1 //===- InstCombineCompares.cpp --------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the visitICmp and visitFCmp functions.
12 //===----------------------------------------------------------------------===//
14 #include "InstCombine.h"
15 #include "llvm/Analysis/ConstantFolding.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
17 #include "llvm/Analysis/MemoryBuiltins.h"
18 #include "llvm/IR/ConstantRange.h"
19 #include "llvm/IR/DataLayout.h"
20 #include "llvm/IR/GetElementPtrTypeIterator.h"
21 #include "llvm/IR/IntrinsicInst.h"
22 #include "llvm/IR/PatternMatch.h"
23 #include "llvm/Target/TargetLibraryInfo.h"
25 using namespace PatternMatch;
27 #define DEBUG_TYPE "instcombine"
29 static ConstantInt *getOne(Constant *C) {
30 return ConstantInt::get(cast<IntegerType>(C->getType()), 1);
33 static ConstantInt *ExtractElement(Constant *V, Constant *Idx) {
34 return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx));
37 static bool HasAddOverflow(ConstantInt *Result,
38 ConstantInt *In1, ConstantInt *In2,
41 return Result->getValue().ult(In1->getValue());
43 if (In2->isNegative())
44 return Result->getValue().sgt(In1->getValue());
45 return Result->getValue().slt(In1->getValue());
48 /// AddWithOverflow - Compute Result = In1+In2, returning true if the result
49 /// overflowed for this type.
50 static bool AddWithOverflow(Constant *&Result, Constant *In1,
51 Constant *In2, bool IsSigned = false) {
52 Result = ConstantExpr::getAdd(In1, In2);
54 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
55 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
56 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
57 if (HasAddOverflow(ExtractElement(Result, Idx),
58 ExtractElement(In1, Idx),
59 ExtractElement(In2, Idx),
66 return HasAddOverflow(cast<ConstantInt>(Result),
67 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
71 static bool HasSubOverflow(ConstantInt *Result,
72 ConstantInt *In1, ConstantInt *In2,
75 return Result->getValue().ugt(In1->getValue());
77 if (In2->isNegative())
78 return Result->getValue().slt(In1->getValue());
80 return Result->getValue().sgt(In1->getValue());
83 /// SubWithOverflow - Compute Result = In1-In2, returning true if the result
84 /// overflowed for this type.
85 static bool SubWithOverflow(Constant *&Result, Constant *In1,
86 Constant *In2, bool IsSigned = false) {
87 Result = ConstantExpr::getSub(In1, In2);
89 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
90 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
91 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
92 if (HasSubOverflow(ExtractElement(Result, Idx),
93 ExtractElement(In1, Idx),
94 ExtractElement(In2, Idx),
101 return HasSubOverflow(cast<ConstantInt>(Result),
102 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
106 /// isSignBitCheck - Given an exploded icmp instruction, return true if the
107 /// comparison only checks the sign bit. If it only checks the sign bit, set
108 /// TrueIfSigned if the result of the comparison is true when the input value is
110 static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS,
111 bool &TrueIfSigned) {
113 case ICmpInst::ICMP_SLT: // True if LHS s< 0
115 return RHS->isZero();
116 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
118 return RHS->isAllOnesValue();
119 case ICmpInst::ICMP_SGT: // True if LHS s> -1
120 TrueIfSigned = false;
121 return RHS->isAllOnesValue();
122 case ICmpInst::ICMP_UGT:
123 // True if LHS u> RHS and RHS == high-bit-mask - 1
125 return RHS->isMaxValue(true);
126 case ICmpInst::ICMP_UGE:
127 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
129 return RHS->getValue().isSignBit();
135 /// Returns true if the exploded icmp can be expressed as a signed comparison
136 /// to zero and updates the predicate accordingly.
137 /// The signedness of the comparison is preserved.
138 static bool isSignTest(ICmpInst::Predicate &pred, const ConstantInt *RHS) {
139 if (!ICmpInst::isSigned(pred))
143 return ICmpInst::isRelational(pred);
146 if (pred == ICmpInst::ICMP_SLT) {
147 pred = ICmpInst::ICMP_SLE;
150 } else if (RHS->isAllOnesValue()) {
151 if (pred == ICmpInst::ICMP_SGT) {
152 pred = ICmpInst::ICMP_SGE;
160 // isHighOnes - Return true if the constant is of the form 1+0+.
161 // This is the same as lowones(~X).
162 static bool isHighOnes(const ConstantInt *CI) {
163 return (~CI->getValue() + 1).isPowerOf2();
166 /// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
167 /// set of known zero and one bits, compute the maximum and minimum values that
168 /// could have the specified known zero and known one bits, returning them in
170 static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero,
171 const APInt& KnownOne,
172 APInt& Min, APInt& Max) {
173 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
174 KnownZero.getBitWidth() == Min.getBitWidth() &&
175 KnownZero.getBitWidth() == Max.getBitWidth() &&
176 "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
177 APInt UnknownBits = ~(KnownZero|KnownOne);
179 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
180 // bit if it is unknown.
182 Max = KnownOne|UnknownBits;
184 if (UnknownBits.isNegative()) { // Sign bit is unknown
185 Min.setBit(Min.getBitWidth()-1);
186 Max.clearBit(Max.getBitWidth()-1);
190 // ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and
191 // a set of known zero and one bits, compute the maximum and minimum values that
192 // could have the specified known zero and known one bits, returning them in
194 static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero,
195 const APInt &KnownOne,
196 APInt &Min, APInt &Max) {
197 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
198 KnownZero.getBitWidth() == Min.getBitWidth() &&
199 KnownZero.getBitWidth() == Max.getBitWidth() &&
200 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
201 APInt UnknownBits = ~(KnownZero|KnownOne);
203 // The minimum value is when the unknown bits are all zeros.
205 // The maximum value is when the unknown bits are all ones.
206 Max = KnownOne|UnknownBits;
211 /// FoldCmpLoadFromIndexedGlobal - Called we see this pattern:
212 /// cmp pred (load (gep GV, ...)), cmpcst
213 /// where GV is a global variable with a constant initializer. Try to simplify
214 /// this into some simple computation that does not need the load. For example
215 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
217 /// If AndCst is non-null, then the loaded value is masked with that constant
218 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
219 Instruction *InstCombiner::
220 FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
221 CmpInst &ICI, ConstantInt *AndCst) {
222 // We need TD information to know the pointer size unless this is inbounds.
223 if (!GEP->isInBounds() && !DL)
226 Constant *Init = GV->getInitializer();
227 if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
230 uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
231 if (ArrayElementCount > 1024) return nullptr; // Don't blow up on huge arrays.
233 // There are many forms of this optimization we can handle, for now, just do
234 // the simple index into a single-dimensional array.
236 // Require: GEP GV, 0, i {{, constant indices}}
237 if (GEP->getNumOperands() < 3 ||
238 !isa<ConstantInt>(GEP->getOperand(1)) ||
239 !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
240 isa<Constant>(GEP->getOperand(2)))
243 // Check that indices after the variable are constants and in-range for the
244 // type they index. Collect the indices. This is typically for arrays of
246 SmallVector<unsigned, 4> LaterIndices;
248 Type *EltTy = Init->getType()->getArrayElementType();
249 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
250 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
251 if (!Idx) return nullptr; // Variable index.
253 uint64_t IdxVal = Idx->getZExtValue();
254 if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index.
256 if (StructType *STy = dyn_cast<StructType>(EltTy))
257 EltTy = STy->getElementType(IdxVal);
258 else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
259 if (IdxVal >= ATy->getNumElements()) return nullptr;
260 EltTy = ATy->getElementType();
262 return nullptr; // Unknown type.
265 LaterIndices.push_back(IdxVal);
268 enum { Overdefined = -3, Undefined = -2 };
270 // Variables for our state machines.
272 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
273 // "i == 47 | i == 87", where 47 is the first index the condition is true for,
274 // and 87 is the second (and last) index. FirstTrueElement is -2 when
275 // undefined, otherwise set to the first true element. SecondTrueElement is
276 // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
277 int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
279 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
280 // form "i != 47 & i != 87". Same state transitions as for true elements.
281 int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
283 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
284 /// define a state machine that triggers for ranges of values that the index
285 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
286 /// This is -2 when undefined, -3 when overdefined, and otherwise the last
287 /// index in the range (inclusive). We use -2 for undefined here because we
288 /// use relative comparisons and don't want 0-1 to match -1.
289 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
291 // MagicBitvector - This is a magic bitvector where we set a bit if the
292 // comparison is true for element 'i'. If there are 64 elements or less in
293 // the array, this will fully represent all the comparison results.
294 uint64_t MagicBitvector = 0;
297 // Scan the array and see if one of our patterns matches.
298 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
299 for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
300 Constant *Elt = Init->getAggregateElement(i);
301 if (!Elt) return nullptr;
303 // If this is indexing an array of structures, get the structure element.
304 if (!LaterIndices.empty())
305 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
307 // If the element is masked, handle it.
308 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
310 // Find out if the comparison would be true or false for the i'th element.
311 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt,
312 CompareRHS, DL, TLI);
313 // If the result is undef for this element, ignore it.
314 if (isa<UndefValue>(C)) {
315 // Extend range state machines to cover this element in case there is an
316 // undef in the middle of the range.
317 if (TrueRangeEnd == (int)i-1)
319 if (FalseRangeEnd == (int)i-1)
324 // If we can't compute the result for any of the elements, we have to give
325 // up evaluating the entire conditional.
326 if (!isa<ConstantInt>(C)) return nullptr;
328 // Otherwise, we know if the comparison is true or false for this element,
329 // update our state machines.
330 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
332 // State machine for single/double/range index comparison.
334 // Update the TrueElement state machine.
335 if (FirstTrueElement == Undefined)
336 FirstTrueElement = TrueRangeEnd = i; // First true element.
338 // Update double-compare state machine.
339 if (SecondTrueElement == Undefined)
340 SecondTrueElement = i;
342 SecondTrueElement = Overdefined;
344 // Update range state machine.
345 if (TrueRangeEnd == (int)i-1)
348 TrueRangeEnd = Overdefined;
351 // Update the FalseElement state machine.
352 if (FirstFalseElement == Undefined)
353 FirstFalseElement = FalseRangeEnd = i; // First false element.
355 // Update double-compare state machine.
356 if (SecondFalseElement == Undefined)
357 SecondFalseElement = i;
359 SecondFalseElement = Overdefined;
361 // Update range state machine.
362 if (FalseRangeEnd == (int)i-1)
365 FalseRangeEnd = Overdefined;
370 // If this element is in range, update our magic bitvector.
371 if (i < 64 && IsTrueForElt)
372 MagicBitvector |= 1ULL << i;
374 // If all of our states become overdefined, bail out early. Since the
375 // predicate is expensive, only check it every 8 elements. This is only
376 // really useful for really huge arrays.
377 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
378 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
379 FalseRangeEnd == Overdefined)
383 // Now that we've scanned the entire array, emit our new comparison(s). We
384 // order the state machines in complexity of the generated code.
385 Value *Idx = GEP->getOperand(2);
387 // If the index is larger than the pointer size of the target, truncate the
388 // index down like the GEP would do implicitly. We don't have to do this for
389 // an inbounds GEP because the index can't be out of range.
390 if (!GEP->isInBounds()) {
391 Type *IntPtrTy = DL->getIntPtrType(GEP->getType());
392 unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
393 if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize)
394 Idx = Builder->CreateTrunc(Idx, IntPtrTy);
397 // If the comparison is only true for one or two elements, emit direct
399 if (SecondTrueElement != Overdefined) {
400 // None true -> false.
401 if (FirstTrueElement == Undefined)
402 return ReplaceInstUsesWith(ICI, Builder->getFalse());
404 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
406 // True for one element -> 'i == 47'.
407 if (SecondTrueElement == Undefined)
408 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
410 // True for two elements -> 'i == 47 | i == 72'.
411 Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx);
412 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
413 Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx);
414 return BinaryOperator::CreateOr(C1, C2);
417 // If the comparison is only false for one or two elements, emit direct
419 if (SecondFalseElement != Overdefined) {
420 // None false -> true.
421 if (FirstFalseElement == Undefined)
422 return ReplaceInstUsesWith(ICI, Builder->getTrue());
424 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
426 // False for one element -> 'i != 47'.
427 if (SecondFalseElement == Undefined)
428 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
430 // False for two elements -> 'i != 47 & i != 72'.
431 Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx);
432 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
433 Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx);
434 return BinaryOperator::CreateAnd(C1, C2);
437 // If the comparison can be replaced with a range comparison for the elements
438 // where it is true, emit the range check.
439 if (TrueRangeEnd != Overdefined) {
440 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
442 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
443 if (FirstTrueElement) {
444 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
445 Idx = Builder->CreateAdd(Idx, Offs);
448 Value *End = ConstantInt::get(Idx->getType(),
449 TrueRangeEnd-FirstTrueElement+1);
450 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
453 // False range check.
454 if (FalseRangeEnd != Overdefined) {
455 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
456 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
457 if (FirstFalseElement) {
458 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
459 Idx = Builder->CreateAdd(Idx, Offs);
462 Value *End = ConstantInt::get(Idx->getType(),
463 FalseRangeEnd-FirstFalseElement);
464 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
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
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
478 if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth())
481 Ty = DL->getSmallestLegalIntType(Init->getContext(), ArrayElementCount);
482 else if (ArrayElementCount <= 32)
483 Ty = Type::getInt32Ty(Init->getContext());
486 Value *V = Builder->CreateIntCast(Idx, Ty, false);
487 V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
488 V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V);
489 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
497 /// EvaluateGEPOffsetExpression - Return a value that can be used to compare
498 /// the *offset* implied by a GEP to zero. For example, if we have &A[i], we
499 /// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can
500 /// be complex, and scales are involved. The above expression would also be
501 /// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32).
502 /// This later form is less amenable to optimization though, and we are allowed
503 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
505 /// If we can't emit an optimized form for this expression, this returns null.
507 static Value *EvaluateGEPOffsetExpression(User *GEP, InstCombiner &IC) {
508 const DataLayout &DL = *IC.getDataLayout();
509 gep_type_iterator GTI = gep_type_begin(GEP);
511 // Check to see if this gep only has a single variable index. If so, and if
512 // any constant indices are a multiple of its scale, then we can compute this
513 // in terms of the scale of the variable index. For example, if the GEP
514 // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
515 // because the expression will cross zero at the same point.
516 unsigned i, e = GEP->getNumOperands();
518 for (i = 1; i != e; ++i, ++GTI) {
519 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
520 // Compute the aggregate offset of constant indices.
