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/IntrinsicInst.h"
16 #include "llvm/Analysis/ConstantFolding.h"
17 #include "llvm/Analysis/InstructionSimplify.h"
18 #include "llvm/Analysis/MemoryBuiltins.h"
19 #include "llvm/Target/TargetData.h"
20 #include "llvm/Support/ConstantRange.h"
21 #include "llvm/Support/GetElementPtrTypeIterator.h"
22 #include "llvm/Support/PatternMatch.h"
24 using namespace PatternMatch;
26 static ConstantInt *getOne(Constant *C) {
27 return ConstantInt::get(cast<IntegerType>(C->getType()), 1);
30 /// AddOne - Add one to a ConstantInt
31 static Constant *AddOne(Constant *C) {
32 return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
34 /// SubOne - Subtract one from a ConstantInt
35 static Constant *SubOne(Constant *C) {
36 return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
39 static ConstantInt *ExtractElement(Constant *V, Constant *Idx) {
40 return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx));
43 static bool HasAddOverflow(ConstantInt *Result,
44 ConstantInt *In1, ConstantInt *In2,
47 return Result->getValue().ult(In1->getValue());
49 if (In2->isNegative())
50 return Result->getValue().sgt(In1->getValue());
51 return Result->getValue().slt(In1->getValue());
54 /// AddWithOverflow - Compute Result = In1+In2, returning true if the result
55 /// overflowed for this type.
56 static bool AddWithOverflow(Constant *&Result, Constant *In1,
57 Constant *In2, bool IsSigned = false) {
58 Result = ConstantExpr::getAdd(In1, In2);
60 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
61 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
62 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
63 if (HasAddOverflow(ExtractElement(Result, Idx),
64 ExtractElement(In1, Idx),
65 ExtractElement(In2, Idx),
72 return HasAddOverflow(cast<ConstantInt>(Result),
73 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
77 static bool HasSubOverflow(ConstantInt *Result,
78 ConstantInt *In1, ConstantInt *In2,
81 return Result->getValue().ugt(In1->getValue());
83 if (In2->isNegative())
84 return Result->getValue().slt(In1->getValue());
86 return Result->getValue().sgt(In1->getValue());
89 /// SubWithOverflow - Compute Result = In1-In2, returning true if the result
90 /// overflowed for this type.
91 static bool SubWithOverflow(Constant *&Result, Constant *In1,
92 Constant *In2, bool IsSigned = false) {
93 Result = ConstantExpr::getSub(In1, In2);
95 if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) {
96 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
97 Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i);
98 if (HasSubOverflow(ExtractElement(Result, Idx),
99 ExtractElement(In1, Idx),
100 ExtractElement(In2, Idx),
107 return HasSubOverflow(cast<ConstantInt>(Result),
108 cast<ConstantInt>(In1), cast<ConstantInt>(In2),
112 /// isSignBitCheck - Given an exploded icmp instruction, return true if the
113 /// comparison only checks the sign bit. If it only checks the sign bit, set
114 /// TrueIfSigned if the result of the comparison is true when the input value is
116 static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS,
117 bool &TrueIfSigned) {
119 case ICmpInst::ICMP_SLT: // True if LHS s< 0
121 return RHS->isZero();
122 case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1
124 return RHS->isAllOnesValue();
125 case ICmpInst::ICMP_SGT: // True if LHS s> -1
126 TrueIfSigned = false;
127 return RHS->isAllOnesValue();
128 case ICmpInst::ICMP_UGT:
129 // True if LHS u> RHS and RHS == high-bit-mask - 1
131 return RHS->isMaxValue(true);
132 case ICmpInst::ICMP_UGE:
133 // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc)
135 return RHS->getValue().isSignBit();
141 // isHighOnes - Return true if the constant is of the form 1+0+.
142 // This is the same as lowones(~X).
143 static bool isHighOnes(const ConstantInt *CI) {
144 return (~CI->getValue() + 1).isPowerOf2();
147 /// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a
148 /// set of known zero and one bits, compute the maximum and minimum values that
149 /// could have the specified known zero and known one bits, returning them in
151 static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero,
152 const APInt& KnownOne,
153 APInt& Min, APInt& Max) {
154 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
155 KnownZero.getBitWidth() == Min.getBitWidth() &&
156 KnownZero.getBitWidth() == Max.getBitWidth() &&
157 "KnownZero, KnownOne and Min, Max must have equal bitwidth.");
158 APInt UnknownBits = ~(KnownZero|KnownOne);
160 // The minimum value is when all unknown bits are zeros, EXCEPT for the sign
161 // bit if it is unknown.
163 Max = KnownOne|UnknownBits;
165 if (UnknownBits.isNegative()) { // Sign bit is unknown
166 Min.setBit(Min.getBitWidth()-1);
167 Max.clearBit(Max.getBitWidth()-1);
171 // ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and
172 // a set of known zero and one bits, compute the maximum and minimum values that
173 // could have the specified known zero and known one bits, returning them in
175 static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero,
176 const APInt &KnownOne,
177 APInt &Min, APInt &Max) {
178 assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() &&
179 KnownZero.getBitWidth() == Min.getBitWidth() &&
180 KnownZero.getBitWidth() == Max.getBitWidth() &&
181 "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth.");
182 APInt UnknownBits = ~(KnownZero|KnownOne);
184 // The minimum value is when the unknown bits are all zeros.
186 // The maximum value is when the unknown bits are all ones.
187 Max = KnownOne|UnknownBits;
192 /// FoldCmpLoadFromIndexedGlobal - Called we see this pattern:
193 /// cmp pred (load (gep GV, ...)), cmpcst
194 /// where GV is a global variable with a constant initializer. Try to simplify
195 /// this into some simple computation that does not need the load. For example
196 /// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3".
198 /// If AndCst is non-null, then the loaded value is masked with that constant
199 /// before doing the comparison. This handles cases like "A[i]&4 == 0".
200 Instruction *InstCombiner::
201 FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV,
202 CmpInst &ICI, ConstantInt *AndCst) {
203 // We need TD information to know the pointer size unless this is inbounds.
204 if (!GEP->isInBounds() && TD == 0) return 0;
206 Constant *Init = GV->getInitializer();
207 if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init))
210 uint64_t ArrayElementCount = Init->getType()->getArrayNumElements();
211 if (ArrayElementCount > 1024) return 0; // Don't blow up on huge arrays.
213 // There are many forms of this optimization we can handle, for now, just do
214 // the simple index into a single-dimensional array.
216 // Require: GEP GV, 0, i {{, constant indices}}
217 if (GEP->getNumOperands() < 3 ||
218 !isa<ConstantInt>(GEP->getOperand(1)) ||
219 !cast<ConstantInt>(GEP->getOperand(1))->isZero() ||
220 isa<Constant>(GEP->getOperand(2)))
223 // Check that indices after the variable are constants and in-range for the
224 // type they index. Collect the indices. This is typically for arrays of
226 SmallVector<unsigned, 4> LaterIndices;
228 Type *EltTy = Init->getType()->getArrayElementType();
229 for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) {
230 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
231 if (Idx == 0) return 0; // Variable index.
233 uint64_t IdxVal = Idx->getZExtValue();
234 if ((unsigned)IdxVal != IdxVal) return 0; // Too large array index.
236 if (StructType *STy = dyn_cast<StructType>(EltTy))
237 EltTy = STy->getElementType(IdxVal);
238 else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) {
239 if (IdxVal >= ATy->getNumElements()) return 0;
240 EltTy = ATy->getElementType();
242 return 0; // Unknown type.
245 LaterIndices.push_back(IdxVal);
248 enum { Overdefined = -3, Undefined = -2 };
250 // Variables for our state machines.
252 // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form
253 // "i == 47 | i == 87", where 47 is the first index the condition is true for,
254 // and 87 is the second (and last) index. FirstTrueElement is -2 when
255 // undefined, otherwise set to the first true element. SecondTrueElement is
256 // -2 when undefined, -3 when overdefined and >= 0 when that index is true.
257 int FirstTrueElement = Undefined, SecondTrueElement = Undefined;
259 // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the
260 // form "i != 47 & i != 87". Same state transitions as for true elements.
261 int FirstFalseElement = Undefined, SecondFalseElement = Undefined;
263 /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these
264 /// define a state machine that triggers for ranges of values that the index
265 /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'.
266 /// This is -2 when undefined, -3 when overdefined, and otherwise the last
267 /// index in the range (inclusive). We use -2 for undefined here because we
268 /// use relative comparisons and don't want 0-1 to match -1.
269 int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined;
271 // MagicBitvector - This is a magic bitvector where we set a bit if the
272 // comparison is true for element 'i'. If there are 64 elements or less in
273 // the array, this will fully represent all the comparison results.
274 uint64_t MagicBitvector = 0;
277 // Scan the array and see if one of our patterns matches.
278 Constant *CompareRHS = cast<Constant>(ICI.getOperand(1));
279 for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) {
280 Constant *Elt = Init->getAggregateElement(i);
281 if (Elt == 0) return 0;
283 // If this is indexing an array of structures, get the structure element.
284 if (!LaterIndices.empty())
285 Elt = ConstantExpr::getExtractValue(Elt, LaterIndices);
287 // If the element is masked, handle it.
288 if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst);
290 // Find out if the comparison would be true or false for the i'th element.
291 Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt,
292 CompareRHS, TD, TLI);
293 // If the result is undef for this element, ignore it.
294 if (isa<UndefValue>(C)) {
295 // Extend range state machines to cover this element in case there is an
296 // undef in the middle of the range.
297 if (TrueRangeEnd == (int)i-1)
299 if (FalseRangeEnd == (int)i-1)
304 // If we can't compute the result for any of the elements, we have to give
305 // up evaluating the entire conditional.
306 if (!isa<ConstantInt>(C)) return 0;
308 // Otherwise, we know if the comparison is true or false for this element,
309 // update our state machines.
310 bool IsTrueForElt = !cast<ConstantInt>(C)->isZero();
312 // State machine for single/double/range index comparison.
314 // Update the TrueElement state machine.
315 if (FirstTrueElement == Undefined)
316 FirstTrueElement = TrueRangeEnd = i; // First true element.
318 // Update double-compare state machine.
319 if (SecondTrueElement == Undefined)
320 SecondTrueElement = i;
322 SecondTrueElement = Overdefined;
324 // Update range state machine.
325 if (TrueRangeEnd == (int)i-1)
328 TrueRangeEnd = Overdefined;
331 // Update the FalseElement state machine.
332 if (FirstFalseElement == Undefined)
333 FirstFalseElement = FalseRangeEnd = i; // First false element.
335 // Update double-compare state machine.
336 if (SecondFalseElement == Undefined)
337 SecondFalseElement = i;
339 SecondFalseElement = Overdefined;
341 // Update range state machine.
342 if (FalseRangeEnd == (int)i-1)
345 FalseRangeEnd = Overdefined;
350 // If this element is in range, update our magic bitvector.
351 if (i < 64 && IsTrueForElt)
352 MagicBitvector |= 1ULL << i;
354 // If all of our states become overdefined, bail out early. Since the
355 // predicate is expensive, only check it every 8 elements. This is only
356 // really useful for really huge arrays.
357 if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined &&
358 SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined &&
359 FalseRangeEnd == Overdefined)
363 // Now that we've scanned the entire array, emit our new comparison(s). We
364 // order the state machines in complexity of the generated code.
365 Value *Idx = GEP->getOperand(2);
367 // If the index is larger than the pointer size of the target, truncate the
368 // index down like the GEP would do implicitly. We don't have to do this for
369 // an inbounds GEP because the index can't be out of range.
370 if (!GEP->isInBounds() &&
371 Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits())
372 Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext()));
374 // If the comparison is only true for one or two elements, emit direct
376 if (SecondTrueElement != Overdefined) {
377 // None true -> false.
378 if (FirstTrueElement == Undefined)
379 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(GEP->getContext()));
381 Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement);
383 // True for one element -> 'i == 47'.
384 if (SecondTrueElement == Undefined)
385 return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx);
387 // True for two elements -> 'i == 47 | i == 72'.
