(TypeBits - Amt)) {
1981  Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
1982  if (ShType->isVectorTy())
1983  TruncTy = VectorType::get(TruncTy, ShType->getVectorNumElements());
1984  Constant *NewC =
1985  ConstantInt::get(TruncTy, C.ashr(*ShiftAmt).trunc(TypeBits - Amt));
1986  return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
1987  }
1988 
1989  return nullptr;
1990 }
1991 
1992 /// Fold icmp ({al}shr X, Y), C.
1993 Instruction *InstCombiner::foldICmpShrConstant(ICmpInst &Cmp,
1994  BinaryOperator *Shr,
1995  const APInt &C) {
1996  // An exact shr only shifts out zero bits, so:
1997  // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
1998  Value *X = Shr->getOperand(0);
1999  CmpInst::Predicate Pred = Cmp.getPredicate();
2000  if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
2001  C.isNullValue())
2002  return new ICmpInst(Pred, X, Cmp.getOperand(1));
2003 
2004  const APInt *ShiftVal;
2005  if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
2006  return foldICmpShrConstConst(Cmp, Shr->getOperand(1), C, *ShiftVal);
2007 
2008  const APInt *ShiftAmt;
2009  if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2010  return nullptr;
2011 
2012  // Check that the shift amount is in range. If not, don't perform undefined
2013  // shifts. When the shift is visited it will be simplified.
2014  unsigned TypeBits = C.getBitWidth();
2015  unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2016  if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2017  return nullptr;
2018 
2019  bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2020  bool IsExact = Shr->isExact();
2021  Type *ShrTy = Shr->getType();
2022  // TODO: If we could guarantee that InstSimplify would handle all of the
2023  // constant-value-based preconditions in the folds below, then we could assert
2024  // those conditions rather than checking them. This is difficult because of
2025  // undef/poison (PR34838).
2026  if (IsAShr) {
2027  if (Pred == CmpInst::ICMP_SLT || (Pred == CmpInst::ICMP_SGT && IsExact)) {
2028  // icmp slt (ashr X, ShAmtC), C --> icmp slt X, (C << ShAmtC)
2029  // icmp sgt (ashr exact X, ShAmtC), C --> icmp sgt X, (C << ShAmtC)
2030  APInt ShiftedC = C.shl(ShAmtVal);
2031  if (ShiftedC.ashr(ShAmtVal) == C)
2032  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2033  }
2034  if (Pred == CmpInst::ICMP_SGT) {
2035  // icmp sgt (ashr X, ShAmtC), C --> icmp sgt X, ((C + 1) << ShAmtC) - 1
2036  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2037  if (!C.isMaxSignedValue() && !(C + 1).shl(ShAmtVal).isMinSignedValue() &&
2038  (ShiftedC + 1).ashr(ShAmtVal) == (C + 1))
2039  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2040  }
2041  } else {
2042  if (Pred == CmpInst::ICMP_ULT || (Pred == CmpInst::ICMP_UGT && IsExact)) {
2043  // icmp ult (lshr X, ShAmtC), C --> icmp ult X, (C << ShAmtC)
2044  // icmp ugt (lshr exact X, ShAmtC), C --> icmp ugt X, (C << ShAmtC)
2045  APInt ShiftedC = C.shl(ShAmtVal);
2046  if (ShiftedC.lshr(ShAmtVal) == C)
2047  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2048  }
2049  if (Pred == CmpInst::ICMP_UGT) {
2050  // icmp ugt (lshr X, ShAmtC), C --> icmp ugt X, ((C + 1) << ShAmtC) - 1
2051  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2052  if ((ShiftedC + 1).lshr(ShAmtVal) == (C + 1))
2053  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2054  }
2055  }
2056 
2057  if (!Cmp.isEquality())
2058  return nullptr;
2059 
2060  // Handle equality comparisons of shift-by-constant.
2061 
2062  // If the comparison constant changes with the shift, the comparison cannot
2063  // succeed (bits of the comparison constant cannot match the shifted value).
2064  // This should be known by InstSimplify and already be folded to true/false.
2065  assert(((IsAShr && C.shl(ShAmtVal).ashr(ShAmtVal) == C) ||
2066  (!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&
2067  "Expected icmp+shr simplify did not occur.");
2068 
2069  // If the bits shifted out are known zero, compare the unshifted value:
2070  // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2071  if (Shr->isExact())
2072  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, C << ShAmtVal));
2073 
2074  if (Shr->hasOneUse()) {
2075  // Canonicalize the shift into an 'and':
2076  // icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
2077  APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2078  Constant *Mask = ConstantInt::get(ShrTy, Val);
2079  Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
2080  return new ICmpInst(Pred, And, ConstantInt::get(ShrTy, C << ShAmtVal));
2081  }
2082 
2083  return nullptr;
2084 }
2085 
2086 /// Fold icmp (udiv X, Y), C.
2087 Instruction *InstCombiner::foldICmpUDivConstant(ICmpInst &Cmp,
2088  BinaryOperator *UDiv,
2089  const APInt &C) {
2090  const APInt *C2;
2091  if (!match(UDiv->getOperand(0), m_APInt(C2)))
2092  return nullptr;
2093 
2094  assert(*C2 != 0 && "udiv 0, X should have been simplified already.");
2095 
2096  // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2097  Value *Y = UDiv->getOperand(1);
2098  if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2099  assert(!C.isMaxValue() &&
2100  "icmp ugt X, UINT_MAX should have been simplified already.");
2101  return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2102  ConstantInt::get(Y->getType(), C2->udiv(C + 1)));
2103  }
2104 
2105  // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2106  if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2107  assert(C != 0 && "icmp ult X, 0 should have been simplified already.");
2108  return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2109  ConstantInt::get(Y->getType(), C2->udiv(C)));
2110  }
2111 
2112  return nullptr;
2113 }
2114 
2115 /// Fold icmp ({su}div X, Y), C.
2116 Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
2117  BinaryOperator *Div,
2118  const APInt &C) {
2119  // Fold: icmp pred ([us]div X, C2), C -> range test
2120  // Fold this div into the comparison, producing a range check.
2121  // Determine, based on the divide type, what the range is being
2122  // checked. If there is an overflow on the low or high side, remember
2123  // it, otherwise compute the range [low, hi) bounding the new value.
2124  // See: InsertRangeTest above for the kinds of replacements possible.
2125  const APInt *C2;
2126  if (!match(Div->getOperand(1), m_APInt(C2)))
2127  return nullptr;
2128 
2129  // FIXME: If the operand types don't match the type of the divide
2130  // then don't attempt this transform. The code below doesn't have the
2131  // logic to deal with a signed divide and an unsigned compare (and
2132  // vice versa). This is because (x /s C2) <s C produces different
2133  // results than (x /s C2) <u C or (x /u C2) <s C or even
2134  // (x /u C2) <u C. Simply casting the operands and result won't
2135  // work. :( The if statement below tests that condition and bails
2136  // if it finds it.
2137  bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2138  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2139  return nullptr;
2140 
2141  // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2142  // INT_MIN will also fail if the divisor is 1. Although folds of all these
2143  // division-by-constant cases should be present, we can not assert that they
2144  // have happened before we reach this icmp instruction.
2145  if (C2->isNullValue() || C2->isOneValue() ||
2146  (DivIsSigned && C2->isAllOnesValue()))
2147  return nullptr;
2148 
2149  // Compute Prod = C * C2. We are essentially solving an equation of
2150  // form X / C2 = C. We solve for X by multiplying C2 and C.
2151  // By solving for X, we can turn this into a range check instead of computing
2152  // a divide.
2153  APInt Prod = C * *C2;
2154 
2155  // Determine if the product overflows by seeing if the product is not equal to
2156  // the divide. Make sure we do the same kind of divide as in the LHS
2157  // instruction that we're folding.
2158  bool ProdOV = (DivIsSigned ? Prod.sdiv(*C2) : Prod.udiv(*C2)) != C;
2159 
2160  ICmpInst::Predicate Pred = Cmp.getPredicate();
2161 
2162  // If the division is known to be exact, then there is no remainder from the
2163  // divide, so the covered range size is unit, otherwise it is the divisor.
2164  APInt RangeSize = Div->isExact() ? APInt(C2->getBitWidth(), 1) : *C2;
2165 
2166  // Figure out the interval that is being checked. For example, a comparison
2167  // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2168  // Compute this interval based on the constants involved and the signedness of
2169  // the compare/divide. This computes a half-open interval, keeping track of
2170  // whether either value in the interval overflows. After analysis each
2171  // overflow variable is set to 0 if it's corresponding bound variable is valid
2172  // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2173  int LoOverflow = 0, HiOverflow = 0;
2174  APInt LoBound, HiBound;
2175 
2176  if (!DivIsSigned) { // udiv
2177  // e.g. X/5 op 3 --> [15, 20)
2178  LoBound = Prod;
2179  HiOverflow = LoOverflow = ProdOV;
2180  if (!HiOverflow) {
2181  // If this is not an exact divide, then many values in the range collapse
2182  // to the same result value.
2183  HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2184  }
2185  } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
2186  if (C.isNullValue()) { // (X / pos) op 0
2187  // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2188  LoBound = -(RangeSize - 1);
2189  HiBound = RangeSize;
2190  } else if (C.isStrictlyPositive()) { // (X / pos) op pos
2191  LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2192  HiOverflow = LoOverflow = ProdOV;
2193  if (!HiOverflow)
2194  HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2195  } else { // (X / pos) op neg
2196  // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2197  HiBound = Prod + 1;
2198  LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2199  if (!LoOverflow) {
2200  APInt DivNeg = -RangeSize;
2201  LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2202  }
2203  }
2204  } else if (C2->isNegative()) { // Divisor is < 0.
2205  if (Div->isExact())
2206  RangeSize.negate();
2207  if (C.isNullValue()) { // (X / neg) op 0
2208  // e.g. X/-5 op 0 --> [-4, 5)
2209  LoBound = RangeSize + 1;
2210  HiBound = -RangeSize;
2211  if (HiBound == *C2) { // -INTMIN = INTMIN
2212  HiOverflow = 1; // [INTMIN+1, overflow)
2213  HiBound = APInt(); // e.g. X/INTMIN = 0 --> X > INTMIN
2214  }
2215  } else if (C.isStrictlyPositive()) { // (X / neg) op pos
2216  // e.g. X/-5 op 3 --> [-19, -14)
2217  HiBound = Prod + 1;
2218  HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2219  if (!LoOverflow)
2220  LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2221  } else { // (X / neg) op neg
2222  LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2223  LoOverflow = HiOverflow = ProdOV;
2224  if (!HiOverflow)
2225  HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2226  }
2227 
2228  // Dividing by a negative swaps the condition. LT <-> GT
2229  Pred = ICmpInst::getSwappedPredicate(Pred);
2230  }
2231 
2232  Value *X = Div->getOperand(0);
2233  switch (Pred) {
2234  default: llvm_unreachable("Unhandled icmp opcode!");
2235  case ICmpInst::ICMP_EQ:
2236  if (LoOverflow && HiOverflow)
2237  return replaceInstUsesWith(Cmp, Builder.getFalse());
2238  if (HiOverflow)
2239  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2240  ICmpInst::ICMP_UGE, X,
2241  ConstantInt::get(Div->getType(), LoBound));
2242  if (LoOverflow)
2243  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2244  ICmpInst::ICMP_ULT, X,
2245  ConstantInt::get(Div->getType(), HiBound));
2246  return replaceInstUsesWith(
2247  Cmp, insertRangeTest(X, LoBound, HiBound, DivIsSigned, true));
2248  case ICmpInst::ICMP_NE:
2249  if (LoOverflow && HiOverflow)
2250  return replaceInstUsesWith(Cmp, Builder.getTrue());
2251  if (HiOverflow)
2252  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2253  ICmpInst::ICMP_ULT, X,
2254  ConstantInt::get(Div->getType(), LoBound));
2255  if (LoOverflow)
2256  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2257  ICmpInst::ICMP_UGE, X,
2258  ConstantInt::get(Div->getType(), HiBound));
2259  return replaceInstUsesWith(Cmp,
2260  insertRangeTest(X, LoBound, HiBound,
2261  DivIsSigned, false));
2262  case ICmpInst::ICMP_ULT:
2263  case ICmpInst::ICMP_SLT:
2264  if (LoOverflow == +1) // Low bound is greater than input range.
2265  return replaceInstUsesWith(Cmp, Builder.getTrue());
2266  if (LoOverflow == -1) // Low bound is less than input range.
2267  return replaceInstUsesWith(Cmp, Builder.getFalse());
2268  return new ICmpInst(Pred, X, ConstantInt::get(Div->getType(), LoBound));
2269  case ICmpInst::ICMP_UGT:
2270  case ICmpInst::ICMP_SGT:
2271  if (HiOverflow == +1) // High bound greater than input range.
2272  return replaceInstUsesWith(Cmp, Builder.getFalse());
2273  if (HiOverflow == -1) // High bound less than input range.