521 if (CI->isZero()) continue;
523 // Handle a struct index, which adds its field offset to the pointer.
524 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
525 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
527 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
528 Offset += Size*CI->getSExtValue();
531 // Found our variable index.
536 // If there are no variable indices, we must have a constant offset, just
537 // evaluate it the general way.
538 if (i == e) return nullptr;
540 Value *VariableIdx = GEP->getOperand(i);
541 // Determine the scale factor of the variable element. For example, this is
542 // 4 if the variable index is into an array of i32.
543 uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType());
545 // Verify that there are no other variable indices. If so, emit the hard way.
546 for (++i, ++GTI; i != e; ++i, ++GTI) {
547 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
548 if (!CI) return nullptr;
550 // Compute the aggregate offset of constant indices.
551 if (CI->isZero()) continue;
553 // Handle a struct index, which adds its field offset to the pointer.
554 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
555 Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
557 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
558 Offset += Size*CI->getSExtValue();
564 // Okay, we know we have a single variable index, which must be a
565 // pointer/array/vector index. If there is no offset, life is simple, return
567 Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType());
568 unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth();
570 // Cast to intptrty in case a truncation occurs. If an extension is needed,
571 // we don't need to bother extending: the extension won't affect where the
572 // computation crosses zero.
573 if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
574 VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy);
579 // Otherwise, there is an index. The computation we will do will be modulo
580 // the pointer size, so get it.
581 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
583 Offset &= PtrSizeMask;
584 VariableScale &= PtrSizeMask;
586 // To do this transformation, any constant index must be a multiple of the
587 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
588 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
589 // multiple of the variable scale.
590 int64_t NewOffs = Offset / (int64_t)VariableScale;
591 if (Offset != NewOffs*(int64_t)VariableScale)
594 // Okay, we can do this evaluation. Start by converting the index to intptr.
595 if (VariableIdx->getType() != IntPtrTy)
596 VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy,
598 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
599 return IC.Builder->CreateAdd(VariableIdx, OffsetVal, "offset");
602 /// FoldGEPICmp - Fold comparisons between a GEP instruction and something
603 /// else. At this point we know that the GEP is on the LHS of the comparison.
604 Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
605 ICmpInst::Predicate Cond,
607 // Don't transform signed compares of GEPs into index compares. Even if the
608 // GEP is inbounds, the final add of the base pointer can have signed overflow
609 // and would change the result of the icmp.
610 // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
611 // the maximum signed value for the pointer type.
612 if (ICmpInst::isSigned(Cond))
615 // Look through bitcasts.
616 if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS))
617 RHS = BCI->getOperand(0);
619 Value *PtrBase = GEPLHS->getOperand(0);
620 if (DL && PtrBase == RHS && GEPLHS->isInBounds()) {
621 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
622 // This transformation (ignoring the base and scales) is valid because we
623 // know pointers can't overflow since the gep is inbounds. See if we can
624 // output an optimized form.
625 Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, *this);
627 // If not, synthesize the offset the hard way.
629 Offset = EmitGEPOffset(GEPLHS);
630 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
631 Constant::getNullValue(Offset->getType()));
632 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
633 // If the base pointers are different, but the indices are the same, just
634 // compare the base pointer.
635 if (PtrBase != GEPRHS->getOperand(0)) {
636 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
637 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
638 GEPRHS->getOperand(0)->getType();
640 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
641 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
642 IndicesTheSame = false;
646 // If all indices are the same, just compare the base pointers.
648 return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0));
650 // If we're comparing GEPs with two base pointers that only differ in type
651 // and both GEPs have only constant indices or just one use, then fold
652 // the compare with the adjusted indices.
653 if (DL && GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
654 (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
655 (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
656 PtrBase->stripPointerCasts() ==
657 GEPRHS->getOperand(0)->stripPointerCasts()) {
658 Value *Cmp = Builder->CreateICmp(ICmpInst::getSignedPredicate(Cond),
659 EmitGEPOffset(GEPLHS),
660 EmitGEPOffset(GEPRHS));
661 return ReplaceInstUsesWith(I, Cmp);
664 // Otherwise, the base pointers are different and the indices are
665 // different, bail out.
669 // If one of the GEPs has all zero indices, recurse.
670 bool AllZeros = true;
671 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
672 if (!isa<Constant>(GEPLHS->getOperand(i)) ||
673 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
678 return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
679 ICmpInst::getSwappedPredicate(Cond), I);
681 // If the other GEP has all zero indices, recurse.
683 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
684 if (!isa<Constant>(GEPRHS->getOperand(i)) ||
685 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
690 return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
692 bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
693 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
694 // If the GEPs only differ by one index, compare it.
695 unsigned NumDifferences = 0; // Keep track of # differences.
696 unsigned DiffOperand = 0; // The operand that differs.
697 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
698 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
699 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
700 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
701 // Irreconcilable differences.
705 if (NumDifferences++) break;
710 if (NumDifferences == 0) // SAME GEP?
711 return ReplaceInstUsesWith(I, // No comparison is needed here.
712 Builder->getInt1(ICmpInst::isTrueWhenEqual(Cond)));
714 else if (NumDifferences == 1 && GEPsInBounds) {
715 Value *LHSV = GEPLHS->getOperand(DiffOperand);
716 Value *RHSV = GEPRHS->getOperand(DiffOperand);
717 // Make sure we do a signed comparison here.
718 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
722 // Only lower this if the icmp is the only user of the GEP or if we expect
723 // the result to fold to a constant!
726 (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
727 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
728 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
729 Value *L = EmitGEPOffset(GEPLHS);
730 Value *R = EmitGEPOffset(GEPRHS);
731 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
737 /// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X".
738 Instruction *InstCombiner::FoldICmpAddOpCst(Instruction &ICI,
739 Value *X, ConstantInt *CI,
740 ICmpInst::Predicate Pred) {
741 // If we have X+0, exit early (simplifying logic below) and let it get folded
742 // elsewhere. icmp X+0, X -> icmp X, X
744 bool isTrue = ICmpInst::isTrueWhenEqual(Pred);
745 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue));
748 // (X+4) == X -> false.
749 if (Pred == ICmpInst::ICMP_EQ)
750 return ReplaceInstUsesWith(ICI, Builder->getFalse());
752 // (X+4) != X -> true.
753 if (Pred == ICmpInst::ICMP_NE)
754 return ReplaceInstUsesWith(ICI, Builder->getTrue());
756 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
757 // so the values can never be equal. Similarly for all other "or equals"
760 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
761 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
762 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
763 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
765 ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI);
766 return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
769 // (X+1) >u X --> X <u (0-1) --> X != 255
770 // (X+2) >u X --> X <u (0-2) --> X <u 254
771 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
772 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
773 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
775 unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
776 ConstantInt *SMax = ConstantInt::get(X->getContext(),
777 APInt::getSignedMaxValue(BitWidth));
779 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
780 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
781 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
782 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
783 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
784 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
785 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
786 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
788 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
789 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
790 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
791 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
792 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
793 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
795 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
796 Constant *C = Builder->getInt(CI->getValue()-1);
797 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
800 /// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS
801 /// and CmpRHS are both known to be integer constants.
802 Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
803 ConstantInt *DivRHS) {
804 ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1));
805 const APInt &CmpRHSV = CmpRHS->getValue();
807 // FIXME: If the operand types don't match the type of the divide
808 // then don't attempt this transform. The code below doesn't have the
809 // logic to deal with a signed divide and an unsigned compare (and
810 // vice versa). This is because (x /s C1) <s C2 produces different
811 // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
812 // (x /u C1) <u C2. Simply casting the operands and result won't
813 // work. :( The if statement below tests that condition and bails
815 bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv;
816 if (!ICI.isEquality() && DivIsSigned != ICI.isSigned())
818 if (DivRHS->isZero())
819 return nullptr; // The ProdOV computation fails on divide by zero.
820 if (DivIsSigned && DivRHS->isAllOnesValue())
821 return nullptr; // The overflow computation also screws up here
822 if (DivRHS->isOne()) {
823 // This eliminates some funny cases with INT_MIN.
824 ICI.setOperand(0, DivI->getOperand(0)); // X/1 == X.
828 // Compute Prod = CI * DivRHS. We are essentially solving an equation
829 // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
830 // C2 (CI). By solving for X we can turn this into a range check
831 // instead of computing a divide.
832 Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS);
834 // Determine if the product overflows by seeing if the product is
835 // not equal to the divide. Make sure we do the same kind of divide
836 // as in the LHS instruction that we're folding.
837 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
838 ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
840 // Get the ICmp opcode
841 ICmpInst::Predicate Pred = ICI.getPredicate();
843 /// If the division is known to be exact, then there is no remainder from the
844 /// divide, so the covered range size is unit, otherwise it is the divisor.
845 ConstantInt *RangeSize = DivI->isExact() ? getOne(Prod) : DivRHS;
847 // Figure out the interval that is being checked. For example, a comparison
848 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
849 // Compute this interval based on the constants involved and the signedness of
850 // the compare/divide. This computes a half-open interval, keeping track of
851 // whether either value in the interval overflows. After analysis each
852 // overflow variable is set to 0 if it's corresponding bound variable is valid
853 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
854 int LoOverflow = 0, HiOverflow = 0;
855 Constant *LoBound = nullptr, *HiBound = nullptr;
857 if (!DivIsSigned) { // udiv
858 // e.g. X/5 op 3 --> [15, 20)
860 HiOverflow = LoOverflow = ProdOV;
862 // If this is not an exact divide, then many values in the range collapse
863 // to the same result value.
864 HiOverflow = AddWithOverflow(HiBound, LoBound, RangeSize, false);
867 } else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0.
868 if (CmpRHSV == 0) { // (X / pos) op 0
869 // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
870 LoBound = ConstantExpr::getNeg(SubOne(RangeSize));
872 } else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos
873 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
874 HiOverflow = LoOverflow = ProdOV;
876 HiOverflow = AddWithOverflow(HiBound, Prod, RangeSize, true);
877 } else { // (X / pos) op neg
878 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
879 HiBound = AddOne(Prod);
880 LoOverflow = HiOverflow = ProdOV ? -1 : 0;
882 ConstantInt *DivNeg =cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
883 LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
886 } else if (DivRHS->isNegative()) { // Divisor is < 0.
888 RangeSize = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
889 if (CmpRHSV == 0) { // (X / neg) op 0
890 // e.g. X/-5 op 0 --> [-4, 5)
891 LoBound = AddOne(RangeSize);
892 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
893 if (HiBound == DivRHS) { // -INTMIN = INTMIN
894 HiOverflow = 1; // [INTMIN+1, overflow)
895 HiBound = nullptr; // e.g. X/INTMIN = 0 --> X > INTMIN
897 } else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos
898 // e.g. X/-5 op 3 --> [-19, -14)
899 HiBound = AddOne(Prod);
900 HiOverflow = LoOverflow = ProdOV ? -1 : 0;
902 LoOverflow = AddWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
903 } else { // (X / neg) op neg
904 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
905 LoOverflow = HiOverflow = ProdOV;
907 HiOverflow = SubWithOverflow(HiBound, Prod, RangeSize, true);
910 // Dividing by a negative swaps the condition. LT <-> GT
911 Pred = ICmpInst::getSwappedPredicate(Pred);
914 Value *X = DivI->getOperand(0);
916 default: llvm_unreachable("Unhandled icmp opcode!");
917 case ICmpInst::ICMP_EQ:
918 if (LoOverflow && HiOverflow)
919 return ReplaceInstUsesWith(ICI, Builder->getFalse());
921 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
922 ICmpInst::ICMP_UGE, X, LoBound);
924 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
925 ICmpInst::ICMP_ULT, X, HiBound);
926 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound,
928 case ICmpInst::ICMP_NE:
929 if (LoOverflow && HiOverflow)
930 return ReplaceInstUsesWith(ICI, Builder->getTrue());
932 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
933 ICmpInst::ICMP_ULT, X, LoBound);
935 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
936 ICmpInst::ICMP_UGE, X, HiBound);
937 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound,
938 DivIsSigned, false));
939 case ICmpInst::ICMP_ULT:
940 case ICmpInst::ICMP_SLT:
941 if (LoOverflow == +1) // Low bound is greater than input range.
942 return ReplaceInstUsesWith(ICI, Builder->getTrue());
943 if (LoOverflow == -1) // Low bound is less than input range.
944 return ReplaceInstUsesWith(ICI, Builder->getFalse());
945 return new ICmpInst(Pred, X, LoBound);
946 case ICmpInst::ICMP_UGT:
947 case ICmpInst::ICMP_SGT:
948 if (HiOverflow == +1) // High bound greater than input range.
949 return ReplaceInstUsesWith(ICI, Builder->getFalse());
950 if (HiOverflow == -1) // High bound less than input range.
951 return ReplaceInstUsesWith(ICI, Builder->getTrue());
952 if (Pred == ICmpInst::ICMP_UGT)
953 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
954 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
958 /// FoldICmpShrCst - Handle "icmp(([al]shr X, cst1), cst2)".
959 Instruction *InstCombiner::FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *Shr,
960 ConstantInt *ShAmt) {
961 const APInt &CmpRHSV = cast<ConstantInt>(ICI.getOperand(1))->getValue();
963 // Check that the shift amount is in range. If not, don't perform
964 // undefined shifts. When the shift is visited it will be
966 uint32_t TypeBits = CmpRHSV.getBitWidth();
967 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
968 if (ShAmtVal >= TypeBits || ShAmtVal == 0)
971 if (!ICI.isEquality()) {
972 // If we have an unsigned comparison and an ashr, we can't simplify this.
973 // Similarly for signed comparisons with lshr.
974 if (ICI.isSigned() != (Shr->getOpcode() == Instruction::AShr))
977 // Otherwise, all lshr and most exact ashr's are equivalent to a udiv/sdiv
978 // by a power of 2. Since we already have logic to simplify these,
979 // transform to div and then simplify the resultant comparison.
980 if (Shr->getOpcode() == Instruction::AShr &&
981 (!Shr->isExact() || ShAmtVal == TypeBits - 1))
984 // Revisit the shift (to delete it).
988 ConstantInt::get(Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal));
991 Shr->getOpcode() == Instruction::AShr ?
992 Builder->CreateSDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()) :
993 Builder->CreateUDiv(Shr->getOperand(0), DivCst, "", Shr->isExact());
995 ICI.setOperand(0, Tmp);
997 // If the builder folded the binop, just return it.
998 BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp);
1002 // Otherwise, fold this div/compare.
