LLVM  6.0.0svn
InstCombineCompares.cpp
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1 //===- InstCombineCompares.cpp --------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the visitICmp and visitFCmp functions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "InstCombineInternal.h"
15 #include "llvm/ADT/APSInt.h"
16 #include "llvm/ADT/SetVector.h"
17 #include "llvm/ADT/Statistic.h"
23 #include "llvm/IR/ConstantRange.h"
24 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/PatternMatch.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/KnownBits.h"
30 
31 using namespace llvm;
32 using namespace PatternMatch;
33 
34 #define DEBUG_TYPE "instcombine"
35 
36 // How many times is a select replaced by one of its operands?
37 STATISTIC(NumSel, "Number of select opts");
38 
39 
41  return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx));
42 }
43 
44 static bool hasAddOverflow(ConstantInt *Result,
45  ConstantInt *In1, ConstantInt *In2,
46  bool IsSigned) {
47  if (!IsSigned)
48  return Result->getValue().ult(In1->getValue());
49 
50  if (In2->isNegative())
51  return Result->getValue().sgt(In1->getValue());
52  return Result->getValue().slt(In1->getValue());
53 }
54 
55 /// Compute Result = In1+In2, returning true if the result overflowed for this
56 /// type.
57 static bool addWithOverflow(Constant *&Result, Constant *In1,
58  Constant *In2, bool IsSigned = false) {
59  Result = ConstantExpr::getAdd(In1, In2);
60 
61  if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
62  for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
64  if (hasAddOverflow(extractElement(Result, Idx),
65  extractElement(In1, Idx),
66  extractElement(In2, Idx),
67  IsSigned))
68  return true;
69  }
70  return false;
71  }
72 
73  return hasAddOverflow(cast<ConstantInt>(Result),
74  cast<ConstantInt>(In1), cast<ConstantInt>(In2),
75  IsSigned);
76 }
77 
78 static bool hasSubOverflow(ConstantInt *Result,
79  ConstantInt *In1, ConstantInt *In2,
80  bool IsSigned) {
81  if (!IsSigned)
82  return Result->getValue().ugt(In1->getValue());
83 
84  if (In2->isNegative())
85  return Result->getValue().slt(In1->getValue());
86 
87  return Result->getValue().sgt(In1->getValue());
88 }
89 
90 /// Compute Result = In1-In2, returning true if the result overflowed for this
91 /// type.
92 static bool subWithOverflow(Constant *&Result, Constant *In1,
93  Constant *In2, bool IsSigned = false) {
94  Result = ConstantExpr::getSub(In1, In2);
95 
96  if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
97  for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
99  if (hasSubOverflow(extractElement(Result, Idx),
100  extractElement(In1, Idx),
101  extractElement(In2, Idx),
102  IsSigned))
103  return true;
104  }
105  return false;
106  }
107 
108  return hasSubOverflow(cast<ConstantInt>(Result),
109  cast<ConstantInt>(In1), cast<ConstantInt>(In2),
110  IsSigned);
111 }
112 
113 /// Given an icmp instruction, return true if any use of this comparison is a
114 /// branch on sign bit comparison.
115 static bool hasBranchUse(ICmpInst &I) {
116  for (auto *U : I.users())
117  if (isa<BranchInst>(U))
118  return true;
119  return false;
120 }
121 
122 /// Given an exploded icmp instruction, return true if the comparison only
123 /// checks the sign bit. If it only checks the sign bit, set TrueIfSigned if the
124 /// result of the comparison is true when the input value is signed.
125 static bool isSignBitCheck(ICmpInst::Predicate Pred, const APInt &RHS,
126  bool &TrueIfSigned) {
127  switch (Pred) {
128  case ICmpInst::ICMP_SLT: // True if LHS s< 0
129  TrueIfSigned = true;
130  return RHS.isNullValue();
131  case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
132  TrueIfSigned = true;
133  return RHS.isAllOnesValue();
134  case ICmpInst::ICMP_SGT: // True if LHS s> -1
135  TrueIfSigned = false;
136  return RHS.isAllOnesValue();
137  case ICmpInst::ICMP_UGT:
138  // True if LHS u> RHS and RHS == high-bit-mask - 1
139  TrueIfSigned = true;
140  return RHS.isMaxSignedValue();
141  case ICmpInst::ICMP_UGE:
142  // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
143  TrueIfSigned = true;
144  return RHS.isSignMask();
145  default:
146  return false;
147  }
148 }
149 
150 /// Returns true if the exploded icmp can be expressed as a signed comparison
151 /// to zero and updates the predicate accordingly.
152 /// The signedness of the comparison is preserved.
153 /// TODO: Refactor with decomposeBitTestICmp()?
154 static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C) {
155  if (!ICmpInst::isSigned(Pred))
156  return false;
157 
158  if (C.isNullValue())
159  return ICmpInst::isRelational(Pred);
160 
161  if (C.isOneValue()) {
162  if (Pred == ICmpInst::ICMP_SLT) {
163  Pred = ICmpInst::ICMP_SLE;
164  return true;
165  }
166  } else if (C.isAllOnesValue()) {
167  if (Pred == ICmpInst::ICMP_SGT) {
168  Pred = ICmpInst::ICMP_SGE;
169  return true;
170  }
171  }
172 
173  return false;
174 }
175 
176 /// Given a signed integer type and a set of known zero and one bits, compute
177 /// the maximum and minimum values that could have the specified known zero and
178 /// known one bits, returning them in Min/Max.
179 /// TODO: Move to method on KnownBits struct?
181  APInt &Min, APInt &Max) {
182  assert(Known.getBitWidth() == Min.getBitWidth() &&
183  Known.getBitWidth() == Max.getBitWidth() &&
184  "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
185  APInt UnknownBits = ~(Known.Zero|Known.One);
186 
187  // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
188  // bit if it is unknown.
189  Min = Known.One;
190  Max = Known.One|UnknownBits;
191 
192  if (UnknownBits.isNegative()) { // Sign bit is unknown
193  Min.setSignBit();
194  Max.clearSignBit();
195  }
196 }
197 
198 /// Given an unsigned integer type and a set of known zero and one bits, compute
199 /// the maximum and minimum values that could have the specified known zero and
200 /// known one bits, returning them in Min/Max.
201 /// TODO: Move to method on KnownBits struct?
203  APInt &Min, APInt &Max) {
204  assert(Known.getBitWidth() == Min.getBitWidth() &&
205  Known.getBitWidth() == Max.getBitWidth() &&
206  "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
207  APInt UnknownBits = ~(Known.Zero|Known.One);
208 
209  // The minimum value is when the unknown bits are all zeros.
210  Min = Known.One;
211  // The maximum value is when the unknown bits are all ones.
212  Max = Known.One|UnknownBits;
213 }
214 
215 /// This is called when we see this pattern:
216 /// cmp pred (load (gep GV, ...)), cmpcst
217 /// where GV is a global variable with a constant initializer. Try to simplify
218 /// this into some simple computation that does not need the load. For example
219 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
220 ///
221 /// If AndCst is non-null, then the loaded value is masked with that constant
222 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
223 Instruction *InstCombiner::foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
224  GlobalVariable *GV,
225  CmpInst &ICI,
226  ConstantInt *AndCst) {
227  Constant *Init = GV->getInitializer();
228  if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
229  return nullptr;
230 
231  uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
232  // Don't blow up on huge arrays.
233  if (ArrayElementCount > MaxArraySizeForCombine)
234  return nullptr;
235 
236  // There are many forms of this optimization we can handle, for now, just do
237  // the simple index into a single-dimensional array.
238  //
239  // Require: GEP GV, 0, i {{, constant indices}}
240  if (GEP->getNumOperands() < 3 ||
241  !isa<ConstantInt>(GEP->getOperand(1)) ||
242  !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
243  isa<Constant>(GEP->getOperand(2)))
244  return nullptr;
245 
246  // Check that indices after the variable are constants and in-range for the
247  // type they index. Collect the indices. This is typically for arrays of
248  // structs.
249  SmallVector<unsigned, 4> LaterIndices;
250 
251  Type *EltTy = Init->getType()->getArrayElementType();
252  for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
253  ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
254  if (!Idx) return nullptr; // Variable index.
255 
256  uint64_t IdxVal = Idx->getZExtValue();
257  if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
258 
259  if (StructType *STy = dyn_cast<StructType>(EltTy))
260  EltTy = STy->getElementType(IdxVal);
261  else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
262  if (IdxVal >= ATy->getNumElements()) return nullptr;
263  EltTy = ATy->getElementType();
264  } else {
265  return nullptr; // Unknown type.
266  }
267 
268  LaterIndices.push_back(IdxVal);
269  }
270 
271  enum { Overdefined = -3, Undefined = -2 };
272 
273  // Variables for our state machines.
274 
275  // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
276  // "i == 47 | i == 87", where 47 is the first index the condition is true for,
277  // and 87 is the second (and last) index. FirstTrueElement is -2 when
278  // undefined, otherwise set to the first true element. SecondTrueElement is
279  // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
280  int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
281 
282  // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
283  // form "i != 47 & i != 87". Same state transitions as for true elements.
284  int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
285 
286  /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
287  /// define a state machine that triggers for ranges of values that the index
288  /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
289  /// This is -2 when undefined, -3 when overdefined, and otherwise the last
290  /// index in the range (inclusive). We use -2 for undefined here because we
291  /// use relative comparisons and don't want 0-1 to match -1.
292  int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
293 
294  // MagicBitvector - This is a magic bitvector where we set a bit if the
295  // comparison is true for element 'i'. If there are 64 elements or less in
296  // the array, this will fully represent all the comparison results.
297  uint64_t MagicBitvector = 0;
298 
299  // Scan the array and see if one of our patterns matches.
300  Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
301  for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
302  Constant *Elt = Init->getAggregateElement(i);
303  if (!Elt) return nullptr;
304 
305  // If this is indexing an array of structures, get the structure element.
306  if (!LaterIndices.empty())
307  Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
308 
309  // If the element is masked, handle it.
310  if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
311 
312  // Find out if the comparison would be true or false for the i'th element.
314  CompareRHS, DL, &TLI);
315  // If the result is undef for this element, ignore it.
316  if (isa<UndefValue>(C)) {
317  // Extend range state machines to cover this element in case there is an
318  // undef in the middle of the range.
319  if (TrueRangeEnd == (int)i-1)
320  TrueRangeEnd = i;
321  if (FalseRangeEnd == (int)i-1)
322  FalseRangeEnd = i;
323  continue;
324  }
325 
326  // If we can't compute the result for any of the elements, we have to give
327  // up evaluating the entire conditional.
328  if (!isa<ConstantInt>(C)) return nullptr;
329 
330  // Otherwise, we know if the comparison is true or false for this element,
331  // update our state machines.
332  bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
333 
334  // State machine for single/double/range index comparison.
335  if (IsTrueForElt) {
336  // Update the TrueElement state machine.
337  if (FirstTrueElement == Undefined)
338  FirstTrueElement = TrueRangeEnd = i; // First true element.
339  else {
340  // Update double-compare state machine.
341  if (SecondTrueElement == Undefined)
342  SecondTrueElement = i;
343  else
344  SecondTrueElement = Overdefined;
345 
346  // Update range state machine.
347  if (TrueRangeEnd == (int)i-1)
348  TrueRangeEnd = i;
349  else
350  TrueRangeEnd = Overdefined;
351  }
352  } else {
353  // Update the FalseElement state machine.
354  if (FirstFalseElement == Undefined)
355  FirstFalseElement = FalseRangeEnd = i; // First false element.
356  else {
357  // Update double-compare state machine.
358  if (SecondFalseElement == Undefined)
359  SecondFalseElement = i;
360  else
361  SecondFalseElement = Overdefined;
362 
363  // Update range state machine.
364  if (FalseRangeEnd == (int)i-1)
365  FalseRangeEnd = i;
366  else
367  FalseRangeEnd = Overdefined;
368  }
369  }
370 
371  // If this element is in range, update our magic bitvector.
372  if (i < 64 && IsTrueForElt)
373  MagicBitvector |= 1ULL << i;
374 
375  // If all of our states become overdefined, bail out early. Since the
376  // predicate is expensive, only check it every 8 elements. This is only
377  // really useful for really huge arrays.
378  if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
379  SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
380  FalseRangeEnd == Overdefined)
381  return nullptr;
382  }
383 
384  // Now that we've scanned the entire array, emit our new comparison(s). We
385  // order the state machines in complexity of the generated code.
386  Value *Idx = GEP->getOperand(2);
387 
388  // If the index is larger than the pointer size of the target, truncate the
389  // index down like the GEP would do implicitly. We don't have to do this for
390  // an inbounds GEP because the index can't be out of range.
391  if (!GEP->isInBounds()) {
392  Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
393  unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
394  if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
395  Idx = Builder.CreateTrunc(Idx, IntPtrTy);
396  }
397 
398  // If the comparison is only true for one or two elements, emit direct
399  // comparisons.
400  if (SecondTrueElement != Overdefined) {
401  // None true -> false.
402  if (FirstTrueElement == Undefined)
403  return replaceInstUsesWith(ICI, Builder.getFalse());
404 
405  Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
406 
407  // True for one element -> 'i == 47'.
408  if (SecondTrueElement == Undefined)
409  return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
410 
411  // True for two elements -> 'i == 47 | i == 72'.
412  Value *C1 = Builder.CreateICmpEQ(Idx, FirstTrueIdx);
413  Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
414  Value *C2 = Builder.CreateICmpEQ(Idx, SecondTrueIdx);
415  return BinaryOperator::CreateOr(C1, C2);
416  }
417 
418  // If the comparison is only false for one or two elements, emit direct
419  // comparisons.
420  if (SecondFalseElement != Overdefined) {
421  // None false -> true.
422  if (FirstFalseElement == Undefined)
423  return replaceInstUsesWith(ICI, Builder.getTrue());
424 
425  Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
426 
427  // False for one element -> 'i != 47'.
428  if (SecondFalseElement == Undefined)
429  return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
430 
431  // False for two elements -> 'i != 47 & i != 72'.
432  Value *C1 = Builder.CreateICmpNE(Idx, FirstFalseIdx);
433  Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
434  Value *C2 = Builder.CreateICmpNE(Idx, SecondFalseIdx);
435  return BinaryOperator::CreateAnd(C1, C2);
436  }
437 
438  // If the comparison can be replaced with a range comparison for the elements
439  // where it is true, emit the range check.
440  if (TrueRangeEnd != Overdefined) {
441  assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
442 
443  // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
444  if (FirstTrueElement) {
445  Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
446  Idx = Builder.CreateAdd(Idx, Offs);
447  }
448 
449  Value *End = ConstantInt::get(Idx->getType(),
450  TrueRangeEnd-FirstTrueElement+1);
451  return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
452  }
453 
454  // False range check.
455  if (FalseRangeEnd != Overdefined) {
456  assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
457  // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
458  if (FirstFalseElement) {
459  Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
460  Idx = Builder.CreateAdd(Idx, Offs);
461  }
462 
463  Value *End = ConstantInt::get(Idx->getType(),
464  FalseRangeEnd-FirstFalseElement);
465  return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
466  }
467 
468  // If a magic bitvector captures the entire comparison state
469  // of this load, replace it with computation that does:
470  // ((magic_cst >> i) & 1) != 0
471  {
472  Type *Ty = nullptr;
473 
474  // Look for an appropriate type:
475  // - The type of Idx if the magic fits
476  // - The smallest fitting legal type if we have a DataLayout
477  // - Default to i32
478  if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
479  Ty = Idx->getType();
480  else
481  Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
482 
483  if (Ty) {
484  Value *V = Builder.CreateIntCast(Idx, Ty, false);
485  V = Builder.CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
486  V = Builder.CreateAnd(ConstantInt::get(Ty, 1), V);
487  return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
488  }
489  }
490 
491  return nullptr;
492 }
493 
494 /// Return a value that can be used to compare the *offset* implied by a GEP to
495 /// zero. For example, if we have &A[i], we want to return 'i' for
496 /// "icmp ne i, 0". Note that, in general, indices can be complex, and scales
497 /// are involved. The above expression would also be legal to codegen as
498 /// "icmp ne (i*4), 0" (assuming A is a pointer to i32).
499 /// This latter form is less amenable to optimization though, and we are allowed
500 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
501 ///
502 /// If we can't emit an optimized form for this expression, this returns null.
503 ///
505  const DataLayout &DL) {
507 
508  // Check to see if this gep only has a single variable index. If so, and if
509  // any constant indices are a multiple of its scale, then we can compute this
510  // in terms of the scale of the variable index. For example, if the GEP
511  // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
512  // because the expression will cross zero at the same point.
513  unsigned i, e = GEP->getNumOperands();
514  int64_t Offset = 0;
515  for (i = 1; i != e; ++i, ++GTI) {
516  if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
517  // Compute the aggregate offset of constant indices.
518  if (CI->isZero()) continue;
519 
520  // Handle a struct index, which adds its field offset to the pointer.
521  if (StructType *STy = GTI.getStructTypeOrNull()) {
522  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
523  } else {
524  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
525  Offset += Size*CI->getSExtValue();
526  }
527  } else {
528  // Found our variable index.
529  break;
530  }
531  }
532 
533  // If there are no variable indices, we must have a constant offset, just
534  // evaluate it the general way.
535  if (i == e) return nullptr;
536 
537  Value *VariableIdx = GEP->getOperand(i);
538  // Determine the scale factor of the variable element. For example, this is
539  // 4 if the variable index is into an array of i32.
540  uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
541 
542  // Verify that there are no other variable indices. If so, emit the hard way.
543  for (++i, ++GTI; i != e; ++i, ++GTI) {
544  ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
545  if (!CI) return nullptr;
546 
547  // Compute the aggregate offset of constant indices.
548  if (CI->isZero()) continue;
549 
550  // Handle a struct index, which adds its field offset to the pointer.
551  if (StructType *STy = GTI.getStructTypeOrNull()) {
552  Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
553  } else {
554  uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
555  Offset += Size*CI->getSExtValue();
556  }
557  }
558 
559  // Okay, we know we have a single variable index, which must be a
560  // pointer/array/vector index. If there is no offset, life is simple, return
561  // the index.
562  Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
563  unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
564  if (Offset == 0) {
565  // Cast to intptrty in case a truncation occurs. If an extension is needed,
566  // we don't need to bother extending: the extension won't affect where the
567  // computation crosses zero.
568  if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
569  VariableIdx = IC.Builder.CreateTrunc(VariableIdx, IntPtrTy);
570  }
571  return VariableIdx;
572  }
573 
574  // Otherwise, there is an index. The computation we will do will be modulo
575  // the pointer size, so get it.
576  uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
577 
578  Offset &= PtrSizeMask;
579  VariableScale &= PtrSizeMask;
580 
581  // To do this transformation, any constant index must be a multiple of the
582  // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
583  // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
584  // multiple of the variable scale.
585  int64_t NewOffs = Offset / (int64_t)VariableScale;
586  if (Offset != NewOffs*(int64_t)VariableScale)
587  return nullptr;
588 
589  // Okay, we can do this evaluation. Start by converting the index to intptr.
590  if (VariableIdx->getType() != IntPtrTy)
591  VariableIdx = IC.Builder.CreateIntCast(VariableIdx, IntPtrTy,
592  true /*Signed*/);
593  Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
594  return IC.Builder.CreateAdd(VariableIdx, OffsetVal, "offset");
595 }
596 
597 /// Returns true if we can rewrite Start as a GEP with pointer Base
598 /// and some integer offset. The nodes that need to be re-written
599 /// for this transformation will be added to Explored.
600 static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
601  const DataLayout &DL,
602  SetVector<Value *> &Explored) {
603  SmallVector<Value *, 16> WorkList(1, Start);
604  Explored.insert(Base);
605 
606  // The following traversal gives us an order which can be used
607  // when doing the final transformation. Since in the final
608  // transformation we create the PHI replacement instructions first,
609  // we don't have to get them in any particular order.
610  //
611  // However, for other instructions we will have to traverse the
612  // operands of an instruction first, which means that we have to
613  // do a post-order traversal.
614  while (!WorkList.empty()) {
616 
617  while (!WorkList.empty()) {
618  if (Explored.size() >= 100)
619  return false;
620 
621  Value *V = WorkList.back();
622 
623  if (Explored.count(V) != 0) {
624  WorkList.pop_back();
625  continue;
626  }
627 
628  if (!isa<IntToPtrInst>(V) && !isa<PtrToIntInst>(V) &&
629  !isa<GetElementPtrInst>(V) && !isa<PHINode>(V))
630  // We've found some value that we can't explore which is different from
631  // the base. Therefore we can't do this transformation.
632  return false;
633 
634  if (isa<IntToPtrInst>(V) || isa<PtrToIntInst>(V)) {
635  auto *CI = dyn_cast<CastInst>(V);
636  if (!CI->isNoopCast(DL))
637  return false;
638 
639  if (Explored.count(CI->getOperand(0)) == 0)
640  WorkList.push_back(CI->getOperand(0));
641  }
642 
643  if (auto *GEP = dyn_cast<GEPOperator>(V)) {
644  // We're limiting the GEP to having one index. This will preserve
645  // the original pointer type. We could handle more cases in the
646  // future.
647  if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
648  GEP->getType() != Start->getType())
649  return false;
650 
651  if (Explored.count(GEP->getOperand(0)) == 0)
652  WorkList.push_back(GEP->getOperand(0));
653  }
654 
655  if (WorkList.back() == V) {
656  WorkList.pop_back();
657  // We've finished visiting this node, mark it as such.
658  Explored.insert(V);
659  }
660 
661  if (auto *PN = dyn_cast<PHINode>(V)) {
662  // We cannot transform PHIs on unsplittable basic blocks.
663  if (isa<CatchSwitchInst>(PN->getParent()->getTerminator()))
664  return false;
665  Explored.insert(PN);
666  PHIs.insert(PN);
667  }
668  }
669 
670  // Explore the PHI nodes further.
671  for (auto *PN : PHIs)
672  for (Value *Op : PN->incoming_values())
673  if (Explored.count(Op) == 0)
674  WorkList.push_back(Op);
675  }
676 
677  // Make sure that we can do this. Since we can't insert GEPs in a basic
678  // block before a PHI node, we can't easily do this transformation if
679  // we have PHI node users of transformed instructions.
680  for (Value *Val : Explored) {
681  for (Value *Use : Val->uses()) {
682 
683  auto *PHI = dyn_cast<PHINode>(Use);
684  auto *Inst = dyn_cast<Instruction>(Val);
685 
686  if (Inst == Base || Inst == PHI || !Inst || !PHI ||
687  Explored.count(PHI) == 0)
688  continue;
689 
690  if (PHI->getParent() == Inst->getParent())
691  return false;
692  }
693  }
694  return true;
695 }
696 
697 // Sets the appropriate insert point on Builder where we can add
698 // a replacement Instruction for V (if that is possible).
699 static void setInsertionPoint(IRBuilder<> &Builder, Value *V,
700  bool Before = true) {
701  if (auto *PHI = dyn_cast<PHINode>(V)) {
702  Builder.SetInsertPoint(&*PHI->getParent()->getFirstInsertionPt());
703  return;
704  }
705  if (auto *I = dyn_cast<Instruction>(V)) {
706  if (!Before)
707  I = &*std::next(I->getIterator());
708  Builder.SetInsertPoint(I);
709  return;
710  }
711  if (auto *A = dyn_cast<Argument>(V)) {
712  // Set the insertion point in the entry block.
713  BasicBlock &Entry = A->getParent()->getEntryBlock();
714  Builder.SetInsertPoint(&*Entry.getFirstInsertionPt());
715  return;
716  }
717  // Otherwise, this is a constant and we don't need to set a new
718  // insertion point.
719  assert(isa<Constant>(V) && "Setting insertion point for unknown value!");
720 }
721 
722 /// Returns a re-written value of Start as an indexed GEP using Base as a
723 /// pointer.
725  const DataLayout &DL,
726  SetVector<Value *> &Explored) {
727  // Perform all the substitutions. This is a bit tricky because we can
728  // have cycles in our use-def chains.
729  // 1. Create the PHI nodes without any incoming values.
730  // 2. Create all the other values.
731  // 3. Add the edges for the PHI nodes.
732  // 4. Emit GEPs to get the original pointers.
733  // 5. Remove the original instructions.
734  Type *IndexType = IntegerType::get(
735  Base->getContext(), DL.getPointerTypeSizeInBits(Start->getType()));
736 
738  NewInsts[Base] = ConstantInt::getNullValue(IndexType);
739 
740  // Create the new PHI nodes, without adding any incoming values.
741  for (Value *Val : Explored) {
742  if (Val == Base)
743  continue;
744  // Create empty phi nodes. This avoids cyclic dependencies when creating
745  // the remaining instructions.
746  if (auto *PHI = dyn_cast<PHINode>(Val))
747  NewInsts[PHI] = PHINode::Create(IndexType, PHI->getNumIncomingValues(),
748  PHI->getName() + ".idx", PHI);
749  }
750  IRBuilder<> Builder(Base->getContext());
751 
752  // Create all the other instructions.