2274  return replaceInstUsesWith(Cmp, Builder.getTrue());
2275  if (Pred == ICmpInst::ICMP_UGT)
2276  return new ICmpInst(ICmpInst::ICMP_UGE, X,
2277  ConstantInt::get(Div->getType(), HiBound));
2278  return new ICmpInst(ICmpInst::ICMP_SGE, X,
2279  ConstantInt::get(Div->getType(), HiBound));
2280  }
2281 
2282  return nullptr;
2283 }
2284 
2285 /// Fold icmp (sub X, Y), C.
2286 Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
2287  BinaryOperator *Sub,
2288  const APInt &C) {
2289  Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2290  ICmpInst::Predicate Pred = Cmp.getPredicate();
2291 
2292  // The following transforms are only worth it if the only user of the subtract
2293  // is the icmp.
2294  if (!Sub->hasOneUse())
2295  return nullptr;
2296 
2297  if (Sub->hasNoSignedWrap()) {
2298  // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2299  if (Pred == ICmpInst::ICMP_SGT && C.isAllOnesValue())
2300  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2301 
2302  // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2303  if (Pred == ICmpInst::ICMP_SGT && C.isNullValue())
2304  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2305 
2306  // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2307  if (Pred == ICmpInst::ICMP_SLT && C.isNullValue())
2308  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2309 
2310  // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2311  if (Pred == ICmpInst::ICMP_SLT && C.isOneValue())
2312  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2313  }
2314 
2315  const APInt *C2;
2316  if (!match(X, m_APInt(C2)))
2317  return nullptr;
2318 
2319  // C2 - Y <u C -> (Y | (C - 1)) == C2
2320  // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2321  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() &&
2322  (*C2 & (C - 1)) == (C - 1))
2323  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, C - 1), X);
2324 
2325  // C2 - Y >u C -> (Y | C) != C2
2326  // iff C2 & C == C and C + 1 is a power of 2
2327  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == C)
2328  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, C), X);
2329 
2330  return nullptr;
2331 }
2332 
2333 /// Fold icmp (add X, Y), C.
2334 Instruction *InstCombiner::foldICmpAddConstant(ICmpInst &Cmp,
2336  const APInt &C) {
2337  Value *Y = Add->getOperand(1);
2338  const APInt *C2;
2339  if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2340  return nullptr;
2341 
2342  // Fold icmp pred (add X, C2), C.
2343  Value *X = Add->getOperand(0);
2344  Type *Ty = Add->getType();
2345  CmpInst::Predicate Pred = Cmp.getPredicate();
2346 
2347  // If the add does not wrap, we can always adjust the compare by subtracting
2348  // the constants. Equality comparisons are handled elsewhere. SGE/SLE are
2349  // canonicalized to SGT/SLT.
2350  if (Add->hasNoSignedWrap() &&
2351  (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) {
2352  bool Overflow;
2353  APInt NewC = C.ssub_ov(*C2, Overflow);
2354  // If there is overflow, the result must be true or false.
2355  // TODO: Can we assert there is no overflow because InstSimplify always
2356  // handles those cases?
2357  if (!Overflow)
2358  // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2359  return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2360  }
2361 
2362  auto CR = ConstantRange::makeExactICmpRegion(Pred, C).subtract(*C2);
2363  const APInt &Upper = CR.getUpper();
2364  const APInt &Lower = CR.getLower();
2365  if (Cmp.isSigned()) {
2366  if (Lower.isSignMask())
2367  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2368  if (Upper.isSignMask())
2369  return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2370  } else {
2371  if (Lower.isMinValue())
2372  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2373  if (Upper.isMinValue())
2374  return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2375  }
2376 
2377  if (!Add->hasOneUse())
2378  return nullptr;
2379 
2380  // X+C <u C2 -> (X & -C2) == C
2381  // iff C & (C2-1) == 0
2382  // C2 is a power of 2
2383  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() && (*C2 & (C - 1)) == 0)
2384  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
2385  ConstantExpr::getNeg(cast<Constant>(Y)));
2386 
2387  // X+C >u C2 -> (X & ~C2) != C
2388  // iff C & C2 == 0
2389  // C2+1 is a power of 2
2390  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == 0)
2391  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~C),
2392  ConstantExpr::getNeg(cast<Constant>(Y)));
2393 
2394  return nullptr;
2395 }
2396 
2397 bool InstCombiner::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
2398  Value *&RHS, ConstantInt *&Less,
2399  ConstantInt *&Equal,
2400  ConstantInt *&Greater) {
2401  // TODO: Generalize this to work with other comparison idioms or ensure
2402  // they get canonicalized into this form.
2403 
2404  // select i1 (a == b), i32 Equal, i32 (select i1 (a < b), i32 Less, i32
2405  // Greater), where Equal, Less and Greater are placeholders for any three
2406  // constants.
2407  ICmpInst::Predicate PredA, PredB;
2408  if (match(SI->getTrueValue(), m_ConstantInt(Equal)) &&
2409  match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) &&
2410  PredA == ICmpInst::ICMP_EQ &&
2411  match(SI->getFalseValue(),
2412  m_Select(m_ICmp(PredB, m_Specific(LHS), m_Specific(RHS)),
2413  m_ConstantInt(Less), m_ConstantInt(Greater))) &&
2414  PredB == ICmpInst::ICMP_SLT) {
2415  return true;
2416  }
2417  return false;
2418 }
2419 
2420 Instruction *InstCombiner::foldICmpSelectConstant(ICmpInst &Cmp,
2421  SelectInst *Select,
2422  ConstantInt *C) {
2423 
2424  assert(C && "Cmp RHS should be a constant int!");
2425  // If we're testing a constant value against the result of a three way
2426  // comparison, the result can be expressed directly in terms of the
2427  // original values being compared. Note: We could possibly be more
2428  // aggressive here and remove the hasOneUse test. The original select is
2429  // really likely to simplify or sink when we remove a test of the result.
2430  Value *OrigLHS, *OrigRHS;
2431  ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
2432  if (Cmp.hasOneUse() &&
2433  matchThreeWayIntCompare(Select, OrigLHS, OrigRHS, C1LessThan, C2Equal,
2434  C3GreaterThan)) {
2435  assert(C1LessThan && C2Equal && C3GreaterThan);
2436 
2437  bool TrueWhenLessThan =
2438  ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
2439  ->isAllOnesValue();
2440  bool TrueWhenEqual =
2441  ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
2442  ->isAllOnesValue();
2443  bool TrueWhenGreaterThan =
2444  ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
2445  ->isAllOnesValue();
2446 
2447  // This generates the new instruction that will replace the original Cmp
2448  // Instruction. Instead of enumerating the various combinations when
2449  // TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
2450  // false, we rely on chaining of ORs and future passes of InstCombine to
2451  // simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
2452 
2453  // When none of the three constants satisfy the predicate for the RHS (C),
2454  // the entire original Cmp can be simplified to a false.
2455  Value *Cond = Builder.getFalse();
2456  if (TrueWhenLessThan)
2457  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT, OrigLHS, OrigRHS));
2458  if (TrueWhenEqual)
2459  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ, OrigLHS, OrigRHS));
2460  if (TrueWhenGreaterThan)
2461  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT, OrigLHS, OrigRHS));
2462 
2463  return replaceInstUsesWith(Cmp, Cond);
2464  }
2465  return nullptr;
2466 }
2467 
2468 /// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2469 /// where X is some kind of instruction.
2470 Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2471  const APInt *C;
2472  if (!match(Cmp.getOperand(1), m_APInt(C)))
2473  return nullptr;
2474 
2475  if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
2476  switch (BO->getOpcode()) {
2477  case Instruction::Xor:
2478  if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
2479  return I;
2480  break;
2481  case Instruction::And:
2482  if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
2483  return I;
2484  break;
2485  case Instruction::Or:
2486  if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
2487  return I;
2488  break;
2489  case Instruction::Mul:
2490  if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
2491  return I;
2492  break;
2493  case Instruction::Shl:
2494  if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
2495  return I;
2496  break;
2497  case Instruction::LShr:
2498  case Instruction::AShr:
2499  if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
2500  return I;
2501  break;
2502  case Instruction::UDiv:
2503  if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
2504  return I;
2506  case Instruction::SDiv:
2507  if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
2508  return I;
2509  break;
2510  case Instruction::Sub:
2511  if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
2512  return I;
2513  break;
2514  case Instruction::Add:
2515  if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
2516  return I;
2517  break;
2518  default:
2519  break;
2520  }
2521  // TODO: These folds could be refactored to be part of the above calls.
2522  if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
2523  return I;
2524  }
2525 
2526  // Match against CmpInst LHS being instructions other than binary operators.
2527 
2528  if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
2529  // For now, we only support constant integers while folding the
2530  // ICMP(SELECT)) pattern. We can extend this to support vector of integers
2531  // similar to the cases handled by binary ops above.
2532  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
2533  if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
2534  return I;
2535  }
2536 
2537  if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
2538  if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
2539  return I;
2540  }
2541 
2542  if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, *C))
2543  return I;
2544 
2545  return nullptr;
2546 }
2547 
2548 /// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2549 /// icmp eq/ne BO, C.
2550 Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2551  BinaryOperator *BO,
2552  const APInt &C) {
2553  // TODO: Some of these folds could work with arbitrary constants, but this
2554  // function is limited to scalar and vector splat constants.
2555  if (!Cmp.isEquality())
2556  return nullptr;
2557 
2558  ICmpInst::Predicate Pred = Cmp.getPredicate();
2559  bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2560  Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2561  Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2562 
2563  switch (BO->getOpcode()) {
2564  case Instruction::SRem:
2565  // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2566  if (C.isNullValue() && BO->hasOneUse()) {
2567  const APInt *BOC;
2568  if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2569  Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
2570  return new ICmpInst(Pred, NewRem,
2572  }
2573  }
2574  break;
2575  case Instruction::Add: {
2576  // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2577  const APInt *BOC;
2578  if (match(BOp1, m_APInt(BOC))) {
2579  if (BO->hasOneUse()) {
2580  Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2581  return new ICmpInst(Pred, BOp0, SubC);
2582  }
2583  } else if (C.isNullValue()) {
2584  // Replace ((add A, B) != 0) with (A != -B) if A or B is
2585  // efficiently invertible, or if the add has just this one use.
2586  if (Value *NegVal = dyn_castNegVal(BOp1))
2587  return new ICmpInst(Pred, BOp0, NegVal);
2588  if (Value *NegVal = dyn_castNegVal(BOp0))
2589  return new ICmpInst(Pred, NegVal, BOp1);
2590  if (BO->hasOneUse()) {
2591  Value *Neg = Builder.CreateNeg(BOp1);
2592  Neg->takeName(BO);
2593  return new ICmpInst(Pred, BOp0, Neg);
2594  }
2595  }
2596  break;
2597  }
2598  case Instruction::Xor:
2599  if (BO->hasOneUse()) {
2600  if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2601  // For the xor case, we can xor two constants together, eliminating
2602  // the explicit xor.
2603  return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2604  } else if (C.isNullValue()) {
2605  // Replace ((xor A, B) != 0) with (A != B)
2606  return new ICmpInst(Pred, BOp0, BOp1);
2607  }
2608  }
2609  break;
2610  case Instruction::Sub:
2611  if (BO->hasOneUse()) {
2612  const APInt *BOC;
2613  if (match(BOp0, m_APInt(BOC))) {
2614  // Replace ((sub BOC, B) != C) with (B != BOC-C).
2615  Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2616  return new ICmpInst(Pred, BOp1, SubC);
2617  } else if (C.isNullValue()) {
2618  // Replace ((sub A, B) != 0) with (A != B).
2619  return new ICmpInst(Pred, BOp0, BOp1);
2620  }
2621  }
2622  break;
2623  case Instruction::Or: {
2624  const APInt *BOC;
2625  if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2626  // Comparing if all bits outside of a constant mask are set?
2627  // Replace (X | C) == -1 with (X & ~C) == ~C.
2628  // This removes the -1 constant.
2629  Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2630  Value *And = Builder.CreateAnd(BOp0, NotBOC);
2631  return new ICmpInst(Pred, And, NotBOC);
2632  }
2633  break;
2634  }
2635  case Instruction::And: {
2636  const APInt *BOC;
2637  if (match(BOp1, m_APInt(BOC))) {
2638  // If we have ((X & C) == C), turn it into ((X & C) != 0).
2639  if (C == *BOC && C.isPowerOf2())
2640  return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2641  BO, Constant::getNullValue(RHS->getType()));
2642 
2643  // Don't perform the following transforms if the AND has multiple uses
2644  if (!BO->hasOneUse())
2645  break;
2646 
2647  // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2648  if (BOC->isSignMask()) {
2649  Constant *Zero = Constant::getNullValue(BOp0->getType());
2650  auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2651  return new ICmpInst(NewPred, BOp0, Zero);
2652  }
2653 
2654  // ((X & ~7) == 0) --> X < 8
2655  if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
2656  Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2657  auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2658  return new ICmpInst(NewPred, BOp0, NegBOC);
2659  }
2660  }
2661  break;
2662  }
2663  case Instruction::Mul:
2664  if (C.isNullValue() && BO->hasNoSignedWrap()) {
2665  const APInt *BOC;
2666  if (match(BOp1, m_APInt(BOC)) && !BOC->isNullValue()) {
2667  // The trivial case (mul X, 0) is handled by InstSimplify.
