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Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 4099 |
1 files changed, 4099 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp new file mode 100644 index 0000000..2dafa58 --- /dev/null +++ b/contrib/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -0,0 +1,4099 @@ +//===- InstCombineCompares.cpp --------------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the visitICmp and visitFCmp functions. +// +//===----------------------------------------------------------------------===// + +#include "InstCombineInternal.h" +#include "llvm/ADT/APSInt.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/IR/ConstantRange.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/GetElementPtrTypeIterator.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Analysis/TargetLibraryInfo.h" + +using namespace llvm; +using namespace PatternMatch; + +#define DEBUG_TYPE "instcombine" + +// How many times is a select replaced by one of its operands? +STATISTIC(NumSel, "Number of select opts"); + +// Initialization Routines + +static ConstantInt *getOne(Constant *C) { + return ConstantInt::get(cast<IntegerType>(C->getType()), 1); +} + +static ConstantInt *ExtractElement(Constant *V, Constant *Idx) { + return cast<ConstantInt>(ConstantExpr::getExtractElement(V, Idx)); +} + +static bool HasAddOverflow(ConstantInt *Result, + ConstantInt *In1, ConstantInt *In2, + bool IsSigned) { + if (!IsSigned) + return Result->getValue().ult(In1->getValue()); + + if (In2->isNegative()) + return Result->getValue().sgt(In1->getValue()); + return Result->getValue().slt(In1->getValue()); +} + +/// AddWithOverflow - Compute Result = In1+In2, returning true if the result +/// overflowed for this type. +static bool AddWithOverflow(Constant *&Result, Constant *In1, + Constant *In2, bool IsSigned = false) { + Result = ConstantExpr::getAdd(In1, In2); + + if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { + for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { + Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); + if (HasAddOverflow(ExtractElement(Result, Idx), + ExtractElement(In1, Idx), + ExtractElement(In2, Idx), + IsSigned)) + return true; + } + return false; + } + + return HasAddOverflow(cast<ConstantInt>(Result), + cast<ConstantInt>(In1), cast<ConstantInt>(In2), + IsSigned); +} + +static bool HasSubOverflow(ConstantInt *Result, + ConstantInt *In1, ConstantInt *In2, + bool IsSigned) { + if (!IsSigned) + return Result->getValue().ugt(In1->getValue()); + + if (In2->isNegative()) + return Result->getValue().slt(In1->getValue()); + + return Result->getValue().sgt(In1->getValue()); +} + +/// SubWithOverflow - Compute Result = In1-In2, returning true if the result +/// overflowed for this type. +static bool SubWithOverflow(Constant *&Result, Constant *In1, + Constant *In2, bool IsSigned = false) { + Result = ConstantExpr::getSub(In1, In2); + + if (VectorType *VTy = dyn_cast<VectorType>(In1->getType())) { + for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { + Constant *Idx = ConstantInt::get(Type::getInt32Ty(In1->getContext()), i); + if (HasSubOverflow(ExtractElement(Result, Idx), + ExtractElement(In1, Idx), + ExtractElement(In2, Idx), + IsSigned)) + return true; + } + return false; + } + + return HasSubOverflow(cast<ConstantInt>(Result), + cast<ConstantInt>(In1), cast<ConstantInt>(In2), + IsSigned); +} + +/// isSignBitCheck - Given an exploded icmp instruction, return true if the +/// comparison only checks the sign bit. If it only checks the sign bit, set +/// TrueIfSigned if the result of the comparison is true when the input value is +/// signed. +static bool isSignBitCheck(ICmpInst::Predicate pred, ConstantInt *RHS, + bool &TrueIfSigned) { + switch (pred) { + case ICmpInst::ICMP_SLT: // True if LHS s< 0 + TrueIfSigned = true; + return RHS->isZero(); + case ICmpInst::ICMP_SLE: // True if LHS s<= RHS and RHS == -1 + TrueIfSigned = true; + return RHS->isAllOnesValue(); + case ICmpInst::ICMP_SGT: // True if LHS s> -1 + TrueIfSigned = false; + return RHS->isAllOnesValue(); + case ICmpInst::ICMP_UGT: + // True if LHS u> RHS and RHS == high-bit-mask - 1 + TrueIfSigned = true; + return RHS->isMaxValue(true); + case ICmpInst::ICMP_UGE: + // True if LHS u>= RHS and RHS == high-bit-mask (2^7, 2^15, 2^31, etc) + TrueIfSigned = true; + return RHS->getValue().isSignBit(); + default: + return false; + } +} + +/// Returns true if the exploded icmp can be expressed as a signed comparison +/// to zero and updates the predicate accordingly. +/// The signedness of the comparison is preserved. +static bool isSignTest(ICmpInst::Predicate &pred, const ConstantInt *RHS) { + if (!ICmpInst::isSigned(pred)) + return false; + + if (RHS->isZero()) + return ICmpInst::isRelational(pred); + + if (RHS->isOne()) { + if (pred == ICmpInst::ICMP_SLT) { + pred = ICmpInst::ICMP_SLE; + return true; + } + } else if (RHS->isAllOnesValue()) { + if (pred == ICmpInst::ICMP_SGT) { + pred = ICmpInst::ICMP_SGE; + return true; + } + } + + return false; +} + +// isHighOnes - Return true if the constant is of the form 1+0+. +// This is the same as lowones(~X). +static bool isHighOnes(const ConstantInt *CI) { + return (~CI->getValue() + 1).isPowerOf2(); +} + +/// ComputeSignedMinMaxValuesFromKnownBits - Given a signed integer type and a +/// set of known zero and one bits, compute the maximum and minimum values that +/// could have the specified known zero and known one bits, returning them in +/// min/max. +static void ComputeSignedMinMaxValuesFromKnownBits(const APInt& KnownZero, + const APInt& KnownOne, + APInt& Min, APInt& Max) { + assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && + KnownZero.getBitWidth() == Min.getBitWidth() && + KnownZero.getBitWidth() == Max.getBitWidth() && + "KnownZero, KnownOne and Min, Max must have equal bitwidth."); + APInt UnknownBits = ~(KnownZero|KnownOne); + + // The minimum value is when all unknown bits are zeros, EXCEPT for the sign + // bit if it is unknown. + Min = KnownOne; + Max = KnownOne|UnknownBits; + + if (UnknownBits.isNegative()) { // Sign bit is unknown + Min.setBit(Min.getBitWidth()-1); + Max.clearBit(Max.getBitWidth()-1); + } +} + +// ComputeUnsignedMinMaxValuesFromKnownBits - Given an unsigned integer type and +// a set of known zero and one bits, compute the maximum and minimum values that +// could have the specified known zero and known one bits, returning them in +// min/max. +static void ComputeUnsignedMinMaxValuesFromKnownBits(const APInt &KnownZero, + const APInt &KnownOne, + APInt &Min, APInt &Max) { + assert(KnownZero.getBitWidth() == KnownOne.getBitWidth() && + KnownZero.getBitWidth() == Min.getBitWidth() && + KnownZero.getBitWidth() == Max.getBitWidth() && + "Ty, KnownZero, KnownOne and Min, Max must have equal bitwidth."); + APInt UnknownBits = ~(KnownZero|KnownOne); + + // The minimum value is when the unknown bits are all zeros. + Min = KnownOne; + // The maximum value is when the unknown bits are all ones. + Max = KnownOne|UnknownBits; +} + + + +/// FoldCmpLoadFromIndexedGlobal - Called we see this pattern: +/// cmp pred (load (gep GV, ...)), cmpcst +/// where GV is a global variable with a constant initializer. Try to simplify +/// this into some simple computation that does not need the load. For example +/// we can optimize "icmp eq (load (gep "foo", 0, i)), 0" into "icmp eq i, 3". +/// +/// If AndCst is non-null, then the loaded value is masked with that constant +/// before doing the comparison. This handles cases like "A[i]&4 == 0". +Instruction *InstCombiner:: +FoldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP, GlobalVariable *GV, + CmpInst &ICI, ConstantInt *AndCst) { + Constant *Init = GV->getInitializer(); + if (!isa<ConstantArray>(Init) && !isa<ConstantDataArray>(Init)) + return nullptr; + + uint64_t ArrayElementCount = Init->getType()->getArrayNumElements(); + if (ArrayElementCount > 1024) return nullptr; // Don't blow up on huge arrays. + + // There are many forms of this optimization we can handle, for now, just do + // the simple index into a single-dimensional array. + // + // Require: GEP GV, 0, i {{, constant indices}} + if (GEP->getNumOperands() < 3 || + !isa<ConstantInt>(GEP->getOperand(1)) || + !cast<ConstantInt>(GEP->getOperand(1))->isZero() || + isa<Constant>(GEP->getOperand(2))) + return nullptr; + + // Check that indices after the variable are constants and in-range for the + // type they index. Collect the indices. This is typically for arrays of + // structs. + SmallVector<unsigned, 4> LaterIndices; + + Type *EltTy = Init->getType()->getArrayElementType(); + for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) { + ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i)); + if (!Idx) return nullptr; // Variable index. + + uint64_t IdxVal = Idx->getZExtValue(); + if ((unsigned)IdxVal != IdxVal) return nullptr; // Too large array index. + + if (StructType *STy = dyn_cast<StructType>(EltTy)) + EltTy = STy->getElementType(IdxVal); + else if (ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) { + if (IdxVal >= ATy->getNumElements()) return nullptr; + EltTy = ATy->getElementType(); + } else { + return nullptr; // Unknown type. + } + + LaterIndices.push_back(IdxVal); + } + + enum { Overdefined = -3, Undefined = -2 }; + + // Variables for our state machines. + + // FirstTrueElement/SecondTrueElement - Used to emit a comparison of the form + // "i == 47 | i == 87", where 47 is the first index the condition is true for, + // and 87 is the second (and last) index. FirstTrueElement is -2 when + // undefined, otherwise set to the first true element. SecondTrueElement is + // -2 when undefined, -3 when overdefined and >= 0 when that index is true. + int FirstTrueElement = Undefined, SecondTrueElement = Undefined; + + // FirstFalseElement/SecondFalseElement - Used to emit a comparison of the + // form "i != 47 & i != 87". Same state transitions as for true elements. + int FirstFalseElement = Undefined, SecondFalseElement = Undefined; + + /// TrueRangeEnd/FalseRangeEnd - In conjunction with First*Element, these + /// define a state machine that triggers for ranges of values that the index + /// is true or false for. This triggers on things like "abbbbc"[i] == 'b'. + /// This is -2 when undefined, -3 when overdefined, and otherwise the last + /// index in the range (inclusive). We use -2 for undefined here because we + /// use relative comparisons and don't want 0-1 to match -1. + int TrueRangeEnd = Undefined, FalseRangeEnd = Undefined; + + // MagicBitvector - This is a magic bitvector where we set a bit if the + // comparison is true for element 'i'. If there are 64 elements or less in + // the array, this will fully represent all the comparison results. + uint64_t MagicBitvector = 0; + + // Scan the array and see if one of our patterns matches. + Constant *CompareRHS = cast<Constant>(ICI.getOperand(1)); + for (unsigned i = 0, e = ArrayElementCount; i != e; ++i) { + Constant *Elt = Init->getAggregateElement(i); + if (!Elt) return nullptr; + + // If this is indexing an array of structures, get the structure element. + if (!LaterIndices.empty()) + Elt = ConstantExpr::getExtractValue(Elt, LaterIndices); + + // If the element is masked, handle it. + if (AndCst) Elt = ConstantExpr::getAnd(Elt, AndCst); + + // Find out if the comparison would be true or