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"
21 #include "llvm/IR/ConstantRange.h"
22 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/PatternMatch.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/KnownBits.h"
28 
29 using namespace llvm;
30 using namespace PatternMatch;
31 
32 #define DEBUG_TYPE "instcombine"
33 
34 // How many times is a select replaced by one of its operands?
35 STATISTIC(NumSel, "Number of select opts");
36 
37 
38 /// Compute Result = In1+In2, returning true if the result overflowed for this
39 /// type.
40 static bool addWithOverflow(APInt &Result, const APInt &In1,
41  const APInt &In2, bool IsSigned = false) {
42  bool Overflow;
43  if (IsSigned)
44  Result = In1.sadd_ov(In2, Overflow);
45  else
46  Result = In1.uadd_ov(In2, Overflow);
47 
48  return Overflow;
49 }
50 
51 /// Compute Result = In1-In2, returning true if the result overflowed for this
52 /// type.
53 static bool subWithOverflow(APInt &Result, const APInt &In1,
54  const APInt &In2, bool IsSigned = false) {
55  bool Overflow;
56  if (IsSigned)
57  Result = In1.ssub_ov(In2, Overflow);
58  else
59  Result = In1.usub_ov(In2, Overflow);
60 
61  return Overflow;
62 }
63 
64 /// Given an icmp instruction, return true if any use of this comparison is a
65 /// branch on sign bit comparison.
66 static bool hasBranchUse(ICmpInst &I) {
67  for (auto *U : I.users())
68  if (isa<BranchInst>(U))
69  return true;
70  return false;
71 }
72 
73 /// Given an exploded icmp instruction, return true if the comparison only
74 /// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if the
75 /// result of the comparison is true when the input value is signed.
76 static bool isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
77  bool &TrueIfSigned) {
78  switch (Pred) {
79  case ICmpInst::ICMP_SLT: // True if LHS s< 0
80  TrueIfSigned = true;
81  return RHS.isNullValue();
82  case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
83  TrueIfSigned = true;
84  return RHS.isAllOnesValue();
85  case ICmpInst::ICMP_SGT: // True if LHS s> -1
86  TrueIfSigned = false;
87  return RHS.isAllOnesValue();
88  case ICmpInst::ICMP_UGT:
89  // True if LHS u> RHS and RHS == high-bit-mask - 1
90  TrueIfSigned = true;
91  return RHS.isMaxSignedValue();
92  case ICmpInst::ICMP_UGE:
93  // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
94  TrueIfSigned = true;
95  return RHS.isSignMask();
96  default:
97  return false;
98  }
99 }
100 
101 /// Returns true if the exploded icmp can be expressed as a signed comparison
102 /// to zero and updates the predicate accordingly.
103 /// The signedness of the comparison is preserved.
104 /// TODO: Refactor with decomposeBitTestICmp()?
105 static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
106  if (!ICmpInst::isSigned(Pred))
107  return false;
108 
109  if (C.isNullValue())
110  return ICmpInst::isRelational(Pred);
111 
112  if (C.isOneValue()) {
113  if (Pred == ICmpInst::ICMP_SLT) {
114  Pred = ICmpInst::ICMP_SLE;
115  return true;
116  }
117  } else if (C.isAllOnesValue()) {
118  if (Pred == ICmpInst::ICMP_SGT) {
119  Pred = ICmpInst::ICMP_SGE;
120  return true;
121  }
122  }
123 
124  return false;
125 }
126 
127 /// Given a signed integer type and a set of known zero and one bits, compute
128 /// the maximum and minimum values that could have the specified known zero and
129 /// known one bits, returning them in Min/Max.
130 /// TODO: Move to method on KnownBits struct?
132  APInt &Min, APInt &Max) {
133  assert(Known.getBitWidth() == Min.getBitWidth() &&
134  Known.getBitWidth() == Max.getBitWidth() &&
135  "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
136  APInt UnknownBits = ~(Known.Zero|Known.One);
137 
138  // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
139  // bit if it is unknown.
140  Min = Known.One;
141  Max = Known.One|UnknownBits;
142 
143  if (UnknownBits.isNegative()) { // Sign bit is unknown
144  Min.setSignBit();
145  Max.clearSignBit();
146  }
147 }
148 
149 /// Given an unsigned integer type and a set of known zero and one bits, compute
150 /// the maximum and minimum values that could have the specified known zero and
151 /// known one bits, returning them in Min/Max.
152 /// TODO: Move to method on KnownBits struct?
154  APInt &Min, APInt &Max) {
155  assert(Known.getBitWidth() == Min.getBitWidth() &&
156  Known.getBitWidth() == Max.getBitWidth() &&
157  "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
158  APInt UnknownBits = ~(Known.Zero|Known.One);
159 
160  // The minimum value is when the unknown bits are all zeros.
161  Min = Known.One;
162  // The maximum value is when the unknown bits are all ones.
163  Max = Known.One|UnknownBits;
164 }
165 
166 /// This is called when we see this pattern:
167 /// cmp pred (load (gep GV, ...)), cmpcst
168 /// where GV is a global variable with a constant initializer. Try to simplify
169 /// this into some simple computation that does not need the load. For example
170 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
171 ///
172 /// If AndCst is non-null, then the loaded value is masked with that constant
173 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
174 Instruction *InstCombiner::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
175  GlobalVariable *GV,
176  CmpInst &ICI,
177  ConstantInt *AndCst) {
178  Constant *Init = GV->getInitializer();
179  if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
180  return nullptr;
181 
182  uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
183  // Don't blow up on huge arrays.
184  if (ArrayElementCount > MaxArraySizeForCombine)
185  return nullptr;
186 
187  // There are many forms of this optimization we can handle, for now, just do
188  // the simple index into a single-dimensional array.
189  //
190  // Require: GEP GV, 0, i {{, constant indices}}
191  if (GEP->getNumOperands() < 3 ||
192  !isa<ConstantInt>(GEP->getOperand(1)) ||
193  !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
194  isa<Constant>(GEP->getOperand(2)))
195  return nullptr;
196 
197  // Check that indices after the variable are constants and in-range for the
198  // type they index. Collect the indices. This is typically for arrays of
199  // structs.
200  SmallVector<unsigned, 4> LaterIndices;
201 
202  Type *EltTy = Init->getType()->getArrayElementType();
203  for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
204  ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
205  if (!Idx) return nullptr; // Variable index.
206 
207  uint64_t IdxVal = Idx->getZExtValue();
208  if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
209 
210  if (StructType *STy = dyn_cast<StructType>(EltTy))
211  EltTy = STy->getElementType(IdxVal);
212  else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
213  if (IdxVal >= ATy->getNumElements()) return nullptr;
214  EltTy = ATy->getElementType();
215  } else {
216  return nullptr; // Unknown type.
217  }
218 
219  LaterIndices.push_back(IdxVal);
220  }
221 
222  enum { Overdefined = -3, Undefined = -2 };
223 
224  // Variables for our state machines.
225 
226  // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
227  // "i == 47 | i == 87", where 47 is the first index the condition is true for,
228  // and 87 is the second (and last) index. FirstTrueElement is -2 when
229  // undefined, otherwise set to the first true element. SecondTrueElement is
230  // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
231  int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
232 
233  // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
234  // form "i != 47 & i != 87". Same state transitions as for true elements.
235  int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
236 
237  /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
238  /// define a state machine that triggers for ranges of values that the index
239  /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
240  /// This is -2 when undefined, -3 when overdefined, and otherwise the last
241  /// index in the range (inclusive). We use -2 for undefined here because we
242  /// use relative comparisons and don't want 0-1 to match -1.
243  int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
244 
245  // MagicBitvector - This is a magic bitvector where we set a bit if the
246  // comparison is true for element 'i'. If there are 64 elements or less in
247  // the array, this will fully represent all the comparison results.
248  uint64_t MagicBitvector = 0;
249 
250  // Scan the array and see if one of our patterns matches.
251  Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
252  for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
253  Constant *Elt = Init->getAggregateElement(i);
254  if (!Elt) return nullptr;
255 
256  // If this is indexing an array of structures, get the structure element.
257  if (!LaterIndices.empty())
258  Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
259 
260  // If the element is masked, handle it.
261  if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
262 
263  // Find out if the comparison would be true or false for the i'th element.
265  CompareRHS, DL, &TLI);
266  // If the result is undef for this element, ignore it.
267  if (isa<UndefValue>(C)) {
268  // Extend range state machines to cover this element in case there is an
269  // undef in the middle of the range.
270  if (TrueRangeEnd == (int)i-1)
271  TrueRangeEnd = i;
272  if (FalseRangeEnd == (int)i-1)
273  FalseRangeEnd = i;
274  continue;
275  }
276 
277  // If we can't compute the result for any of the elements, we have to give
278  // up evaluating the entire conditional.
279  if (!isa<ConstantInt>(C)) return nullptr;
280 
281  // Otherwise, we know if the comparison is true or false for this element,
282  // update our state machines.
283  bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
284 
285  // State machine for single/double/range index comparison.
286  if (IsTrueForElt) {
287  // Update the TrueElement state machine.
288  if (FirstTrueElement == Undefined)
289  FirstTrueElement = TrueRangeEnd = i; // First true element.
290  else {
291  // Update double-compare state machine.
292  if (SecondTrueElement == Undefined)
293  SecondTrueElement = i;
294  else
295  SecondTrueElement = Overdefined;
296 
297  // Update range state machine.
298  if (TrueRangeEnd == (int)i-1)
299  TrueRangeEnd = i;
300  else
301  TrueRangeEnd = Overdefined;
302  }
303  } else {
304  // Update the FalseElement state machine.
305  if (FirstFalseElement == Undefined)
306  FirstFalseElement = FalseRangeEnd = i; // First false element.
307  else {
308  // Update double-compare state machine.
309  if (SecondFalseElement == Undefined)
310  SecondFalseElement = i;
311  else
312  SecondFalseElement = Overdefined;
313 
314  // Update range state machine.
315  if (FalseRangeEnd == (int)i-1)
316  FalseRangeEnd = i;
317  else
318  FalseRangeEnd = Overdefined;
319  }
320  }
321 
322  // If this element is in range, update our magic bitvector.
323  if (i < 64 && IsTrueForElt)
324  MagicBitvector |= 1ULL << i;
325 
326  // If all of our states become overdefined, bail out early. Since the
327  // predicate is expensive, only check it every 8 elements. This is only
328  // really useful for really huge arrays.
329  if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
330  SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
331  FalseRangeEnd == Overdefined)
332  return nullptr;
333  }
334 
335  // Now that we've scanned the entire array, emit our new comparison(s). We
336  // order the state machines in complexity of the generated code.
337  Value *Idx = GEP->getOperand(2);
338 
339  // If the index is larger than the pointer size of the target, truncate the
340  // index down like the GEP would do implicitly. We don't have to do this for
341  // an inbounds GEP because the index can't be out of range.
342  if (!GEP->isInBounds()) {
343  Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
344  unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
345  if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
346  Idx = Builder.CreateTrunc(Idx, IntPtrTy);
347  }
348 
349  // If the comparison is only true for one or two elements, emit direct
350  // comparisons.
351  if (SecondTrueElement != Overdefined) {
352  // None true -> false.
353  if (FirstTrueElement == Undefined)
354  return replaceInstUsesWith(ICI, Builder.getFalse());
355 
356  Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
357 
358  // True for one element -> 'i == 47'.
359  if (SecondTrueElement == Undefined)
360  return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
361 
362  // True for two elements -> 'i == 47 | i == 72'.
363  Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
364  Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
365  Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
366  return BinaryOperator::CreateOr(C1, C2);
367  }
368 
369  // If the comparison is only false for one or two elements, emit direct
370  // comparisons.
371  if (SecondFalseElement != Overdefined) {
372  // None false -> true.
373  if (FirstFalseElement == Undefined)
374  return replaceInstUsesWith(ICI, Builder.getTrue());
375 
376  Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
377 
378  // False for one element -> 'i != 47'.
379  if (SecondFalseElement == Undefined)
380  return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
381 
382  // False for two elements -> 'i != 47 & i != 72'.
383  Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
384  Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
385  Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
386  return BinaryOperator::CreateAnd(C1, C2);
387  }
388 
389  // If the comparison can be replaced with a range comparison for the elements
390  // where it is true, emit the range check.
391  if (TrueRangeEnd != Overdefined) {
392  assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
393 
394  // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
395  if (FirstTrueElement) {
396  Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
397  Idx = Builder.CreateAdd(Idx, Offs);
398  }
399 
400  Value *End = ConstantInt::get(Idx->getType(),
401  TrueRangeEnd-FirstTrueElement+1);
402  return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
403  }
404 
405  // False range check.
406  if (FalseRangeEnd != Overdefined) {
407  assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
408  // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
409  if (FirstFalseElement) {
410  Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
411  Idx = Builder.CreateAdd(Idx, Offs);
412  }
413 
414  Value *End = ConstantInt::get(Idx->getType(),
415  FalseRangeEnd-FirstFalseElement);
416  return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
417  }
418 
419  // If a magic bitvector captures the entire comparison state
420  // of this load, replace it with computation that does:
421  // ((magic_cst >> i) & 1) != 0
422  {
423  Type *Ty = nullptr;
424 
425  // Look for an appropriate type:
426  // - The type of Idx if the magic fits
427  // - The smallest fitting legal type
428  if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
429  Ty = Idx->getType();
430  else
431  Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
432 
433  if (Ty) {
434  Value *V = Builder.CreateIntCast(Idx, Ty, false);
435  V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
436  V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
437  return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
438  }
439  }
440 
441  return nullptr;
442 }
443 
444 /// Return a value that can be used to compare the *offset* implied by a GEP to
445 /// zero. For example, if we have &A[i], we want to return 'i' for
446 /// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
447 /// are involved. The above expression would also be legal to codegen as
448 /// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
449 /// This latter form is less amenable to optimization though, and we are allowed
450 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
451 ///
452 /// If we can't emit an optimized form for this expression, this returns null.
453 ///
455  const DataLayout &DL) {
457 
458  // Check to see if this gep only has a single variable index. If so, and if
459  // any constant indices are a multiple of its scale, then we can compute this
460  // in terms of the scale of the variable index. For example, if the GEP
461  // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
462  // because the expression will cross zero at the same point.
463  unsigned i, e = GEP->getNumOperands();
464  int64_t Offset = 0;
465  for (i = 1; i != e; ++i, ++GTI) {
466  if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
467  // Compute the aggregate offset of constant indices.
468  if (CI->isZero()) continue;
469 
470  // Handle a struct index, which adds its field offset to the pointer.
471  if (StructType *STy = GTI.getStructTypeOrNull()) {
472  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
473  } else {
474  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
475  Offset += Size*CI->getSExtValue();
476  }
477  } else {
478  // Found our variable index.
479  break;
480  }
481  }
482 
483  // If there are no variable indices, we must have a constant offset, just
484  // evaluate it the general way.
485  if (i == e) return nullptr;
486 
487  Value *VariableIdx = GEP->getOperand(i);
488  // Determine the scale factor of the variable element. For example, this is
489  // 4 if the variable index is into an array of i32.
490  uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
491 
492  // Verify that there are no other variable indices. If so, emit the hard way.
493  for (++i, ++GTI; i != e; ++i, ++GTI) {
494  ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
495  if (!CI) return nullptr;
496 
497  // Compute the aggregate offset of constant indices.
498  if (CI->isZero()) continue;
499 
500  // Handle a struct index, which adds its field offset to the pointer.
501  if (StructType *STy = GTI.getStructTypeOrNull()) {
502  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
503  } else {
504  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
505  Offset += Size*CI->getSExtValue();
506  }
507  }
508 
509  // Okay, we know we have a single variable index, which must be a
510  // pointer/array/vector index. If there is no offset, life is simple, return
511  // the index.
512  Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
513  unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
514  if (Offset == 0) {
515  // Cast to intptrty in case a truncation occurs. If an extension is needed,
516  // we don't need to bother extending: the extension won't affect where the
517  // computation crosses zero.
518  if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
519  VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
520  }
521  return VariableIdx;
522  }
523 
524  // Otherwise, there is an index. The computation we will do will be modulo
525  // the pointer size, so get it.
526  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
527 
528  Offset &= PtrSizeMask;
529  VariableScale &= PtrSizeMask;
530 
531  // To do this transformation, any constant index must be a multiple of the
532  // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
533  // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
534  // multiple of the variable scale.
535  int64_t NewOffs = Offset / (int64_t)VariableScale;
536  if (Offset != NewOffs*(int64_t)VariableScale)
537  return nullptr;
538 
539  // Okay, we can do this evaluation. Start by converting the index to intptr.
540  if (VariableIdx->getType() != IntPtrTy)
541  VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
542  true /*Signed*/);
543  Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
544  return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
545 }
546 
547 /// Returns true if we can rewrite Start as a GEP with pointer Base
548 /// and some integer offset. The nodes that need to be re-written
549 /// for this transformation will be added to Explored.
550 static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
551  const DataLayout &DL,
552  SetVector<Value *> &Explored) {
553  SmallVector<Value *, 16> WorkList(1, Start);
554  Explored.insert(Base);
555 
556  // The following traversal gives us an order which can be used
557  // when doing the final transformation. Since in the final
558  // transformation we create the PHI replacement instructions first,
559  // we don't have to get them in any particular order.
560  //
561  // However, for other instructions we will have to traverse the
562  // operands of an instruction first, which means that we have to
563  // do a post-order traversal.
564  while (!WorkList.empty()) {
566 
567  while (!WorkList.empty()) {
568  if (Explored.size() >= 100)
569  return false;
570 
571  Value *V = WorkList.back();
572 
573  if (Explored.count(V) != 0) {
574  WorkList.pop_back();
575  continue;
576  }
577 
578  if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
579  !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
580  // We've found some value that we can't explore which is different from
581  // the base. Therefore we can't do this transformation.
582  return false;
583 
584  if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
585  auto *CI = dyn_cast<CastInst>(V);
586  if (!CI->isNoopCast(DL))
587  return false;
588 
589  if (Explored.count(CI->getOperand(0)) == 0)
590  WorkList.push_back(CI->getOperand(0));
591  }
592 
593  if (auto *GEP = dyn_cast<GEPOperator>(V)) {
594  // We're limiting the GEP to having one index. This will preserve
595  // the original pointer type. We could handle more cases in the
596  // future.
597  if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
598  GEP->getType() != Start->getType())
599  return false;
600 
601  if (Explored.count(GEP->getOperand(0)) == 0)
602  WorkList.push_back(GEP->getOperand(0));
603  }
604 
605  if (WorkList.back() == V) {
606  WorkList.pop_back();
607  // We've finished visiting this node, mark it as such.
608  Explored.insert(V);
609  }
610 
611  if (auto *PN = dyn_cast<PHINode>(V)) {
612  // We cannot transform PHIs on unsplittable basic blocks.
613  if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
614  return false;
615  Explored.insert(PN);
616  PHIs.insert(PN);
617  }
618  }
619 
620  // Explore the PHI nodes further.
621  for (auto *PN : PHIs)
622  for (Value *Op : PN->incoming_values())
623  if (Explored.count(Op) == 0)
624  WorkList.push_back(Op);
625  }
626 
627  // Make sure that we can do this. Since we can't insert GEPs in a basic
628  // block before a PHI node, we can't easily do this transformation if
629  // we have PHI node users of transformed instructions.
630  for (Value *Val : Explored) {
631  for (Value *Use : Val->uses()) {
632 
633  auto *PHI = dyn_cast<PHINode>(Use);
634  auto *Inst = dyn_cast<Instruction>(Val);
635 
636  if (Inst == Base || Inst == PHI || !Inst || !PHI ||
637  Explored.count(PHI) == 0)
638  continue;
639 
640  if (PHI->getParent() == Inst->getParent())
641  return false;
642  }
643  }
644  return true;
645 }
646 
647 // Sets the appropriate insert point on Builder where we can add
648 // a replacement Instruction for V (if that is possible).
649 static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
650  bool Before = true) {
651  if (auto *PHI = dyn_cast<PHINode>(V)) {
652  Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
653  return;
654  }
655  if (auto *I = dyn_cast<Instruction>(V)) {
656  if (!Before)
657  I = &*std::next(I->getIterator());
658  Builder.SetInsertPoint(I);
659  return;
660  }
661  if (auto *A = dyn_cast<Argument>(V)) {
662  // Set the insertion point in the entry block.
663  BasicBlock &Entry = A->getParent()->getEntryBlock();
664  Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
665  return;
666  }
667  // Otherwise, this is a constant and we don't need to set a new
668  // insertion point.
669  assert(isa<Constant>(V) && "Setting insertion point for unknown value!");
670 }
671 
672 /// Returns a re-written value of Start as an indexed GEP using Base as a
673 /// pointer.
675  const DataLayout &DL,
676  SetVector<Value *> &Explored) {
677  // Perform all the substitutions. This is a bit tricky because we can
678  // have cycles in our use-def chains.
679  // 1. Create the PHI nodes without any incoming values.
680  // 2. Create all the other values.
681  // 3. Add the edges for the PHI nodes.
682  // 4. Emit GEPs to get the original pointers.
683  // 5. Remove the original instructions.
684  Type *IndexType = IntegerType::get(
685  Base->getContext(), DL.getPointerTypeSizeInBits(Start->getType()));
686 
688  NewInsts[Base] = ConstantInt::getNullValue(IndexType);
689 
690  // Create the new PHI nodes, without adding any incoming values.
691  for (Value *Val : Explored) {
692  if (Val == Base)
693  continue;
694  // Create empty phi nodes. This avoids cyclic dependencies when creating
695  // the remaining instructions.