1003 assert(TheDiv->getOpcode() == Instruction::SDiv ||
1004 TheDiv->getOpcode() == Instruction::UDiv);
1006 Instruction *Res = FoldICmpDivCst(ICI, TheDiv, cast<ConstantInt>(DivCst));
1007 assert(Res && "This div/cst should have folded!");
1012 // If we are comparing against bits always shifted out, the
1013 // comparison cannot succeed.
1014 APInt Comp = CmpRHSV << ShAmtVal;
1015 ConstantInt *ShiftedCmpRHS = Builder->getInt(Comp);
1016 if (Shr->getOpcode() == Instruction::LShr)
1017 Comp = Comp.lshr(ShAmtVal);
1019 Comp = Comp.ashr(ShAmtVal);
1021 if (Comp != CmpRHSV) { // Comparing against a bit that we know is zero.
1022 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
1023 Constant *Cst = Builder->getInt1(IsICMP_NE);
1024 return ReplaceInstUsesWith(ICI, Cst);
1027 // Otherwise, check to see if the bits shifted out are known to be zero.
1028 // If so, we can compare against the unshifted value:
1029 // (X & 4) >> 1 == 2 --> (X & 4) == 4.
1030 if (Shr->hasOneUse() && Shr->isExact())
1031 return new ICmpInst(ICI.getPredicate(), Shr->getOperand(0), ShiftedCmpRHS);
1033 if (Shr->hasOneUse()) {
1034 // Otherwise strength reduce the shift into an and.
1035 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
1036 Constant *Mask = Builder->getInt(Val);
1038 Value *And = Builder->CreateAnd(Shr->getOperand(0),
1039 Mask, Shr->getName()+".mask");
1040 return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS);
1046 /// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
1048 Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
1051 const APInt &RHSV = RHS->getValue();
1053 switch (LHSI->getOpcode()) {
1054 case Instruction::Trunc:
1055 if (ICI.isEquality() && LHSI->hasOneUse()) {
1056 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1057 // of the high bits truncated out of x are known.
1058 unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
1059 SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits();
1060 APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
1061 computeKnownBits(LHSI->getOperand(0), KnownZero, KnownOne);
1063 // If all the high bits are known, we can do this xform.
1064 if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) {
1065 // Pull in the high bits from known-ones set.
1066 APInt NewRHS = RHS->getValue().zext(SrcBits);
1067 NewRHS |= KnownOne & APInt::getHighBitsSet(SrcBits, SrcBits-DstBits);
1068 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
1069 Builder->getInt(NewRHS));
1074 case Instruction::Xor: // (icmp pred (xor X, XorCst), CI)
1075 if (ConstantInt *XorCst = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
1076 // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1078 if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) ||
1079 (ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) {
1080 Value *CompareVal = LHSI->getOperand(0);
1082 // If the sign bit of the XorCst is not set, there is no change to
1083 // the operation, just stop using the Xor.
1084 if (!XorCst->isNegative()) {
1085 ICI.setOperand(0, CompareVal);
1090 // Was the old condition true if the operand is positive?
1091 bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT;
1093 // If so, the new one isn't.
1094 isTrueIfPositive ^= true;
1096 if (isTrueIfPositive)
1097 return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal,
1100 return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal,
1104 if (LHSI->hasOneUse()) {
1105 // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit))
1106 if (!ICI.isEquality() && XorCst->getValue().isSignBit()) {
1107 const APInt &SignBit = XorCst->getValue();
1108 ICmpInst::Predicate Pred = ICI.isSigned()
1109 ? ICI.getUnsignedPredicate()
1110 : ICI.getSignedPredicate();
1111 return new ICmpInst(Pred, LHSI->getOperand(0),
1112 Builder->getInt(RHSV ^ SignBit));
1115 // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A)
1116 if (!ICI.isEquality() && XorCst->isMaxValue(true)) {
1117 const APInt &NotSignBit = XorCst->getValue();
1118 ICmpInst::Predicate Pred = ICI.isSigned()
1119 ? ICI.getUnsignedPredicate()
1120 : ICI.getSignedPredicate();
1121 Pred = ICI.getSwappedPredicate(Pred);
1122 return new ICmpInst(Pred, LHSI->getOperand(0),
1123 Builder->getInt(RHSV ^ NotSignBit));
1127 // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C)
1128 // iff -C is a power of 2
1129 if (ICI.getPredicate() == ICmpInst::ICMP_UGT &&
1130 XorCst->getValue() == ~RHSV && (RHSV + 1).isPowerOf2())
1131 return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), XorCst);
1133 // (icmp ult (xor X, C), -C) -> (icmp uge X, C)
1134 // iff -C is a power of 2
1135 if (ICI.getPredicate() == ICmpInst::ICMP_ULT &&
1136 XorCst->getValue() == -RHSV && RHSV.isPowerOf2())
1137 return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), XorCst);
1140 case Instruction::And: // (icmp pred (and X, AndCst), RHS)
1141 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
1142 LHSI->getOperand(0)->hasOneUse()) {
1143 ConstantInt *AndCst = cast<ConstantInt>(LHSI->getOperand(1));
1145 // If the LHS is an AND of a truncating cast, we can widen the
1146 // and/compare to be the input width without changing the value
1147 // produced, eliminating a cast.
1148 if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) {
1149 // We can do this transformation if either the AND constant does not
1150 // have its sign bit set or if it is an equality comparison.
1151 // Extending a relational comparison when we're checking the sign
1152 // bit would not work.
1153 if (ICI.isEquality() ||
1154 (!AndCst->isNegative() && RHSV.isNonNegative())) {
1156 Builder->CreateAnd(Cast->getOperand(0),
1157 ConstantExpr::getZExt(AndCst, Cast->getSrcTy()));
1158 NewAnd->takeName(LHSI);
1159 return new ICmpInst(ICI.getPredicate(), NewAnd,
1160 ConstantExpr::getZExt(RHS, Cast->getSrcTy()));
1164 // If the LHS is an AND of a zext, and we have an equality compare, we can
1165 // shrink the and/compare to the smaller type, eliminating the cast.
1166 if (ZExtInst *Cast = dyn_cast<ZExtInst>(LHSI->getOperand(0))) {
1167 IntegerType *Ty = cast<IntegerType>(Cast->getSrcTy());
1168 // Make sure we don't compare the upper bits, SimplifyDemandedBits
1169 // should fold the icmp to true/false in that case.
1170 if (ICI.isEquality() && RHSV.getActiveBits() <= Ty->getBitWidth()) {
1172 Builder->CreateAnd(Cast->getOperand(0),
1173 ConstantExpr::getTrunc(AndCst, Ty));
1174 NewAnd->takeName(LHSI);
1175 return new ICmpInst(ICI.getPredicate(), NewAnd,
1176 ConstantExpr::getTrunc(RHS, Ty));
1180 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
1181 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
1182 // happens a LOT in code produced by the C front-end, for bitfield
1184 BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0));
1185 if (Shift && !Shift->isShift())
1189 ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : nullptr;
1191 // This seemingly simple opportunity to fold away a shift turns out to
1192 // be rather complicated. See PR17827
1193 // ( http://llvm.org/bugs/show_bug.cgi?id=17827 ) for details.
1195 bool CanFold = false;
1196 unsigned ShiftOpcode = Shift->getOpcode();
1197 if (ShiftOpcode == Instruction::AShr) {
1198 // There may be some constraints that make this possible,
1199 // but nothing simple has been discovered yet.
1201 } else if (ShiftOpcode == Instruction::Shl) {
1202 // For a left shift, we can fold if the comparison is not signed.
1203 // We can also fold a signed comparison if the mask value and
1204 // comparison value are not negative. These constraints may not be
1205 // obvious, but we can prove that they are correct using an SMT
1207 if (!ICI.isSigned() || (!AndCst->isNegative() && !RHS->isNegative()))
1209 } else if (ShiftOpcode == Instruction::LShr) {
1210 // For a logical right shift, we can fold if the comparison is not
1211 // signed. We can also fold a signed comparison if the shifted mask
1212 // value and the shifted comparison value are not negative.
1213 // These constraints may not be obvious, but we can prove that they
1214 // are correct using an SMT solver.
1215 if (!ICI.isSigned())
1218 ConstantInt *ShiftedAndCst =
1219 cast<ConstantInt>(ConstantExpr::getShl(AndCst, ShAmt));
1220 ConstantInt *ShiftedRHSCst =
1221 cast<ConstantInt>(ConstantExpr::getShl(RHS, ShAmt));
1223 if (!ShiftedAndCst->isNegative() && !ShiftedRHSCst->isNegative())
1230 if (ShiftOpcode == Instruction::Shl)
1231 NewCst = ConstantExpr::getLShr(RHS, ShAmt);
1233 NewCst = ConstantExpr::getShl(RHS, ShAmt);
1235 // Check to see if we are shifting out any of the bits being
1237 if (ConstantExpr::get(ShiftOpcode, NewCst, ShAmt) != RHS) {
1238 // If we shifted bits out, the fold is not going to work out.
1239 // As a special case, check to see if this means that the
1240 // result is always true or false now.
1241 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
1242 return ReplaceInstUsesWith(ICI, Builder->getFalse());
1243 if (ICI.getPredicate() == ICmpInst::ICMP_NE)
1244 return ReplaceInstUsesWith(ICI, Builder->getTrue());
1246 ICI.setOperand(1, NewCst);
1247 Constant *NewAndCst;
1248 if (ShiftOpcode == Instruction::Shl)
1249 NewAndCst = ConstantExpr::getLShr(AndCst, ShAmt);
1251 NewAndCst = ConstantExpr::getShl(AndCst, ShAmt);
1252 LHSI->setOperand(1, NewAndCst);
1253 LHSI->setOperand(0, Shift->getOperand(0));
1254 Worklist.Add(Shift); // Shift is dead.
1260 // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is
1261 // preferable because it allows the C<<Y expression to be hoisted out
1262 // of a loop if Y is invariant and X is not.
1263 if (Shift && Shift->hasOneUse() && RHSV == 0 &&
1264 ICI.isEquality() && !Shift->isArithmeticShift() &&
1265 !isa<Constant>(Shift->getOperand(0))) {
1268 if (Shift->getOpcode() == Instruction::LShr) {
1269 NS = Builder->CreateShl(AndCst, Shift->getOperand(1));
1271 // Insert a logical shift.
1272 NS = Builder->CreateLShr(AndCst, Shift->getOperand(1));
1275 // Compute X & (C << Y).
1277 Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName());
1279 ICI.setOperand(0, NewAnd);
1283 // Replace ((X & AndCst) > RHSV) with ((X & AndCst) != 0), if any
1284 // bit set in (X & AndCst) will produce a result greater than RHSV.
1285 if (ICI.getPredicate() == ICmpInst::ICMP_UGT) {
1286 unsigned NTZ = AndCst->getValue().countTrailingZeros();
1287 if ((NTZ < AndCst->getBitWidth()) &&
1288 APInt::getOneBitSet(AndCst->getBitWidth(), NTZ).ugt(RHSV))
1289 return new ICmpInst(ICmpInst::ICMP_NE, LHSI,
1290 Constant::getNullValue(RHS->getType()));
1294 // Try to optimize things like "A[i]&42 == 0" to index computations.
1295 if (LoadInst *LI = dyn_cast<LoadInst>(LHSI->getOperand(0))) {
1296 if (GetElementPtrInst *GEP =
1297 dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1298 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1299 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1300 !LI->isVolatile() && isa<ConstantInt>(LHSI->getOperand(1))) {
1301 ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1));
1302 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C))
1307 // X & -C == -C -> X > u ~C
1308 // X & -C != -C -> X <= u ~C
1309 // iff C is a power of 2
1310 if (ICI.isEquality() && RHS == LHSI->getOperand(1) && (-RHSV).isPowerOf2())
1311 return new ICmpInst(
1312 ICI.getPredicate() == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_UGT
1313 : ICmpInst::ICMP_ULE,
1314 LHSI->getOperand(0), SubOne(RHS));
1317 case Instruction::Or: {
1318 if (!ICI.isEquality() || !RHS->isNullValue() || !LHSI->hasOneUse())
1321 if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1322 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1323 // -> and (icmp eq P, null), (icmp eq Q, null).
1324 Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P,
1325 Constant::getNullValue(P->getType()));
1326 Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q,
1327 Constant::getNullValue(Q->getType()));
1329 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
1330 Op = BinaryOperator::CreateAnd(ICIP, ICIQ);
1332 Op = BinaryOperator::CreateOr(ICIP, ICIQ);
1338 case Instruction::Mul: { // (icmp pred (mul X, Val), CI)
1339 ConstantInt *Val = dyn_cast<ConstantInt>(LHSI->getOperand(1));
1342 // If this is a signed comparison to 0 and the mul is sign preserving,
1343 // use the mul LHS operand instead.
1344 ICmpInst::Predicate pred = ICI.getPredicate();
1345 if (isSignTest(pred, RHS) && !Val->isZero() &&
1346 cast<BinaryOperator>(LHSI)->hasNoSignedWrap())
1347 return new ICmpInst(Val->isNegative() ?