753  for (Value *Val : Explored) {
754 
755  if (NewInsts.find(Val) != NewInsts.end())
756  continue;
757 
758  if (auto *CI = dyn_cast<CastInst>(Val)) {
759  NewInsts[CI] = NewInsts[CI->getOperand(0)];
760  continue;
761  }
762  if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
763  Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)]
764  : GEP->getOperand(1);
765  setInsertionPoint(Builder, GEP);
766  // Indices might need to be sign extended. GEPs will magically do
767  // this, but we need to do it ourselves here.
768  if (Index->getType()->getScalarSizeInBits() !=
769  NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) {
770  Index = Builder.CreateSExtOrTrunc(
771  Index, NewInsts[GEP->getOperand(0)]->getType(),
772  GEP->getOperand(0)->getName() + ".sext");
773  }
774 
775  auto *Op = NewInsts[GEP->getOperand(0)];
776  if (isa<ConstantInt>(Op) && dyn_cast<ConstantInt>(Op)->isZero())
777  NewInsts[GEP] = Index;
778  else
779  NewInsts[GEP] = Builder.CreateNSWAdd(
780  Op, Index, GEP->getOperand(0)->getName() + ".add");
781  continue;
782  }
783  if (isa<PHINode>(Val))
784  continue;
785 
786  llvm_unreachable("Unexpected instruction type");
787  }
788 
789  // Add the incoming values to the PHI nodes.
790  for (Value *Val : Explored) {
791  if (Val == Base)
792  continue;
793  // All the instructions have been created, we can now add edges to the
794  // phi nodes.
795  if (auto *PHI = dyn_cast<PHINode>(Val)) {
796  PHINode *NewPhi = static_cast<PHINode *>(NewInsts[PHI]);
797  for (unsigned I = 0, E = PHI->getNumIncomingValues(); I < E; ++I) {
798  Value *NewIncoming = PHI->getIncomingValue(I);
799 
800  if (NewInsts.find(NewIncoming) != NewInsts.end())
801  NewIncoming = NewInsts[NewIncoming];
802 
803  NewPhi->addIncoming(NewIncoming, PHI->getIncomingBlock(I));
804  }
805  }
806  }
807 
808  for (Value *Val : Explored) {
809  if (Val == Base)
810  continue;
811 
812  // Depending on the type, for external users we have to emit
813  // a GEP or a GEP + ptrtoint.
814  setInsertionPoint(Builder, Val, false);
815 
816  // If required, create an inttoptr instruction for Base.
817  Value *NewBase = Base;
818  if (!Base->getType()->isPointerTy())
819  NewBase = Builder.CreateBitOrPointerCast(Base, Start->getType(),
820  Start->getName() + "to.ptr");
821 
822  Value *GEP = Builder.CreateInBoundsGEP(
823  Start->getType()->getPointerElementType(), NewBase,
824  makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
825 
826  if (!Val->getType()->isPointerTy()) {
827  Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
828  Val->getName() + ".conv");
829  GEP = Cast;
830  }
831  Val->replaceAllUsesWith(GEP);
832  }
833 
834  return NewInsts[Start];
835 }
836 
837 /// Looks through GEPs, IntToPtrInsts and PtrToIntInsts in order to express
838 /// the input Value as a constant indexed GEP. Returns a pair containing
839 /// the GEPs Pointer and Index.
840 static std::pair<Value *, Value *>
842  Type *IndexType = IntegerType::get(V->getContext(),
844 
845  Constant *Index = ConstantInt::getNullValue(IndexType);
846  while (true) {
847  if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
848  // We accept only inbouds GEPs here to exclude the possibility of
849  // overflow.
850  if (!GEP->isInBounds())
851  break;
852  if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
853  GEP->getType() == V->getType()) {
854  V = GEP->getOperand(0);
855  Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
856  Index = ConstantExpr::getAdd(
857  Index, ConstantExpr::getSExtOrBitCast(GEPIndex, IndexType));
858  continue;
859  }
860  break;
861  }
862  if (auto *CI = dyn_cast<IntToPtrInst>(V)) {
863  if (!CI->isNoopCast(DL))
864  break;
865  V = CI->getOperand(0);
866  continue;
867  }
868  if (auto *CI = dyn_cast<PtrToIntInst>(V)) {
869  if (!CI->isNoopCast(DL))
870  break;
871  V = CI->getOperand(0);
872  continue;
873  }
874  break;
875  }
876  return {V, Index};
877 }
878 
879 /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
880 /// We can look through PHIs, GEPs and casts in order to determine a common base
881 /// between GEPLHS and RHS.
883  ICmpInst::Predicate Cond,
884  const DataLayout &DL) {
885  if (!GEPLHS->hasAllConstantIndices())
886  return nullptr;
887 
888  // Make sure the pointers have the same type.
889  if (GEPLHS->getType() != RHS->getType())
890  return nullptr;
891 
892  Value *PtrBase, *Index;
893  std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
894 
895  // The set of nodes that will take part in this transformation.
896  SetVector<Value *> Nodes;
897 
898  if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
899  return nullptr;
900 
901  // We know we can re-write this as
902  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2)
903  // Since we've only looked through inbouds GEPs we know that we
904  // can't have overflow on either side. We can therefore re-write
905  // this as:
906  // OFFSET1 cmp OFFSET2
907  Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes);
908 
909  // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written
910  // GEP having PtrBase as the pointer base, and has returned in NewRHS the
911  // offset. Since Index is the offset of LHS to the base pointer, we will now
912  // compare the offsets instead of comparing the pointers.
913  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS);
914 }
915 
916 /// Fold comparisons between a GEP instruction and something else. At this point
917 /// we know that the GEP is on the LHS of the comparison.
918 Instruction *InstCombiner::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
919  ICmpInst::Predicate Cond,
920  Instruction &I) {
921  // Don't transform signed compares of GEPs into index compares. Even if the
922  // GEP is inbounds, the final add of the base pointer can have signed overflow
923  // and would change the result of the icmp.
924  // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
925  // the maximum signed value for the pointer type.
926  if (ICmpInst::isSigned(Cond))
927  return nullptr;
928 
929  // Look through bitcasts and addrspacecasts. We do not however want to remove
930  // 0 GEPs.
931  if (!isa<GetElementPtrInst>(RHS))
932  RHS = RHS->stripPointerCasts();
933 
934  Value *PtrBase = GEPLHS->getOperand(0);
935  if (PtrBase == RHS && GEPLHS->isInBounds()) {
936  // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
937  // This transformation (ignoring the base and scales) is valid because we
938  // know pointers can't overflow since the gep is inbounds. See if we can
939  // output an optimized form.
940  Value *Offset = evaluateGEPOffsetExpression(GEPLHS, *this, DL);
941 
942  // If not, synthesize the offset the hard way.
943  if (!Offset)
944  Offset = EmitGEPOffset(GEPLHS);
945  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
946  Constant::getNullValue(Offset->getType()));
947  } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
948  // If the base pointers are different, but the indices are the same, just
949  // compare the base pointer.
950  if (PtrBase != GEPRHS->getOperand(0)) {
951  bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
952  IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
953  GEPRHS->getOperand(0)->getType();
954  if (IndicesTheSame)
955  for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
956  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
957  IndicesTheSame = false;
958  break;
959  }
960 
961  // If all indices are the same, just compare the base pointers.
962  if (IndicesTheSame)
963  return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
964 
965  // If we're comparing GEPs with two base pointers that only differ in type
966  // and both GEPs have only constant indices or just one use, then fold
967  // the compare with the adjusted indices.
968  if (GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
969  (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
970  (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
971  PtrBase->stripPointerCasts() ==
972  GEPRHS->getOperand(0)->stripPointerCasts()) {
973  Value *LOffset = EmitGEPOffset(GEPLHS);
974  Value *ROffset = EmitGEPOffset(GEPRHS);
975 
976  // If we looked through an addrspacecast between different sized address
977  // spaces, the LHS and RHS pointers are different sized
978  // integers. Truncate to the smaller one.
979  Type *LHSIndexTy = LOffset->getType();
980  Type *RHSIndexTy = ROffset->getType();
981  if (LHSIndexTy != RHSIndexTy) {
982  if (LHSIndexTy->getPrimitiveSizeInBits() <
983  RHSIndexTy->getPrimitiveSizeInBits()) {
984  ROffset = Builder.CreateTrunc(ROffset, LHSIndexTy);
985  } else
986  LOffset = Builder.CreateTrunc(LOffset, RHSIndexTy);
987  }
988 
989  Value *Cmp = Builder.CreateICmp(ICmpInst::getSignedPredicate(Cond),
990  LOffset, ROffset);
991  return replaceInstUsesWith(I, Cmp);
992  }
993 
994  // Otherwise, the base pointers are different and the indices are
995  // different. Try convert this to an indexed compare by looking through
996  // PHIs/casts.
997  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
998  }
999 
1000  // If one of the GEPs has all zero indices, recurse.
1001  if (GEPLHS->hasAllZeroIndices())
1002  return foldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
1004 
1005  // If the other GEP has all zero indices, recurse.
1006  if (GEPRHS->hasAllZeroIndices())
1007  return foldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
1008 
1009  bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
1010  if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
1011  // If the GEPs only differ by one index, compare it.
1012  unsigned NumDifferences = 0; // Keep track of # differences.
1013  unsigned DiffOperand = 0; // The operand that differs.
1014  for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
1015  if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
1016  if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
1017  GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
1018  // Irreconcilable differences.
1019  NumDifferences = 2;
1020  break;
1021  } else {
1022  if (NumDifferences++) break;
1023  DiffOperand = i;
1024  }
1025  }
1026 
1027  if (NumDifferences == 0) // SAME GEP?
1028  return replaceInstUsesWith(I, // No comparison is needed here.
1029  Builder.getInt1(ICmpInst::isTrueWhenEqual(Cond)));
1030 
1031  else if (NumDifferences == 1 && GEPsInBounds) {
1032  Value *LHSV = GEPLHS->getOperand(DiffOperand);
1033  Value *RHSV = GEPRHS->getOperand(DiffOperand);
1034  // Make sure we do a signed comparison here.
1035  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
1036  }
1037  }
1038 
1039  // Only lower this if the icmp is the only user of the GEP or if we expect
1040  // the result to fold to a constant!
1041  if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
1042  (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
1043  // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
1044  Value *L = EmitGEPOffset(GEPLHS);
1045  Value *R = EmitGEPOffset(GEPRHS);
1046  return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
1047  }
1048  }
1049 
1050  // Try convert this to an indexed compare by looking through PHIs/casts as a
1051  // last resort.
1052  return transformToIndexedCompare(GEPLHS, RHS, Cond, DL);
1053 }
1054 
1055 Instruction *InstCombiner::foldAllocaCmp(ICmpInst &ICI,
1056  const AllocaInst *Alloca,
1057  const Value *Other) {
1058  assert(ICI.isEquality() && "Cannot fold non-equality comparison.");
1059 
1060  // It would be tempting to fold away comparisons between allocas and any
1061  // pointer not based on that alloca (e.g. an argument). However, even
1062  // though such pointers cannot alias, they can still compare equal.
1063  //
1064  // But LLVM doesn't specify where allocas get their memory, so if the alloca
1065  // doesn't escape we can argue that it's impossible to guess its value, and we
1066  // can therefore act as if any such guesses are wrong.
1067  //
1068  // The code below checks that the alloca doesn't escape, and that it's only
1069  // used in a comparison once (the current instruction). The
1070  // single-comparison-use condition ensures that we're trivially folding all
1071  // comparisons against the alloca consistently, and avoids the risk of
1072  // erroneously folding a comparison of the pointer with itself.
1073 
1074  unsigned MaxIter = 32; // Break cycles and bound to constant-time.
1075 
1077  for (const Use &U : Alloca->uses()) {
1078  if (Worklist.size() >= MaxIter)
1079  return nullptr;
1080  Worklist.push_back(&U);
1081  }
1082 
1083  unsigned NumCmps = 0;
1084  while (!Worklist.empty()) {
1085  assert(Worklist.size() <= MaxIter);
1086  const Use *U = Worklist.pop_back_val();
1087  const Value *V = U->getUser();
1088  --MaxIter;
1089 
1090  if (isa<BitCastInst>(V) || isa<GetElementPtrInst>(V) || isa<PHINode>(V) ||
1091  isa<SelectInst>(V)) {
1092  // Track the uses.
1093  } else if (isa<LoadInst>(V)) {
1094  // Loading from the pointer doesn't escape it.
1095  continue;
1096  } else if (const auto *SI = dyn_cast<StoreInst>(V)) {
1097  // Storing *to* the pointer is fine, but storing the pointer escapes it.
1098  if (SI->getValueOperand() == U->get())
1099  return nullptr;
1100  continue;
1101  } else if (isa<ICmpInst>(V)) {
1102  if (NumCmps++)
1103  return nullptr; // Found more than one cmp.
1104  continue;
1105  } else if (const auto *Intrin = dyn_cast<IntrinsicInst>(V)) {
1106  switch (Intrin->getIntrinsicID()) {
1107  // These intrinsics don't escape or compare the pointer. Memset is safe
1108  // because we don't allow ptrtoint. Memcpy and memmove are safe because
1109  // we don't allow stores, so src cannot point to V.
1110  case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
1111  case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
1112  case Intrinsic::memcpy: case Intrinsic::memmove: case Intrinsic::memset:
1113  continue;
1114  default:
1115  return nullptr;
1116  }
1117  } else {
1118  return nullptr;
1119  }
1120  for (const Use &U : V->uses()) {
1121  if (Worklist.size() >= MaxIter)
1122  return nullptr;
1123  Worklist.push_back(&U);
1124  }
1125  }
1126 
1127  Type *CmpTy = CmpInst::makeCmpResultType(Other->getType());
1128  return replaceInstUsesWith(
1129  ICI,
1131 }
1132 
1133 /// Fold "icmp pred (X+CI), X".
1134 Instruction *InstCombiner::foldICmpAddOpConst(Instruction &ICI,
1135  Value *X, ConstantInt *CI,
1136  ICmpInst::Predicate Pred) {
1137  // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
1138  // so the values can never be equal. Similarly for all other "or equals"
1139  // operators.
1140 
1141  // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
1142  // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
1143  // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
1144  if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
1145  Value *R =
1147  return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
1148  }
1149 
1150  // (X+1) >u X --> X <u (0-1) --> X != 255
1151  // (X+2) >u X --> X <u (0-2) --> X <u 254
1152  // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
1153  if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
1154  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
1155 
1156  unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
1158  APInt::getSignedMaxValue(BitWidth));
1159 
1160  // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
1161  // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
1162  // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
1163  // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
1164  // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
1165  // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
1166  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1167  return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
1168 
1169  // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
1170  // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
1171  // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
1172  // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
1173  // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
1174  // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
1175 
1176  assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
1177  Constant *C = Builder.getInt(CI->getValue() - 1);
1178  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
1179 }
1180 
1181 /// Handle "(icmp eq/ne (ashr/lshr AP2, A), AP1)" ->
1182 /// (icmp eq/ne A, Log2(AP2/AP1)) ->
1183 /// (icmp eq/ne A, Log2(AP2) - Log2(AP1)).
1184 Instruction *InstCombiner::foldICmpShrConstConst(ICmpInst &I, Value *A,
1185  const APInt &AP1,
1186  const APInt &AP2) {
1187  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1188 
1189  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1190  if (I.getPredicate() == I.ICMP_NE)
1191  Pred = CmpInst::getInversePredicate(Pred);
1192  return new ICmpInst(Pred, LHS, RHS);
1193  };
1194 
1195  // Don't bother doing any work for cases which InstSimplify handles.
1196  if (AP2.isNullValue())
1197  return nullptr;
1198 
1199  bool IsAShr = isa<AShrOperator>(I.getOperand(0));
1200  if (IsAShr) {
1201  if (AP2.isAllOnesValue())
1202  return nullptr;
1203  if (AP2.isNegative() != AP1.isNegative())
1204  return nullptr;
1205  if (AP2.sgt(AP1))
1206  return nullptr;
1207  }
1208 
1209  if (!AP1)
1210  // 'A' must be large enough to shift out the highest set bit.
1211  return getICmp(I.ICMP_UGT, A,
1212  ConstantInt::get(A->getType(), AP2.logBase2()));
1213 
1214  if (AP1 == AP2)
1215  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1216 
1217  int Shift;
1218  if (IsAShr && AP1.isNegative())
1219  Shift = AP1.countLeadingOnes() - AP2.countLeadingOnes();
1220  else
1221  Shift = AP1.countLeadingZeros() - AP2.countLeadingZeros();
1222 
1223  if (Shift > 0) {
1224  if (IsAShr && AP1 == AP2.ashr(Shift)) {
1225  // There are multiple solutions if we are comparing against -1 and the LHS
1226  // of the ashr is not a power of two.
1227  if (AP1.isAllOnesValue() && !AP2.isPowerOf2())
1228  return getICmp(I.ICMP_UGE, A, ConstantInt::get(A->getType(), Shift));
1229  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1230  } else if (AP1 == AP2.lshr(Shift)) {
1231  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1232  }
1233  }
1234 
1235  // Shifting const2 will never be equal to const1.
1236  // FIXME: This should always be handled by InstSimplify?
1237  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1238  return replaceInstUsesWith(I, TorF);
1239 }
1240 
1241 /// Handle "(icmp eq/ne (shl AP2, A), AP1)" ->
1242 /// (icmp eq/ne A, TrailingZeros(AP1) - TrailingZeros(AP2)).
1243 Instruction *InstCombiner::foldICmpShlConstConst(ICmpInst &I, Value *A,
1244  const APInt &AP1,
1245  const APInt &AP2) {
1246  assert(I.isEquality() && "Cannot fold icmp gt/lt");
1247 
1248  auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) {
1249  if (I.getPredicate() == I.ICMP_NE)
1250  Pred = CmpInst::getInversePredicate(Pred);
1251  return new ICmpInst(Pred, LHS, RHS);
1252  };
1253 
1254  // Don't bother doing any work for cases which InstSimplify handles.
1255  if (AP2.isNullValue())
1256  return nullptr;
1257 
1258  unsigned AP2TrailingZeros = AP2.countTrailingZeros();
1259 
1260  if (!AP1 && AP2TrailingZeros != 0)
1261  return getICmp(
1262  I.ICMP_UGE, A,
1263  ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros));
1264 
1265  if (AP1 == AP2)
1266  return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType()));
1267 
1268  // Get the distance between the lowest bits that are set.
1269  int Shift = AP1.countTrailingZeros() - AP2TrailingZeros;
1270 
1271  if (Shift > 0 && AP2.shl(Shift) == AP1)
1272  return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift));
1273 
1274  // Shifting const2 will never be equal to const1.
1275  // FIXME: This should always be handled by InstSimplify?
1276  auto *TorF = ConstantInt::get(I.getType(), I.getPredicate() == I.ICMP_NE);
1277  return replaceInstUsesWith(I, TorF);
1278 }
1279 
1280 /// The caller has matched a pattern of the form:
1281 /// I = icmp ugt (add (add A, B), CI2), CI1
1282 /// If this is of the form:
1283 /// sum = a + b
1284 /// if (sum+128 >u 255)
1285 /// Then replace it with llvm.sadd.with.overflow.i8.
1286 ///
1288  ConstantInt *CI2, ConstantInt *CI1,
1289  InstCombiner &IC) {
1290  // The transformation we're trying to do here is to transform this into an
1291  // llvm.sadd.with.overflow. To do this, we have to replace the original add
1292  // with a narrower add, and discard the add-with-constant that is part of the
1293  // range check (if we can't eliminate it, this isn't profitable).
1294 
1295  // In order to eliminate the add-with-constant, the compare can be its only
1296  // use.
1297  Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1298  if (!AddWithCst->hasOneUse())
1299  return nullptr;
1300 
1301  // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1302  if (!CI2->getValue().isPowerOf2())
1303  return nullptr;
1304  unsigned NewWidth = CI2->getValue().countTrailingZeros();
1305  if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31)
1306  return nullptr;
1307 
1308  // The width of the new add formed is 1 more than the bias.
1309  ++NewWidth;
1310 
1311  // Check to see that CI1 is an all-ones value with NewWidth bits.
1312  if (CI1->getBitWidth() == NewWidth ||
1313  CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1314  return nullptr;
1315 
1316  // This is only really a signed overflow check if the inputs have been
1317  // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1318  // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1319  unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1320  if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits ||
1321  IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits)
1322  return nullptr;
1323 
1324  // In order to replace the original add with a narrower
1325  // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1326  // and truncates that discard the high bits of the add. Verify that this is
1327  // the case.
1328  Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1329  for (User *U : OrigAdd->users()) {
1330  if (U == AddWithCst)
1331  continue;
1332 
1333  // Only accept truncates for now. We would really like a nice recursive
1334  // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1335  // chain to see which bits of a value are actually demanded. If the
1336  // original add had another add which was then immediately truncated, we
1337  // could still do the transformation.
1338  TruncInst *TI = dyn_cast<TruncInst>(U);
1339  if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1340  return nullptr;
1341  }
1342 
1343  // If the pattern matches, truncate the inputs to the narrower type and
1344  // use the sadd_with_overflow intrinsic to efficiently compute both the
1345  // result and the overflow bit.
1346  Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1348  Intrinsic::sadd_with_overflow, NewType);
1349 
1350  InstCombiner::BuilderTy &Builder = IC.Builder;
1351 
1352  // Put the new code above the original add, in case there are any uses of the
1353  // add between the add and the compare.
1354  Builder.SetInsertPoint(OrigAdd);
1355 
1356  Value *TruncA = Builder.CreateTrunc(A, NewType, A->getName() + ".trunc");
1357  Value *TruncB = Builder.CreateTrunc(B, NewType, B->getName() + ".trunc");
1358  CallInst *Call = Builder.CreateCall(F, {TruncA, TruncB}, "sadd");
1359  Value *Add = Builder.CreateExtractValue(Call, 0, "sadd.result");
1360  Value *ZExt = Builder.CreateZExt(Add, OrigAdd->getType());
1361 
1362  // The inner add was the result of the narrow add, zero extended to the
1363  // wider type. Replace it with the result computed by the intrinsic.
1364  IC.replaceInstUsesWith(*OrigAdd, ZExt);
1365 
1366  // The original icmp gets replaced with the overflow value.
1367  return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1368 }
1369 
1370 // Fold icmp Pred X, C.
1371 Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
1372  CmpInst::Predicate Pred = Cmp.getPredicate();
1373  Value *X = Cmp.getOperand(0);
1374 
1375  const APInt *C;
1376  if (!match(Cmp.getOperand(1), m_APInt(C)))
1377  return nullptr;
1378 
1379  Value *A = nullptr, *B = nullptr;
1380 
1381  // Match the following pattern, which is a common idiom when writing
1382  // overflow-safe integer arithmetic functions. The source performs an addition
1383  // in wider type and explicitly checks for overflow using comparisons against
1384  // INT_MIN and INT_MAX. Simplify by using the sadd_with_overflow intrinsic.
1385  //
1386  // TODO: This could probably be generalized to handle other overflow-safe
1387  // operations if we worked out the formulas to compute the appropriate magic
1388  // constants.
1389  //
1390  // sum = a + b
1391  // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1392  {
1393  ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1394  if (Pred == ICmpInst::ICMP_UGT &&
1395  match(X, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1397  Cmp, A, B, CI2, cast<ConstantInt>(Cmp.getOperand(1)), *this))
1398  return Res;
1399  }
1400 
1401  // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
1402  if (C->isNullValue() && Pred == ICmpInst::ICMP_SGT) {
1404  if (SPR.Flavor == SPF_SMIN) {
1405  if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
1406  return new ICmpInst(Pred, B, Cmp.getOperand(1));
1407  if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
1408  return new ICmpInst(Pred, A, Cmp.getOperand(1));
1409  }
1410  }
1411 
1412  // FIXME: Use m_APInt to allow folds for splat constants.
1413  ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
1414  if (!CI)
1415  return nullptr;
1416 
1417  // Canonicalize icmp instructions based on dominating conditions.
1418  BasicBlock *Parent = Cmp.getParent();
1419  BasicBlock *Dom = Parent->getSinglePredecessor();
1420  auto *BI = Dom ? dyn_cast<BranchInst>(Dom->getTerminator()) : nullptr;
1421  ICmpInst::Predicate Pred2;
1422  BasicBlock *TrueBB, *FalseBB;
1423  ConstantInt *CI2;
1424  if (BI && match(BI, m_Br(m_ICmp(Pred2, m_Specific(X), m_ConstantInt(CI2)),
1425  TrueBB, FalseBB)) &&
1426  TrueBB != FalseBB) {
1427  ConstantRange CR =
1429  ConstantRange DominatingCR =
1430  (Parent == TrueBB)
1433  CmpInst::getInversePredicate(Pred2), CI2->getValue());
1434  ConstantRange Intersection = DominatingCR.intersectWith(CR);
1435  ConstantRange Difference = DominatingCR.difference(CR);
1436  if (Intersection.isEmptySet())
1437  return replaceInstUsesWith(Cmp, Builder.getFalse());
1438  if (Difference.isEmptySet())
1439  return replaceInstUsesWith(Cmp, Builder.getTrue());
1440 
1441  // If this is a normal comparison, it demands all bits. If it is a sign
1442  // bit comparison, it only demands the sign bit.