696  if (auto *PHI = dyn_cast<PHINode>(Val))
697  NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
698  PHI->getName() + ".idx", PHI);
699  }
700  IRBuilder<> Builder(Base->getContext());
701 
702  // Create all the other instructions.
703  for (Value *Val : Explored) {
704 
705  if (NewInsts.find(Val) != NewInsts.end())
706  continue;
707 
708  if (auto *CI = dyn_cast<CastInst>(Val)) {
709  NewInsts[CI] = NewInsts[CI->getOperand(0)];
710  continue;
711  }
712  if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
713  Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
714  : GEP->getOperand(1);
715  setInsertionPoint(Builder, GEP);
716  // Indices might need to be sign extended. GEPs will magically do
717  // this, but we need to do it ourselves here.
718  if (Index->getType()->getScalarSizeInBits() !=
719  NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
720  Index = Builder.CreateSExtOrTrunc(
721  Index, NewInsts[GEP->getOperand(0)]->getType(),
722  GEP->getOperand(0)->getName() + ".sext");
723  }
724 
725  auto *Op = NewInsts[GEP->getOperand(0)];
726  if (isa<ConstantInt>(Op) && dyn_cast<ConstantInt>(Op)->isZero())
727  NewInsts[GEP] = Index;
728  else
729  NewInsts[GEP] = Builder.CreateNSWAdd(
730  Op, Index, GEP->getOperand(0)->getName() + ".add");
731  continue;
732  }
733  if (isa<PHINode>(Val))
734  continue;
735 
736  llvm_unreachable("Unexpected instruction type");
737  }
738 
739  // Add the incoming values to the PHI nodes.
740  for (Value *Val : Explored) {
741  if (Val == Base)
742  continue;
743  // All the instructions have been created, we can now add edges to the
744  // phi nodes.
745  if (auto *PHI = dyn_cast<PHINode>(Val)) {
746  PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
747  for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
748  Value *NewIncoming = PHI->getIncomingValue(I);
749 
750  if (NewInsts.find(NewIncoming) != NewInsts.end())
751  NewIncoming = NewInsts[NewIncoming];
752 
753  NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
754  }
755  }
756  }
757 
758  for (Value *Val : Explored) {
759  if (Val == Base)
760  continue;
761 
762  // Depending on the type, for external users we have to emit
763  // a GEP or a GEP + ptrtoint.
764  setInsertionPoint(Builder, Val, false);
765 
766  // If required, create an inttoptr instruction for Base.
767  Value *NewBase = Base;
768  if (!Base->getType()->isPointerTy())
769  NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
770  Start->getName() + "to.ptr");
771 
772  Value *GEP = Builder.CreateInBoundsGEP(
773  Start->getType()->getPointerElementType(), NewBase,
774  makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
775 
776  if (!Val->getType()->isPointerTy()) {
777  Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
778  Val->getName() + ".conv");
779  GEP = Cast;
780  }
781  Val->replaceAllUsesWith(GEP);
782  }
783 
784  return NewInsts[Start];
785 }
786 
787 /// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
788 /// the input Value as a constant indexed GEP. Returns a pair containing
789 /// the GEPs Pointer and Index.
790 static std::pair<Value *, Value *>
792  Type *IndexType = IntegerType::get(V->getContext(),
794 
795  Constant *Index = ConstantInt::getNullValue(IndexType);
796  while (true) {
797  if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
798  // We accept only inbouds GEPs here to exclude the possibility of
799  // overflow.
800  if (!GEP->isInBounds())
801  break;
802  if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
803  GEP->getType() == V->getType()) {
804  V = GEP->getOperand(0);
805  Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
806  Index = ConstantExpr::getAdd(
807  Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
808  continue;
809  }
810  break;
811  }
812  if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
813  if (!CI->isNoopCast(DL))
814  break;
815  V = CI->getOperand(0);
816  continue;
817  }
818  if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
819  if (!CI->isNoopCast(DL))
820  break;
821  V = CI->getOperand(0);
822  continue;
823  }
824  break;
825  }
826  return {V, Index};
827 }
828 
829 /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
830 /// We can look through PHIs, GEPs and casts in order to determine a common base
831 /// between GEPLHS and RHS.
833  ICmpInst::Predicate Cond,
834  const DataLayout &DL) {
835  if (!GEPLHS->hasAllConstantIndices())
836  return nullptr;
837 
838  // Make sure the pointers have the same type.
839  if (GEPLHS->getType() != RHS->getType())
840  return nullptr;
841 
842  Value *PtrBase, *Index;
843  std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
844 
845  // The set of nodes that will take part in this transformation.
846  SetVector<Value *> Nodes;
847 
848  if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
849  return nullptr;
850 
851  // We know we can re-write this as
852  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
853  // Since we've only looked through inbouds GEPs we know that we
854  // can't have overflow on either side. We can therefore re-write
855  // this as:
856  // OFFSET1 cmp OFFSET2
857  Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
858 
859  // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
860  // GEP having PtrBase as the pointer base, and has returned in NewRHS the
861  // offset. Since Index is the offset of LHS to the base pointer, we will now
862  // compare the offsets instead of comparing the pointers.
863  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
864 }
865 
866 /// Fold comparisons between a GEP instruction and something else. At this point
867 /// we know that the GEP is on the LHS of the comparison.
868 Instruction *InstCombiner::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
869  ICmpInst::Predicate Cond,
870  Instruction &I) {
871  // Don't transform signed compares of GEPs into index compares. Even if the
872  // GEP is inbounds, the final add of the base pointer can have signed overflow
873  // and would change the result of the icmp.
874  // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
875  // the maximum signed value for the pointer type.
876  if (ICmpInst::isSigned(Cond))
877  return nullptr;
878 
879  // Look through bitcasts and addrspacecasts. We do not however want to remove
880  // 0 GEPs.
881  if (!isa<GetElementPtrInst>(RHS))
882  RHS = RHS->stripPointerCasts();
883 
884  Value *PtrBase = GEPLHS->getOperand(0);
885  if (PtrBase == RHS && GEPLHS->isInBounds()) {
886  // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
887  // This transformation (ignoring the base and scales) is valid because we
888  // know pointers can't overflow since the gep is inbounds. See if we can
889  // output an optimized form.
890  Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
891 
892  // If not, synthesize the offset the hard way.
893  if (!Offset)
894  Offset = EmitGEPOffset(GEPLHS);
895  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
896  Constant::getNullValue(Offset->getType()));
897  } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
898  // If the base pointers are different, but the indices are the same, just
899  // compare the base pointer.
900  if (PtrBase != GEPRHS->getOperand(0)) {
901  bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
902  IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
903  GEPRHS->getOperand(0)->getType();
904  if (IndicesTheSame)
905  for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
906  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
907  IndicesTheSame = false;
908  break;
909  }
910 
911  // If all indices are the same, just compare the base pointers.
912  if (IndicesTheSame)
913  return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
914 
915  // If we're comparing GEPs with two base pointers that only differ in type
916  // and both GEPs have only constant indices or just one use, then fold
917  // the compare with the adjusted indices.
918  if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
919  (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
920  (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
921  PtrBase->stripPointerCasts() ==
922  GEPRHS->getOperand(0)->stripPointerCasts()) {
923  Value *LOffset = EmitGEPOffset(GEPLHS);
924  Value *ROffset = EmitGEPOffset(GEPRHS);
925 
926  // If we looked through an addrspacecast between different sized address
927  // spaces, the LHS and RHS pointers are different sized
928  // integers. Truncate to the smaller one.
929  Type *LHSIndexTy = LOffset->getType();
930  Type *RHSIndexTy = ROffset->getType();
931  if (LHSIndexTy != RHSIndexTy) {
932  if (LHSIndexTy->getPrimitiveSizeInBits() <
933  RHSIndexTy->getPrimitiveSizeInBits()) {
934  ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
935  } else
936  LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
937  }
938 
939  Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
940  LOffset, ROffset);
941  return replaceInstUsesWith(I, Cmp);
942  }
943 
944  // Otherwise, the base pointers are different and the indices are
945  // different. Try convert this to an indexed compare by looking through
946  // PHIs/casts.
947  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
948  }
949 
950  // If one of the GEPs has all zero indices, recurse.
951  if (GEPLHS->hasAllZeroIndices())
952  return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
954 
955  // If the other GEP has all zero indices, recurse.
956  if (GEPRHS->hasAllZeroIndices())
957  return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
958 
959  bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
960  if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
961  // If the GEPs only differ by one index, compare it.
962  unsigned NumDifferences = 0; // Keep track of # differences.
963  unsigned DiffOperand = 0; // The operand that differs.
964  for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
965  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
966  if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
967  GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
968  // Irreconcilable differences.
969  NumDifferences = 2;
970  break;
971  } else {
972  if (NumDifferences++) break;
973  DiffOperand = i;
974  }
975  }
976 
977  if (NumDifferences == 0) // SAME GEP?
978  return replaceInstUsesWith(I, // No comparison is needed here.
979  Builder.getInt1(ICmpInst::isTrueWhenEqual(Cond)));
980 
981  else if (NumDifferences == 1 && GEPsInBounds) {
982  Value *LHSV = GEPLHS->getOperand(DiffOperand);
983  Value *RHSV = GEPRHS->getOperand(DiffOperand);
984  // Make sure we do a signed comparison here.
985  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
986  }
987  }
988 
989  // Only lower this if the icmp is the only user of the GEP or if we expect
990  // the result to fold to a constant!
991  if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
992  (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
993  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
994  Value *L = EmitGEPOffset(GEPLHS);
995  Value *R = EmitGEPOffset(GEPRHS);
996  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
997  }
998  }
999 
1000  // Try convert this to an indexed compare by looking through PHIs/casts as a
1001  // last resort.
1002  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1003 }
1004 
1005 Instruction *InstCombiner::foldAllocaCmp(ICmpInst &ICI,
1006  const AllocaInst *Alloca,
1007  const Value *Other) {
1008  assert(ICI.isEquality() && "Cannot fold non-equality comparison.");
1009 
1010  // It would be tempting to fold away comparisons between allocas and any
1011  // pointer not based on that alloca (e.g. an argument). However, even
1012  // though such pointers cannot alias, they can still compare equal.
1013  //
1014  // But LLVM doesn't specify where allocas get their memory, so if the alloca
1015  // doesn't escape we can argue that it's impossible to guess its value, and we
1016  // can therefore act as if any such guesses are wrong.
1017  //
1018  // The code below checks that the alloca doesn't escape, and that it's only
1019  // used in a comparison once (the current instruction). The
1020  // single-comparison-use condition ensures that we're trivially folding all
1021  // comparisons against the alloca consistently, and avoids the risk of
1022  // erroneously folding a comparison of the pointer with itself.
1023 
1024  unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1025 
1027  for (const Use &U : Alloca->uses()) {
1028  if (Worklist.size() >= MaxIter)
1029  return nullptr;
1030  Worklist.push_back(&U);
1031  }
1032 
1033  unsigned NumCmps = 0;
1034  while (!Worklist.empty()) {
1035  assert(Worklist.size() <= MaxIter);
1036  const Use *U = Worklist.pop_back_val();
1037  const Value *V = U->getUser();
1038  --MaxIter;
1039 
1040  if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1041  isa<SelectInst>(V)) {
1042  // Track the uses.
1043  } else if (isa<LoadInst>(V)) {
1044  // Loading from the pointer doesn't escape it.
1045  continue;
1046  } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1047  // Storing *to* the pointer is fine, but storing the pointer escapes it.
1048  if (SI->getValueOperand() == U->get())
1049  return nullptr;
1050  continue;
1051  } else if (isa<ICmpInst>(V)) {
1052  if (NumCmps++)
1053  return nullptr; // Found more than one cmp.
1054  continue;
1055  } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1056  switch (Intrin->getIntrinsicID()) {
1057  // These intrinsics don't escape or compare the pointer. Memset is safe
1058  // because we don't allow ptrtoint. Memcpy and memmove are safe because
1059  // we don't allow stores, so src cannot point to V.
1060  case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1061  case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1062  continue;
1063  default:
1064  return nullptr;
1065  }
1066  } else {
1067  return nullptr;
1068  }
1069  for (const Use &U : V->uses()) {
1070  if (Worklist.size() >= MaxIter)
1071  return nullptr;
1072  Worklist.push_back(&U);
1073  }
1074  }
1075 
1076  Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1077  return replaceInstUsesWith(
1078  ICI,
1080 }
1081 
1082 /// Fold "icmp pred (X+CI), X".
1083 Instruction *InstCombiner::foldICmpAddOpConst(Value *X, ConstantInt *CI,
1084  ICmpInst::Predicate Pred) {
1085  // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1086  // so the values can never be equal. Similarly for all other "or equals"
1087  // operators.
1088 
1089  // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1090  // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1091  // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1092  if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1093  Value *R =
1095  return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1096  }
1097 
1098  // (X+1) >u X --> X <u (0-1) --> X != 255
1099  // (X+2) >u X --> X <u (0-2) --> X <u 254
1100  // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1101  if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1102  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
1103 
1104  unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
1106  APInt::getSignedMaxValue(BitWidth));
1107 
1108  // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1109  // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1110  // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1111  // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1112  // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1113  // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1114  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1115  return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
1116 
1117  // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1118  // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1119  // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1120  // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1121  // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1122  // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1123 
1124  assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
1125  Constant *C = Builder.getInt(CI->getValue() - 1);
1126  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
1127 }
1128 
1129 /// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1130 /// (icmp eq/ne A, Log2(AP2/AP1)) ->
1131 /// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1132 Instruction *InstCombiner::foldICmpShrConstConst(ICmpInst &I, Value *A,
1133  const APInt &AP1,
1134  const APInt &AP2) {
1135  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1136 
1137  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1138  if (I.getPredicate() == I.ICMP_NE)
1139  Pred = CmpInst::getInversePredicate(Pred);
1140  return new ICmpInst(Pred, LHS, RHS);
1141  };
1142 
1143  // Don't bother doing any work for cases which InstSimplify handles.
1144  if (AP2.isNullValue())
1145  return nullptr;
1146 
1147  bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1148  if (IsAShr) {
1149  if (AP2.isAllOnesValue())
1150  return nullptr;
1151  if (AP2.isNegative() != AP1.isNegative())
1152  return nullptr;
1153  if (AP2.sgt(AP1))
1154  return nullptr;
1155  }
1156 
1157  if (!AP1)
1158  // 'A' must be large enough to shift out the highest set bit.
1159  return getICmp(I.ICMP_UGT, A,
1160  ConstantInt::get(A->getType(), AP2.logBase2()));
1161 
1162  if (AP1 == AP2)
1163  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1164 
1165  int Shift;
1166  if (IsAShr && AP1.isNegative())
1167  Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1168  else
1169  Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1170 
1171  if (Shift > 0) {
1172  if (IsAShr && AP1 == AP2.ashr(Shift)) {
1173  // There are multiple solutions if we are comparing against -1 and the LHS
1174  // of the ashr is not a power of two.
1175  if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1176  return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1177  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1178  } else if (AP1 == AP2.lshr(Shift)) {
1179  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1180  }
1181  }
1182 
1183  // Shifting const2 will never be equal to const1.
1184  // FIXME: This should always be handled by InstSimplify?
1185  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1186  return replaceInstUsesWith(I, TorF);
1187 }
1188 
1189 /// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1190 /// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1191 Instruction *InstCombiner::foldICmpShlConstConst(ICmpInst &I, Value *A,
1192  const APInt &AP1,
1193  const APInt &AP2) {
1194  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1195 
1196  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1197  if (I.getPredicate() == I.ICMP_NE)
1198  Pred = CmpInst::getInversePredicate(Pred);
1199  return new ICmpInst(Pred, LHS, RHS);
1200  };
1201 
1202  // Don't bother doing any work for cases which InstSimplify handles.
1203  if (AP2.isNullValue())
1204  return nullptr;
1205 
1206  unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1207 
1208  if (!AP1 && AP2TrailingZeros != 0)
1209  return getICmp(
1210  I.ICMP_UGE, A,
1211  ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1212 
1213  if (AP1 == AP2)
1214  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1215 
1216  // Get the distance between the lowest bits that are set.
1217  int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1218 
1219  if (Shift > 0 && AP2.shl(Shift) == AP1)
1220  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1221 
1222  // Shifting const2 will never be equal to const1.
1223  // FIXME: This should always be handled by InstSimplify?
1224  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1225  return replaceInstUsesWith(I, TorF);
1226 }
1227 
1228 /// The caller has matched a pattern of the form:
1229 /// I = icmp ugt (add (add A, B), CI2), CI1
1230 /// If this is of the form:
1231 /// sum = a + b
1232 /// if (sum+128 >u 255)
1233 /// Then replace it with llvm.sadd.with.overflow.i8.
1234 ///
1236  ConstantInt *CI2, ConstantInt *CI1,
1237  InstCombiner &IC) {
1238  // The transformation we're trying to do here is to transform this into an
1239  // llvm.sadd.with.overflow. To do this, we have to replace the original add
1240  // with a narrower add, and discard the add-with-constant that is part of the
1241  // range check (if we can't eliminate it, this isn't profitable).
1242 
1243  // In order to eliminate the add-with-constant, the compare can be its only
1244  // use.
1245  Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1246  if (!AddWithCst->hasOneUse())
1247  return nullptr;
1248 
1249  // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1250  if (!CI2->getValue().isPowerOf2())
1251  return nullptr;
1252  unsigned NewWidth = CI2->getValue().countTrailingZeros();
1253  if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1254  return nullptr;
1255 
1256  // The width of the new add formed is 1 more than the bias.
1257  ++NewWidth;
1258 
1259  // Check to see that CI1 is an all-ones value with NewWidth bits.
1260  if (CI1->getBitWidth() == NewWidth ||
1261  CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1262  return nullptr;
1263 
1264  // This is only really a signed overflow check if the inputs have been
1265  // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1266  // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1267  unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1268  if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1269  IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1270  return nullptr;
1271 
1272  // In order to replace the original add with a narrower
1273  // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1274  // and truncates that discard the high bits of the add. Verify that this is
1275  // the case.
1276  Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1277  for (User *U : OrigAdd->users()) {
1278  if (U == AddWithCst)
1279  continue;
1280 
1281  // Only accept truncates for now. We would really like a nice recursive
1282  // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1283  // chain to see which bits of a value are actually demanded. If the
1284  // original add had another add which was then immediately truncated, we
1285  // could still do the transformation.
1286  TruncInst *TI = dyn_cast<TruncInst>(U);
1287  if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1288  return nullptr;
1289  }
1290 
1291  // If the pattern matches, truncate the inputs to the narrower type and
1292  // use the sadd_with_overflow intrinsic to efficiently compute both the
1293  // result and the overflow bit.
1294  Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1296  Intrinsic::sadd_with_overflow, NewType);
1297 
1298  InstCombiner::BuilderTy &Builder = IC.Builder;
1299 
1300  // Put the new code above the original add, in case there are any uses of the
1301  // add between the add and the compare.
1302  Builder.SetInsertPoint(OrigAdd);
1303 
1304  Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
1305  Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
1306  CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
1307  Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
1308  Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
1309 
1310  // The inner add was the result of the narrow add, zero extended to the
1311  // wider type. Replace it with the result computed by the intrinsic.
1312  IC.replaceInstUsesWith(*OrigAdd, ZExt);
1313 
1314  // The original icmp gets replaced with the overflow value.
1315  return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1316 }
1317 
1318 // Handle (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1319 Instruction *InstCombiner::foldICmpWithZero(ICmpInst &Cmp) {
1320  CmpInst::Predicate Pred = Cmp.getPredicate();
1321  Value *X = Cmp.getOperand(0);
1322 
1323  if (match(Cmp.getOperand(1), m_Zero()) && Pred == ICmpInst::ICMP_SGT) {
1324  Value *A, *B;
1325  SelectPatternResult SPR = matchSelectPattern(X, A, B);
1326  if (SPR.Flavor == SPF_SMIN) {
1327  if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
1328  return new ICmpInst(Pred, B, Cmp.getOperand(1));
1329  if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
1330  return new ICmpInst(Pred, A, Cmp.getOperand(1));
1331  }
1332  }
1333  return nullptr;
1334 }
1335 
1336 // Fold icmp Pred X, C.
1337 Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
1338  CmpInst::Predicate Pred = Cmp.getPredicate();
1339  Value *X = Cmp.getOperand(0);
1340 
1341  const APInt *C;
1342  if (!match(Cmp.getOperand(1), m_APInt(C)))
1343  return nullptr;
1344 
1345  Value *A = nullptr, *B = nullptr;
1346 
1347  // Match the following pattern, which is a common idiom when writing
1348  // overflow-safe integer arithmetic functions. The source performs an addition
1349  // in wider type and explicitly checks for overflow using comparisons against
1350  // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1351  //
1352  // TODO: This could probably be generalized to handle other overflow-safe
1353  // operations if we worked out the formulas to compute the appropriate magic
1354  // constants.
1355  //
1356  // sum = a + b
1357  // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1358  {
1359  ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1360  if (Pred == ICmpInst::ICMP_UGT &&
1361  match(X, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1363  Cmp, A, B, CI2, cast<ConstantInt>(Cmp.getOperand(1)), *this))
1364  return Res;
1365  }
1366 
1367  // FIXME: Use m_APInt to allow folds for splat constants.
1368  ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
1369  if (!CI)
1370  return nullptr;
1371 
1372  // Canonicalize icmp instructions based on dominating conditions.