2668  // General case : (mul X, C) != 0 iff X != 0
2669  // (mul X, C) == 0 iff X == 0
2670  return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2671  }
2672  }
2673  break;
2674  case Instruction::UDiv:
2675  if (C.isNullValue()) {
2676  // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2677  auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2678  return new ICmpInst(NewPred, BOp1, BOp0);
2679  }
2680  break;
2681  default:
2682  break;
2683  }
2684  return nullptr;
2685 }
2686 
2687 /// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2688 Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2689  const APInt &C) {
2691  if (!II || !Cmp.isEquality())
2692  return nullptr;
2693 
2694  // Handle icmp {eq|ne} <intrinsic>, Constant.
2695  Type *Ty = II->getType();
2696  switch (II->getIntrinsicID()) {
2697  case Intrinsic::bswap:
2698  Worklist.Add(II);
2699  Cmp.setOperand(0, II->getArgOperand(0));
2700  Cmp.setOperand(1, ConstantInt::get(Ty, C.byteSwap()));
2701  return &Cmp;
2702 
2703  case Intrinsic::ctlz:
2704  case Intrinsic::cttz:
2705  // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2706  if (C == C.getBitWidth()) {
2707  Worklist.Add(II);
2708  Cmp.setOperand(0, II->getArgOperand(0));
2710  return &Cmp;
2711  }
2712  break;
2713 
2714  case Intrinsic::ctpop: {
2715  // popcount(A) == 0 -> A == 0 and likewise for !=
2716  // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2717  bool IsZero = C.isNullValue();
2718  if (IsZero || C == C.getBitWidth()) {
2719  Worklist.Add(II);
2720  Cmp.setOperand(0, II->getArgOperand(0));
2721  auto *NewOp =
2723  Cmp.setOperand(1, NewOp);
2724  return &Cmp;
2725  }
2726  break;
2727  }
2728  default:
2729  break;
2730  }
2731 
2732  return nullptr;
2733 }
2734 
2735 /// Handle icmp with constant (but not simple integer constant) RHS.
2736 Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2737  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2738  Constant *RHSC = dyn_cast<Constant>(Op1);
2739  Instruction *LHSI = dyn_cast<Instruction>(Op0);
2740  if (!RHSC || !LHSI)
2741  return nullptr;
2742 
2743  switch (LHSI->getOpcode()) {
2744  case Instruction::GetElementPtr:
2745  // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2746  if (RHSC->isNullValue() &&
2747  cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2748  return new ICmpInst(
2749  I.getPredicate(), LHSI->getOperand(0),
2750  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2751  break;
2752  case Instruction::PHI:
2753  // Only fold icmp into the PHI if the phi and icmp are in the same
2754  // block. If in the same block, we're encouraging jump threading. If
2755  // not, we are just pessimizing the code by making an i1 phi.
2756  if (LHSI->getParent() == I.getParent())
2757  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2758  return NV;
2759  break;
2760  case Instruction::Select: {
2761  // If either operand of the select is a constant, we can fold the
2762  // comparison into the select arms, which will cause one to be
2763  // constant folded and the select turned into a bitwise or.
2764  Value *Op1 = nullptr, *Op2 = nullptr;
2765  ConstantInt *CI = nullptr;
2766  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2767  Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2768  CI = dyn_cast<ConstantInt>(Op1);
2769  }
2770  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2771  Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2772  CI = dyn_cast<ConstantInt>(Op2);
2773  }
2774 
2775  // We only want to perform this transformation if it will not lead to
2776  // additional code. This is true if either both sides of the select
2777  // fold to a constant (in which case the icmp is replaced with a select
2778  // which will usually simplify) or this is the only user of the
2779  // select (in which case we are trading a select+icmp for a simpler
2780  // select+icmp) or all uses of the select can be replaced based on
2781  // dominance information ("Global cases").
2782  bool Transform = false;
2783  if (Op1 && Op2)
2784  Transform = true;
2785  else if (Op1 || Op2) {
2786  // Local case
2787  if (LHSI->hasOneUse())
2788  Transform = true;
2789  // Global cases
2790  else if (CI && !CI->isZero())
2791  // When Op1 is constant try replacing select with second operand.
2792  // Otherwise Op2 is constant and try replacing select with first
2793  // operand.
2794  Transform =
2795  replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2796  }
2797  if (Transform) {
2798  if (!Op1)
2799  Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2800  I.getName());
2801  if (!Op2)
2802  Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2803  I.getName());
2804  return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2805  }
2806  break;
2807  }
2808  case Instruction::IntToPtr:
2809  // icmp pred inttoptr(X), null -> icmp pred X, 0
2810  if (RHSC->isNullValue() &&
2811  DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2812  return new ICmpInst(
2813  I.getPredicate(), LHSI->getOperand(0),
2814  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2815  break;
2816 
2817  case Instruction::Load:
2818  // Try to optimize things like "A[i] > 4" to index computations.
2819  if (GetElementPtrInst *GEP =
2820  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2821  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2822  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2823  !cast<LoadInst>(LHSI)->isVolatile())
2824  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2825  return Res;
2826  }
2827  break;
2828  }
2829 
2830  return nullptr;
2831 }
2832 
2833 /// Try to fold icmp (binop), X or icmp X, (binop).
2834 /// TODO: A large part of this logic is duplicated in InstSimplify's
2835 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
2836 /// duplication.
2837 Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2838  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2839 
2840  // Special logic for binary operators.
2841  BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2842  BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2843  if (!BO0 && !BO1)
2844  return nullptr;
2845 
2846  const CmpInst::Predicate Pred = I.getPredicate();
2847  bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2848  if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2849  NoOp0WrapProblem =
2850  ICmpInst::isEquality(Pred) ||
2851  (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2852  (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2853  if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2854  NoOp1WrapProblem =
2855  ICmpInst::isEquality(Pred) ||
2856  (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2857  (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2858 
2859  // Analyze the case when either Op0 or Op1 is an add instruction.
2860  // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2861  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2862  if (BO0 && BO0->getOpcode() == Instruction::Add) {
2863  A = BO0->getOperand(0);
2864  B = BO0->getOperand(1);
2865  }
2866  if (BO1 && BO1->getOpcode() == Instruction::Add) {
2867  C = BO1->getOperand(0);
2868  D = BO1->getOperand(1);
2869  }
2870 
2871  // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2872  if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2873  return new ICmpInst(Pred, A == Op1 ? B : A,
2874  Constant::getNullValue(Op1->getType()));
2875 
2876  // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2877  if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2878  return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2879  C == Op0 ? D : C);
2880 
2881  // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2882  if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2883  NoOp1WrapProblem &&
2884  // Try not to increase register pressure.
2885  BO0->hasOneUse() && BO1->hasOneUse()) {
2886  // Determine Y and Z in the form icmp (X+Y), (X+Z).
2887  Value *Y, *Z;
2888  if (A == C) {
2889  // C + B == C + D -> B == D
2890  Y = B;
2891  Z = D;
2892  } else if (A == D) {
2893  // D + B == C + D -> B == C
2894  Y = B;
2895  Z = C;
2896  } else if (B == C) {
2897  // A + C == C + D -> A == D
2898  Y = A;
2899  Z = D;
2900  } else {
2901  assert(B == D);
2902  // A + D == C + D -> A == C
2903  Y = A;
2904  Z = C;
2905  }
2906  return new ICmpInst(Pred, Y, Z);
2907  }
2908 
2909  // icmp slt (X + -1), Y -> icmp sle X, Y
2910  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2911  match(B, m_AllOnes()))
2912  return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2913 
2914  // icmp sge (X + -1), Y -> icmp sgt X, Y
2915  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2916  match(B, m_AllOnes()))
2917  return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2918 
2919  // icmp sle (X + 1), Y -> icmp slt X, Y
2920  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2921  return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2922 
2923  // icmp sgt (X + 1), Y -> icmp sge X, Y
2924  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2925  return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2926 
2927  // icmp sgt X, (Y + -1) -> icmp sge X, Y
2928  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2929  match(D, m_AllOnes()))
2930  return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2931 
2932  // icmp sle X, (Y + -1) -> icmp slt X, Y
2933  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2934  match(D, m_AllOnes()))
2935  return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2936 
2937  // icmp sge X, (Y + 1) -> icmp sgt X, Y
2938  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
2939  return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
2940 
2941  // icmp slt X, (Y + 1) -> icmp sle X, Y
2942  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
2943  return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
2944 
2945  // TODO: The subtraction-related identities shown below also hold, but
2946  // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
2947  // wouldn't happen even if they were implemented.
2948  //
2949  // icmp ult (X - 1), Y -> icmp ule X, Y
2950  // icmp uge (X - 1), Y -> icmp ugt X, Y
2951  // icmp ugt X, (Y - 1) -> icmp uge X, Y
2952  // icmp ule X, (Y - 1) -> icmp ult X, Y
2953 
2954  // icmp ule (X + 1), Y -> icmp ult X, Y
2955  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
2956  return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
2957 
2958  // icmp ugt (X + 1), Y -> icmp uge X, Y
2959  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
2960  return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
2961 
2962  // icmp uge X, (Y + 1) -> icmp ugt X, Y
2963  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
2964  return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
2965 
2966  // icmp ult X, (Y + 1) -> icmp ule X, Y
2967  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
2968  return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
2969 
2970  // if C1 has greater magnitude than C2:
2971  // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
2972  // s.t. C3 = C1 - C2
2973  //
2974  // if C2 has greater magnitude than C1:
2975  // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
2976  // s.t. C3 = C2 - C1
2977  if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
2978  (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
2979  if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
2980  if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
2981  const APInt &AP1 = C1->getValue();
2982  const APInt &AP2 = C2->getValue();
2983  if (AP1.isNegative() == AP2.isNegative()) {
2984  APInt AP1Abs = C1->getValue().abs();
2985  APInt AP2Abs = C2->getValue().abs();
2986  if (AP1Abs.uge(AP2Abs)) {
2987  ConstantInt *C3 = Builder.getInt(AP1 - AP2);
2988  Value *NewAdd = Builder.CreateNSWAdd(A, C3);
2989  return new ICmpInst(Pred, NewAdd, C);
2990  } else {
2991  ConstantInt *C3 = Builder.getInt(AP2 - AP1);
2992  Value *NewAdd = Builder.CreateNSWAdd(C, C3);
2993  return new ICmpInst(Pred, A, NewAdd);
2994  }
2995  }
2996  }
2997 
2998  // Analyze the case when either Op0 or Op1 is a sub instruction.
2999  // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
3000  A = nullptr;
3001  B = nullptr;
3002  C = nullptr;
3003  D = nullptr;
3004  if (BO0 && BO0->getOpcode() == Instruction::Sub) {
3005  A = BO0->getOperand(0);
3006  B = BO0->getOperand(1);
3007  }
3008  if (BO1 && BO1->getOpcode() == Instruction::Sub) {
3009  C = BO1->getOperand(0);
3010  D = BO1->getOperand(1);
3011  }
3012 
3013  // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
3014  if (A == Op1 && NoOp0WrapProblem)
3015  return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
3016 
3017  // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
3018  if (C == Op0 && NoOp1WrapProblem)
3019  return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
3020 
3021  // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
3022  if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
3023  // Try not to increase register pressure.
3024  BO0->hasOneUse() && BO1->hasOneUse())
3025  return new ICmpInst(Pred, A, C);
3026 
3027  // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
3028  if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
3029  // Try not to increase register pressure.
3030  BO0->hasOneUse() && BO1->hasOneUse())
3031  return new ICmpInst(Pred, D, B);
3032 
3033  // icmp (0-X) < cst --> x > -cst
3034  if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
3035  Value *X;
3036  if (match(BO0, m_Neg(m_Value(X))))
3037  if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3038  if (!RHSC->isMinValue(/*isSigned=*/true))
3039  return new ICmpInst(I.getSwappedPredicate(), X,
3040  ConstantExpr::getNeg(RHSC));
3041  }
3042 
3043  BinaryOperator *SRem = nullptr;
3044  // icmp (srem X, Y), Y
3045  if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
3046  SRem = BO0;
3047  // icmp Y, (srem X, Y)
3048  else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3049  Op0 == BO1->getOperand(1))
3050  SRem = BO1;
3051  if (SRem) {
3052  // We don't check hasOneUse to avoid increasing register pressure because
3053  // the value we use is the same value this instruction was already using.