false for the i'th element. + Constant *C = ConstantFoldCompareInstOperands(ICI.getPredicate(), Elt, + CompareRHS, DL, TLI); + // If the result is undef for this element, ignore it. + if (isa<UndefValue>(C)) { + // Extend range state machines to cover this element in case there is an + // undef in the middle of the range. + if (TrueRangeEnd == (int)i-1) + TrueRangeEnd = i; + if (FalseRangeEnd == (int)i-1) + FalseRangeEnd = i; + continue; + } + + // If we can't compute the result for any of the elements, we have to give + // up evaluating the entire conditional. + if (!isa<ConstantInt>(C)) return nullptr; + + // Otherwise, we know if the comparison is true or false for this element, + // update our state machines. + bool IsTrueForElt = !cast<ConstantInt>(C)->isZero(); + + // State machine for single/double/range index comparison. + if (IsTrueForElt) { + // Update the TrueElement state machine. + if (FirstTrueElement == Undefined) + FirstTrueElement = TrueRangeEnd = i; // First true element. + else { + // Update double-compare state machine. + if (SecondTrueElement == Undefined) + SecondTrueElement = i; + else + SecondTrueElement = Overdefined; + + // Update range state machine. + if (TrueRangeEnd == (int)i-1) + TrueRangeEnd = i; + else + TrueRangeEnd = Overdefined; + } + } else { + // Update the FalseElement state machine. + if (FirstFalseElement == Undefined) + FirstFalseElement = FalseRangeEnd = i; // First false element. + else { + // Update double-compare state machine. + if (SecondFalseElement == Undefined) + SecondFalseElement = i; + else + SecondFalseElement = Overdefined; + + // Update range state machine. + if (FalseRangeEnd == (int)i-1) + FalseRangeEnd = i; + else + FalseRangeEnd = Overdefined; + } + } + + + // If this element is in range, update our magic bitvector. + if (i < 64 && IsTrueForElt) + MagicBitvector |= 1ULL << i; + + // If all of our states become overdefined, bail out early. Since the + // predicate is expensive, only check it every 8 elements. This is only + // really useful for really huge arrays. + if ((i & 8) == 0 && i >= 64 && SecondTrueElement == Overdefined && + SecondFalseElement == Overdefined && TrueRangeEnd == Overdefined && + FalseRangeEnd == Overdefined) + return nullptr; + } + + // Now that we've scanned the entire array, emit our new comparison(s). We + // order the state machines in complexity of the generated code. + Value *Idx = GEP->getOperand(2); + + // If the index is larger than the pointer size of the target, truncate the + // index down like the GEP would do implicitly. We don't have to do this for + // an inbounds GEP because the index can't be out of range. + if (!GEP->isInBounds()) { + Type *IntPtrTy = DL.getIntPtrType(GEP->getType()); + unsigned PtrSize = IntPtrTy->getIntegerBitWidth(); + if (Idx->getType()->getPrimitiveSizeInBits() > PtrSize) + Idx = Builder->CreateTrunc(Idx, IntPtrTy); + } + + // If the comparison is only true for one or two elements, emit direct + // comparisons. + if (SecondTrueElement != Overdefined) { + // None true -> false. + if (FirstTrueElement == Undefined) + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + + Value *FirstTrueIdx = ConstantInt::get(Idx->getType(), FirstTrueElement); + + // True for one element -> 'i == 47'. + if (SecondTrueElement == Undefined) + return new ICmpInst(ICmpInst::ICMP_EQ, Idx, FirstTrueIdx); + + // True for two elements -> 'i == 47 | i == 72'. + Value *C1 = Builder->CreateICmpEQ(Idx, FirstTrueIdx); + Value *SecondTrueIdx = ConstantInt::get(Idx->getType(), SecondTrueElement); + Value *C2 = Builder->CreateICmpEQ(Idx, SecondTrueIdx); + return BinaryOperator::CreateOr(C1, C2); + } + + // If the comparison is only false for one or two elements, emit direct + // comparisons. + if (SecondFalseElement != Overdefined) { + // None false -> true. + if (FirstFalseElement == Undefined) + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + + Value *FirstFalseIdx = ConstantInt::get(Idx->getType(), FirstFalseElement); + + // False for one element -> 'i != 47'. + if (SecondFalseElement == Undefined) + return new ICmpInst(ICmpInst::ICMP_NE, Idx, FirstFalseIdx); + + // False for two elements -> 'i != 47 & i != 72'. + Value *C1 = Builder->CreateICmpNE(Idx, FirstFalseIdx); + Value *SecondFalseIdx = ConstantInt::get(Idx->getType(),SecondFalseElement); + Value *C2 = Builder->CreateICmpNE(Idx, SecondFalseIdx); + return BinaryOperator::CreateAnd(C1, C2); + } + + // If the comparison can be replaced with a range comparison for the elements + // where it is true, emit the range check. + if (TrueRangeEnd != Overdefined) { + assert(TrueRangeEnd != FirstTrueElement && "Should emit single compare"); + + // Generate (i-FirstTrue) <u (TrueRangeEnd-FirstTrue+1). + if (FirstTrueElement) { + Value *Offs = ConstantInt::get(Idx->getType(), -FirstTrueElement); + Idx = Builder->CreateAdd(Idx, Offs); + } + + Value *End = ConstantInt::get(Idx->getType(), + TrueRangeEnd-FirstTrueElement+1); + return new ICmpInst(ICmpInst::ICMP_ULT, Idx, End); + } + + // False range check. + if (FalseRangeEnd != Overdefined) { + assert(FalseRangeEnd != FirstFalseElement && "Should emit single compare"); + // Generate (i-FirstFalse) >u (FalseRangeEnd-FirstFalse). + if (FirstFalseElement) { + Value *Offs = ConstantInt::get(Idx->getType(), -FirstFalseElement); + Idx = Builder->CreateAdd(Idx, Offs); + } + + Value *End = ConstantInt::get(Idx->getType(), + FalseRangeEnd-FirstFalseElement); + return new ICmpInst(ICmpInst::ICMP_UGT, Idx, End); + } + + + // If a magic bitvector captures the entire comparison state + // of this load, replace it with computation that does: + // ((magic_cst >> i) & 1) != 0 + { + Type *Ty = nullptr; + + // Look for an appropriate type: + // - The type of Idx if the magic fits + // - The smallest fitting legal type if we have a DataLayout + // - Default to i32 + if (ArrayElementCount <= Idx->getType()->getIntegerBitWidth()) + Ty = Idx->getType(); + else + Ty = DL.getSmallestLegalIntType(Init->getContext(), ArrayElementCount); + + if (Ty) { + Value *V = Builder->CreateIntCast(Idx, Ty, false); + V = Builder->CreateLShr(ConstantInt::get(Ty, MagicBitvector), V); + V = Builder->CreateAnd(ConstantInt::get(Ty, 1), V); + return new ICmpInst(ICmpInst::ICMP_NE, V, ConstantInt::get(Ty, 0)); + } + } + + return nullptr; +} + + +/// EvaluateGEPOffsetExpression - Return a value that can be used to compare +/// the *offset* implied by a GEP to zero. For example, if we have &A[i], we +/// want to return 'i' for "icmp ne i, 0". Note that, in general, indices can +/// be complex, and scales are involved. The above expression would also be +/// legal to codegen as "icmp ne (i*4), 0" (assuming A is a pointer to i32). +/// This later form is less amenable to optimization though, and we are allowed +/// to generate the first by knowing that pointer arithmetic doesn't overflow. +/// +/// If we can't emit an optimized form for this expression, this returns null. +/// +static Value *EvaluateGEPOffsetExpression(User *GEP, InstCombiner &IC, + const DataLayout &DL) { + gep_type_iterator GTI = gep_type_begin(GEP); + + // Check to see if this gep only has a single variable index. If so, and if + // any constant indices are a multiple of its scale, then we can compute this + // in terms of the scale of the variable index. For example, if the GEP + // implies an offset of "12 + i*4", then we can codegen this as "3 + i", + // because the expression will cross zero at the same point. + unsigned i, e = GEP->getNumOperands(); + int64_t Offset = 0; + for (i = 1; i != e; ++i, ++GTI) { + if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) { + // Compute the aggregate offset of constant indices. + if (CI->isZero()) continue; + + // Handle a struct index, which adds its field offset to the pointer. + if (StructType *STy = dyn_cast<StructType>(*GTI)) { + Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); + } else { + uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()); + Offset += Size*CI->getSExtValue(); + } + } else { + // Found our variable index. + break; + } + } + + // If there are no variable indices, we must have a constant offset, just + // evaluate it the general way. + if (i == e) return nullptr; + + Value *VariableIdx = GEP->getOperand(i); + // Determine the scale factor of the variable element. For example, this is + // 4 if the variable index is into an array of i32. + uint64_t VariableScale = DL.getTypeAllocSize(GTI.getIndexedType()); + + // Verify that there are no other variable indices. If so, emit the hard way. + for (++i, ++GTI; i != e; ++i, ++GTI) { + ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i)); + if (!CI) return nullptr; + + // Compute the aggregate offset of constant indices. + if (CI->isZero()) continue; + + // Handle a struct index, which adds its field offset to the pointer. + if (StructType *STy = dyn_cast<StructType>(*GTI)) { + Offset += DL.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); + } else { + uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()); + Offset += Size*CI->getSExtValue(); + } + } + + + + // Okay, we know we have a single variable index, which must be a + // pointer/array/vector index. If there is no offset, life is simple, return + // the index. + Type *IntPtrTy = DL.getIntPtrType(GEP->getOperand(0)->getType()); + unsigned IntPtrWidth = IntPtrTy->getIntegerBitWidth(); + if (Offset == 0) { + // Cast to intptrty in case a truncation occurs. If an extension is needed, + // we don't need to bother extending: the extension won't affect where the + // computation crosses zero. + if (VariableIdx->getType()->getPrimitiveSizeInBits() > IntPtrWidth) { + VariableIdx = IC.Builder->CreateTrunc(VariableIdx, IntPtrTy); + } + return VariableIdx; + } + + // Otherwise, there is an index. The computation we will do will be modulo + // the pointer size, so get it. + uint64_t PtrSizeMask = ~0ULL >> (64-IntPtrWidth); + + Offset &= PtrSizeMask; + VariableScale &= PtrSizeMask; + + // To do this transformation, any constant index must be a multiple of the + // variable scale factor. For example, we can evaluate "12 + 4*i" as "3 + i", + // but we can't evaluate "10 + 3*i" in terms of i. Check that the offset is a + // multiple of the variable scale. + int64_t NewOffs = Offset / (int64_t)VariableScale; + if (Offset != NewOffs*(int64_t)VariableScale) + return nullptr; + + // Okay, we can do this evaluation. Start by converting the index to intptr. + if (VariableIdx->getType() != IntPtrTy) + VariableIdx = IC.Builder->CreateIntCast(VariableIdx, IntPtrTy, + true /*Signed*/); + Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs); + return IC.Builder->CreateAdd(VariableIdx, OffsetVal, "offset"); +} + +/// FoldGEPICmp - Fold comparisons between a GEP instruction and something +/// else. At this point we know that the GEP is on the LHS of the comparison. +Instruction *InstCombiner::FoldGEPICmp(GEPOperator *GEPLHS, Value *RHS, + ICmpInst::Predicate Cond, + Instruction &I) { + // Don't transform signed compares of GEPs into index compares. Even if the + // GEP is inbounds, the final add of the base pointer can have signed overflow + // and would change the result of the icmp. + // e.g. "&foo[0] <s &foo[1]" can't be folded to "true" because "foo" could be + // the maximum signed value for the pointer type. + if (ICmpInst::isSigned(Cond)) + return nullptr; + + // Look