1348 ICmpInst::getSwappedPredicate(pred) : pred,
1349 LHSI->getOperand(0),
1350 Constant::getNullValue(RHS->getType()));
1355 case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI)
1356 uint32_t TypeBits = RHSV.getBitWidth();
1357 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
1360 // (1 << X) pred P2 -> X pred Log2(P2)
1361 if (match(LHSI, m_Shl(m_One(), m_Value(X)))) {
1362 bool RHSVIsPowerOf2 = RHSV.isPowerOf2();
1363 ICmpInst::Predicate Pred = ICI.getPredicate();
1364 if (ICI.isUnsigned()) {
1365 if (!RHSVIsPowerOf2) {
1366 // (1 << X) < 30 -> X <= 4
1367 // (1 << X) <= 30 -> X <= 4
1368 // (1 << X) >= 30 -> X > 4
1369 // (1 << X) > 30 -> X > 4
1370 if (Pred == ICmpInst::ICMP_ULT)
1371 Pred = ICmpInst::ICMP_ULE;
1372 else if (Pred == ICmpInst::ICMP_UGE)
1373 Pred = ICmpInst::ICMP_UGT;
1375 unsigned RHSLog2 = RHSV.logBase2();
1377 // (1 << X) >= 2147483648 -> X >= 31 -> X == 31
1378 // (1 << X) > 2147483648 -> X > 31 -> false
1379 // (1 << X) <= 2147483648 -> X <= 31 -> true
1380 // (1 << X) < 2147483648 -> X < 31 -> X != 31
1381 if (RHSLog2 == TypeBits-1) {
1382 if (Pred == ICmpInst::ICMP_UGE)
1383 Pred = ICmpInst::ICMP_EQ;
1384 else if (Pred == ICmpInst::ICMP_UGT)
1385 return ReplaceInstUsesWith(ICI, Builder->getFalse());
1386 else if (Pred == ICmpInst::ICMP_ULE)
1387 return ReplaceInstUsesWith(ICI, Builder->getTrue());
1388 else if (Pred == ICmpInst::ICMP_ULT)
1389 Pred = ICmpInst::ICMP_NE;
1392 return new ICmpInst(Pred, X,
1393 ConstantInt::get(RHS->getType(), RHSLog2));
1394 } else if (ICI.isSigned()) {
1395 if (RHSV.isAllOnesValue()) {
1396 // (1 << X) <= -1 -> X == 31
1397 if (Pred == ICmpInst::ICMP_SLE)
1398 return new ICmpInst(ICmpInst::ICMP_EQ, X,
1399 ConstantInt::get(RHS->getType(), TypeBits-1));
1401 // (1 << X) > -1 -> X != 31
1402 if (Pred == ICmpInst::ICMP_SGT)
1403 return new ICmpInst(ICmpInst::ICMP_NE, X,
1404 ConstantInt::get(RHS->getType(), TypeBits-1));
1406 // (1 << X) < 0 -> X == 31
1407 // (1 << X) <= 0 -> X == 31
1408 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
1409 return new ICmpInst(ICmpInst::ICMP_EQ, X,
1410 ConstantInt::get(RHS->getType(), TypeBits-1));
1412 // (1 << X) >= 0 -> X != 31
1413 // (1 << X) > 0 -> X != 31
1414 if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
1415 return new ICmpInst(ICmpInst::ICMP_NE, X,
1416 ConstantInt::get(RHS->getType(), TypeBits-1));
1418 } else if (ICI.isEquality()) {
1420 return new ICmpInst(
1421 Pred, X, ConstantInt::get(RHS->getType(), RHSV.logBase2()));
1423 return ReplaceInstUsesWith(
1424 ICI, Pred == ICmpInst::ICMP_EQ ? Builder->getFalse()
1425 : Builder->getTrue());
1431 // Check that the shift amount is in range. If not, don't perform
1432 // undefined shifts. When the shift is visited it will be
1434 if (ShAmt->uge(TypeBits))
1437 if (ICI.isEquality()) {
1438 // If we are comparing against bits always shifted out, the
1439 // comparison cannot succeed.
1441 ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt),
1443 if (Comp != RHS) {// Comparing against a bit that we know is zero.
1444 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
1445 Constant *Cst = Builder->getInt1(IsICMP_NE);
1446 return ReplaceInstUsesWith(ICI, Cst);
1449 // If the shift is NUW, then it is just shifting out zeros, no need for an
1451 if (cast<BinaryOperator>(LHSI)->hasNoUnsignedWrap())
1452 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
1453 ConstantExpr::getLShr(RHS, ShAmt));
1455 // If the shift is NSW and we compare to 0, then it is just shifting out
1456 // sign bits, no need for an AND either.
1457 if (cast<BinaryOperator>(LHSI)->hasNoSignedWrap() && RHSV == 0)
1458 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
1459 ConstantExpr::getLShr(RHS, ShAmt));
1461 if (LHSI->hasOneUse()) {
1462 // Otherwise strength reduce the shift into an and.
1463 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
1464 Constant *Mask = Builder->getInt(APInt::getLowBitsSet(TypeBits,
1465 TypeBits - ShAmtVal));
1468 Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask");
1469 return new ICmpInst(ICI.getPredicate(), And,
1470 ConstantExpr::getLShr(RHS, ShAmt));
1474 // If this is a signed comparison to 0 and the shift is sign preserving,
1475 // use the shift LHS operand instead.
1476 ICmpInst::Predicate pred = ICI.getPredicate();
1477 if (isSignTest(pred, RHS) &&
1478 cast<BinaryOperator>(LHSI)->hasNoSignedWrap())
1479 return new ICmpInst(pred,
1480 LHSI->getOperand(0),
1481 Constant::getNullValue(RHS->getType()));
1483 // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
1484 bool TrueIfSigned = false;
1485 if (LHSI->hasOneUse() &&
1486 isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) {
1487 // (X << 31) <s 0 --> (X&1) != 0
1488 Constant *Mask = ConstantInt::get(LHSI->getOperand(0)->getType(),
1489 APInt::getOneBitSet(TypeBits,
1490 TypeBits-ShAmt->getZExtValue()-1));
1492 Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask");
1493 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
1494 And, Constant::getNullValue(And->getType()));
1497 // Transform (icmp pred iM (shl iM %v, N), CI)
1498 // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (CI>>N))
1499 // Transform the shl to a trunc if (trunc (CI>>N)) has no loss and M-N.
1500 // This enables to get rid of the shift in favor of a trunc which can be
1501 // free on the target. It has the additional benefit of comparing to a
1502 // smaller constant, which will be target friendly.
1503 unsigned Amt = ShAmt->getLimitedValue(TypeBits-1);
1504 if (LHSI->hasOneUse() &&
1505 Amt != 0 && RHSV.countTrailingZeros() >= Amt) {
1506 Type *NTy = IntegerType::get(ICI.getContext(), TypeBits - Amt);
1507 Constant *NCI = ConstantExpr::getTrunc(
1508 ConstantExpr::getAShr(RHS,
1509 ConstantInt::get(RHS->getType(), Amt)),
1511 return new ICmpInst(ICI.getPredicate(),
1512 Builder->CreateTrunc(LHSI->getOperand(0), NTy),
1519 case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
1520 case Instruction::AShr: {
1521 // Handle equality comparisons of shift-by-constant.
1522 BinaryOperator *BO = cast<BinaryOperator>(LHSI);
1523 if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
1524 if (Instruction *Res = FoldICmpShrCst(ICI, BO, ShAmt))
1528 // Handle exact shr's.
1529 if (ICI.isEquality() && BO->isExact() && BO->hasOneUse()) {
1530 if (RHSV.isMinValue())
1531 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), RHS);
1536 case Instruction::SDiv:
1537 case Instruction::UDiv:
1538 // Fold: icmp pred ([us]div X, C1), C2 -> range test
1539 // Fold this div into the comparison, producing a range check.
1540 // Determine, based on the divide type, what the range is being
1541 // checked. If there is an overflow on the low or high side, remember
1542 // it, otherwise compute the range [low, hi) bounding the new value.
1543 // See: InsertRangeTest above for the kinds of replacements possible.
1544 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
1545 if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
1550 case Instruction::Sub: {
1551 ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(0));
1553 const APInt &LHSV = LHSC->getValue();
1555 // C1-X <u C2 -> (X|(C2-1)) == C1
1556 // iff C1 & (C2-1) == C2-1
1557 // C2 is a power of 2
1558 if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
1559 RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == (RHSV - 1))
1560 return new ICmpInst(ICmpInst::ICMP_EQ,
1561 Builder->CreateOr(LHSI->getOperand(1), RHSV - 1),
1564 // C1-X >u C2 -> (X|C2) != C1
1565 // iff C1 & C2 == C2
1566 // C2+1 is a power of 2
1567 if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
1568 (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == RHSV)
1569 return new ICmpInst(ICmpInst::ICMP_NE,
1570 Builder->CreateOr(LHSI->getOperand(1), RHSV), LHSC);
1574 case Instruction::Add:
1575 // Fold: icmp pred (add X, C1), C2
1576 if (!ICI.isEquality()) {
1577 ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1));
1579 const APInt &LHSV = LHSC->getValue();
1581 ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV)
1584 if (ICI.isSigned()) {
1585 if (CR.getLower().isSignBit()) {
1586 return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0),
1587 Builder->getInt(CR.getUpper()));
1588 } else if (CR.getUpper().isSignBit()) {
1589 return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0),
1590 Builder->getInt(CR.getLower()));
1593 if (CR.getLower().isMinValue()) {
1594 return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0),
1595 Builder->getInt(CR.getUpper()));
1596 } else if (CR.getUpper().isMinValue()) {
1597 return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0),
1598 Builder->getInt(CR.getLower()));
1602 // X-C1 <u C2 -> (X & -C2) == C1
1603 // iff C1 & (C2-1) == 0
1604 // C2 is a power of 2
1605 if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
1606 RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == 0)
1607 return new ICmpInst(ICmpInst::ICMP_EQ,
1608 Builder->CreateAnd(LHSI->getOperand(0), -RHSV),
1609 ConstantExpr::getNeg(LHSC));
1611 // X-C1 >u C2 -> (X & ~C2) != C1
1613 // C2+1 is a power of 2
1614 if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
1615 (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == 0)
1616 return new ICmpInst(ICmpInst::ICMP_NE,
1617 Builder->CreateAnd(LHSI->getOperand(0), ~RHSV),
1618 ConstantExpr::getNeg(LHSC));
1623 // Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
1624 if (ICI.isEquality()) {
1625 bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
1627 // If the first operand is (add|sub|and|or|xor|rem) with a constant, and
1628 // the second operand is a constant, simplify a bit.
1629 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) {
1630 switch (BO->getOpcode()) {
1631 case Instruction::SRem:
1632 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
1633 if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){
1634 const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue();
1635 if (V.sgt(1) && V.isPowerOf2()) {
1637 Builder->CreateURem(BO->getOperand(0), BO->getOperand(1),
1639 return new ICmpInst(ICI.getPredicate(), NewRem,
1640 Constant::getNullValue(BO->getType()));
1644 case Instruction::Add:
1645 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
1646 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1647 if (BO->hasOneUse())
1648 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1649 ConstantExpr::getSub(RHS, BOp1C));
1650 } else if (RHSV == 0) {
1651 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1652 // efficiently invertible, or if the add has just this one use.
1653 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1655 if (Value *NegVal = dyn_castNegVal(BOp1))
1656 return new ICmpInst(ICI.getPredicate(), BOp0, NegVal);
1657 if (Value *NegVal = dyn_castNegVal(BOp0))
1658 return new ICmpInst(ICI.getPredicate(), NegVal, BOp1);
1659 if (BO->hasOneUse()) {
1660 Value *Neg = Builder->CreateNeg(BOp1);
1662 return new ICmpInst(ICI.getPredicate(), BOp0, Neg);
1666 case Instruction::Xor:
1667 // For the xor case, we can xor two constants together, eliminating
1668 // the explicit xor.
1669 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1670 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1671 ConstantExpr::getXor(RHS, BOC));
1672 } else if (RHSV == 0) {
1673 // Replace ((xor A, B) != 0) with (A != B)
1674 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1678 case Instruction::Sub:
1679 // Replace ((sub A, B) != C) with (B != A-C) if A & C are constants.
1680 if (ConstantInt *BOp0C = dyn_cast<ConstantInt>(BO->getOperand(0))) {
1681 if (BO->hasOneUse())
1682 return new ICmpInst(ICI.getPredicate(), BO->getOperand(1),
1683 ConstantExpr::getSub(BOp0C, RHS));
1684 } else if (RHSV == 0) {
1685 // Replace ((sub A, B) != 0) with (A != B)
1686 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1690 case Instruction::Or:
1691 // If bits are being or'd in that are not present in the constant we
1692 // are comparing against, then the comparison could never succeed!
1693 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1694 Constant *NotCI = ConstantExpr::getNot(RHS);
1695 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
1696 return ReplaceInstUsesWith(ICI, Builder->getInt1(isICMP_NE));
1700 case Instruction::And:
1701 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1702 // If bits are being compared against that are and'd out, then the
1703 // comparison can never succeed!
1704 if ((RHSV & ~BOC->getValue()) != 0)
1705 return ReplaceInstUsesWith(ICI, Builder->getInt1(isICMP_NE));
1707 // If we have ((X & C) == C), turn it into ((X & C) != 0).
1708 if (RHS == BOC && RHSV.isPowerOf2())
1709 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ :
1710 ICmpInst::ICMP_NE, LHSI,
1711 Constant::getNullValue(RHS->getType()));
1713 // Don't perform the following transforms if the AND has multiple uses
1714 if (!BO->hasOneUse())
1717 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
1718 if (BOC->getValue().isSignBit()) {
1719 Value *X = BO->getOperand(0);
1720 Constant *Zero = Constant::getNullValue(X->getType());
1721 ICmpInst::Predicate pred = isICMP_NE ?
1722 ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
1723 return new ICmpInst(pred, X, Zero);
1726 // ((X & ~7) == 0) --> X < 8
1727 if (RHSV == 0 && isHighOnes(BOC)) {
1728 Value *X = BO->getOperand(0);
1729 Constant *NegX = ConstantExpr::getNeg(BOC);
1730 ICmpInst::Predicate pred = isICMP_NE ?
1731 ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
1732 return new ICmpInst(pred, X, NegX);
1736 case Instruction::Mul:
1737 if (RHSV == 0 && BO->hasNoSignedWrap()) {
1738 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1739 // The trivial case (mul X, 0) is handled by InstSimplify
1740 // General case : (mul X, C) != 0 iff X != 0
1741 // (mul X, C) == 0 iff X == 0
1743 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1744 Constant::getNullValue(RHS->getType()));
1750 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) {
1751 // Handle icmp {eq|ne} <intrinsic>, intcst.
1752 switch (II->getIntrinsicID()) {
1753 case Intrinsic::bswap:
1755 ICI.setOperand(0, II->getArgOperand(0));
1756 ICI.setOperand(1, Builder->getInt(RHSV.byteSwap()));
1758 case Intrinsic::ctlz:
1759 case Intrinsic::cttz:
1760 // ctz(A) == bitwidth(a) -> A == 0 and likewise for !=
1761 if (RHSV == RHS->getType()->getBitWidth()) {
1763 ICI.setOperand(0, II->getArgOperand(0));
1764 ICI.setOperand(1, ConstantInt::get(RHS->getType(), 0));
1768 case Intrinsic::ctpop:
1769 // popcount(A) == 0 -> A == 0 and likewise for !=
1770 if (RHS->isZero()) {
1772 ICI.setOperand(0, II->getArgOperand(0));
1773 ICI.setOperand(1, RHS);
1785 /// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst).
1786 /// We only handle extending casts so far.
1788 Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) {
1789 const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0));
1790 Value *LHSCIOp = LHSCI->getOperand(0);
1791 Type *SrcTy = LHSCIOp->getType();
1792 Type *DestTy = LHSCI->getType();
1795 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
1796 // integer type is the same size as the pointer type.