3054  switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3055  default:
3056  break;
3057  case ICmpInst::ICMP_EQ:
3058  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3059  case ICmpInst::ICMP_NE:
3060  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3061  case ICmpInst::ICMP_SGT:
3062  case ICmpInst::ICMP_SGE:
3063  return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3065  case ICmpInst::ICMP_SLT:
3066  case ICmpInst::ICMP_SLE:
3067  return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3068  Constant::getNullValue(SRem->getType()));
3069  }
3070  }
3071 
3072  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3073  BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3074  switch (BO0->getOpcode()) {
3075  default:
3076  break;
3077  case Instruction::Add:
3078  case Instruction::Sub:
3079  case Instruction::Xor: {
3080  if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3081  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3082 
3083  const APInt *C;
3084  if (match(BO0->getOperand(1), m_APInt(C))) {
3085  // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3086  if (C->isSignMask()) {
3087  ICmpInst::Predicate NewPred =
3089  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3090  }
3091 
3092  // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
3093  if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
3094  ICmpInst::Predicate NewPred =
3096  NewPred = I.getSwappedPredicate(NewPred);
3097  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3098  }
3099  }
3100  break;
3101  }
3102  case Instruction::Mul: {
3103  if (!I.isEquality())
3104  break;
3105 
3106  const APInt *C;
3107  if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
3108  !C->isOneValue()) {
3109  // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
3110  // Mask = -1 >> count-trailing-zeros(C).
3111  if (unsigned TZs = C->countTrailingZeros()) {
3113  BO0->getType(),
3114  APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
3115  Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
3116  Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
3117  return new ICmpInst(Pred, And1, And2);
3118  }
3119  // If there are no trailing zeros in the multiplier, just eliminate
3120  // the multiplies (no masking is needed):
3121  // icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
3122  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3123  }
3124  break;
3125  }
3126  case Instruction::UDiv:
3127  case Instruction::LShr:
3128  if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
3129  break;
3130  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3131 
3132  case Instruction::SDiv:
3133  if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
3134  break;
3135  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3136 
3137  case Instruction::AShr:
3138  if (!BO0->isExact() || !BO1->isExact())
3139  break;
3140  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3141 
3142  case Instruction::Shl: {
3143  bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3144  bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3145  if (!NUW && !NSW)
3146  break;
3147  if (!NSW && I.isSigned())
3148  break;
3149  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3150  }
3151  }
3152  }
3153 
3154  if (BO0) {
3155  // Transform A & (L - 1) `ult` L --> L != 0
3156  auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3157  auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
3158 
3159  if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
3160  auto *Zero = Constant::getNullValue(BO0->getType());
3161  return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3162  }
3163  }
3164 
3165  return nullptr;
3166 }
3167 
3168 /// Fold icmp Pred min|max(X, Y), X.
3170  ICmpInst::Predicate Pred = Cmp.getPredicate();
3171  Value *Op0 = Cmp.getOperand(0);
3172  Value *X = Cmp.getOperand(1);
3173 
3174  // Canonicalize minimum or maximum operand to LHS of the icmp.
3175  if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3176  match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3177  match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3178  match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3179  std::swap(Op0, X);
3180  Pred = Cmp.getSwappedPredicate();
3181  }
3182 
3183  Value *Y;
3184  if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3185  // smin(X, Y) == X --> X s<= Y
3186  // smin(X, Y) s>= X --> X s<= Y
3187  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3188  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3189 
3190  // smin(X, Y) != X --> X s> Y
3191  // smin(X, Y) s< X --> X s> Y
3192  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3193  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3194 
3195  // These cases should be handled in InstSimplify:
3196  // smin(X, Y) s<= X --> true
3197  // smin(X, Y) s> X --> false
3198  return nullptr;
3199  }
3200 
3201  if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3202  // smax(X, Y) == X --> X s>= Y
3203  // smax(X, Y) s<= X --> X s>= Y
3204  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3205  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3206 
3207  // smax(X, Y) != X --> X s< Y
3208  // smax(X, Y) s> X --> X s< Y
3209  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3210  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3211 
3212  // These cases should be handled in InstSimplify:
3213  // smax(X, Y) s>= X --> true
3214  // smax(X, Y) s< X --> false
3215  return nullptr;
3216  }
3217 
3218  if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3219  // umin(X, Y) == X --> X u<= Y
3220  // umin(X, Y) u>= X --> X u<= Y
3221  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3222  return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3223 
3224  // umin(X, Y) != X --> X u> Y
3225  // umin(X, Y) u< X --> X u> Y
3226  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3227  return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3228 
3229  // These cases should be handled in InstSimplify:
3230  // umin(X, Y) u<= X --> true
3231  // umin(X, Y) u> X --> false
3232  return nullptr;
3233  }
3234 
3235  if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3236  // umax(X, Y) == X --> X u>= Y
3237  // umax(X, Y) u<= X --> X u>= Y
3238  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3239  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3240 
3241  // umax(X, Y) != X --> X u< Y
3242  // umax(X, Y) u> X --> X u< Y
3243  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3244  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3245 
3246  // These cases should be handled in InstSimplify:
3247  // umax(X, Y) u>= X --> true
3248  // umax(X, Y) u< X --> false
3249  return nullptr;
3250  }
3251 
3252  return nullptr;
3253 }
3254 
3255 Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3256  if (!I.isEquality())
3257  return nullptr;
3258 
3259  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3260  const CmpInst::Predicate Pred = I.getPredicate();
3261  Value *A, *B, *C, *D;
3262  if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3263  if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3264  Value *OtherVal = A == Op1 ? B : A;
3265  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3266  }
3267 
3268  if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3269  // A^c1 == C^c2 --> A == C^(c1^c2)
3270  ConstantInt *C1, *C2;
3271  if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3272  Op1->hasOneUse()) {
3273  Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
3274  Value *Xor = Builder.CreateXor(C, NC);
3275  return new ICmpInst(Pred, A, Xor);
3276  }
3277 
3278  // A^B == A^D -> B == D
3279  if (A == C)
3280  return new ICmpInst(Pred, B, D);
3281  if (A == D)
3282  return new ICmpInst(Pred, B, C);
3283  if (B == C)
3284  return new ICmpInst(Pred, A, D);
3285  if (B == D)
3286  return new ICmpInst(Pred, A, C);
3287  }
3288  }
3289 
3290  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3291  // A == (A^B) -> B == 0
3292  Value *OtherVal = A == Op0 ? B : A;
3293  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3294  }
3295 
3296  // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3297  if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3298  match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3299  Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3300 
3301  if (A == C) {
3302  X = B;
3303  Y = D;
3304  Z = A;
3305  } else if (A == D) {
3306  X = B;
3307  Y = C;
3308  Z = A;
3309  } else if (B == C) {
3310  X = A;
3311  Y = D;
3312  Z = B;
3313  } else if (B == D) {
3314  X = A;
3315  Y = C;
3316  Z = B;
3317  }
3318 
3319  if (X) { // Build (X^Y) & Z
3320  Op1 = Builder.CreateXor(X, Y);
3321  Op1 = Builder.CreateAnd(Op1, Z);
3322  I.setOperand(0, Op1);
3323  I.setOperand(1, Constant::getNullValue(Op1->getType()));
3324  return &I;
3325  }
3326  }
3327 
3328  // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3329  // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3330  ConstantInt *Cst1;
3331  if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3332  match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3333  (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3334  match(Op1, m_ZExt(m_Value(A))))) {
3335  APInt Pow2 = Cst1->getValue() + 1;
3336  if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3337  Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3338  return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
3339  }
3340 
3341  // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3342  // For lshr and ashr pairs.
3343  if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3344  match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3345  (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3346  match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3347  unsigned TypeBits = Cst1->getBitWidth();
3348  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3349  if (ShAmt < TypeBits && ShAmt != 0) {
3350  ICmpInst::Predicate NewPred =
3352  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3353  APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3354  return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
3355  }
3356  }
3357 
3358  // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3359  if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3360  match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3361  unsigned TypeBits = Cst1->getBitWidth();
3362  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3363  if (ShAmt < TypeBits && ShAmt != 0) {
3364  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3365  APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3366  Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
3367  I.getName() + ".mask");
3368  return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
3369  }
3370  }
3371 
3372  // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3373  // "icmp (and X, mask), cst"
3374  uint64_t ShAmt = 0;
3375  if (Op0->hasOneUse() &&
3376  match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3377  match(Op1, m_ConstantInt(Cst1)) &&
3378  // Only do this when A has multiple uses. This is most important to do
3379  // when it exposes other optimizations.
3380  !A->hasOneUse()) {
3381  unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3382 
3383  if (ShAmt < ASize) {
3384  APInt MaskV =
3386  MaskV <<= ShAmt;
3387 
3388  APInt CmpV = Cst1->getValue().zext(ASize);
3389  CmpV <<= ShAmt;
3390 
3391  Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
3392  return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
3393  }
3394  }
3395 
3396  // If both operands are byte-swapped or bit-reversed, just compare the
3397  // original values.
3398  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
3399  // and handle more intrinsics.
3400  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
3401  (match(Op0, m_BitReverse(m_Value(A))) &&
3402  match(Op1, m_BitReverse(m_Value(B)))))
3403  return new ICmpInst(Pred, A, B);
3404 
3405  return nullptr;
3406 }
3407 
3408 /// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3409 /// far.
3410 Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3411  const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3412  Value *LHSCIOp = LHSCI->getOperand(0);
3413  Type *SrcTy = LHSCIOp->getType();
3414  Type *DestTy = LHSCI->getType();
3415  Value *RHSCIOp;
3416 
3417  // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3418  // integer type is the same size as the pointer type.
3419  if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3420  DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
3421  Value *RHSOp = nullptr;
3422  if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3423  Value *RHSCIOp = RHSC->getOperand(0);
3424  if (RHSCIOp->getType()->getPointerAddressSpace() ==
3425  LHSCIOp->getType()->getPointerAddressSpace()) {
3426  RHSOp = RHSC->getOperand(0);
3427  // If the pointer types don't match, insert a bitcast.
3428  if (LHSCIOp->getType() != RHSOp->getType())
3429  RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
3430  }
3431  } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3432  RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3433  }
3434 
3435  if (RHSOp)
3436  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3437  }
3438 
3439  // The code below only handles extension cast instructions, so far.
3440  // Enforce this.
3441  if (LHSCI->getOpcode() != Instruction::ZExt &&
3442  LHSCI->getOpcode() != Instruction::SExt)
3443  return nullptr;
3444 
3445  bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3446  bool isSignedCmp = ICmp.isSigned();
3447 
3448  if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3449  // Not an extension from the same type?
3450  RHSCIOp = CI->getOperand(0);
3451  if (RHSCIOp->getType() != LHSCIOp->getType())
3452  return nullptr;
3453 
3454  // If the signedness of the two casts doesn't agree (i.e. one is a sext
3455  // and the other is a zext), then we can't handle this.
3456  if (CI->getOpcode() != LHSCI->getOpcode())
3457  return nullptr;
3458 
3459  // Deal with equality cases early.
3460  if (ICmp.isEquality())
3461  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3462 
3463  // A signed comparison of sign extended values simplifies into a
3464  // signed comparison.
3465  if (isSignedCmp && isSignedExt)
3466  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3467 
3468  // The other three cases all fold into an unsigned comparison.
3469  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3470  }
3471 
3472  // If we aren't dealing with a constant on the RHS, exit early.
3473  auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3474  if (!C)
3475  return nullptr;
3476 
3477  // Compute the constant that would happen if we truncated to SrcTy then
3478  // re-extended to DestTy.
3479  Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3480  Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3481 
3482  // If the re-extended constant didn't change...
3483  if (Res2 == C) {
3484  // Deal with equality cases early.
3485  if (ICmp.isEquality())
3486  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3487 
3488  // A signed comparison of sign extended values simplifies into a
3489  // signed comparison.
3490  if (isSignedExt && isSignedCmp)
3491  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3492 
3493  // The other three cases all fold into an unsigned comparison.
3494  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3495  }
3496 
3497  // The re-extended constant changed, partly changed (in the case of a vector),
3498  // or could not be determined to be equal (in the case of a constant
3499  // expression), so the constant cannot be represented in the shorter type.
3500  // Consequently, we cannot emit a simple comparison.
3501  // All the cases that fold to true or false will have already been handled
3502  // by SimplifyICmpInst, so only deal with the tricky case.
3503 
3504  if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3505  return nullptr;
3506 
3507  // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3508  // should have been folded away previously and not enter in here.
3509 
3510  // We're performing an unsigned comp with a sign extended value.
3511  // This is true if the input is >= 0. [aka >s -1]
3512  Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3513  Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3514 
3515  // Finally, return the value computed.
3516  if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3517  return replaceInstUsesWith(ICmp, Result);
3518 
3519  assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
3520  return BinaryOperator::CreateNot(Result);
3521 }
3522 
3523 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3524  Value *RHS, Instruction &OrigI,
3525  Value *&Result, Constant *&Overflow) {
3526  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3527  std::swap(LHS, RHS);
3528 
3529  auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3530  Result = OpResult;
3531  Overflow = OverflowVal;
3532  if (ReuseName)
3533  Result->takeName(&OrigI);
3534  return true;
3535  };
3536 
3537  // If the overflow check was an add followed by a compare, the insertion point
3538  // may be pointing to the compare. We want to insert the new instructions
3539  // before the add in case there are uses of the add between the add and the
3540  // compare.