1373  BasicBlock *Parent = Cmp.getParent();
1374  BasicBlock *Dom = Parent->getSinglePredecessor();
1375  auto *BI = Dom ? dyn_cast<BranchInst>(Dom->getTerminator()) : nullptr;
1376  ICmpInst::Predicate Pred2;
1377  BasicBlock *TrueBB, *FalseBB;
1378  ConstantInt *CI2;
1379  if (BI && match(BI, m_Br(m_ICmp(Pred2, m_Specific(X), m_ConstantInt(CI2)),
1380  TrueBB, FalseBB)) &&
1381  TrueBB != FalseBB) {
1382  ConstantRange CR =
1384  ConstantRange DominatingCR =
1385  (Parent == TrueBB)
1388  CmpInst::getInversePredicate(Pred2), CI2->getValue());
1389  ConstantRange Intersection = DominatingCR.intersectWith(CR);
1390  ConstantRange Difference = DominatingCR.difference(CR);
1391  if (Intersection.isEmptySet())
1392  return replaceInstUsesWith(Cmp, Builder.getFalse());
1393  if (Difference.isEmptySet())
1394  return replaceInstUsesWith(Cmp, Builder.getTrue());
1395 
1396  // If this is a normal comparison, it demands all bits. If it is a sign
1397  // bit comparison, it only demands the sign bit.
1398  bool UnusedBit;
1399  bool IsSignBit = isSignBitCheck(Pred, CI->getValue(), UnusedBit);
1400 
1401  // Canonicalizing a sign bit comparison that gets used in a branch,
1402  // pessimizes codegen by generating branch on zero instruction instead
1403  // of a test and branch. So we avoid canonicalizing in such situations
1404  // because test and branch instruction has better branch displacement
1405  // than compare and branch instruction.
1406  if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
1407  return nullptr;
1408 
1409  if (auto *AI = Intersection.getSingleElement())
1410  return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*AI));
1411  if (auto *AD = Difference.getSingleElement())
1412  return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*AD));
1413  }
1414 
1415  return nullptr;
1416 }
1417 
1418 /// Fold icmp (trunc X, Y), C.
1419 Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
1420  TruncInst *Trunc,
1421  const APInt &C) {
1422  ICmpInst::Predicate Pred = Cmp.getPredicate();
1423  Value *X = Trunc->getOperand(0);
1424  if (C.isOneValue() && C.getBitWidth() > 1) {
1425  // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1426  Value *V = nullptr;
1427  if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1428  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1429  ConstantInt::get(V->getType(), 1));
1430  }
1431 
1432  if (Cmp.isEquality() && Trunc->hasOneUse()) {
1433  // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1434  // of the high bits truncated out of x are known.
1435  unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1436  SrcBits = X->getType()->getScalarSizeInBits();
1437  KnownBits Known = computeKnownBits(X, 0, &Cmp);
1438 
1439  // If all the high bits are known, we can do this xform.
1440  if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1441  // Pull in the high bits from known-ones set.
1442  APInt NewRHS = C.zext(SrcBits);
1443  NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1444  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1445  }
1446  }
1447 
1448  return nullptr;
1449 }
1450 
1451 /// Fold icmp (xor X, Y), C.
1452 Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp,
1453  BinaryOperator *Xor,
1454  const APInt &C) {
1455  Value *X = Xor->getOperand(0);
1456  Value *Y = Xor->getOperand(1);
1457  const APInt *XorC;
1458  if (!match(Y, m_APInt(XorC)))
1459  return nullptr;
1460 
1461  // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1462  // fold the xor.
1463  ICmpInst::Predicate Pred = Cmp.getPredicate();
1464  bool TrueIfSigned = false;
1465  if (isSignBitCheck(Cmp.getPredicate(), C, TrueIfSigned)) {
1466 
1467  // If the sign bit of the XorCst is not set, there is no change to
1468  // the operation, just stop using the Xor.
1469  if (!XorC->isNegative()) {
1470  Cmp.setOperand(0, X);
1471  Worklist.Add(Xor);
1472  return &Cmp;
1473  }
1474 
1475  // Emit the opposite comparison.
1476  if (TrueIfSigned)
1477  return new ICmpInst(ICmpInst::ICMP_SGT, X,
1479  else
1480  return new ICmpInst(ICmpInst::ICMP_SLT, X,
1482  }
1483 
1484  if (Xor->hasOneUse()) {
1485  // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1486  if (!Cmp.isEquality() && XorC->isSignMask()) {
1487  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1488  : Cmp.getSignedPredicate();
1489  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1490  }
1491 
1492  // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1493  if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1494  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1495  : Cmp.getSignedPredicate();
1496  Pred = Cmp.getSwappedPredicate(Pred);
1497  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), C ^ *XorC));
1498  }
1499  }
1500 
1501  // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1502  // iff -C is a power of 2
1503  if (Pred == ICmpInst::ICMP_UGT && *XorC == ~C && (C + 1).isPowerOf2())
1504  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1505 
1506  // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1507  // iff -C is a power of 2
1508  if (Pred == ICmpInst::ICMP_ULT && *XorC == -C && C.isPowerOf2())
1509  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
1510 
1511  return nullptr;
1512 }
1513 
1514 /// Fold icmp (and (sh X, Y), C2), C1.
1515 Instruction *InstCombiner::foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
1516  const APInt &C1, const APInt &C2) {
1517  BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1518  if (!Shift || !Shift->isShift())
1519  return nullptr;
1520 
1521  // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1522  // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1523  // code produced by the clang front-end, for bitfield access.
1524  // This seemingly simple opportunity to fold away a shift turns out to be
1525  // rather complicated. See PR17827 for details.
1526  unsigned ShiftOpcode = Shift->getOpcode();
1527  bool IsShl = ShiftOpcode == Instruction::Shl;
1528  const APInt *C3;
1529  if (match(Shift->getOperand(1), m_APInt(C3))) {
1530  bool CanFold = false;
1531  if (ShiftOpcode == Instruction::Shl) {
1532  // For a left shift, we can fold if the comparison is not signed. We can
1533  // also fold a signed comparison if the mask value and comparison value
1534  // are not negative. These constraints may not be obvious, but we can
1535  // prove that they are correct using an SMT solver.
1536  if (!Cmp.isSigned() || (!C2.isNegative() && !C1.isNegative()))
1537  CanFold = true;
1538  } else {
1539  bool IsAshr = ShiftOpcode == Instruction::AShr;
1540  // For a logical right shift, we can fold if the comparison is not signed.
1541  // We can also fold a signed comparison if the shifted mask value and the
1542  // shifted comparison value are not negative. These constraints may not be
1543  // obvious, but we can prove that they are correct using an SMT solver.
1544  // For an arithmetic shift right we can do the same, if we ensure
1545  // the And doesn't use any bits being shifted in. Normally these would
1546  // be turned into lshr by SimplifyDemandedBits, but not if there is an
1547  // additional user.
1548  if (!IsAshr || (C2.shl(*C3).lshr(*C3) == C2)) {
1549  if (!Cmp.isSigned() ||
1550  (!C2.shl(*C3).isNegative() && !C1.shl(*C3).isNegative()))
1551  CanFold = true;
1552  }
1553  }
1554 
1555  if (CanFold) {
1556  APInt NewCst = IsShl ? C1.lshr(*C3) : C1.shl(*C3);
1557  APInt SameAsC1 = IsShl ? NewCst.shl(*C3) : NewCst.lshr(*C3);
1558  // Check to see if we are shifting out any of the bits being compared.
1559  if (SameAsC1 != C1) {
1560  // If we shifted bits out, the fold is not going to work out. As a
1561  // special case, check to see if this means that the result is always
1562  // true or false now.
1563  if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1564  return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1565  if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1566  return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1567  } else {
1568  Cmp.setOperand(1, ConstantInt::get(And->getType(), NewCst));
1569  APInt NewAndCst = IsShl ? C2.lshr(*C3) : C2.shl(*C3);
1570  And->setOperand(1, ConstantInt::get(And->getType(), NewAndCst));
1571  And->setOperand(0, Shift->getOperand(0));
1572  Worklist.Add(Shift); // Shift is dead.
1573  return &Cmp;
1574  }
1575  }
1576  }
1577 
1578  // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1579  // preferable because it allows the C2 << Y expression to be hoisted out of a
1580  // loop if Y is invariant and X is not.
1581  if (Shift->hasOneUse() && C1.isNullValue() && Cmp.isEquality() &&
1582  !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1583  // Compute C2 << Y.
1584  Value *NewShift =
1585  IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
1586  : Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
1587 
1588  // Compute X & (C2 << Y).
1589  Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
1590  Cmp.setOperand(0, NewAnd);
1591  return &Cmp;
1592  }
1593 
1594  return nullptr;
1595 }
1596 
1597 /// Fold icmp (and X, C2), C1.
1598 Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
1599  BinaryOperator *And,
1600  const APInt &C1) {
1601  const APInt *C2;
1602  if (!match(And->getOperand(1), m_APInt(C2)))
1603  return nullptr;
1604 
1605  if (!And->hasOneUse())
1606  return nullptr;
1607 
1608  // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1609  // the input width without changing the value produced, eliminate the cast:
1610  //
1611  // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1612  //
1613  // We can do this transformation if the constants do not have their sign bits
1614  // set or if it is an equality comparison. Extending a relational comparison
1615  // when we're checking the sign bit would not work.
1616  Value *W;
1617  if (match(And->getOperand(0), m_OneUse(m_Trunc(m_Value(W)))) &&
1618  (Cmp.isEquality() || (!C1.isNegative() && !C2->isNegative()))) {
1619  // TODO: Is this a good transform for vectors? Wider types may reduce
1620  // throughput. Should this transform be limited (even for scalars) by using
1621  // shouldChangeType()?
1622  if (!Cmp.getType()->isVectorTy()) {
1623  Type *WideType = W->getType();
1624  unsigned WideScalarBits = WideType->getScalarSizeInBits();
1625  Constant *ZextC1 = ConstantInt::get(WideType, C1.zext(WideScalarBits));
1626  Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1627  Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
1628  return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1629  }
1630  }
1631 
1632  if (Instruction *I = foldICmpAndShift(Cmp, And, C1, *C2))
1633  return I;
1634 
1635  // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1636  // (icmp pred (and A, (or (shl 1, B), 1), 0))
1637  //
1638  // iff pred isn't signed
1639  if (!Cmp.isSigned() && C1.isNullValue() && And->getOperand(0)->hasOneUse() &&
1640  match(And->getOperand(1), m_One())) {
1641  Constant *One = cast<Constant>(And->getOperand(1));
1642  Value *Or = And->getOperand(0);
1643  Value *A, *B, *LShr;
1644  if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1645  match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1646  unsigned UsesRemoved = 0;
1647  if (And->hasOneUse())
1648  ++UsesRemoved;
1649  if (Or->hasOneUse())
1650  ++UsesRemoved;
1651  if (LShr->hasOneUse())
1652  ++UsesRemoved;
1653 
1654  // Compute A & ((1 << B) | 1)
1655  Value *NewOr = nullptr;
1656  if (auto *C = dyn_cast<Constant>(B)) {
1657  if (UsesRemoved >= 1)
1658  NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1659  } else {
1660  if (UsesRemoved >= 3)
1661  NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
1662  /*HasNUW=*/true),
1663  One, Or->getName());
1664  }
1665  if (NewOr) {
1666  Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
1667  Cmp.setOperand(0, NewAnd);
1668  return &Cmp;
1669  }
1670  }
1671  }
1672 
1673  return nullptr;
1674 }
1675 
1676 /// Fold icmp (and X, Y), C.
1677 Instruction *InstCombiner::foldICmpAndConstant(ICmpInst &Cmp,
1678  BinaryOperator *And,
1679  const APInt &C) {
1680  if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1681  return I;
1682 
1683  // TODO: These all require that Y is constant too, so refactor with the above.
1684 
1685  // Try to optimize things like "A[i] & 42 == 0" to index computations.
1686  Value *X = And->getOperand(0);
1687  Value *Y = And->getOperand(1);
1688  if (auto *LI = dyn_cast<LoadInst>(X))
1689  if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1690  if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1691  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1692  !LI->isVolatile() && isa<ConstantInt>(Y)) {
1693  ConstantInt *C2 = cast<ConstantInt>(Y);
1694  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1695  return Res;
1696  }
1697 
1698  if (!Cmp.isEquality())
1699  return nullptr;
1700 
1701  // X & -C == -C -> X > u ~C
1702  // X & -C != -C -> X <= u ~C
1703  // iff C is a power of 2
1704  if (Cmp.getOperand(1) == Y && (-C).isPowerOf2()) {
1705  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
1707  return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1708  }
1709 
1710  // (X & C2) == 0 -> (trunc X) >= 0
1711  // (X & C2) != 0 -> (trunc X) < 0
1712  // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1713  const APInt *C2;
1714  if (And->hasOneUse() && C.isNullValue() && match(Y, m_APInt(C2))) {
1715  int32_t ExactLogBase2 = C2->exactLogBase2();
1716  if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1717  Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1718  if (And->getType()->isVectorTy())
1719  NTy = VectorType::get(NTy, And->getType()->getVectorNumElements());
1720  Value *Trunc = Builder.CreateTrunc(X, NTy);
1721  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
1723  return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1724  }
1725  }
1726 
1727  return nullptr;
1728 }
1729 
1730 /// Fold icmp (or X, Y), C.
1731 Instruction *InstCombiner::foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
1732  const APInt &C) {
1733  ICmpInst::Predicate Pred = Cmp.getPredicate();
1734  if (C.isOneValue()) {
1735  // icmp slt signum(V) 1 --> icmp slt V, 1
1736  Value *V = nullptr;
1737  if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1738  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1739  ConstantInt::get(V->getType(), 1));
1740  }
1741 
1742  // X | C == C --> X <=u C
1743  // X | C != C --> X >u C
1744  // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1745  if (Cmp.isEquality() && Cmp.getOperand(1) == Or->getOperand(1) &&
1746  (C + 1).isPowerOf2()) {
1748  return new ICmpInst(Pred, Or->getOperand(0), Or->getOperand(1));
1749  }
1750 
1751  if (!Cmp.isEquality() || !C.isNullValue() || !Or->hasOneUse())
1752  return nullptr;
1753 
1754  Value *P, *Q;
1755  if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1756  // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1757  // -> and (icmp eq P, null), (icmp eq Q, null).
1758  Value *CmpP =
1759  Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1760  Value *CmpQ =
1761  Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1762  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1763  return BinaryOperator::Create(BOpc, CmpP, CmpQ);
1764  }
1765 
1766  // Are we using xors to bitwise check for a pair of (in)equalities? Convert to
1767  // a shorter form that has more potential to be folded even further.
1768  Value *X1, *X2, *X3, *X4;
1769  if (match(Or->getOperand(0), m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
1770  match(Or->getOperand(1), m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
1771  // ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
1772  // ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
1773  Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
1774  Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
1775  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1776  return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
1777  }
1778 
1779  return nullptr;
1780 }
1781 
1782 /// Fold icmp (mul X, Y), C.
1783 Instruction *InstCombiner::foldICmpMulConstant(ICmpInst &Cmp,
1784  BinaryOperator *Mul,
1785  const APInt &C) {
1786  const APInt *MulC;
1787  if (!match(Mul->getOperand(1), m_APInt(MulC)))
1788  return nullptr;
1789 
1790  // If this is a test of the sign bit and the multiply is sign-preserving with
1791  // a constant operand, use the multiply LHS operand instead.
1792  ICmpInst::Predicate Pred = Cmp.getPredicate();
1793  if (isSignTest(Pred, C) && Mul->hasNoSignedWrap()) {
1794  if (MulC->isNegative())
1795  Pred = ICmpInst::getSwappedPredicate(Pred);
1796  return new ICmpInst(Pred, Mul->getOperand(0),
1798  }
1799 
1800  return nullptr;
1801 }
1802 
1803 /// Fold icmp (shl 1, Y), C.
1805  const APInt &C) {
1806  Value *Y;
1807  if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
1808  return nullptr;
1809 
1810  Type *ShiftType = Shl->getType();
1811  unsigned TypeBits = C.getBitWidth();
1812  bool CIsPowerOf2 = C.isPowerOf2();
1813  ICmpInst::Predicate Pred = Cmp.getPredicate();
1814  if (Cmp.isUnsigned()) {
1815  // (1 << Y) pred C -> Y pred Log2(C)
1816  if (!CIsPowerOf2) {
1817  // (1 << Y) < 30 -> Y <= 4
1818  // (1 << Y) <= 30 -> Y <= 4
1819  // (1 << Y) >= 30 -> Y > 4
1820  // (1 << Y) > 30 -> Y > 4
1821  if (Pred == ICmpInst::ICMP_ULT)
1822  Pred = ICmpInst::ICMP_ULE;
1823  else if (Pred == ICmpInst::ICMP_UGE)
1824  Pred = ICmpInst::ICMP_UGT;
1825  }
1826 
1827  // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
1828  // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
1829  unsigned CLog2 = C.logBase2();
1830  if (CLog2 == TypeBits - 1) {
1831  if (Pred == ICmpInst::ICMP_UGE)
1832  Pred = ICmpInst::ICMP_EQ;
1833  else if (Pred == ICmpInst::ICMP_ULT)
1834  Pred = ICmpInst::ICMP_NE;
1835  }
1836  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
1837  } else if (Cmp.isSigned()) {
1838  Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
1839  if (C.isAllOnesValue()) {
1840  // (1 << Y) <= -1 -> Y == 31
1841  if (Pred == ICmpInst::ICMP_SLE)
1842  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1843 
1844  // (1 << Y) > -1 -> Y != 31
1845  if (Pred == ICmpInst::ICMP_SGT)
1846  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1847  } else if (!C) {
1848  // (1 << Y) < 0 -> Y == 31
1849  // (1 << Y) <= 0 -> Y == 31
1850  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1851  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1852 
1853  // (1 << Y) >= 0 -> Y != 31
1854  // (1 << Y) > 0 -> Y != 31
1855  if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1856  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1857  }
1858  } else if (Cmp.isEquality() && CIsPowerOf2) {
1859  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C.logBase2()));
1860  }
1861 
1862  return nullptr;
1863 }
1864 
1865 /// Fold icmp (shl X, Y), C.
1866 Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp,
1867  BinaryOperator *Shl,
1868  const APInt &C) {
1869  const APInt *ShiftVal;
1870  if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
1871  return foldICmpShlConstConst(Cmp, Shl->getOperand(1), C, *ShiftVal);
1872 
1873  const APInt *ShiftAmt;
1874  if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
1875  return foldICmpShlOne(Cmp, Shl, C);
1876 
1877  // Check that the shift amount is in range. If not, don't perform undefined
1878  // shifts. When the shift is visited, it will be simplified.
1879  unsigned TypeBits = C.getBitWidth();
1880  if (ShiftAmt->uge(TypeBits))
1881  return nullptr;
1882 
1883  ICmpInst::Predicate Pred = Cmp.getPredicate();
1884  Value *X = Shl->getOperand(0);
1885  Type *ShType = Shl->getType();
1886 
1887  // NSW guarantees that we are only shifting out sign bits from the high bits,
1888  // so we can ASHR the compare constant without needing a mask and eliminate
1889  // the shift.
1890  if (Shl->hasNoSignedWrap()) {
1891  if (Pred == ICmpInst::ICMP_SGT) {
1892  // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
1893  APInt ShiftedC = C.ashr(*ShiftAmt);
1894  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1895  }
1896  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1897  // This is the same code as the SGT case, but assert the pre-condition
1898  // that is needed for this to work with equality predicates.
1899  assert(C.ashr(*ShiftAmt).shl(*ShiftAmt) == C &&
1900  "Compare known true or false was not folded");
1901  APInt ShiftedC = C.ashr(*ShiftAmt);
1902  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1903  }
1904  if (Pred == ICmpInst::ICMP_SLT) {
1905  // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
1906  // (X << S) <=s C is equiv to X <=s (C >> S) for all C
1907  // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
1908  // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
1909  assert(!C.isMinSignedValue() && "Unexpected icmp slt");
1910  APInt ShiftedC = (C - 1).ashr(*ShiftAmt) + 1;
1911  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1912  }
1913  // If this is a signed comparison to 0 and the shift is sign preserving,
1914  // use the shift LHS operand instead; isSignTest may change 'Pred', so only
1915  // do that if we're sure to not continue on in this function.
1916  if (isSignTest(Pred, C))
1917  return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
1918  }
1919 
1920  // NUW guarantees that we are only shifting out zero bits from the high bits,
1921  // so we can LSHR the compare constant without needing a mask and eliminate
1922  // the shift.
1923  if (Shl->hasNoUnsignedWrap()) {
1924  if (Pred == ICmpInst::ICMP_UGT) {
1925  // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
1926  APInt ShiftedC = C.lshr(*ShiftAmt);
1927  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1928  }
1929  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1930  // This is the same code as the UGT case, but assert the pre-condition
1931  // that is needed for this to work with equality predicates.
1932  assert(C.lshr(*ShiftAmt).shl(*ShiftAmt) == C &&
1933  "Compare known true or false was not folded");
1934  APInt ShiftedC = C.lshr(*ShiftAmt);
1935  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1936  }
1937  if (Pred == ICmpInst::ICMP_ULT) {
1938  // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
1939  // (X << S) <=u C is equiv to X <=u (C >> S) for all C
1940  // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
1941  // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
1942  assert(C.ugt(0) && "ult 0 should have been eliminated");
1943  APInt ShiftedC = (C - 1).lshr(*ShiftAmt) + 1;
1944  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1945  }
1946  }
1947 
1948  if (Cmp.isEquality() && Shl->hasOneUse()) {
1949  // Strength-reduce the shift into an 'and'.