388 Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx);
389 Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement);
390 Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx);
391 return BinaryOperator::CreateOr(C1, C2);
394 // If the comparison is only false for one or two elements, emit direct
396 if (SecondFalseElement != Overdefined) {
397 // None false -> true.
398 if (FirstFalseElement == Undefined)
399 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(GEP->getContext()));
401 Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement);
403 // False for one element -> 'i != 47'.
404 if (SecondFalseElement == Undefined)
405 return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx);
407 // False for two elements -> 'i != 47 & i != 72'.
408 Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx);
409 Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement);
410 Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx);
411 return BinaryOperator::CreateAnd(C1, C2);
414 // If the comparison can be replaced with a range comparison for the elements
415 // where it is true, emit the range check.
416 if (TrueRangeEnd != Overdefined) {
417 assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare");
419 // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1).
420 if (FirstTrueElement) {
421 Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement);
422 Idx = Builder->CreateAdd(Idx, Offs);
425 Value *End = ConstantInt::get(Idx->getType(),
426 TrueRangeEnd-FirstTrueElement+1);
427 return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End);
430 // False range check.
431 if (FalseRangeEnd != Overdefined) {
432 assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare");
433 // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse).
434 if (FirstFalseElement) {
435 Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement);
436 Idx = Builder->CreateAdd(Idx, Offs);
439 Value *End = ConstantInt::get(Idx->getType(),
440 FalseRangeEnd-FirstFalseElement);
441 return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End);
445 // If a 32-bit or 64-bit magic bitvector captures the entire comparison state
446 // of this load, replace it with computation that does:
447 // ((magic_cst >> i) & 1) != 0
448 if (ArrayElementCount <= 32 ||
449 (TD && ArrayElementCount <= 64 && TD->isLegalInteger(64))) {
451 if (ArrayElementCount <= 32)
452 Ty = Type::getInt32Ty(Init->getContext());
454 Ty = Type::getInt64Ty(Init->getContext());
455 Value *V = Builder->CreateIntCast(Idx, Ty, false);
456 V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V);
457 V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V);
458 return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0));
465 /// EvaluateGEPOffsetExpression - Return a value that can be used to compare
466 /// the *offset* implied by a GEP to zero. For example, if we have &A[i], we
467 /// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can
468 /// be complex, and scales are involved. The above expression would also be
469 /// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32).
470 /// This later form is less amenable to optimization though, and we are allowed
471 /// to generate the first by knowing that pointer arithmetic doesn't overflow.
473 /// If we can't emit an optimized form for this expression, this returns null.
475 static Value *EvaluateGEPOffsetExpression(User *GEP, InstCombiner &IC) {
476 TargetData &TD = *IC.getTargetData();
477 gep_type_iterator GTI = gep_type_begin(GEP);
479 // Check to see if this gep only has a single variable index. If so, and if
480 // any constant indices are a multiple of its scale, then we can compute this
481 // in terms of the scale of the variable index. For example, if the GEP
482 // implies an offset of "12 + i*4", then we can codegen this as "3 + i",
483 // because the expression will cross zero at the same point.
484 unsigned i, e = GEP->getNumOperands();
486 for (i = 1; i != e; ++i, ++GTI) {
487 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
488 // Compute the aggregate offset of constant indices.
489 if (CI->isZero()) continue;
491 // Handle a struct index, which adds its field offset to the pointer.
492 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
493 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
495 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
496 Offset += Size*CI->getSExtValue();
499 // Found our variable index.
504 // If there are no variable indices, we must have a constant offset, just
505 // evaluate it the general way.
506 if (i == e) return 0;
508 Value *VariableIdx = GEP->getOperand(i);
509 // Determine the scale factor of the variable element. For example, this is
510 // 4 if the variable index is into an array of i32.
511 uint64_t VariableScale = TD.getTypeAllocSize(GTI.getIndexedType());
513 // Verify that there are no other variable indices. If so, emit the hard way.
514 for (++i, ++GTI; i != e; ++i, ++GTI) {
515 ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i));
518 // Compute the aggregate offset of constant indices.
519 if (CI->isZero()) continue;
521 // Handle a struct index, which adds its field offset to the pointer.
522 if (StructType *STy = dyn_cast<StructType>(*GTI)) {
523 Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue());
525 uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
526 Offset += Size*CI->getSExtValue();
530 // Okay, we know we have a single variable index, which must be a
531 // pointer/array/vector index. If there is no offset, life is simple, return
533 unsigned IntPtrWidth = TD.getPointerSizeInBits();
535 // Cast to intptrty in case a truncation occurs. If an extension is needed,
536 // we don't need to bother extending: the extension won't affect where the
537 // computation crosses zero.
538 if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) {
539 Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
540 VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy);
545 // Otherwise, there is an index. The computation we will do will be modulo
546 // the pointer size, so get it.
547 uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth);
549 Offset &= PtrSizeMask;
550 VariableScale &= PtrSizeMask;
552 // To do this transformation, any constant index must be a multiple of the
553 // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i",
554 // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a
555 // multiple of the variable scale.
556 int64_t NewOffs = Offset / (int64_t)VariableScale;
557 if (Offset != NewOffs*(int64_t)VariableScale)
560 // Okay, we can do this evaluation. Start by converting the index to intptr.
561 Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext());
562 if (VariableIdx->getType() != IntPtrTy)
563 VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy,
565 Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs);
566 return IC.Builder->CreateAdd(VariableIdx, OffsetVal, "offset");
569 /// FoldGEPICmp - Fold comparisons between a GEP instruction and something
570 /// else. At this point we know that the GEP is on the LHS of the comparison.
571 Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
572 ICmpInst::Predicate Cond,
574 // Don't transform signed compares of GEPs into index compares. Even if the
575 // GEP is inbounds, the final add of the base pointer can have signed overflow
576 // and would change the result of the icmp.
577 // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be
578 // the maximum signed value for the pointer type.
579 if (ICmpInst::isSigned(Cond))
582 // Look through bitcasts.
583 if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS))
584 RHS = BCI->getOperand(0);
586 Value *PtrBase = GEPLHS->getOperand(0);
587 if (TD && PtrBase == RHS && GEPLHS->isInBounds()) {
588 // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0).
589 // This transformation (ignoring the base and scales) is valid because we
590 // know pointers can't overflow since the gep is inbounds. See if we can
591 // output an optimized form.
592 Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, *this);
594 // If not, synthesize the offset the hard way.
596 Offset = EmitGEPOffset(GEPLHS);
597 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset,
598 Constant::getNullValue(Offset->getType()));
599 } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
600 // If the base pointers are different, but the indices are the same, just
601 // compare the base pointer.
602 if (PtrBase != GEPRHS->getOperand(0)) {
603 bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands();
604 IndicesTheSame &= GEPLHS->getOperand(0)->getType() ==
605 GEPRHS->getOperand(0)->getType();
607 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
608 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
609 IndicesTheSame = false;
613 // If all indices are the same, just compare the base pointers.
615 return new ICmpInst(ICmpInst::getSignedPredicate(Cond),
616 GEPLHS->getOperand(0), GEPRHS->getOperand(0));
618 // If we're comparing GEPs with two base pointers that only differ in type
619 // and both GEPs have only constant indices or just one use, then fold
620 // the compare with the adjusted indices.
621 if (TD && GEPLHS->isInBounds() && GEPRHS->isInBounds() &&
622 (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) &&
623 (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) &&
624 PtrBase->stripPointerCasts() ==
625 GEPRHS->getOperand(0)->stripPointerCasts()) {
626 Value *Cmp = Builder->CreateICmp(ICmpInst::getSignedPredicate(Cond),
627 EmitGEPOffset(GEPLHS),
628 EmitGEPOffset(GEPRHS));
629 return ReplaceInstUsesWith(I, Cmp);
632 // Otherwise, the base pointers are different and the indices are
633 // different, bail out.
637 // If one of the GEPs has all zero indices, recurse.
638 bool AllZeros = true;
639 for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i)
640 if (!isa<Constant>(GEPLHS->getOperand(i)) ||
641 !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) {
646 return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0),
647 ICmpInst::getSwappedPredicate(Cond), I);
649 // If the other GEP has all zero indices, recurse.
651 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
652 if (!isa<Constant>(GEPRHS->getOperand(i)) ||
653 !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) {
658 return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I);
660 bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds();
661 if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) {
662 // If the GEPs only differ by one index, compare it.
663 unsigned NumDifferences = 0; // Keep track of # differences.
664 unsigned DiffOperand = 0; // The operand that differs.
665 for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i)
666 if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) {
667 if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() !=
668 GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) {
669 // Irreconcilable differences.
673 if (NumDifferences++) break;
678 if (NumDifferences == 0) // SAME GEP?
679 return ReplaceInstUsesWith(I, // No comparison is needed here.
680 ConstantInt::get(Type::getInt1Ty(I.getContext()),
681 ICmpInst::isTrueWhenEqual(Cond)));
683 else if (NumDifferences == 1 && GEPsInBounds) {
684 Value *LHSV = GEPLHS->getOperand(DiffOperand);
685 Value *RHSV = GEPRHS->getOperand(DiffOperand);
686 // Make sure we do a signed comparison here.
687 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV);
691 // Only lower this if the icmp is the only user of the GEP or if we expect
692 // the result to fold to a constant!
695 (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) &&
696 (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) {
697 // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2)
698 Value *L = EmitGEPOffset(GEPLHS);
699 Value *R = EmitGEPOffset(GEPRHS);
700 return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R);
706 /// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X".
707 Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI,
708 Value *X, ConstantInt *CI,
709 ICmpInst::Predicate Pred,
711 // If we have X+0, exit early (simplifying logic below) and let it get folded
712 // elsewhere. icmp X+0, X -> icmp X, X
714 bool isTrue = ICmpInst::isTrueWhenEqual(Pred);
715 return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue));
718 // (X+4) == X -> false.
719 if (Pred == ICmpInst::ICMP_EQ)
720 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext()));
722 // (X+4) != X -> true.
723 if (Pred == ICmpInst::ICMP_NE)
724 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext()));
726 // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0,
727 // so the values can never be equal. Similarly for all other "or equals"
730 // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255
731 // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253
732 // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0
733 if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
735 ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI);
736 return new ICmpInst(ICmpInst::ICMP_UGT, X, R);
739 // (X+1) >u X --> X <u (0-1) --> X != 255
740 // (X+2) >u X --> X <u (0-2) --> X <u 254
741 // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0
742 if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
743 return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI));
745 unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits();
746 ConstantInt *SMax = ConstantInt::get(X->getContext(),
747 APInt::getSignedMaxValue(BitWidth));
749 // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127
750 // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125
751 // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0
752 // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1
753 // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126
754 // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127
755 if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
756 return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI));
758 // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127
759 // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126
760 // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1
761 // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2
762 // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126
763 // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128
765 assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE);
766 Constant *C = ConstantInt::get(X->getContext(), CI->getValue()-1);
767 return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C));
770 /// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS
771 /// and CmpRHS are both known to be integer constants.
772 Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI,
773 ConstantInt *DivRHS) {
774 ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1));
775 const APInt &CmpRHSV = CmpRHS->getValue();
777 // FIXME: If the operand types don't match the type of the divide
778 // then don't attempt this transform. The code below doesn't have the
779 // logic to deal with a signed divide and an unsigned compare (and
780 // vice versa). This is because (x /s C1) <s C2 produces different
781 // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even
782 // (x /u C1) <u C2. Simply casting the operands and result won't
783 // work. :( The if statement below tests that condition and bails
785 bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv;
786 if (!ICI.isEquality() && DivIsSigned != ICI.isSigned())
788 if (DivRHS->isZero())
789 return 0; // The ProdOV computation fails on divide by zero.
790 if (DivIsSigned && DivRHS->isAllOnesValue())
791 return 0; // The overflow computation also screws up here
792 if (DivRHS->isOne()) {
793 // This eliminates some funny cases with INT_MIN.
794 ICI.setOperand(0, DivI->getOperand(0)); // X/1 == X.
798 // Compute Prod = CI * DivRHS. We are essentially solving an equation
799 // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and
800 // C2 (CI). By solving for X we can turn this into a range check
801 // instead of computing a divide.