3541  Builder.SetInsertPoint(&OrigI);
3542 
3543  switch (OCF) {
3544  case OCF_INVALID:
3545  llvm_unreachable("bad overflow check kind!");
3546 
3547  case OCF_UNSIGNED_ADD: {
3548  OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3550  return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
3551  true);
3552 
3554  return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
3555 
3556  // Fall through uadd into sadd
3558  }
3559  case OCF_SIGNED_ADD: {
3560  // X + 0 -> {X, false}
3561  if (match(RHS, m_Zero()))
3562  return SetResult(LHS, Builder.getFalse(), false);
3563 
3564  // We can strength reduce this signed add into a regular add if we can prove
3565  // that it will never overflow.
3566  if (OCF == OCF_SIGNED_ADD)
3567  if (willNotOverflowSignedAdd(LHS, RHS, OrigI))
3568  return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
3569  true);
3570  break;
3571  }
3572 
3573  case OCF_UNSIGNED_SUB:
3574  case OCF_SIGNED_SUB: {
3575  // X - 0 -> {X, false}
3576  if (match(RHS, m_Zero()))
3577  return SetResult(LHS, Builder.getFalse(), false);
3578 
3579  if (OCF == OCF_SIGNED_SUB) {
3580  if (willNotOverflowSignedSub(LHS, RHS, OrigI))
3581  return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
3582  true);
3583  } else {
3584  if (willNotOverflowUnsignedSub(LHS, RHS, OrigI))
3585  return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
3586  true);
3587  }
3588  break;
3589  }
3590 
3591  case OCF_UNSIGNED_MUL: {
3592  OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3594  return SetResult(Builder.CreateNUWMul(LHS, RHS), Builder.getFalse(),
3595  true);
3597  return SetResult(Builder.CreateMul(LHS, RHS), Builder.getTrue(), true);
3599  }
3600  case OCF_SIGNED_MUL:
3601  // X * undef -> undef
3602  if (isa<UndefValue>(RHS))
3603  return SetResult(RHS, UndefValue::get(Builder.getInt1Ty()), false);
3604 
3605  // X * 0 -> {0, false}
3606  if (match(RHS, m_Zero()))
3607  return SetResult(RHS, Builder.getFalse(), false);
3608 
3609  // X * 1 -> {X, false}
3610  if (match(RHS, m_One()))
3611  return SetResult(LHS, Builder.getFalse(), false);
3612 
3613  if (OCF == OCF_SIGNED_MUL)
3614  if (willNotOverflowSignedMul(LHS, RHS, OrigI))
3615  return SetResult(Builder.CreateNSWMul(LHS, RHS), Builder.getFalse(),
3616  true);
3617  break;
3618  }
3619 
3620  return false;
3621 }
3622 
3623 /// \brief Recognize and process idiom involving test for multiplication
3624 /// overflow.
3625 ///
3626 /// The caller has matched a pattern of the form:
3627 /// I = cmp u (mul(zext A, zext B), V
3628 /// The function checks if this is a test for overflow and if so replaces
3629 /// multiplication with call to 'mul.with.overflow' intrinsic.
3630 ///
3631 /// \param I Compare instruction.
3632 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3633 /// the compare instruction. Must be of integer type.
3634 /// \param OtherVal The other argument of compare instruction.
3635 /// \returns Instruction which must replace the compare instruction, NULL if no
3636 /// replacement required.
3638  Value *OtherVal, InstCombiner &IC) {
3639  // Don't bother doing this transformation for pointers, don't do it for
3640  // vectors.
3641  if (!isa<IntegerType>(MulVal->getType()))
3642  return nullptr;
3643 
3644  assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
3645  assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
3646  auto *MulInstr = dyn_cast<Instruction>(MulVal);
3647  if (!MulInstr)
3648  return nullptr;
3649  assert(MulInstr->getOpcode() == Instruction::Mul);
3650 
3651  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3652  *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3653  assert(LHS->getOpcode() == Instruction::ZExt);
3654  assert(RHS->getOpcode() == Instruction::ZExt);
3655  Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3656 
3657  // Calculate type and width of the result produced by mul.with.overflow.
3658  Type *TyA = A->getType(), *TyB = B->getType();
3659  unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3660  WidthB = TyB->getPrimitiveSizeInBits();
3661  unsigned MulWidth;
3662  Type *MulType;
3663  if (WidthB > WidthA) {
3664  MulWidth = WidthB;
3665  MulType = TyB;
3666  } else {
3667  MulWidth = WidthA;
3668  MulType = TyA;
3669  }
3670 
3671  // In order to replace the original mul with a narrower mul.with.overflow,
3672  // all uses must ignore upper bits of the product. The number of used low
3673  // bits must be not greater than the width of mul.with.overflow.
3674  if (MulVal->hasNUsesOrMore(2))
3675  for (User *U : MulVal->users()) {
3676  if (U == &I)
3677  continue;
3678  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3679  // Check if truncation ignores bits above MulWidth.
3680  unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3681  if (TruncWidth > MulWidth)
3682  return nullptr;
3683  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3684  // Check if AND ignores bits above MulWidth.
3685  if (BO->getOpcode() != Instruction::And)
3686  return nullptr;
3687  if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3688  const APInt &CVal = CI->getValue();
3689  if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3690  return nullptr;
3691  } else {
3692  // In this case we could have the operand of the binary operation
3693  // being defined in another block, and performing the replacement
3694  // could break the dominance relation.
3695  return nullptr;
3696  }
3697  } else {
3698  // Other uses prohibit this transformation.
3699  return nullptr;
3700  }
3701  }
3702 
3703  // Recognize patterns
3704  switch (I.getPredicate()) {
3705  case ICmpInst::ICMP_EQ:
3706  case ICmpInst::ICMP_NE:
3707  // Recognize pattern:
3708  // mulval = mul(zext A, zext B)
3709  // cmp eq/neq mulval, zext trunc mulval
3710  if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3711  if (Zext->hasOneUse()) {
3712  Value *ZextArg = Zext->getOperand(0);
3713  if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3714  if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3715  break; //Recognized
3716  }
3717 
3718  // Recognize pattern:
3719  // mulval = mul(zext A, zext B)
3720  // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3721  ConstantInt *CI;
3722  Value *ValToMask;
3723  if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3724  if (ValToMask != MulVal)
3725  return nullptr;
3726  const APInt &CVal = CI->getValue() + 1;
3727  if (CVal.isPowerOf2()) {
3728  unsigned MaskWidth = CVal.logBase2();
3729  if (MaskWidth == MulWidth)
3730  break; // Recognized
3731  }
3732  }
3733  return nullptr;
3734 
3735  case ICmpInst::ICMP_UGT:
3736  // Recognize pattern:
3737  // mulval = mul(zext A, zext B)
3738  // cmp ugt mulval, max
3739  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3740  APInt MaxVal = APInt::getMaxValue(MulWidth);
3741  MaxVal = MaxVal.zext(CI->getBitWidth());
3742  if (MaxVal.eq(CI->getValue()))
3743  break; // Recognized
3744  }
3745  return nullptr;
3746 
3747  case ICmpInst::ICMP_UGE:
3748  // Recognize pattern:
3749  // mulval = mul(zext A, zext B)
3750  // cmp uge mulval, max+1
3751  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3752  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3753  if (MaxVal.eq(CI->getValue()))
3754  break; // Recognized
3755  }
3756  return nullptr;
3757 
3758  case ICmpInst::ICMP_ULE:
3759  // Recognize pattern:
3760  // mulval = mul(zext A, zext B)
3761  // cmp ule mulval, max
3762  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3763  APInt MaxVal = APInt::getMaxValue(MulWidth);
3764  MaxVal = MaxVal.zext(CI->getBitWidth());
3765  if (MaxVal.eq(CI->getValue()))
3766  break; // Recognized
3767  }
3768  return nullptr;
3769 
3770  case ICmpInst::ICMP_ULT:
3771  // Recognize pattern:
3772  // mulval = mul(zext A, zext B)
3773  // cmp ule mulval, max + 1
3774  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3775  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3776  if (MaxVal.eq(CI->getValue()))
3777  break; // Recognized
3778  }
3779  return nullptr;
3780 
3781  default:
3782  return nullptr;
3783  }
3784 
3785  InstCombiner::BuilderTy &Builder = IC.Builder;
3786  Builder.SetInsertPoint(MulInstr);
3787 
3788  // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3789  Value *MulA = A, *MulB = B;
3790  if (WidthA < MulWidth)
3791  MulA = Builder.CreateZExt(A, MulType);
3792  if (WidthB < MulWidth)
3793  MulB = Builder.CreateZExt(B, MulType);
3795  Intrinsic::umul_with_overflow, MulType);
3796  CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
3797  IC.Worklist.Add(MulInstr);
3798 
3799  // If there are uses of mul result other than the comparison, we know that
3800  // they are truncation or binary AND. Change them to use result of
3801  // mul.with.overflow and adjust properly mask/size.
3802  if (MulVal->hasNUsesOrMore(2)) {
3803  Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
3804  for (User *U : MulVal->users()) {
3805  if (U == &I || U == OtherVal)
3806  continue;
3807  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3808  if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3809  IC.replaceInstUsesWith(*TI, Mul);
3810  else
3811  TI->setOperand(0, Mul);
3812  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3813  assert(BO->getOpcode() == Instruction::And);
3814  // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3815  ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3816  APInt ShortMask = CI->getValue().trunc(MulWidth);
3817  Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
3818  Instruction *Zext =
3819  cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
3820  IC.Worklist.Add(Zext);
3821  IC.replaceInstUsesWith(*BO, Zext);
3822  } else {
3823  llvm_unreachable("Unexpected Binary operation");
3824  }
3825  IC.Worklist.Add(cast<Instruction>(U));
3826  }
3827  }
3828  if (isa<Instruction>(OtherVal))
3829  IC.Worklist.Add(cast<Instruction>(OtherVal));
3830 
3831  // The original icmp gets replaced with the overflow value, maybe inverted
3832  // depending on predicate.
3833  bool Inverse = false;
3834  switch (I.getPredicate()) {
3835  case ICmpInst::ICMP_NE:
3836  break;
3837  case ICmpInst::ICMP_EQ:
3838  Inverse = true;
3839  break;
3840  case ICmpInst::ICMP_UGT:
3841  case ICmpInst::ICMP_UGE:
3842  if (I.getOperand(0) == MulVal)
3843  break;
3844  Inverse = true;
3845  break;
3846  case ICmpInst::ICMP_ULT:
3847  case ICmpInst::ICMP_ULE:
3848  if (I.getOperand(1) == MulVal)
3849  break;
3850  Inverse = true;
3851  break;
3852  default:
3853  llvm_unreachable("Unexpected predicate");
3854  }
3855  if (Inverse) {
3856  Value *Res = Builder.CreateExtractValue(Call, 1);
3857  return BinaryOperator::CreateNot(Res);
3858  }
3859 
3860  return ExtractValueInst::Create(Call, 1);
3861 }
3862 
3863 /// When performing a comparison against a constant, it is possible that not all
3864 /// the bits in the LHS are demanded. This helper method computes the mask that
3865 /// IS demanded.
3866 static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
3867  const APInt *RHS;
3868  if (!match(I.getOperand(1), m_APInt(RHS)))
3869  return APInt::getAllOnesValue(BitWidth);
3870 
3871  // If this is a normal comparison, it demands all bits. If it is a sign bit
3872  // comparison, it only demands the sign bit.
3873  bool UnusedBit;
3874  if (isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
3875  return APInt::getSignMask(BitWidth);
3876 
3877  switch (I.getPredicate()) {
3878  // For a UGT comparison, we don't care about any bits that
3879  // correspond to the trailing ones of the comparand. The value of these
3880  // bits doesn't impact the outcome of the comparison, because any value
3881  // greater than the RHS must differ in a bit higher than these due to carry.
3882  case ICmpInst::ICMP_UGT:
3883  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
3884 
3885  // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3886  // Any value less than the RHS must differ in a higher bit because of carries.
3887  case ICmpInst::ICMP_ULT:
3888  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
3889 
3890  default:
3891  return APInt::getAllOnesValue(BitWidth);
3892  }
3893 }
3894 
3895 /// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
3896 /// should be swapped.
3897 /// The decision is based on how many times these two operands are reused
3898 /// as subtract operands and their positions in those instructions.
3899 /// The rational is that several architectures use the same instruction for
3900 /// both subtract and cmp, thus it is better if the order of those operands
3901 /// match.
3902 /// \return true if Op0 and Op1 should be swapped.
3903 static bool swapMayExposeCSEOpportunities(const Value * Op0,
3904  const Value * Op1) {
3905  // Filter out pointer value as those cannot appears directly in subtract.
3906  // FIXME: we may want to go through inttoptrs or bitcasts.
3907  if (Op0->getType()->isPointerTy())
3908  return false;
3909  // Count every uses of both Op0 and Op1 in a subtract.
3910  // Each time Op0 is the first operand, count -1: swapping is bad, the
3911  // subtract has already the same layout as the compare.
3912  // Each time Op0 is the second operand, count +1: swapping is good, the
3913  // subtract has a different layout as the compare.
3914  // At the end, if the benefit is greater than 0, Op0 should come second to
3915  // expose more CSE opportunities.