1797 if (DL && LHSCI->getOpcode() == Instruction::PtrToInt &&
1798 DL->getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
1799 Value *RHSOp = nullptr;
1800 if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
1801 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
1802 } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
1803 RHSOp = RHSC->getOperand(0);
1804 // If the pointer types don't match, insert a bitcast.
1805 if (LHSCIOp->getType() != RHSOp->getType())
1806 RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
1810 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);
1813 // The code below only handles extension cast instructions, so far.
1815 if (LHSCI->getOpcode() != Instruction::ZExt &&
1816 LHSCI->getOpcode() != Instruction::SExt)
1819 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
1820 bool isSignedCmp = ICI.isSigned();
1822 if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) {
1823 // Not an extension from the same type?
1824 RHSCIOp = CI->getOperand(0);
1825 if (RHSCIOp->getType() != LHSCIOp->getType())
1828 // If the signedness of the two casts doesn't agree (i.e. one is a sext
1829 // and the other is a zext), then we can't handle this.
1830 if (CI->getOpcode() != LHSCI->getOpcode())
1833 // Deal with equality cases early.
1834 if (ICI.isEquality())
1835 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
1837 // A signed comparison of sign extended values simplifies into a
1838 // signed comparison.
1839 if (isSignedCmp && isSignedExt)
1840 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
1842 // The other three cases all fold into an unsigned comparison.
1843 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
1846 // If we aren't dealing with a constant on the RHS, exit early
1847 ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1));
1851 // Compute the constant that would happen if we truncated to SrcTy then
1852 // reextended to DestTy.
1853 Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy);
1854 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(),
1857 // If the re-extended constant didn't change...
1859 // Deal with equality cases early.
1860 if (ICI.isEquality())
1861 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
1863 // A signed comparison of sign extended values simplifies into a
1864 // signed comparison.
1865 if (isSignedExt && isSignedCmp)
1866 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
1868 // The other three cases all fold into an unsigned comparison.
1869 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1);
1872 // The re-extended constant changed so the constant cannot be represented
1873 // in the shorter type. Consequently, we cannot emit a simple comparison.
1874 // All the cases that fold to true or false will have already been handled
1875 // by SimplifyICmpInst, so only deal with the tricky case.
1877 if (isSignedCmp || !isSignedExt)
1880 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
1881 // should have been folded away previously and not enter in here.
1883 // We're performing an unsigned comp with a sign extended value.
1884 // This is true if the input is >= 0. [aka >s -1]
1885 Constant *NegOne = Constant::getAllOnesValue(SrcTy);
1886 Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName());
1888 // Finally, return the value computed.
1889 if (ICI.getPredicate() == ICmpInst::ICMP_ULT)
1890 return ReplaceInstUsesWith(ICI, Result);
1892 assert(ICI.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
1893 return BinaryOperator::CreateNot(Result);
1896 /// ProcessUGT_ADDCST_ADD - The caller has matched a pattern of the form:
1897 /// I = icmp ugt (add (add A, B), CI2), CI1
1898 /// If this is of the form:
1900 /// if (sum+128 >u 255)
1901 /// Then replace it with llvm.sadd.with.overflow.i8.
1903 static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
1904 ConstantInt *CI2, ConstantInt *CI1,
1906 // The transformation we're trying to do here is to transform this into an
1907 // llvm.sadd.with.overflow. To do this, we have to replace the original add
1908 // with a narrower add, and discard the add-with-constant that is part of the
1909 // range check (if we can't eliminate it, this isn't profitable).
1911 // In order to eliminate the add-with-constant, the compare can be its only
1913 Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1914 if (!AddWithCst->hasOneUse()) return nullptr;
1916 // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1917 if (!CI2->getValue().isPowerOf2()) return nullptr;
1918 unsigned NewWidth = CI2->getValue().countTrailingZeros();
1919 if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31) return nullptr;
1921 // The width of the new add formed is 1 more than the bias.
1924 // Check to see that CI1 is an all-ones value with NewWidth bits.
1925 if (CI1->getBitWidth() == NewWidth ||
1926 CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1929 // This is only really a signed overflow check if the inputs have been
1930 // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1931 // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1932 unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1933 if (IC.ComputeNumSignBits(A) < NeededSignBits ||
1934 IC.ComputeNumSignBits(B) < NeededSignBits)
1937 // In order to replace the original add with a narrower
1938 // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1939 // and truncates that discard the high bits of the add. Verify that this is
1941 Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1942 for (User *U : OrigAdd->users()) {
1943 if (U == AddWithCst) continue;
1945 // Only accept truncates for now. We would really like a nice recursive
1946 // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1947 // chain to see which bits of a value are actually demanded. If the
1948 // original add had another add which was then immediately truncated, we
1949 // could still do the transformation.
1950 TruncInst *TI = dyn_cast<TruncInst>(U);
1951 if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth)
1955 // If the pattern matches, truncate the inputs to the narrower type and
1956 // use the sadd_with_overflow intrinsic to efficiently compute both the
1957 // result and the overflow bit.
1958 Module *M = I.getParent()->getParent()->getParent();
1960 Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1961 Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow,
1964 InstCombiner::BuilderTy *Builder = IC.Builder;
1966 // Put the new code above the original add, in case there are any uses of the
1967 // add between the add and the compare.
1968 Builder->SetInsertPoint(OrigAdd);
1970 Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc");
1971 Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc");
1972 CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB, "sadd");
1973 Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result");
1974 Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType());
1976 // The inner add was the result of the narrow add, zero extended to the
1977 // wider type. Replace it with the result computed by the intrinsic.
1978 IC.ReplaceInstUsesWith(*OrigAdd, ZExt);
1980 // The original icmp gets replaced with the overflow value.
1981 return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1984 static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV,
1986 // Don't bother doing this transformation for pointers, don't do it for
1988 if (!isa<IntegerType>(OrigAddV->getType())) return nullptr;
1990 // If the add is a constant expr, then we don't bother transforming it.
1991 Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV);
1992 if (!OrigAdd) return nullptr;
1994 Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1);
1996 // Put the new code above the original add, in case there are any uses of the
1997 // add between the add and the compare.
1998 InstCombiner::BuilderTy *Builder = IC.Builder;
1999 Builder->SetInsertPoint(OrigAdd);
2001 Module *M = I.getParent()->getParent()->getParent();
2002 Type *Ty = LHS->getType();
2003 Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
2004 CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd");
2005 Value *Add = Builder->CreateExtractValue(Call, 0);
2007 IC.ReplaceInstUsesWith(*OrigAdd, Add);
2009 // The original icmp gets replaced with the overflow value.
2010 return ExtractValueInst::Create(Call, 1, "uadd.overflow");
2013 /// \brief Recognize and process idiom involving test for multiplication
2016 /// The caller has matched a pattern of the form:
2017 /// I = cmp u (mul(zext A, zext B), V
2018 /// The function checks if this is a test for overflow and if so replaces
2019 /// multiplication with call to 'mul.with.overflow' intrinsic.
2021 /// \param I Compare instruction.
2022 /// \param MulVal Result of 'mult' instruction. It is one of the arguments of
2023 /// the compare instruction. Must be of integer type.
2024 /// \param OtherVal The other argument of compare instruction.
2025 /// \returns Instruction which must replace the compare instruction, NULL if no
2026 /// replacement required.
2027 static Instruction *ProcessUMulZExtIdiom(ICmpInst &I, Value *MulVal,
2028 Value *OtherVal, InstCombiner &IC) {
2029 assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal);
2030 assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal);
2031 assert(isa<IntegerType>(MulVal->getType()));
2032 Instruction *MulInstr = cast<Instruction>(MulVal);
2033 assert(MulInstr->getOpcode() == Instruction::Mul);
2035 Instruction *LHS = cast<Instruction>(MulInstr->getOperand(0)),
2036 *RHS = cast<Instruction>(MulInstr->getOperand(1));
2037 assert(LHS->getOpcode() == Instruction::ZExt);
2038 assert(RHS->getOpcode() == Instruction::ZExt);
2039 Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);
2041 // Calculate type and width of the result produced by mul.with.overflow.
2042 Type *TyA = A->getType(), *TyB = B->getType();
2043 unsigned WidthA = TyA->getPrimitiveSizeInBits(),
2044 WidthB = TyB->getPrimitiveSizeInBits();
2047 if (WidthB > WidthA) {
2055 // In order to replace the original mul with a narrower mul.with.overflow,
2056 // all uses must ignore upper bits of the product. The number of used low
2057 // bits must be not greater than the width of mul.with.overflow.
2058 if (MulVal->hasNUsesOrMore(2))
2059 for (User *U : MulVal->users()) {
2062 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
2063 // Check if truncation ignores bits above MulWidth.
2064 unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits();
2065 if (TruncWidth > MulWidth)
2067 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
2068 // Check if AND ignores bits above MulWidth.
2069 if (BO->getOpcode() != Instruction::And)
2071 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) {
2072 const APInt &CVal = CI->getValue();
2073 if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth)
2077 // Other uses prohibit this transformation.
2082 // Recognize patterns
2083 switch (I.getPredicate()) {
2084 case ICmpInst::ICMP_EQ:
2085 case ICmpInst::ICMP_NE:
2086 // Recognize pattern:
2087 // mulval = mul(zext A, zext B)
2088 // cmp eq/neq mulval, zext trunc mulval
2089 if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal))
2090 if (Zext->hasOneUse()) {
2091 Value *ZextArg = Zext->getOperand(0);
2092 if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg))
2093 if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth)
2097 // Recognize pattern:
2098 // mulval = mul(zext A, zext B)
2099 // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits.
2102 if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) {
2103 if (ValToMask != MulVal)
2105 const APInt &CVal = CI->getValue() + 1;
2106 if (CVal.isPowerOf2()) {
2107 unsigned MaskWidth = CVal.logBase2();
2108 if (MaskWidth == MulWidth)
2109 break; // Recognized
2114 case ICmpInst::ICMP_UGT:
2115 // Recognize pattern:
2116 // mulval = mul(zext A, zext B)
2117 // cmp ugt mulval, max
2118 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
2119 APInt MaxVal = APInt::getMaxValue(MulWidth);
2120 MaxVal = MaxVal.zext(CI->getBitWidth());
2121 if (MaxVal.eq(CI->getValue()))
2122 break; // Recognized
2126 case ICmpInst::ICMP_UGE:
2127 // Recognize pattern:
2128 // mulval = mul(zext A, zext B)
2129 // cmp uge mulval, max+1
2130 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
2131 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
2132 if (MaxVal.eq(CI->getValue()))
2133 break; // Recognized
2137 case ICmpInst::ICMP_ULE:
2138 // Recognize pattern:
2139 // mulval = mul(zext A, zext B)
2140 // cmp ule mulval, max
2141 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
2142 APInt MaxVal = APInt::getMaxValue(MulWidth);
2143 MaxVal = MaxVal.zext(CI->getBitWidth());
2144 if (MaxVal.eq(CI->getValue()))
2145 break; // Recognized
2149 case ICmpInst::ICMP_ULT:
2150 // Recognize pattern:
2151 // mulval = mul(zext A, zext B)
2152 // cmp ule mulval, max + 1
2153 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) {
2154 APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth);
2155 if (MaxVal.eq(CI->getValue()))
2156 break; // Recognized
2164 InstCombiner::BuilderTy *Builder = IC.Builder;
2165 Builder->SetInsertPoint(MulInstr);
2166 Module *M = I.getParent()->getParent()->getParent();
2168 // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B)
2169 Value *MulA = A, *MulB = B;
2170 if (WidthA < MulWidth)
2171 MulA = Builder->CreateZExt(A, MulType);
2172 if (WidthB < MulWidth)
2173 MulB = Builder->CreateZExt(B, MulType);
2175 Intrinsic::getDeclaration(M, Intrinsic::umul_with_overflow, MulType);
2176 CallInst *Call = Builder->CreateCall2(F, MulA, MulB, "umul");
2177 IC.Worklist.Add(MulInstr);
2179 // If there are uses of mul result other than the comparison, we know that
2180 // they are truncation or binary AND. Change them to use result of
2181 // mul.with.overflow and adjust properly mask/size.
2182 if (MulVal->hasNUsesOrMore(2)) {
2183 Value *Mul = Builder->CreateExtractValue(Call, 0, "umul.value");
2184 for (User *U : MulVal->users()) {
2185 if (U == &I || U == OtherVal)
2187 if (TruncInst *TI = dyn_cast<TruncInst>(U)) {
2188 if (TI->getType()->getPrimitiveSizeInBits() == MulWidth)
2189 IC.ReplaceInstUsesWith(*TI, Mul);
2191 TI->setOperand(0, Mul);
2192 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) {
2193 assert(BO->getOpcode() == Instruction::And);
2194 // Replace (mul & mask) --> zext (mul.with.overflow & short_mask)
2195 ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));
2196 APInt ShortMask = CI->getValue().trunc(MulWidth);
2197 Value *ShortAnd = Builder->CreateAnd(Mul, ShortMask);
2199 cast<Instruction>(Builder->CreateZExt(ShortAnd, BO->getType()));
2200 IC.Worklist.Add(Zext);
2201 IC.ReplaceInstUsesWith(*BO, Zext);
2203 llvm_unreachable("Unexpected Binary operation");
2205 IC.Worklist.Add(cast<Instruction>(U));
2208 if (isa<Instruction>(OtherVal))
2209 IC.Worklist.Add(cast<Instruction>(OtherVal));
2211 // The original icmp gets replaced with the overflow value, maybe inverted
2212 // depending on predicate.
2213 bool Inverse = false;
2214 switch (I.getPredicate()) {
2215 case ICmpInst::ICMP_NE:
2217 case ICmpInst::ICMP_EQ:
2220 case ICmpInst::ICMP_UGT:
2221 case ICmpInst::ICMP_UGE:
2222 if (I.getOperand(0) == MulVal)
2226 case ICmpInst::ICMP_ULT:
2227 case ICmpInst::ICMP_ULE:
2228 if (I.getOperand(1) == MulVal)
2233 llvm_unreachable("Unexpected predicate");
2236 Value *Res = Builder->CreateExtractValue(Call, 1);
2237 return BinaryOperator::CreateNot(Res);
2240 return ExtractValueInst::Create(Call, 1);
2243 // DemandedBitsLHSMask - When performing a comparison against a constant,
2244 // it is possible that not all the bits in the LHS are demanded. This helper
2245 // method computes the mask that IS demanded.
2246 static APInt DemandedBitsLHSMask(ICmpInst &I,
2247 unsigned BitWidth, bool isSignCheck) {
2249 return APInt::getSignBit(BitWidth);
2251 ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(1));
2252 if (!CI) return APInt::getAllOnesValue(BitWidth);
2253 const APInt &RHS = CI->getValue();
2255 switch (I.getPredicate()) {
2256 // For a UGT comparison, we don't care about any bits that
2257 // correspond to the trailing ones of the comparand. The value of these
2258 // bits doesn't impact the outcome of the comparison, because any value
2259 // greater than the RHS must differ in a bit higher than these due to carry.