1951  ShType,
1952  APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
1953  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1954  Constant *LShrC = ConstantInt::get(ShType, C.lshr(*ShiftAmt));
1955  return new ICmpInst(Pred, And, LShrC);
1956  }
1957 
1958  // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
1959  bool TrueIfSigned = false;
1960  if (Shl->hasOneUse() && isSignBitCheck(Pred, C, TrueIfSigned)) {
1961  // (X << 31) <s 0 --> (X & 1) != 0
1963  ShType,
1964  APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
1965  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
1966  return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
1967  And, Constant::getNullValue(ShType));
1968  }
1969 
1970  // Transform (icmp pred iM (shl iM %v, N), C)
1971  // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
1972  // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
1973  // This enables us to get rid of the shift in favor of a trunc that may be
1974  // free on the target. It has the additional benefit of comparing to a
1975  // smaller constant that may be more target-friendly.
1976  unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
1977  if (Shl->hasOneUse() && Amt != 0 && C.countTrailingZeros() >= Amt &&
1978  DL.isLegalInteger(TypeBits - Amt)) {
1979  Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
1980  if (ShType->isVectorTy())
1981  TruncTy = VectorType::get(TruncTy, ShType->getVectorNumElements());
1982  Constant *NewC =
1983  ConstantInt::get(TruncTy, C.ashr(*ShiftAmt).trunc(TypeBits - Amt));
1984  return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
1985  }
1986 
1987  return nullptr;
1988 }
1989 
1990 /// Fold icmp ({al}shr X, Y), C.
1991 Instruction *InstCombiner::foldICmpShrConstant(ICmpInst &Cmp,
1992  BinaryOperator *Shr,
1993  const APInt &C) {
1994  // An exact shr only shifts out zero bits, so:
1995  // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
1996  Value *X = Shr->getOperand(0);
1997  CmpInst::Predicate Pred = Cmp.getPredicate();
1998  if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
1999  C.isNullValue())
2000  return new ICmpInst(Pred, X, Cmp.getOperand(1));
2001 
2002  const APInt *ShiftVal;
2003  if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
2004  return foldICmpShrConstConst(Cmp, Shr->getOperand(1), C, *ShiftVal);
2005 
2006  const APInt *ShiftAmt;
2007  if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2008  return nullptr;
2009 
2010  // Check that the shift amount is in range. If not, don't perform undefined
2011  // shifts. When the shift is visited it will be simplified.
2012  unsigned TypeBits = C.getBitWidth();
2013  unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2014  if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2015  return nullptr;
2016 
2017  bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2018  bool IsExact = Shr->isExact();
2019  Type *ShrTy = Shr->getType();
2020  // TODO: If we could guarantee that InstSimplify would handle all of the
2021  // constant-value-based preconditions in the folds below, then we could assert
2022  // those conditions rather than checking them. This is difficult because of
2023  // undef/poison (PR34838).
2024  if (IsAShr) {
2025  if (Pred == CmpInst::ICMP_SLT || (Pred == CmpInst::ICMP_SGT && IsExact)) {
2026  // icmp slt (ashr X, ShAmtC), C --> icmp slt X, (C << ShAmtC)
2027  // icmp sgt (ashr exact X, ShAmtC), C --> icmp sgt X, (C << ShAmtC)
2028  APInt ShiftedC = C.shl(ShAmtVal);
2029  if (ShiftedC.ashr(ShAmtVal) == C)
2030  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2031  }
2032  if (Pred == CmpInst::ICMP_SGT) {
2033  // icmp sgt (ashr X, ShAmtC), C --> icmp sgt X, ((C + 1) << ShAmtC) - 1
2034  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2035  if (!C.isMaxSignedValue() && !(C + 1).shl(ShAmtVal).isMinSignedValue() &&
2036  (ShiftedC + 1).ashr(ShAmtVal) == (C + 1))
2037  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2038  }
2039  } else {
2040  if (Pred == CmpInst::ICMP_ULT || (Pred == CmpInst::ICMP_UGT && IsExact)) {
2041  // icmp ult (lshr X, ShAmtC), C --> icmp ult X, (C << ShAmtC)
2042  // icmp ugt (lshr exact X, ShAmtC), C --> icmp ugt X, (C << ShAmtC)
2043  APInt ShiftedC = C.shl(ShAmtVal);
2044  if (ShiftedC.lshr(ShAmtVal) == C)
2045  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2046  }
2047  if (Pred == CmpInst::ICMP_UGT) {
2048  // icmp ugt (lshr X, ShAmtC), C --> icmp ugt X, ((C + 1) << ShAmtC) - 1
2049  APInt ShiftedC = (C + 1).shl(ShAmtVal) - 1;
2050  if ((ShiftedC + 1).lshr(ShAmtVal) == (C + 1))
2051  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, ShiftedC));
2052  }
2053  }
2054 
2055  if (!Cmp.isEquality())
2056  return nullptr;
2057 
2058  // Handle equality comparisons of shift-by-constant.
2059 
2060  // If the comparison constant changes with the shift, the comparison cannot
2061  // succeed (bits of the comparison constant cannot match the shifted value).
2062  // This should be known by InstSimplify and already be folded to true/false.
2063  assert(((IsAShr && C.shl(ShAmtVal).ashr(ShAmtVal) == C) ||
2064  (!IsAShr && C.shl(ShAmtVal).lshr(ShAmtVal) == C)) &&
2065  "Expected icmp+shr simplify did not occur.");
2066 
2067  // If the bits shifted out are known zero, compare the unshifted value:
2068  // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2069  if (Shr->isExact())
2070  return new ICmpInst(Pred, X, ConstantInt::get(ShrTy, C << ShAmtVal));
2071 
2072  if (Shr->hasOneUse()) {
2073  // Canonicalize the shift into an 'and':
2074  // icmp eq/ne (shr X, ShAmt), C --> icmp eq/ne (and X, HiMask), (C << ShAmt)
2075  APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2076  Constant *Mask = ConstantInt::get(ShrTy, Val);
2077  Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
2078  return new ICmpInst(Pred, And, ConstantInt::get(ShrTy, C << ShAmtVal));
2079  }
2080 
2081  return nullptr;
2082 }
2083 
2084 /// Fold icmp (udiv X, Y), C.
2085 Instruction *InstCombiner::foldICmpUDivConstant(ICmpInst &Cmp,
2086  BinaryOperator *UDiv,
2087  const APInt &C) {
2088  const APInt *C2;
2089  if (!match(UDiv->getOperand(0), m_APInt(C2)))
2090  return nullptr;
2091 
2092  assert(*C2 != 0 && "udiv 0, X should have been simplified already.");
2093 
2094  // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2095  Value *Y = UDiv->getOperand(1);
2096  if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2097  assert(!C.isMaxValue() &&
2098  "icmp ugt X, UINT_MAX should have been simplified already.");
2099  return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2100  ConstantInt::get(Y->getType(), C2->udiv(C + 1)));
2101  }
2102 
2103  // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2104  if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2105  assert(C != 0 && "icmp ult X, 0 should have been simplified already.");
2106  return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2107  ConstantInt::get(Y->getType(), C2->udiv(C)));
2108  }
2109 
2110  return nullptr;
2111 }
2112 
2113 /// Fold icmp ({su}div X, Y), C.
2114 Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
2115  BinaryOperator *Div,
2116  const APInt &C) {
2117  // Fold: icmp pred ([us]div X, C2), C -> range test
2118  // Fold this div into the comparison, producing a range check.
2119  // Determine, based on the divide type, what the range is being
2120  // checked. If there is an overflow on the low or high side, remember
2121  // it, otherwise compute the range [low, hi) bounding the new value.
2122  // See: InsertRangeTest above for the kinds of replacements possible.
2123  const APInt *C2;
2124  if (!match(Div->getOperand(1), m_APInt(C2)))
2125  return nullptr;
2126 
2127  // FIXME: If the operand types don't match the type of the divide
2128  // then don't attempt this transform. The code below doesn't have the
2129  // logic to deal with a signed divide and an unsigned compare (and
2130  // vice versa). This is because (x /s C2) <s C produces different
2131  // results than (x /s C2) <u C or (x /u C2) <s C or even
2132  // (x /u C2) <u C. Simply casting the operands and result won't
2133  // work. :( The if statement below tests that condition and bails
2134  // if it finds it.
2135  bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2136  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2137  return nullptr;
2138 
2139  // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2140  // INT_MIN will also fail if the divisor is 1. Although folds of all these
2141  // division-by-constant cases should be present, we can not assert that they
2142  // have happened before we reach this icmp instruction.
2143  if (C2->isNullValue() || C2->isOneValue() ||
2144  (DivIsSigned && C2->isAllOnesValue()))
2145  return nullptr;
2146 
2147  // Compute Prod = C * C2. We are essentially solving an equation of
2148  // form X / C2 = C. We solve for X by multiplying C2 and C.
2149  // By solving for X, we can turn this into a range check instead of computing
2150  // a divide.
2151  APInt Prod = C * *C2;
2152 
2153  // Determine if the product overflows by seeing if the product is not equal to
2154  // the divide. Make sure we do the same kind of divide as in the LHS
2155  // instruction that we're folding.
2156  bool ProdOV = (DivIsSigned ? Prod.sdiv(*C2) : Prod.udiv(*C2)) != C;
2157 
2158  ICmpInst::Predicate Pred = Cmp.getPredicate();
2159 
2160  // If the division is known to be exact, then there is no remainder from the
2161  // divide, so the covered range size is unit, otherwise it is the divisor.
2162  APInt RangeSize = Div->isExact() ? APInt(C2->getBitWidth(), 1) : *C2;
2163 
2164  // Figure out the interval that is being checked. For example, a comparison
2165  // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2166  // Compute this interval based on the constants involved and the signedness of
2167  // the compare/divide. This computes a half-open interval, keeping track of
2168  // whether either value in the interval overflows. After analysis each
2169  // overflow variable is set to 0 if it's corresponding bound variable is valid
2170  // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2171  int LoOverflow = 0, HiOverflow = 0;
2172  APInt LoBound, HiBound;
2173 
2174  if (!DivIsSigned) { // udiv
2175  // e.g. X/5 op 3 --> [15, 20)
2176  LoBound = Prod;
2177  HiOverflow = LoOverflow = ProdOV;
2178  if (!HiOverflow) {
2179  // If this is not an exact divide, then many values in the range collapse
2180  // to the same result value.
2181  HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2182  }
2183  } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
2184  if (C.isNullValue()) { // (X / pos) op 0
2185  // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2186  LoBound = -(RangeSize - 1);
2187  HiBound = RangeSize;
2188  } else if (C.isStrictlyPositive()) { // (X / pos) op pos
2189  LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2190  HiOverflow = LoOverflow = ProdOV;
2191  if (!HiOverflow)
2192  HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2193  } else { // (X / pos) op neg
2194  // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2195  HiBound = Prod + 1;
2196  LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2197  if (!LoOverflow) {
2198  APInt DivNeg = -RangeSize;
2199  LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2200  }
2201  }
2202  } else if (C2->isNegative()) { // Divisor is < 0.
2203  if (Div->isExact())
2204  RangeSize.negate();
2205  if (C.isNullValue()) { // (X / neg) op 0
2206  // e.g. X/-5 op 0 --> [-4, 5)
2207  LoBound = RangeSize + 1;
2208  HiBound = -RangeSize;
2209  if (HiBound == *C2) { // -INTMIN = INTMIN
2210  HiOverflow = 1; // [INTMIN+1, overflow)
2211  HiBound = APInt(); // e.g. X/INTMIN = 0 --> X > INTMIN
2212  }
2213  } else if (C.isStrictlyPositive()) { // (X / neg) op pos
2214  // e.g. X/-5 op 3 --> [-19, -14)
2215  HiBound = Prod + 1;
2216  HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2217  if (!LoOverflow)
2218  LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2219  } else { // (X / neg) op neg
2220  LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2221  LoOverflow = HiOverflow = ProdOV;
2222  if (!HiOverflow)
2223  HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2224  }
2225 
2226  // Dividing by a negative swaps the condition. LT <-> GT
2227  Pred = ICmpInst::getSwappedPredicate(Pred);
2228  }
2229 
2230  Value *X = Div->getOperand(0);
2231  switch (Pred) {
2232  default: llvm_unreachable("Unhandled icmp opcode!");
2233  case ICmpInst::ICMP_EQ:
2234  if (LoOverflow && HiOverflow)
2235  return replaceInstUsesWith(Cmp, Builder.getFalse());
2236  if (HiOverflow)
2237  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2238  ICmpInst::ICMP_UGE, X,
2239  ConstantInt::get(Div->getType(), LoBound));
2240  if (LoOverflow)
2241  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2242  ICmpInst::ICMP_ULT, X,
2243  ConstantInt::get(Div->getType(), HiBound));
2244  return replaceInstUsesWith(
2245  Cmp, insertRangeTest(X, LoBound, HiBound, DivIsSigned, true));
2246  case ICmpInst::ICMP_NE:
2247  if (LoOverflow && HiOverflow)
2248  return replaceInstUsesWith(Cmp, Builder.getTrue());
2249  if (HiOverflow)
2250  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2251  ICmpInst::ICMP_ULT, X,
2252  ConstantInt::get(Div->getType(), LoBound));
2253  if (LoOverflow)
2254  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2255  ICmpInst::ICMP_UGE, X,
2256  ConstantInt::get(Div->getType(), HiBound));
2257  return replaceInstUsesWith(Cmp,
2258  insertRangeTest(X, LoBound, HiBound,
2259  DivIsSigned, false));
2260  case ICmpInst::ICMP_ULT:
2261  case ICmpInst::ICMP_SLT:
2262  if (LoOverflow == +1) // Low bound is greater than input range.
2263  return replaceInstUsesWith(Cmp, Builder.getTrue());
2264  if (LoOverflow == -1) // Low bound is less than input range.
2265  return replaceInstUsesWith(Cmp, Builder.getFalse());
2266  return new ICmpInst(Pred, X, ConstantInt::get(Div->getType(), LoBound));
2267  case ICmpInst::ICMP_UGT:
2268  case ICmpInst::ICMP_SGT:
2269  if (HiOverflow == +1) // High bound greater than input range.
2270  return replaceInstUsesWith(Cmp, Builder.getFalse());
2271  if (HiOverflow == -1) // High bound less than input range.
2272  return replaceInstUsesWith(Cmp, Builder.getTrue());
2273  if (Pred == ICmpInst::ICMP_UGT)
2274  return new ICmpInst(ICmpInst::ICMP_UGE, X,
2275  ConstantInt::get(Div->getType(), HiBound));
2276  return new ICmpInst(ICmpInst::ICMP_SGE, X,
2277  ConstantInt::get(Div->getType(), HiBound));
2278  }
2279 
2280  return nullptr;
2281 }
2282 
2283 /// Fold icmp (sub X, Y), C.
2284 Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
2285  BinaryOperator *Sub,
2286  const APInt &C) {
2287  Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2288  ICmpInst::Predicate Pred = Cmp.getPredicate();
2289 
2290  // The following transforms are only worth it if the only user of the subtract
2291  // is the icmp.
2292  if (!Sub->hasOneUse())
2293  return nullptr;
2294 
2295  if (Sub->hasNoSignedWrap()) {
2296  // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2297  if (Pred == ICmpInst::ICMP_SGT && C.isAllOnesValue())
2298  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2299 
2300  // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2301  if (Pred == ICmpInst::ICMP_SGT && C.isNullValue())
2302  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2303 
2304  // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2305  if (Pred == ICmpInst::ICMP_SLT && C.isNullValue())
2306  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2307 
2308  // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2309  if (Pred == ICmpInst::ICMP_SLT && C.isOneValue())
2310  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2311  }
2312 
2313  const APInt *C2;
2314  if (!match(X, m_APInt(C2)))
2315  return nullptr;
2316 
2317  // C2 - Y <u C -> (Y | (C - 1)) == C2
2318  // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2319  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() &&
2320  (*C2 & (C - 1)) == (C - 1))
2321  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, C - 1), X);
2322 
2323  // C2 - Y >u C -> (Y | C) != C2
2324  // iff C2 & C == C and C + 1 is a power of 2
2325  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == C)
2326  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, C), X);
2327 
2328  return nullptr;
2329 }
2330 
2331 /// Fold icmp (add X, Y), C.
2332 Instruction *InstCombiner::foldICmpAddConstant(ICmpInst &Cmp,
2334  const APInt &C) {
2335  Value *Y = Add->getOperand(1);
2336  const APInt *C2;
2337  if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2338  return nullptr;
2339 
2340  // Fold icmp pred (add X, C2), C.
2341  Value *X = Add->getOperand(0);
2342  Type *Ty = Add->getType();
2343  CmpInst::Predicate Pred = Cmp.getPredicate();
2344 
2345  // If the add does not wrap, we can always adjust the compare by subtracting
2346  // the constants. Equality comparisons are handled elsewhere. SGE/SLE are
2347  // canonicalized to SGT/SLT.
2348  if (Add->hasNoSignedWrap() &&
2349  (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) {
2350  bool Overflow;
2351  APInt NewC = C.ssub_ov(*C2, Overflow);
2352  // If there is overflow, the result must be true or false.
2353  // TODO: Can we assert there is no overflow because InstSimplify always
2354  // handles those cases?
2355  if (!Overflow)
2356  // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2357  return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2358  }
2359 
2360  auto CR = ConstantRange::makeExactICmpRegion(Pred, C).subtract(*C2);
2361  const APInt &Upper = CR.getUpper();
2362  const APInt &Lower = CR.getLower();
2363  if (Cmp.isSigned()) {
2364  if (Lower.isSignMask())
2365  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2366  if (Upper.isSignMask())
2367  return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2368  } else {
2369  if (Lower.isMinValue())
2370  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2371  if (Upper.isMinValue())
2372  return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2373  }
2374 
2375  if (!Add->hasOneUse())
2376  return nullptr;
2377 
2378  // X+C <u C2 -> (X & -C2) == C
2379  // iff C & (C2-1) == 0
2380  // C2 is a power of 2
2381  if (Pred == ICmpInst::ICMP_ULT && C.isPowerOf2() && (*C2 & (C - 1)) == 0)
2382  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
2383  ConstantExpr::getNeg(cast<Constant>(Y)));
2384 
2385  // X+C >u C2 -> (X & ~C2) != C
2386  // iff C & C2 == 0
2387  // C2+1 is a power of 2
2388  if (Pred == ICmpInst::ICMP_UGT && (C + 1).isPowerOf2() && (*C2 & C) == 0)
2389  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~C),
2390  ConstantExpr::getNeg(cast<Constant>(Y)));
2391 
2392  return nullptr;
2393 }
2394 
2395 bool InstCombiner::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
2396  Value *&RHS, ConstantInt *&Less,
2397  ConstantInt *&Equal,
2398  ConstantInt *&Greater) {
2399  // TODO: Generalize this to work with other comparison idioms or ensure
2400  // they get canonicalized into this form.
2401 
2402  // select i1 (a == b), i32 Equal, i32 (select i1 (a < b), i32 Less, i32
2403  // Greater), where Equal, Less and Greater are placeholders for any three
2404  // constants.
2405  ICmpInst::Predicate PredA, PredB;
2406  if (match(SI->getTrueValue(), m_ConstantInt(Equal)) &&
2407  match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) &&
2408  PredA == ICmpInst::ICMP_EQ &&
2409  match(SI->getFalseValue(),
2410  m_Select(m_ICmp(PredB, m_Specific(LHS), m_Specific(RHS)),
2411  m_ConstantInt(Less), m_ConstantInt(Greater))) &&
2412  PredB == ICmpInst::ICMP_SLT) {
2413  return true;
2414  }
2415  return false;
2416 }
2417 
2418 Instruction *InstCombiner::foldICmpSelectConstant(ICmpInst &Cmp,
2419  SelectInst *Select,
2420  ConstantInt *C) {
2421 
2422  assert(C && "Cmp RHS should be a constant int!");
2423  // If we're testing a constant value against the result of a three way
2424  // comparison, the result can be expressed directly in terms of the
2425  // original values being compared. Note: We could possibly be more
2426  // aggressive here and remove the hasOneUse test. The original select is
2427  // really likely to simplify or sink when we remove a test of the result.
2428  Value *OrigLHS, *OrigRHS;
2429  ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
2430  if (Cmp.hasOneUse() &&
2431  matchThreeWayIntCompare(Select, OrigLHS, OrigRHS, C1LessThan, C2Equal,
2432  C3GreaterThan)) {
2433  assert(C1LessThan && C2Equal && C3GreaterThan);
2434 
2435  bool TrueWhenLessThan =
2436  ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
2437  ->isAllOnesValue();
2438  bool TrueWhenEqual =
2439  ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
2440  ->isAllOnesValue();
2441  bool TrueWhenGreaterThan =
2442  ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
2443  ->isAllOnesValue();
2444 
2445  // This generates the new instruction that will replace the original Cmp
2446  // Instruction. Instead of enumerating the various combinations when
2447  // TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
2448  // false, we rely on chaining of ORs and future passes of InstCombine to
2449  // simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
2450 
2451  // When none of the three constants satisfy the predicate for the RHS (C),
2452  // the entire original Cmp can be simplified to a false.