3916  int GlobalSwapBenefits = 0;
3917  for (const User *U : Op0->users()) {
3918  const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U);
3919  if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
3920  continue;
3921  // If Op0 is the first argument, this is not beneficial to swap the
3922  // arguments.
3923  int LocalSwapBenefits = -1;
3924  unsigned Op1Idx = 1;
3925  if (BinOp->getOperand(Op1Idx) == Op0) {
3926  Op1Idx = 0;
3927  LocalSwapBenefits = 1;
3928  }
3929  if (BinOp->getOperand(Op1Idx) != Op1)
3930  continue;
3931  GlobalSwapBenefits += LocalSwapBenefits;
3932  }
3933  return GlobalSwapBenefits > 0;
3934 }
3935 
3936 /// \brief Check that one use is in the same block as the definition and all
3937 /// other uses are in blocks dominated by a given block.
3938 ///
3939 /// \param DI Definition
3940 /// \param UI Use
3941 /// \param DB Block that must dominate all uses of \p DI outside
3942 /// the parent block
3943 /// \return true when \p UI is the only use of \p DI in the parent block
3944 /// and all other uses of \p DI are in blocks dominated by \p DB.
3945 ///
3947  const Instruction *UI,
3948  const BasicBlock *DB) const {
3949  assert(DI && UI && "Instruction not defined\n");
3950  // Ignore incomplete definitions.
3951  if (!DI->getParent())
3952  return false;
3953  // DI and UI must be in the same block.
3954  if (DI->getParent() != UI->getParent())
3955  return false;
3956  // Protect from self-referencing blocks.
3957  if (DI->getParent() == DB)
3958  return false;
3959  for (const User *U : DI->users()) {
3960  auto *Usr = cast<Instruction>(U);
3961  if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
3962  return false;
3963  }
3964  return true;
3965 }
3966 
3967 /// Return true when the instruction sequence within a block is select-cmp-br.
3968 static bool isChainSelectCmpBranch(const SelectInst *SI) {
3969  const BasicBlock *BB = SI->getParent();
3970  if (!BB)
3971  return false;
3972  auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
3973  if (!BI || BI->getNumSuccessors() != 2)
3974  return false;
3975  auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
3976  if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
3977  return false;
3978  return true;
3979 }
3980 
3981 /// \brief True when a select result is replaced by one of its operands
3982 /// in select-icmp sequence. This will eventually result in the elimination
3983 /// of the select.
3984 ///
3985 /// \param SI Select instruction
3986 /// \param Icmp Compare instruction
3987 /// \param SIOpd Operand that replaces the select
3988 ///
3989 /// Notes:
3990 /// - The replacement is global and requires dominator information
3991 /// - The caller is responsible for the actual replacement
3992 ///
3993 /// Example:
3994 ///
3995 /// entry:
3996 /// %4 = select i1 %3, %C* %0, %C* null
3997 /// %5 = icmp eq %C* %4, null
3998 /// br i1 %5, label %9, label %7
3999 /// ...
4000 /// ; <label>:7 ; preds = %entry
4001 /// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
4002 /// ...
4003 ///
4004 /// can be transformed to
4005 ///
4006 /// %5 = icmp eq %C* %0, null
4007 /// %6 = select i1 %3, i1 %5, i1 true
4008 /// br i1 %6, label %9, label %7
4009 /// ...
4010 /// ; <label>:7 ; preds = %entry
4011 /// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
4012 ///
4013 /// Similar when the first operand of the select is a constant or/and
4014 /// the compare is for not equal rather than equal.
4015 ///
4016 /// NOTE: The function is only called when the select and compare constants
4017 /// are equal, the optimization can work only for EQ predicates. This is not a
4018 /// major restriction since a NE compare should be 'normalized' to an equal
4019 /// compare, which usually happens in the combiner and test case
4020 /// select-cmp-br.ll checks for it.
4022  const ICmpInst *Icmp,
4023  const unsigned SIOpd) {
4024  assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
4025  if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
4026  BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
4027  // The check for the single predecessor is not the best that can be
4028  // done. But it protects efficiently against cases like when SI's
4029  // home block has two successors, Succ and Succ1, and Succ1 predecessor
4030  // of Succ. Then SI can't be replaced by SIOpd because the use that gets
4031  // replaced can be reached on either path. So the uniqueness check
4032  // guarantees that the path all uses of SI (outside SI's parent) are on
4033  // is disjoint from all other paths out of SI. But that information
4034  // is more expensive to compute, and the trade-off here is in favor
4035  // of compile-time. It should also be noticed that we check for a single
4036  // predecessor and not only uniqueness. This to handle the situation when
4037  // Succ and Succ1 points to the same basic block.
4038  if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
4039  NumSel++;
4040  SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
4041  return true;
4042  }
4043  }
4044  return false;
4045 }
4046 
4047 /// Try to fold the comparison based on range information we can get by checking
4048 /// whether bits are known to be zero or one in the inputs.
4049 Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
4050  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4051  Type *Ty = Op0->getType();
4052  ICmpInst::Predicate Pred = I.getPredicate();
4053 
4054  // Get scalar or pointer size.
4055  unsigned BitWidth = Ty->isIntOrIntVectorTy()
4056  ? Ty->getScalarSizeInBits()
4057  : DL.getTypeSizeInBits(Ty->getScalarType());
4058 
4059  if (!BitWidth)
4060  return nullptr;
4061 
4062  KnownBits Op0Known(BitWidth);
4063  KnownBits Op1Known(BitWidth);
4064 
4065  if (SimplifyDemandedBits(&I, 0,
4066  getDemandedBitsLHSMask(I, BitWidth),
4067  Op0Known, 0))
4068  return &I;
4069 
4070  if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4071  Op1Known, 0))
4072  return &I;
4073 
4074  // Given the known and unknown bits, compute a range that the LHS could be
4075  // in. Compute the Min, Max and RHS values based on the known bits. For the
4076  // EQ and NE we use unsigned values.
4077  APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4078  APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4079  if (I.isSigned()) {
4080  computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4081  computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4082  } else {
4083  computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4084  computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4085  }
4086 
4087  // If Min and Max are known to be the same, then SimplifyDemandedBits
4088  // figured out that the LHS is a constant. Constant fold this now, so that
4089  // code below can assume that Min != Max.
4090  if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4091  return new ICmpInst(Pred, ConstantInt::get(Op0->getType(), Op0Min), Op1);
4092  if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4093  return new ICmpInst(Pred, Op0, ConstantInt::get(Op1->getType(), Op1Min));
4094 
4095  // Based on the range information we know about the LHS, see if we can
4096  // simplify this comparison. For example, (x&4) < 8 is always true.
4097  switch (Pred) {
4098  default:
4099  llvm_unreachable("Unknown icmp opcode!");
4100  case ICmpInst::ICMP_EQ:
4101  case ICmpInst::ICMP_NE: {
4102  if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4103  return Pred == CmpInst::ICMP_EQ
4104  ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4105  : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4106  }
4107 
4108  // If all bits are known zero except for one, then we know at most one bit
4109  // is set. If the comparison is against zero, then this is a check to see if
4110  // *that* bit is set.
4111  APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4112  if (Op1Known.isZero()) {
4113  // If the LHS is an AND with the same constant, look through it.
4114  Value *LHS = nullptr;
4115  const APInt *LHSC;
4116  if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4117  *LHSC != Op0KnownZeroInverted)
4118  LHS = Op0;
4119 
4120  Value *X;
4121  if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4122  APInt ValToCheck = Op0KnownZeroInverted;
4123  Type *XTy = X->getType();
4124  if (ValToCheck.isPowerOf2()) {
4125  // ((1 << X) & 8) == 0 -> X != 3
4126  // ((1 << X) & 8) != 0 -> X == 3
4127  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4128  auto NewPred = ICmpInst::getInversePredicate(Pred);
4129  return new ICmpInst(NewPred, X, CmpC);
4130  } else if ((++ValToCheck).isPowerOf2()) {
4131  // ((1 << X) & 7) == 0 -> X >= 3
4132  // ((1 << X) & 7) != 0 -> X < 3
4133  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4134  auto NewPred =
4136  return new ICmpInst(NewPred, X, CmpC);
4137  }
4138  }
4139 
4140  // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4141  const APInt *CI;
4142  if (Op0KnownZeroInverted.isOneValue() &&
4143  match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4144  // ((8 >>u X) & 1) == 0 -> X != 3
4145  // ((8 >>u X) & 1) != 0 -> X == 3
4146  unsigned CmpVal = CI->countTrailingZeros();
4147  auto NewPred = ICmpInst::getInversePredicate(Pred);
4148  return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4149  }
4150  }
4151  break;
4152  }
4153  case ICmpInst::ICMP_ULT: {
4154  if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4155  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4156  if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4157  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4158  if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4159  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4160 
4161  const APInt *CmpC;
4162  if (match(Op1, m_APInt(CmpC))) {
4163  // A <u C -> A == C-1 if min(A)+1 == C
4164  if (*CmpC == Op0Min + 1)
4165  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4166  ConstantInt::get(Op1->getType(), *CmpC - 1));
4167  // X <u C --> X == 0, if the number of zero bits in the bottom of X
4168  // exceeds the log2 of C.
4169  if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
4170  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4171  Constant::getNullValue(Op1->getType()));
4172  }
4173  break;
4174  }
4175  case ICmpInst::ICMP_UGT: {
4176  if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4177  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4178  if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4179  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4180  if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4181  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4182 
4183  const APInt *CmpC;
4184  if (match(Op1, m_APInt(CmpC))) {
4185  // A >u C -> A == C+1 if max(a)-1 == C
4186  if (*CmpC == Op0Max - 1)
4187  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4188  ConstantInt::get(Op1->getType(), *CmpC + 1));
4189  // X >u C --> X != 0, if the number of zero bits in the bottom of X
4190  // exceeds the log2 of C.
4191  if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
4192  return new ICmpInst(ICmpInst::ICMP_NE, Op0,
4193  Constant::getNullValue(Op1->getType()));
4194  }
4195  break;
4196  }
4197  case ICmpInst::ICMP_SLT: {
4198  if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4199  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4200  if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4201  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4202  if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4203  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4204  const APInt *CmpC;
4205  if (match(Op1, m_APInt(CmpC))) {
4206  if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4207  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4208  ConstantInt::get(Op1->getType(), *CmpC - 1));
4209  }
4210  break;
4211  }
4212  case ICmpInst::ICMP_SGT: {
4213  if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4214  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4215  if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4216  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4217  if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4218  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4219  const APInt *CmpC;
4220  if (match(Op1, m_APInt(CmpC))) {
4221  if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4222  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4223  ConstantInt::get(Op1->getType(), *CmpC + 1));
4224  }
4225  break;
4226  }
4227  case ICmpInst::ICMP_SGE:
4228  assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
4229  if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4230  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4231  if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4232  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4233  if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
4234  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4235  break;
4236  case ICmpInst::ICMP_SLE:
4237  assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
4238  if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4239  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4240  if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4241  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4242  if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
4243  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4244  break;
4245  case ICmpInst::ICMP_UGE:
4246  assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
4247  if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4248  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4249  if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4250  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4251  if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
4252  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4253  break;
4254  case ICmpInst::ICMP_ULE:
4255  assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
4256  if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4257  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4258  if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4259  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4260  if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
4261  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4262  break;
4263  }
4264 
4265  // Turn a signed comparison into an unsigned one if both operands are known to
4266  // have the same sign.
4267  if (I.isSigned() &&
4268  ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4269  (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4270  return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4271 
4272  return nullptr;
4273 }
4274 
4275 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
4276 /// it into the appropriate icmp lt or icmp gt instruction. This transform
4277 /// allows them to be folded in visitICmpInst.
4279  ICmpInst::Predicate Pred = I.getPredicate();
4280  if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4281  Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4282  return nullptr;
4283 
4284  Value *Op0 = I.getOperand(0);
4285  Value *Op1 = I.getOperand(1);
4286  auto *Op1C = dyn_cast<Constant>(Op1);
4287  if (!Op1C)
4288  return nullptr;
4289 
4290  // Check if the constant operand can be safely incremented/decremented without
4291  // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4292  // the edge cases for us, so we just assert on them. For vectors, we must
4293  // handle the edge cases.
4294  Type *Op1Type = Op1->getType();
4295  bool IsSigned = I.isSigned();
4296  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4297  auto *CI = dyn_cast<ConstantInt>(Op1C);
4298  if (CI) {
4299  // A <= MAX -> TRUE ; A >= MIN -> TRUE
4300  assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
4301  } else if (Op1Type->isVectorTy()) {
4302  // TODO? If the edge cases for vectors were guaranteed to be handled as they
4303  // are for scalar, we could remove the min/max checks. However, to do that,
4304  // we would have to use insertelement/shufflevector to replace edge values.
4305  unsigned NumElts = Op1Type->getVectorNumElements();
4306  for (unsigned i = 0; i != NumElts; ++i) {
4307  Constant *Elt = Op1C->getAggregateElement(i);
4308  if (!Elt)
4309  return nullptr;
4310 
4311  if (isa<UndefValue>(Elt))
4312  continue;
4313 
4314  // Bail out if we can't determine if this constant is min/max or if we
4315  // know that this constant is min/max.