1443  bool UnusedBit;
1444  bool IsSignBit = isSignBitCheck(Pred, CI->getValue(), UnusedBit);
1445 
1446  // Canonicalizing a sign bit comparison that gets used in a branch,
1447  // pessimizes codegen by generating branch on zero instruction instead
1448  // of a test and branch. So we avoid canonicalizing in such situations
1449  // because test and branch instruction has better branch displacement
1450  // than compare and branch instruction.
1451  if (Cmp.isEquality() || (IsSignBit && hasBranchUse(Cmp)))
1452  return nullptr;
1453 
1454  if (auto *AI = Intersection.getSingleElement())
1455  return new ICmpInst(ICmpInst::ICMP_EQ, X, Builder.getInt(*AI));
1456  if (auto *AD = Difference.getSingleElement())
1457  return new ICmpInst(ICmpInst::ICMP_NE, X, Builder.getInt(*AD));
1458  }
1459 
1460  return nullptr;
1461 }
1462 
1463 /// Fold icmp (trunc X, Y), C.
1464 Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
1465  Instruction *Trunc,
1466  const APInt *C) {
1467  ICmpInst::Predicate Pred = Cmp.getPredicate();
1468  Value *X = Trunc->getOperand(0);
1469  if (C->isOneValue() && C->getBitWidth() > 1) {
1470  // icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
1471  Value *V = nullptr;
1472  if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
1473  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1474  ConstantInt::get(V->getType(), 1));
1475  }
1476 
1477  if (Cmp.isEquality() && Trunc->hasOneUse()) {
1478  // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1479  // of the high bits truncated out of x are known.
1480  unsigned DstBits = Trunc->getType()->getScalarSizeInBits(),
1481  SrcBits = X->getType()->getScalarSizeInBits();
1482  KnownBits Known = computeKnownBits(X, 0, &Cmp);
1483 
1484  // If all the high bits are known, we can do this xform.
1485  if ((Known.Zero | Known.One).countLeadingOnes() >= SrcBits - DstBits) {
1486  // Pull in the high bits from known-ones set.
1487  APInt NewRHS = C->zext(SrcBits);
1488  NewRHS |= Known.One & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
1489  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), NewRHS));
1490  }
1491  }
1492 
1493  return nullptr;
1494 }
1495 
1496 /// Fold icmp (xor X, Y), C.
1497 Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp,
1498  BinaryOperator *Xor,
1499  const APInt *C) {
1500  Value *X = Xor->getOperand(0);
1501  Value *Y = Xor->getOperand(1);
1502  const APInt *XorC;
1503  if (!match(Y, m_APInt(XorC)))
1504  return nullptr;
1505 
1506  // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1507  // fold the xor.
1508  ICmpInst::Predicate Pred = Cmp.getPredicate();
1509  if ((Pred == ICmpInst::ICMP_SLT && C->isNullValue()) ||
1510  (Pred == ICmpInst::ICMP_SGT && C->isAllOnesValue())) {
1511 
1512  // If the sign bit of the XorCst is not set, there is no change to
1513  // the operation, just stop using the Xor.
1514  if (!XorC->isNegative()) {
1515  Cmp.setOperand(0, X);
1516  Worklist.Add(Xor);
1517  return &Cmp;
1518  }
1519 
1520  // Was the old condition true if the operand is positive?
1521  bool isTrueIfPositive = Pred == ICmpInst::ICMP_SGT;
1522 
1523  // If so, the new one isn't.
1524  isTrueIfPositive ^= true;
1525 
1526  Constant *CmpConstant = cast<Constant>(Cmp.getOperand(1));
1527  if (isTrueIfPositive)
1528  return new ICmpInst(ICmpInst::ICMP_SGT, X, SubOne(CmpConstant));
1529  else
1530  return new ICmpInst(ICmpInst::ICMP_SLT, X, AddOne(CmpConstant));
1531  }
1532 
1533  if (Xor->hasOneUse()) {
1534  // (icmp u/s (xor X SignMask), C) -> (icmp s/u X, (xor C SignMask))
1535  if (!Cmp.isEquality() && XorC->isSignMask()) {
1536  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1537  : Cmp.getSignedPredicate();
1538  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), *C ^ *XorC));
1539  }
1540 
1541  // (icmp u/s (xor X ~SignMask), C) -> (icmp s/u X, (xor C ~SignMask))
1542  if (!Cmp.isEquality() && XorC->isMaxSignedValue()) {
1543  Pred = Cmp.isSigned() ? Cmp.getUnsignedPredicate()
1544  : Cmp.getSignedPredicate();
1545  Pred = Cmp.getSwappedPredicate(Pred);
1546  return new ICmpInst(Pred, X, ConstantInt::get(X->getType(), *C ^ *XorC));
1547  }
1548  }
1549 
1550  // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1551  // iff -C is a power of 2
1552  if (Pred == ICmpInst::ICMP_UGT && *XorC == ~(*C) && (*C + 1).isPowerOf2())
1553  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
1554 
1555  // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1556  // iff -C is a power of 2
1557  if (Pred == ICmpInst::ICMP_ULT && *XorC == -(*C) && C->isPowerOf2())
1558  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
1559 
1560  return nullptr;
1561 }
1562 
1563 /// Fold icmp (and (sh X, Y), C2), C1.
1564 Instruction *InstCombiner::foldICmpAndShift(ICmpInst &Cmp, BinaryOperator *And,
1565  const APInt *C1, const APInt *C2) {
1566  BinaryOperator *Shift = dyn_cast<BinaryOperator>(And->getOperand(0));
1567  if (!Shift || !Shift->isShift())
1568  return nullptr;
1569 
1570  // If this is: (X >> C3) & C2 != C1 (where any shift and any compare could
1571  // exist), turn it into (X & (C2 << C3)) != (C1 << C3). This happens a LOT in
1572  // code produced by the clang front-end, for bitfield access.
1573  // This seemingly simple opportunity to fold away a shift turns out to be
1574  // rather complicated. See PR17827 for details.
1575  unsigned ShiftOpcode = Shift->getOpcode();
1576  bool IsShl = ShiftOpcode == Instruction::Shl;
1577  const APInt *C3;
1578  if (match(Shift->getOperand(1), m_APInt(C3))) {
1579  bool CanFold = false;
1580  if (ShiftOpcode == Instruction::AShr) {
1581  // There may be some constraints that make this possible, but nothing
1582  // simple has been discovered yet.
1583  CanFold = false;
1584  } else if (ShiftOpcode == Instruction::Shl) {
1585  // For a left shift, we can fold if the comparison is not signed. We can
1586  // also fold a signed comparison if the mask value and comparison value
1587  // are not negative. These constraints may not be obvious, but we can
1588  // prove that they are correct using an SMT solver.
1589  if (!Cmp.isSigned() || (!C2->isNegative() && !C1->isNegative()))
1590  CanFold = true;
1591  } else if (ShiftOpcode == Instruction::LShr) {
1592  // For a logical right shift, we can fold if the comparison is not signed.
1593  // We can also fold a signed comparison if the shifted mask value and the
1594  // shifted comparison value are not negative. These constraints may not be
1595  // obvious, but we can prove that they are correct using an SMT solver.
1596  if (!Cmp.isSigned() ||
1597  (!C2->shl(*C3).isNegative() && !C1->shl(*C3).isNegative()))
1598  CanFold = true;
1599  }
1600 
1601  if (CanFold) {
1602  APInt NewCst = IsShl ? C1->lshr(*C3) : C1->shl(*C3);
1603  APInt SameAsC1 = IsShl ? NewCst.shl(*C3) : NewCst.lshr(*C3);
1604  // Check to see if we are shifting out any of the bits being compared.
1605  if (SameAsC1 != *C1) {
1606  // If we shifted bits out, the fold is not going to work out. As a
1607  // special case, check to see if this means that the result is always
1608  // true or false now.
1609  if (Cmp.getPredicate() == ICmpInst::ICMP_EQ)
1610  return replaceInstUsesWith(Cmp, ConstantInt::getFalse(Cmp.getType()));
1611  if (Cmp.getPredicate() == ICmpInst::ICMP_NE)
1612  return replaceInstUsesWith(Cmp, ConstantInt::getTrue(Cmp.getType()));
1613  } else {
1614  Cmp.setOperand(1, ConstantInt::get(And->getType(), NewCst));
1615  APInt NewAndCst = IsShl ? C2->lshr(*C3) : C2->shl(*C3);
1616  And->setOperand(1, ConstantInt::get(And->getType(), NewAndCst));
1617  And->setOperand(0, Shift->getOperand(0));
1618  Worklist.Add(Shift); // Shift is dead.
1619  return &Cmp;
1620  }
1621  }
1622  }
1623 
1624  // Turn ((X >> Y) & C2) == 0 into (X & (C2 << Y)) == 0. The latter is
1625  // preferable because it allows the C2 << Y expression to be hoisted out of a
1626  // loop if Y is invariant and X is not.
1627  if (Shift->hasOneUse() && C1->isNullValue() && Cmp.isEquality() &&
1628  !Shift->isArithmeticShift() && !isa<Constant>(Shift->getOperand(0))) {
1629  // Compute C2 << Y.
1630  Value *NewShift =
1631  IsShl ? Builder.CreateLShr(And->getOperand(1), Shift->getOperand(1))
1632  : Builder.CreateShl(And->getOperand(1), Shift->getOperand(1));
1633 
1634  // Compute X & (C2 << Y).
1635  Value *NewAnd = Builder.CreateAnd(Shift->getOperand(0), NewShift);
1636  Cmp.setOperand(0, NewAnd);
1637  return &Cmp;
1638  }
1639 
1640  return nullptr;
1641 }
1642 
1643 /// Fold icmp (and X, C2), C1.
1644 Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
1645  BinaryOperator *And,
1646  const APInt *C1) {
1647  const APInt *C2;
1648  if (!match(And->getOperand(1), m_APInt(C2)))
1649  return nullptr;
1650 
1651  if (!And->hasOneUse() || !And->getOperand(0)->hasOneUse())
1652  return nullptr;
1653 
1654  // If the LHS is an 'and' of a truncate and we can widen the and/compare to
1655  // the input width without changing the value produced, eliminate the cast:
1656  //
1657  // icmp (and (trunc W), C2), C1 -> icmp (and W, C2'), C1'
1658  //
1659  // We can do this transformation if the constants do not have their sign bits
1660  // set or if it is an equality comparison. Extending a relational comparison
1661  // when we're checking the sign bit would not work.
1662  Value *W;
1663  if (match(And->getOperand(0), m_Trunc(m_Value(W))) &&
1664  (Cmp.isEquality() || (!C1->isNegative() && !C2->isNegative()))) {
1665  // TODO: Is this a good transform for vectors? Wider types may reduce
1666  // throughput. Should this transform be limited (even for scalars) by using
1667  // shouldChangeType()?
1668  if (!Cmp.getType()->isVectorTy()) {
1669  Type *WideType = W->getType();
1670  unsigned WideScalarBits = WideType->getScalarSizeInBits();
1671  Constant *ZextC1 = ConstantInt::get(WideType, C1->zext(WideScalarBits));
1672  Constant *ZextC2 = ConstantInt::get(WideType, C2->zext(WideScalarBits));
1673  Value *NewAnd = Builder.CreateAnd(W, ZextC2, And->getName());
1674  return new ICmpInst(Cmp.getPredicate(), NewAnd, ZextC1);
1675  }
1676  }
1677 
1678  if (Instruction *I = foldICmpAndShift(Cmp, And, C1, C2))
1679  return I;
1680 
1681  // (icmp pred (and (or (lshr A, B), A), 1), 0) -->
1682  // (icmp pred (and A, (or (shl 1, B), 1), 0))
1683  //
1684  // iff pred isn't signed
1685  if (!Cmp.isSigned() && C1->isNullValue() &&
1686  match(And->getOperand(1), m_One())) {
1687  Constant *One = cast<Constant>(And->getOperand(1));
1688  Value *Or = And->getOperand(0);
1689  Value *A, *B, *LShr;
1690  if (match(Or, m_Or(m_Value(LShr), m_Value(A))) &&
1691  match(LShr, m_LShr(m_Specific(A), m_Value(B)))) {
1692  unsigned UsesRemoved = 0;
1693  if (And->hasOneUse())
1694  ++UsesRemoved;
1695  if (Or->hasOneUse())
1696  ++UsesRemoved;
1697  if (LShr->hasOneUse())
1698  ++UsesRemoved;
1699 
1700  // Compute A & ((1 << B) | 1)
1701  Value *NewOr = nullptr;
1702  if (auto *C = dyn_cast<Constant>(B)) {
1703  if (UsesRemoved >= 1)
1704  NewOr = ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One);
1705  } else {
1706  if (UsesRemoved >= 3)
1707  NewOr = Builder.CreateOr(Builder.CreateShl(One, B, LShr->getName(),
1708  /*HasNUW=*/true),
1709  One, Or->getName());
1710  }
1711  if (NewOr) {
1712  Value *NewAnd = Builder.CreateAnd(A, NewOr, And->getName());
1713  Cmp.setOperand(0, NewAnd);
1714  return &Cmp;
1715  }
1716  }
1717  }
1718 
1719  // (X & C2) > C1 --> (X & C2) != 0, if any bit set in (X & C2) will produce a
1720  // result greater than C1.
1721  unsigned NumTZ = C2->countTrailingZeros();
1722  if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && NumTZ < C2->getBitWidth() &&
1723  APInt::getOneBitSet(C2->getBitWidth(), NumTZ).ugt(*C1)) {
1725  return new ICmpInst(ICmpInst::ICMP_NE, And, Zero);
1726  }
1727 
1728  return nullptr;
1729 }
1730 
1731 /// Fold icmp (and X, Y), C.
1732 Instruction *InstCombiner::foldICmpAndConstant(ICmpInst &Cmp,
1733  BinaryOperator *And,
1734  const APInt *C) {
1735  if (Instruction *I = foldICmpAndConstConst(Cmp, And, C))
1736  return I;
1737 
1738  // TODO: These all require that Y is constant too, so refactor with the above.
1739 
1740  // Try to optimize things like "A[i] & 42 == 0" to index computations.
1741  Value *X = And->getOperand(0);
1742  Value *Y = And->getOperand(1);
1743  if (auto *LI = dyn_cast<LoadInst>(X))
1744  if (auto *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1745  if (auto *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1746  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1747  !LI->isVolatile() && isa<ConstantInt>(Y)) {
1748  ConstantInt *C2 = cast<ConstantInt>(Y);
1749  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, Cmp, C2))
1750  return Res;
1751  }
1752 
1753  if (!Cmp.isEquality())
1754  return nullptr;
1755 
1756  // X & -C == -C -> X > u ~C
1757  // X & -C != -C -> X <= u ~C
1758  // iff C is a power of 2
1759  if (Cmp.getOperand(1) == Y && (-(*C)).isPowerOf2()) {
1760  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_UGT
1762  return new ICmpInst(NewPred, X, SubOne(cast<Constant>(Cmp.getOperand(1))));
1763  }
1764 
1765  // (X & C2) == 0 -> (trunc X) >= 0
1766  // (X & C2) != 0 -> (trunc X) < 0
1767  // iff C2 is a power of 2 and it masks the sign bit of a legal integer type.
1768  const APInt *C2;
1769  if (And->hasOneUse() && C->isNullValue() && match(Y, m_APInt(C2))) {
1770  int32_t ExactLogBase2 = C2->exactLogBase2();
1771  if (ExactLogBase2 != -1 && DL.isLegalInteger(ExactLogBase2 + 1)) {
1772  Type *NTy = IntegerType::get(Cmp.getContext(), ExactLogBase2 + 1);
1773  if (And->getType()->isVectorTy())
1774  NTy = VectorType::get(NTy, And->getType()->getVectorNumElements());
1775  Value *Trunc = Builder.CreateTrunc(X, NTy);
1776  auto NewPred = Cmp.getPredicate() == CmpInst::ICMP_EQ ? CmpInst::ICMP_SGE
1778  return new ICmpInst(NewPred, Trunc, Constant::getNullValue(NTy));
1779  }
1780  }
1781 
1782  return nullptr;
1783 }
1784 
1785 /// Fold icmp (or X, Y), C.
1786 Instruction *InstCombiner::foldICmpOrConstant(ICmpInst &Cmp, BinaryOperator *Or,
1787  const APInt *C) {
1788  ICmpInst::Predicate Pred = Cmp.getPredicate();
1789  if (C->isOneValue()) {
1790  // icmp slt signum(V) 1 --> icmp slt V, 1
1791  Value *V = nullptr;
1792  if (Pred == ICmpInst::ICMP_SLT && match(Or, m_Signum(m_Value(V))))
1793  return new ICmpInst(ICmpInst::ICMP_SLT, V,
1794  ConstantInt::get(V->getType(), 1));
1795  }
1796 
1797  // X | C == C --> X <=u C
1798  // X | C != C --> X >u C
1799  // iff C+1 is a power of 2 (C is a bitmask of the low bits)
1800  if (Cmp.isEquality() && Cmp.getOperand(1) == Or->getOperand(1) &&
1801  (*C + 1).isPowerOf2()) {
1803  return new ICmpInst(Pred, Or->getOperand(0), Or->getOperand(1));
1804  }
1805 
1806  if (!Cmp.isEquality() || !C->isNullValue() || !Or->hasOneUse())
1807  return nullptr;
1808 
1809  Value *P, *Q;
1810  if (match(Or, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1811  // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1812  // -> and (icmp eq P, null), (icmp eq Q, null).
1813  Value *CmpP =
1814  Builder.CreateICmp(Pred, P, ConstantInt::getNullValue(P->getType()));
1815  Value *CmpQ =
1816  Builder.CreateICmp(Pred, Q, ConstantInt::getNullValue(Q->getType()));
1817  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1818  return BinaryOperator::Create(BOpc, CmpP, CmpQ);
1819  }
1820 
1821  // Are we using xors to bitwise check for a pair of (in)equalities? Convert to
1822  // a shorter form that has more potential to be folded even further.
1823  Value *X1, *X2, *X3, *X4;
1824  if (match(Or->getOperand(0), m_OneUse(m_Xor(m_Value(X1), m_Value(X2)))) &&
1825  match(Or->getOperand(1), m_OneUse(m_Xor(m_Value(X3), m_Value(X4))))) {
1826  // ((X1 ^ X2) || (X3 ^ X4)) == 0 --> (X1 == X2) && (X3 == X4)
1827  // ((X1 ^ X2) || (X3 ^ X4)) != 0 --> (X1 != X2) || (X3 != X4)
1828  Value *Cmp12 = Builder.CreateICmp(Pred, X1, X2);
1829  Value *Cmp34 = Builder.CreateICmp(Pred, X3, X4);
1830  auto BOpc = Pred == CmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
1831  return BinaryOperator::Create(BOpc, Cmp12, Cmp34);
1832  }
1833 
1834  return nullptr;
1835 }
1836 
1837 /// Fold icmp (mul X, Y), C.
1838 Instruction *InstCombiner::foldICmpMulConstant(ICmpInst &Cmp,
1839  BinaryOperator *Mul,
1840  const APInt *C) {
1841  const APInt *MulC;
1842  if (!match(Mul->getOperand(1), m_APInt(MulC)))
1843  return nullptr;
1844 
1845  // If this is a test of the sign bit and the multiply is sign-preserving with
1846  // a constant operand, use the multiply LHS operand instead.
1847  ICmpInst::Predicate Pred = Cmp.getPredicate();
1848  if (isSignTest(Pred, *C) && Mul->hasNoSignedWrap()) {
1849  if (MulC->isNegative())
1850  Pred = ICmpInst::getSwappedPredicate(Pred);
1851  return new ICmpInst(Pred, Mul->getOperand(0),
1853  }
1854 
1855  return nullptr;
1856 }
1857 
1858 /// Fold icmp (shl 1, Y), C.
1860  const APInt *C) {
1861  Value *Y;
1862  if (!match(Shl, m_Shl(m_One(), m_Value(Y))))
1863  return nullptr;
1864 
1865  Type *ShiftType = Shl->getType();
1866  uint32_t TypeBits = C->getBitWidth();
1867  bool CIsPowerOf2 = C->isPowerOf2();
1868  ICmpInst::Predicate Pred = Cmp.getPredicate();
1869  if (Cmp.isUnsigned()) {
1870  // (1 << Y) pred C -> Y pred Log2(C)
1871  if (!CIsPowerOf2) {
1872  // (1 << Y) < 30 -> Y <= 4
1873  // (1 << Y) <= 30 -> Y <= 4
1874  // (1 << Y) >= 30 -> Y > 4
1875  // (1 << Y) > 30 -> Y > 4
1876  if (Pred == ICmpInst::ICMP_ULT)
1877  Pred = ICmpInst::ICMP_ULE;
1878  else if (Pred == ICmpInst::ICMP_UGE)
1879  Pred = ICmpInst::ICMP_UGT;
1880  }
1881 
1882  // (1 << Y) >= 2147483648 -> Y >= 31 -> Y == 31
1883  // (1 << Y) < 2147483648 -> Y < 31 -> Y != 31
1884  unsigned CLog2 = C->logBase2();
1885  if (CLog2 == TypeBits - 1) {
1886  if (Pred == ICmpInst::ICMP_UGE)
1887  Pred = ICmpInst::ICMP_EQ;
1888  else if (Pred == ICmpInst::ICMP_ULT)
1889  Pred = ICmpInst::ICMP_NE;
1890  }
1891  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, CLog2));
1892  } else if (Cmp.isSigned()) {
1893  Constant *BitWidthMinusOne = ConstantInt::get(ShiftType, TypeBits - 1);
1894  if (C->isAllOnesValue()) {
1895  // (1 << Y) <= -1 -> Y == 31
1896  if (Pred == ICmpInst::ICMP_SLE)
1897  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1898 
1899  // (1 << Y) > -1 -> Y != 31
1900  if (Pred == ICmpInst::ICMP_SGT)
1901  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1902  } else if (!(*C)) {
1903  // (1 << Y) < 0 -> Y == 31
1904  // (1 << Y) <= 0 -> Y == 31
1905  if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1906  return new ICmpInst(ICmpInst::ICMP_EQ, Y, BitWidthMinusOne);
1907 
1908  // (1 << Y) >= 0 -> Y != 31
1909  // (1 << Y) > 0 -> Y != 31
1910  if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1911  return new ICmpInst(ICmpInst::ICMP_NE, Y, BitWidthMinusOne);
1912  }
1913  } else if (Cmp.isEquality() && CIsPowerOf2) {
1914  return new ICmpInst(Pred, Y, ConstantInt::get(ShiftType, C->logBase2()));
1915  }
1916 
1917  return nullptr;
1918 }
1919 
1920 /// Fold icmp (shl X, Y), C.
1921 Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp,
1922  BinaryOperator *Shl,
1923  const APInt *C) {
1924  const APInt *ShiftVal;
1925  if (Cmp.isEquality() && match(Shl->getOperand(0), m_APInt(ShiftVal)))
1926  return foldICmpShlConstConst(Cmp, Shl->getOperand(1), *C, *ShiftVal);
1927 
1928  const APInt *ShiftAmt;
1929  if (!match(Shl->getOperand(1), m_APInt(ShiftAmt)))
1930  return foldICmpShlOne(Cmp, Shl, C);
1931 
1932  // Check that the shift amount is in range. If not, don't perform undefined
1933  // shifts. When the shift is visited, it will be simplified.
1934  unsigned TypeBits = C->getBitWidth();
1935  if (ShiftAmt->uge(TypeBits))
1936  return nullptr;
1937 
1938  ICmpInst::Predicate Pred = Cmp.getPredicate();
1939  Value *X = Shl->getOperand(0);
1940  Type *ShType = Shl->getType();
1941 
1942  // NSW guarantees that we are only shifting out sign bits from the high bits,
1943  // so we can ASHR the compare constant without needing a mask and eliminate
1944  // the shift.
1945  if (Shl->hasNoSignedWrap()) {
1946  if (Pred == ICmpInst::ICMP_SGT) {
1947  // icmp Pred (shl nsw X, ShiftAmt), C --> icmp Pred X, (C >>s ShiftAmt)
1948  APInt ShiftedC = C->ashr(*ShiftAmt);
1949  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1950  }
1951  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1952  // This is the same code as the SGT case, but assert the pre-condition
1953  // that is needed for this to work with equality predicates.