2453  Value *Cond = Builder.getFalse();
2454  if (TrueWhenLessThan)
2455  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT, OrigLHS, OrigRHS));
2456  if (TrueWhenEqual)
2457  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ, OrigLHS, OrigRHS));
2458  if (TrueWhenGreaterThan)
2459  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT, OrigLHS, OrigRHS));
2460 
2461  return replaceInstUsesWith(Cmp, Cond);
2462  }
2463  return nullptr;
2464 }
2465 
2466 /// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2467 /// where X is some kind of instruction.
2468 Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2469  const APInt *C;
2470  if (!match(Cmp.getOperand(1), m_APInt(C)))
2471  return nullptr;
2472 
2473  if (auto *BO = dyn_cast<BinaryOperator>(Cmp.getOperand(0))) {
2474  switch (BO->getOpcode()) {
2475  case Instruction::Xor:
2476  if (Instruction *I = foldICmpXorConstant(Cmp, BO, *C))
2477  return I;
2478  break;
2479  case Instruction::And:
2480  if (Instruction *I = foldICmpAndConstant(Cmp, BO, *C))
2481  return I;
2482  break;
2483  case Instruction::Or:
2484  if (Instruction *I = foldICmpOrConstant(Cmp, BO, *C))
2485  return I;
2486  break;
2487  case Instruction::Mul:
2488  if (Instruction *I = foldICmpMulConstant(Cmp, BO, *C))
2489  return I;
2490  break;
2491  case Instruction::Shl:
2492  if (Instruction *I = foldICmpShlConstant(Cmp, BO, *C))
2493  return I;
2494  break;
2495  case Instruction::LShr:
2496  case Instruction::AShr:
2497  if (Instruction *I = foldICmpShrConstant(Cmp, BO, *C))
2498  return I;
2499  break;
2500  case Instruction::UDiv:
2501  if (Instruction *I = foldICmpUDivConstant(Cmp, BO, *C))
2502  return I;
2504  case Instruction::SDiv:
2505  if (Instruction *I = foldICmpDivConstant(Cmp, BO, *C))
2506  return I;
2507  break;
2508  case Instruction::Sub:
2509  if (Instruction *I = foldICmpSubConstant(Cmp, BO, *C))
2510  return I;
2511  break;
2512  case Instruction::Add:
2513  if (Instruction *I = foldICmpAddConstant(Cmp, BO, *C))
2514  return I;
2515  break;
2516  default:
2517  break;
2518  }
2519  // TODO: These folds could be refactored to be part of the above calls.
2520  if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, *C))
2521  return I;
2522  }
2523 
2524  // Match against CmpInst LHS being instructions other than binary operators.
2525 
2526  if (auto *SI = dyn_cast<SelectInst>(Cmp.getOperand(0))) {
2527  // For now, we only support constant integers while folding the
2528  // ICMP(SELECT)) pattern. We can extend this to support vector of integers
2529  // similar to the cases handled by binary ops above.
2530  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
2531  if (Instruction *I = foldICmpSelectConstant(Cmp, SI, ConstRHS))
2532  return I;
2533  }
2534 
2535  if (auto *TI = dyn_cast<TruncInst>(Cmp.getOperand(0))) {
2536  if (Instruction *I = foldICmpTruncConstant(Cmp, TI, *C))
2537  return I;
2538  }
2539 
2540  if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, *C))
2541  return I;
2542 
2543  return nullptr;
2544 }
2545 
2546 /// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2547 /// icmp eq/ne BO, C.
2548 Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2549  BinaryOperator *BO,
2550  const APInt &C) {
2551  // TODO: Some of these folds could work with arbitrary constants, but this
2552  // function is limited to scalar and vector splat constants.
2553  if (!Cmp.isEquality())
2554  return nullptr;
2555 
2556  ICmpInst::Predicate Pred = Cmp.getPredicate();
2557  bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2558  Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2559  Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2560 
2561  switch (BO->getOpcode()) {
2562  case Instruction::SRem:
2563  // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2564  if (C.isNullValue() && BO->hasOneUse()) {
2565  const APInt *BOC;
2566  if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2567  Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
2568  return new ICmpInst(Pred, NewRem,
2570  }
2571  }
2572  break;
2573  case Instruction::Add: {
2574  // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2575  const APInt *BOC;
2576  if (match(BOp1, m_APInt(BOC))) {
2577  if (BO->hasOneUse()) {
2578  Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2579  return new ICmpInst(Pred, BOp0, SubC);
2580  }
2581  } else if (C.isNullValue()) {
2582  // Replace ((add A, B) != 0) with (A != -B) if A or B is
2583  // efficiently invertible, or if the add has just this one use.
2584  if (Value *NegVal = dyn_castNegVal(BOp1))
2585  return new ICmpInst(Pred, BOp0, NegVal);
2586  if (Value *NegVal = dyn_castNegVal(BOp0))
2587  return new ICmpInst(Pred, NegVal, BOp1);
2588  if (BO->hasOneUse()) {
2589  Value *Neg = Builder.CreateNeg(BOp1);
2590  Neg->takeName(BO);
2591  return new ICmpInst(Pred, BOp0, Neg);
2592  }
2593  }
2594  break;
2595  }
2596  case Instruction::Xor:
2597  if (BO->hasOneUse()) {
2598  if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2599  // For the xor case, we can xor two constants together, eliminating
2600  // the explicit xor.
2601  return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2602  } else if (C.isNullValue()) {
2603  // Replace ((xor A, B) != 0) with (A != B)
2604  return new ICmpInst(Pred, BOp0, BOp1);
2605  }
2606  }
2607  break;
2608  case Instruction::Sub:
2609  if (BO->hasOneUse()) {
2610  const APInt *BOC;
2611  if (match(BOp0, m_APInt(BOC))) {
2612  // Replace ((sub BOC, B) != C) with (B != BOC-C).
2613  Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2614  return new ICmpInst(Pred, BOp1, SubC);
2615  } else if (C.isNullValue()) {
2616  // Replace ((sub A, B) != 0) with (A != B).
2617  return new ICmpInst(Pred, BOp0, BOp1);
2618  }
2619  }
2620  break;
2621  case Instruction::Or: {
2622  const APInt *BOC;
2623  if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2624  // Comparing if all bits outside of a constant mask are set?
2625  // Replace (X | C) == -1 with (X & ~C) == ~C.
2626  // This removes the -1 constant.
2627  Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2628  Value *And = Builder.CreateAnd(BOp0, NotBOC);
2629  return new ICmpInst(Pred, And, NotBOC);
2630  }
2631  break;
2632  }
2633  case Instruction::And: {
2634  const APInt *BOC;
2635  if (match(BOp1, m_APInt(BOC))) {
2636  // If we have ((X & C) == C), turn it into ((X & C) != 0).
2637  if (C == *BOC && C.isPowerOf2())
2638  return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2639  BO, Constant::getNullValue(RHS->getType()));
2640 
2641  // Don't perform the following transforms if the AND has multiple uses
2642  if (!BO->hasOneUse())
2643  break;
2644 
2645  // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2646  if (BOC->isSignMask()) {
2647  Constant *Zero = Constant::getNullValue(BOp0->getType());
2648  auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2649  return new ICmpInst(NewPred, BOp0, Zero);
2650  }
2651 
2652  // ((X & ~7) == 0) --> X < 8
2653  if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
2654  Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2655  auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2656  return new ICmpInst(NewPred, BOp0, NegBOC);
2657  }
2658  }
2659  break;
2660  }
2661  case Instruction::Mul:
2662  if (C.isNullValue() && BO->hasNoSignedWrap()) {
2663  const APInt *BOC;
2664  if (match(BOp1, m_APInt(BOC)) && !BOC->isNullValue()) {
2665  // The trivial case (mul X, 0) is handled by InstSimplify.
2666  // General case : (mul X, C) != 0 iff X != 0
2667  // (mul X, C) == 0 iff X == 0
2668  return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2669  }
2670  }
2671  break;
2672  case Instruction::UDiv:
2673  if (C.isNullValue()) {
2674  // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2675  auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2676  return new ICmpInst(NewPred, BOp1, BOp0);
2677  }
2678  break;
2679  default:
2680  break;
2681  }
2682  return nullptr;
2683 }
2684 
2685 /// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2686 Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2687  const APInt &C) {
2689  if (!II || !Cmp.isEquality())
2690  return nullptr;
2691 
2692  // Handle icmp {eq|ne} <intrinsic>, Constant.
2693  Type *Ty = II->getType();
2694  switch (II->getIntrinsicID()) {
2695  case Intrinsic::bswap:
2696  Worklist.Add(II);
2697  Cmp.setOperand(0, II->getArgOperand(0));
2698  Cmp.setOperand(1, ConstantInt::get(Ty, C.byteSwap()));
2699  return &Cmp;
2700 
2701  case Intrinsic::ctlz:
2702  case Intrinsic::cttz:
2703  // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2704  if (C == C.getBitWidth()) {
2705  Worklist.Add(II);
2706  Cmp.setOperand(0, II->getArgOperand(0));
2708  return &Cmp;
2709  }
2710  break;
2711 
2712  case Intrinsic::ctpop: {
2713  // popcount(A) == 0 -> A == 0 and likewise for !=
2714  // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2715  bool IsZero = C.isNullValue();
2716  if (IsZero || C == C.getBitWidth()) {
2717  Worklist.Add(II);
2718  Cmp.setOperand(0, II->getArgOperand(0));
2719  auto *NewOp =
2721  Cmp.setOperand(1, NewOp);
2722  return &Cmp;
2723  }
2724  break;
2725  }
2726  default:
2727  break;
2728  }
2729 
2730  return nullptr;
2731 }
2732 
2733 /// Handle icmp with constant (but not simple integer constant) RHS.
2734 Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2735  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2736  Constant *RHSC = dyn_cast<Constant>(Op1);
2737  Instruction *LHSI = dyn_cast<Instruction>(Op0);
2738  if (!RHSC || !LHSI)
2739  return nullptr;
2740 
2741  switch (LHSI->getOpcode()) {
2742  case Instruction::GetElementPtr:
2743  // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2744  if (RHSC->isNullValue() &&
2745  cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2746  return new ICmpInst(
2747  I.getPredicate(), LHSI->getOperand(0),
2748  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2749  break;
2750  case Instruction::PHI:
2751  // Only fold icmp into the PHI if the phi and icmp are in the same
2752  // block. If in the same block, we're encouraging jump threading. If
2753  // not, we are just pessimizing the code by making an i1 phi.
2754  if (LHSI->getParent() == I.getParent())
2755  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2756  return NV;
2757  break;
2758  case Instruction::Select: {
2759  // If either operand of the select is a constant, we can fold the
2760  // comparison into the select arms, which will cause one to be
2761  // constant folded and the select turned into a bitwise or.
2762  Value *Op1 = nullptr, *Op2 = nullptr;
2763  ConstantInt *CI = nullptr;
2764  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2765  Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2766  CI = dyn_cast<ConstantInt>(Op1);
2767  }
2768  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2769  Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2770  CI = dyn_cast<ConstantInt>(Op2);
2771  }
2772 
2773  // We only want to perform this transformation if it will not lead to
2774  // additional code. This is true if either both sides of the select
2775  // fold to a constant (in which case the icmp is replaced with a select
2776  // which will usually simplify) or this is the only user of the
2777  // select (in which case we are trading a select+icmp for a simpler
2778  // select+icmp) or all uses of the select can be replaced based on
2779  // dominance information ("Global cases").
2780  bool Transform = false;
2781  if (Op1 && Op2)
2782  Transform = true;
2783  else if (Op1 || Op2) {
2784  // Local case
2785  if (LHSI->hasOneUse())
2786  Transform = true;
2787  // Global cases
2788  else if (CI && !CI->isZero())
2789  // When Op1 is constant try replacing select with second operand.
2790  // Otherwise Op2 is constant and try replacing select with first
2791  // operand.
2792  Transform =
2793  replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2794  }
2795  if (Transform) {
2796  if (!Op1)
2797  Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2798  I.getName());
2799  if (!Op2)
2800  Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2801  I.getName());
2802  return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2803  }
2804  break;
2805  }
2806  case Instruction::IntToPtr:
2807  // icmp pred inttoptr(X), null -> icmp pred X, 0
2808  if (RHSC->isNullValue() &&
2809  DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2810  return new ICmpInst(
2811  I.getPredicate(), LHSI->getOperand(0),
2812  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2813  break;
2814 
2815  case Instruction::Load:
2816  // Try to optimize things like "A[i] > 4" to index computations.
2817  if (GetElementPtrInst *GEP =
2818  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2819  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2820  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2821  !cast<LoadInst>(LHSI)->isVolatile())
2822  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2823  return Res;
2824  }
2825  break;
2826  }
2827 
2828  return nullptr;
2829 }
2830 
2831 /// Try to fold icmp (binop), X or icmp X, (binop).
2832 /// TODO: A large part of this logic is duplicated in InstSimplify's
2833 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
2834 /// duplication.
2835 Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2836  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2837 
2838  // Special logic for binary operators.
2839  BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2840  BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2841  if (!BO0 && !BO1)
2842  return nullptr;
2843 
2844  const CmpInst::Predicate Pred = I.getPredicate();
2845  bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2846  if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2847  NoOp0WrapProblem =
2848  ICmpInst::isEquality(Pred) ||
2849  (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2850  (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2851  if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2852  NoOp1WrapProblem =
2853  ICmpInst::isEquality(Pred) ||
2854  (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2855  (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2856 
2857  // Analyze the case when either Op0 or Op1 is an add instruction.
2858  // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2859  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2860  if (BO0 && BO0->getOpcode() == Instruction::Add) {
2861  A = BO0->getOperand(0);
2862  B = BO0->getOperand(1);
2863  }
2864  if (BO1 && BO1->getOpcode() == Instruction::Add) {
2865  C = BO1->getOperand(0);
2866  D = BO1->getOperand(1);
2867  }
2868 
2869  // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2870  if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2871  return new ICmpInst(Pred, A == Op1 ? B : A,
2872  Constant::getNullValue(Op1->getType()));
2873 
2874  // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2875  if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2876  return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2877  C == Op0 ? D : C);
2878 
2879  // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2880  if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2881  NoOp1WrapProblem &&
2882  // Try not to increase register pressure.
2883  BO0->hasOneUse() && BO1->hasOneUse()) {
2884  // Determine Y and Z in the form icmp (X+Y), (X+Z).
2885  Value *Y, *Z;
2886  if (A == C) {
2887  // C + B == C + D -> B == D
2888  Y = B;
2889  Z = D;
2890  } else if (A == D) {
2891  // D + B == C + D -> B == C
2892  Y = B;
2893  Z = C;
2894  } else if (B == C) {
2895  // A + C == C + D -> A == D
2896  Y = A;
2897  Z = D;
2898  } else {
2899  assert(B == D);
2900  // A + D == C + D -> A == C
2901  Y = A;
2902  Z = C;
2903  }
2904  return new ICmpInst(Pred, Y, Z);
2905  }
2906 
2907  // icmp slt (X + -1), Y -> icmp sle X, Y
2908  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2909  match(B, m_AllOnes()))
2910  return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2911 
2912  // icmp sge (X + -1), Y -> icmp sgt X, Y
2913  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2914  match(B, m_AllOnes()))
2915  return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2916 
2917  // icmp sle (X + 1), Y -> icmp slt X, Y
2918  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2919  return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2920 
2921  // icmp sgt (X + 1), Y -> icmp sge X, Y
2922  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2923  return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2924 
2925  // icmp sgt X, (Y + -1) -> icmp sge X, Y
2926  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2927  match(D, m_AllOnes()))
2928  return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2929 
2930  // icmp sle X, (Y + -1) -> icmp slt X, Y
2931  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2932  match(D, m_AllOnes()))
2933  return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2934 
2935  // icmp sge X, (Y + 1) -> icmp sgt X, Y
2936  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
2937  return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
2938 
2939  // icmp slt X, (Y + 1) -> icmp sle X, Y
2940  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
2941  return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
2942 
2943  // TODO: The subtraction-related identities shown below also hold, but
2944  // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
2945  // wouldn't happen even if they were implemented.
2946  //
2947  // icmp ult (X - 1), Y -> icmp ule X, Y
2948  // icmp uge (X - 1), Y -> icmp ugt X, Y
2949  // icmp ugt X, (Y - 1) -> icmp uge X, Y
2950  // icmp ule X, (Y - 1) -> icmp ult X, Y
2951 
2952  // icmp ule (X + 1), Y -> icmp ult X, Y
2953  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
2954  return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
2955 
2956  // icmp ugt (X + 1), Y -> icmp uge X, Y
2957  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
2958  return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
2959 
2960  // icmp uge X, (Y + 1) -> icmp ugt X, Y
2961  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
2962  return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
2963 
2964  // icmp ult X, (Y + 1) -> icmp ule X, Y
2965  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
2966  return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
2967 
2968  // if C1 has greater magnitude than C2:
2969  // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
2970  // s.t. C3 = C1 - C2
2971  //
2972  // if C2 has greater magnitude than C1:
2973  // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
2974  // s.t. C3 = C2 - C1
2975  if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
2976  (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
2977  if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
2978  if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
2979  const APInt &AP1 = C1->getValue();
2980  const APInt &AP2 = C2->getValue();
2981  if (AP1.isNegative() == AP2.isNegative()) {
2982  APInt AP1Abs = C1->getValue().abs();
2983  APInt AP2Abs = C2->getValue().abs();
2984  if (AP1Abs.uge(AP2Abs)) {
2985  ConstantInt *C3 = Builder.getInt(AP1 - AP2);
2986  Value *NewAdd = Builder.CreateNSWAdd(A, C3);
2987  return new ICmpInst(Pred, NewAdd, C);
2988  } else {
2989  ConstantInt *C3 = Builder.getInt(AP2 - AP1);
2990  Value *NewAdd = Builder.CreateNSWAdd(C, C3);
2991  return new ICmpInst(Pred, A, NewAdd);
2992  }
2993  }
2994  }
2995 
2996  // Analyze the case when either Op0 or Op1 is a sub instruction.
2997  // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
2998  A = nullptr;
2999  B = nullptr;
3000  C = nullptr;
3001  D = nullptr;
3002  if (BO0 && BO0->getOpcode() == Instruction::Sub) {
3003  A = BO0->getOperand(0);
3004  B = BO0->getOperand(1);
3005  }
3006  if (BO1 && BO1->getOpcode() == Instruction::Sub) {
3007  C = BO1->getOperand(0);
3008  D = BO1->getOperand(1);
3009  }
3010 
3011  // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
3012  if (A == Op1 && NoOp0WrapProblem)
3013  return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
3014 
3015  // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
3016  if (C == Op0 && NoOp1WrapProblem)
3017  return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
3018 
3019  // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
3020  if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
3021  // Try not to increase register pressure.
3022  BO0->hasOneUse() && BO1->hasOneUse())
3023  return new ICmpInst(Pred, A, C);
3024 
3025  // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
3026  if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
3027  // Try not to increase register pressure.
3028  BO0->hasOneUse() && BO1->hasOneUse())
3029  return new ICmpInst(Pred, D, B);
3030 
3031  // icmp (0-X) < cst --> x > -cst
3032  if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
3033  Value *X;
3034  if (match(BO0, m_Neg(m_Value(X))))
3035  if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3036  if (!RHSC->isMinValue(/*isSigned=*/true))
3037  return new ICmpInst(I.getSwappedPredicate(), X,
3038  ConstantExpr::getNeg(RHSC));
3039  }
3040 
3041  BinaryOperator *SRem = nullptr;
3042  // icmp (srem X, Y), Y
3043  if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
3044  SRem = BO0;
3045  // icmp Y, (srem X, Y)
3046  else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3047  Op0 == BO1->getOperand(1))
3048  SRem = BO1;
3049  if (SRem) {
3050  // We don't check hasOneUse to avoid increasing register pressure because
3051  // the value we use is the same value this instruction was already using.
3052  switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3053  default:
3054  break;
3055  case ICmpInst::ICMP_EQ:
3056  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3057  case ICmpInst::ICMP_NE:
3058  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3059  case ICmpInst::ICMP_SGT:
3060  case ICmpInst::ICMP_SGE:
3061  return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3063  case ICmpInst::ICMP_SLT:
3064  case ICmpInst::ICMP_SLE:
3065  return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3066  Constant::getNullValue(SRem->getType()));
3067  }
3068  }
3069 
3070  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3071  BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3072  switch (BO0->getOpcode()) {
3073  default:
3074  break;
3075  case Instruction::Add:
3076  case Instruction::Sub:
3077  case Instruction::Xor: {
3078  if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3079  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3080 
3081  const APInt *C;
3082  if (match(BO0->getOperand(1), m_APInt(C))) {
3083  // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3084  if (C->isSignMask()) {
3085  ICmpInst::Predicate NewPred =
3087  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3088  }
3089 
3090  // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
3091  if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
3092  ICmpInst::Predicate NewPred =
3094  NewPred = I.getSwappedPredicate(NewPred);
3095  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3096  }
3097  }
3098  break;
3099  }
3100  case Instruction::Mul: {
3101  if (!I.isEquality())
3102  break;
3103 
3104  const APInt *C;
3105  if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
3106  !C->isOneValue()) {
3107  // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
3108  // Mask = -1 >> count-trailing-zeros(C).