4316  auto *CI = dyn_cast<ConstantInt>(Elt);
4317  if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4318  return nullptr;
4319  }
4320  } else {
4321  // ConstantExpr?
4322  return nullptr;
4323  }
4324 
4325  // Increment or decrement the constant and set the new comparison predicate:
4326  // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4327  Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4329  NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4330  return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4331 }
4332 
4333 /// Integer compare with boolean values can always be turned into bitwise ops.
4335  InstCombiner::BuilderTy &Builder) {
4336  Value *A = I.getOperand(0), *B = I.getOperand(1);
4337  assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
4338 
4339  // A boolean compared to true/false can be simplified to Op0/true/false in
4340  // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
4341  // Cases not handled by InstSimplify are always 'not' of Op0.
4342  if (match(B, m_Zero())) {
4343  switch (I.getPredicate()) {
4344  case CmpInst::ICMP_EQ: // A == 0 -> !A
4345  case CmpInst::ICMP_ULE: // A <=u 0 -> !A
4346  case CmpInst::ICMP_SGE: // A >=s 0 -> !A
4347  return BinaryOperator::CreateNot(A);
4348  default:
4349  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4350  }
4351  } else if (match(B, m_One())) {
4352  switch (I.getPredicate()) {
4353  case CmpInst::ICMP_NE: // A != 1 -> !A
4354  case CmpInst::ICMP_ULT: // A <u 1 -> !A
4355  case CmpInst::ICMP_SGT: // A >s -1 -> !A
4356  return BinaryOperator::CreateNot(A);
4357  default:
4358  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4359  }
4360  }
4361 
4362  switch (I.getPredicate()) {
4363  default:
4364  llvm_unreachable("Invalid icmp instruction!");
4365  case ICmpInst::ICMP_EQ:
4366  // icmp eq i1 A, B -> ~(A ^ B)
4367  return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
4368 
4369  case ICmpInst::ICMP_NE:
4370  // icmp ne i1 A, B -> A ^ B
4371  return BinaryOperator::CreateXor(A, B);
4372 
4373  case ICmpInst::ICMP_UGT:
4374  // icmp ugt -> icmp ult
4375  std::swap(A, B);
4377  case ICmpInst::ICMP_ULT:
4378  // icmp ult i1 A, B -> ~A & B
4379  return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
4380 
4381  case ICmpInst::ICMP_SGT:
4382  // icmp sgt -> icmp slt
4383  std::swap(A, B);
4385  case ICmpInst::ICMP_SLT:
4386  // icmp slt i1 A, B -> A & ~B
4387  return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
4388 
4389  case ICmpInst::ICMP_UGE:
4390  // icmp uge -> icmp ule
4391  std::swap(A, B);
4393  case ICmpInst::ICMP_ULE:
4394  // icmp ule i1 A, B -> ~A | B
4395  return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
4396 
4397  case ICmpInst::ICMP_SGE:
4398  // icmp sge -> icmp sle
4399  std::swap(A, B);
4401  case ICmpInst::ICMP_SLE:
4402  // icmp sle i1 A, B -> A | ~B
4403  return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
4404  }
4405 }
4406 
4408  bool Changed = false;
4409  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4410  unsigned Op0Cplxity = getComplexity(Op0);
4411  unsigned Op1Cplxity = getComplexity(Op1);
4412 
4413  /// Orders the operands of the compare so that they are listed from most
4414  /// complex to least complex. This puts constants before unary operators,
4415  /// before binary operators.
4416  if (Op0Cplxity < Op1Cplxity ||
4417  (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4418  I.swapOperands();
4419  std::swap(Op0, Op1);
4420  Changed = true;
4421  }
4422 
4423  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4424  SQ.getWithInstruction(&I)))
4425  return replaceInstUsesWith(I, V);
4426 
4427  // Comparing -val or val with non-zero is the same as just comparing val
4428  // ie, abs(val) != 0 -> val != 0
4429  if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4430  Value *Cond, *SelectTrue, *SelectFalse;
4431  if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4432  m_Value(SelectFalse)))) {
4433  if (Value *V = dyn_castNegVal(SelectTrue)) {
4434  if (V == SelectFalse)
4435  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4436  }
4437  else if (Value *V = dyn_castNegVal(SelectFalse)) {
4438  if (V == SelectTrue)
4439  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4440  }
4441  }
4442  }
4443 
4444  if (Op0->getType()->isIntOrIntVectorTy(1))
4445  if (Instruction *Res = canonicalizeICmpBool(I, Builder))
4446  return Res;
4447 
4448  if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4449  return NewICmp;
4450 
4451  if (Instruction *Res = foldICmpWithConstant(I))
4452  return Res;
4453 
4454  if (Instruction *Res = foldICmpUsingKnownBits(I))
4455  return Res;
4456 
4457  // Test if the ICmpInst instruction is used exclusively by a select as
4458  // part of a minimum or maximum operation. If so, refrain from doing
4459  // any other folding. This helps out other analyses which understand
4460  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4461  // and CodeGen. And in this case, at least one of the comparison
4462  // operands has at least one user besides the compare (the select),
4463  // which would often largely negate the benefit of folding anyway.
4464  //
4465  // Do the same for the other patterns recognized by matchSelectPattern.
4466  if (I.hasOneUse())
4467  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4468  Value *A, *B;
4469  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4470  if (SPR.Flavor != SPF_UNKNOWN)
4471  return nullptr;
4472  }
4473 
4474  // Do this after checking for min/max to prevent infinite looping.
4475  if (Instruction *Res = foldICmpWithZero(I))
4476  return Res;
4477 
4478  // FIXME: We only do this after checking for min/max to prevent infinite
4479  // looping caused by a reverse canonicalization of these patterns for min/max.
4480  // FIXME: The organization of folds is a mess. These would naturally go into
4481  // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4482  // down here after the min/max restriction.
4483  ICmpInst::Predicate Pred = I.getPredicate();
4484  const APInt *C;
4485  if (match(Op1, m_APInt(C))) {
4486  // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4487  if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4488  Constant *Zero = Constant::getNullValue(Op0->getType());
4489  return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4490  }
4491 
4492  // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4493  if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4494  Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4495  return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4496  }
4497  }
4498 
4499  if (Instruction *Res = foldICmpInstWithConstant(I))
4500  return Res;
4501 
4502  if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4503  return Res;
4504 
4505  // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4506  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4507  if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4508  return NI;
4509  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4510  if (Instruction *NI = foldGEPICmp(GEP, Op0,
4512  return NI;
4513 
4514  // Try to optimize equality comparisons against alloca-based pointers.
4515  if (Op0->getType()->isPointerTy() && I.isEquality()) {
4516  assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
4517  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4518  if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4519  return New;
4520  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4521  if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4522  return New;
4523  }
4524 
4525  // Test to see if the operands of the icmp are casted versions of other
4526  // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4527  // now.
4528  if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4529  if (Op0->getType()->isPointerTy() &&
4530  (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4531  // We keep moving the cast from the left operand over to the right
4532  // operand, where it can often be eliminated completely.
4533  Op0 = CI->getOperand(0);
4534 
4535  // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4536  // so eliminate it as well.
4537  if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4538  Op1 = CI2->getOperand(0);
4539 
4540  // If Op1 is a constant, we can fold the cast into the constant.
4541  if (Op0->getType() != Op1->getType()) {
4542  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4543  Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4544  } else {
4545  // Otherwise, cast the RHS right before the icmp
4546  Op1 = Builder.CreateBitCast(Op1, Op0->getType());
4547  }
4548  }
4549  return new ICmpInst(I.getPredicate(), Op0, Op1);
4550  }
4551  }
4552 
4553  if (isa<CastInst>(Op0)) {
4554  // Handle the special case of: icmp (cast bool to X), <cst>
4555  // This comes up when you have code like
4556  // int X = A < B;
4557  // if (X) ...
4558  // For generality, we handle any zero-extension of any operand comparison
4559  // with a constant or another cast from the same type.
4560  if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4561  if (Instruction *R = foldICmpWithCastAndCast(I))
4562  return R;
4563  }
4564 
4565  if (Instruction *Res = foldICmpBinOp(I))
4566  return Res;
4567 
4568  if (Instruction *Res = foldICmpWithMinMax(I))
4569  return Res;
4570 
4571  {
4572  Value *A, *B;
4573  // Transform (A & ~B) == 0 --> (A & B) != 0
4574  // and (A & ~B) != 0 --> (A & B) == 0
4575  // if A is a power of 2.
4576  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4577  match(Op1, m_Zero()) &&
4578  isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
4579  return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
4580  Op1);
4581 
4582  // ~X < ~Y --> Y < X
4583  // ~X < C --> X > ~C
4584  if (match(Op0, m_Not(m_Value(A)))) {
4585  if (match(Op1, m_Not(m_Value(B))))
4586  return new ICmpInst(I.getPredicate(), B, A);
4587 
4588  const APInt *C;
4589  if (match(Op1, m_APInt(C)))
4590  return new ICmpInst(I.getSwappedPredicate(), A,
4591  ConstantInt::get(Op1->getType(), ~(*C)));
4592  }
4593 
4594  Instruction *AddI = nullptr;
4595  if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4596  m_Instruction(AddI))) &&
4597  isa<IntegerType>(A->getType())) {
4598  Value *Result;
4599  Constant *Overflow;
4600  if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4601  Overflow)) {
4602  replaceInstUsesWith(*AddI, Result);
4603  return replaceInstUsesWith(I, Overflow);
4604  }
4605  }
4606 
4607  // (zext a) * (zext b) --> llvm.umul.with.overflow.
4608  if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4609  if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4610  return R;
4611  }
4612  if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4613  if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4614  return R;
4615  }
4616  }
4617 
4618  if (Instruction *Res = foldICmpEquality(I))
4619  return Res;
4620 
4621  // The 'cmpxchg' instruction returns an aggregate containing the old value and
4622  // an i1 which indicates whether or not we successfully did the swap.
4623  //
4624  // Replace comparisons between the old value and the expected value with the
4625  // indicator that 'cmpxchg' returns.
4626  //
4627  // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4628  // spuriously fail. In those cases, the old value may equal the expected
4629  // value but it is possible for the swap to not occur.
4630  if (I.getPredicate() == ICmpInst::ICMP_EQ)
4631  if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4632  if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4633  if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4634  !ACXI->isWeak())
4635  return ExtractValueInst::Create(ACXI, 1);
4636 
4637  {
4638  Value *X; ConstantInt *Cst;
4639  // icmp X+Cst, X
4640  if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4641  return foldICmpAddOpConst(X, Cst, I.getPredicate());
4642 
4643  // icmp X, X+Cst
4644  if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4645  return foldICmpAddOpConst(X, Cst, I.getSwappedPredicate());
4646  }
4647  return Changed ? &I : nullptr;
4648 }
4649 
4650 /// Fold fcmp ([us]itofp x, cst) if possible.
4651 Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4652  Constant *RHSC) {
4653  if (!isa<ConstantFP>(RHSC)) return nullptr;
4654  const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4655 
4656  // Get the width of the mantissa. We don't want to hack on conversions that
4657  // might lose information from the integer, e.g. "i64 -> float"
4658  int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4659  if (MantissaWidth == -1) return nullptr; // Unknown.
4660 
4661  IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4662 
4663  bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4664 
4665  if (I.isEquality()) {
4667  bool IsExact = false;
4668  APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4669  RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4670 
4671  // If the floating point constant isn't an integer value, we know if we will
4672  // ever compare equal / not equal to it.
4673  if (!IsExact) {
4674  // TODO: Can never be -0.0 and other non-representable values
4675  APFloat RHSRoundInt(RHS);
4677  if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4678  if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4679  return replaceInstUsesWith(I, Builder.getFalse());
4680 
4682  return replaceInstUsesWith(I, Builder.getTrue());
4683  }
4684  }
4685 
4686  // TODO: If the constant is exactly representable, is it always OK to do
4687  // equality compares as integer?
4688  }
4689 
4690  // Check to see that the input is converted from an integer type that is small
4691  // enough that preserves all bits. TODO: check here for "known" sign bits.
4692  // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4693  unsigned InputSize = IntTy->getScalarSizeInBits();
4694 
4695  // Following test does NOT adjust InputSize downwards for signed inputs,
4696  // because the most negative value still requires all the mantissa bits
4697  // to distinguish it from one less than that value.
4698  if ((int)InputSize > MantissaWidth) {
4699  // Conversion would lose accuracy. Check if loss can impact comparison.
4700  int Exp = ilogb(RHS);
4701  if (Exp == APFloat::IEK_Inf) {
4702  int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4703  if (MaxExponent < (int)InputSize - !LHSUnsigned)
4704  // Conversion could create infinity.
4705  return nullptr;
4706  } else {
4707  // Note that if RHS is zero or NaN, then Exp is negative
4708  // and first condition is trivially false.
4709  if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4710  // Conversion could affect comparison.