802 Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS);
804 // Determine if the product overflows by seeing if the product is
805 // not equal to the divide. Make sure we do the same kind of divide
806 // as in the LHS instruction that we're folding.
807 bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) :
808 ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS;
810 // Get the ICmp opcode
811 ICmpInst::Predicate Pred = ICI.getPredicate();
813 /// If the division is known to be exact, then there is no remainder from the
814 /// divide, so the covered range size is unit, otherwise it is the divisor.
815 ConstantInt *RangeSize = DivI->isExact() ? getOne(Prod) : DivRHS;
817 // Figure out the interval that is being checked. For example, a comparison
818 // like "X /u 5 == 0" is really checking that X is in the interval [0, 5).
819 // Compute this interval based on the constants involved and the signedness of
820 // the compare/divide. This computes a half-open interval, keeping track of
821 // whether either value in the interval overflows. After analysis each
822 // overflow variable is set to 0 if it's corresponding bound variable is valid
823 // -1 if overflowed off the bottom end, or +1 if overflowed off the top end.
824 int LoOverflow = 0, HiOverflow = 0;
825 Constant *LoBound = 0, *HiBound = 0;
827 if (!DivIsSigned) { // udiv
828 // e.g. X/5 op 3 --> [15, 20)
830 HiOverflow = LoOverflow = ProdOV;
832 // If this is not an exact divide, then many values in the range collapse
833 // to the same result value.
834 HiOverflow = AddWithOverflow(HiBound, LoBound, RangeSize, false);
837 } else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0.
838 if (CmpRHSV == 0) { // (X / pos) op 0
839 // Can't overflow. e.g. X/2 op 0 --> [-1, 2)
840 LoBound = ConstantExpr::getNeg(SubOne(RangeSize));
842 } else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos
843 LoBound = Prod; // e.g. X/5 op 3 --> [15, 20)
844 HiOverflow = LoOverflow = ProdOV;
846 HiOverflow = AddWithOverflow(HiBound, Prod, RangeSize, true);
847 } else { // (X / pos) op neg
848 // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14)
849 HiBound = AddOne(Prod);
850 LoOverflow = HiOverflow = ProdOV ? -1 : 0;
852 ConstantInt *DivNeg =cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
853 LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0;
856 } else if (DivRHS->isNegative()) { // Divisor is < 0.
858 RangeSize = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
859 if (CmpRHSV == 0) { // (X / neg) op 0
860 // e.g. X/-5 op 0 --> [-4, 5)
861 LoBound = AddOne(RangeSize);
862 HiBound = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize));
863 if (HiBound == DivRHS) { // -INTMIN = INTMIN
864 HiOverflow = 1; // [INTMIN+1, overflow)
865 HiBound = 0; // e.g. X/INTMIN = 0 --> X > INTMIN
867 } else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos
868 // e.g. X/-5 op 3 --> [-19, -14)
869 HiBound = AddOne(Prod);
870 HiOverflow = LoOverflow = ProdOV ? -1 : 0;
872 LoOverflow = AddWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0;
873 } else { // (X / neg) op neg
874 LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20)
875 LoOverflow = HiOverflow = ProdOV;
877 HiOverflow = SubWithOverflow(HiBound, Prod, RangeSize, true);
880 // Dividing by a negative swaps the condition. LT <-> GT
881 Pred = ICmpInst::getSwappedPredicate(Pred);
884 Value *X = DivI->getOperand(0);
886 default: llvm_unreachable("Unhandled icmp opcode!");
887 case ICmpInst::ICMP_EQ:
888 if (LoOverflow && HiOverflow)
889 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext()));
891 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
892 ICmpInst::ICMP_UGE, X, LoBound);
894 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
895 ICmpInst::ICMP_ULT, X, HiBound);
896 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound,
898 case ICmpInst::ICMP_NE:
899 if (LoOverflow && HiOverflow)
900 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext()));
902 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT :
903 ICmpInst::ICMP_ULT, X, LoBound);
905 return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE :
906 ICmpInst::ICMP_UGE, X, HiBound);
907 return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound,
908 DivIsSigned, false));
909 case ICmpInst::ICMP_ULT:
910 case ICmpInst::ICMP_SLT:
911 if (LoOverflow == +1) // Low bound is greater than input range.
912 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext()));
913 if (LoOverflow == -1) // Low bound is less than input range.
914 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext()));
915 return new ICmpInst(Pred, X, LoBound);
916 case ICmpInst::ICMP_UGT:
917 case ICmpInst::ICMP_SGT:
918 if (HiOverflow == +1) // High bound greater than input range.
919 return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext()));
920 if (HiOverflow == -1) // High bound less than input range.
921 return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext()));
922 if (Pred == ICmpInst::ICMP_UGT)
923 return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound);
924 return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound);
928 /// FoldICmpShrCst - Handle "icmp(([al]shr X, cst1), cst2)".
929 Instruction *InstCombiner::FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *Shr,
930 ConstantInt *ShAmt) {
931 const APInt &CmpRHSV = cast<ConstantInt>(ICI.getOperand(1))->getValue();
933 // Check that the shift amount is in range. If not, don't perform
934 // undefined shifts. When the shift is visited it will be
936 uint32_t TypeBits = CmpRHSV.getBitWidth();
937 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
938 if (ShAmtVal >= TypeBits || ShAmtVal == 0)
941 if (!ICI.isEquality()) {
942 // If we have an unsigned comparison and an ashr, we can't simplify this.
943 // Similarly for signed comparisons with lshr.
944 if (ICI.isSigned() != (Shr->getOpcode() == Instruction::AShr))
947 // Otherwise, all lshr and most exact ashr's are equivalent to a udiv/sdiv
948 // by a power of 2. Since we already have logic to simplify these,
949 // transform to div and then simplify the resultant comparison.
950 if (Shr->getOpcode() == Instruction::AShr &&
951 (!Shr->isExact() || ShAmtVal == TypeBits - 1))
954 // Revisit the shift (to delete it).
958 ConstantInt::get(Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal));
961 Shr->getOpcode() == Instruction::AShr ?
962 Builder->CreateSDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()) :
963 Builder->CreateUDiv(Shr->getOperand(0), DivCst, "", Shr->isExact());
965 ICI.setOperand(0, Tmp);
967 // If the builder folded the binop, just return it.
968 BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp);
972 // Otherwise, fold this div/compare.
973 assert(TheDiv->getOpcode() == Instruction::SDiv ||
974 TheDiv->getOpcode() == Instruction::UDiv);
976 Instruction *Res = FoldICmpDivCst(ICI, TheDiv, cast<ConstantInt>(DivCst));
977 assert(Res && "This div/cst should have folded!");
982 // If we are comparing against bits always shifted out, the
983 // comparison cannot succeed.
984 APInt Comp = CmpRHSV << ShAmtVal;
985 ConstantInt *ShiftedCmpRHS = ConstantInt::get(ICI.getContext(), Comp);
986 if (Shr->getOpcode() == Instruction::LShr)
987 Comp = Comp.lshr(ShAmtVal);
989 Comp = Comp.ashr(ShAmtVal);
991 if (Comp != CmpRHSV) { // Comparing against a bit that we know is zero.
992 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
993 Constant *Cst = ConstantInt::get(Type::getInt1Ty(ICI.getContext()),
995 return ReplaceInstUsesWith(ICI, Cst);
998 // Otherwise, check to see if the bits shifted out are known to be zero.
999 // If so, we can compare against the unshifted value:
1000 // (X & 4) >> 1 == 2 --> (X & 4) == 4.
1001 if (Shr->hasOneUse() && Shr->isExact())
1002 return new ICmpInst(ICI.getPredicate(), Shr->getOperand(0), ShiftedCmpRHS);
1004 if (Shr->hasOneUse()) {
1005 // Otherwise strength reduce the shift into an and.
1006 APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal));
1007 Constant *Mask = ConstantInt::get(ICI.getContext(), Val);
1009 Value *And = Builder->CreateAnd(Shr->getOperand(0),
1010 Mask, Shr->getName()+".mask");
1011 return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS);
1017 /// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)".
1019 Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI,
1022 const APInt &RHSV = RHS->getValue();
1024 switch (LHSI->getOpcode()) {
1025 case Instruction::Trunc:
1026 if (ICI.isEquality() && LHSI->hasOneUse()) {
1027 // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
1028 // of the high bits truncated out of x are known.
1029 unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
1030 SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits();
1031 APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
1032 ComputeMaskedBits(LHSI->getOperand(0), KnownZero, KnownOne);
1034 // If all the high bits are known, we can do this xform.
1035 if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) {
1036 // Pull in the high bits from known-ones set.
1037 APInt NewRHS = RHS->getValue().zext(SrcBits);
1038 NewRHS |= KnownOne & APInt::getHighBitsSet(SrcBits, SrcBits-DstBits);
1039 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
1040 ConstantInt::get(ICI.getContext(), NewRHS));
1045 case Instruction::Xor: // (icmp pred (xor X, XorCST), CI)
1046 if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
1047 // If this is a comparison that tests the signbit (X < 0) or (x > -1),
1049 if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) ||
1050 (ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) {
1051 Value *CompareVal = LHSI->getOperand(0);
1053 // If the sign bit of the XorCST is not set, there is no change to
1054 // the operation, just stop using the Xor.
1055 if (!XorCST->isNegative()) {
1056 ICI.setOperand(0, CompareVal);
1061 // Was the old condition true if the operand is positive?
1062 bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT;
1064 // If so, the new one isn't.
1065 isTrueIfPositive ^= true;
1067 if (isTrueIfPositive)
1068 return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal,
1071 return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal,
1075 if (LHSI->hasOneUse()) {
1076 // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit))
1077 if (!ICI.isEquality() && XorCST->getValue().isSignBit()) {
1078 const APInt &SignBit = XorCST->getValue();
1079 ICmpInst::Predicate Pred = ICI.isSigned()
1080 ? ICI.getUnsignedPredicate()
1081 : ICI.getSignedPredicate();
1082 return new ICmpInst(Pred, LHSI->getOperand(0),
1083 ConstantInt::get(ICI.getContext(),
1087 // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A)
1088 if (!ICI.isEquality() && XorCST->isMaxValue(true)) {
1089 const APInt &NotSignBit = XorCST->getValue();
1090 ICmpInst::Predicate Pred = ICI.isSigned()
1091 ? ICI.getUnsignedPredicate()
1092 : ICI.getSignedPredicate();
1093 Pred = ICI.getSwappedPredicate(Pred);
1094 return new ICmpInst(Pred, LHSI->getOperand(0),
1095 ConstantInt::get(ICI.getContext(),
1096 RHSV ^ NotSignBit));
1101 case Instruction::And: // (icmp pred (and X, AndCST), RHS)
1102 if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
1103 LHSI->getOperand(0)->hasOneUse()) {
1104 ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));
1106 // If the LHS is an AND of a truncating cast, we can widen the
1107 // and/compare to be the input width without changing the value
1108 // produced, eliminating a cast.
1109 if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) {
1110 // We can do this transformation if either the AND constant does not
1111 // have its sign bit set or if it is an equality comparison.
1112 // Extending a relational comparison when we're checking the sign
1113 // bit would not work.
1114 if (ICI.isEquality() ||
1115 (!AndCST->isNegative() && RHSV.isNonNegative())) {
1117 Builder->CreateAnd(Cast->getOperand(0),
1118 ConstantExpr::getZExt(AndCST, Cast->getSrcTy()));
1119 NewAnd->takeName(LHSI);
1120 return new ICmpInst(ICI.getPredicate(), NewAnd,
1121 ConstantExpr::getZExt(RHS, Cast->getSrcTy()));
1125 // If the LHS is an AND of a zext, and we have an equality compare, we can
1126 // shrink the and/compare to the smaller type, eliminating the cast.
1127 if (ZExtInst *Cast = dyn_cast<ZExtInst>(LHSI->getOperand(0))) {
1128 IntegerType *Ty = cast<IntegerType>(Cast->getSrcTy());
1129 // Make sure we don't compare the upper bits, SimplifyDemandedBits
1130 // should fold the icmp to true/false in that case.