3109  if (unsigned TZs = C->countTrailingZeros()) {
3111  BO0->getType(),
3112  APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
3113  Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
3114  Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
3115  return new ICmpInst(Pred, And1, And2);
3116  }
3117  // If there are no trailing zeros in the multiplier, just eliminate
3118  // the multiplies (no masking is needed):
3119  // icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
3120  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3121  }
3122  break;
3123  }
3124  case Instruction::UDiv:
3125  case Instruction::LShr:
3126  if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
3127  break;
3128  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3129 
3130  case Instruction::SDiv:
3131  if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
3132  break;
3133  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3134 
3135  case Instruction::AShr:
3136  if (!BO0->isExact() || !BO1->isExact())
3137  break;
3138  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3139 
3140  case Instruction::Shl: {
3141  bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3142  bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3143  if (!NUW && !NSW)
3144  break;
3145  if (!NSW && I.isSigned())
3146  break;
3147  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3148  }
3149  }
3150  }
3151 
3152  if (BO0) {
3153  // Transform A & (L - 1) `ult` L --> L != 0
3154  auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3155  auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
3156 
3157  if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
3158  auto *Zero = Constant::getNullValue(BO0->getType());
3159  return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3160  }
3161  }
3162 
3163  return nullptr;
3164 }
3165 
3166 /// Fold icmp Pred min|max(X, Y), X.
3168  ICmpInst::Predicate Pred = Cmp.getPredicate();
3169  Value *Op0 = Cmp.getOperand(0);
3170  Value *X = Cmp.getOperand(1);
3171 
3172  // Canonicalize minimum or maximum operand to LHS of the icmp.
3173  if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3174  match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3175  match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3176  match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3177  std::swap(Op0, X);
3178  Pred = Cmp.getSwappedPredicate();
3179  }
3180 
3181  Value *Y;
3182  if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3183  // smin(X, Y) == X --> X s<= Y
3184  // smin(X, Y) s>= X --> X s<= Y
3185  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3186  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3187 
3188  // smin(X, Y) != X --> X s> Y
3189  // smin(X, Y) s< X --> X s> Y
3190  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3191  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3192 
3193  // These cases should be handled in InstSimplify:
3194  // smin(X, Y) s<= X --> true
3195  // smin(X, Y) s> X --> false
3196  return nullptr;
3197  }
3198 
3199  if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3200  // smax(X, Y) == X --> X s>= Y
3201  // smax(X, Y) s<= X --> X s>= Y
3202  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3203  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3204 
3205  // smax(X, Y) != X --> X s< Y
3206  // smax(X, Y) s> X --> X s< Y
3207  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3208  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3209 
3210  // These cases should be handled in InstSimplify:
3211  // smax(X, Y) s>= X --> true
3212  // smax(X, Y) s< X --> false
3213  return nullptr;
3214  }
3215 
3216  if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3217  // umin(X, Y) == X --> X u<= Y
3218  // umin(X, Y) u>= X --> X u<= Y
3219  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3220  return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3221 
3222  // umin(X, Y) != X --> X u> Y
3223  // umin(X, Y) u< X --> X u> Y
3224  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3225  return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3226 
3227  // These cases should be handled in InstSimplify:
3228  // umin(X, Y) u<= X --> true
3229  // umin(X, Y) u> X --> false
3230  return nullptr;
3231  }
3232 
3233  if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3234  // umax(X, Y) == X --> X u>= Y
3235  // umax(X, Y) u<= X --> X u>= Y
3236  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3237  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3238 
3239  // umax(X, Y) != X --> X u< Y
3240  // umax(X, Y) u> X --> X u< Y
3241  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3242  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3243 
3244  // These cases should be handled in InstSimplify:
3245  // umax(X, Y) u>= X --> true
3246  // umax(X, Y) u< X --> false
3247  return nullptr;
3248  }
3249 
3250  return nullptr;
3251 }
3252 
3253 Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3254  if (!I.isEquality())
3255  return nullptr;
3256 
3257  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3258  const CmpInst::Predicate Pred = I.getPredicate();
3259  Value *A, *B, *C, *D;
3260  if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3261  if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3262  Value *OtherVal = A == Op1 ? B : A;
3263  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3264  }
3265 
3266  if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3267  // A^c1 == C^c2 --> A == C^(c1^c2)
3268  ConstantInt *C1, *C2;
3269  if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3270  Op1->hasOneUse()) {
3271  Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
3272  Value *Xor = Builder.CreateXor(C, NC);
3273  return new ICmpInst(Pred, A, Xor);
3274  }
3275 
3276  // A^B == A^D -> B == D
3277  if (A == C)
3278  return new ICmpInst(Pred, B, D);
3279  if (A == D)
3280  return new ICmpInst(Pred, B, C);
3281  if (B == C)
3282  return new ICmpInst(Pred, A, D);
3283  if (B == D)
3284  return new ICmpInst(Pred, A, C);
3285  }
3286  }
3287 
3288  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3289  // A == (A^B) -> B == 0
3290  Value *OtherVal = A == Op0 ? B : A;
3291  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3292  }
3293 
3294  // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3295  if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3296  match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3297  Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3298 
3299  if (A == C) {
3300  X = B;
3301  Y = D;
3302  Z = A;
3303  } else if (A == D) {
3304  X = B;
3305  Y = C;
3306  Z = A;
3307  } else if (B == C) {
3308  X = A;
3309  Y = D;
3310  Z = B;
3311  } else if (B == D) {
3312  X = A;
3313  Y = C;
3314  Z = B;
3315  }
3316 
3317  if (X) { // Build (X^Y) & Z
3318  Op1 = Builder.CreateXor(X, Y);
3319  Op1 = Builder.CreateAnd(Op1, Z);
3320  I.setOperand(0, Op1);
3321  I.setOperand(1, Constant::getNullValue(Op1->getType()));
3322  return &I;
3323  }
3324  }
3325 
3326  // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3327  // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3328  ConstantInt *Cst1;
3329  if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3330  match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3331  (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3332  match(Op1, m_ZExt(m_Value(A))))) {
3333  APInt Pow2 = Cst1->getValue() + 1;
3334  if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3335  Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3336  return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
3337  }
3338 
3339  // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3340  // For lshr and ashr pairs.
3341  if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3342  match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3343  (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3344  match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3345  unsigned TypeBits = Cst1->getBitWidth();
3346  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3347  if (ShAmt < TypeBits && ShAmt != 0) {
3348  ICmpInst::Predicate NewPred =
3350  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3351  APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3352  return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
3353  }
3354  }
3355 
3356  // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3357  if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3358  match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3359  unsigned TypeBits = Cst1->getBitWidth();
3360  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3361  if (ShAmt < TypeBits && ShAmt != 0) {
3362  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3363  APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3364  Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
3365  I.getName() + ".mask");
3366  return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
3367  }
3368  }
3369 
3370  // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3371  // "icmp (and X, mask), cst"
3372  uint64_t ShAmt = 0;
3373  if (Op0->hasOneUse() &&
3374  match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3375  match(Op1, m_ConstantInt(Cst1)) &&
3376  // Only do this when A has multiple uses. This is most important to do
3377  // when it exposes other optimizations.
3378  !A->hasOneUse()) {
3379  unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3380 
3381  if (ShAmt < ASize) {
3382  APInt MaskV =
3384  MaskV <<= ShAmt;
3385 
3386  APInt CmpV = Cst1->getValue().zext(ASize);
3387  CmpV <<= ShAmt;
3388 
3389  Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
3390  return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
3391  }
3392  }
3393 
3394  // If both operands are byte-swapped or bit-reversed, just compare the
3395  // original values.
3396  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
3397  // and handle more intrinsics.
3398  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
3399  (match(Op0, m_BitReverse(m_Value(A))) &&
3400  match(Op1, m_BitReverse(m_Value(B)))))
3401  return new ICmpInst(Pred, A, B);
3402 
3403  return nullptr;
3404 }
3405 
3406 /// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3407 /// far.
3408 Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3409  const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3410  Value *LHSCIOp = LHSCI->getOperand(0);
3411  Type *SrcTy = LHSCIOp->getType();
3412  Type *DestTy = LHSCI->getType();
3413  Value *RHSCIOp;
3414 
3415  // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3416  // integer type is the same size as the pointer type.
3417  if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3418  DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
3419  Value *RHSOp = nullptr;
3420  if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3421  Value *RHSCIOp = RHSC->getOperand(0);
3422  if (RHSCIOp->getType()->getPointerAddressSpace() ==
3423  LHSCIOp->getType()->getPointerAddressSpace()) {
3424  RHSOp = RHSC->getOperand(0);
3425  // If the pointer types don't match, insert a bitcast.
3426  if (LHSCIOp->getType() != RHSOp->getType())
3427  RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
3428  }
3429  } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3430  RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3431  }
3432 
3433  if (RHSOp)
3434  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3435  }
3436 
3437  // The code below only handles extension cast instructions, so far.
3438  // Enforce this.
3439  if (LHSCI->getOpcode() != Instruction::ZExt &&
3440  LHSCI->getOpcode() != Instruction::SExt)
3441  return nullptr;
3442 
3443  bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3444  bool isSignedCmp = ICmp.isSigned();
3445 
3446  if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3447  // Not an extension from the same type?
3448  RHSCIOp = CI->getOperand(0);
3449  if (RHSCIOp->getType() != LHSCIOp->getType())
3450  return nullptr;
3451 
3452  // If the signedness of the two casts doesn't agree (i.e. one is a sext
3453  // and the other is a zext), then we can't handle this.
3454  if (CI->getOpcode() != LHSCI->getOpcode())
3455  return nullptr;
3456 
3457  // Deal with equality cases early.
3458  if (ICmp.isEquality())
3459  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3460 
3461  // A signed comparison of sign extended values simplifies into a
3462  // signed comparison.
3463  if (isSignedCmp && isSignedExt)
3464  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3465 
3466  // The other three cases all fold into an unsigned comparison.
3467  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3468  }
3469 
3470  // If we aren't dealing with a constant on the RHS, exit early.
3471  auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3472  if (!C)
3473  return nullptr;
3474 
3475  // Compute the constant that would happen if we truncated to SrcTy then
3476  // re-extended to DestTy.
3477  Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3478  Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3479 
3480  // If the re-extended constant didn't change...
3481  if (Res2 == C) {
3482  // Deal with equality cases early.
3483  if (ICmp.isEquality())
3484  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3485 
3486  // A signed comparison of sign extended values simplifies into a
3487  // signed comparison.
3488  if (isSignedExt && isSignedCmp)
3489  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3490 
3491  // The other three cases all fold into an unsigned comparison.
3492  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3493  }
3494 
3495  // The re-extended constant changed, partly changed (in the case of a vector),
3496  // or could not be determined to be equal (in the case of a constant
3497  // expression), so the constant cannot be represented in the shorter type.
3498  // Consequently, we cannot emit a simple comparison.
3499  // All the cases that fold to true or false will have already been handled
3500  // by SimplifyICmpInst, so only deal with the tricky case.
3501 
3502  if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3503  return nullptr;
3504 
3505  // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3506  // should have been folded away previously and not enter in here.
3507 
3508  // We're performing an unsigned comp with a sign extended value.
3509  // This is true if the input is >= 0. [aka >s -1]
3510  Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3511  Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3512 
3513  // Finally, return the value computed.
3514  if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3515  return replaceInstUsesWith(ICmp, Result);
3516 
3517  assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
3518  return BinaryOperator::CreateNot(Result);
3519 }
3520 
3521 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3522  Value *RHS, Instruction &OrigI,
3523  Value *&Result, Constant *&Overflow) {
3524  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3525  std::swap(LHS, RHS);
3526 
3527  auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3528  Result = OpResult;
3529  Overflow = OverflowVal;
3530  if (ReuseName)
3531  Result->takeName(&OrigI);
3532  return true;
3533  };
3534 
3535  // If the overflow check was an add followed by a compare, the insertion point
3536  // may be pointing to the compare. We want to insert the new instructions
3537  // before the add in case there are uses of the add between the add and the
3538  // compare.
3539  Builder.SetInsertPoint(&OrigI);
3540 
3541  switch (OCF) {
3542  case OCF_INVALID:
3543  llvm_unreachable("bad overflow check kind!");
3544 
3545  case OCF_UNSIGNED_ADD: {
3546  OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3548  return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
3549  true);
3550 
3552  return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
3553 
3554  // Fall through uadd into sadd
3556  }
3557  case OCF_SIGNED_ADD: {
3558  // X + 0 -> {X, false}
3559  if (match(RHS, m_Zero()))
3560  return SetResult(LHS, Builder.getFalse(), false);
3561 
3562  // We can strength reduce this signed add into a regular add if we can prove
3563  // that it will never overflow.
3564  if (OCF == OCF_SIGNED_ADD)
3565  if (willNotOverflowSignedAdd(LHS, RHS, OrigI))
3566  return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
3567  true);
3568  break;
3569  }
3570 
3571  case OCF_UNSIGNED_SUB:
3572  case OCF_SIGNED_SUB: {
3573  // X - 0 -> {X, false}
3574  if (match(RHS, m_Zero()))
3575  return SetResult(LHS, Builder.getFalse(), false);
3576 
3577  if (OCF == OCF_SIGNED_SUB) {
3578  if (willNotOverflowSignedSub(LHS, RHS, OrigI))
3579  return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
3580  true);
3581  } else {
3582  if (willNotOverflowUnsignedSub(LHS, RHS, OrigI))
3583  return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
3584  true);
3585  }
3586  break;
3587  }
3588 
3589  case OCF_UNSIGNED_MUL: {
3590  OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3592  return SetResult(Builder.CreateNUWMul(LHS, RHS), Builder.getFalse(),
3593  true);
3595  return SetResult(Builder.CreateMul(LHS, RHS), Builder.getTrue(), true);
3597  }
3598  case OCF_SIGNED_MUL:
3599  // X * undef -> undef
3600  if (isa<UndefValue>(RHS))
3601  return SetResult(RHS, UndefValue::get(Builder.getInt1Ty()), false);
3602 
3603  // X * 0 -> {0, false}
3604  if (match(RHS, m_Zero()))
3605  return SetResult(RHS, Builder.getFalse(), false);
3606 
3607  // X * 1 -> {X, false}
3608  if (match(RHS, m_One()))
3609  return SetResult(LHS, Builder.getFalse(), false);
3610 
3611  if (OCF == OCF_SIGNED_MUL)
3612  if (willNotOverflowSignedMul(LHS, RHS, OrigI))
3613  return SetResult(Builder.CreateNSWMul(LHS, RHS), Builder.getFalse(),
3614  true);
3615  break;
3616  }
3617 
3618  return false;
3619 }
3620 
3621 /// \brief Recognize and process idiom involving test for multiplication
3622 /// overflow.
3623 ///
3624 /// The caller has matched a pattern of the form:
3625 /// I = cmp u (mul(zext A, zext B), V
3626 /// The function checks if this is a test for overflow and if so replaces
3627 /// multiplication with call to 'mul.with.overflow' intrinsic.
3628 ///
3629 /// \param I Compare instruction.
3630 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3631 /// the compare instruction. Must be of integer type.
3632 /// \param OtherVal The other argument of compare instruction.
3633 /// \returns Instruction which must replace the compare instruction, NULL if no
3634 /// replacement required.
3636  Value *OtherVal, InstCombiner &IC) {
3637  // Don't bother doing this transformation for pointers, don't do it for
3638  // vectors.
3639  if (!isa<IntegerType>(MulVal->getType()))
3640  return nullptr;
3641 
3642  assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
3643  assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
3644  auto *MulInstr = dyn_cast<Instruction>(MulVal);
3645  if (!MulInstr)
3646  return nullptr;
3647  assert(MulInstr->getOpcode() == Instruction::Mul);
3648 
3649  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3650  *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3651  assert(LHS->getOpcode() == Instruction::ZExt);
3652  assert(RHS->getOpcode() == Instruction::ZExt);
3653  Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3654 
3655  // Calculate type and width of the result produced by mul.with.overflow.
3656  Type *TyA = A->getType(), *TyB = B->getType();
3657  unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3658  WidthB = TyB->getPrimitiveSizeInBits();
3659  unsigned MulWidth;
3660  Type *MulType;
3661  if (WidthB > WidthA) {
3662  MulWidth = WidthB;
3663  MulType = TyB;
3664  } else {
3665  MulWidth = WidthA;
3666  MulType = TyA;
3667  }
3668 
3669  // In order to replace the original mul with a narrower mul.with.overflow,
3670  // all uses must ignore upper bits of the product. The number of used low
3671  // bits must be not greater than the width of mul.with.overflow.
3672  if (MulVal->hasNUsesOrMore(2))
3673  for (User *U : MulVal->users()) {
3674  if (U == &I)
3675  continue;
3676  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3677  // Check if truncation ignores bits above MulWidth.
3678  unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3679  if (TruncWidth > MulWidth)
3680  return nullptr;
3681  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3682  // Check if AND ignores bits above MulWidth.
3683  if (BO->getOpcode() != Instruction::And)
3684  return nullptr;
3685  if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3686  const APInt &CVal = CI->getValue();
3687  if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3688  return nullptr;
3689  } else {
3690  // In this case we could have the operand of the binary operation
3691  // being defined in another block, and performing the replacement
3692  // could break the dominance relation.
3693  return nullptr;
3694  }
3695  } else {
3696  // Other uses prohibit this transformation.
3697  return nullptr;
3698  }
3699  }
3700 
3701  // Recognize patterns
3702  switch (I.getPredicate()) {
3703  case ICmpInst::ICMP_EQ:
3704  case ICmpInst::ICMP_NE:
3705  // Recognize pattern:
3706  // mulval = mul(zext A, zext B)
3707  // cmp eq/neq mulval, zext trunc mulval
3708  if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3709  if (Zext->hasOneUse()) {
3710  Value *ZextArg = Zext->getOperand(0);
3711  if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3712  if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3713  break; //Recognized
3714  }
3715 
3716  // Recognize pattern:
3717  // mulval = mul(zext A, zext B)
3718  // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3719  ConstantInt *CI;
3720  Value *ValToMask;
3721  if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3722  if (ValToMask != MulVal)
3723  return nullptr;
3724  const APInt &CVal = CI->getValue() + 1;
3725  if (CVal.isPowerOf2()) {
3726  unsigned MaskWidth = CVal.logBase2();
3727  if (MaskWidth == MulWidth)
3728  break; // Recognized
3729  }
3730  }
3731  return nullptr;
3732 
3733  case ICmpInst::ICMP_UGT:
3734  // Recognize pattern:
3735  // mulval = mul(zext A, zext B)
3736  // cmp ugt mulval, max
3737  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3738  APInt MaxVal = APInt::getMaxValue(MulWidth);
3739  MaxVal = MaxVal.zext(CI->getBitWidth());
3740  if (MaxVal.eq(CI->getValue()))
3741  break; // Recognized
3742  }
3743  return nullptr;
3744 
3745  case ICmpInst::ICMP_UGE:
3746  // Recognize pattern:
3747  // mulval = mul(zext A, zext B)
3748  // cmp uge mulval, max+1
3749  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3750  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3751  if (MaxVal.eq(CI->getValue()))
3752  break; // Recognized
3753  }
3754  return nullptr;
3755 
3756  case ICmpInst::ICMP_ULE:
3757  // Recognize pattern:
3758  // mulval = mul(zext A, zext B)
3759  // cmp ule mulval, max
3760  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3761  APInt MaxVal = APInt::getMaxValue(MulWidth);
3762  MaxVal = MaxVal.zext(CI->getBitWidth());
3763  if (MaxVal.eq(CI->getValue()))
3764  break; // Recognized
3765  }
3766  return nullptr;
3767 
3768  case ICmpInst::ICMP_ULT:
3769  // Recognize pattern:
3770  // mulval = mul(zext A, zext B)
3771  // cmp ule mulval, max + 1
3772  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3773  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3774  if (MaxVal.eq(CI->getValue()))
3775  break; // Recognized
3776  }
3777  return nullptr;
3778 
3779  default:
3780  return nullptr;
3781  }
3782 
3783  InstCombiner::BuilderTy &Builder = IC.Builder;
3784  Builder.SetInsertPoint(MulInstr);
3785 
3786  // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3787  Value *MulA = A, *MulB = B;
3788  if (WidthA < MulWidth)
3789  MulA = Builder.CreateZExt(A, MulType);
3790  if (WidthB < MulWidth)
3791  MulB = Builder.CreateZExt(B, MulType);
3793  Intrinsic::umul_with_overflow, MulType);
3794  CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
3795  IC.Worklist.Add(MulInstr);
3796 
3797  // If there are uses of mul result other than the comparison, we know that
3798  // they are truncation or binary AND. Change them to use result of
3799  // mul.with.overflow and adjust properly mask/size.
3800  if (MulVal->hasNUsesOrMore(2)) {
3801  Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
3802  for (User *U : MulVal->users()) {
3803  if (U == &I || U == OtherVal)
3804  continue;
3805  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3806  if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3807  IC.replaceInstUsesWith(*TI, Mul);
3808  else
3809  TI->setOperand(0, Mul);
3810  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3811  assert(BO->getOpcode() == Instruction::And);
3812  // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3813  ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3814  APInt ShortMask = CI->getValue().trunc(MulWidth);
3815  Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
3816  Instruction *Zext =
3817  cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
3818  IC.Worklist.Add(Zext);
3819  IC.replaceInstUsesWith(*BO, Zext);
3820  } else {
3821  llvm_unreachable("Unexpected Binary operation");
3822  }
3823  IC.Worklist.Add(cast<Instruction>(U));
3824  }
3825  }
3826  if (isa<Instruction>(OtherVal))
3827  IC.Worklist.Add(cast<Instruction>(OtherVal));
3828 
3829  // The original icmp gets replaced with the overflow value, maybe inverted
3830  // depending on predicate.