1954  assert(C->ashr(*ShiftAmt).shl(*ShiftAmt) == *C &&
1955  "Compare known true or false was not folded");
1956  APInt ShiftedC = C->ashr(*ShiftAmt);
1957  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1958  }
1959  if (Pred == ICmpInst::ICMP_SLT) {
1960  // SLE is the same as above, but SLE is canonicalized to SLT, so convert:
1961  // (X << S) <=s C is equiv to X <=s (C >> S) for all C
1962  // (X << S) <s (C + 1) is equiv to X <s (C >> S) + 1 if C <s SMAX
1963  // (X << S) <s C is equiv to X <s ((C - 1) >> S) + 1 if C >s SMIN
1964  assert(!C->isMinSignedValue() && "Unexpected icmp slt");
1965  APInt ShiftedC = (*C - 1).ashr(*ShiftAmt) + 1;
1966  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1967  }
1968  // If this is a signed comparison to 0 and the shift is sign preserving,
1969  // use the shift LHS operand instead; isSignTest may change 'Pred', so only
1970  // do that if we're sure to not continue on in this function.
1971  if (isSignTest(Pred, *C))
1972  return new ICmpInst(Pred, X, Constant::getNullValue(ShType));
1973  }
1974 
1975  // NUW guarantees that we are only shifting out zero bits from the high bits,
1976  // so we can LSHR the compare constant without needing a mask and eliminate
1977  // the shift.
1978  if (Shl->hasNoUnsignedWrap()) {
1979  if (Pred == ICmpInst::ICMP_UGT) {
1980  // icmp Pred (shl nuw X, ShiftAmt), C --> icmp Pred X, (C >>u ShiftAmt)
1981  APInt ShiftedC = C->lshr(*ShiftAmt);
1982  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1983  }
1984  if (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE) {
1985  // This is the same code as the UGT case, but assert the pre-condition
1986  // that is needed for this to work with equality predicates.
1987  assert(C->lshr(*ShiftAmt).shl(*ShiftAmt) == *C &&
1988  "Compare known true or false was not folded");
1989  APInt ShiftedC = C->lshr(*ShiftAmt);
1990  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
1991  }
1992  if (Pred == ICmpInst::ICMP_ULT) {
1993  // ULE is the same as above, but ULE is canonicalized to ULT, so convert:
1994  // (X << S) <=u C is equiv to X <=u (C >> S) for all C
1995  // (X << S) <u (C + 1) is equiv to X <u (C >> S) + 1 if C <u ~0u
1996  // (X << S) <u C is equiv to X <u ((C - 1) >> S) + 1 if C >u 0
1997  assert(C->ugt(0) && "ult 0 should have been eliminated");
1998  APInt ShiftedC = (*C - 1).lshr(*ShiftAmt) + 1;
1999  return new ICmpInst(Pred, X, ConstantInt::get(ShType, ShiftedC));
2000  }
2001  }
2002 
2003  if (Cmp.isEquality() && Shl->hasOneUse()) {
2004  // Strength-reduce the shift into an 'and'.
2006  ShType,
2007  APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt->getZExtValue()));
2008  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
2009  Constant *LShrC = ConstantInt::get(ShType, C->lshr(*ShiftAmt));
2010  return new ICmpInst(Pred, And, LShrC);
2011  }
2012 
2013  // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
2014  bool TrueIfSigned = false;
2015  if (Shl->hasOneUse() && isSignBitCheck(Pred, *C, TrueIfSigned)) {
2016  // (X << 31) <s 0 --> (X & 1) != 0
2018  ShType,
2019  APInt::getOneBitSet(TypeBits, TypeBits - ShiftAmt->getZExtValue() - 1));
2020  Value *And = Builder.CreateAnd(X, Mask, Shl->getName() + ".mask");
2021  return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
2022  And, Constant::getNullValue(ShType));
2023  }
2024 
2025  // Transform (icmp pred iM (shl iM %v, N), C)
2026  // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (C>>N))
2027  // Transform the shl to a trunc if (trunc (C>>N)) has no loss and M-N.
2028  // This enables us to get rid of the shift in favor of a trunc that may be
2029  // free on the target. It has the additional benefit of comparing to a
2030  // smaller constant that may be more target-friendly.
2031  unsigned Amt = ShiftAmt->getLimitedValue(TypeBits - 1);
2032  if (Shl->hasOneUse() && Amt != 0 && C->countTrailingZeros() >= Amt &&
2033  DL.isLegalInteger(TypeBits - Amt)) {
2034  Type *TruncTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
2035  if (ShType->isVectorTy())
2036  TruncTy = VectorType::get(TruncTy, ShType->getVectorNumElements());
2037  Constant *NewC =
2038  ConstantInt::get(TruncTy, C->ashr(*ShiftAmt).trunc(TypeBits - Amt));
2039  return new ICmpInst(Pred, Builder.CreateTrunc(X, TruncTy), NewC);
2040  }
2041 
2042  return nullptr;
2043 }
2044 
2045 /// Fold icmp ({al}shr X, Y), C.
2046 Instruction *InstCombiner::foldICmpShrConstant(ICmpInst &Cmp,
2047  BinaryOperator *Shr,
2048  const APInt *C) {
2049  // An exact shr only shifts out zero bits, so:
2050  // icmp eq/ne (shr X, Y), 0 --> icmp eq/ne X, 0
2051  Value *X = Shr->getOperand(0);
2052  CmpInst::Predicate Pred = Cmp.getPredicate();
2053  if (Cmp.isEquality() && Shr->isExact() && Shr->hasOneUse() &&
2054  C->isNullValue())
2055  return new ICmpInst(Pred, X, Cmp.getOperand(1));
2056 
2057  const APInt *ShiftVal;
2058  if (Cmp.isEquality() && match(Shr->getOperand(0), m_APInt(ShiftVal)))
2059  return foldICmpShrConstConst(Cmp, Shr->getOperand(1), *C, *ShiftVal);
2060 
2061  const APInt *ShiftAmt;
2062  if (!match(Shr->getOperand(1), m_APInt(ShiftAmt)))
2063  return nullptr;
2064 
2065  // Check that the shift amount is in range. If not, don't perform undefined
2066  // shifts. When the shift is visited it will be simplified.
2067  unsigned TypeBits = C->getBitWidth();
2068  unsigned ShAmtVal = ShiftAmt->getLimitedValue(TypeBits);
2069  if (ShAmtVal >= TypeBits || ShAmtVal == 0)
2070  return nullptr;
2071 
2072  bool IsAShr = Shr->getOpcode() == Instruction::AShr;
2073  if (!Cmp.isEquality()) {
2074  // If we have an unsigned comparison and an ashr, we can't simplify this.
2075  // Similarly for signed comparisons with lshr.
2076  if (Cmp.isSigned() != IsAShr)
2077  return nullptr;
2078 
2079  // Otherwise, all lshr and most exact ashr's are equivalent to a udiv/sdiv
2080  // by a power of 2. Since we already have logic to simplify these,
2081  // transform to div and then simplify the resultant comparison.
2082  if (IsAShr && (!Shr->isExact() || ShAmtVal == TypeBits - 1))
2083  return nullptr;
2084 
2085  // Revisit the shift (to delete it).
2086  Worklist.Add(Shr);
2087 
2088  Constant *DivCst = ConstantInt::get(
2089  Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal));
2090 
2091  Value *Tmp = IsAShr ? Builder.CreateSDiv(X, DivCst, "", Shr->isExact())
2092  : Builder.CreateUDiv(X, DivCst, "", Shr->isExact());
2093 
2094  Cmp.setOperand(0, Tmp);
2095 
2096  // If the builder folded the binop, just return it.
2097  BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp);
2098  if (!TheDiv)
2099  return &Cmp;
2100 
2101  // Otherwise, fold this div/compare.
2102  assert(TheDiv->getOpcode() == Instruction::SDiv ||
2103  TheDiv->getOpcode() == Instruction::UDiv);
2104 
2105  Instruction *Res = foldICmpDivConstant(Cmp, TheDiv, C);
2106  assert(Res && "This div/cst should have folded!");
2107  return Res;
2108  }
2109 
2110  // Handle equality comparisons of shift-by-constant.
2111 
2112  // If the comparison constant changes with the shift, the comparison cannot
2113  // succeed (bits of the comparison constant cannot match the shifted value).
2114  // This should be known by InstSimplify and already be folded to true/false.
2115  assert(((IsAShr && C->shl(ShAmtVal).ashr(ShAmtVal) == *C) ||
2116  (!IsAShr && C->shl(ShAmtVal).lshr(ShAmtVal) == *C)) &&
2117  "Expected icmp+shr simplify did not occur.");
2118 
2119  // Check if the bits shifted out are known to be zero. If so, we can compare
2120  // against the unshifted value:
2121  // (X & 4) >> 1 == 2 --> (X & 4) == 4.
2122  Constant *ShiftedCmpRHS = ConstantInt::get(Shr->getType(), *C << ShAmtVal);
2123  if (Shr->hasOneUse()) {
2124  if (Shr->isExact())
2125  return new ICmpInst(Pred, X, ShiftedCmpRHS);
2126 
2127  // Otherwise strength reduce the shift into an 'and'.
2128  APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
2129  Constant *Mask = ConstantInt::get(Shr->getType(), Val);
2130  Value *And = Builder.CreateAnd(X, Mask, Shr->getName() + ".mask");
2131  return new ICmpInst(Pred, And, ShiftedCmpRHS);
2132  }
2133 
2134  return nullptr;
2135 }
2136 
2137 /// Fold icmp (udiv X, Y), C.
2138 Instruction *InstCombiner::foldICmpUDivConstant(ICmpInst &Cmp,
2139  BinaryOperator *UDiv,
2140  const APInt *C) {
2141  const APInt *C2;
2142  if (!match(UDiv->getOperand(0), m_APInt(C2)))
2143  return nullptr;
2144 
2145  assert(*C2 != 0 && "udiv 0, X should have been simplified already.");
2146 
2147  // (icmp ugt (udiv C2, Y), C) -> (icmp ule Y, C2/(C+1))
2148  Value *Y = UDiv->getOperand(1);
2149  if (Cmp.getPredicate() == ICmpInst::ICMP_UGT) {
2150  assert(!C->isMaxValue() &&
2151  "icmp ugt X, UINT_MAX should have been simplified already.");
2152  return new ICmpInst(ICmpInst::ICMP_ULE, Y,
2153  ConstantInt::get(Y->getType(), C2->udiv(*C + 1)));
2154  }
2155 
2156  // (icmp ult (udiv C2, Y), C) -> (icmp ugt Y, C2/C)
2157  if (Cmp.getPredicate() == ICmpInst::ICMP_ULT) {
2158  assert(*C != 0 && "icmp ult X, 0 should have been simplified already.");
2159  return new ICmpInst(ICmpInst::ICMP_UGT, Y,
2160  ConstantInt::get(Y->getType(), C2->udiv(*C)));
2161  }
2162 
2163  return nullptr;
2164 }
2165 
2166 /// Fold icmp ({su}div X, Y), C.
2167 Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &Cmp,
2168  BinaryOperator *Div,
2169  const APInt *C) {
2170  // Fold: icmp pred ([us]div X, C2), C -> range test
2171  // Fold this div into the comparison, producing a range check.
2172  // Determine, based on the divide type, what the range is being
2173  // checked. If there is an overflow on the low or high side, remember
2174  // it, otherwise compute the range [low, hi) bounding the new value.
2175  // See: InsertRangeTest above for the kinds of replacements possible.
2176  const APInt *C2;
2177  if (!match(Div->getOperand(1), m_APInt(C2)))
2178  return nullptr;
2179 
2180  // FIXME: If the operand types don't match the type of the divide
2181  // then don't attempt this transform. The code below doesn't have the
2182  // logic to deal with a signed divide and an unsigned compare (and
2183  // vice versa). This is because (x /s C2) <s C produces different
2184  // results than (x /s C2) <u C or (x /u C2) <s C or even
2185  // (x /u C2) <u C. Simply casting the operands and result won't
2186  // work. :( The if statement below tests that condition and bails
2187  // if it finds it.
2188  bool DivIsSigned = Div->getOpcode() == Instruction::SDiv;
2189  if (!Cmp.isEquality() && DivIsSigned != Cmp.isSigned())
2190  return nullptr;
2191 
2192  // The ProdOV computation fails on divide by 0 and divide by -1. Cases with
2193  // INT_MIN will also fail if the divisor is 1. Although folds of all these
2194  // division-by-constant cases should be present, we can not assert that they
2195  // have happened before we reach this icmp instruction.
2196  if (C2->isNullValue() || C2->isOneValue() ||
2197  (DivIsSigned && C2->isAllOnesValue()))
2198  return nullptr;
2199 
2200  // TODO: We could do all of the computations below using APInt.
2201  Constant *CmpRHS = cast<Constant>(Cmp.getOperand(1));
2202  Constant *DivRHS = cast<Constant>(Div->getOperand(1));
2203 
2204  // Compute Prod = CmpRHS * DivRHS. We are essentially solving an equation of
2205  // form X / C2 = C. We solve for X by multiplying C2 (DivRHS) and C (CmpRHS).
2206  // By solving for X, we can turn this into a range check instead of computing
2207  // a divide.
2208  Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS);
2209 
2210  // Determine if the product overflows by seeing if the product is not equal to
2211  // the divide. Make sure we do the same kind of divide as in the LHS
2212  // instruction that we're folding.
2213  bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS)
2214  : ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
2215 
2216  ICmpInst::Predicate Pred = Cmp.getPredicate();
2217 
2218  // If the division is known to be exact, then there is no remainder from the
2219  // divide, so the covered range size is unit, otherwise it is the divisor.
2220  Constant *RangeSize =
2221  Div->isExact() ? ConstantInt::get(Div->getType(), 1) : DivRHS;
2222 
2223  // Figure out the interval that is being checked. For example, a comparison
2224  // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
2225  // Compute this interval based on the constants involved and the signedness of
2226  // the compare/divide. This computes a half-open interval, keeping track of
2227  // whether either value in the interval overflows. After analysis each
2228  // overflow variable is set to 0 if it's corresponding bound variable is valid
2229  // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
2230  int LoOverflow = 0, HiOverflow = 0;
2231  Constant *LoBound = nullptr, *HiBound = nullptr;
2232 
2233  if (!DivIsSigned) { // udiv
2234  // e.g. X/5 op 3 --> [15, 20)
2235  LoBound = Prod;
2236  HiOverflow = LoOverflow = ProdOV;
2237  if (!HiOverflow) {
2238  // If this is not an exact divide, then many values in the range collapse
2239  // to the same result value.
2240  HiOverflow = addWithOverflow(HiBound, LoBound, RangeSize, false);
2241  }
2242  } else if (C2->isStrictlyPositive()) { // Divisor is > 0.
2243  if (C->isNullValue()) { // (X / pos) op 0
2244  // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
2245  LoBound = ConstantExpr::getNeg(SubOne(RangeSize));
2246  HiBound = RangeSize;
2247  } else if (C->isStrictlyPositive()) { // (X / pos) op pos
2248  LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
2249  HiOverflow = LoOverflow = ProdOV;
2250  if (!HiOverflow)
2251  HiOverflow = addWithOverflow(HiBound, Prod, RangeSize, true);
2252  } else { // (X / pos) op neg
2253  // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
2254  HiBound = AddOne(Prod);
2255  LoOverflow = HiOverflow = ProdOV ? -1 : 0;
2256  if (!LoOverflow) {
2257  Constant *DivNeg = ConstantExpr::getNeg(RangeSize);
2258  LoOverflow = addWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
2259  }
2260  }
2261  } else if (C2->isNegative()) { // Divisor is < 0.
2262  if (Div->isExact())
2263  RangeSize = ConstantExpr::getNeg(RangeSize);
2264  if (C->isNullValue()) { // (X / neg) op 0
2265  // e.g. X/-5 op 0 --> [-4, 5)
2266  LoBound = AddOne(RangeSize);
2267  HiBound = ConstantExpr::getNeg(RangeSize);
2268  if (HiBound == DivRHS) { // -INTMIN = INTMIN
2269  HiOverflow = 1; // [INTMIN+1, overflow)
2270  HiBound = nullptr; // e.g. X/INTMIN = 0 --> X > INTMIN
2271  }
2272  } else if (C->isStrictlyPositive()) { // (X / neg) op pos
2273  // e.g. X/-5 op 3 --> [-19, -14)
2274  HiBound = AddOne(Prod);
2275  HiOverflow = LoOverflow = ProdOV ? -1 : 0;
2276  if (!LoOverflow)
2277  LoOverflow = addWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
2278  } else { // (X / neg) op neg
2279  LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
2280  LoOverflow = HiOverflow = ProdOV;
2281  if (!HiOverflow)
2282  HiOverflow = subWithOverflow(HiBound, Prod, RangeSize, true);
2283  }
2284 
2285  // Dividing by a negative swaps the condition. LT <-> GT
2286  Pred = ICmpInst::getSwappedPredicate(Pred);
2287  }
2288 
2289  Value *X = Div->getOperand(0);
2290  switch (Pred) {
2291  default: llvm_unreachable("Unhandled icmp opcode!");
2292  case ICmpInst::ICMP_EQ:
2293  if (LoOverflow && HiOverflow)
2294  return replaceInstUsesWith(Cmp, Builder.getFalse());
2295  if (HiOverflow)
2296  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2297  ICmpInst::ICMP_UGE, X, LoBound);
2298  if (LoOverflow)
2299  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2300  ICmpInst::ICMP_ULT, X, HiBound);
2301  return replaceInstUsesWith(
2302  Cmp, insertRangeTest(X, LoBound->getUniqueInteger(),
2303  HiBound->getUniqueInteger(), DivIsSigned, true));
2304  case ICmpInst::ICMP_NE:
2305  if (LoOverflow && HiOverflow)
2306  return replaceInstUsesWith(Cmp, Builder.getTrue());
2307  if (HiOverflow)
2308  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
2309  ICmpInst::ICMP_ULT, X, LoBound);
2310  if (LoOverflow)
2311  return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
2312  ICmpInst::ICMP_UGE, X, HiBound);
2313  return replaceInstUsesWith(Cmp,
2314  insertRangeTest(X, LoBound->getUniqueInteger(),
2315  HiBound->getUniqueInteger(),
2316  DivIsSigned, false));
2317  case ICmpInst::ICMP_ULT:
2318  case ICmpInst::ICMP_SLT:
2319  if (LoOverflow == +1) // Low bound is greater than input range.
2320  return replaceInstUsesWith(Cmp, Builder.getTrue());
2321  if (LoOverflow == -1) // Low bound is less than input range.
2322  return replaceInstUsesWith(Cmp, Builder.getFalse());
2323  return new ICmpInst(Pred, X, LoBound);
2324  case ICmpInst::ICMP_UGT:
2325  case ICmpInst::ICMP_SGT:
2326  if (HiOverflow == +1) // High bound greater than input range.
2327  return replaceInstUsesWith(Cmp, Builder.getFalse());
2328  if (HiOverflow == -1) // High bound less than input range.
2329  return replaceInstUsesWith(Cmp, Builder.getTrue());
2330  if (Pred == ICmpInst::ICMP_UGT)
2331  return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
2332  return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
2333  }
2334 
2335  return nullptr;
2336 }
2337 
2338 /// Fold icmp (sub X, Y), C.
2339 Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp,
2340  BinaryOperator *Sub,
2341  const APInt *C) {
2342  Value *X = Sub->getOperand(0), *Y = Sub->getOperand(1);
2343  ICmpInst::Predicate Pred = Cmp.getPredicate();
2344 
2345  // The following transforms are only worth it if the only user of the subtract
2346  // is the icmp.
2347  if (!Sub->hasOneUse())
2348  return nullptr;
2349 
2350  if (Sub->hasNoSignedWrap()) {
2351  // (icmp sgt (sub nsw X, Y), -1) -> (icmp sge X, Y)
2352  if (Pred == ICmpInst::ICMP_SGT && C->isAllOnesValue())
2353  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
2354 
2355  // (icmp sgt (sub nsw X, Y), 0) -> (icmp sgt X, Y)
2356  if (Pred == ICmpInst::ICMP_SGT && C->isNullValue())
2357  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
2358 
2359  // (icmp slt (sub nsw X, Y), 0) -> (icmp slt X, Y)
2360  if (Pred == ICmpInst::ICMP_SLT && C->isNullValue())
2361  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
2362 
2363  // (icmp slt (sub nsw X, Y), 1) -> (icmp sle X, Y)
2364  if (Pred == ICmpInst::ICMP_SLT && C->isOneValue())
2365  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
2366  }
2367 
2368  const APInt *C2;
2369  if (!match(X, m_APInt(C2)))
2370  return nullptr;
2371 
2372  // C2 - Y <u C -> (Y | (C - 1)) == C2
2373  // iff (C2 & (C - 1)) == C - 1 and C is a power of 2
2374  if (Pred == ICmpInst::ICMP_ULT && C->isPowerOf2() &&
2375  (*C2 & (*C - 1)) == (*C - 1))
2376  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateOr(Y, *C - 1), X);
2377 
2378  // C2 - Y >u C -> (Y | C) != C2
2379  // iff C2 & C == C and C + 1 is a power of 2
2380  if (Pred == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() && (*C2 & *C) == *C)
2381  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateOr(Y, *C), X);
2382 
2383  return nullptr;
2384 }
2385 
2386 /// Fold icmp (add X, Y), C.
2387 Instruction *InstCombiner::foldICmpAddConstant(ICmpInst &Cmp,
2389  const APInt *C) {
2390  Value *Y = Add->getOperand(1);
2391  const APInt *C2;
2392  if (Cmp.isEquality() || !match(Y, m_APInt(C2)))
2393  return nullptr;
2394 
2395  // Fold icmp pred (add X, C2), C.
2396  Value *X = Add->getOperand(0);
2397  Type *Ty = Add->getType();
2398  CmpInst::Predicate Pred = Cmp.getPredicate();
2399 
2400  // If the add does not wrap, we can always adjust the compare by subtracting
2401  // the constants. Equality comparisons are handled elsewhere. SGE/SLE are
2402  // canonicalized to SGT/SLT.
2403  if (Add->hasNoSignedWrap() &&
2404  (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SLT)) {
2405  bool Overflow;
2406  APInt NewC = C->ssub_ov(*C2, Overflow);
2407  // If there is overflow, the result must be true or false.
2408  // TODO: Can we assert there is no overflow because InstSimplify always
2409  // handles those cases?
2410  if (!Overflow)
2411  // icmp Pred (add nsw X, C2), C --> icmp Pred X, (C - C2)
2412  return new ICmpInst(Pred, X, ConstantInt::get(Ty, NewC));
2413  }
2414 
2415  auto CR = ConstantRange::makeExactICmpRegion(Pred, *C).subtract(*C2);
2416  const APInt &Upper = CR.getUpper();
2417  const APInt &Lower = CR.getLower();
2418  if (Cmp.isSigned()) {
2419  if (Lower.isSignMask())
2420  return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantInt::get(Ty, Upper));
2421  if (Upper.isSignMask())
2422  return new ICmpInst(ICmpInst::ICMP_SGE, X, ConstantInt::get(Ty, Lower));
2423  } else {
2424  if (Lower.isMinValue())
2425  return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantInt::get(Ty, Upper));
2426  if (Upper.isMinValue())
2427  return new ICmpInst(ICmpInst::ICMP_UGE, X, ConstantInt::get(Ty, Lower));
2428  }
2429 
2430  if (!Add->hasOneUse())
2431  return nullptr;
2432 
2433  // X+C <u C2 -> (X & -C2) == C
2434  // iff C & (C2-1) == 0
2435  // C2 is a power of 2
2436  if (Pred == ICmpInst::ICMP_ULT && C->isPowerOf2() && (*C2 & (*C - 1)) == 0)
2437  return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -(*C)),
2438  ConstantExpr::getNeg(cast<Constant>(Y)));
2439 
2440  // X+C >u C2 -> (X & ~C2) != C
2441  // iff C & C2 == 0
2442  // C2+1 is a power of 2
2443  if (Pred == ICmpInst::ICMP_UGT && (*C + 1).isPowerOf2() && (*C2 & *C) == 0)
2444  return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, ~(*C)),
2445  ConstantExpr::getNeg(cast<Constant>(Y)));
2446 
2447  return nullptr;
2448 }
2449 
2450 bool InstCombiner::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
2451  Value *&RHS, ConstantInt *&Less,
2452  ConstantInt *&Equal,
2453  ConstantInt *&Greater) {
2454  // TODO: Generalize this to work with other comparison idioms or ensure
2455  // they get canonicalized into this form.
2456 
2457  // select i1 (a == b), i32 Equal, i32 (select i1 (a < b), i32 Less, i32
2458  // Greater), where Equal, Less and Greater are placeholders for any three
2459  // constants.