1131 if (ICI.isEquality() && RHSV.getActiveBits() <= Ty->getBitWidth()) {
1133 Builder->CreateAnd(Cast->getOperand(0),
1134 ConstantExpr::getTrunc(AndCST, Ty));
1135 NewAnd->takeName(LHSI);
1136 return new ICmpInst(ICI.getPredicate(), NewAnd,
1137 ConstantExpr::getTrunc(RHS, Ty));
1141 // If this is: (X >> C1) & C2 != C3 (where any shift and any compare
1142 // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This
1143 // happens a LOT in code produced by the C front-end, for bitfield
1145 BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0));
1146 if (Shift && !Shift->isShift())
1150 ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0;
1151 Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift.
1152 Type *AndTy = AndCST->getType(); // Type of the and.
1154 // We can fold this as long as we can't shift unknown bits
1155 // into the mask. This can only happen with signed shift
1156 // rights, as they sign-extend.
1158 bool CanFold = Shift->isLogicalShift();
1160 // To test for the bad case of the signed shr, see if any
1161 // of the bits shifted in could be tested after the mask.
1162 uint32_t TyBits = Ty->getPrimitiveSizeInBits();
1163 int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits);
1165 uint32_t BitWidth = AndTy->getPrimitiveSizeInBits();
1166 if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) &
1167 AndCST->getValue()) == 0)
1173 if (Shift->getOpcode() == Instruction::Shl)
1174 NewCst = ConstantExpr::getLShr(RHS, ShAmt);
1176 NewCst = ConstantExpr::getShl(RHS, ShAmt);
1178 // Check to see if we are shifting out any of the bits being
1180 if (ConstantExpr::get(Shift->getOpcode(),
1181 NewCst, ShAmt) != RHS) {
1182 // If we shifted bits out, the fold is not going to work out.
1183 // As a special case, check to see if this means that the
1184 // result is always true or false now.
1185 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
1186 return ReplaceInstUsesWith(ICI,
1187 ConstantInt::getFalse(ICI.getContext()));
1188 if (ICI.getPredicate() == ICmpInst::ICMP_NE)
1189 return ReplaceInstUsesWith(ICI,
1190 ConstantInt::getTrue(ICI.getContext()));
1192 ICI.setOperand(1, NewCst);
1193 Constant *NewAndCST;
1194 if (Shift->getOpcode() == Instruction::Shl)
1195 NewAndCST = ConstantExpr::getLShr(AndCST, ShAmt);
1197 NewAndCST = ConstantExpr::getShl(AndCST, ShAmt);
1198 LHSI->setOperand(1, NewAndCST);
1199 LHSI->setOperand(0, Shift->getOperand(0));
1200 Worklist.Add(Shift); // Shift is dead.
1206 // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is
1207 // preferable because it allows the C<<Y expression to be hoisted out
1208 // of a loop if Y is invariant and X is not.
1209 if (Shift && Shift->hasOneUse() && RHSV == 0 &&
1210 ICI.isEquality() && !Shift->isArithmeticShift() &&
1211 !isa<Constant>(Shift->getOperand(0))) {
1214 if (Shift->getOpcode() == Instruction::LShr) {
1215 NS = Builder->CreateShl(AndCST, Shift->getOperand(1));
1217 // Insert a logical shift.
1218 NS = Builder->CreateLShr(AndCST, Shift->getOperand(1));
1221 // Compute X & (C << Y).
1223 Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName());
1225 ICI.setOperand(0, NewAnd);
1230 // Try to optimize things like "A[i]&42 == 0" to index computations.
1231 if (LoadInst *LI = dyn_cast<LoadInst>(LHSI->getOperand(0))) {
1232 if (GetElementPtrInst *GEP =
1233 dyn_cast<GetElementPtrInst>(LI->getOperand(0)))
1234 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
1235 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
1236 !LI->isVolatile() && isa<ConstantInt>(LHSI->getOperand(1))) {
1237 ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1));
1238 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C))
1244 case Instruction::Or: {
1245 if (!ICI.isEquality() || !RHS->isNullValue() || !LHSI->hasOneUse())
1248 if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) {
1249 // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0
1250 // -> and (icmp eq P, null), (icmp eq Q, null).
1251 Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P,
1252 Constant::getNullValue(P->getType()));
1253 Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q,
1254 Constant::getNullValue(Q->getType()));
1256 if (ICI.getPredicate() == ICmpInst::ICMP_EQ)
1257 Op = BinaryOperator::CreateAnd(ICIP, ICIQ);
1259 Op = BinaryOperator::CreateOr(ICIP, ICIQ);
1265 case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI)
1266 ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1));
1269 uint32_t TypeBits = RHSV.getBitWidth();
1271 // Check that the shift amount is in range. If not, don't perform
1272 // undefined shifts. When the shift is visited it will be
1274 if (ShAmt->uge(TypeBits))
1277 if (ICI.isEquality()) {
1278 // If we are comparing against bits always shifted out, the
1279 // comparison cannot succeed.
1281 ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt),
1283 if (Comp != RHS) {// Comparing against a bit that we know is zero.
1284 bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
1286 ConstantInt::get(Type::getInt1Ty(ICI.getContext()), IsICMP_NE);
1287 return ReplaceInstUsesWith(ICI, Cst);
1290 // If the shift is NUW, then it is just shifting out zeros, no need for an
1292 if (cast<BinaryOperator>(LHSI)->hasNoUnsignedWrap())
1293 return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
1294 ConstantExpr::getLShr(RHS, ShAmt));
1296 if (LHSI->hasOneUse()) {
1297 // Otherwise strength reduce the shift into an and.
1298 uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits);
1300 ConstantInt::get(ICI.getContext(), APInt::getLowBitsSet(TypeBits,
1301 TypeBits-ShAmtVal));
1304 Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask");
1305 return new ICmpInst(ICI.getPredicate(), And,
1306 ConstantExpr::getLShr(RHS, ShAmt));
1310 // Otherwise, if this is a comparison of the sign bit, simplify to and/test.
1311 bool TrueIfSigned = false;
1312 if (LHSI->hasOneUse() &&
1313 isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) {
1314 // (X << 31) <s 0 --> (X&1) != 0
1315 Constant *Mask = ConstantInt::get(LHSI->getOperand(0)->getType(),
1316 APInt::getOneBitSet(TypeBits,
1317 TypeBits-ShAmt->getZExtValue()-1));
1319 Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask");
1320 return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
1321 And, Constant::getNullValue(And->getType()));
1326 case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI)
1327 case Instruction::AShr: {
1328 // Handle equality comparisons of shift-by-constant.
1329 BinaryOperator *BO = cast<BinaryOperator>(LHSI);
1330 if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
1331 if (Instruction *Res = FoldICmpShrCst(ICI, BO, ShAmt))
1335 // Handle exact shr's.
1336 if (ICI.isEquality() && BO->isExact() && BO->hasOneUse()) {
1337 if (RHSV.isMinValue())
1338 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), RHS);
1343 case Instruction::SDiv:
1344 case Instruction::UDiv:
1345 // Fold: icmp pred ([us]div X, C1), C2 -> range test
1346 // Fold this div into the comparison, producing a range check.
1347 // Determine, based on the divide type, what the range is being
1348 // checked. If there is an overflow on the low or high side, remember
1349 // it, otherwise compute the range [low, hi) bounding the new value.
1350 // See: InsertRangeTest above for the kinds of replacements possible.
1351 if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1)))
1352 if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI),
1357 case Instruction::Add:
1358 // Fold: icmp pred (add X, C1), C2
1359 if (!ICI.isEquality()) {
1360 ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1));
1362 const APInt &LHSV = LHSC->getValue();
1364 ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV)
1367 if (ICI.isSigned()) {
1368 if (CR.getLower().isSignBit()) {
1369 return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0),
1370 ConstantInt::get(ICI.getContext(),CR.getUpper()));
1371 } else if (CR.getUpper().isSignBit()) {
1372 return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0),
1373 ConstantInt::get(ICI.getContext(),CR.getLower()));
1376 if (CR.getLower().isMinValue()) {
1377 return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0),
1378 ConstantInt::get(ICI.getContext(),CR.getUpper()));
1379 } else if (CR.getUpper().isMinValue()) {
1380 return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0),
1381 ConstantInt::get(ICI.getContext(),CR.getLower()));
1388 // Simplify icmp_eq and icmp_ne instructions with integer constant RHS.
1389 if (ICI.isEquality()) {
1390 bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE;
1392 // If the first operand is (add|sub|and|or|xor|rem) with a constant, and
1393 // the second operand is a constant, simplify a bit.
1394 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) {
1395 switch (BO->getOpcode()) {
1396 case Instruction::SRem:
1397 // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one.
1398 if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){
1399 const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue();
1400 if (V.sgt(1) && V.isPowerOf2()) {
1402 Builder->CreateURem(BO->getOperand(0), BO->getOperand(1),
1404 return new ICmpInst(ICI.getPredicate(), NewRem,
1405 Constant::getNullValue(BO->getType()));
1409 case Instruction::Add:
1410 // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
1411 if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1412 if (BO->hasOneUse())
1413 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1414 ConstantExpr::getSub(RHS, BOp1C));
1415 } else if (RHSV == 0) {
1416 // Replace ((add A, B) != 0) with (A != -B) if A or B is
1417 // efficiently invertible, or if the add has just this one use.
1418 Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1);
1420 if (Value *NegVal = dyn_castNegVal(BOp1))
1421 return new ICmpInst(ICI.getPredicate(), BOp0, NegVal);
1422 if (Value *NegVal = dyn_castNegVal(BOp0))
1423 return new ICmpInst(ICI.getPredicate(), NegVal, BOp1);
1424 if (BO->hasOneUse()) {
1425 Value *Neg = Builder->CreateNeg(BOp1);
1427 return new ICmpInst(ICI.getPredicate(), BOp0, Neg);
1431 case Instruction::Xor:
1432 // For the xor case, we can xor two constants together, eliminating
1433 // the explicit xor.
1434 if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) {
1435 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1436 ConstantExpr::getXor(RHS, BOC));
1437 } else if (RHSV == 0) {
1438 // Replace ((xor A, B) != 0) with (A != B)
1439 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1443 case Instruction::Sub:
1444 // Replace ((sub A, B) != C) with (B != A-C) if A & C are constants.
1445 if (ConstantInt *BOp0C = dyn_cast<ConstantInt>(BO->getOperand(0))) {
1446 if (BO->hasOneUse())
1447 return new ICmpInst(ICI.getPredicate(), BO->getOperand(1),
1448 ConstantExpr::getSub(BOp0C, RHS));
1449 } else if (RHSV == 0) {
1450 // Replace ((sub A, B) != 0) with (A != B)
1451 return new ICmpInst(ICI.getPredicate(), BO->getOperand(0),
1455 case Instruction::Or:
1456 // If bits are being or'd in that are not present in the constant we
1457 // are comparing against, then the comparison could never succeed!
1458 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1459 Constant *NotCI = ConstantExpr::getNot(RHS);
1460 if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue())
1461 return ReplaceInstUsesWith(ICI,
1462 ConstantInt::get(Type::getInt1Ty(ICI.getContext()),
1467 case Instruction::And:
1468 if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) {
1469 // If bits are being compared against that are and'd out, then the
1470 // comparison can never succeed!
1471 if ((RHSV & ~BOC->getValue()) != 0)
1472 return ReplaceInstUsesWith(ICI,
1473 ConstantInt::get(Type::getInt1Ty(ICI.getContext()),
1476 // If we have ((X & C) == C), turn it into ((X & C) != 0).