2260 case ICmpInst::ICMP_UGT: {
2261 unsigned trailingOnes = RHS.countTrailingOnes();
2262 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingOnes);
2266 // Similarly, for a ULT comparison, we don't care about the trailing zeros.
2267 // Any value less than the RHS must differ in a higher bit because of carries.
2268 case ICmpInst::ICMP_ULT: {
2269 unsigned trailingZeros = RHS.countTrailingZeros();
2270 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingZeros);
2275 return APInt::getAllOnesValue(BitWidth);
2280 /// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst
2281 /// should be swapped.
2282 /// The decision is based on how many times these two operands are reused
2283 /// as subtract operands and their positions in those instructions.
2284 /// The rational is that several architectures use the same instruction for
2285 /// both subtract and cmp, thus it is better if the order of those operands
2287 /// \return true if Op0 and Op1 should be swapped.
2288 static bool swapMayExposeCSEOpportunities(const Value * Op0,
2289 const Value * Op1) {
2290 // Filter out pointer value as those cannot appears directly in subtract.
2291 // FIXME: we may want to go through inttoptrs or bitcasts.
2292 if (Op0->getType()->isPointerTy())
2294 // Count every uses of both Op0 and Op1 in a subtract.
2295 // Each time Op0 is the first operand, count -1: swapping is bad, the
2296 // subtract has already the same layout as the compare.
2297 // Each time Op0 is the second operand, count +1: swapping is good, the
2298 // subtract has a different layout as the compare.
2299 // At the end, if the benefit is greater than 0, Op0 should come second to
2300 // expose more CSE opportunities.
2301 int GlobalSwapBenefits = 0;
2302 for (const User *U : Op0->users()) {
2303 const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U);
2304 if (!BinOp || BinOp->getOpcode() != Instruction::Sub)
2306 // If Op0 is the first argument, this is not beneficial to swap the
2308 int LocalSwapBenefits = -1;
2309 unsigned Op1Idx = 1;
2310 if (BinOp->getOperand(Op1Idx) == Op0) {
2312 LocalSwapBenefits = 1;
2314 if (BinOp->getOperand(Op1Idx) != Op1)
2316 GlobalSwapBenefits += LocalSwapBenefits;
2318 return GlobalSwapBenefits > 0;
2321 Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
2322 bool Changed = false;
2323 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2324 unsigned Op0Cplxity = getComplexity(Op0);
2325 unsigned Op1Cplxity = getComplexity(Op1);
2327 /// Orders the operands of the compare so that they are listed from most
2328 /// complex to least complex. This puts constants before unary operators,
2329 /// before binary operators.
2330 if (Op0Cplxity < Op1Cplxity ||
2331 (Op0Cplxity == Op1Cplxity &&
2332 swapMayExposeCSEOpportunities(Op0, Op1))) {
2334 std::swap(Op0, Op1);
2338 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL))
2339 return ReplaceInstUsesWith(I, V);
2341 // comparing -val or val with non-zero is the same as just comparing val
2342 // ie, abs(val) != 0 -> val != 0
2343 if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero()))
2345 Value *Cond, *SelectTrue, *SelectFalse;
2346 if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
2347 m_Value(SelectFalse)))) {
2348 if (Value *V = dyn_castNegVal(SelectTrue)) {
2349 if (V == SelectFalse)
2350 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
2352 else if (Value *V = dyn_castNegVal(SelectFalse)) {
2353 if (V == SelectTrue)
2354 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
2359 Type *Ty = Op0->getType();
2361 // icmp's with boolean values can always be turned into bitwise operations
2362 if (Ty->isIntegerTy(1)) {
2363 switch (I.getPredicate()) {
2364 default: llvm_unreachable("Invalid icmp instruction!");
2365 case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B)
2366 Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp");
2367 return BinaryOperator::CreateNot(Xor);
2369 case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B
2370 return BinaryOperator::CreateXor(Op0, Op1);
2372 case ICmpInst::ICMP_UGT:
2373 std::swap(Op0, Op1); // Change icmp ugt -> icmp ult
2375 case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B
2376 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
2377 return BinaryOperator::CreateAnd(Not, Op1);
2379 case ICmpInst::ICMP_SGT:
2380 std::swap(Op0, Op1); // Change icmp sgt -> icmp slt
2382 case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B
2383 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
2384 return BinaryOperator::CreateAnd(Not, Op0);
2386 case ICmpInst::ICMP_UGE:
2387 std::swap(Op0, Op1); // Change icmp uge -> icmp ule
2389 case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B
2390 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
2391 return BinaryOperator::CreateOr(Not, Op1);
2393 case ICmpInst::ICMP_SGE:
2394 std::swap(Op0, Op1); // Change icmp sge -> icmp sle
2396 case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B
2397 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
2398 return BinaryOperator::CreateOr(Not, Op0);
2403 unsigned BitWidth = 0;
2404 if (Ty->isIntOrIntVectorTy())
2405 BitWidth = Ty->getScalarSizeInBits();
2406 else if (DL) // Pointers require DL info to get their size.
2407 BitWidth = DL->getTypeSizeInBits(Ty->getScalarType());
2409 bool isSignBit = false;
2411 // See if we are doing a comparison with a constant.
2412 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2413 Value *A = nullptr, *B = nullptr;
2415 // Match the following pattern, which is a common idiom when writing
2416 // overflow-safe integer arithmetic function. The source performs an
2417 // addition in wider type, and explicitly checks for overflow using
2418 // comparisons against INT_MIN and INT_MAX. Simplify this by using the
2419 // sadd_with_overflow intrinsic.
2421 // TODO: This could probably be generalized to handle other overflow-safe
2422 // operations if we worked out the formulas to compute the appropriate
2426 // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
2428 ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
2429 if (I.getPredicate() == ICmpInst::ICMP_UGT &&
2430 match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
2431 if (Instruction *Res = ProcessUGT_ADDCST_ADD(I, A, B, CI2, CI, *this))
2435 // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
2436 if (I.isEquality() && CI->isZero() &&
2437 match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
2438 // (icmp cond A B) if cond is equality
2439 return new ICmpInst(I.getPredicate(), A, B);
2442 // If we have an icmp le or icmp ge instruction, turn it into the
2443 // appropriate icmp lt or icmp gt instruction. This allows us to rely on
2444 // them being folded in the code below. The SimplifyICmpInst code has
2445 // already handled the edge cases for us, so we just assert on them.
2446 switch (I.getPredicate()) {
2448 case ICmpInst::ICMP_ULE:
2449 assert(!CI->isMaxValue(false)); // A <=u MAX -> TRUE
2450 return new ICmpInst(ICmpInst::ICMP_ULT, Op0,
2451 Builder->getInt(CI->getValue()+1));
2452 case ICmpInst::ICMP_SLE:
2453 assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE
2454 return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
2455 Builder->getInt(CI->getValue()+1));
2456 case ICmpInst::ICMP_UGE:
2457 assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE
2458 return new ICmpInst(ICmpInst::ICMP_UGT, Op0,
2459 Builder->getInt(CI->getValue()-1));
2460 case ICmpInst::ICMP_SGE:
2461 assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE
2462 return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
2463 Builder->getInt(CI->getValue()-1));
2466 // If this comparison is a normal comparison, it demands all
2467 // bits, if it is a sign bit comparison, it only demands the sign bit.
2469 isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
2472 // See if we can fold the comparison based on range information we can get
2473 // by checking whether bits are known to be zero or one in the input.
2474 if (BitWidth != 0) {
2475 APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0);
2476 APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0);
2478 if (SimplifyDemandedBits(I.getOperandUse(0),
2479 DemandedBitsLHSMask(I, BitWidth, isSignBit),
2480 Op0KnownZero, Op0KnownOne, 0))
2482 if (SimplifyDemandedBits(I.getOperandUse(1),
2483 APInt::getAllOnesValue(BitWidth),
2484 Op1KnownZero, Op1KnownOne, 0))
2487 // Given the known and unknown bits, compute a range that the LHS could be
2488 // in. Compute the Min, Max and RHS values based on the known bits. For the
2489 // EQ and NE we use unsigned values.
2490 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
2491 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
2493 ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
2495 ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
2498 ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
2500 ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
2504 // If Min and Max are known to be the same, then SimplifyDemandedBits
2505 // figured out that the LHS is a constant. Just constant fold this now so
2506 // that code below can assume that Min != Max.
2507 if (!isa<Constant>(Op0) && Op0Min == Op0Max)
2508 return new ICmpInst(I.getPredicate(),
2509 ConstantInt::get(Op0->getType(), Op0Min), Op1);
2510 if (!isa<Constant>(Op1) && Op1Min == Op1Max)
2511 return new ICmpInst(I.getPredicate(), Op0,
2512 ConstantInt::get(Op1->getType(), Op1Min));
2514 // Based on the range information we know about the LHS, see if we can
2515 // simplify this comparison. For example, (x&4) < 8 is always true.
2516 switch (I.getPredicate()) {
2517 default: llvm_unreachable("Unknown icmp opcode!");
2518 case ICmpInst::ICMP_EQ: {
2519 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
2520 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2522 // If all bits are known zero except for one, then we know at most one
2523 // bit is set. If the comparison is against zero, then this is a check
2524 // to see if *that* bit is set.
2525 APInt Op0KnownZeroInverted = ~Op0KnownZero;
2526 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
2527 // If the LHS is an AND with the same constant, look through it.
2528 Value *LHS = nullptr;
2529 ConstantInt *LHSC = nullptr;
2530 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
2531 LHSC->getValue() != Op0KnownZeroInverted)
2534 // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
2535 // then turn "((1 << x)&8) == 0" into "x != 3".
2537 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
2538 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
2539 return new ICmpInst(ICmpInst::ICMP_NE, X,
2540 ConstantInt::get(X->getType(), CmpVal));
2543 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
2544 // then turn "((8 >>u x)&1) == 0" into "x != 3".
2546 if (Op0KnownZeroInverted == 1 &&
2547 match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
2548 return new ICmpInst(ICmpInst::ICMP_NE, X,
2549 ConstantInt::get(X->getType(),
2550 CI->countTrailingZeros()));
2555 case ICmpInst::ICMP_NE: {
2556 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
2557 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2559 // If all bits are known zero except for one, then we know at most one
2560 // bit is set. If the comparison is against zero, then this is a check
2561 // to see if *that* bit is set.
2562 APInt Op0KnownZeroInverted = ~Op0KnownZero;
2563 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
2564 // If the LHS is an AND with the same constant, look through it.
2565 Value *LHS = nullptr;
2566 ConstantInt *LHSC = nullptr;
2567 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
2568 LHSC->getValue() != Op0KnownZeroInverted)
2571 // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
2572 // then turn "((1 << x)&8) != 0" into "x == 3".
2574 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
2575 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
2576 return new ICmpInst(ICmpInst::ICMP_EQ, X,
2577 ConstantInt::get(X->getType(), CmpVal));
2580 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
2581 // then turn "((8 >>u x)&1) != 0" into "x == 3".
2583 if (Op0KnownZeroInverted == 1 &&
2584 match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
2585 return new ICmpInst(ICmpInst::ICMP_EQ, X,
2586 ConstantInt::get(X->getType(),
2587 CI->countTrailingZeros()));
2592 case ICmpInst::ICMP_ULT:
2593 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
2594 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2595 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
2596 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2597 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
2598 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2599 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2600 if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C
2601 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2602 Builder->getInt(CI->getValue()-1));
2604 // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
2605 if (CI->isMinValue(true))
2606 return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
2607 Constant::getAllOnesValue(Op0->getType()));
2610 case ICmpInst::ICMP_UGT:
2611 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
2612 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2613 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
2614 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2616 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
2617 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2618 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2619 if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C
2620 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2621 Builder->getInt(CI->getValue()+1));
2623 // (x >u 2147483647) -> (x <s 0) -> true if sign bit set
2624 if (CI->isMaxValue(true))
2625 return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
2626 Constant::getNullValue(Op0->getType()));
2629 case ICmpInst::ICMP_SLT:
2630 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
2631 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2632 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
2633 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2634 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
2635 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2636 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2637 if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C
2638 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2639 Builder->getInt(CI->getValue()-1));
2642 case ICmpInst::ICMP_SGT:
2643 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
2644 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2645 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
2646 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2648 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
2649 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2650 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2651 if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C
2652 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2653 Builder->getInt(CI->getValue()+1));
2656 case ICmpInst::ICMP_SGE:
2657 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
2658 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
2659 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2660 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
2661 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2663 case ICmpInst::ICMP_SLE:
2664 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
2665 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
2666 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2667 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
2668 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2670 case ICmpInst::ICMP_UGE:
2671 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
2672 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
2673 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2674 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
2675 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2677 case ICmpInst::ICMP_ULE:
2678 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
2679 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
2680 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2681 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
2682 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2686 // Turn a signed comparison into an unsigned one if both operands
2687 // are known to have the same sign.
2689 ((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) ||
2690 (Op0KnownOne.isNegative() && Op1KnownOne.isNegative())))
2691 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
2694 // Test if the ICmpInst instruction is used exclusively by a select as
2695 // part of a minimum or maximum operation. If so, refrain from doing
2696 // any other folding. This helps out other analyses which understand
2697 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
2698 // and CodeGen. And in this case, at least one of the comparison
2699 // operands has at least one user besides the compare (the select),
2700 // which would often largely negate the benefit of folding anyway.
2702 if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin()))
2703 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
2704 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
2707 // See if we are doing a comparison between a constant and an instruction that
2708 // can be folded into the comparison.
2709 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2710 // Since the RHS is a ConstantInt (CI), if the left hand side is an
2711 // instruction, see if that instruction also has constants so that the
2712 // instruction can be folded into the icmp
2713 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2714 if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI))
2718 // Handle icmp with constant (but not simple integer constant) RHS
2719 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
2720 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2721 switch (LHSI->getOpcode()) {
2722 case Instruction::GetElementPtr:
2723 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2724 if (RHSC->isNullValue() &&
2725 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2726 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
2727 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2729 case Instruction::PHI:
2730 // Only fold icmp into the PHI if the phi and icmp are in the same
2731 // block. If in the same block, we're encouraging jump threading. If
2732 // not, we are just pessimizing the code by making an i1 phi.