3831  bool Inverse = false;
3832  switch (I.getPredicate()) {
3833  case ICmpInst::ICMP_NE:
3834  break;
3835  case ICmpInst::ICMP_EQ:
3836  Inverse = true;
3837  break;
3838  case ICmpInst::ICMP_UGT:
3839  case ICmpInst::ICMP_UGE:
3840  if (I.getOperand(0) == MulVal)
3841  break;
3842  Inverse = true;
3843  break;
3844  case ICmpInst::ICMP_ULT:
3845  case ICmpInst::ICMP_ULE:
3846  if (I.getOperand(1) == MulVal)
3847  break;
3848  Inverse = true;
3849  break;
3850  default:
3851  llvm_unreachable("Unexpected predicate");
3852  }
3853  if (Inverse) {
3854  Value *Res = Builder.CreateExtractValue(Call, 1);
3855  return BinaryOperator::CreateNot(Res);
3856  }
3857 
3858  return ExtractValueInst::Create(Call, 1);
3859 }
3860 
3861 /// When performing a comparison against a constant, it is possible that not all
3862 /// the bits in the LHS are demanded. This helper method computes the mask that
3863 /// IS demanded.
3864 static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth) {
3865  const APInt *RHS;
3866  if (!match(I.getOperand(1), m_APInt(RHS)))
3867  return APInt::getAllOnesValue(BitWidth);
3868 
3869  // If this is a normal comparison, it demands all bits. If it is a sign bit
3870  // comparison, it only demands the sign bit.
3871  bool UnusedBit;
3872  if (isSignBitCheck(I.getPredicate(), *RHS, UnusedBit))
3873  return APInt::getSignMask(BitWidth);
3874 
3875  switch (I.getPredicate()) {
3876  // For a UGT comparison, we don't care about any bits that
3877  // correspond to the trailing ones of the comparand. The value of these
3878  // bits doesn't impact the outcome of the comparison, because any value
3879  // greater than the RHS must differ in a bit higher than these due to carry.
3880  case ICmpInst::ICMP_UGT:
3881  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingOnes());
3882 
3883  // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3884  // Any value less than the RHS must differ in a higher bit because of carries.
3885  case ICmpInst::ICMP_ULT:
3886  return APInt::getBitsSetFrom(BitWidth, RHS->countTrailingZeros());
3887 
3888  default:
3889  return APInt::getAllOnesValue(BitWidth);
3890  }
3891 }
3892 
3893 /// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
3894 /// should be swapped.
3895 /// The decision is based on how many times these two operands are reused
3896 /// as subtract operands and their positions in those instructions.
3897 /// The rational is that several architectures use the same instruction for
3898 /// both subtract and cmp, thus it is better if the order of those operands
3899 /// match.
3900 /// \return true if Op0 and Op1 should be swapped.
3901 static bool swapMayExposeCSEOpportunities(const Value * Op0,
3902  const Value * Op1) {
3903  // Filter out pointer value as those cannot appears directly in subtract.
3904  // FIXME: we may want to go through inttoptrs or bitcasts.
3905  if (Op0->getType()->isPointerTy())
3906  return false;
3907  // Count every uses of both Op0 and Op1 in a subtract.
3908  // Each time Op0 is the first operand, count -1: swapping is bad, the
3909  // subtract has already the same layout as the compare.
3910  // Each time Op0 is the second operand, count +1: swapping is good, the
3911  // subtract has a different layout as the compare.
3912  // At the end, if the benefit is greater than 0, Op0 should come second to
3913  // expose more CSE opportunities.
3914  int GlobalSwapBenefits = 0;
3915  for (const User *U : Op0->users()) {
3916  const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U);
3917  if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
3918  continue;
3919  // If Op0 is the first argument, this is not beneficial to swap the
3920  // arguments.
3921  int LocalSwapBenefits = -1;
3922  unsigned Op1Idx = 1;
3923  if (BinOp->getOperand(Op1Idx) == Op0) {
3924  Op1Idx = 0;
3925  LocalSwapBenefits = 1;
3926  }
3927  if (BinOp->getOperand(Op1Idx) != Op1)
3928  continue;
3929  GlobalSwapBenefits += LocalSwapBenefits;
3930  }
3931  return GlobalSwapBenefits > 0;
3932 }
3933 
3934 /// \brief Check that one use is in the same block as the definition and all
3935 /// other uses are in blocks dominated by a given block.
3936 ///
3937 /// \param DI Definition
3938 /// \param UI Use
3939 /// \param DB Block that must dominate all uses of \p DI outside
3940 /// the parent block
3941 /// \return true when \p UI is the only use of \p DI in the parent block
3942 /// and all other uses of \p DI are in blocks dominated by \p DB.
3943 ///
3945  const Instruction *UI,
3946  const BasicBlock *DB) const {
3947  assert(DI && UI && "Instruction not defined\n");
3948  // Ignore incomplete definitions.
3949  if (!DI->getParent())
3950  return false;
3951  // DI and UI must be in the same block.
3952  if (DI->getParent() != UI->getParent())
3953  return false;
3954  // Protect from self-referencing blocks.
3955  if (DI->getParent() == DB)
3956  return false;
3957  for (const User *U : DI->users()) {
3958  auto *Usr = cast<Instruction>(U);
3959  if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
3960  return false;
3961  }
3962  return true;
3963 }
3964 
3965 /// Return true when the instruction sequence within a block is select-cmp-br.
3966 static bool isChainSelectCmpBranch(const SelectInst *SI) {
3967  const BasicBlock *BB = SI->getParent();
3968  if (!BB)
3969  return false;
3970  auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
3971  if (!BI || BI->getNumSuccessors() != 2)
3972  return false;
3973  auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
3974  if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
3975  return false;
3976  return true;
3977 }
3978 
3979 /// \brief True when a select result is replaced by one of its operands
3980 /// in select-icmp sequence. This will eventually result in the elimination
3981 /// of the select.
3982 ///
3983 /// \param SI Select instruction
3984 /// \param Icmp Compare instruction
3985 /// \param SIOpd Operand that replaces the select
3986 ///
3987 /// Notes:
3988 /// - The replacement is global and requires dominator information
3989 /// - The caller is responsible for the actual replacement
3990 ///
3991 /// Example:
3992 ///
3993 /// entry:
3994 /// %4 = select i1 %3, %C* %0, %C* null
3995 /// %5 = icmp eq %C* %4, null
3996 /// br i1 %5, label %9, label %7
3997 /// ...
3998 /// ; <label>:7 ; preds = %entry
3999 /// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
4000 /// ...
4001 ///
4002 /// can be transformed to
4003 ///
4004 /// %5 = icmp eq %C* %0, null
4005 /// %6 = select i1 %3, i1 %5, i1 true
4006 /// br i1 %6, label %9, label %7
4007 /// ...
4008 /// ; <label>:7 ; preds = %entry
4009 /// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
4010 ///
4011 /// Similar when the first operand of the select is a constant or/and
4012 /// the compare is for not equal rather than equal.
4013 ///
4014 /// NOTE: The function is only called when the select and compare constants
4015 /// are equal, the optimization can work only for EQ predicates. This is not a
4016 /// major restriction since a NE compare should be 'normalized' to an equal
4017 /// compare, which usually happens in the combiner and test case
4018 /// select-cmp-br.ll checks for it.
4020  const ICmpInst *Icmp,
4021  const unsigned SIOpd) {
4022  assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
4023  if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
4024  BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
4025  // The check for the single predecessor is not the best that can be
4026  // done. But it protects efficiently against cases like when SI's
4027  // home block has two successors, Succ and Succ1, and Succ1 predecessor
4028  // of Succ. Then SI can't be replaced by SIOpd because the use that gets
4029  // replaced can be reached on either path. So the uniqueness check
4030  // guarantees that the path all uses of SI (outside SI's parent) are on
4031  // is disjoint from all other paths out of SI. But that information
4032  // is more expensive to compute, and the trade-off here is in favor
4033  // of compile-time. It should also be noticed that we check for a single
4034  // predecessor and not only uniqueness. This to handle the situation when
4035  // Succ and Succ1 points to the same basic block.
4036  if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
4037  NumSel++;
4038  SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
4039  return true;
4040  }
4041  }
4042  return false;
4043 }
4044 
4045 /// Try to fold the comparison based on range information we can get by checking
4046 /// whether bits are known to be zero or one in the inputs.
4047 Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
4048  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4049  Type *Ty = Op0->getType();
4050  ICmpInst::Predicate Pred = I.getPredicate();
4051 
4052  // Get scalar or pointer size.
4053  unsigned BitWidth = Ty->isIntOrIntVectorTy()
4054  ? Ty->getScalarSizeInBits()
4055  : DL.getTypeSizeInBits(Ty->getScalarType());
4056 
4057  if (!BitWidth)
4058  return nullptr;
4059 
4060  KnownBits Op0Known(BitWidth);
4061  KnownBits Op1Known(BitWidth);
4062 
4063  if (SimplifyDemandedBits(&I, 0,
4064  getDemandedBitsLHSMask(I, BitWidth),
4065  Op0Known, 0))
4066  return &I;
4067 
4068  if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4069  Op1Known, 0))
4070  return &I;
4071 
4072  // Given the known and unknown bits, compute a range that the LHS could be
4073  // in. Compute the Min, Max and RHS values based on the known bits. For the
4074  // EQ and NE we use unsigned values.
4075  APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4076  APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4077  if (I.isSigned()) {
4078  computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4079  computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4080  } else {
4081  computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4082  computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4083  }
4084 
4085  // If Min and Max are known to be the same, then SimplifyDemandedBits
4086  // figured out that the LHS is a constant. Constant fold this now, so that
4087  // code below can assume that Min != Max.
4088  if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4089  return new ICmpInst(Pred, ConstantInt::get(Op0->getType(), Op0Min), Op1);
4090  if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4091  return new ICmpInst(Pred, Op0, ConstantInt::get(Op1->getType(), Op1Min));
4092 
4093  // Based on the range information we know about the LHS, see if we can
4094  // simplify this comparison. For example, (x&4) < 8 is always true.
4095  switch (Pred) {
4096  default:
4097  llvm_unreachable("Unknown icmp opcode!");
4098  case ICmpInst::ICMP_EQ:
4099  case ICmpInst::ICMP_NE: {
4100  if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4101  return Pred == CmpInst::ICMP_EQ
4102  ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4103  : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4104  }
4105 
4106  // If all bits are known zero except for one, then we know at most one bit
4107  // is set. If the comparison is against zero, then this is a check to see if
4108  // *that* bit is set.
4109  APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4110  if (Op1Known.isZero()) {
4111  // If the LHS is an AND with the same constant, look through it.
4112  Value *LHS = nullptr;
4113  const APInt *LHSC;
4114  if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4115  *LHSC != Op0KnownZeroInverted)
4116  LHS = Op0;
4117 
4118  Value *X;
4119  if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4120  APInt ValToCheck = Op0KnownZeroInverted;
4121  Type *XTy = X->getType();
4122  if (ValToCheck.isPowerOf2()) {
4123  // ((1 << X) & 8) == 0 -> X != 3
4124  // ((1 << X) & 8) != 0 -> X == 3
4125  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4126  auto NewPred = ICmpInst::getInversePredicate(Pred);
4127  return new ICmpInst(NewPred, X, CmpC);
4128  } else if ((++ValToCheck).isPowerOf2()) {
4129  // ((1 << X) & 7) == 0 -> X >= 3
4130  // ((1 << X) & 7) != 0 -> X < 3
4131  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4132  auto NewPred =
4134  return new ICmpInst(NewPred, X, CmpC);
4135  }
4136  }
4137 
4138  // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4139  const APInt *CI;
4140  if (Op0KnownZeroInverted.isOneValue() &&
4141  match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4142  // ((8 >>u X) & 1) == 0 -> X != 3
4143  // ((8 >>u X) & 1) != 0 -> X == 3
4144  unsigned CmpVal = CI->countTrailingZeros();
4145  auto NewPred = ICmpInst::getInversePredicate(Pred);
4146  return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4147  }
4148  }
4149  break;
4150  }
4151  case ICmpInst::ICMP_ULT: {
4152  if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4153  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4154  if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4155  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4156  if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4157  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4158 
4159  const APInt *CmpC;
4160  if (match(Op1, m_APInt(CmpC))) {
4161  // A <u C -> A == C-1 if min(A)+1 == C
4162  if (*CmpC == Op0Min + 1)
4163  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4164  ConstantInt::get(Op1->getType(), *CmpC - 1));
4165  // X <u C --> X == 0, if the number of zero bits in the bottom of X
4166  // exceeds the log2 of C.
4167  if (Op0Known.countMinTrailingZeros() >= CmpC->ceilLogBase2())
4168  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4169  Constant::getNullValue(Op1->getType()));
4170  }
4171  break;
4172  }
4173  case ICmpInst::ICMP_UGT: {
4174  if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4175  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4176  if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4177  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4178  if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4179  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4180 
4181  const APInt *CmpC;
4182  if (match(Op1, m_APInt(CmpC))) {
4183  // A >u C -> A == C+1 if max(a)-1 == C
4184  if (*CmpC == Op0Max - 1)
4185  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4186  ConstantInt::get(Op1->getType(), *CmpC + 1));
4187  // X >u C --> X != 0, if the number of zero bits in the bottom of X
4188  // exceeds the log2 of C.
4189  if (Op0Known.countMinTrailingZeros() >= CmpC->getActiveBits())
4190  return new ICmpInst(ICmpInst::ICMP_NE, Op0,
4191  Constant::getNullValue(Op1->getType()));
4192  }
4193  break;
4194  }
4195  case ICmpInst::ICMP_SLT: {
4196  if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4197  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4198  if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4199  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4200  if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4201  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4202  const APInt *CmpC;
4203  if (match(Op1, m_APInt(CmpC))) {
4204  if (*CmpC == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4205  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4206  ConstantInt::get(Op1->getType(), *CmpC - 1));
4207  }
4208  break;
4209  }
4210  case ICmpInst::ICMP_SGT: {
4211  if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4212  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4213  if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4214  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4215  if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4216  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4217  const APInt *CmpC;
4218  if (match(Op1, m_APInt(CmpC))) {
4219  if (*CmpC == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4220  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4221  ConstantInt::get(Op1->getType(), *CmpC + 1));
4222  }
4223  break;
4224  }
4225  case ICmpInst::ICMP_SGE:
4226  assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
4227  if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4228  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4229  if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4230  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4231  if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
4232  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4233  break;
4234  case ICmpInst::ICMP_SLE:
4235  assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
4236  if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4237  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4238  if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4239  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4240  if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
4241  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4242  break;
4243  case ICmpInst::ICMP_UGE:
4244  assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
4245  if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4246  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4247  if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4248  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4249  if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
4250  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4251  break;
4252  case ICmpInst::ICMP_ULE:
4253  assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
4254  if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4255  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4256  if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4257  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4258  if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
4259  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
4260  break;
4261  }
4262 
4263  // Turn a signed comparison into an unsigned one if both operands are known to
4264  // have the same sign.
4265  if (I.isSigned() &&
4266  ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4267  (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4268  return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4269 
4270  return nullptr;
4271 }
4272 
4273 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
4274 /// it into the appropriate icmp lt or icmp gt instruction. This transform
4275 /// allows them to be folded in visitICmpInst.
4277  ICmpInst::Predicate Pred = I.getPredicate();
4278  if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4279  Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4280  return nullptr;
4281 
4282  Value *Op0 = I.getOperand(0);
4283  Value *Op1 = I.getOperand(1);
4284  auto *Op1C = dyn_cast<Constant>(Op1);
4285  if (!Op1C)
4286  return nullptr;
4287 
4288  // Check if the constant operand can be safely incremented/decremented without
4289  // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4290  // the edge cases for us, so we just assert on them. For vectors, we must
4291  // handle the edge cases.
4292  Type *Op1Type = Op1->getType();
4293  bool IsSigned = I.isSigned();
4294  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4295  auto *CI = dyn_cast<ConstantInt>(Op1C);
4296  if (CI) {
4297  // A <= MAX -> TRUE ; A >= MIN -> TRUE
4298  assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
4299  } else if (Op1Type->isVectorTy()) {
4300  // TODO? If the edge cases for vectors were guaranteed to be handled as they
4301  // are for scalar, we could remove the min/max checks. However, to do that,
4302  // we would have to use insertelement/shufflevector to replace edge values.
4303  unsigned NumElts = Op1Type->getVectorNumElements();
4304  for (unsigned i = 0; i != NumElts; ++i) {
4305  Constant *Elt = Op1C->getAggregateElement(i);
4306  if (!Elt)
4307  return nullptr;
4308 
4309  if (isa<UndefValue>(Elt))
4310  continue;
4311 
4312  // Bail out if we can't determine if this constant is min/max or if we
4313  // know that this constant is min/max.
4314  auto *CI = dyn_cast<ConstantInt>(Elt);
4315  if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4316  return nullptr;
4317  }
4318  } else {
4319  // ConstantExpr?
4320  return nullptr;
4321  }
4322 
4323  // Increment or decrement the constant and set the new comparison predicate:
4324  // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4325  Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4327  NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4328  return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4329 }
4330 
4331 /// Integer compare with boolean values can always be turned into bitwise ops.
4333  InstCombiner::BuilderTy &Builder) {
4334  Value *A = I.getOperand(0), *B = I.getOperand(1);
4335  assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
4336 
4337  // A boolean compared to true/false can be simplified to Op0/true/false in
4338  // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
4339  // Cases not handled by InstSimplify are always 'not' of Op0.
4340  if (match(B, m_Zero())) {
4341  switch (I.getPredicate()) {
4342  case CmpInst::ICMP_EQ: // A == 0 -> !A
4343  case CmpInst::ICMP_ULE: // A <=u 0 -> !A
4344  case CmpInst::ICMP_SGE: // A >=s 0 -> !A
4345  return BinaryOperator::CreateNot(A);
4346  default:
4347  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4348  }
4349  } else if (match(B, m_One())) {
4350  switch (I.getPredicate()) {
4351  case CmpInst::ICMP_NE: // A != 1 -> !A
4352  case CmpInst::ICMP_ULT: // A <u 1 -> !A
4353  case CmpInst::ICMP_SGT: // A >s -1 -> !A
4354  return BinaryOperator::CreateNot(A);
4355  default:
4356  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4357  }
4358  }
4359 
4360  switch (I.getPredicate()) {
4361  default:
4362  llvm_unreachable("Invalid icmp instruction!");
4363  case ICmpInst::ICMP_EQ:
4364  // icmp eq i1 A, B -> ~(A ^ B)
4365  return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
4366 
4367  case ICmpInst::ICMP_NE:
4368  // icmp ne i1 A, B -> A ^ B
4369  return BinaryOperator::CreateXor(A, B);
4370 
4371  case ICmpInst::ICMP_UGT:
4372  // icmp ugt -> icmp ult
4373  std::swap(A, B);
4375  case ICmpInst::ICMP_ULT:
4376  // icmp ult i1 A, B -> ~A & B
4377  return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
4378 
4379  case ICmpInst::ICMP_SGT:
4380  // icmp sgt -> icmp slt
4381  std::swap(A, B);
4383  case ICmpInst::ICMP_SLT:
4384  // icmp slt i1 A, B -> A & ~B
4385  return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
4386 
4387  case ICmpInst::ICMP_UGE:
4388  // icmp uge -> icmp ule
4389  std::swap(A, B);
4391  case ICmpInst::ICMP_ULE:
4392  // icmp ule i1 A, B -> ~A | B
4393  return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
4394 
4395  case ICmpInst::ICMP_SGE:
4396  // icmp sge -> icmp sle
4397  std::swap(A, B);
4399  case ICmpInst::ICMP_SLE:
4400  // icmp sle i1 A, B -> A | ~B
4401  return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
4402  }
4403 }
4404 
4406  bool Changed = false;
4407  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4408  unsigned Op0Cplxity = getComplexity(Op0);
4409  unsigned Op1Cplxity = getComplexity(Op1);
4410 
4411  /// Orders the operands of the compare so that they are listed from most
4412  /// complex to least complex. This puts constants before unary operators,
4413  /// before binary operators.
4414  if (Op0Cplxity < Op1Cplxity ||
4415  (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4416  I.swapOperands();
4417  std::swap(Op0, Op1);
4418  Changed = true;
4419  }
4420 
4421  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4422  SQ.getWithInstruction(&I)))
4423  return replaceInstUsesWith(I, V);
4424 
4425  // Comparing -val or val with non-zero is the same as just comparing val
4426  // ie, abs(val) != 0 -> val != 0
4427  if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4428  Value *Cond, *SelectTrue, *SelectFalse;
4429  if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4430  m_Value(SelectFalse)))) {
4431  if (Value *V = dyn_castNegVal(SelectTrue)) {
4432  if (V == SelectFalse)
4433  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4434  }
4435  else if (Value *V = dyn_castNegVal(SelectFalse)) {
4436  if (V == SelectTrue)
4437  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4438  }
4439  }
4440  }
4441 
4442  if (Op0->getType()->isIntOrIntVectorTy(1))
4443  if (Instruction *Res = canonicalizeICmpBool(I, Builder))
4444  return Res;
4445 
4446  if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4447  return NewICmp;
4448 
4449  if (Instruction *Res = foldICmpWithConstant(I))
4450  return Res;
4451 
4452  if (Instruction *Res = foldICmpUsingKnownBits(I))
4453  return Res;
4454 
4455  // Test if the ICmpInst instruction is used exclusively by a select as
4456  // part of a minimum or maximum operation. If so, refrain from doing
4457  // any other folding. This helps out other analyses which understand
4458  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4459  // and CodeGen. And in this case, at least one of the comparison
4460  // operands has at least one user besides the compare (the select),
4461  // which would often largely negate the benefit of folding anyway.