1477 if (RHS == BOC && RHSV.isPowerOf2())
1478 return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ :
1479 ICmpInst::ICMP_NE, LHSI,
1480 Constant::getNullValue(RHS->getType()));
1482 // Don't perform the following transforms if the AND has multiple uses
1483 if (!BO->hasOneUse())
1486 // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
1487 if (BOC->getValue().isSignBit()) {
1488 Value *X = BO->getOperand(0);
1489 Constant *Zero = Constant::getNullValue(X->getType());
1490 ICmpInst::Predicate pred = isICMP_NE ?
1491 ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
1492 return new ICmpInst(pred, X, Zero);
1495 // ((X & ~7) == 0) --> X < 8
1496 if (RHSV == 0 && isHighOnes(BOC)) {
1497 Value *X = BO->getOperand(0);
1498 Constant *NegX = ConstantExpr::getNeg(BOC);
1499 ICmpInst::Predicate pred = isICMP_NE ?
1500 ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
1501 return new ICmpInst(pred, X, NegX);
1506 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) {
1507 // Handle icmp {eq|ne} <intrinsic>, intcst.
1508 switch (II->getIntrinsicID()) {
1509 case Intrinsic::bswap:
1511 ICI.setOperand(0, II->getArgOperand(0));
1512 ICI.setOperand(1, ConstantInt::get(II->getContext(), RHSV.byteSwap()));
1514 case Intrinsic::ctlz:
1515 case Intrinsic::cttz:
1516 // ctz(A) == bitwidth(a) -> A == 0 and likewise for !=
1517 if (RHSV == RHS->getType()->getBitWidth()) {
1519 ICI.setOperand(0, II->getArgOperand(0));
1520 ICI.setOperand(1, ConstantInt::get(RHS->getType(), 0));
1524 case Intrinsic::ctpop:
1525 // popcount(A) == 0 -> A == 0 and likewise for !=
1526 if (RHS->isZero()) {
1528 ICI.setOperand(0, II->getArgOperand(0));
1529 ICI.setOperand(1, RHS);
1541 /// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst).
1542 /// We only handle extending casts so far.
1544 Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) {
1545 const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0));
1546 Value *LHSCIOp = LHSCI->getOperand(0);
1547 Type *SrcTy = LHSCIOp->getType();
1548 Type *DestTy = LHSCI->getType();
1551 // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
1552 // integer type is the same size as the pointer type.
1553 if (TD && LHSCI->getOpcode() == Instruction::PtrToInt &&
1554 TD->getPointerSizeInBits() ==
1555 cast<IntegerType>(DestTy)->getBitWidth()) {
1557 if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) {
1558 RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy);
1559 } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) {
1560 RHSOp = RHSC->getOperand(0);
1561 // If the pointer types don't match, insert a bitcast.
1562 if (LHSCIOp->getType() != RHSOp->getType())
1563 RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType());
1567 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp);
1570 // The code below only handles extension cast instructions, so far.
1572 if (LHSCI->getOpcode() != Instruction::ZExt &&
1573 LHSCI->getOpcode() != Instruction::SExt)
1576 bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt;
1577 bool isSignedCmp = ICI.isSigned();
1579 if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) {
1580 // Not an extension from the same type?
1581 RHSCIOp = CI->getOperand(0);
1582 if (RHSCIOp->getType() != LHSCIOp->getType())
1585 // If the signedness of the two casts doesn't agree (i.e. one is a sext
1586 // and the other is a zext), then we can't handle this.
1587 if (CI->getOpcode() != LHSCI->getOpcode())
1590 // Deal with equality cases early.
1591 if (ICI.isEquality())
1592 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
1594 // A signed comparison of sign extended values simplifies into a
1595 // signed comparison.
1596 if (isSignedCmp && isSignedExt)
1597 return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp);
1599 // The other three cases all fold into an unsigned comparison.
1600 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp);
1603 // If we aren't dealing with a constant on the RHS, exit early
1604 ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1));
1608 // Compute the constant that would happen if we truncated to SrcTy then
1609 // reextended to DestTy.
1610 Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy);
1611 Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(),
1614 // If the re-extended constant didn't change...
1616 // Deal with equality cases early.
1617 if (ICI.isEquality())
1618 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
1620 // A signed comparison of sign extended values simplifies into a
1621 // signed comparison.
1622 if (isSignedExt && isSignedCmp)
1623 return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1);
1625 // The other three cases all fold into an unsigned comparison.
1626 return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1);
1629 // The re-extended constant changed so the constant cannot be represented
1630 // in the shorter type. Consequently, we cannot emit a simple comparison.
1631 // All the cases that fold to true or false will have already been handled
1632 // by SimplifyICmpInst, so only deal with the tricky case.
1634 if (isSignedCmp || !isSignedExt)
1637 // Evaluate the comparison for LT (we invert for GT below). LE and GE cases
1638 // should have been folded away previously and not enter in here.
1640 // We're performing an unsigned comp with a sign extended value.
1641 // This is true if the input is >= 0. [aka >s -1]
1642 Constant *NegOne = Constant::getAllOnesValue(SrcTy);
1643 Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName());
1645 // Finally, return the value computed.
1646 if (ICI.getPredicate() == ICmpInst::ICMP_ULT)
1647 return ReplaceInstUsesWith(ICI, Result);
1649 assert(ICI.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
1650 return BinaryOperator::CreateNot(Result);
1653 /// ProcessUGT_ADDCST_ADD - The caller has matched a pattern of the form:
1654 /// I = icmp ugt (add (add A, B), CI2), CI1
1655 /// If this is of the form:
1657 /// if (sum+128 >u 255)
1658 /// Then replace it with llvm.sadd.with.overflow.i8.
1660 static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
1661 ConstantInt *CI2, ConstantInt *CI1,
1663 // The transformation we're trying to do here is to transform this into an
1664 // llvm.sadd.with.overflow. To do this, we have to replace the original add
1665 // with a narrower add, and discard the add-with-constant that is part of the
1666 // range check (if we can't eliminate it, this isn't profitable).
1668 // In order to eliminate the add-with-constant, the compare can be its only
1670 Instruction *AddWithCst = cast<Instruction>(I.getOperand(0));
1671 if (!AddWithCst->hasOneUse()) return 0;
1673 // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow.
1674 if (!CI2->getValue().isPowerOf2()) return 0;
1675 unsigned NewWidth = CI2->getValue().countTrailingZeros();
1676 if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31) return 0;
1678 // The width of the new add formed is 1 more than the bias.
1681 // Check to see that CI1 is an all-ones value with NewWidth bits.
1682 if (CI1->getBitWidth() == NewWidth ||
1683 CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth))
1686 // This is only really a signed overflow check if the inputs have been
1687 // sign-extended; check for that condition. For example, if CI2 is 2^31 and
1688 // the operands of the add are 64 bits wide, we need at least 33 sign bits.
1689 unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1;
1690 if (IC.ComputeNumSignBits(A) < NeededSignBits ||
1691 IC.ComputeNumSignBits(B) < NeededSignBits)
1694 // In order to replace the original add with a narrower
1695 // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant
1696 // and truncates that discard the high bits of the add. Verify that this is
1698 Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0));
1699 for (Value::use_iterator UI = OrigAdd->use_begin(), E = OrigAdd->use_end();
1701 if (*UI == AddWithCst) continue;
1703 // Only accept truncates for now. We would really like a nice recursive
1704 // predicate like SimplifyDemandedBits, but which goes downwards the use-def
1705 // chain to see which bits of a value are actually demanded. If the
1706 // original add had another add which was then immediately truncated, we
1707 // could still do the transformation.
1708 TruncInst *TI = dyn_cast<TruncInst>(*UI);
1710 TI->getType()->getPrimitiveSizeInBits() > NewWidth) return 0;
1713 // If the pattern matches, truncate the inputs to the narrower type and
1714 // use the sadd_with_overflow intrinsic to efficiently compute both the
1715 // result and the overflow bit.
1716 Module *M = I.getParent()->getParent()->getParent();
1718 Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
1719 Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow,
1722 InstCombiner::BuilderTy *Builder = IC.Builder;
1724 // Put the new code above the original add, in case there are any uses of the
1725 // add between the add and the compare.
1726 Builder->SetInsertPoint(OrigAdd);
1728 Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc");
1729 Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc");
1730 CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB, "sadd");
1731 Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result");
1732 Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType());
1734 // The inner add was the result of the narrow add, zero extended to the
1735 // wider type. Replace it with the result computed by the intrinsic.
1736 IC.ReplaceInstUsesWith(*OrigAdd, ZExt);
1738 // The original icmp gets replaced with the overflow value.
1739 return ExtractValueInst::Create(Call, 1, "sadd.overflow");
1742 static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV,
1744 // Don't bother doing this transformation for pointers, don't do it for
1746 if (!isa<IntegerType>(OrigAddV->getType())) return 0;
1748 // If the add is a constant expr, then we don't bother transforming it.
1749 Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV);
1750 if (OrigAdd == 0) return 0;
1752 Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1);
1754 // Put the new code above the original add, in case there are any uses of the
1755 // add between the add and the compare.
1756 InstCombiner::BuilderTy *Builder = IC.Builder;
1757 Builder->SetInsertPoint(OrigAdd);
1759 Module *M = I.getParent()->getParent()->getParent();
1760 Type *Ty = LHS->getType();
1761 Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, Ty);
1762 CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd");
1763 Value *Add = Builder->CreateExtractValue(Call, 0);
1765 IC.ReplaceInstUsesWith(*OrigAdd, Add);
1767 // The original icmp gets replaced with the overflow value.
1768 return ExtractValueInst::Create(Call, 1, "uadd.overflow");
1771 // DemandedBitsLHSMask - When performing a comparison against a constant,
1772 // it is possible that not all the bits in the LHS are demanded. This helper
1773 // method computes the mask that IS demanded.
1774 static APInt DemandedBitsLHSMask(ICmpInst &I,
1775 unsigned BitWidth, bool isSignCheck) {
1777 return APInt::getSignBit(BitWidth);
1779 ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(1));
1780 if (!CI) return APInt::getAllOnesValue(BitWidth);
1781 const APInt &RHS = CI->getValue();
1783 switch (I.getPredicate()) {
1784 // For a UGT comparison, we don't care about any bits that
1785 // correspond to the trailing ones of the comparand. The value of these
1786 // bits doesn't impact the outcome of the comparison, because any value
1787 // greater than the RHS must differ in a bit higher than these due to carry.
1788 case ICmpInst::ICMP_UGT: {
1789 unsigned trailingOnes = RHS.countTrailingOnes();
1790 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingOnes);
1794 // Similarly, for a ULT comparison, we don't care about the trailing zeros.
1795 // Any value less than the RHS must differ in a higher bit because of carries.
1796 case ICmpInst::ICMP_ULT: {
1797 unsigned trailingZeros = RHS.countTrailingZeros();
1798 APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingZeros);
1803 return APInt::getAllOnesValue(BitWidth);
1808 Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
1809 bool Changed = false;
1810 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1812 /// Orders the operands of the compare so that they are listed from most
1813 /// complex to least complex. This puts constants before unary operators,
1814 /// before binary operators.
1815 if (getComplexity(Op0) < getComplexity(Op1)) {
1817 std::swap(Op0, Op1);
1821 if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, TD))
1822 return ReplaceInstUsesWith(I, V);
1824 // comparing -val or val with non-zero is the same as just comparing val
1825 // ie, abs(val) != 0 -> val != 0
1826 if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero()))
1828 Value *Cond, *SelectTrue, *SelectFalse;
1829 if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue),
1830 m_Value(SelectFalse)))) {
1831 if (Value *V = dyn_castNegVal(SelectTrue)) {
1832 if (V == SelectFalse)
1833 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
1835 else if (Value *V = dyn_castNegVal(SelectFalse)) {
1836 if (V == SelectTrue)
1837 return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1);
1842 Type *Ty = Op0->getType();
1844 // icmp's with boolean values can always be turned into bitwise operations
1845 if (Ty->isIntegerTy(1)) {
1846 switch (I.getPredicate()) {
1847 default: llvm_unreachable("Invalid icmp instruction!");
1848 case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B)
1849 Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp");
1850 return BinaryOperator::CreateNot(Xor);
1852 case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B
1853 return BinaryOperator::CreateXor(Op0, Op1);
1855 case ICmpInst::ICMP_UGT:
1856 std::swap(Op0, Op1); // Change icmp ugt -> icmp ult
1858 case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B
1859 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
1860 return BinaryOperator::CreateAnd(Not, Op1);
1862 case ICmpInst::ICMP_SGT:
1863 std::swap(Op0, Op1); // Change icmp sgt -> icmp slt
1865 case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B
1866 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
1867 return BinaryOperator::CreateAnd(Not, Op0);
1869 case ICmpInst::ICMP_UGE:
1870 std::swap(Op0, Op1); // Change icmp uge -> icmp ule
1872 case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B
1873 Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp");
1874 return BinaryOperator::CreateOr(Not, Op1);
1876 case ICmpInst::ICMP_SGE:
1877 std::swap(Op0, Op1); // Change icmp sge -> icmp sle
1879 case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B
1880 Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp");
1881 return BinaryOperator::CreateOr(Not, Op0);
1886 unsigned BitWidth = 0;
1887 if (Ty->isIntOrIntVectorTy())
1888 BitWidth = Ty->getScalarSizeInBits();
1889 else if (TD) // Pointers require TD info to get their size.