2733 if (LHSI->getParent() == I.getParent())
2734 if (Instruction *NV = FoldOpIntoPhi(I))
2737 case Instruction::Select: {
2738 // If either operand of the select is a constant, we can fold the
2739 // comparison into the select arms, which will cause one to be
2740 // constant folded and the select turned into a bitwise or.
2741 Value *Op1 = nullptr, *Op2 = nullptr;
2742 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1)))
2743 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2744 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2)))
2745 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2747 // We only want to perform this transformation if it will not lead to
2748 // additional code. This is true if either both sides of the select
2749 // fold to a constant (in which case the icmp is replaced with a select
2750 // which will usually simplify) or this is the only user of the
2751 // select (in which case we are trading a select+icmp for a simpler
2753 if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) {
2755 Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1),
2758 Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2),
2760 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2764 case Instruction::IntToPtr:
2765 // icmp pred inttoptr(X), null -> icmp pred X, 0
2766 if (RHSC->isNullValue() && DL &&
2767 DL->getIntPtrType(RHSC->getType()) ==
2768 LHSI->getOperand(0)->getType())
2769 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
2770 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2773 case Instruction::Load:
2774 // Try to optimize things like "A[i] > 4" to index computations.
2775 if (GetElementPtrInst *GEP =
2776 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2777 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2778 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2779 !cast<LoadInst>(LHSI)->isVolatile())
2780 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
2787 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
2788 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
2789 if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I))
2791 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
2792 if (Instruction *NI = FoldGEPICmp(GEP, Op0,
2793 ICmpInst::getSwappedPredicate(I.getPredicate()), I))
2796 // Test to see if the operands of the icmp are casted versions of other
2797 // values. If the ptr->ptr cast can be stripped off both arguments, we do so
2799 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
2800 if (Op0->getType()->isPointerTy() &&
2801 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
2802 // We keep moving the cast from the left operand over to the right
2803 // operand, where it can often be eliminated completely.
2804 Op0 = CI->getOperand(0);
2806 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
2807 // so eliminate it as well.
2808 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
2809 Op1 = CI2->getOperand(0);
2811 // If Op1 is a constant, we can fold the cast into the constant.
2812 if (Op0->getType() != Op1->getType()) {
2813 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
2814 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
2816 // Otherwise, cast the RHS right before the icmp
2817 Op1 = Builder->CreateBitCast(Op1, Op0->getType());
2820 return new ICmpInst(I.getPredicate(), Op0, Op1);
2824 if (isa<CastInst>(Op0)) {
2825 // Handle the special case of: icmp (cast bool to X), <cst>
2826 // This comes up when you have code like
2829 // For generality, we handle any zero-extension of any operand comparison
2830 // with a constant or another cast from the same type.
2831 if (isa<Constant>(Op1) || isa<CastInst>(Op1))
2832 if (Instruction *R = visitICmpInstWithCastAndCast(I))
2836 // Special logic for binary operators.
2837 BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2838 BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2840 CmpInst::Predicate Pred = I.getPredicate();
2841 bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2842 if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2843 NoOp0WrapProblem = ICmpInst::isEquality(Pred) ||
2844 (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2845 (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2846 if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2847 NoOp1WrapProblem = ICmpInst::isEquality(Pred) ||
2848 (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2849 (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2851 // Analyze the case when either Op0 or Op1 is an add instruction.
2852 // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2853 Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr;
2854 if (BO0 && BO0->getOpcode() == Instruction::Add)
2855 A = BO0->getOperand(0), B = BO0->getOperand(1);
2856 if (BO1 && BO1->getOpcode() == Instruction::Add)
2857 C = BO1->getOperand(0), D = BO1->getOperand(1);
2859 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2860 if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2861 return new ICmpInst(Pred, A == Op1 ? B : A,
2862 Constant::getNullValue(Op1->getType()));
2864 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2865 if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2866 return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2869 // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2870 if (A && C && (A == C || A == D || B == C || B == D) &&
2871 NoOp0WrapProblem && NoOp1WrapProblem &&
2872 // Try not to increase register pressure.
2873 BO0->hasOneUse() && BO1->hasOneUse()) {
2874 // Determine Y and Z in the form icmp (X+Y), (X+Z).
2877 // C + B == C + D -> B == D
2880 } else if (A == D) {
2881 // D + B == C + D -> B == C
2884 } else if (B == C) {
2885 // A + C == C + D -> A == D
2890 // A + D == C + D -> A == C
2894 return new ICmpInst(Pred, Y, Z);
2897 // icmp slt (X + -1), Y -> icmp sle X, Y
2898 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT &&
2899 match(B, m_AllOnes()))
2900 return new ICmpInst(CmpInst::ICMP_SLE, A, Op1);
2902 // icmp sge (X + -1), Y -> icmp sgt X, Y
2903 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE &&
2904 match(B, m_AllOnes()))
2905 return new ICmpInst(CmpInst::ICMP_SGT, A, Op1);
2907 // icmp sle (X + 1), Y -> icmp slt X, Y
2908 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE &&
2910 return new ICmpInst(CmpInst::ICMP_SLT, A, Op1);
2912 // icmp sgt (X + 1), Y -> icmp sge X, Y
2913 if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT &&
2915 return new ICmpInst(CmpInst::ICMP_SGE, A, Op1);
2917 // if C1 has greater magnitude than C2:
2918 // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y
2919 // s.t. C3 = C1 - C2
2921 // if C2 has greater magnitude than C1:
2922 // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3)
2923 // s.t. C3 = C2 - C1
2924 if (A && C && NoOp0WrapProblem && NoOp1WrapProblem &&
2925 (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned())
2926 if (ConstantInt *C1 = dyn_cast<ConstantInt>(B))
2927 if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) {
2928 const APInt &AP1 = C1->getValue();
2929 const APInt &AP2 = C2->getValue();
2930 if (AP1.isNegative() == AP2.isNegative()) {
2931 APInt AP1Abs = C1->getValue().abs();
2932 APInt AP2Abs = C2->getValue().abs();
2933 if (AP1Abs.uge(AP2Abs)) {
2934 ConstantInt *C3 = Builder->getInt(AP1 - AP2);
2935 Value *NewAdd = Builder->CreateNSWAdd(A, C3);
2936 return new ICmpInst(Pred, NewAdd, C);
2938 ConstantInt *C3 = Builder->getInt(AP2 - AP1);
2939 Value *NewAdd = Builder->CreateNSWAdd(C, C3);
2940 return new ICmpInst(Pred, A, NewAdd);
2946 // Analyze the case when either Op0 or Op1 is a sub instruction.
2947 // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
2948 A = nullptr; B = nullptr; C = nullptr; D = nullptr;
2949 if (BO0 && BO0->getOpcode() == Instruction::Sub)
2950 A = BO0->getOperand(0), B = BO0->getOperand(1);
2951 if (BO1 && BO1->getOpcode() == Instruction::Sub)
2952 C = BO1->getOperand(0), D = BO1->getOperand(1);
2954 // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
2955 if (A == Op1 && NoOp0WrapProblem)
2956 return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
2958 // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
2959 if (C == Op0 && NoOp1WrapProblem)
2960 return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
2962 // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
2963 if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
2964 // Try not to increase register pressure.
2965 BO0->hasOneUse() && BO1->hasOneUse())
2966 return new ICmpInst(Pred, A, C);
2968 // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
2969 if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
2970 // Try not to increase register pressure.
2971 BO0->hasOneUse() && BO1->hasOneUse())
2972 return new ICmpInst(Pred, D, B);
2974 BinaryOperator *SRem = nullptr;
2975 // icmp (srem X, Y), Y
2976 if (BO0 && BO0->getOpcode() == Instruction::SRem &&
2977 Op1 == BO0->getOperand(1))
2979 // icmp Y, (srem X, Y)
2980 else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
2981 Op0 == BO1->getOperand(1))
2984 // We don't check hasOneUse to avoid increasing register pressure because
2985 // the value we use is the same value this instruction was already using.
2986 switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
2988 case ICmpInst::ICMP_EQ:
2989 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2990 case ICmpInst::ICMP_NE:
2991 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2992 case ICmpInst::ICMP_SGT:
2993 case ICmpInst::ICMP_SGE:
2994 return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
2995 Constant::getAllOnesValue(SRem->getType()));
2996 case ICmpInst::ICMP_SLT:
2997 case ICmpInst::ICMP_SLE:
2998 return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
2999 Constant::getNullValue(SRem->getType()));
3003 if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() &&
3004 BO0->hasOneUse() && BO1->hasOneUse() &&
3005 BO0->getOperand(1) == BO1->getOperand(1)) {
3006 switch (BO0->getOpcode()) {
3008 case Instruction::Add:
3009 case Instruction::Sub:
3010 case Instruction::Xor:
3011 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
3012 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3013 BO1->getOperand(0));
3014 // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b
3015 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
3016 if (CI->getValue().isSignBit()) {
3017 ICmpInst::Predicate Pred = I.isSigned()
3018 ? I.getUnsignedPredicate()
3019 : I.getSignedPredicate();
3020 return new ICmpInst(Pred, BO0->getOperand(0),
3021 BO1->getOperand(0));
3024 if (CI->isMaxValue(true)) {
3025 ICmpInst::Predicate Pred = I.isSigned()
3026 ? I.getUnsignedPredicate()
3027 : I.getSignedPredicate();
3028 Pred = I.getSwappedPredicate(Pred);
3029 return new ICmpInst(Pred, BO0->getOperand(0),
3030 BO1->getOperand(0));
3034 case Instruction::Mul:
3035 if (!I.isEquality())
3038 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
3039 // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
3040 // Mask = -1 >> count-trailing-zeros(Cst).
3041 if (!CI->isZero() && !CI->isOne()) {
3042 const APInt &AP = CI->getValue();
3043 ConstantInt *Mask = ConstantInt::get(I.getContext(),
3044 APInt::getLowBitsSet(AP.getBitWidth(),
3046 AP.countTrailingZeros()));
3047 Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask);
3048 Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask);
3049 return new ICmpInst(I.getPredicate(), And1, And2);
3053 case Instruction::UDiv:
3054 case Instruction::LShr:
3058 case Instruction::SDiv:
3059 case Instruction::AShr:
3060 if (!BO0->isExact() || !BO1->isExact())
3062 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3063 BO1->getOperand(0));
3064 case Instruction::Shl: {
3065 bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
3066 bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
3069 if (!NSW && I.isSigned())
3071 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
3072 BO1->getOperand(0));
3079 // Transform (A & ~B) == 0 --> (A & B) != 0
3080 // and (A & ~B) != 0 --> (A & B) == 0
3081 // if A is a power of 2.
3082 if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
3083 match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(A) && I.isEquality())
3084 return new ICmpInst(I.getInversePredicate(),
3085 Builder->CreateAnd(A, B),
3088 // ~x < ~y --> y < x
3089 // ~x < cst --> ~cst < x
3090 if (match(Op0, m_Not(m_Value(A)))) {
3091 if (match(Op1, m_Not(m_Value(B))))
3092 return new ICmpInst(I.getPredicate(), B, A);
3093 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
3094 return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A);
3097 // (a+b) <u a --> llvm.uadd.with.overflow.
3098 // (a+b) <u b --> llvm.uadd.with.overflow.
3099 if (I.getPredicate() == ICmpInst::ICMP_ULT &&
3100 match(Op0, m_Add(m_Value(A), m_Value(B))) &&
3101 (Op1 == A || Op1 == B))
3102 if (Instruction *R = ProcessUAddIdiom(I, Op0, *this))
3105 // a >u (a+b) --> llvm.uadd.with.overflow.
3106 // b >u (a+b) --> llvm.uadd.with.overflow.
3107 if (I.getPredicate() == ICmpInst::ICMP_UGT &&
3108 match(Op1, m_Add(m_Value(A), m_Value(B))) &&
3109 (Op0 == A || Op0 == B))
3110 if (Instruction *R = ProcessUAddIdiom(I, Op1, *this))
3113 // (zext a) * (zext b) --> llvm.umul.with.overflow.
3114 if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
3115 if (Instruction *R = ProcessUMulZExtIdiom(I, Op0, Op1, *this))
3118 if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) {
3119 if (Instruction *R = ProcessUMulZExtIdiom(I, Op1, Op0, *this))
3124 if (I.isEquality()) {
3125 Value *A, *B, *C, *D;
3127 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
3128 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
3129 Value *OtherVal = A == Op1 ? B : A;
3130 return new ICmpInst(I.getPredicate(), OtherVal,
3131 Constant::getNullValue(A->getType()));
3134 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
3135 // A^c1 == C^c2 --> A == C^(c1^c2)
3136 ConstantInt *C1, *C2;
3137 if (match(B, m_ConstantInt(C1)) &&
3138 match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) {
3139 Constant *NC = Builder->getInt(C1->getValue() ^ C2->getValue());
3140 Value *Xor = Builder->CreateXor(C, NC);
3141 return new ICmpInst(I.getPredicate(), A, Xor);
3144 // A^B == A^D -> B == D
3145 if (A == C) return new ICmpInst(I.getPredicate(), B, D);
3146 if (A == D) return new ICmpInst(I.getPredicate(), B, C);
3147 if (B == C) return new ICmpInst(I.getPredicate(), A, D);
3148 if (B == D) return new ICmpInst(I.getPredicate(), A, C);
3152 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
3153 (A == Op0 || B == Op0)) {
3154 // A == (A^B) -> B == 0
3155 Value *OtherVal = A == Op0 ? B : A;
3156 return new ICmpInst(I.getPredicate(), OtherVal,
3157 Constant::getNullValue(A->getType()));
3160 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
3161 if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
3162 match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
3163 Value *X = nullptr, *Y = nullptr, *Z = nullptr;
3166 X = B; Y = D; Z = A;
3167 } else if (A == D) {
3168 X = B; Y = C; Z = A;
3169 } else if (B == C) {
3170 X = A; Y = D; Z = B;
3171 } else if (B == D) {
3172 X = A; Y = C; Z = B;
3175 if (X) { // Build (X^Y) & Z
3176 Op1 = Builder->CreateXor(X, Y);
3177 Op1 = Builder->CreateAnd(Op1, Z);
3178 I.setOperand(0, Op1);
3179 I.setOperand(1, Constant::getNullValue(Op1->getType()));
3184 // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B)
3185 // and (B & (1<<X)-1) == (zext A) --> A == (trunc B)
3187 if ((Op0->hasOneUse() &&
3188 match(Op0, m_ZExt(m_Value(A))) &&
3189 match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) ||
3190 (Op1->hasOneUse() &&
3191 match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) &&
3192 match(Op1, m_ZExt(m_Value(A))))) {
3193 APInt Pow2 = Cst1->getValue() + 1;
3194 if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) &&
3195 Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth())
3196 return new ICmpInst(I.getPredicate(), A,
3197 Builder->CreateTrunc(B, A->getType()));
3200 // (A >> C) == (B >> C) --> (A^B) u< (1 << C)
3201 // For lshr and ashr pairs.