4711  return nullptr;
4712  }
4713  }
4714 
4715  // Otherwise, we can potentially simplify the comparison. We know that it
4716  // will always come through as an integer value and we know the constant is
4717  // not a NAN (it would have been previously simplified).
4718  assert(!RHS.isNaN() && "NaN comparison not already folded!");
4719 
4720  ICmpInst::Predicate Pred;
4721  switch (I.getPredicate()) {
4722  default: llvm_unreachable("Unexpected predicate!");
4723  case FCmpInst::FCMP_UEQ:
4724  case FCmpInst::FCMP_OEQ:
4725  Pred = ICmpInst::ICMP_EQ;
4726  break;
4727  case FCmpInst::FCMP_UGT:
4728  case FCmpInst::FCMP_OGT:
4729  Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4730  break;
4731  case FCmpInst::FCMP_UGE:
4732  case FCmpInst::FCMP_OGE:
4733  Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4734  break;
4735  case FCmpInst::FCMP_ULT:
4736  case FCmpInst::FCMP_OLT:
4737  Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4738  break;
4739  case FCmpInst::FCMP_ULE:
4740  case FCmpInst::FCMP_OLE:
4741  Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4742  break;
4743  case FCmpInst::FCMP_UNE:
4744  case FCmpInst::FCMP_ONE:
4745  Pred = ICmpInst::ICMP_NE;
4746  break;
4747  case FCmpInst::FCMP_ORD:
4748  return replaceInstUsesWith(I, Builder.getTrue());
4749  case FCmpInst::FCMP_UNO:
4750  return replaceInstUsesWith(I, Builder.getFalse());
4751  }
4752 
4753  // Now we know that the APFloat is a normal number, zero or inf.
4754 
4755  // See if the FP constant is too large for the integer. For example,
4756  // comparing an i8 to 300.0.
4757  unsigned IntWidth = IntTy->getScalarSizeInBits();
4758 
4759  if (!LHSUnsigned) {
4760  // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4761  // and large values.
4762  APFloat SMax(RHS.getSemantics());
4763  SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4765  if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4766  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4767  Pred == ICmpInst::ICMP_SLE)
4768  return replaceInstUsesWith(I, Builder.getTrue());
4769  return replaceInstUsesWith(I, Builder.getFalse());
4770  }
4771  } else {
4772  // If the RHS value is > UnsignedMax, fold the comparison. This handles
4773  // +INF and large values.
4774  APFloat UMax(RHS.getSemantics());
4775  UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4777  if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4778  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4779  Pred == ICmpInst::ICMP_ULE)
4780  return replaceInstUsesWith(I, Builder.getTrue());
4781  return replaceInstUsesWith(I, Builder.getFalse());
4782  }
4783  }
4784 
4785  if (!LHSUnsigned) {
4786  // See if the RHS value is < SignedMin.
4787  APFloat SMin(RHS.getSemantics());
4788  SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4790  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4791  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4792  Pred == ICmpInst::ICMP_SGE)
4793  return replaceInstUsesWith(I, Builder.getTrue());
4794  return replaceInstUsesWith(I, Builder.getFalse());
4795  }
4796  } else {
4797  // See if the RHS value is < UnsignedMin.
4798  APFloat SMin(RHS.getSemantics());
4799  SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4801  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4802  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4803  Pred == ICmpInst::ICMP_UGE)
4804  return replaceInstUsesWith(I, Builder.getTrue());
4805  return replaceInstUsesWith(I, Builder.getFalse());
4806  }
4807  }
4808 
4809  // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4810  // [0, UMAX], but it may still be fractional. See if it is fractional by
4811  // casting the FP value to the integer value and back, checking for equality.
4812  // Don't do this for zero, because -0.0 is not fractional.
4813  Constant *RHSInt = LHSUnsigned
4814  ? ConstantExpr::getFPToUI(RHSC, IntTy)
4815  : ConstantExpr::getFPToSI(RHSC, IntTy);
4816  if (!RHS.isZero()) {
4817  bool Equal = LHSUnsigned
4818  ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4819  : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4820  if (!Equal) {
4821  // If we had a comparison against a fractional value, we have to adjust
4822  // the compare predicate and sometimes the value. RHSC is rounded towards
4823  // zero at this point.
4824  switch (Pred) {
4825  default: llvm_unreachable("Unexpected integer comparison!");
4826  case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4827  return replaceInstUsesWith(I, Builder.getTrue());
4828  case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4829  return replaceInstUsesWith(I, Builder.getFalse());
4830  case ICmpInst::ICMP_ULE:
4831  // (float)int <= 4.4 --> int <= 4
4832  // (float)int <= -4.4 --> false
4833  if (RHS.isNegative())
4834  return replaceInstUsesWith(I, Builder.getFalse());
4835  break;
4836  case ICmpInst::ICMP_SLE:
4837  // (float)int <= 4.4 --> int <= 4
4838  // (float)int <= -4.4 --> int < -4
4839  if (RHS.isNegative())
4840  Pred = ICmpInst::ICMP_SLT;
4841  break;
4842  case ICmpInst::ICMP_ULT:
4843  // (float)int < -4.4 --> false
4844  // (float)int < 4.4 --> int <= 4
4845  if (RHS.isNegative())
4846  return replaceInstUsesWith(I, Builder.getFalse());
4847  Pred = ICmpInst::ICMP_ULE;
4848  break;
4849  case ICmpInst::ICMP_SLT:
4850  // (float)int < -4.4 --> int < -4
4851  // (float)int < 4.4 --> int <= 4
4852  if (!RHS.isNegative())
4853  Pred = ICmpInst::ICMP_SLE;
4854  break;
4855  case ICmpInst::ICMP_UGT:
4856  // (float)int > 4.4 --> int > 4
4857  // (float)int > -4.4 --> true
4858  if (RHS.isNegative())
4859  return replaceInstUsesWith(I, Builder.getTrue());
4860  break;
4861  case ICmpInst::ICMP_SGT:
4862  // (float)int > 4.4 --> int > 4
4863  // (float)int > -4.4 --> int >= -4
4864  if (RHS.isNegative())
4865  Pred = ICmpInst::ICMP_SGE;
4866  break;
4867  case ICmpInst::ICMP_UGE:
4868  // (float)int >= -4.4 --> true
4869  // (float)int >= 4.4 --> int > 4
4870  if (RHS.isNegative())
4871  return replaceInstUsesWith(I, Builder.getTrue());
4872  Pred = ICmpInst::ICMP_UGT;
4873  break;
4874  case ICmpInst::ICMP_SGE:
4875  // (float)int >= -4.4 --> int >= -4
4876  // (float)int >= 4.4 --> int > 4
4877  if (!RHS.isNegative())
4878  Pred = ICmpInst::ICMP_SGT;
4879  break;
4880  }
4881  }
4882  }
4883 
4884  // Lower this FP comparison into an appropriate integer version of the
4885  // comparison.
4886  return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4887 }
4888 
4890  bool Changed = false;
4891 
4892  /// Orders the operands of the compare so that they are listed from most
4893  /// complex to least complex. This puts constants before unary operators,
4894  /// before binary operators.
4895  if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4896  I.swapOperands();
4897  Changed = true;
4898  }
4899 
4900  const CmpInst::Predicate Pred = I.getPredicate();
4901  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4902  if (Value *V = SimplifyFCmpInst(Pred, Op0, Op1, I.getFastMathFlags(),
4903  SQ.getWithInstruction(&I)))
4904  return replaceInstUsesWith(I, V);
4905 
4906  // Simplify 'fcmp pred X, X'
4907  if (Op0 == Op1) {
4908  switch (Pred) {
4909  default: break;
4910  case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4911  case FCmpInst::FCMP_ULT: // True if unordered or less than
4912  case FCmpInst::FCMP_UGT: // True if unordered or greater than
4913  case FCmpInst::FCMP_UNE: // True if unordered or not equal
4914  // Canonicalize these to be 'fcmp uno %X, 0.0'.
4917  return &I;
4918 
4919  case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4920  case FCmpInst::FCMP_OEQ: // True if ordered and equal
4921  case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4922  case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4923  // Canonicalize these to be 'fcmp ord %X, 0.0'.
4926  return &I;
4927  }
4928  }
4929 
4930  // If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
4931  // then canonicalize the operand to 0.0.
4932  if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
4933  if (!match(Op0, m_Zero()) && isKnownNeverNaN(Op0)) {
4935  return &I;
4936  }
4937  if (!match(Op1, m_Zero()) && isKnownNeverNaN(Op1)) {
4939  return &I;
4940  }
4941  }
4942 
4943  // Test if the FCmpInst instruction is used exclusively by a select as
4944  // part of a minimum or maximum operation. If so, refrain from doing
4945  // any other folding. This helps out other analyses which understand
4946  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4947  // and CodeGen. And in this case, at least one of the comparison
4948  // operands has at least one user besides the compare (the select),
4949  // which would often largely negate the benefit of folding anyway.
4950  if (I.hasOneUse())
4951  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4952  Value *A, *B;
4953  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4954  if (SPR.Flavor != SPF_UNKNOWN)
4955  return nullptr;
4956  }
4957 
4958  // Handle fcmp with constant RHS
4959  if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4960  if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4961  switch (LHSI->getOpcode()) {
4962  case Instruction::FPExt: {
4963  // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
4964  FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
4965  ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
4966  if (!RHSF)
4967  break;
4968 
4969  const fltSemantics *Sem;
4970  // FIXME: This shouldn't be here.
4971  if (LHSExt->getSrcTy()->isHalfTy())
4972  Sem = &APFloat::IEEEhalf();
4973  else if (LHSExt->getSrcTy()->isFloatTy())
4974  Sem = &APFloat::IEEEsingle();
4975  else if (LHSExt->getSrcTy()->isDoubleTy())
4976  Sem = &APFloat::IEEEdouble();
4977  else if (LHSExt->getSrcTy()->isFP128Ty())
4978  Sem = &APFloat::IEEEquad();
4979  else if (LHSExt->getSrcTy()->isX86_FP80Ty())
4980  Sem = &APFloat::x87DoubleExtended();
4981  else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
4982  Sem = &APFloat::PPCDoubleDouble();
4983  else
4984  break;
4985 
4986  bool Lossy;
4987  APFloat F = RHSF->getValueAPF();
4988  F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
4989 
4990  // Avoid lossy conversions and denormals. Zero is a special case
4991  // that's OK to convert.
4992  APFloat Fabs = F;
4993  Fabs.clearSign();
4994  if (!Lossy &&
4995  ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
4996  APFloat::cmpLessThan) || Fabs.isZero()))
4997 
4998  return new FCmpInst(Pred, LHSExt->getOperand(0),
4999  ConstantFP::get(RHSC->getContext(), F));
5000  break;
5001  }
5002  case Instruction::PHI:
5003  // Only fold fcmp into the PHI if the phi and fcmp are in the same
5004  // block. If in the same block, we're encouraging jump threading. If
5005  // not, we are just pessimizing the code by making an i1 phi.
5006  if (LHSI->getParent() == I.getParent())
5007  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
5008  return NV;
5009  break;
5010  case Instruction::SIToFP:
5011  case Instruction::UIToFP:
5012  if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
5013  return NV;
5014  break;
5015  case Instruction::FSub: {
5016  // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
5017  Value *Op;
5018  if (match(LHSI, m_FNeg(m_Value(Op))))
5019  return new FCmpInst(I.getSwappedPredicate(), Op,
5020  ConstantExpr::getFNeg(RHSC));
5021  break;
5022  }
5023  case Instruction::Load:
5024  if (GetElementPtrInst *GEP =
5025  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
5026  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
5027  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
5028  !cast<LoadInst>(LHSI)->isVolatile())
5029  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
5030  return Res;
5031  }
5032  break;
5033  case Instruction::Call: {
5034  if (!RHSC->isNullValue())
5035  break;
5036 
5037  CallInst *CI = cast<CallInst>(LHSI);
5038  Intrinsic::ID IID = getIntrinsicForCallSite(CI, &TLI);
5039  if (IID != Intrinsic::fabs)
5040  break;
5041 
5042  // Various optimization for fabs compared with zero.
5043  switch (Pred) {
5044  default:
5045  break;
5046  // fabs(x) < 0 --> false
5047  case FCmpInst::FCMP_OLT:
5048  llvm_unreachable("handled by SimplifyFCmpInst");
5049  // fabs(x) > 0 --> x != 0
5050  case FCmpInst::FCMP_OGT:
5051  return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC);
5052  // fabs(x) <= 0 --> x == 0
5053  case FCmpInst::FCMP_OLE:
5054  return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC);
5055  // fabs(x) >= 0 --> !isnan(x)
5056  case FCmpInst::FCMP_OGE:
5057  return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC);
5058  // fabs(x) == 0 --> x == 0
5059  // fabs(x) != 0 --> x != 0
5060  case FCmpInst::FCMP_OEQ:
5061  case FCmpInst::FCMP_UEQ:
5062  case FCmpInst::FCMP_ONE:
5063  case FCmpInst::FCMP_UNE:
5064  return new FCmpInst(Pred, CI->getArgOperand(0), RHSC);
5065  }
5066  }
5067  }
5068  }
5069 
5070  // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
5071