1890 BitWidth = TD->getTypeSizeInBits(Ty->getScalarType());
1892 bool isSignBit = false;
1894 // See if we are doing a comparison with a constant.
1895 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
1896 Value *A = 0, *B = 0;
1898 // Match the following pattern, which is a common idiom when writing
1899 // overflow-safe integer arithmetic function. The source performs an
1900 // addition in wider type, and explicitly checks for overflow using
1901 // comparisons against INT_MIN and INT_MAX. Simplify this by using the
1902 // sadd_with_overflow intrinsic.
1904 // TODO: This could probably be generalized to handle other overflow-safe
1905 // operations if we worked out the formulas to compute the appropriate
1909 // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8
1911 ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI
1912 if (I.getPredicate() == ICmpInst::ICMP_UGT &&
1913 match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2))))
1914 if (Instruction *Res = ProcessUGT_ADDCST_ADD(I, A, B, CI2, CI, *this))
1918 // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
1919 if (I.isEquality() && CI->isZero() &&
1920 match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
1921 // (icmp cond A B) if cond is equality
1922 return new ICmpInst(I.getPredicate(), A, B);
1925 // If we have an icmp le or icmp ge instruction, turn it into the
1926 // appropriate icmp lt or icmp gt instruction. This allows us to rely on
1927 // them being folded in the code below. The SimplifyICmpInst code has
1928 // already handled the edge cases for us, so we just assert on them.
1929 switch (I.getPredicate()) {
1931 case ICmpInst::ICMP_ULE:
1932 assert(!CI->isMaxValue(false)); // A <=u MAX -> TRUE
1933 return new ICmpInst(ICmpInst::ICMP_ULT, Op0,
1934 ConstantInt::get(CI->getContext(), CI->getValue()+1));
1935 case ICmpInst::ICMP_SLE:
1936 assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE
1937 return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
1938 ConstantInt::get(CI->getContext(), CI->getValue()+1));
1939 case ICmpInst::ICMP_UGE:
1940 assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE
1941 return new ICmpInst(ICmpInst::ICMP_UGT, Op0,
1942 ConstantInt::get(CI->getContext(), CI->getValue()-1));
1943 case ICmpInst::ICMP_SGE:
1944 assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE
1945 return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
1946 ConstantInt::get(CI->getContext(), CI->getValue()-1));
1949 // If this comparison is a normal comparison, it demands all
1950 // bits, if it is a sign bit comparison, it only demands the sign bit.
1952 isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit);
1955 // See if we can fold the comparison based on range information we can get
1956 // by checking whether bits are known to be zero or one in the input.
1957 if (BitWidth != 0) {
1958 APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0);
1959 APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0);
1961 if (SimplifyDemandedBits(I.getOperandUse(0),
1962 DemandedBitsLHSMask(I, BitWidth, isSignBit),
1963 Op0KnownZero, Op0KnownOne, 0))
1965 if (SimplifyDemandedBits(I.getOperandUse(1),
1966 APInt::getAllOnesValue(BitWidth),
1967 Op1KnownZero, Op1KnownOne, 0))
1970 // Given the known and unknown bits, compute a range that the LHS could be
1971 // in. Compute the Min, Max and RHS values based on the known bits. For the
1972 // EQ and NE we use unsigned values.
1973 APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0);
1974 APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0);
1976 ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
1978 ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
1981 ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne,
1983 ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne,
1987 // If Min and Max are known to be the same, then SimplifyDemandedBits
1988 // figured out that the LHS is a constant. Just constant fold this now so
1989 // that code below can assume that Min != Max.
1990 if (!isa<Constant>(Op0) && Op0Min == Op0Max)
1991 return new ICmpInst(I.getPredicate(),
1992 ConstantInt::get(Op0->getType(), Op0Min), Op1);
1993 if (!isa<Constant>(Op1) && Op1Min == Op1Max)
1994 return new ICmpInst(I.getPredicate(), Op0,
1995 ConstantInt::get(Op1->getType(), Op1Min));
1997 // Based on the range information we know about the LHS, see if we can
1998 // simplify this comparison. For example, (x&4) < 8 is always true.
1999 switch (I.getPredicate()) {
2000 default: llvm_unreachable("Unknown icmp opcode!");
2001 case ICmpInst::ICMP_EQ: {
2002 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
2003 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2005 // If all bits are known zero except for one, then we know at most one
2006 // bit is set. If the comparison is against zero, then this is a check
2007 // to see if *that* bit is set.
2008 APInt Op0KnownZeroInverted = ~Op0KnownZero;
2009 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
2010 // If the LHS is an AND with the same constant, look through it.
2012 ConstantInt *LHSC = 0;
2013 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
2014 LHSC->getValue() != Op0KnownZeroInverted)
2017 // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
2018 // then turn "((1 << x)&8) == 0" into "x != 3".
2020 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
2021 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
2022 return new ICmpInst(ICmpInst::ICMP_NE, X,
2023 ConstantInt::get(X->getType(), CmpVal));
2026 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
2027 // then turn "((8 >>u x)&1) == 0" into "x != 3".
2029 if (Op0KnownZeroInverted == 1 &&
2030 match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
2031 return new ICmpInst(ICmpInst::ICMP_NE, X,
2032 ConstantInt::get(X->getType(),
2033 CI->countTrailingZeros()));
2038 case ICmpInst::ICMP_NE: {
2039 if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
2040 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2042 // If all bits are known zero except for one, then we know at most one
2043 // bit is set. If the comparison is against zero, then this is a check
2044 // to see if *that* bit is set.
2045 APInt Op0KnownZeroInverted = ~Op0KnownZero;
2046 if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
2047 // If the LHS is an AND with the same constant, look through it.
2049 ConstantInt *LHSC = 0;
2050 if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) ||
2051 LHSC->getValue() != Op0KnownZeroInverted)
2054 // If the LHS is 1 << x, and we know the result is a power of 2 like 8,
2055 // then turn "((1 << x)&8) != 0" into "x == 3".
2057 if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
2058 unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
2059 return new ICmpInst(ICmpInst::ICMP_EQ, X,
2060 ConstantInt::get(X->getType(), CmpVal));
2063 // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
2064 // then turn "((8 >>u x)&1) != 0" into "x == 3".
2066 if (Op0KnownZeroInverted == 1 &&
2067 match(LHS, m_LShr(m_Power2(CI), m_Value(X))))
2068 return new ICmpInst(ICmpInst::ICMP_EQ, X,
2069 ConstantInt::get(X->getType(),
2070 CI->countTrailingZeros()));
2075 case ICmpInst::ICMP_ULT:
2076 if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
2077 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2078 if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
2079 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2080 if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B)
2081 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2082 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2083 if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C
2084 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2085 ConstantInt::get(CI->getContext(), CI->getValue()-1));
2087 // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear
2088 if (CI->isMinValue(true))
2089 return new ICmpInst(ICmpInst::ICMP_SGT, Op0,
2090 Constant::getAllOnesValue(Op0->getType()));
2093 case ICmpInst::ICMP_UGT:
2094 if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
2095 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2096 if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
2097 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2099 if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B)
2100 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2101 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2102 if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C
2103 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2104 ConstantInt::get(CI->getContext(), CI->getValue()+1));
2106 // (x >u 2147483647) -> (x <s 0) -> true if sign bit set
2107 if (CI->isMaxValue(true))
2108 return new ICmpInst(ICmpInst::ICMP_SLT, Op0,
2109 Constant::getNullValue(Op0->getType()));
2112 case ICmpInst::ICMP_SLT:
2113 if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
2114 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2115 if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
2116 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2117 if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B)
2118 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2119 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2120 if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C
2121 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2122 ConstantInt::get(CI->getContext(), CI->getValue()-1));
2125 case ICmpInst::ICMP_SGT:
2126 if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
2127 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2128 if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
2129 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2131 if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B)
2132 return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
2133 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2134 if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C
2135 return new ICmpInst(ICmpInst::ICMP_EQ, Op0,
2136 ConstantInt::get(CI->getContext(), CI->getValue()+1));
2139 case ICmpInst::ICMP_SGE:
2140 assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
2141 if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
2142 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2143 if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
2144 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2146 case ICmpInst::ICMP_SLE:
2147 assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
2148 if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
2149 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2150 if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
2151 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2153 case ICmpInst::ICMP_UGE:
2154 assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
2155 if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
2156 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2157 if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
2158 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2160 case ICmpInst::ICMP_ULE:
2161 assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
2162 if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
2163 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2164 if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
2165 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2169 // Turn a signed comparison into an unsigned one if both operands
2170 // are known to have the same sign.
2172 ((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) ||
2173 (Op0KnownOne.isNegative() && Op1KnownOne.isNegative())))
2174 return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1);
2177 // Test if the ICmpInst instruction is used exclusively by a select as
2178 // part of a minimum or maximum operation. If so, refrain from doing
2179 // any other folding. This helps out other analyses which understand
2180 // non-obfuscated minimum and maximum idioms, such as ScalarEvolution
2181 // and CodeGen. And in this case, at least one of the comparison
2182 // operands has at least one user besides the compare (the select),
2183 // which would often largely negate the benefit of folding anyway.
2185 if (SelectInst *SI = dyn_cast<SelectInst>(*I.use_begin()))
2186 if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) ||
2187 (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
2190 // See if we are doing a comparison between a constant and an instruction that
2191 // can be folded into the comparison.
2192 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
2193 // Since the RHS is a ConstantInt (CI), if the left hand side is an
2194 // instruction, see if that instruction also has constants so that the
2195 // instruction can be folded into the icmp
2196 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2197 if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI))
2201 // Handle icmp with constant (but not simple integer constant) RHS
2202 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
2203 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2204 switch (LHSI->getOpcode()) {
2205 case Instruction::GetElementPtr:
2206 // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null
2207 if (RHSC->isNullValue() &&
2208 cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices())
2209 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
2210 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2212 case Instruction::PHI:
2213 // Only fold icmp into the PHI if the phi and icmp are in the same
2214 // block. If in the same block, we're encouraging jump threading. If
2215 // not, we are just pessimizing the code by making an i1 phi.
2216 if (LHSI->getParent() == I.getParent())
2217 if (Instruction *NV = FoldOpIntoPhi(I))
2220 case Instruction::Select: {
2221 // If either operand of the select is a constant, we can fold the
2222 // comparison into the select arms, which will cause one to be
2223 // constant folded and the select turned into a bitwise or.
2224 Value *Op1 = 0, *Op2 = 0;
2225 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1)))
2226 Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2227 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2)))
2228 Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC);
2230 // We only want to perform this transformation if it will not lead to
2231 // additional code. This is true if either both sides of the select
2232 // fold to a constant (in which case the icmp is replaced with a select
2233 // which will usually simplify) or this is the only user of the
2234 // select (in which case we are trading a select+icmp for a simpler
2236 if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) {
2238 Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1),
2241 Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2),
2243 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2247 case Instruction::IntToPtr:
2248 // icmp pred inttoptr(X), null -> icmp pred X, 0
2249 if (RHSC->isNullValue() && TD &&
2250 TD->getIntPtrType(RHSC->getContext()) ==
2251 LHSI->getOperand(0)->getType())
2252 return new ICmpInst(I.getPredicate(), LHSI->getOperand(0),
2253 Constant::getNullValue(LHSI->getOperand(0)->getType()));
2256 case Instruction::Load:
2257 // Try to optimize things like "A[i] > 4" to index computations.