2460  ICmpInst::Predicate PredA, PredB;
2461  if (match(SI->getTrueValue(), m_ConstantInt(Equal)) &&
2462  match(SI->getCondition(), m_ICmp(PredA, m_Value(LHS), m_Value(RHS))) &&
2463  PredA == ICmpInst::ICMP_EQ &&
2464  match(SI->getFalseValue(),
2465  m_Select(m_ICmp(PredB, m_Specific(LHS), m_Specific(RHS)),
2466  m_ConstantInt(Less), m_ConstantInt(Greater))) &&
2467  PredB == ICmpInst::ICMP_SLT) {
2468  return true;
2469  }
2470  return false;
2471 }
2472 
2473 Instruction *InstCombiner::foldICmpSelectConstant(ICmpInst &Cmp,
2475  ConstantInt *C) {
2476 
2477  assert(C && "Cmp RHS should be a constant int!");
2478  // If we're testing a constant value against the result of a three way
2479  // comparison, the result can be expressed directly in terms of the
2480  // original values being compared. Note: We could possibly be more
2481  // aggressive here and remove the hasOneUse test. The original select is
2482  // really likely to simplify or sink when we remove a test of the result.
2483  Value *OrigLHS, *OrigRHS;
2484  ConstantInt *C1LessThan, *C2Equal, *C3GreaterThan;
2485  if (Cmp.hasOneUse() &&
2486  matchThreeWayIntCompare(cast<SelectInst>(Select), OrigLHS, OrigRHS,
2487  C1LessThan, C2Equal, C3GreaterThan)) {
2488  assert(C1LessThan && C2Equal && C3GreaterThan);
2489 
2490  bool TrueWhenLessThan =
2491  ConstantExpr::getCompare(Cmp.getPredicate(), C1LessThan, C)
2492  ->isAllOnesValue();
2493  bool TrueWhenEqual =
2494  ConstantExpr::getCompare(Cmp.getPredicate(), C2Equal, C)
2495  ->isAllOnesValue();
2496  bool TrueWhenGreaterThan =
2497  ConstantExpr::getCompare(Cmp.getPredicate(), C3GreaterThan, C)
2498  ->isAllOnesValue();
2499 
2500  // This generates the new instruction that will replace the original Cmp
2501  // Instruction. Instead of enumerating the various combinations when
2502  // TrueWhenLessThan, TrueWhenEqual and TrueWhenGreaterThan are true versus
2503  // false, we rely on chaining of ORs and future passes of InstCombine to
2504  // simplify the OR further (i.e. a s< b || a == b becomes a s<= b).
2505 
2506  // When none of the three constants satisfy the predicate for the RHS (C),
2507  // the entire original Cmp can be simplified to a false.
2508  Value *Cond = Builder.getFalse();
2509  if (TrueWhenLessThan)
2510  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SLT, OrigLHS, OrigRHS));
2511  if (TrueWhenEqual)
2512  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_EQ, OrigLHS, OrigRHS));
2513  if (TrueWhenGreaterThan)
2514  Cond = Builder.CreateOr(Cond, Builder.CreateICmp(ICmpInst::ICMP_SGT, OrigLHS, OrigRHS));
2515 
2516  return replaceInstUsesWith(Cmp, Cond);
2517  }
2518  return nullptr;
2519 }
2520 
2521 /// Try to fold integer comparisons with a constant operand: icmp Pred X, C
2522 /// where X is some kind of instruction.
2523 Instruction *InstCombiner::foldICmpInstWithConstant(ICmpInst &Cmp) {
2524  const APInt *C;
2525  if (!match(Cmp.getOperand(1), m_APInt(C)))
2526  return nullptr;
2527 
2528  BinaryOperator *BO;
2529  if (match(Cmp.getOperand(0), m_BinOp(BO))) {
2530  switch (BO->getOpcode()) {
2531  case Instruction::Xor:
2532  if (Instruction *I = foldICmpXorConstant(Cmp, BO, C))
2533  return I;
2534  break;
2535  case Instruction::And:
2536  if (Instruction *I = foldICmpAndConstant(Cmp, BO, C))
2537  return I;
2538  break;
2539  case Instruction::Or:
2540  if (Instruction *I = foldICmpOrConstant(Cmp, BO, C))
2541  return I;
2542  break;
2543  case Instruction::Mul:
2544  if (Instruction *I = foldICmpMulConstant(Cmp, BO, C))
2545  return I;
2546  break;
2547  case Instruction::Shl:
2548  if (Instruction *I = foldICmpShlConstant(Cmp, BO, C))
2549  return I;
2550  break;
2551  case Instruction::LShr:
2552  case Instruction::AShr:
2553  if (Instruction *I = foldICmpShrConstant(Cmp, BO, C))
2554  return I;
2555  break;
2556  case Instruction::UDiv:
2557  if (Instruction *I = foldICmpUDivConstant(Cmp, BO, C))
2558  return I;
2560  case Instruction::SDiv:
2561  if (Instruction *I = foldICmpDivConstant(Cmp, BO, C))
2562  return I;
2563  break;
2564  case Instruction::Sub:
2565  if (Instruction *I = foldICmpSubConstant(Cmp, BO, C))
2566  return I;
2567  break;
2568  case Instruction::Add:
2569  if (Instruction *I = foldICmpAddConstant(Cmp, BO, C))
2570  return I;
2571  break;
2572  default:
2573  break;
2574  }
2575  // TODO: These folds could be refactored to be part of the above calls.
2576  if (Instruction *I = foldICmpBinOpEqualityWithConstant(Cmp, BO, C))
2577  return I;
2578  }
2579 
2580  // Match against CmpInst LHS being instructions other than binary operators.
2581  Instruction *LHSI;
2582  if (match(Cmp.getOperand(0), m_Instruction(LHSI))) {
2583  switch (LHSI->getOpcode()) {
2584  case Instruction::Select:
2585  {
2586  // For now, we only support constant integers while folding the
2587  // ICMP(SELECT)) pattern. We can extend this to support vector of integers
2588  // similar to the cases handled by binary ops above.
2589  if (ConstantInt *ConstRHS = dyn_cast<ConstantInt>(Cmp.getOperand(1)))
2590  if (Instruction *I = foldICmpSelectConstant(Cmp, LHSI, ConstRHS))
2591  return I;
2592  break;
2593  }
2594  case Instruction::Trunc:
2595  if (Instruction *I = foldICmpTruncConstant(Cmp, LHSI, C))
2596  return I;
2597  break;
2598  default:
2599  break;
2600  }
2601  }
2602 
2603  if (Instruction *I = foldICmpIntrinsicWithConstant(Cmp, C))
2604  return I;
2605 
2606  return nullptr;
2607 }
2608 
2609 /// Fold an icmp equality instruction with binary operator LHS and constant RHS:
2610 /// icmp eq/ne BO, C.
2611 Instruction *InstCombiner::foldICmpBinOpEqualityWithConstant(ICmpInst &Cmp,
2612  BinaryOperator *BO,
2613  const APInt *C) {
2614  // TODO: Some of these folds could work with arbitrary constants, but this
2615  // function is limited to scalar and vector splat constants.
2616  if (!Cmp.isEquality())
2617  return nullptr;
2618 
2619  ICmpInst::Predicate Pred = Cmp.getPredicate();
2620  bool isICMP_NE = Pred == ICmpInst::ICMP_NE;
2621  Constant *RHS = cast<Constant>(Cmp.getOperand(1));
2622  Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
2623 
2624  switch (BO->getOpcode()) {
2625  case Instruction::SRem:
2626  // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
2627  if (C->isNullValue() && BO->hasOneUse()) {
2628  const APInt *BOC;
2629  if (match(BOp1, m_APInt(BOC)) && BOC->sgt(1) && BOC->isPowerOf2()) {
2630  Value *NewRem = Builder.CreateURem(BOp0, BOp1, BO->getName());
2631  return new ICmpInst(Pred, NewRem,
2633  }
2634  }
2635  break;
2636  case Instruction::Add: {
2637  // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
2638  const APInt *BOC;
2639  if (match(BOp1, m_APInt(BOC))) {
2640  if (BO->hasOneUse()) {
2641  Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
2642  return new ICmpInst(Pred, BOp0, SubC);
2643  }
2644  } else if (C->isNullValue()) {
2645  // Replace ((add A, B) != 0) with (A != -B) if A or B is
2646  // efficiently invertible, or if the add has just this one use.
2647  if (Value *NegVal = dyn_castNegVal(BOp1))
2648  return new ICmpInst(Pred, BOp0, NegVal);
2649  if (Value *NegVal = dyn_castNegVal(BOp0))
2650  return new ICmpInst(Pred, NegVal, BOp1);
2651  if (BO->hasOneUse()) {
2652  Value *Neg = Builder.CreateNeg(BOp1);
2653  Neg->takeName(BO);
2654  return new ICmpInst(Pred, BOp0, Neg);
2655  }
2656  }
2657  break;
2658  }
2659  case Instruction::Xor:
2660  if (BO->hasOneUse()) {
2661  if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
2662  // For the xor case, we can xor two constants together, eliminating
2663  // the explicit xor.
2664  return new ICmpInst(Pred, BOp0, ConstantExpr::getXor(RHS, BOC));
2665  } else if (C->isNullValue()) {
2666  // Replace ((xor A, B) != 0) with (A != B)
2667  return new ICmpInst(Pred, BOp0, BOp1);
2668  }
2669  }
2670  break;
2671  case Instruction::Sub:
2672  if (BO->hasOneUse()) {
2673  const APInt *BOC;
2674  if (match(BOp0, m_APInt(BOC))) {
2675  // Replace ((sub BOC, B) != C) with (B != BOC-C).
2676  Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
2677  return new ICmpInst(Pred, BOp1, SubC);
2678  } else if (C->isNullValue()) {
2679  // Replace ((sub A, B) != 0) with (A != B).
2680  return new ICmpInst(Pred, BOp0, BOp1);
2681  }
2682  }
2683  break;
2684  case Instruction::Or: {
2685  const APInt *BOC;
2686  if (match(BOp1, m_APInt(BOC)) && BO->hasOneUse() && RHS->isAllOnesValue()) {
2687  // Comparing if all bits outside of a constant mask are set?
2688  // Replace (X | C) == -1 with (X & ~C) == ~C.
2689  // This removes the -1 constant.
2690  Constant *NotBOC = ConstantExpr::getNot(cast<Constant>(BOp1));
2691  Value *And = Builder.CreateAnd(BOp0, NotBOC);
2692  return new ICmpInst(Pred, And, NotBOC);
2693  }
2694  break;
2695  }
2696  case Instruction::And: {
2697  const APInt *BOC;
2698  if (match(BOp1, m_APInt(BOC))) {
2699  // If we have ((X & C) == C), turn it into ((X & C) != 0).
2700  if (C == BOC && C->isPowerOf2())
2701  return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
2702  BO, Constant::getNullValue(RHS->getType()));
2703 
2704  // Don't perform the following transforms if the AND has multiple uses
2705  if (!BO->hasOneUse())
2706  break;
2707 
2708  // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
2709  if (BOC->isSignMask()) {
2710  Constant *Zero = Constant::getNullValue(BOp0->getType());
2711  auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
2712  return new ICmpInst(NewPred, BOp0, Zero);
2713  }
2714 
2715  // ((X & ~7) == 0) --> X < 8
2716  if (C->isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
2717  Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
2718  auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
2719  return new ICmpInst(NewPred, BOp0, NegBOC);
2720  }
2721  }
2722  break;
2723  }
2724  case Instruction::Mul:
2725  if (C->isNullValue() && BO->hasNoSignedWrap()) {
2726  const APInt *BOC;
2727  if (match(BOp1, m_APInt(BOC)) && !BOC->isNullValue()) {
2728  // The trivial case (mul X, 0) is handled by InstSimplify.
2729  // General case : (mul X, C) != 0 iff X != 0
2730  // (mul X, C) == 0 iff X == 0
2731  return new ICmpInst(Pred, BOp0, Constant::getNullValue(RHS->getType()));
2732  }
2733  }
2734  break;
2735  case Instruction::UDiv:
2736  if (C->isNullValue()) {
2737  // (icmp eq/ne (udiv A, B), 0) -> (icmp ugt/ule i32 B, A)
2738  auto NewPred = isICMP_NE ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT;
2739  return new ICmpInst(NewPred, BOp1, BOp0);
2740  }
2741  break;
2742  default:
2743  break;
2744  }
2745  return nullptr;
2746 }
2747 
2748 /// Fold an icmp with LLVM intrinsic and constant operand: icmp Pred II, C.
2749 Instruction *InstCombiner::foldICmpIntrinsicWithConstant(ICmpInst &Cmp,
2750  const APInt *C) {
2752  if (!II || !Cmp.isEquality())
2753  return nullptr;
2754 
2755  // Handle icmp {eq|ne} <intrinsic>, Constant.
2756  Type *Ty = II->getType();
2757  switch (II->getIntrinsicID()) {
2758  case Intrinsic::bswap:
2759  Worklist.Add(II);
2760  Cmp.setOperand(0, II->getArgOperand(0));
2761  Cmp.setOperand(1, ConstantInt::get(Ty, C->byteSwap()));
2762  return &Cmp;
2763 
2764  case Intrinsic::ctlz:
2765  case Intrinsic::cttz:
2766  // ctz(A) == bitwidth(A) -> A == 0 and likewise for !=
2767  if (*C == C->getBitWidth()) {
2768  Worklist.Add(II);
2769  Cmp.setOperand(0, II->getArgOperand(0));
2771  return &Cmp;
2772  }
2773  break;
2774 
2775  case Intrinsic::ctpop: {
2776  // popcount(A) == 0 -> A == 0 and likewise for !=
2777  // popcount(A) == bitwidth(A) -> A == -1 and likewise for !=
2778  bool IsZero = C->isNullValue();
2779  if (IsZero || *C == C->getBitWidth()) {
2780  Worklist.Add(II);
2781  Cmp.setOperand(0, II->getArgOperand(0));
2782  auto *NewOp =
2784  Cmp.setOperand(1, NewOp);
2785  return &Cmp;
2786  }
2787  break;
2788  }
2789  default:
2790  break;
2791  }
2792 
2793  return nullptr;
2794 }
2795 
2796 /// Handle icmp with constant (but not simple integer constant) RHS.
2797 Instruction *InstCombiner::foldICmpInstWithConstantNotInt(ICmpInst &I) {
2798  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2799  Constant *RHSC = dyn_cast<Constant>(Op1);
2800  Instruction *LHSI = dyn_cast<Instruction>(Op0);
2801  if (!RHSC || !LHSI)
2802  return nullptr;
2803 
2804  switch (LHSI->getOpcode()) {
2805  case Instruction::GetElementPtr:
2806  // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2807  if (RHSC->isNullValue() &&
2808  cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2809  return new ICmpInst(
2810  I.getPredicate(), LHSI->getOperand(0),
2811  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2812  break;
2813  case Instruction::PHI:
2814  // Only fold icmp into the PHI if the phi and icmp are in the same
2815  // block. If in the same block, we're encouraging jump threading. If
2816  // not, we are just pessimizing the code by making an i1 phi.
2817  if (LHSI->getParent() == I.getParent())
2818  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
2819  return NV;
2820  break;
2821  case Instruction::Select: {
2822  // If either operand of the select is a constant, we can fold the
2823  // comparison into the select arms, which will cause one to be
2824  // constant folded and the select turned into a bitwise or.
2825  Value *Op1 = nullptr, *Op2 = nullptr;
2826  ConstantInt *CI = nullptr;
2827  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2828  Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2829  CI = dyn_cast<ConstantInt>(Op1);
2830  }
2831  if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2832  Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2833  CI = dyn_cast<ConstantInt>(Op2);
2834  }
2835 
2836  // We only want to perform this transformation if it will not lead to
2837  // additional code. This is true if either both sides of the select
2838  // fold to a constant (in which case the icmp is replaced with a select
2839  // which will usually simplify) or this is the only user of the
2840  // select (in which case we are trading a select+icmp for a simpler
2841  // select+icmp) or all uses of the select can be replaced based on
2842  // dominance information ("Global cases").
2843  bool Transform = false;
2844  if (Op1 && Op2)
2845  Transform = true;
2846  else if (Op1 || Op2) {
2847  // Local case
2848  if (LHSI->hasOneUse())
2849  Transform = true;
2850  // Global cases
2851  else if (CI && !CI->isZero())
2852  // When Op1 is constant try replacing select with second operand.
2853  // Otherwise Op2 is constant and try replacing select with first
2854  // operand.
2855  Transform =
2856  replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, Op1 ? 2 : 1);
2857  }
2858  if (Transform) {
2859  if (!Op1)
2860  Op1 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC,
2861  I.getName());
2862  if (!Op2)
2863  Op2 = Builder.CreateICmp(I.getPredicate(), LHSI->getOperand(2), RHSC,
2864  I.getName());
2865  return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2866  }
2867  break;
2868  }
2869  case Instruction::IntToPtr:
2870  // icmp pred inttoptr(X), null -> icmp pred X, 0
2871  if (RHSC->isNullValue() &&
2872  DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType())
2873  return new ICmpInst(
2874  I.getPredicate(), LHSI->getOperand(0),
2875  Constant::getNullValue(LHSI->getOperand(0)->getType()));
2876  break;
2877 
2878  case Instruction::Load:
2879  // Try to optimize things like "A[i] > 4" to index computations.
2880  if (GetElementPtrInst *GEP =
2881  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2882  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2883  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2884  !cast<LoadInst>(LHSI)->isVolatile())
2885  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
2886  return Res;
2887  }
2888  break;
2889  }
2890 
2891  return nullptr;
2892 }
2893 
2894 /// Try to fold icmp (binop), X or icmp X, (binop).
2895 /// TODO: A large part of this logic is duplicated in InstSimplify's
2896 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
2897 /// duplication.
2898 Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
2899  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2900 
2901  // Special logic for binary operators.
2902  BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2903  BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2904  if (!BO0 && !BO1)
2905  return nullptr;
2906 
2907  const CmpInst::Predicate Pred = I.getPredicate();
2908  bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2909  if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2910  NoOp0WrapProblem =
2911  ICmpInst::isEquality(Pred) ||
2912  (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2913  (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2914  if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2915  NoOp1WrapProblem =
2916  ICmpInst::isEquality(Pred) ||
2917  (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2918  (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2919 
2920  // Analyze the case when either Op0 or Op1 is an add instruction.
2921  // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2922  Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2923  if (BO0 && BO0->getOpcode() == Instruction::Add) {
2924  A = BO0->getOperand(0);
2925  B = BO0->getOperand(1);
2926  }
2927  if (BO1 && BO1->getOpcode() == Instruction::Add) {
2928  C = BO1->getOperand(0);
2929  D = BO1->getOperand(1);
2930  }
2931 
2932  // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2933  if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2934  return new ICmpInst(Pred, A == Op1 ? B : A,
2935  Constant::getNullValue(Op1->getType()));
2936 
2937  // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2938  if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2939  return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2940  C == Op0 ? D : C);
2941 
2942  // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2943  if (A && C && (A == C || A == D || B == C || B == D) && NoOp0WrapProblem &&
2944  NoOp1WrapProblem &&
2945  // Try not to increase register pressure.
2946  BO0->hasOneUse() && BO1->hasOneUse()) {
2947  // Determine Y and Z in the form icmp (X+Y), (X+Z).
2948  Value *Y, *Z;
2949  if (A == C) {
2950  // C + B == C + D -> B == D
2951  Y = B;
2952  Z = D;
2953  } else if (A == D) {
2954  // D + B == C + D -> B == C
2955  Y = B;
2956  Z = C;
2957  } else if (B == C) {
2958  // A + C == C + D -> A == D
2959  Y = A;
2960  Z = D;
2961  } else {
2962  assert(B == D);
2963  // A + D == C + D -> A == C
2964  Y = A;
2965  Z = C;
2966  }
2967  return new ICmpInst(Pred, Y, Z);
2968  }
2969 
2970  // icmp slt (X + -1), Y -> icmp sle X, Y
2971  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2972  match(B, m_AllOnes()))
2973  return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2974 
2975  // icmp sge (X + -1), Y -> icmp sgt X, Y
2976  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2977  match(B, m_AllOnes()))
2978  return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2979 
2980  // icmp sle (X + 1), Y -> icmp slt X, Y
2981  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && match(B, m_One()))
2982  return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2983 
2984  // icmp sgt (X + 1), Y -> icmp sge X, Y
2985  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && match(B, m_One()))
2986  return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2987 
2988  // icmp sgt X, (Y + -1) -> icmp sge X, Y
2989  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGT &&
2990  match(D, m_AllOnes()))
2991  return new ICmpInst(CmpInst::ICMP_SGE, Op0, C);
2992 
2993  // icmp sle X, (Y + -1) -> icmp slt X, Y
2994  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLE &&
2995  match(D, m_AllOnes()))
2996  return new ICmpInst(CmpInst::ICMP_SLT, Op0, C);
2997 
2998  // icmp sge X, (Y + 1) -> icmp sgt X, Y
2999  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SGE && match(D, m_One()))
3000  return new ICmpInst(CmpInst::ICMP_SGT, Op0, C);
3001 
3002  // icmp slt X, (Y + 1) -> icmp sle X, Y
3003  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_SLT && match(D, m_One()))
3004  return new ICmpInst(CmpInst::ICMP_SLE, Op0, C);
3005 
3006  // TODO: The subtraction-related identities shown below also hold, but
3007  // canonicalization from (X -nuw 1) to (X + -1) means that the combinations
3008  // wouldn't happen even if they were implemented.
3009  //
3010  // icmp ult (X - 1), Y -> icmp ule X, Y
3011  // icmp uge (X - 1), Y -> icmp ugt X, Y
3012  // icmp ugt X, (Y - 1) -> icmp uge X, Y
3013  // icmp ule X, (Y - 1) -> icmp ult X, Y
3014 
3015  // icmp ule (X + 1), Y -> icmp ult X, Y
3016  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_ULE && match(B, m_One()))
3017  return new ICmpInst(CmpInst::ICMP_ULT, A, Op1);
3018 
3019  // icmp ugt (X + 1), Y -> icmp uge X, Y
3020  if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_UGT && match(B, m_One()))
3021  return new ICmpInst(CmpInst::ICMP_UGE, A, Op1);
3022 
3023  // icmp uge X, (Y + 1) -> icmp ugt X, Y
3024  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_UGE && match(D, m_One()))
3025  return new ICmpInst(CmpInst::ICMP_UGT, Op0, C);
3026 
3027  // icmp ult X, (Y + 1) -> icmp ule X, Y
3028  if (C && NoOp1WrapProblem && Pred == CmpInst::ICMP_ULT && match(D, m_One()))
3029  return new ICmpInst(CmpInst::ICMP_ULE, Op0, C);
3030 
3031  // if C1 has greater magnitude than C2:
3032  // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
3033  // s.t. C3 = C1 - C2
3034  //
3035  // if C2 has greater magnitude than C1:
3036  // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
3037  // s.t. C3 = C2 - C1
3038  if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
3039  (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
3040  if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
3041  if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
3042  const APInt &AP1 = C1->getValue();
3043  const APInt &AP2 = C2->getValue();
3044  if (AP1.isNegative() == AP2.isNegative()) {
3045  APInt AP1Abs = C1->getValue().abs();
3046  APInt AP2Abs = C2->getValue().abs();
3047  if (AP1Abs.uge(AP2Abs)) {
3048  ConstantInt *C3 = Builder.getInt(AP1 - AP2);
3049  Value *NewAdd = Builder.CreateNSWAdd(A, C3);
3050  return new ICmpInst(Pred, NewAdd, C);
3051  } else {
3052  ConstantInt *C3 = Builder.getInt(AP2 - AP1);
3053  Value *NewAdd = Builder.CreateNSWAdd(C, C3);
3054  return new ICmpInst(Pred, A, NewAdd);
3055  }
3056  }
3057  }
3058 
3059  // Analyze the case when either Op0 or Op1 is a sub instruction.
3060  // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
3061  A = nullptr;
3062  B = nullptr;
3063  C = nullptr;
3064  D = nullptr;
3065  if (BO0 && BO0->getOpcode() == Instruction::Sub) {
3066  A = BO0->getOperand(0);
3067  B = BO0->getOperand(1);
3068  }
3069  if (BO1 && BO1->getOpcode() == Instruction::Sub) {
3070  C = BO1->getOperand(0);
3071  D = BO1->getOperand(1);
3072  }
3073 
3074  // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
3075  if (A == Op1 && NoOp0WrapProblem)
3076  return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
3077 
3078  // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
3079  if (C == Op0 && NoOp1WrapProblem)
3080  return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
3081 
3082  // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
3083  if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
3084  // Try not to increase register pressure.
3085  BO0->hasOneUse() && BO1->hasOneUse())
3086  return new ICmpInst(Pred, A, C);
3087 
3088  // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
3089  if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
3090  // Try not to increase register pressure.