3202 if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3203 match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) ||
3204 (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) &&
3205 match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) {
3206 unsigned TypeBits = Cst1->getBitWidth();
3207 unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits);
3208 if (ShAmt < TypeBits && ShAmt != 0) {
3209 ICmpInst::Predicate Pred = I.getPredicate() == ICmpInst::ICMP_NE
3210 ? ICmpInst::ICMP_UGE
3211 : ICmpInst::ICMP_ULT;
3212 Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted");
3213 APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt);
3214 return new ICmpInst(Pred, Xor, Builder->getInt(CmpVal));
3218 // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
3219 // "icmp (and X, mask), cst"
3221 if (Op0->hasOneUse() &&
3222 match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A),
3223 m_ConstantInt(ShAmt))))) &&
3224 match(Op1, m_ConstantInt(Cst1)) &&
3225 // Only do this when A has multiple uses. This is most important to do
3226 // when it exposes other optimizations.
3228 unsigned ASize =cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
3230 if (ShAmt < ASize) {
3232 APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits());
3235 APInt CmpV = Cst1->getValue().zext(ASize);
3238 Value *Mask = Builder->CreateAnd(A, Builder->getInt(MaskV));
3239 return new ICmpInst(I.getPredicate(), Mask, Builder->getInt(CmpV));
3245 Value *X; ConstantInt *Cst;
3247 if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
3248 return FoldICmpAddOpCst(I, X, Cst, I.getPredicate());
3251 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
3252 return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate());
3254 return Changed ? &I : nullptr;
3257 /// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
3259 Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
3262 if (!isa<ConstantFP>(RHSC)) return nullptr;
3263 const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
3265 // Get the width of the mantissa. We don't want to hack on conversions that
3266 // might lose information from the integer, e.g. "i64 -> float"
3267 int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
3268 if (MantissaWidth == -1) return nullptr; // Unknown.
3270 // Check to see that the input is converted from an integer type that is small
3271 // enough that preserves all bits. TODO: check here for "known" sign bits.
3272 // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
3273 unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits();
3275 // If this is a uitofp instruction, we need an extra bit to hold the sign.
3276 bool LHSUnsigned = isa<UIToFPInst>(LHSI);
3280 // If the conversion would lose info, don't hack on this.
3281 if ((int)InputSize > MantissaWidth)
3284 // Otherwise, we can potentially simplify the comparison. We know that it
3285 // will always come through as an integer value and we know the constant is
3286 // not a NAN (it would have been previously simplified).
3287 assert(!RHS.isNaN() && "NaN comparison not already folded!");
3289 ICmpInst::Predicate Pred;
3290 switch (I.getPredicate()) {
3291 default: llvm_unreachable("Unexpected predicate!");
3292 case FCmpInst::FCMP_UEQ:
3293 case FCmpInst::FCMP_OEQ:
3294 Pred = ICmpInst::ICMP_EQ;
3296 case FCmpInst::FCMP_UGT:
3297 case FCmpInst::FCMP_OGT:
3298 Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
3300 case FCmpInst::FCMP_UGE:
3301 case FCmpInst::FCMP_OGE:
3302 Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
3304 case FCmpInst::FCMP_ULT:
3305 case FCmpInst::FCMP_OLT:
3306 Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
3308 case FCmpInst::FCMP_ULE:
3309 case FCmpInst::FCMP_OLE:
3310 Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
3312 case FCmpInst::FCMP_UNE:
3313 case FCmpInst::FCMP_ONE:
3314 Pred = ICmpInst::ICMP_NE;
3316 case FCmpInst::FCMP_ORD:
3317 return ReplaceInstUsesWith(I, Builder->getTrue());
3318 case FCmpInst::FCMP_UNO:
3319 return ReplaceInstUsesWith(I, Builder->getFalse());
3322 IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
3324 // Now we know that the APFloat is a normal number, zero or inf.
3326 // See if the FP constant is too large for the integer. For example,
3327 // comparing an i8 to 300.0.
3328 unsigned IntWidth = IntTy->getScalarSizeInBits();
3331 // If the RHS value is > SignedMax, fold the comparison. This handles +INF
3332 // and large values.
3333 APFloat SMax(RHS.getSemantics());
3334 SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
3335 APFloat::rmNearestTiesToEven);
3336 if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
3337 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
3338 Pred == ICmpInst::ICMP_SLE)
3339 return ReplaceInstUsesWith(I, Builder->getTrue());
3340 return ReplaceInstUsesWith(I, Builder->getFalse());
3343 // If the RHS value is > UnsignedMax, fold the comparison. This handles
3344 // +INF and large values.
3345 APFloat UMax(RHS.getSemantics());
3346 UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
3347 APFloat::rmNearestTiesToEven);
3348 if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
3349 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
3350 Pred == ICmpInst::ICMP_ULE)
3351 return ReplaceInstUsesWith(I, Builder->getTrue());
3352 return ReplaceInstUsesWith(I, Builder->getFalse());
3357 // See if the RHS value is < SignedMin.
3358 APFloat SMin(RHS.getSemantics());
3359 SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
3360 APFloat::rmNearestTiesToEven);
3361 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
3362 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
3363 Pred == ICmpInst::ICMP_SGE)
3364 return ReplaceInstUsesWith(I, Builder->getTrue());
3365 return ReplaceInstUsesWith(I, Builder->getFalse());
3368 // See if the RHS value is < UnsignedMin.
3369 APFloat SMin(RHS.getSemantics());
3370 SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
3371 APFloat::rmNearestTiesToEven);
3372 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
3373 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
3374 Pred == ICmpInst::ICMP_UGE)
3375 return ReplaceInstUsesWith(I, Builder->getTrue());
3376 return ReplaceInstUsesWith(I, Builder->getFalse());
3380 // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
3381 // [0, UMAX], but it may still be fractional. See if it is fractional by
3382 // casting the FP value to the integer value and back, checking for equality.
3383 // Don't do this for zero, because -0.0 is not fractional.
3384 Constant *RHSInt = LHSUnsigned
3385 ? ConstantExpr::getFPToUI(RHSC, IntTy)
3386 : ConstantExpr::getFPToSI(RHSC, IntTy);
3387 if (!RHS.isZero()) {
3388 bool Equal = LHSUnsigned
3389 ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
3390 : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
3392 // If we had a comparison against a fractional value, we have to adjust
3393 // the compare predicate and sometimes the value. RHSC is rounded towards
3394 // zero at this point.
3396 default: llvm_unreachable("Unexpected integer comparison!");
3397 case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
3398 return ReplaceInstUsesWith(I, Builder->getTrue());
3399 case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
3400 return ReplaceInstUsesWith(I, Builder->getFalse());
3401 case ICmpInst::ICMP_ULE:
3402 // (float)int <= 4.4 --> int <= 4
3403 // (float)int <= -4.4 --> false
3404 if (RHS.isNegative())
3405 return ReplaceInstUsesWith(I, Builder->getFalse());
3407 case ICmpInst::ICMP_SLE:
3408 // (float)int <= 4.4 --> int <= 4
3409 // (float)int <= -4.4 --> int < -4
3410 if (RHS.isNegative())
3411 Pred = ICmpInst::ICMP_SLT;
3413 case ICmpInst::ICMP_ULT:
3414 // (float)int < -4.4 --> false
3415 // (float)int < 4.4 --> int <= 4
3416 if (RHS.isNegative())
3417 return ReplaceInstUsesWith(I, Builder->getFalse());
3418 Pred = ICmpInst::ICMP_ULE;
3420 case ICmpInst::ICMP_SLT:
3421 // (float)int < -4.4 --> int < -4
3422 // (float)int < 4.4 --> int <= 4
3423 if (!RHS.isNegative())
3424 Pred = ICmpInst::ICMP_SLE;
3426 case ICmpInst::ICMP_UGT:
3427 // (float)int > 4.4 --> int > 4
3428 // (float)int > -4.4 --> true
3429 if (RHS.isNegative())
3430 return ReplaceInstUsesWith(I, Builder->getTrue());
3432 case ICmpInst::ICMP_SGT:
3433 // (float)int > 4.4 --> int > 4
3434 // (float)int > -4.4 --> int >= -4
3435 if (RHS.isNegative())
3436 Pred = ICmpInst::ICMP_SGE;
3438 case ICmpInst::ICMP_UGE:
3439 // (float)int >= -4.4 --> true
3440 // (float)int >= 4.4 --> int > 4
3441 if (RHS.isNegative())
3442 return ReplaceInstUsesWith(I, Builder->getTrue());
3443 Pred = ICmpInst::ICMP_UGT;
3445 case ICmpInst::ICMP_SGE:
3446 // (float)int >= -4.4 --> int >= -4
3447 // (float)int >= 4.4 --> int > 4
3448 if (!RHS.isNegative())
3449 Pred = ICmpInst::ICMP_SGT;
3455 // Lower this FP comparison into an appropriate integer version of the
3457 return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
3460 Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
3461 bool Changed = false;
3463 /// Orders the operands of the compare so that they are listed from most
3464 /// complex to least complex. This puts constants before unary operators,
3465 /// before binary operators.
3466 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
3471 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
3473 if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL))
3474 return ReplaceInstUsesWith(I, V);
3476 // Simplify 'fcmp pred X, X'
3478 switch (I.getPredicate()) {
3479 default: llvm_unreachable("Unknown predicate!");
3480 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
3481 case FCmpInst::FCMP_ULT: // True if unordered or less than
3482 case FCmpInst::FCMP_UGT: // True if unordered or greater than
3483 case FCmpInst::FCMP_UNE: // True if unordered or not equal
3484 // Canonicalize these to be 'fcmp uno %X, 0.0'.
3485 I.setPredicate(FCmpInst::FCMP_UNO);
3486 I.setOperand(1, Constant::getNullValue(Op0->getType()));
3489 case FCmpInst::FCMP_ORD: // True if ordered (no nans)
3490 case FCmpInst::FCMP_OEQ: // True if ordered and equal
3491 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
3492 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
3493 // Canonicalize these to be 'fcmp ord %X, 0.0'.
3494 I.setPredicate(FCmpInst::FCMP_ORD);
3495 I.setOperand(1, Constant::getNullValue(Op0->getType()));
3500 // Handle fcmp with constant RHS
3501 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
3502 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
3503 switch (LHSI->getOpcode()) {
3504 case Instruction::FPExt: {
3505 // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
3506 FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
3507 ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
3511 const fltSemantics *Sem;
3512 // FIXME: This shouldn't be here.
3513 if (LHSExt->getSrcTy()->isHalfTy())
3514 Sem = &APFloat::IEEEhalf;
3515 else if (LHSExt->getSrcTy()->isFloatTy())
3516 Sem = &APFloat::IEEEsingle;
3517 else if (LHSExt->getSrcTy()->isDoubleTy())
3518 Sem = &APFloat::IEEEdouble;
3519 else if (LHSExt->getSrcTy()->isFP128Ty())
3520 Sem = &APFloat::IEEEquad;
3521 else if (LHSExt->getSrcTy()->isX86_FP80Ty())
3522 Sem = &APFloat::x87DoubleExtended;
3523 else if (LHSExt->getSrcTy()->isPPC_FP128Ty())
3524 Sem = &APFloat::PPCDoubleDouble;
3529 APFloat F = RHSF->getValueAPF();
3530 F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
3532 // Avoid lossy conversions and denormals. Zero is a special case
3533 // that's OK to convert.
3537 ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
3538 APFloat::cmpLessThan) || Fabs.isZero()))
3540 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
3541 ConstantFP::get(RHSC->getContext(), F));
3544 case Instruction::PHI:
3545 // Only fold fcmp into the PHI if the phi and fcmp are in the same
3546 // block. If in the same block, we're encouraging jump threading. If
3547 // not, we are just pessimizing the code by making an i1 phi.
3548 if (LHSI->getParent() == I.getParent())
3549 if (Instruction *NV = FoldOpIntoPhi(I))
3552 case Instruction::SIToFP:
3553 case Instruction::UIToFP:
3554 if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC))
3557 case Instruction::FSub: {
3558 // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
3560 if (match(LHSI, m_FNeg(m_Value(Op))))
3561 return new FCmpInst(I.getSwappedPredicate(), Op,
3562 ConstantExpr::getFNeg(RHSC));
3565 case Instruction::Load:
3566 if (GetElementPtrInst *GEP =
3567 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
3568 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
3569 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
3570 !cast<LoadInst>(LHSI)->isVolatile())
3571 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
3575 case Instruction::Call: {
3576 CallInst *CI = cast<CallInst>(LHSI);
3578 // Various optimization for fabs compared with zero.
3579 if (RHSC->isNullValue() && CI->getCalledFunction() &&
3580 TLI->getLibFunc(CI->getCalledFunction()->getName(), Func) &&
3582 if (Func == LibFunc::fabs || Func == LibFunc::fabsf ||
3583 Func == LibFunc::fabsl) {
3584 switch (I.getPredicate()) {
3586 // fabs(x) < 0 --> false
3587 case FCmpInst::FCMP_OLT:
3588 return ReplaceInstUsesWith(I, Builder->getFalse());
3589 // fabs(x) > 0 --> x != 0
3590 case FCmpInst::FCMP_OGT:
3591 return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0),
3593 // fabs(x) <= 0 --> x == 0
3594 case FCmpInst::FCMP_OLE:
3595 return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0),
3597 // fabs(x) >= 0 --> !isnan(x)
3598 case FCmpInst::FCMP_OGE:
3599 return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0),
3601 // fabs(x) == 0 --> x == 0
3602 // fabs(x) != 0 --> x != 0
3603 case FCmpInst::FCMP_OEQ:
3604 case FCmpInst::FCMP_UEQ:
3605 case FCmpInst::FCMP_ONE:
3606 case FCmpInst::FCMP_UNE:
3607 return new FCmpInst(I.getPredicate(), CI->getArgOperand(0),
3616 // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
3618 if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
3619 return new FCmpInst(I.getSwappedPredicate(), X, Y);
3621 // fcmp (fpext x), (fpext y) -> fcmp x, y
3622 if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0))
3623 if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1))
3624 if (LHSExt->getSrcTy() == RHSExt->getSrcTy())
3625 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
3626 RHSExt->getOperand(0));
3628 return Changed ? &I : nullptr;