2258 if (GetElementPtrInst *GEP =
2259 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2260 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2261 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2262 !cast<LoadInst>(LHSI)->isVolatile())
2263 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
2270 // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now.
2271 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0))
2272 if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I))
2274 if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1))
2275 if (Instruction *NI = FoldGEPICmp(GEP, Op0,
2276 ICmpInst::getSwappedPredicate(I.getPredicate()), I))
2279 // Test to see if the operands of the icmp are casted versions of other
2280 // values. If the ptr->ptr cast can be stripped off both arguments, we do so
2282 if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) {
2283 if (Op0->getType()->isPointerTy() &&
2284 (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) {
2285 // We keep moving the cast from the left operand over to the right
2286 // operand, where it can often be eliminated completely.
2287 Op0 = CI->getOperand(0);
2289 // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast
2290 // so eliminate it as well.
2291 if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1))
2292 Op1 = CI2->getOperand(0);
2294 // If Op1 is a constant, we can fold the cast into the constant.
2295 if (Op0->getType() != Op1->getType()) {
2296 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
2297 Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType());
2299 // Otherwise, cast the RHS right before the icmp
2300 Op1 = Builder->CreateBitCast(Op1, Op0->getType());
2303 return new ICmpInst(I.getPredicate(), Op0, Op1);
2307 if (isa<CastInst>(Op0)) {
2308 // Handle the special case of: icmp (cast bool to X), <cst>
2309 // This comes up when you have code like
2312 // For generality, we handle any zero-extension of any operand comparison
2313 // with a constant or another cast from the same type.
2314 if (isa<Constant>(Op1) || isa<CastInst>(Op1))
2315 if (Instruction *R = visitICmpInstWithCastAndCast(I))
2319 // Special logic for binary operators.
2320 BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0);
2321 BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1);
2323 CmpInst::Predicate Pred = I.getPredicate();
2324 bool NoOp0WrapProblem = false, NoOp1WrapProblem = false;
2325 if (BO0 && isa<OverflowingBinaryOperator>(BO0))
2326 NoOp0WrapProblem = ICmpInst::isEquality(Pred) ||
2327 (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) ||
2328 (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap());
2329 if (BO1 && isa<OverflowingBinaryOperator>(BO1))
2330 NoOp1WrapProblem = ICmpInst::isEquality(Pred) ||
2331 (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) ||
2332 (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap());
2334 // Analyze the case when either Op0 or Op1 is an add instruction.
2335 // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null).
2336 Value *A = 0, *B = 0, *C = 0, *D = 0;
2337 if (BO0 && BO0->getOpcode() == Instruction::Add)
2338 A = BO0->getOperand(0), B = BO0->getOperand(1);
2339 if (BO1 && BO1->getOpcode() == Instruction::Add)
2340 C = BO1->getOperand(0), D = BO1->getOperand(1);
2342 // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow.
2343 if ((A == Op1 || B == Op1) && NoOp0WrapProblem)
2344 return new ICmpInst(Pred, A == Op1 ? B : A,
2345 Constant::getNullValue(Op1->getType()));
2347 // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow.
2348 if ((C == Op0 || D == Op0) && NoOp1WrapProblem)
2349 return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()),
2352 // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow.
2353 if (A && C && (A == C || A == D || B == C || B == D) &&
2354 NoOp0WrapProblem && NoOp1WrapProblem &&
2355 // Try not to increase register pressure.
2356 BO0->hasOneUse() && BO1->hasOneUse()) {
2357 // Determine Y and Z in the form icmp (X+Y), (X+Z).
2358 Value *Y = (A == C || A == D) ? B : A;
2359 Value *Z = (C == A || C == B) ? D : C;
2360 return new ICmpInst(Pred, Y, Z);
2363 // Analyze the case when either Op0 or Op1 is a sub instruction.
2364 // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null).
2365 A = 0; B = 0; C = 0; D = 0;
2366 if (BO0 && BO0->getOpcode() == Instruction::Sub)
2367 A = BO0->getOperand(0), B = BO0->getOperand(1);
2368 if (BO1 && BO1->getOpcode() == Instruction::Sub)
2369 C = BO1->getOperand(0), D = BO1->getOperand(1);
2371 // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow.
2372 if (A == Op1 && NoOp0WrapProblem)
2373 return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B);
2375 // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow.
2376 if (C == Op0 && NoOp1WrapProblem)
2377 return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType()));
2379 // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow.
2380 if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem &&
2381 // Try not to increase register pressure.
2382 BO0->hasOneUse() && BO1->hasOneUse())
2383 return new ICmpInst(Pred, A, C);
2385 // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow.
2386 if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem &&
2387 // Try not to increase register pressure.
2388 BO0->hasOneUse() && BO1->hasOneUse())
2389 return new ICmpInst(Pred, D, B);
2391 BinaryOperator *SRem = NULL;
2392 // icmp (srem X, Y), Y
2393 if (BO0 && BO0->getOpcode() == Instruction::SRem &&
2394 Op1 == BO0->getOperand(1))
2396 // icmp Y, (srem X, Y)
2397 else if (BO1 && BO1->getOpcode() == Instruction::SRem &&
2398 Op0 == BO1->getOperand(1))
2401 // We don't check hasOneUse to avoid increasing register pressure because
2402 // the value we use is the same value this instruction was already using.
2403 switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) {
2405 case ICmpInst::ICMP_EQ:
2406 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
2407 case ICmpInst::ICMP_NE:
2408 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
2409 case ICmpInst::ICMP_SGT:
2410 case ICmpInst::ICMP_SGE:
2411 return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1),
2412 Constant::getAllOnesValue(SRem->getType()));
2413 case ICmpInst::ICMP_SLT:
2414 case ICmpInst::ICMP_SLE:
2415 return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1),
2416 Constant::getNullValue(SRem->getType()));
2420 if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() &&
2421 BO0->hasOneUse() && BO1->hasOneUse() &&
2422 BO0->getOperand(1) == BO1->getOperand(1)) {
2423 switch (BO0->getOpcode()) {
2425 case Instruction::Add:
2426 case Instruction::Sub:
2427 case Instruction::Xor:
2428 if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b
2429 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
2430 BO1->getOperand(0));
2431 // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b
2432 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
2433 if (CI->getValue().isSignBit()) {
2434 ICmpInst::Predicate Pred = I.isSigned()
2435 ? I.getUnsignedPredicate()
2436 : I.getSignedPredicate();
2437 return new ICmpInst(Pred, BO0->getOperand(0),
2438 BO1->getOperand(0));
2441 if (CI->isMaxValue(true)) {
2442 ICmpInst::Predicate Pred = I.isSigned()
2443 ? I.getUnsignedPredicate()
2444 : I.getSignedPredicate();
2445 Pred = I.getSwappedPredicate(Pred);
2446 return new ICmpInst(Pred, BO0->getOperand(0),
2447 BO1->getOperand(0));
2451 case Instruction::Mul:
2452 if (!I.isEquality())
2455 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) {
2456 // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask
2457 // Mask = -1 >> count-trailing-zeros(Cst).
2458 if (!CI->isZero() && !CI->isOne()) {
2459 const APInt &AP = CI->getValue();
2460 ConstantInt *Mask = ConstantInt::get(I.getContext(),
2461 APInt::getLowBitsSet(AP.getBitWidth(),
2463 AP.countTrailingZeros()));
2464 Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask);
2465 Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask);
2466 return new ICmpInst(I.getPredicate(), And1, And2);
2470 case Instruction::UDiv:
2471 case Instruction::LShr:
2475 case Instruction::SDiv:
2476 case Instruction::AShr:
2477 if (!BO0->isExact() || !BO1->isExact())
2479 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
2480 BO1->getOperand(0));
2481 case Instruction::Shl: {
2482 bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
2483 bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
2486 if (!NSW && I.isSigned())
2488 return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
2489 BO1->getOperand(0));
2496 // ~x < ~y --> y < x
2497 // ~x < cst --> ~cst < x
2498 if (match(Op0, m_Not(m_Value(A)))) {
2499 if (match(Op1, m_Not(m_Value(B))))
2500 return new ICmpInst(I.getPredicate(), B, A);
2501 if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1))
2502 return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A);
2505 // (a+b) <u a --> llvm.uadd.with.overflow.
2506 // (a+b) <u b --> llvm.uadd.with.overflow.
2507 if (I.getPredicate() == ICmpInst::ICMP_ULT &&
2508 match(Op0, m_Add(m_Value(A), m_Value(B))) &&
2509 (Op1 == A || Op1 == B))
2510 if (Instruction *R = ProcessUAddIdiom(I, Op0, *this))
2513 // a >u (a+b) --> llvm.uadd.with.overflow.
2514 // b >u (a+b) --> llvm.uadd.with.overflow.
2515 if (I.getPredicate() == ICmpInst::ICMP_UGT &&
2516 match(Op1, m_Add(m_Value(A), m_Value(B))) &&
2517 (Op0 == A || Op0 == B))
2518 if (Instruction *R = ProcessUAddIdiom(I, Op1, *this))
2522 if (I.isEquality()) {
2523 Value *A, *B, *C, *D;
2525 if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
2526 if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0
2527 Value *OtherVal = A == Op1 ? B : A;
2528 return new ICmpInst(I.getPredicate(), OtherVal,
2529 Constant::getNullValue(A->getType()));
2532 if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) {
2533 // A^c1 == C^c2 --> A == C^(c1^c2)
2534 ConstantInt *C1, *C2;
2535 if (match(B, m_ConstantInt(C1)) &&
2536 match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) {
2537 Constant *NC = ConstantInt::get(I.getContext(),
2538 C1->getValue() ^ C2->getValue());
2539 Value *Xor = Builder->CreateXor(C, NC);
2540 return new ICmpInst(I.getPredicate(), A, Xor);
2543 // A^B == A^D -> B == D
2544 if (A == C) return new ICmpInst(I.getPredicate(), B, D);
2545 if (A == D) return new ICmpInst(I.getPredicate(), B, C);
2546 if (B == C) return new ICmpInst(I.getPredicate(), A, D);
2547 if (B == D) return new ICmpInst(I.getPredicate(), A, C);
2551 if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
2552 (A == Op0 || B == Op0)) {
2553 // A == (A^B) -> B == 0
2554 Value *OtherVal = A == Op0 ? B : A;
2555 return new ICmpInst(I.getPredicate(), OtherVal,
2556 Constant::getNullValue(A->getType()));
2559 // (X&Z) == (Y&Z) -> (X^Y) & Z == 0
2560 if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) &&
2561 match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) {
2562 Value *X = 0, *Y = 0, *Z = 0;
2565 X = B; Y = D; Z = A;
2566 } else if (A == D) {
2567 X = B; Y = C; Z = A;
2568 } else if (B == C) {
2569 X = A; Y = D; Z = B;
2570 } else if (B == D) {
2571 X = A; Y = C; Z = B;
2574 if (X) { // Build (X^Y) & Z
2575 Op1 = Builder->CreateXor(X, Y);
2576 Op1 = Builder->CreateAnd(Op1, Z);
2577 I.setOperand(0, Op1);
2578 I.setOperand(1, Constant::getNullValue(Op1->getType()));
2583 // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to
2584 // "icmp (and X, mask), cst"
2587 if (Op0->hasOneUse() &&
2588 match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A),
2589 m_ConstantInt(ShAmt))))) &&
2590 match(Op1, m_ConstantInt(Cst1)) &&
2591 // Only do this when A has multiple uses. This is most important to do
2592 // when it exposes other optimizations.
2594 unsigned ASize =cast<IntegerType>(A->getType())->getPrimitiveSizeInBits();
2596 if (ShAmt < ASize) {
2598 APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits());
2601 APInt CmpV = Cst1->getValue().zext(ASize);
2604 Value *Mask = Builder->CreateAnd(A, Builder->getInt(MaskV));
2605 return new ICmpInst(I.getPredicate(), Mask, Builder->getInt(CmpV));
2611 Value *X; ConstantInt *Cst;
2613 if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X)
2614 return FoldICmpAddOpCst(I, X, Cst, I.getPredicate(), Op0);
2617 if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X)
2618 return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1);
2620 return Changed ? &I : 0;
2628 /// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible.