3091  BO0->hasOneUse() && BO1->hasOneUse())
3092  return new ICmpInst(Pred, D, B);
3093 
3094  // icmp (0-X) < cst --> x > -cst
3095  if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) {
3096  Value *X;
3097  if (match(BO0, m_Neg(m_Value(X))))
3098  if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3099  if (!RHSC->isMinValue(/*isSigned=*/true))
3100  return new ICmpInst(I.getSwappedPredicate(), X,
3101  ConstantExpr::getNeg(RHSC));
3102  }
3103 
3104  BinaryOperator *SRem = nullptr;
3105  // icmp (srem X, Y), Y
3106  if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
3107  SRem = BO0;
3108  // icmp Y, (srem X, Y)
3109  else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
3110  Op0 == BO1->getOperand(1))
3111  SRem = BO1;
3112  if (SRem) {
3113  // We don't check hasOneUse to avoid increasing register pressure because
3114  // the value we use is the same value this instruction was already using.
3115  switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
3116  default:
3117  break;
3118  case ICmpInst::ICMP_EQ:
3119  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
3120  case ICmpInst::ICMP_NE:
3121  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
3122  case ICmpInst::ICMP_SGT:
3123  case ICmpInst::ICMP_SGE:
3124  return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
3126  case ICmpInst::ICMP_SLT:
3127  case ICmpInst::ICMP_SLE:
3128  return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
3129  Constant::getNullValue(SRem->getType()));
3130  }
3131  }
3132 
3133  if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && BO0->hasOneUse() &&
3134  BO1->hasOneUse() && BO0->getOperand(1) == BO1->getOperand(1)) {
3135  switch (BO0->getOpcode()) {
3136  default:
3137  break;
3138  case Instruction::Add:
3139  case Instruction::Sub:
3140  case Instruction::Xor: {
3141  if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3142  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3143 
3144  const APInt *C;
3145  if (match(BO0->getOperand(1), m_APInt(C))) {
3146  // icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
3147  if (C->isSignMask()) {
3148  ICmpInst::Predicate NewPred =
3150  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3151  }
3152 
3153  // icmp u/s (a ^ maxsignval), (b ^ maxsignval) --> icmp s/u' a, b
3154  if (BO0->getOpcode() == Instruction::Xor && C->isMaxSignedValue()) {
3155  ICmpInst::Predicate NewPred =
3157  NewPred = I.getSwappedPredicate(NewPred);
3158  return new ICmpInst(NewPred, BO0->getOperand(0), BO1->getOperand(0));
3159  }
3160  }
3161  break;
3162  }
3163  case Instruction::Mul: {
3164  if (!I.isEquality())
3165  break;
3166 
3167  const APInt *C;
3168  if (match(BO0->getOperand(1), m_APInt(C)) && !C->isNullValue() &&
3169  !C->isOneValue()) {
3170  // icmp eq/ne (X * C), (Y * C) --> icmp (X & Mask), (Y & Mask)
3171  // Mask = -1 >> count-trailing-zeros(C).
3172  if (unsigned TZs = C->countTrailingZeros()) {
3174  BO0->getType(),
3175  APInt::getLowBitsSet(C->getBitWidth(), C->getBitWidth() - TZs));
3176  Value *And1 = Builder.CreateAnd(BO0->getOperand(0), Mask);
3177  Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
3178  return new ICmpInst(Pred, And1, And2);
3179  }
3180  // If there are no trailing zeros in the multiplier, just eliminate
3181  // the multiplies (no masking is needed):
3182  // icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
3183  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3184  }
3185  break;
3186  }
3187  case Instruction::UDiv:
3188  case Instruction::LShr:
3189  if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
3190  break;
3191  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3192 
3193  case Instruction::SDiv:
3194  if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
3195  break;
3196  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3197 
3198  case Instruction::AShr:
3199  if (!BO0->isExact() || !BO1->isExact())
3200  break;
3201  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3202 
3203  case Instruction::Shl: {
3204  bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3205  bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3206  if (!NUW && !NSW)
3207  break;
3208  if (!NSW && I.isSigned())
3209  break;
3210  return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
3211  }
3212  }
3213  }
3214 
3215  if (BO0) {
3216  // Transform A & (L - 1) `ult` L --> L != 0
3217  auto LSubOne = m_Add(m_Specific(Op1), m_AllOnes());
3218  auto BitwiseAnd = m_c_And(m_Value(), LSubOne);
3219 
3220  if (match(BO0, BitwiseAnd) && Pred == ICmpInst::ICMP_ULT) {
3221  auto *Zero = Constant::getNullValue(BO0->getType());
3222  return new ICmpInst(ICmpInst::ICMP_NE, Op1, Zero);
3223  }
3224  }
3225 
3226  return nullptr;
3227 }
3228 
3229 /// Fold icmp Pred min|max(X, Y), X.
3231  ICmpInst::Predicate Pred = Cmp.getPredicate();
3232  Value *Op0 = Cmp.getOperand(0);
3233  Value *X = Cmp.getOperand(1);
3234 
3235  // Canonicalize minimum or maximum operand to LHS of the icmp.
3236  if (match(X, m_c_SMin(m_Specific(Op0), m_Value())) ||
3237  match(X, m_c_SMax(m_Specific(Op0), m_Value())) ||
3238  match(X, m_c_UMin(m_Specific(Op0), m_Value())) ||
3239  match(X, m_c_UMax(m_Specific(Op0), m_Value()))) {
3240  std::swap(Op0, X);
3241  Pred = Cmp.getSwappedPredicate();
3242  }
3243 
3244  Value *Y;
3245  if (match(Op0, m_c_SMin(m_Specific(X), m_Value(Y)))) {
3246  // smin(X, Y) == X --> X s<= Y
3247  // smin(X, Y) s>= X --> X s<= Y
3248  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SGE)
3249  return new ICmpInst(ICmpInst::ICMP_SLE, X, Y);
3250 
3251  // smin(X, Y) != X --> X s> Y
3252  // smin(X, Y) s< X --> X s> Y
3253  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SLT)
3254  return new ICmpInst(ICmpInst::ICMP_SGT, X, Y);
3255 
3256  // These cases should be handled in InstSimplify:
3257  // smin(X, Y) s<= X --> true
3258  // smin(X, Y) s> X --> false
3259  return nullptr;
3260  }
3261 
3262  if (match(Op0, m_c_SMax(m_Specific(X), m_Value(Y)))) {
3263  // smax(X, Y) == X --> X s>= Y
3264  // smax(X, Y) s<= X --> X s>= Y
3265  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_SLE)
3266  return new ICmpInst(ICmpInst::ICMP_SGE, X, Y);
3267 
3268  // smax(X, Y) != X --> X s< Y
3269  // smax(X, Y) s> X --> X s< Y
3270  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_SGT)
3271  return new ICmpInst(ICmpInst::ICMP_SLT, X, Y);
3272 
3273  // These cases should be handled in InstSimplify:
3274  // smax(X, Y) s>= X --> true
3275  // smax(X, Y) s< X --> false
3276  return nullptr;
3277  }
3278 
3279  if (match(Op0, m_c_UMin(m_Specific(X), m_Value(Y)))) {
3280  // umin(X, Y) == X --> X u<= Y
3281  // umin(X, Y) u>= X --> X u<= Y
3282  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_UGE)
3283  return new ICmpInst(ICmpInst::ICMP_ULE, X, Y);
3284 
3285  // umin(X, Y) != X --> X u> Y
3286  // umin(X, Y) u< X --> X u> Y
3287  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_ULT)
3288  return new ICmpInst(ICmpInst::ICMP_UGT, X, Y);
3289 
3290  // These cases should be handled in InstSimplify:
3291  // umin(X, Y) u<= X --> true
3292  // umin(X, Y) u> X --> false
3293  return nullptr;
3294  }
3295 
3296  if (match(Op0, m_c_UMax(m_Specific(X), m_Value(Y)))) {
3297  // umax(X, Y) == X --> X u>= Y
3298  // umax(X, Y) u<= X --> X u>= Y
3299  if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_ULE)
3300  return new ICmpInst(ICmpInst::ICMP_UGE, X, Y);
3301 
3302  // umax(X, Y) != X --> X u< Y
3303  // umax(X, Y) u> X --> X u< Y
3304  if (Pred == CmpInst::ICMP_NE || Pred == CmpInst::ICMP_UGT)
3305  return new ICmpInst(ICmpInst::ICMP_ULT, X, Y);
3306 
3307  // These cases should be handled in InstSimplify:
3308  // umax(X, Y) u>= X --> true
3309  // umax(X, Y) u< X --> false
3310  return nullptr;
3311  }
3312 
3313  return nullptr;
3314 }
3315 
3316 Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
3317  if (!I.isEquality())
3318  return nullptr;
3319 
3320  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3321  const CmpInst::Predicate Pred = I.getPredicate();
3322  Value *A, *B, *C, *D;
3323  if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3324  if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3325  Value *OtherVal = A == Op1 ? B : A;
3326  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3327  }
3328 
3329  if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3330  // A^c1 == C^c2 --> A == C^(c1^c2)
3331  ConstantInt *C1, *C2;
3332  if (match(B, m_ConstantInt(C1)) && match(D, m_ConstantInt(C2)) &&
3333  Op1->hasOneUse()) {
3334  Constant *NC = Builder.getInt(C1->getValue() ^ C2->getValue());
3335  Value *Xor = Builder.CreateXor(C, NC);
3336  return new ICmpInst(Pred, A, Xor);
3337  }
3338 
3339  // A^B == A^D -> B == D
3340  if (A == C)
3341  return new ICmpInst(Pred, B, D);
3342  if (A == D)
3343  return new ICmpInst(Pred, B, C);
3344  if (B == C)
3345  return new ICmpInst(Pred, A, D);
3346  if (B == D)
3347  return new ICmpInst(Pred, A, C);
3348  }
3349  }
3350 
3351  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) {
3352  // A == (A^B) -> B == 0
3353  Value *OtherVal = A == Op0 ? B : A;
3354  return new ICmpInst(Pred, OtherVal, Constant::getNullValue(A->getType()));
3355  }
3356 
3357  // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3358  if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3359  match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3360  Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3361 
3362  if (A == C) {
3363  X = B;
3364  Y = D;
3365  Z = A;
3366  } else if (A == D) {
3367  X = B;
3368  Y = C;
3369  Z = A;
3370  } else if (B == C) {
3371  X = A;
3372  Y = D;
3373  Z = B;
3374  } else if (B == D) {
3375  X = A;
3376  Y = C;
3377  Z = B;
3378  }
3379 
3380  if (X) { // Build (X^Y) & Z
3381  Op1 = Builder.CreateXor(X, Y);
3382  Op1 = Builder.CreateAnd(Op1, Z);
3383  I.setOperand(0, Op1);
3384  I.setOperand(1, Constant::getNullValue(Op1->getType()));
3385  return &I;
3386  }
3387  }
3388 
3389  // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3390  // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3391  ConstantInt *Cst1;
3392  if ((Op0->hasOneUse() && match(Op0, m_ZExt(m_Value(A))) &&
3393  match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3394  (Op1->hasOneUse() && match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3395  match(Op1, m_ZExt(m_Value(A))))) {
3396  APInt Pow2 = Cst1->getValue() + 1;
3397  if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3398  Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3399  return new ICmpInst(Pred, A, Builder.CreateTrunc(B, A->getType()));
3400  }
3401 
3402  // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3403  // For lshr and ashr pairs.
3404  if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3405  match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3406  (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3407  match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3408  unsigned TypeBits = Cst1->getBitWidth();
3409  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3410  if (ShAmt < TypeBits && ShAmt != 0) {
3411  ICmpInst::Predicate NewPred =
3413  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3414  APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3415  return new ICmpInst(NewPred, Xor, Builder.getInt(CmpVal));
3416  }
3417  }
3418 
3419  // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0
3420  if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) &&
3421  match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) {
3422  unsigned TypeBits = Cst1->getBitWidth();
3423  unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3424  if (ShAmt < TypeBits && ShAmt != 0) {
3425  Value *Xor = Builder.CreateXor(A, B, I.getName() + ".unshifted");
3426  APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt);
3427  Value *And = Builder.CreateAnd(Xor, Builder.getInt(AndVal),
3428  I.getName() + ".mask");
3429  return new ICmpInst(Pred, And, Constant::getNullValue(Cst1->getType()));
3430  }
3431  }
3432 
3433  // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3434  // "icmp (and X, mask), cst"
3435  uint64_t ShAmt = 0;
3436  if (Op0->hasOneUse() &&
3437  match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), m_ConstantInt(ShAmt))))) &&
3438  match(Op1, m_ConstantInt(Cst1)) &&
3439  // Only do this when A has multiple uses. This is most important to do
3440  // when it exposes other optimizations.
3441  !A->hasOneUse()) {
3442  unsigned ASize = cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3443 
3444  if (ShAmt < ASize) {
3445  APInt MaskV =
3447  MaskV <<= ShAmt;
3448 
3449  APInt CmpV = Cst1->getValue().zext(ASize);
3450  CmpV <<= ShAmt;
3451 
3452  Value *Mask = Builder.CreateAnd(A, Builder.getInt(MaskV));
3453  return new ICmpInst(Pred, Mask, Builder.getInt(CmpV));
3454  }
3455  }
3456 
3457  // If both operands are byte-swapped or bit-reversed, just compare the
3458  // original values.
3459  // TODO: Move this to a function similar to foldICmpIntrinsicWithConstant()
3460  // and handle more intrinsics.
3461  if ((match(Op0, m_BSwap(m_Value(A))) && match(Op1, m_BSwap(m_Value(B)))) ||
3462  (match(Op0, m_BitReverse(m_Value(A))) &&
3463  match(Op1, m_BitReverse(m_Value(B)))))
3464  return new ICmpInst(Pred, A, B);
3465 
3466  return nullptr;
3467 }
3468 
3469 /// Handle icmp (cast x to y), (cast/cst). We only handle extending casts so
3470 /// far.
3471 Instruction *InstCombiner::foldICmpWithCastAndCast(ICmpInst &ICmp) {
3472  const CastInst *LHSCI = cast<CastInst>(ICmp.getOperand(0));
3473  Value *LHSCIOp = LHSCI->getOperand(0);
3474  Type *SrcTy = LHSCIOp->getType();
3475  Type *DestTy = LHSCI->getType();
3476  Value *RHSCIOp;
3477 
3478  // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
3479  // integer type is the same size as the pointer type.
3480  if (LHSCI->getOpcode() == Instruction::PtrToInt &&
3481  DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
3482  Value *RHSOp = nullptr;
3483  if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
3484  Value *RHSCIOp = RHSC->getOperand(0);
3485  if (RHSCIOp->getType()->getPointerAddressSpace() ==
3486  LHSCIOp->getType()->getPointerAddressSpace()) {
3487  RHSOp = RHSC->getOperand(0);
3488  // If the pointer types don't match, insert a bitcast.
3489  if (LHSCIOp->getType() != RHSOp->getType())
3490  RHSOp = Builder.CreateBitCast(RHSOp, LHSCIOp->getType());
3491  }
3492  } else if (auto *RHSC = dyn_cast<Constant>(ICmp.getOperand(1))) {
3493  RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
3494  }
3495 
3496  if (RHSOp)
3497  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSOp);
3498  }
3499 
3500  // The code below only handles extension cast instructions, so far.
3501  // Enforce this.
3502  if (LHSCI->getOpcode() != Instruction::ZExt &&
3503  LHSCI->getOpcode() != Instruction::SExt)
3504  return nullptr;
3505 
3506  bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
3507  bool isSignedCmp = ICmp.isSigned();
3508 
3509  if (auto *CI = dyn_cast<CastInst>(ICmp.getOperand(1))) {
3510  // Not an extension from the same type?
3511  RHSCIOp = CI->getOperand(0);
3512  if (RHSCIOp->getType() != LHSCIOp->getType())
3513  return nullptr;
3514 
3515  // If the signedness of the two casts doesn't agree (i.e. one is a sext
3516  // and the other is a zext), then we can't handle this.
3517  if (CI->getOpcode() != LHSCI->getOpcode())
3518  return nullptr;
3519 
3520  // Deal with equality cases early.
3521  if (ICmp.isEquality())
3522  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3523 
3524  // A signed comparison of sign extended values simplifies into a
3525  // signed comparison.
3526  if (isSignedCmp && isSignedExt)
3527  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, RHSCIOp);
3528 
3529  // The other three cases all fold into an unsigned comparison.
3530  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
3531  }
3532 
3533  // If we aren't dealing with a constant on the RHS, exit early.
3534  auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
3535  if (!C)
3536  return nullptr;
3537 
3538  // Compute the constant that would happen if we truncated to SrcTy then
3539  // re-extended to DestTy.
3540  Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
3541  Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), Res1, DestTy);
3542 
3543  // If the re-extended constant didn't change...
3544  if (Res2 == C) {
3545  // Deal with equality cases early.
3546  if (ICmp.isEquality())
3547  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3548 
3549  // A signed comparison of sign extended values simplifies into a
3550  // signed comparison.
3551  if (isSignedExt && isSignedCmp)
3552  return new ICmpInst(ICmp.getPredicate(), LHSCIOp, Res1);
3553 
3554  // The other three cases all fold into an unsigned comparison.
3555  return new ICmpInst(ICmp.getUnsignedPredicate(), LHSCIOp, Res1);
3556  }
3557 
3558  // The re-extended constant changed, partly changed (in the case of a vector),
3559  // or could not be determined to be equal (in the case of a constant
3560  // expression), so the constant cannot be represented in the shorter type.
3561  // Consequently, we cannot emit a simple comparison.
3562  // All the cases that fold to true or false will have already been handled
3563  // by SimplifyICmpInst, so only deal with the tricky case.
3564 
3565  if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
3566  return nullptr;
3567 
3568  // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
3569  // should have been folded away previously and not enter in here.
3570 
3571  // We're performing an unsigned comp with a sign extended value.
3572  // This is true if the input is >= 0. [aka >s -1]
3573  Constant *NegOne = Constant::getAllOnesValue(SrcTy);
3574  Value *Result = Builder.CreateICmpSGT(LHSCIOp, NegOne, ICmp.getName());
3575 
3576  // Finally, return the value computed.
3577  if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
3578  return replaceInstUsesWith(ICmp, Result);
3579 
3580  assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
3581  return BinaryOperator::CreateNot(Result);
3582 }
3583 
3584 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
3585  Value *RHS, Instruction &OrigI,
3586  Value *&Result, Constant *&Overflow) {
3587  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
3588  std::swap(LHS, RHS);
3589 
3590  auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
3591  Result = OpResult;
3592  Overflow = OverflowVal;
3593  if (ReuseName)
3594  Result->takeName(&OrigI);
3595  return true;
3596  };
3597 
3598  // If the overflow check was an add followed by a compare, the insertion point
3599  // may be pointing to the compare. We want to insert the new instructions
3600  // before the add in case there are uses of the add between the add and the
3601  // compare.
3602  Builder.SetInsertPoint(&OrigI);
3603 
3604  switch (OCF) {
3605  case OCF_INVALID:
3606  llvm_unreachable("bad overflow check kind!");
3607 
3608  case OCF_UNSIGNED_ADD: {
3609  OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI);
3611  return SetResult(Builder.CreateNUWAdd(LHS, RHS), Builder.getFalse(),
3612  true);
3613 
3615  return SetResult(Builder.CreateAdd(LHS, RHS), Builder.getTrue(), true);
3616 
3617  // Fall through uadd into sadd
3619  }
3620  case OCF_SIGNED_ADD: {
3621  // X + 0 -> {X, false}
3622  if (match(RHS, m_Zero()))
3623  return SetResult(LHS, Builder.getFalse(), false);
3624 
3625  // We can strength reduce this signed add into a regular add if we can prove
3626  // that it will never overflow.
3627  if (OCF == OCF_SIGNED_ADD)
3628  if (willNotOverflowSignedAdd(LHS, RHS, OrigI))
3629  return SetResult(Builder.CreateNSWAdd(LHS, RHS), Builder.getFalse(),
3630  true);
3631  break;
3632  }
3633 
3634  case OCF_UNSIGNED_SUB:
3635  case OCF_SIGNED_SUB: {
3636  // X - 0 -> {X, false}
3637  if (match(RHS, m_Zero()))
3638  return SetResult(LHS, Builder.getFalse(), false);
3639 
3640  if (OCF == OCF_SIGNED_SUB) {
3641  if (willNotOverflowSignedSub(LHS, RHS, OrigI))
3642  return SetResult(Builder.CreateNSWSub(LHS, RHS), Builder.getFalse(),
3643  true);
3644  } else {
3645  if (willNotOverflowUnsignedSub(LHS, RHS, OrigI))
3646  return SetResult(Builder.CreateNUWSub(LHS, RHS), Builder.getFalse(),
3647  true);
3648  }
3649  break;
3650  }
3651 
3652  case OCF_UNSIGNED_MUL: {
3653  OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI);
3655  return SetResult(Builder.CreateNUWMul(LHS, RHS), Builder.getFalse(),
3656  true);
3658  return SetResult(Builder.CreateMul(LHS, RHS), Builder.getTrue(), true);
3660  }
3661  case OCF_SIGNED_MUL:
3662  // X * undef -> undef
3663  if (isa<UndefValue>(RHS))
3664  return SetResult(RHS, UndefValue::get(Builder.getInt1Ty()), false);
3665 
3666  // X * 0 -> {0, false}
3667  if (match(RHS, m_Zero()))
3668  return SetResult(RHS, Builder.getFalse(), false);
3669 
3670  // X * 1 -> {X, false}
3671  if (match(RHS, m_One()))
3672  return SetResult(LHS, Builder.getFalse(), false);
3673 
3674  if (OCF == OCF_SIGNED_MUL)
3675  if (willNotOverflowSignedMul(LHS, RHS, OrigI))
3676  return SetResult(Builder.CreateNSWMul(LHS, RHS), Builder.getFalse(),
3677  true);
3678  break;
3679  }
3680 
3681  return false;
3682 }
3683 
3684 /// \brief Recognize and process idiom involving test for multiplication
3685 /// overflow.
3686 ///
3687 /// The caller has matched a pattern of the form:
3688 /// I = cmp u (mul(zext A, zext B), V
3689 /// The function checks if this is a test for overflow and if so replaces
3690 /// multiplication with call to 'mul.with.overflow' intrinsic.
3691 ///
3692 /// \param I Compare instruction.
3693 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
3694 /// the compare instruction. Must be of integer type.
3695 /// \param OtherVal The other argument of compare instruction.
3696 /// \returns Instruction which must replace the compare instruction, NULL if no
3697 /// replacement required.
3699  Value *OtherVal, InstCombiner &IC) {
3700  // Don't bother doing this transformation for pointers, don't do it for
3701  // vectors.
3702  if (!isa<IntegerType>(MulVal->getType()))
3703  return nullptr;
3704 
3705  assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
3706  assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
3707  auto *MulInstr = dyn_cast<Instruction>(MulVal);
3708  if (!MulInstr)
3709  return nullptr;
3710  assert(MulInstr->getOpcode() == Instruction::Mul);
3711 
3712  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
3713  *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
3714  assert(LHS->getOpcode() == Instruction::ZExt);
3715  assert(RHS->getOpcode() == Instruction::ZExt);
3716  Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
3717 
3718  // Calculate type and width of the result produced by mul.with.overflow.
3719  Type *TyA = A->getType(), *TyB = B->getType();
3720  unsigned WidthA = TyA->getPrimitiveSizeInBits(),
3721  WidthB = TyB->getPrimitiveSizeInBits();
3722  unsigned MulWidth;
3723  Type *MulType;
3724  if (WidthB > WidthA) {
3725  MulWidth = WidthB;
3726  MulType = TyB;
3727  } else {
3728  MulWidth = WidthA;
3729  MulType = TyA;
3730  }
3731 
3732  // In order to replace the original mul with a narrower mul.with.overflow,
3733  // all uses must ignore upper bits of the product. The number of used low
3734  // bits must be not greater than the width of mul.with.overflow.
3735  if (MulVal->hasNUsesOrMore(2))
3736  for (User *U : MulVal->users()) {
3737  if (U == &I)
3738  continue;
3739  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3740  // Check if truncation ignores bits above MulWidth.
3741  unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
3742  if (TruncWidth > MulWidth)
3743  return nullptr;
3744  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3745  // Check if AND ignores bits above MulWidth.
3746  if (BO->getOpcode() != Instruction::And)
3747  return nullptr;
3748  if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
3749  const APInt &CVal = CI->getValue();
3750  if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
3751  return nullptr;
3752  } else {
3753  // In this case we could have the operand of the binary operation
3754  // being defined in another block, and performing the replacement
3755  // could break the dominance relation.
3756  return nullptr;
3757  }
3758  } else {
3759  // Other uses prohibit this transformation.