4462  //
4463  // Do the same for the other patterns recognized by matchSelectPattern.
4464  if (I.hasOneUse())
4465  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4466  Value *A, *B;
4467  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4468  if (SPR.Flavor != SPF_UNKNOWN)
4469  return nullptr;
4470  }
4471 
4472  // Do this after checking for min/max to prevent infinite looping.
4473  if (Instruction *Res = foldICmpWithZero(I))
4474  return Res;
4475 
4476  // FIXME: We only do this after checking for min/max to prevent infinite
4477  // looping caused by a reverse canonicalization of these patterns for min/max.
4478  // FIXME: The organization of folds is a mess. These would naturally go into
4479  // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4480  // down here after the min/max restriction.
4481  ICmpInst::Predicate Pred = I.getPredicate();
4482  const APInt *C;
4483  if (match(Op1, m_APInt(C))) {
4484  // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4485  if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4486  Constant *Zero = Constant::getNullValue(Op0->getType());
4487  return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4488  }
4489 
4490  // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4491  if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4492  Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4493  return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4494  }
4495  }
4496 
4497  if (Instruction *Res = foldICmpInstWithConstant(I))
4498  return Res;
4499 
4500  if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4501  return Res;
4502 
4503  // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4504  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4505  if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4506  return NI;
4507  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4508  if (Instruction *NI = foldGEPICmp(GEP, Op0,
4510  return NI;
4511 
4512  // Try to optimize equality comparisons against alloca-based pointers.
4513  if (Op0->getType()->isPointerTy() && I.isEquality()) {
4514  assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
4515  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4516  if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4517  return New;
4518  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4519  if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4520  return New;
4521  }
4522 
4523  // Test to see if the operands of the icmp are casted versions of other
4524  // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4525  // now.
4526  if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4527  if (Op0->getType()->isPointerTy() &&
4528  (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4529  // We keep moving the cast from the left operand over to the right
4530  // operand, where it can often be eliminated completely.
4531  Op0 = CI->getOperand(0);
4532 
4533  // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4534  // so eliminate it as well.
4535  if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4536  Op1 = CI2->getOperand(0);
4537 
4538  // If Op1 is a constant, we can fold the cast into the constant.
4539  if (Op0->getType() != Op1->getType()) {
4540  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4541  Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4542  } else {
4543  // Otherwise, cast the RHS right before the icmp
4544  Op1 = Builder.CreateBitCast(Op1, Op0->getType());
4545  }
4546  }
4547  return new ICmpInst(I.getPredicate(), Op0, Op1);
4548  }
4549  }
4550 
4551  if (isa<CastInst>(Op0)) {
4552  // Handle the special case of: icmp (cast bool to X), <cst>
4553  // This comes up when you have code like
4554  // int X = A < B;
4555  // if (X) ...
4556  // For generality, we handle any zero-extension of any operand comparison
4557  // with a constant or another cast from the same type.
4558  if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4559  if (Instruction *R = foldICmpWithCastAndCast(I))
4560  return R;
4561  }
4562 
4563  if (Instruction *Res = foldICmpBinOp(I))
4564  return Res;
4565 
4566  if (Instruction *Res = foldICmpWithMinMax(I))
4567  return Res;
4568 
4569  {
4570  Value *A, *B;
4571  // Transform (A & ~B) == 0 --> (A & B) != 0
4572  // and (A & ~B) != 0 --> (A & B) == 0
4573  // if A is a power of 2.
4574  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4575  match(Op1, m_Zero()) &&
4576  isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
4577  return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
4578  Op1);
4579 
4580  // ~X < ~Y --> Y < X
4581  // ~X < C --> X > ~C
4582  if (match(Op0, m_Not(m_Value(A)))) {
4583  if (match(Op1, m_Not(m_Value(B))))
4584  return new ICmpInst(I.getPredicate(), B, A);
4585 
4586  const APInt *C;
4587  if (match(Op1, m_APInt(C)))
4588  return new ICmpInst(I.getSwappedPredicate(), A,
4589  ConstantInt::get(Op1->getType(), ~(*C)));
4590  }
4591 
4592  Instruction *AddI = nullptr;
4593  if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4594  m_Instruction(AddI))) &&
4595  isa<IntegerType>(A->getType())) {
4596  Value *Result;
4597  Constant *Overflow;
4598  if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4599  Overflow)) {
4600  replaceInstUsesWith(*AddI, Result);
4601  return replaceInstUsesWith(I, Overflow);
4602  }
4603  }
4604 
4605  // (zext a) * (zext b) --> llvm.umul.with.overflow.
4606  if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4607  if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4608  return R;
4609  }
4610  if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4611  if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4612  return R;
4613  }
4614  }
4615 
4616  if (Instruction *Res = foldICmpEquality(I))
4617  return Res;
4618 
4619  // The 'cmpxchg' instruction returns an aggregate containing the old value and
4620  // an i1 which indicates whether or not we successfully did the swap.
4621  //
4622  // Replace comparisons between the old value and the expected value with the
4623  // indicator that 'cmpxchg' returns.
4624  //
4625  // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4626  // spuriously fail. In those cases, the old value may equal the expected
4627  // value but it is possible for the swap to not occur.
4628  if (I.getPredicate() == ICmpInst::ICMP_EQ)
4629  if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4630  if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4631  if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4632  !ACXI->isWeak())
4633  return ExtractValueInst::Create(ACXI, 1);
4634 
4635  {
4636  Value *X; ConstantInt *Cst;
4637  // icmp X+Cst, X
4638  if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4639  return foldICmpAddOpConst(X, Cst, I.getPredicate());
4640 
4641  // icmp X, X+Cst
4642  if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4643  return foldICmpAddOpConst(X, Cst, I.getSwappedPredicate());
4644  }
4645  return Changed ? &I : nullptr;
4646 }
4647 
4648 /// Fold fcmp ([us]itofp x, cst) if possible.
4649 Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4650  Constant *RHSC) {
4651  if (!isa<ConstantFP>(RHSC)) return nullptr;
4652  const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4653 
4654  // Get the width of the mantissa. We don't want to hack on conversions that
4655  // might lose information from the integer, e.g. "i64 -> float"
4656  int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4657  if (MantissaWidth == -1) return nullptr; // Unknown.
4658 
4659  IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4660 
4661  bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4662 
4663  if (I.isEquality()) {
4665  bool IsExact = false;
4666  APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4667  RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4668 
4669  // If the floating point constant isn't an integer value, we know if we will
4670  // ever compare equal / not equal to it.
4671  if (!IsExact) {
4672  // TODO: Can never be -0.0 and other non-representable values
4673  APFloat RHSRoundInt(RHS);
4675  if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4676  if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4677  return replaceInstUsesWith(I, Builder.getFalse());
4678 
4680  return replaceInstUsesWith(I, Builder.getTrue());
4681  }
4682  }
4683 
4684  // TODO: If the constant is exactly representable, is it always OK to do
4685  // equality compares as integer?
4686  }
4687 
4688  // Check to see that the input is converted from an integer type that is small
4689  // enough that preserves all bits. TODO: check here for "known" sign bits.
4690  // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4691  unsigned InputSize = IntTy->getScalarSizeInBits();
4692 
4693  // Following test does NOT adjust InputSize downwards for signed inputs,
4694  // because the most negative value still requires all the mantissa bits
4695  // to distinguish it from one less than that value.
4696  if ((int)InputSize > MantissaWidth) {
4697  // Conversion would lose accuracy. Check if loss can impact comparison.
4698  int Exp = ilogb(RHS);
4699  if (Exp == APFloat::IEK_Inf) {
4700  int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4701  if (MaxExponent < (int)InputSize - !LHSUnsigned)
4702  // Conversion could create infinity.
4703  return nullptr;
4704  } else {
4705  // Note that if RHS is zero or NaN, then Exp is negative
4706  // and first condition is trivially false.
4707  if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4708  // Conversion could affect comparison.
4709  return nullptr;
4710  }
4711  }
4712 
4713  // Otherwise, we can potentially simplify the comparison. We know that it
4714  // will always come through as an integer value and we know the constant is
4715  // not a NAN (it would have been previously simplified).
4716  assert(!RHS.isNaN() && "NaN comparison not already folded!");
4717 
4718  ICmpInst::Predicate Pred;
4719  switch (I.getPredicate()) {
4720  default: llvm_unreachable("Unexpected predicate!");
4721  case FCmpInst::FCMP_UEQ:
4722  case FCmpInst::FCMP_OEQ:
4723  Pred = ICmpInst::ICMP_EQ;
4724  break;
4725  case FCmpInst::FCMP_UGT:
4726  case FCmpInst::FCMP_OGT:
4727  Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4728  break;
4729  case FCmpInst::FCMP_UGE:
4730  case FCmpInst::FCMP_OGE:
4731  Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4732  break;
4733  case FCmpInst::FCMP_ULT:
4734  case FCmpInst::FCMP_OLT:
4735  Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4736  break;
4737  case FCmpInst::FCMP_ULE:
4738  case FCmpInst::FCMP_OLE:
4739  Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4740  break;
4741  case FCmpInst::FCMP_UNE:
4742  case FCmpInst::FCMP_ONE:
4743  Pred = ICmpInst::ICMP_NE;
4744  break;
4745  case FCmpInst::FCMP_ORD:
4746  return replaceInstUsesWith(I, Builder.getTrue());
4747  case FCmpInst::FCMP_UNO:
4748  return replaceInstUsesWith(I, Builder.getFalse());
4749  }
4750 
4751  // Now we know that the APFloat is a normal number, zero or inf.
4752 
4753  // See if the FP constant is too large for the integer. For example,
4754  // comparing an i8 to 300.0.
4755  unsigned IntWidth = IntTy->getScalarSizeInBits();
4756 
4757  if (!LHSUnsigned) {
4758  // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4759  // and large values.
4760  APFloat SMax(RHS.getSemantics());
4761  SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4763  if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4764  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4765  Pred == ICmpInst::ICMP_SLE)
4766  return replaceInstUsesWith(I, Builder.getTrue());
4767  return replaceInstUsesWith(I, Builder.getFalse());
4768  }
4769  } else {
4770  // If the RHS value is > UnsignedMax, fold the comparison. This handles
4771  // +INF and large values.
4772  APFloat UMax(RHS.getSemantics());
4773  UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4775  if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4776  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4777  Pred == ICmpInst::ICMP_ULE)
4778  return replaceInstUsesWith(I, Builder.getTrue());
4779  return replaceInstUsesWith(I, Builder.getFalse());
4780  }
4781  }
4782 
4783  if (!LHSUnsigned) {
4784  // See if the RHS value is < SignedMin.
4785  APFloat SMin(RHS.getSemantics());
4786  SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4788  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4789  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4790  Pred == ICmpInst::ICMP_SGE)
4791  return replaceInstUsesWith(I, Builder.getTrue());
4792  return replaceInstUsesWith(I, Builder.getFalse());
4793  }
4794  } else {
4795  // See if the RHS value is < UnsignedMin.
4796  APFloat SMin(RHS.getSemantics());
4797  SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4799  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4800  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4801  Pred == ICmpInst::ICMP_UGE)
4802  return replaceInstUsesWith(I, Builder.getTrue());
4803  return replaceInstUsesWith(I, Builder.getFalse());
4804  }
4805  }
4806 
4807  // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4808  // [0, UMAX], but it may still be fractional. See if it is fractional by
4809  // casting the FP value to the integer value and back, checking for equality.
4810  // Don't do this for zero, because -0.0 is not fractional.
4811  Constant *RHSInt = LHSUnsigned
4812  ? ConstantExpr::getFPToUI(RHSC, IntTy)
4813  : ConstantExpr::getFPToSI(RHSC, IntTy);
4814  if (!RHS.isZero()) {
4815  bool Equal = LHSUnsigned
4816  ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4817  : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4818  if (!Equal) {
4819  // If we had a comparison against a fractional value, we have to adjust
4820  // the compare predicate and sometimes the value. RHSC is rounded towards
4821  // zero at this point.
4822  switch (Pred) {
4823  default: llvm_unreachable("Unexpected integer comparison!");
4824  case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4825  return replaceInstUsesWith(I, Builder.getTrue());
4826  case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4827  return replaceInstUsesWith(I, Builder.getFalse());
4828  case ICmpInst::ICMP_ULE:
4829  // (float)int <= 4.4 --> int <= 4
4830  // (float)int <= -4.4 --> false
4831  if (RHS.isNegative())
4832  return replaceInstUsesWith(I, Builder.getFalse());
4833  break;
4834  case ICmpInst::ICMP_SLE:
4835  // (float)int <= 4.4 --> int <= 4
4836  // (float)int <= -4.4 --> int < -4
4837  if (RHS.isNegative())
4838  Pred = ICmpInst::ICMP_SLT;
4839  break;
4840  case ICmpInst::ICMP_ULT:
4841  // (float)int < -4.4 --> false
4842  // (float)int < 4.4 --> int <= 4
4843  if (RHS.isNegative())
4844  return replaceInstUsesWith(I, Builder.getFalse());
4845  Pred = ICmpInst::ICMP_ULE;
4846  break;
4847  case ICmpInst::ICMP_SLT:
4848  // (float)int < -4.4 --> int < -4
4849  // (float)int < 4.4 --> int <= 4
4850  if (!RHS.isNegative())
4851  Pred = ICmpInst::ICMP_SLE;
4852  break;
4853  case ICmpInst::ICMP_UGT:
4854  // (float)int > 4.4 --> int > 4
4855  // (float)int > -4.4 --> true
4856  if (RHS.isNegative())
4857  return replaceInstUsesWith(I, Builder.getTrue());
4858  break;
4859  case ICmpInst::ICMP_SGT:
4860  // (float)int > 4.4 --> int > 4
4861  // (float)int > -4.4 --> int >= -4
4862  if (RHS.isNegative())
4863  Pred = ICmpInst::ICMP_SGE;
4864  break;
4865  case ICmpInst::ICMP_UGE:
4866  // (float)int >= -4.4 --> true
4867  // (float)int >= 4.4 --> int > 4
4868  if (RHS.isNegative())
4869  return replaceInstUsesWith(I, Builder.getTrue());
4870  Pred = ICmpInst::ICMP_UGT;
4871  break;
4872  case ICmpInst::ICMP_SGE:
4873  // (float)int >= -4.4 --> int >= -4
4874  // (float)int >= 4.4 --> int > 4
4875  if (!RHS.isNegative())
4876  Pred = ICmpInst::ICMP_SGT;
4877  break;
4878  }
4879  }
4880  }
4881 
4882  // Lower this FP comparison into an appropriate integer version of the
4883  // comparison.
4884  return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4885 }
4886 
4888  bool Changed = false;
4889 
4890  /// Orders the operands of the compare so that they are listed from most
4891  /// complex to least complex. This puts constants before unary operators,
4892  /// before binary operators.
4893  if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4894  I.swapOperands();
4895  Changed = true;
4896  }
4897 
4898  const CmpInst::Predicate Pred = I.getPredicate();
4899  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4900  if (Value *V = SimplifyFCmpInst(Pred, Op0, Op1, I.getFastMathFlags(),
4901  SQ.getWithInstruction(&I)))
4902  return replaceInstUsesWith(I, V);
4903 
4904  // Simplify 'fcmp pred X, X'
4905  if (Op0 == Op1) {
4906  switch (Pred) {
4907  default: break;
4908  case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4909  case FCmpInst::FCMP_ULT: // True if unordered or less than
4910  case FCmpInst::FCMP_UGT: // True if unordered or greater than
4911  case FCmpInst::FCMP_UNE: // True if unordered or not equal
4912  // Canonicalize these to be 'fcmp uno %X, 0.0'.
4915  return &I;
4916 
4917  case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4918  case FCmpInst::FCMP_OEQ: // True if ordered and equal
4919  case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4920  case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4921  // Canonicalize these to be 'fcmp ord %X, 0.0'.
4924  return &I;
4925  }
4926  }
4927 
4928  // If we're just checking for a NaN (ORD/UNO) and have a non-NaN operand,
4929  // then canonicalize the operand to 0.0.
4930  if (Pred == CmpInst::FCMP_ORD || Pred == CmpInst::FCMP_UNO) {
4931  if (!match(Op0, m_Zero()) && isKnownNeverNaN(Op0)) {
4933  return &I;
4934  }
4935  if (!match(Op1, m_Zero()) && isKnownNeverNaN(Op1)) {
4937  return &I;
4938  }
4939  }
4940 
4941  // Test if the FCmpInst instruction is used exclusively by a select as
4942  // part of a minimum or maximum operation. If so, refrain from doing
4943  // any other folding. This helps out other analyses which understand
4944  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4945  // and CodeGen. And in this case, at least one of the comparison
4946  // operands has at least one user besides the compare (the select),
4947  // which would often largely negate the benefit of folding anyway.
4948  if (I.hasOneUse())
4949  if (SelectInst *SI = dyn_cast<SelectInst>(I.user_back())) {
4950  Value *A, *B;
4951  SelectPatternResult SPR = matchSelectPattern(SI, A, B);
4952  if (SPR.Flavor != SPF_UNKNOWN)
4953  return nullptr;
4954  }
4955 
4956  // Handle fcmp with constant RHS
4957  if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4958  if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4959  switch (LHSI->getOpcode()) {
4960  case Instruction::FPExt: {
4961  // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
4962  FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
4963  ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
4964  if (!RHSF)
4965  break;
4966 
4967  const fltSemantics *Sem;
4968  // FIXME: This shouldn't be here.
4969  if (LHSExt->getSrcTy()->isHalfTy())
4970  Sem = &APFloat::IEEEhalf();
4971  else if (LHSExt->getSrcTy()->isFloatTy())
4972  Sem = &APFloat::IEEEsingle();
4973  else if (LHSExt->getSrcTy()->isDoubleTy())
4974  Sem = &APFloat::IEEEdouble();
4975  else if (LHSExt->getSrcTy()->isFP128Ty())
4976  Sem = &APFloat::IEEEquad();
4977  else if (LHSExt->getSrcTy()->isX86_FP80Ty())
4978  Sem = &APFloat::x87DoubleExtended();
4979  else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
4980  Sem = &APFloat::PPCDoubleDouble();
4981  else
4982  break;
4983 
4984  bool Lossy;
4985  APFloat F = RHSF->getValueAPF();
4986  F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
4987 
4988  // Avoid lossy conversions and denormals. Zero is a special case
4989  // that's OK to convert.
4990  APFloat Fabs = F;
4991  Fabs.clearSign();
4992  if (!Lossy &&
4993  ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
4994  APFloat::cmpLessThan) || Fabs.isZero()))
4995 
4996  return new FCmpInst(Pred, LHSExt->getOperand(0),
4997  ConstantFP::get(RHSC->getContext(), F));
4998  break;
4999  }
5000  case Instruction::PHI:
5001  // Only fold fcmp into the PHI if the phi and fcmp are in the same
5002  // block. If in the same block, we're encouraging jump threading. If
5003  // not, we are just pessimizing the code by making an i1 phi.
5004  if (LHSI->getParent() == I.getParent())
5005  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
5006  return NV;
5007  break;
5008  case Instruction::SIToFP:
5009  case Instruction::UIToFP:
5010  if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
5011  return NV;
5012  break;
5013  case Instruction::FSub: {
5014  // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
5015  Value *Op;
5016  if (match(LHSI, m_FNeg(m_Value(Op))))
5017  return new FCmpInst(I.getSwappedPredicate(), Op,
5018  ConstantExpr::getFNeg(RHSC));
5019  break;
5020  }
5021  case Instruction::Load:
5022  if (GetElementPtrInst *GEP =
5023  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
5024  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
5025  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
5026  !cast<LoadInst>(LHSI)->isVolatile())
5027  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
5028  return Res;
5029  }
5030  break;
5031  case Instruction::Call: {
5032  if (!RHSC->isNullValue())
5033  break;
5034 
5035  CallInst *CI = cast<CallInst>(LHSI);
5036  Intrinsic::ID IID = getIntrinsicForCallSite(CI, &TLI);
5037  if (IID != Intrinsic::fabs)
5038  break;
5039 
5040  // Various optimization for fabs compared with zero.
5041  switch (Pred) {
5042  default:
5043  break;
5044  // fabs(x) < 0 --> false
5045  case FCmpInst::FCMP_OLT:
5046  llvm_unreachable("handled by SimplifyFCmpInst");
5047  // fabs(x) > 0 --> x != 0
5048  case FCmpInst::FCMP_OGT:
5049  return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC);
5050  // fabs(x) <= 0 --> x == 0
5051  case FCmpInst::FCMP_OLE:
5052  return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC);
5053  // fabs(x) >= 0 --> !isnan(x)
5054  case FCmpInst::FCMP_OGE:
5055  return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC);
5056  // fabs(x) == 0 --> x == 0
5057  // fabs(x) != 0 --> x != 0
5058  case FCmpInst::FCMP_OEQ:
5059  case FCmpInst::FCMP_UEQ:
5060  case FCmpInst::FCMP_ONE:
5061  case FCmpInst::FCMP_UNE:
5062  return new FCmpInst(Pred, CI->getArgOperand(0), RHSC);
5063  }
5064  }
5065  }
5066  }
5067 
5068  // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
5069  Value *X, *Y;
5070  if (match(Op0,