2630 Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I,
2633 if (!isa<ConstantFP>(RHSC)) return 0;
2634 const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF();
2636 // Get the width of the mantissa. We don't want to hack on conversions that
2637 // might lose information from the integer, e.g. "i64 -> float"
2638 int MantissaWidth = LHSI->getType()->getFPMantissaWidth();
2639 if (MantissaWidth == -1) return 0; // Unknown.
2641 // Check to see that the input is converted from an integer type that is small
2642 // enough that preserves all bits. TODO: check here for "known" sign bits.
2643 // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e.
2644 unsigned InputSize = LHSI->getOperand(0)->getType()->getScalarSizeInBits();
2646 // If this is a uitofp instruction, we need an extra bit to hold the sign.
2647 bool LHSUnsigned = isa<UIToFPInst>(LHSI);
2651 // If the conversion would lose info, don't hack on this.
2652 if ((int)InputSize > MantissaWidth)
2655 // Otherwise, we can potentially simplify the comparison. We know that it
2656 // will always come through as an integer value and we know the constant is
2657 // not a NAN (it would have been previously simplified).
2658 assert(!RHS.isNaN() && "NaN comparison not already folded!");
2660 ICmpInst::Predicate Pred;
2661 switch (I.getPredicate()) {
2662 default: llvm_unreachable("Unexpected predicate!");
2663 case FCmpInst::FCMP_UEQ:
2664 case FCmpInst::FCMP_OEQ:
2665 Pred = ICmpInst::ICMP_EQ;
2667 case FCmpInst::FCMP_UGT:
2668 case FCmpInst::FCMP_OGT:
2669 Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT;
2671 case FCmpInst::FCMP_UGE:
2672 case FCmpInst::FCMP_OGE:
2673 Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE;
2675 case FCmpInst::FCMP_ULT:
2676 case FCmpInst::FCMP_OLT:
2677 Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT;
2679 case FCmpInst::FCMP_ULE:
2680 case FCmpInst::FCMP_OLE:
2681 Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE;
2683 case FCmpInst::FCMP_UNE:
2684 case FCmpInst::FCMP_ONE:
2685 Pred = ICmpInst::ICMP_NE;
2687 case FCmpInst::FCMP_ORD:
2688 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2689 case FCmpInst::FCMP_UNO:
2690 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2693 IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType());
2695 // Now we know that the APFloat is a normal number, zero or inf.
2697 // See if the FP constant is too large for the integer. For example,
2698 // comparing an i8 to 300.0.
2699 unsigned IntWidth = IntTy->getScalarSizeInBits();
2702 // If the RHS value is > SignedMax, fold the comparison. This handles +INF
2703 // and large values.
2704 APFloat SMax(RHS.getSemantics(), APFloat::fcZero, false);
2705 SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true,
2706 APFloat::rmNearestTiesToEven);
2707 if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0
2708 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT ||
2709 Pred == ICmpInst::ICMP_SLE)
2710 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2711 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2714 // If the RHS value is > UnsignedMax, fold the comparison. This handles
2715 // +INF and large values.
2716 APFloat UMax(RHS.getSemantics(), APFloat::fcZero, false);
2717 UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false,
2718 APFloat::rmNearestTiesToEven);
2719 if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0
2720 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT ||
2721 Pred == ICmpInst::ICMP_ULE)
2722 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2723 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2728 // See if the RHS value is < SignedMin.
2729 APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false);
2730 SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true,
2731 APFloat::rmNearestTiesToEven);
2732 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0
2733 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT ||
2734 Pred == ICmpInst::ICMP_SGE)
2735 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2736 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2739 // See if the RHS value is < UnsignedMin.
2740 APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false);
2741 SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true,
2742 APFloat::rmNearestTiesToEven);
2743 if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0
2744 if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT ||
2745 Pred == ICmpInst::ICMP_UGE)
2746 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2747 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2751 // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or
2752 // [0, UMAX], but it may still be fractional. See if it is fractional by
2753 // casting the FP value to the integer value and back, checking for equality.
2754 // Don't do this for zero, because -0.0 is not fractional.
2755 Constant *RHSInt = LHSUnsigned
2756 ? ConstantExpr::getFPToUI(RHSC, IntTy)
2757 : ConstantExpr::getFPToSI(RHSC, IntTy);
2758 if (!RHS.isZero()) {
2759 bool Equal = LHSUnsigned
2760 ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC
2761 : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC;
2763 // If we had a comparison against a fractional value, we have to adjust
2764 // the compare predicate and sometimes the value. RHSC is rounded towards
2765 // zero at this point.
2767 default: llvm_unreachable("Unexpected integer comparison!");
2768 case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true
2769 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2770 case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false
2771 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2772 case ICmpInst::ICMP_ULE:
2773 // (float)int <= 4.4 --> int <= 4
2774 // (float)int <= -4.4 --> false
2775 if (RHS.isNegative())
2776 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2778 case ICmpInst::ICMP_SLE:
2779 // (float)int <= 4.4 --> int <= 4
2780 // (float)int <= -4.4 --> int < -4
2781 if (RHS.isNegative())
2782 Pred = ICmpInst::ICMP_SLT;
2784 case ICmpInst::ICMP_ULT:
2785 // (float)int < -4.4 --> false
2786 // (float)int < 4.4 --> int <= 4
2787 if (RHS.isNegative())
2788 return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext()));
2789 Pred = ICmpInst::ICMP_ULE;
2791 case ICmpInst::ICMP_SLT:
2792 // (float)int < -4.4 --> int < -4
2793 // (float)int < 4.4 --> int <= 4
2794 if (!RHS.isNegative())
2795 Pred = ICmpInst::ICMP_SLE;
2797 case ICmpInst::ICMP_UGT:
2798 // (float)int > 4.4 --> int > 4
2799 // (float)int > -4.4 --> true
2800 if (RHS.isNegative())
2801 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2803 case ICmpInst::ICMP_SGT:
2804 // (float)int > 4.4 --> int > 4
2805 // (float)int > -4.4 --> int >= -4
2806 if (RHS.isNegative())
2807 Pred = ICmpInst::ICMP_SGE;
2809 case ICmpInst::ICMP_UGE:
2810 // (float)int >= -4.4 --> true
2811 // (float)int >= 4.4 --> int > 4
2812 if (!RHS.isNegative())
2813 return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getContext()));
2814 Pred = ICmpInst::ICMP_UGT;
2816 case ICmpInst::ICMP_SGE:
2817 // (float)int >= -4.4 --> int >= -4
2818 // (float)int >= 4.4 --> int > 4
2819 if (!RHS.isNegative())
2820 Pred = ICmpInst::ICMP_SGT;
2826 // Lower this FP comparison into an appropriate integer version of the
2828 return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt);
2831 Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
2832 bool Changed = false;
2834 /// Orders the operands of the compare so that they are listed from most
2835 /// complex to least complex. This puts constants before unary operators,
2836 /// before binary operators.
2837 if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) {
2842 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
2844 if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, TD))
2845 return ReplaceInstUsesWith(I, V);
2847 // Simplify 'fcmp pred X, X'
2849 switch (I.getPredicate()) {
2850 default: llvm_unreachable("Unknown predicate!");
2851 case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y)
2852 case FCmpInst::FCMP_ULT: // True if unordered or less than
2853 case FCmpInst::FCMP_UGT: // True if unordered or greater than
2854 case FCmpInst::FCMP_UNE: // True if unordered or not equal
2855 // Canonicalize these to be 'fcmp uno %X, 0.0'.
2856 I.setPredicate(FCmpInst::FCMP_UNO);
2857 I.setOperand(1, Constant::getNullValue(Op0->getType()));
2860 case FCmpInst::FCMP_ORD: // True if ordered (no nans)
2861 case FCmpInst::FCMP_OEQ: // True if ordered and equal
2862 case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal
2863 case FCmpInst::FCMP_OLE: // True if ordered and less than or equal
2864 // Canonicalize these to be 'fcmp ord %X, 0.0'.
2865 I.setPredicate(FCmpInst::FCMP_ORD);
2866 I.setOperand(1, Constant::getNullValue(Op0->getType()));
2871 // Handle fcmp with constant RHS
2872 if (Constant *RHSC = dyn_cast<Constant>(Op1)) {
2873 if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
2874 switch (LHSI->getOpcode()) {
2875 case Instruction::FPExt: {
2876 // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless
2877 FPExtInst *LHSExt = cast<FPExtInst>(LHSI);
2878 ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC);
2882 // We can't convert a PPC double double.
2883 if (RHSF->getType()->isPPC_FP128Ty())
2886 const fltSemantics *Sem;
2887 // FIXME: This shouldn't be here.
2888 if (LHSExt->getSrcTy()->isHalfTy())
2889 Sem = &APFloat::IEEEhalf;
2890 else if (LHSExt->getSrcTy()->isFloatTy())
2891 Sem = &APFloat::IEEEsingle;
2892 else if (LHSExt->getSrcTy()->isDoubleTy())
2893 Sem = &APFloat::IEEEdouble;
2894 else if (LHSExt->getSrcTy()->isFP128Ty())
2895 Sem = &APFloat::IEEEquad;
2896 else if (LHSExt->getSrcTy()->isX86_FP80Ty())
2897 Sem = &APFloat::x87DoubleExtended;
2902 APFloat F = RHSF->getValueAPF();
2903 F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy);
2905 // Avoid lossy conversions and denormals. Zero is a special case
2906 // that's OK to convert.
2910 ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) !=
2911 APFloat::cmpLessThan) || Fabs.isZero()))
2913 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
2914 ConstantFP::get(RHSC->getContext(), F));
2917 case Instruction::PHI:
2918 // Only fold fcmp into the PHI if the phi and fcmp are in the same
2919 // block. If in the same block, we're encouraging jump threading. If
2920 // not, we are just pessimizing the code by making an i1 phi.
2921 if (LHSI->getParent() == I.getParent())
2922 if (Instruction *NV = FoldOpIntoPhi(I))
2925 case Instruction::SIToFP:
2926 case Instruction::UIToFP:
2927 if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC))
2930 case Instruction::Select: {
2931 // If either operand of the select is a constant, we can fold the
2932 // comparison into the select arms, which will cause one to be
2933 // constant folded and the select turned into a bitwise or.
2934 Value *Op1 = 0, *Op2 = 0;
2935 if (LHSI->hasOneUse()) {
2936 if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) {
2937 // Fold the known value into the constant operand.
2938 Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
2939 // Insert a new FCmp of the other select operand.
2940 Op2 = Builder->CreateFCmp(I.getPredicate(),
2941 LHSI->getOperand(2), RHSC, I.getName());
2942 } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) {
2943 // Fold the known value into the constant operand.
2944 Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC);
2945 // Insert a new FCmp of the other select operand.
2946 Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1),
2952 return SelectInst::Create(LHSI->getOperand(0), Op1, Op2);
2955 case Instruction::FSub: {
2956 // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C
2958 if (match(LHSI, m_FNeg(m_Value(Op))))
2959 return new FCmpInst(I.getSwappedPredicate(), Op,
2960 ConstantExpr::getFNeg(RHSC));
2963 case Instruction::Load:
2964 if (GetElementPtrInst *GEP =
2965 dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) {
2966 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0)))
2967 if (GV->isConstant() && GV->hasDefinitiveInitializer() &&
2968 !cast<LoadInst>(LHSI)->isVolatile())
2969 if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I))
2976 // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y
2978 if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
2979 return new FCmpInst(I.getSwappedPredicate(), X, Y);
2981 // fcmp (fpext x), (fpext y) -> fcmp x, y
2982 if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0))
2983 if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1))
2984 if (LHSExt->getSrcTy() == RHSExt->getSrcTy())
2985 return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0),
2986 RHSExt->getOperand(0));
2988 return Changed ? &I : 0;