3760  return nullptr;
3761  }
3762  }
3763 
3764  // Recognize patterns
3765  switch (I.getPredicate()) {
3766  case ICmpInst::ICMP_EQ:
3767  case ICmpInst::ICMP_NE:
3768  // Recognize pattern:
3769  // mulval = mul(zext A, zext B)
3770  // cmp eq/neq mulval, zext trunc mulval
3771  if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
3772  if (Zext->hasOneUse()) {
3773  Value *ZextArg = Zext->getOperand(0);
3774  if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
3775  if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
3776  break; //Recognized
3777  }
3778 
3779  // Recognize pattern:
3780  // mulval = mul(zext A, zext B)
3781  // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
3782  ConstantInt *CI;
3783  Value *ValToMask;
3784  if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
3785  if (ValToMask != MulVal)
3786  return nullptr;
3787  const APInt &CVal = CI->getValue() + 1;
3788  if (CVal.isPowerOf2()) {
3789  unsigned MaskWidth = CVal.logBase2();
3790  if (MaskWidth == MulWidth)
3791  break; // Recognized
3792  }
3793  }
3794  return nullptr;
3795 
3796  case ICmpInst::ICMP_UGT:
3797  // Recognize pattern:
3798  // mulval = mul(zext A, zext B)
3799  // cmp ugt mulval, max
3800  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3801  APInt MaxVal = APInt::getMaxValue(MulWidth);
3802  MaxVal = MaxVal.zext(CI->getBitWidth());
3803  if (MaxVal.eq(CI->getValue()))
3804  break; // Recognized
3805  }
3806  return nullptr;
3807 
3808  case ICmpInst::ICMP_UGE:
3809  // Recognize pattern:
3810  // mulval = mul(zext A, zext B)
3811  // cmp uge mulval, max+1
3812  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3813  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3814  if (MaxVal.eq(CI->getValue()))
3815  break; // Recognized
3816  }
3817  return nullptr;
3818 
3819  case ICmpInst::ICMP_ULE:
3820  // Recognize pattern:
3821  // mulval = mul(zext A, zext B)
3822  // cmp ule mulval, max
3823  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3824  APInt MaxVal = APInt::getMaxValue(MulWidth);
3825  MaxVal = MaxVal.zext(CI->getBitWidth());
3826  if (MaxVal.eq(CI->getValue()))
3827  break; // Recognized
3828  }
3829  return nullptr;
3830 
3831  case ICmpInst::ICMP_ULT:
3832  // Recognize pattern:
3833  // mulval = mul(zext A, zext B)
3834  // cmp ule mulval, max + 1
3835  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
3836  APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
3837  if (MaxVal.eq(CI->getValue()))
3838  break; // Recognized
3839  }
3840  return nullptr;
3841 
3842  default:
3843  return nullptr;
3844  }
3845 
3846  InstCombiner::BuilderTy &Builder = IC.Builder;
3847  Builder.SetInsertPoint(MulInstr);
3848 
3849  // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
3850  Value *MulA = A, *MulB = B;
3851  if (WidthA < MulWidth)
3852  MulA = Builder.CreateZExt(A, MulType);
3853  if (WidthB < MulWidth)
3854  MulB = Builder.CreateZExt(B, MulType);
3856  Intrinsic::umul_with_overflow, MulType);
3857  CallInst *Call = Builder.CreateCall(F, {MulA, MulB}, "umul");
3858  IC.Worklist.Add(MulInstr);
3859 
3860  // If there are uses of mul result other than the comparison, we know that
3861  // they are truncation or binary AND. Change them to use result of
3862  // mul.with.overflow and adjust properly mask/size.
3863  if (MulVal->hasNUsesOrMore(2)) {
3864  Value *Mul = Builder.CreateExtractValue(Call, 0, "umul.value");
3865  for (User *U : MulVal->users()) {
3866  if (U == &I || U == OtherVal)
3867  continue;
3868  if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
3869  if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
3870  IC.replaceInstUsesWith(*TI, Mul);
3871  else
3872  TI->setOperand(0, Mul);
3873  } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
3874  assert(BO->getOpcode() == Instruction::And);
3875  // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
3876  ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
3877  APInt ShortMask = CI->getValue().trunc(MulWidth);
3878  Value *ShortAnd = Builder.CreateAnd(Mul, ShortMask);
3879  Instruction *Zext =
3880  cast<Instruction>(Builder.CreateZExt(ShortAnd, BO->getType()));
3881  IC.Worklist.Add(Zext);
3882  IC.replaceInstUsesWith(*BO, Zext);
3883  } else {
3884  llvm_unreachable("Unexpected Binary operation");
3885  }
3886  IC.Worklist.Add(cast<Instruction>(U));
3887  }
3888  }
3889  if (isa<Instruction>(OtherVal))
3890  IC.Worklist.Add(cast<Instruction>(OtherVal));
3891 
3892  // The original icmp gets replaced with the overflow value, maybe inverted
3893  // depending on predicate.
3894  bool Inverse = false;
3895  switch (I.getPredicate()) {
3896  case ICmpInst::ICMP_NE:
3897  break;
3898  case ICmpInst::ICMP_EQ:
3899  Inverse = true;
3900  break;
3901  case ICmpInst::ICMP_UGT:
3902  case ICmpInst::ICMP_UGE:
3903  if (I.getOperand(0) == MulVal)
3904  break;
3905  Inverse = true;
3906  break;
3907  case ICmpInst::ICMP_ULT:
3908  case ICmpInst::ICMP_ULE:
3909  if (I.getOperand(1) == MulVal)
3910  break;
3911  Inverse = true;
3912  break;
3913  default:
3914  llvm_unreachable("Unexpected predicate");
3915  }
3916  if (Inverse) {
3917  Value *Res = Builder.CreateExtractValue(Call, 1);
3918  return BinaryOperator::CreateNot(Res);
3919  }
3920 
3921  return ExtractValueInst::Create(Call, 1);
3922 }
3923 
3924 /// When performing a comparison against a constant, it is possible that not all
3925 /// the bits in the LHS are demanded. This helper method computes the mask that
3926 /// IS demanded.
3927 static APInt getDemandedBitsLHSMask(ICmpInst &I, unsigned BitWidth,
3928  bool isSignCheck) {
3929  if (isSignCheck)
3930  return APInt::getSignMask(BitWidth);
3931 
3933  if (!CI) return APInt::getAllOnesValue(BitWidth);
3934  const APInt &RHS = CI->getValue();
3935 
3936  switch (I.getPredicate()) {
3937  // For a UGT comparison, we don't care about any bits that
3938  // correspond to the trailing ones of the comparand. The value of these
3939  // bits doesn't impact the outcome of the comparison, because any value
3940  // greater than the RHS must differ in a bit higher than these due to carry.
3941  case ICmpInst::ICMP_UGT: {
3942  unsigned trailingOnes = RHS.countTrailingOnes();
3943  return APInt::getBitsSetFrom(BitWidth, trailingOnes);
3944  }
3945 
3946  // Similarly, for a ULT comparison, we don't care about the trailing zeros.
3947  // Any value less than the RHS must differ in a higher bit because of carries.
3948  case ICmpInst::ICMP_ULT: {
3949  unsigned trailingZeros = RHS.countTrailingZeros();
3950  return APInt::getBitsSetFrom(BitWidth, trailingZeros);
3951  }
3952 
3953  default:
3954  return APInt::getAllOnesValue(BitWidth);
3955  }
3956 }
3957 
3958 /// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
3959 /// should be swapped.
3960 /// The decision is based on how many times these two operands are reused
3961 /// as subtract operands and their positions in those instructions.
3962 /// The rational is that several architectures use the same instruction for
3963 /// both subtract and cmp, thus it is better if the order of those operands
3964 /// match.
3965 /// \return true if Op0 and Op1 should be swapped.
3966 static bool swapMayExposeCSEOpportunities(const Value * Op0,
3967  const Value * Op1) {
3968  // Filter out pointer value as those cannot appears directly in subtract.
3969  // FIXME: we may want to go through inttoptrs or bitcasts.
3970  if (Op0->getType()->isPointerTy())
3971  return false;
3972  // Count every uses of both Op0 and Op1 in a subtract.
3973  // Each time Op0 is the first operand, count -1: swapping is bad, the
3974  // subtract has already the same layout as the compare.
3975  // Each time Op0 is the second operand, count +1: swapping is good, the
3976  // subtract has a different layout as the compare.
3977  // At the end, if the benefit is greater than 0, Op0 should come second to
3978  // expose more CSE opportunities.
3979  int GlobalSwapBenefits = 0;
3980  for (const User *U : Op0->users()) {
3981  const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U);
3982  if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
3983  continue;
3984  // If Op0 is the first argument, this is not beneficial to swap the
3985  // arguments.
3986  int LocalSwapBenefits = -1;
3987  unsigned Op1Idx = 1;
3988  if (BinOp->getOperand(Op1Idx) == Op0) {
3989  Op1Idx = 0;
3990  LocalSwapBenefits = 1;
3991  }
3992  if (BinOp->getOperand(Op1Idx) != Op1)
3993  continue;
3994  GlobalSwapBenefits += LocalSwapBenefits;
3995  }
3996  return GlobalSwapBenefits > 0;
3997 }
3998 
3999 /// \brief Check that one use is in the same block as the definition and all
4000 /// other uses are in blocks dominated by a given block.
4001 ///
4002 /// \param DI Definition
4003 /// \param UI Use
4004 /// \param DB Block that must dominate all uses of \p DI outside
4005 /// the parent block
4006 /// \return true when \p UI is the only use of \p DI in the parent block
4007 /// and all other uses of \p DI are in blocks dominated by \p DB.
4008 ///
4010  const Instruction *UI,
4011  const BasicBlock *DB) const {
4012  assert(DI && UI && "Instruction not defined\n");
4013  // Ignore incomplete definitions.
4014  if (!DI->getParent())
4015  return false;
4016  // DI and UI must be in the same block.
4017  if (DI->getParent() != UI->getParent())
4018  return false;
4019  // Protect from self-referencing blocks.
4020  if (DI->getParent() == DB)
4021  return false;
4022  for (const User *U : DI->users()) {
4023  auto *Usr = cast<Instruction>(U);
4024  if (Usr != UI && !DT.dominates(DB, Usr->getParent()))
4025  return false;
4026  }
4027  return true;
4028 }
4029 
4030 /// Return true when the instruction sequence within a block is select-cmp-br.
4031 static bool isChainSelectCmpBranch(const SelectInst *SI) {
4032  const BasicBlock *BB = SI->getParent();
4033  if (!BB)
4034  return false;
4035  auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator());
4036  if (!BI || BI->getNumSuccessors() != 2)
4037  return false;
4038  auto *IC = dyn_cast<ICmpInst>(BI->getCondition());
4039  if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI))
4040  return false;
4041  return true;
4042 }
4043 
4044 /// \brief True when a select result is replaced by one of its operands
4045 /// in select-icmp sequence. This will eventually result in the elimination
4046 /// of the select.
4047 ///
4048 /// \param SI Select instruction
4049 /// \param Icmp Compare instruction
4050 /// \param SIOpd Operand that replaces the select
4051 ///
4052 /// Notes:
4053 /// - The replacement is global and requires dominator information
4054 /// - The caller is responsible for the actual replacement
4055 ///
4056 /// Example:
4057 ///
4058 /// entry:
4059 /// %4 = select i1 %3, %C* %0, %C* null
4060 /// %5 = icmp eq %C* %4, null
4061 /// br i1 %5, label %9, label %7
4062 /// ...
4063 /// ; <label>:7 ; preds = %entry
4064 /// %8 = getelementptr inbounds %C* %4, i64 0, i32 0
4065 /// ...
4066 ///
4067 /// can be transformed to
4068 ///
4069 /// %5 = icmp eq %C* %0, null
4070 /// %6 = select i1 %3, i1 %5, i1 true
4071 /// br i1 %6, label %9, label %7
4072 /// ...
4073 /// ; <label>:7 ; preds = %entry
4074 /// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0!
4075 ///
4076 /// Similar when the first operand of the select is a constant or/and
4077 /// the compare is for not equal rather than equal.
4078 ///
4079 /// NOTE: The function is only called when the select and compare constants
4080 /// are equal, the optimization can work only for EQ predicates. This is not a
4081 /// major restriction since a NE compare should be 'normalized' to an equal
4082 /// compare, which usually happens in the combiner and test case
4083 /// select-cmp-br.ll checks for it.
4085  const ICmpInst *Icmp,
4086  const unsigned SIOpd) {
4087  assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!");
4088  if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) {
4089  BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1);
4090  // The check for the single predecessor is not the best that can be
4091  // done. But it protects efficiently against cases like when SI's
4092  // home block has two successors, Succ and Succ1, and Succ1 predecessor
4093  // of Succ. Then SI can't be replaced by SIOpd because the use that gets
4094  // replaced can be reached on either path. So the uniqueness check
4095  // guarantees that the path all uses of SI (outside SI's parent) are on
4096  // is disjoint from all other paths out of SI. But that information
4097  // is more expensive to compute, and the trade-off here is in favor
4098  // of compile-time. It should also be noticed that we check for a single
4099  // predecessor and not only uniqueness. This to handle the situation when
4100  // Succ and Succ1 points to the same basic block.
4101  if (Succ->getSinglePredecessor() && dominatesAllUses(SI, Icmp, Succ)) {
4102  NumSel++;
4103  SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent());
4104  return true;
4105  }
4106  }
4107  return false;
4108 }
4109 
4110 /// Try to fold the comparison based on range information we can get by checking
4111 /// whether bits are known to be zero or one in the inputs.
4112 Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
4113  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4114  Type *Ty = Op0->getType();
4115  ICmpInst::Predicate Pred = I.getPredicate();
4116 
4117  // Get scalar or pointer size.
4118  unsigned BitWidth = Ty->isIntOrIntVectorTy()
4119  ? Ty->getScalarSizeInBits()
4120  : DL.getTypeSizeInBits(Ty->getScalarType());
4121 
4122  if (!BitWidth)
4123  return nullptr;
4124 
4125  // If this is a normal comparison, it demands all bits. If it is a sign bit
4126  // comparison, it only demands the sign bit.
4127  bool IsSignBit = false;
4128  const APInt *CmpC;
4129  if (match(Op1, m_APInt(CmpC))) {
4130  bool UnusedBit;
4131  IsSignBit = isSignBitCheck(Pred, *CmpC, UnusedBit);
4132  }
4133 
4134  KnownBits Op0Known(BitWidth);
4135  KnownBits Op1Known(BitWidth);
4136 
4137  if (SimplifyDemandedBits(&I, 0,
4138  getDemandedBitsLHSMask(I, BitWidth, IsSignBit),
4139  Op0Known, 0))
4140  return &I;
4141 
4142  if (SimplifyDemandedBits(&I, 1, APInt::getAllOnesValue(BitWidth),
4143  Op1Known, 0))
4144  return &I;
4145 
4146  // Given the known and unknown bits, compute a range that the LHS could be
4147  // in. Compute the Min, Max and RHS values based on the known bits. For the
4148  // EQ and NE we use unsigned values.
4149  APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
4150  APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
4151  if (I.isSigned()) {
4152  computeSignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4153  computeSignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4154  } else {
4155  computeUnsignedMinMaxValuesFromKnownBits(Op0Known, Op0Min, Op0Max);
4156  computeUnsignedMinMaxValuesFromKnownBits(Op1Known, Op1Min, Op1Max);
4157  }
4158 
4159  // If Min and Max are known to be the same, then SimplifyDemandedBits
4160  // figured out that the LHS is a constant. Constant fold this now, so that
4161  // code below can assume that Min != Max.
4162  if (!isa<Constant>(Op0) && Op0Min == Op0Max)
4163  return new ICmpInst(Pred, ConstantInt::get(Op0->getType(), Op0Min), Op1);
4164  if (!isa<Constant>(Op1) && Op1Min == Op1Max)
4165  return new ICmpInst(Pred, Op0, ConstantInt::get(Op1->getType(), Op1Min));
4166 
4167  // Based on the range information we know about the LHS, see if we can
4168  // simplify this comparison. For example, (x&4) < 8 is always true.
4169  switch (Pred) {
4170  default:
4171  llvm_unreachable("Unknown icmp opcode!");
4172  case ICmpInst::ICMP_EQ:
4173  case ICmpInst::ICMP_NE: {
4174  if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) {
4175  return Pred == CmpInst::ICMP_EQ
4176  ? replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()))
4177  : replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4178  }
4179 
4180  // If all bits are known zero except for one, then we know at most one bit
4181  // is set. If the comparison is against zero, then this is a check to see if
4182  // *that* bit is set.
4183  APInt Op0KnownZeroInverted = ~Op0Known.Zero;
4184  if (Op1Known.isZero()) {
4185  // If the LHS is an AND with the same constant, look through it.
4186  Value *LHS = nullptr;
4187  const APInt *LHSC;
4188  if (!match(Op0, m_And(m_Value(LHS), m_APInt(LHSC))) ||
4189  *LHSC != Op0KnownZeroInverted)
4190  LHS = Op0;
4191 
4192  Value *X;
4193  if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
4194  APInt ValToCheck = Op0KnownZeroInverted;
4195  Type *XTy = X->getType();
4196  if (ValToCheck.isPowerOf2()) {
4197  // ((1 << X) & 8) == 0 -> X != 3
4198  // ((1 << X) & 8) != 0 -> X == 3
4199  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4200  auto NewPred = ICmpInst::getInversePredicate(Pred);
4201  return new ICmpInst(NewPred, X, CmpC);
4202  } else if ((++ValToCheck).isPowerOf2()) {
4203  // ((1 << X) & 7) == 0 -> X >= 3
4204  // ((1 << X) & 7) != 0 -> X < 3
4205  auto *CmpC = ConstantInt::get(XTy, ValToCheck.countTrailingZeros());
4206  auto NewPred =
4208  return new ICmpInst(NewPred, X, CmpC);
4209  }
4210  }
4211 
4212  // Check if the LHS is 8 >>u x and the result is a power of 2 like 1.
4213  const APInt *CI;
4214  if (Op0KnownZeroInverted.isOneValue() &&
4215  match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) {
4216  // ((8 >>u X) & 1) == 0 -> X != 3
4217  // ((8 >>u X) & 1) != 0 -> X == 3
4218  unsigned CmpVal = CI->countTrailingZeros();
4219  auto NewPred = ICmpInst::getInversePredicate(Pred);
4220  return new ICmpInst(NewPred, X, ConstantInt::get(X->getType(), CmpVal));
4221  }
4222  }
4223  break;
4224  }
4225  case ICmpInst::ICMP_ULT: {
4226  if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
4227  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4228  if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
4229  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4230  if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
4231  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4232 
4233  const APInt *CmpC;
4234  if (match(Op1, m_APInt(CmpC))) {
4235  // A <u C -> A == C-1 if min(A)+1 == C
4236  if (Op1Max == Op0Min + 1) {
4237  Constant *CMinus1 = ConstantInt::get(Op0->getType(), *CmpC - 1);
4238  return new ICmpInst(ICmpInst::ICMP_EQ, Op0, CMinus1);
4239  }
4240  }
4241  break;
4242  }
4243  case ICmpInst::ICMP_UGT: {
4244  if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
4245  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4246 
4247  if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
4248  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4249 
4250  if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
4251  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4252 
4253  const APInt *CmpC;
4254  if (match(Op1, m_APInt(CmpC))) {
4255  // A >u C -> A == C+1 if max(a)-1 == C
4256  if (*CmpC == Op0Max - 1)
4257  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4258  ConstantInt::get(Op1->getType(), *CmpC + 1));
4259  }
4260  break;
4261  }
4262  case ICmpInst::ICMP_SLT:
4263  if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
4264  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4265  if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
4266  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4267  if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
4268  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4269  if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
4270  if (Op1Max == Op0Min + 1) // A <s C -> A == C-1 if min(A)+1 == C
4271  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4272  Builder.getInt(CI->getValue() - 1));
4273  }
4274  break;
4275  case ICmpInst::ICMP_SGT:
4276  if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
4277  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4278  if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
4279  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4280 
4281  if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
4282  return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
4283  if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
4284  if (Op1Min == Op0Max - 1) // A >s C -> A == C+1 if max(A)-1 == C
4285  return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
4286  Builder.getInt(CI->getValue() + 1));
4287  }
4288  break;
4289  case ICmpInst::ICMP_SGE:
4290  assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
4291  if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
4292  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4293  if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
4294  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4295  break;
4296  case ICmpInst::ICMP_SLE:
4297  assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
4298  if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
4299  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4300  if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
4301  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4302  break;
4303  case ICmpInst::ICMP_UGE:
4304  assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
4305  if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
4306  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4307  if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
4308  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4309  break;
4310  case ICmpInst::ICMP_ULE:
4311  assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
4312  if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
4313  return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
4314  if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
4315  return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
4316  break;
4317  }
4318 
4319  // Turn a signed comparison into an unsigned one if both operands are known to
4320  // have the same sign.
4321  if (I.isSigned() &&
4322  ((Op0Known.Zero.isNegative() && Op1Known.Zero.isNegative()) ||
4323  (Op0Known.One.isNegative() && Op1Known.One.isNegative())))
4324  return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
4325 
4326  return nullptr;
4327 }
4328 
4329 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
4330 /// it into the appropriate icmp lt or icmp gt instruction. This transform
4331 /// allows them to be folded in visitICmpInst.
4333  ICmpInst::Predicate Pred = I.getPredicate();
4334  if (Pred != ICmpInst::ICMP_SLE && Pred != ICmpInst::ICMP_SGE &&
4335  Pred != ICmpInst::ICMP_ULE && Pred != ICmpInst::ICMP_UGE)
4336  return nullptr;
4337 
4338  Value *Op0 = I.getOperand(0);
4339  Value *Op1 = I.getOperand(1);
4340  auto *Op1C = dyn_cast<Constant>(Op1);
4341  if (!Op1C)
4342  return nullptr;
4343 
4344  // Check if the constant operand can be safely incremented/decremented without
4345  // overflowing/underflowing. For scalars, SimplifyICmpInst has already handled
4346  // the edge cases for us, so we just assert on them. For vectors, we must
4347  // handle the edge cases.
4348  Type *Op1Type = Op1->getType();
4349  bool IsSigned = I.isSigned();
4350  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
4351  auto *CI = dyn_cast<ConstantInt>(Op1C);
4352  if (CI) {
4353  // A <= MAX -> TRUE ; A >= MIN -> TRUE
4354  assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
4355  } else if (Op1Type->isVectorTy()) {
4356  // TODO? If the edge cases for vectors were guaranteed to be handled as they
4357  // are for scalar, we could remove the min/max checks. However, to do that,
4358  // we would have to use insertelement/shufflevector to replace edge values.
4359  unsigned NumElts = Op1Type->getVectorNumElements();
4360  for (unsigned i = 0; i != NumElts; ++i) {
4361  Constant *Elt = Op1C->getAggregateElement(i);
4362  if (!Elt)
4363  return nullptr;
4364 
4365  if (isa<UndefValue>(Elt))
4366  continue;
4367 
4368  // Bail out if we can't determine if this constant is min/max or if we
4369  // know that this constant is min/max.
4370  auto *CI = dyn_cast<ConstantInt>(Elt);
4371  if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
4372  return nullptr;
4373  }
4374  } else {
4375  // ConstantExpr?
4376  return nullptr;
4377  }
4378 
4379  // Increment or decrement the constant and set the new comparison predicate:
4380  // ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
4381  Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
4383  NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
4384  return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));
4385 }
4386 
4387 /// Integer compare with boolean values can always be turned into bitwise ops.
4389  InstCombiner::BuilderTy &Builder) {
4390  Value *A = I.getOperand(0), *B = I.getOperand(1);
4391  assert(A->getType()->isIntOrIntVectorTy(1) && "Bools only");
4392 
4393  // A boolean compared to true/false can be simplified to Op0/true/false in
4394  // 14 out of the 20 (10 predicates * 2 constants) possible combinations.
4395  // Cases not handled by InstSimplify are always 'not' of Op0.
4396  if (match(B, m_Zero())) {
4397  switch (I.getPredicate()) {
4398  case CmpInst::ICMP_EQ: // A == 0 -> !A
4399  case CmpInst::ICMP_ULE: // A <=u 0 -> !A
4400  case CmpInst::ICMP_SGE: // A >=s 0 -> !A
4401  return BinaryOperator::CreateNot(A);
4402  default:
4403  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4404  }
4405  } else if (match(B, m_One())) {
4406  switch (I.getPredicate()) {
4407  case CmpInst::ICMP_NE: // A != 1 -> !A
4408  case CmpInst::ICMP_ULT: // A <u 1 -> !A
4409  case CmpInst::ICMP_SGT: // A >s -1 -> !A
4410  return BinaryOperator::CreateNot(A);
4411  default:
4412  llvm_unreachable("ICmp i1 X, C not simplified as expected.");
4413  }
4414  }
4415 
4416  switch (I.getPredicate()) {
4417  default:
4418  llvm_unreachable("Invalid icmp instruction!");
4419  case ICmpInst::ICMP_EQ:
4420  // icmp eq i1 A, B -> ~(A ^ B)
4421  return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
4422 
4423  case ICmpInst::ICMP_NE:
4424  // icmp ne i1 A, B -> A ^ B
4425  return BinaryOperator::CreateXor(A, B);
4426 
4427  case ICmpInst::ICMP_UGT:
4428  // icmp ugt -> icmp ult
4429  std::swap(A, B);
4431  case ICmpInst::ICMP_ULT:
4432  // icmp ult i1 A, B -> ~A & B
4433  return BinaryOperator::CreateAnd(Builder.CreateNot(A), B);
4434 
4435  case ICmpInst::ICMP_SGT:
4436  // icmp sgt -> icmp slt
4437  std::swap(A, B);
4439  case ICmpInst::ICMP_SLT:
4440  // icmp slt i1 A, B -> A & ~B
4441  return BinaryOperator::CreateAnd(Builder.CreateNot(B), A);
4442 
4443  case ICmpInst::ICMP_UGE:
4444  // icmp uge -> icmp ule
4445  std::swap(A, B);
4447  case ICmpInst::ICMP_ULE:
4448  // icmp ule i1 A, B -> ~A | B
4449  return BinaryOperator::CreateOr(Builder.CreateNot(A), B);
4450 
4451  case ICmpInst::ICMP_SGE:
4452  // icmp sge -> icmp sle
4453  std::swap(A, B);
4455  case ICmpInst::ICMP_SLE:
4456  // icmp sle i1 A, B -> A | ~B
4457  return BinaryOperator::CreateOr(Builder.CreateNot(B), A);
4458  }
4459 }
4460 
4462  bool Changed = false;
4463  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4464  unsigned Op0Cplxity = getComplexity(Op0);
4465  unsigned Op1Cplxity = getComplexity(Op1);
4466 
4467  /// Orders the operands of the compare so that they are listed from most
4468  /// complex to least complex. This puts constants before unary operators,
4469  /// before binary operators.
4470  if (Op0Cplxity < Op1Cplxity ||
4471  (Op0Cplxity == Op1Cplxity && swapMayExposeCSEOpportunities(Op0, Op1))) {
4472  I.swapOperands();
4473  std::swap(Op0, Op1);
4474  Changed = true;
4475  }
4476 
4477  if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1,
4478  SQ.getWithInstruction(&I)))
4479  return replaceInstUsesWith(I, V);
4480 
4481  // comparing -val or val with non-zero is the same as just comparing val
4482  // ie, abs(val) != 0 -> val != 0
4483  if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) {
4484  Value *Cond, *SelectTrue, *SelectFalse;
4485  if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
4486  m_Value(SelectFalse)))) {
4487  if (Value *V = dyn_castNegVal(SelectTrue)) {
4488  if (V == SelectFalse)
4489  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4490  }
4491  else if (Value *V = dyn_castNegVal(SelectFalse)) {
4492  if (V == SelectTrue)
4493  return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
4494  }
4495  }
4496  }
4497 
4498  if (Op0->getType()->isIntOrIntVectorTy(1))
4499  if (Instruction *Res = canonicalizeICmpBool(I, Builder))
4500  return Res;
4501 
4502  if (ICmpInst *NewICmp = canonicalizeCmpWithConstant(I))
4503  return NewICmp;
4504 
4505  if (Instruction *Res = foldICmpWithConstant(I))
4506  return Res;
4507 
4508  if (Instruction *Res = foldICmpUsingKnownBits(I))
4509  return Res;
4510 
4511  // Test if the ICmpInst instruction is used exclusively by a select as
4512  // part of a minimum or maximum operation. If so, refrain from doing
4513  // any other folding. This helps out other analyses which understand
4514  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4515  // and CodeGen. And in this case, at least one of the comparison
4516  // operands has at least one user besides the compare (the select),
4517  // which would often largely negate the benefit of folding anyway.
4518  if (I.hasOneUse())
4519  if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
4520  if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
4521  (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
4522  return nullptr;
4523 
4524  // FIXME: We only do this after checking for min/max to prevent infinite
4525  // looping caused by a reverse canonicalization of these patterns for min/max.
4526  // FIXME: The organization of folds is a mess. These would naturally go into
4527  // canonicalizeCmpWithConstant(), but we can't move all of the above folds
4528  // down here after the min/max restriction.
4529  ICmpInst::Predicate Pred = I.getPredicate();
4530  const APInt *C;
4531  if (match(Op1, m_APInt(C))) {
4532  // For i32: x >u 2147483647 -> x <s 0 -> true if sign bit set
4533  if (Pred == ICmpInst::ICMP_UGT && C->isMaxSignedValue()) {
4535  return new ICmpInst(ICmpInst::ICMP_SLT, Op0, Zero);
4536  }
4537 
4538  // For i32: x <u 2147483648 -> x >s -1 -> true if sign bit clear
4539  if (Pred == ICmpInst::ICMP_ULT && C->isMinSignedValue()) {
4540  Constant *AllOnes = Constant::getAllOnesValue(Op0->getType());
4541  return new ICmpInst(ICmpInst::ICMP_SGT, Op0, AllOnes);
4542  }
4543  }
4544 
4545  if (Instruction *Res = foldICmpInstWithConstant(I))
4546  return Res;
4547 
4548  if (Instruction *Res = foldICmpInstWithConstantNotInt(I))
4549  return Res;
4550 
4551  // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
4552  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
4553  if (Instruction *NI = foldGEPICmp(GEP, Op1, I.getPredicate(), I))
4554  return NI;
4555  if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
4556  if (Instruction *NI = foldGEPICmp(GEP, Op0,
4558  return NI;
4559 
4560  // Try to optimize equality comparisons against alloca-based pointers.
4561  if (Op0->getType()->isPointerTy() && I.isEquality()) {
4562  assert(Op1->getType()->isPointerTy() && "Comparing pointer with non-pointer?");
4563  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op0, DL)))
4564  if (Instruction *New = foldAllocaCmp(I, Alloca, Op1))
4565  return New;
4566  if (auto *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Op1, DL)))
4567  if (Instruction *New = foldAllocaCmp(I, Alloca, Op0))
4568  return New;
4569  }
4570 
4571  // Test to see if the operands of the icmp are casted versions of other
4572  // values. If the ptr->ptr cast can be stripped off both arguments, we do so
4573  // now.
4574  if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
4575  if (Op0->getType()->isPointerTy() &&
4576  (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
4577  // We keep moving the cast from the left operand over to the right
4578  // operand, where it can often be eliminated completely.
4579  Op0 = CI->getOperand(0);
4580 
4581  // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
4582  // so eliminate it as well.
4583  if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
4584  Op1 = CI2->getOperand(0);
4585 
4586  // If Op1 is a constant, we can fold the cast into the constant.
4587  if (Op0->getType() != Op1->getType()) {
4588  if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
4589  Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
4590  } else {
4591  // Otherwise, cast the RHS right before the icmp
4592  Op1 = Builder.CreateBitCast(Op1, Op0->getType());
4593  }
4594  }
4595  return new ICmpInst(I.getPredicate(), Op0, Op1);
4596  }
4597  }
4598 
4599  if (isa<CastInst>(Op0)) {
4600  // Handle the special case of: icmp (cast bool to X), <cst>
4601  // This comes up when you have code like
4602  // int X = A < B;
4603  // if (X) ...
4604  // For generality, we handle any zero-extension of any operand comparison
4605  // with a constant or another cast from the same type.
4606  if (isa<Constant>(Op1) || isa<CastInst>(Op1))
4607  if (Instruction *R = foldICmpWithCastAndCast(I))
4608  return R;
4609  }
4610 
4611  if (Instruction *Res = foldICmpBinOp(I))
4612  return Res;
4613 
4614  if (Instruction *Res = foldICmpWithMinMax(I))
4615  return Res;
4616 
4617  {
4618  Value *A, *B;
4619  // Transform (A & ~B) == 0 --> (A & B) != 0
4620  // and (A & ~B) != 0 --> (A & B) == 0
4621  // if A is a power of 2.
4622  if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
4623  match(Op1, m_Zero()) &&
4624  isKnownToBeAPowerOfTwo(A, false, 0, &I) && I.isEquality())
4625  return new ICmpInst(I.getInversePredicate(), Builder.CreateAnd(A, B),
4626  Op1);
4627 
4628  // ~X < ~Y --> Y < X
4629  // ~X < C --> X > ~C
4630  if (match(Op0, m_Not(m_Value(A)))) {
4631  if (match(Op1, m_Not(m_Value(B))))
4632  return new ICmpInst(I.getPredicate(), B, A);
4633 
4634  const APInt *C;
4635  if (match(Op1, m_APInt(C)))
4636  return new ICmpInst(I.getSwappedPredicate(), A,
4637  ConstantInt::get(Op1->getType(), ~(*C)));
4638  }
4639 
4640  Instruction *AddI = nullptr;
4641  if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B),
4642  m_Instruction(AddI))) &&
4643  isa<IntegerType>(A->getType())) {
4644  Value *Result;
4645  Constant *Overflow;
4646  if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result,
4647  Overflow)) {
4648  replaceInstUsesWith(*AddI, Result);
4649  return replaceInstUsesWith(I, Overflow);
4650  }
4651  }
4652 
4653  // (zext a) * (zext b) --> llvm.umul.with.overflow.
4654  if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4655  if (Instruction *R = processUMulZExtIdiom(I, Op0, Op1, *this))
4656  return R;
4657  }
4658  if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
4659  if (Instruction *R = processUMulZExtIdiom(I, Op1, Op0, *this))
4660  return R;
4661  }
4662  }
4663 
4664  if (Instruction *Res = foldICmpEquality(I))
4665  return Res;
4666 
4667  // The 'cmpxchg' instruction returns an aggregate containing the old value and
4668  // an i1 which indicates whether or not we successfully did the swap.
4669  //
4670  // Replace comparisons between the old value and the expected value with the
4671  // indicator that 'cmpxchg' returns.
4672  //
4673  // N.B. This transform is only valid when the 'cmpxchg' is not permitted to
4674  // spuriously fail. In those cases, the old value may equal the expected
4675  // value but it is possible for the swap to not occur.
4676  if (I.getPredicate() == ICmpInst::ICMP_EQ)
4677  if (auto *EVI = dyn_cast<ExtractValueInst>(Op0))
4678  if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand()))
4679  if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 &&
4680  !ACXI->isWeak())
4681  return ExtractValueInst::Create(ACXI, 1);
4682 
4683  {
4684  Value *X; ConstantInt *Cst;
4685  // icmp X+Cst, X
4686  if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
4687  return foldICmpAddOpConst(I, X, Cst, I.getPredicate());
4688 
4689  // icmp X, X+Cst
4690  if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
4691  return foldICmpAddOpConst(I, X, Cst, I.getSwappedPredicate());
4692  }
4693  return Changed ? &I : nullptr;
4694 }
4695 
4696 /// Fold fcmp ([us]itofp x, cst) if possible.
4697 Instruction *InstCombiner::foldFCmpIntToFPConst(FCmpInst &I, Instruction *LHSI,
4698  Constant *RHSC) {
4699  if (!isa<ConstantFP>(RHSC)) return nullptr;
4700  const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
4701 
4702  // Get the width of the mantissa. We don't want to hack on conversions that
4703  // might lose information from the integer, e.g. "i64 -> float"
4704  int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
4705  if (MantissaWidth == -1) return nullptr; // Unknown.
4706 
4707  IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
4708 
4709  bool LHSUnsigned = isa<UIToFPInst>(LHSI);
4710 
4711  if (I.isEquality()) {
4713  bool IsExact = false;
4714  APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned);
4715  RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact);
4716 
4717  // If the floating point constant isn't an integer value, we know if we will
4718  // ever compare equal / not equal to it.
4719  if (!IsExact) {
4720  // TODO: Can never be -0.0 and other non-representable values
4721  APFloat RHSRoundInt(RHS);
4723  if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) {
4724  if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ)
4725  return replaceInstUsesWith(I, Builder.getFalse());
4726 
4728  return replaceInstUsesWith(I, Builder.getTrue());
4729  }
4730  }
4731 
4732  // TODO: If the constant is exactly representable, is it always OK to do
4733  // equality compares as integer?
4734  }
4735 
4736  // Check to see that the input is converted from an integer type that is small
4737  // enough that preserves all bits. TODO: check here for "known" sign bits.
4738  // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
4739  unsigned InputSize = IntTy->getScalarSizeInBits();
4740 
4741  // Following test does NOT adjust InputSize downwards for signed inputs,
4742  // because the most negative value still requires all the mantissa bits
4743  // to distinguish it from one less than that value.
4744  if ((int)InputSize > MantissaWidth) {
4745  // Conversion would lose accuracy. Check if loss can impact comparison.
4746  int Exp = ilogb(RHS);
4747  if (Exp == APFloat::IEK_Inf) {
4748  int MaxExponent = ilogb(APFloat::getLargest(RHS.getSemantics()));
4749  if (MaxExponent < (int)InputSize - !LHSUnsigned)
4750  // Conversion could create infinity.
4751  return nullptr;
4752  } else {
4753  // Note that if RHS is zero or NaN, then Exp is negative
4754  // and first condition is trivially false.
4755  if (MantissaWidth <= Exp && Exp <= (int)InputSize - !LHSUnsigned)
4756  // Conversion could affect comparison.
4757  return nullptr;
4758  }
4759  }
4760 
4761  // Otherwise, we can potentially simplify the comparison. We know that it
4762  // will always come through as an integer value and we know the constant is
4763  // not a NAN (it would have been previously simplified).
4764  assert(!RHS.isNaN() && "NaN comparison not already folded!");
4765 
4766  ICmpInst::Predicate Pred;
4767  switch (I.getPredicate()) {
4768  default: llvm_unreachable("Unexpected predicate!");
4769  case FCmpInst::FCMP_UEQ:
4770  case FCmpInst::FCMP_OEQ:
4771  Pred = ICmpInst::ICMP_EQ;
4772  break;
4773  case FCmpInst::FCMP_UGT:
4774  case FCmpInst::FCMP_OGT:
4775  Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
4776  break;
4777  case FCmpInst::FCMP_UGE:
4778  case FCmpInst::FCMP_OGE:
4779  Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
4780  break;
4781  case FCmpInst::FCMP_ULT:
4782  case FCmpInst::FCMP_OLT:
4783  Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
4784  break;
4785  case FCmpInst::FCMP_ULE:
4786  case FCmpInst::FCMP_OLE:
4787  Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
4788  break;
4789  case FCmpInst::FCMP_UNE:
4790  case FCmpInst::FCMP_ONE:
4791  Pred = ICmpInst::ICMP_NE;
4792  break;
4793  case FCmpInst::FCMP_ORD:
4794  return replaceInstUsesWith(I, Builder.getTrue());
4795  case FCmpInst::FCMP_UNO:
4796  return replaceInstUsesWith(I, Builder.getFalse());
4797  }
4798 
4799  // Now we know that the APFloat is a normal number, zero or inf.
4800 
4801  // See if the FP constant is too large for the integer. For example,
4802  // comparing an i8 to 300.0.
4803  unsigned IntWidth = IntTy->getScalarSizeInBits();
4804 
4805  if (!LHSUnsigned) {
4806  // If the RHS value is > SignedMax, fold the comparison. This handles +INF
4807  // and large values.
4808  APFloat SMax(RHS.getSemantics());
4809  SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
4811  if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
4812  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
4813  Pred == ICmpInst::ICMP_SLE)
4814  return replaceInstUsesWith(I, Builder.getTrue());
4815  return replaceInstUsesWith(I, Builder.getFalse());
4816  }
4817  } else {
4818  // If the RHS value is > UnsignedMax, fold the comparison. This handles
4819  // +INF and large values.
4820  APFloat UMax(RHS.getSemantics());
4821  UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
4823  if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
4824  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
4825  Pred == ICmpInst::ICMP_ULE)
4826  return replaceInstUsesWith(I, Builder.getTrue());
4827  return replaceInstUsesWith(I, Builder.getFalse());
4828  }
4829  }
4830 
4831  if (!LHSUnsigned) {
4832  // See if the RHS value is < SignedMin.
4833  APFloat SMin(RHS.getSemantics());
4834  SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
4836  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
4837  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
4838  Pred == ICmpInst::ICMP_SGE)
4839  return replaceInstUsesWith(I, Builder.getTrue());
4840  return replaceInstUsesWith(I, Builder.getFalse());
4841  }
4842  } else {
4843  // See if the RHS value is < UnsignedMin.
4844  APFloat SMin(RHS.getSemantics());
4845  SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
4847  if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
4848  if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
4849  Pred == ICmpInst::ICMP_UGE)
4850  return replaceInstUsesWith(I, Builder.getTrue());
4851  return replaceInstUsesWith(I, Builder.getFalse());
4852  }
4853  }
4854 
4855  // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
4856  // [0, UMAX], but it may still be fractional. See if it is fractional by
4857  // casting the FP value to the integer value and back, checking for equality.
4858  // Don't do this for zero, because -0.0 is not fractional.
4859  Constant *RHSInt = LHSUnsigned
4860  ? ConstantExpr::getFPToUI(RHSC, IntTy)
4861  : ConstantExpr::getFPToSI(RHSC, IntTy);
4862  if (!RHS.isZero()) {
4863  bool Equal = LHSUnsigned
4864  ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
4865  : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
4866  if (!Equal) {
4867  // If we had a comparison against a fractional value, we have to adjust
4868  // the compare predicate and sometimes the value. RHSC is rounded towards
4869  // zero at this point.
4870  switch (Pred) {
4871  default: llvm_unreachable("Unexpected integer comparison!");
4872  case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
4873  return replaceInstUsesWith(I, Builder.getTrue());
4874  case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
4875  return replaceInstUsesWith(I, Builder.getFalse());
4876  case ICmpInst::ICMP_ULE:
4877  // (float)int <= 4.4 --> int <= 4
4878  // (float)int <= -4.4 --> false
4879  if (RHS.isNegative())
4880  return replaceInstUsesWith(I, Builder.getFalse());
4881  break;
4882  case ICmpInst::ICMP_SLE:
4883  // (float)int <= 4.4 --> int <= 4
4884  // (float)int <= -4.4 --> int < -4
4885  if (RHS.isNegative())
4886  Pred = ICmpInst::ICMP_SLT;
4887  break;
4888  case ICmpInst::ICMP_ULT:
4889  // (float)int < -4.4 --> false
4890  // (float)int < 4.4 --> int <= 4
4891  if (RHS.isNegative())
4892  return replaceInstUsesWith(I, Builder.getFalse());
4893  Pred = ICmpInst::ICMP_ULE;
4894  break;
4895  case ICmpInst::ICMP_SLT:
4896  // (float)int < -4.4 --> int < -4
4897  // (float)int < 4.4 --> int <= 4
4898  if (!RHS.isNegative())
4899  Pred = ICmpInst::ICMP_SLE;
4900  break;
4901  case ICmpInst::ICMP_UGT:
4902  // (float)int > 4.4 --> int > 4
4903  // (float)int > -4.4 --> true
4904  if (RHS.isNegative())
4905  return replaceInstUsesWith(I, Builder.getTrue());
4906  break;
4907  case ICmpInst::ICMP_SGT:
4908  // (float)int > 4.4 --> int > 4
4909  // (float)int > -4.4 --> int >= -4
4910  if (RHS.isNegative())
4911  Pred = ICmpInst::ICMP_SGE;
4912  break;
4913  case ICmpInst::ICMP_UGE:
4914  // (float)int >= -4.4 --> true
4915  // (float)int >= 4.4 --> int > 4
4916  if (RHS.isNegative())
4917  return replaceInstUsesWith(I, Builder.getTrue());
4918  Pred = ICmpInst::ICMP_UGT;
4919  break;
4920  case ICmpInst::ICMP_SGE:
4921  // (float)int >= -4.4 --> int >= -4
4922  // (float)int >= 4.4 --> int > 4
4923  if (!RHS.isNegative())
4924  Pred = ICmpInst::ICMP_SGT;
4925  break;
4926  }
4927  }
4928  }
4929 
4930  // Lower this FP comparison into an appropriate integer version of the
4931  // comparison.
4932  return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
4933 }
4934 
4936  bool Changed = false;
4937 
4938  /// Orders the operands of the compare so that they are listed from most
4939  /// complex to least complex. This puts constants before unary operators,
4940  /// before binary operators.
4941  if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
4942  I.swapOperands();
4943  Changed = true;
4944  }
4945 
4946  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
4947 
4948  if (Value *V =
4949  SimplifyFCmpInst(I.getPredicate(), Op0, Op1, I.getFastMathFlags(),
4950  SQ.getWithInstruction(&I)))
4951  return replaceInstUsesWith(I, V);
4952 
4953  // Simplify 'fcmp pred X, X'
4954  if (Op0 == Op1) {
4955  switch (I.getPredicate()) {
4956  default: llvm_unreachable("Unknown predicate!");
4957  case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
4958  case FCmpInst::FCMP_ULT: // True if unordered or less than
4959  case FCmpInst::FCMP_UGT: // True if unordered or greater than
4960  case FCmpInst::FCMP_UNE: // True if unordered or not equal
4961  // Canonicalize these to be 'fcmp uno %X, 0.0'.
4964  return &I;
4965 
4966  case FCmpInst::FCMP_ORD: // True if ordered (no nans)
4967  case FCmpInst::FCMP_OEQ: // True if ordered and equal
4968  case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
4969  case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
4970  // Canonicalize these to be 'fcmp ord %X, 0.0'.
4973  return &I;
4974  }
4975  }
4976 
4977  // Test if the FCmpInst instruction is used exclusively by a select as
4978  // part of a minimum or maximum operation. If so, refrain from doing
4979  // any other folding. This helps out other analyses which understand
4980  // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
4981  // and CodeGen. And in this case, at least one of the comparison
4982  // operands has at least one user besides the compare (the select),
4983  // which would often largely negate the benefit of folding anyway.
4984  if (I.hasOneUse())
4985  if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
4986  if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
4987  (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
4988  return nullptr;
4989 
4990  // Handle fcmp with constant RHS
4991  if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
4992  if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
4993  switch (LHSI->getOpcode()) {
4994  case Instruction::FPExt: {
4995  // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
4996  FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
4997  ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
4998  if (!RHSF)
4999  break;
5000 
5001  const fltSemantics *Sem;
5002  // FIXME: This shouldn't be here.
5003  if (LHSExt->getSrcTy()->isHalfTy())
5004  Sem = &APFloat::IEEEhalf();
5005  else if (LHSExt->getSrcTy()->isFloatTy())
5006  Sem = &APFloat::IEEEsingle();
5007  else if (LHSExt->getSrcTy()->isDoubleTy())
5008  Sem = &APFloat::IEEEdouble();
5009  else if (LHSExt->getSrcTy()->isFP128Ty())
5010  Sem = &APFloat::IEEEquad();
5011  else if (LHSExt->getSrcTy()->isX86_FP80Ty())
5012  Sem = &APFloat::x87DoubleExtended();
5013  else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
5014  Sem = &APFloat::PPCDoubleDouble();
5015  else
5016  break;
5017 
5018  bool Lossy;
5019  APFloat F = RHSF->getValueAPF();
5020  F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
5021 
5022  // Avoid lossy conversions and denormals. Zero is a special case
5023  // that's OK to convert.
5024  APFloat Fabs = F;
5025  Fabs.clearSign();
5026  if (!Lossy &&
5027  ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
5028  APFloat::cmpLessThan) || Fabs.isZero()))
5029 
5030  return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
5031  ConstantFP::get(RHSC->getContext(), F));
5032  break;
5033  }
5034  case Instruction::PHI:
5035  // Only fold fcmp into the PHI if the phi and fcmp are in the same
5036  // block. If in the same block, we're encouraging jump threading. If
5037  // not, we are just pessimizing the code by making an i1 phi.
5038  if (LHSI->getParent() == I.getParent())
5039  if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
5040  return NV;
5041  break;
5042  case Instruction::SIToFP:
5043  case Instruction::UIToFP:
5044  if (Instruction *NV = foldFCmpIntToFPConst(I, LHSI, RHSC))
5045  return NV;
5046  break;
5047  case Instruction::FSub: {
5048  // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
5049  Value *Op;
5050  if (match(LHSI, m_FNeg(m_Value(Op))))
5051  return new FCmpInst(I.getSwappedPredicate(), Op,
5052  ConstantExpr::getFNeg(RHSC));
5053  break;
5054  }
5055  case Instruction::Load:
5056  if (GetElementPtrInst *GEP =
5057  dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
5058  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
5059  if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
5060  !cast<LoadInst>(LHSI)->isVolatile())
5061  if (Instruction *Res = foldCmpLoadFromIndexedGlobal(GEP, GV, I))
5062  return Res;
5063  }
5064