through bitcasts and addrspacecasts. We do not however want to remove + // 0 GEPs. + if (!isa<GetElementPtrInst>(RHS)) + RHS = RHS->stripPointerCasts(); + + Value *PtrBase = GEPLHS->getOperand(0); + if (PtrBase == RHS && GEPLHS->isInBounds()) { + // ((gep Ptr, OFFSET) cmp Ptr) ---> (OFFSET cmp 0). + // This transformation (ignoring the base and scales) is valid because we + // know pointers can't overflow since the gep is inbounds. See if we can + // output an optimized form. + Value *Offset = EvaluateGEPOffsetExpression(GEPLHS, *this, DL); + + // If not, synthesize the offset the hard way. + if (!Offset) + Offset = EmitGEPOffset(GEPLHS); + return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Offset, + Constant::getNullValue(Offset->getType())); + } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) { + // If the base pointers are different, but the indices are the same, just + // compare the base pointer. + if (PtrBase != GEPRHS->getOperand(0)) { + bool IndicesTheSame = GEPLHS->getNumOperands()==GEPRHS->getNumOperands(); + IndicesTheSame &= GEPLHS->getOperand(0)->getType() == + GEPRHS->getOperand(0)->getType(); + if (IndicesTheSame) + for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) + if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { + IndicesTheSame = false; + break; + } + + // If all indices are the same, just compare the base pointers. + if (IndicesTheSame) + return new ICmpInst(Cond, GEPLHS->getOperand(0), GEPRHS->getOperand(0)); + + // If we're comparing GEPs with two base pointers that only differ in type + // and both GEPs have only constant indices or just one use, then fold + // the compare with the adjusted indices. + if (GEPLHS->isInBounds() && GEPRHS->isInBounds() && + (GEPLHS->hasAllConstantIndices() || GEPLHS->hasOneUse()) && + (GEPRHS->hasAllConstantIndices() || GEPRHS->hasOneUse()) && + PtrBase->stripPointerCasts() == + GEPRHS->getOperand(0)->stripPointerCasts()) { + Value *LOffset = EmitGEPOffset(GEPLHS); + Value *ROffset = EmitGEPOffset(GEPRHS); + + // If we looked through an addrspacecast between different sized address + // spaces, the LHS and RHS pointers are different sized + // integers. Truncate to the smaller one. + Type *LHSIndexTy = LOffset->getType(); + Type *RHSIndexTy = ROffset->getType(); + if (LHSIndexTy != RHSIndexTy) { + if (LHSIndexTy->getPrimitiveSizeInBits() < + RHSIndexTy->getPrimitiveSizeInBits()) { + ROffset = Builder->CreateTrunc(ROffset, LHSIndexTy); + } else + LOffset = Builder->CreateTrunc(LOffset, RHSIndexTy); + } + + Value *Cmp = Builder->CreateICmp(ICmpInst::getSignedPredicate(Cond), + LOffset, ROffset); + return ReplaceInstUsesWith(I, Cmp); + } + + // Otherwise, the base pointers are different and the indices are + // different, bail out. + return nullptr; + } + + // If one of the GEPs has all zero indices, recurse. + if (GEPLHS->hasAllZeroIndices()) + return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0), + ICmpInst::getSwappedPredicate(Cond), I); + + // If the other GEP has all zero indices, recurse. + if (GEPRHS->hasAllZeroIndices()) + return FoldGEPICmp(GEPLHS, GEPRHS->getOperand(0), Cond, I); + + bool GEPsInBounds = GEPLHS->isInBounds() && GEPRHS->isInBounds(); + if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands()) { + // If the GEPs only differ by one index, compare it. + unsigned NumDifferences = 0; // Keep track of # differences. + unsigned DiffOperand = 0; // The operand that differs. + for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) + if (GEPLHS->getOperand(i) != GEPRHS->getOperand(i)) { + if (GEPLHS->getOperand(i)->getType()->getPrimitiveSizeInBits() != + GEPRHS->getOperand(i)->getType()->getPrimitiveSizeInBits()) { + // Irreconcilable differences. + NumDifferences = 2; + break; + } else { + if (NumDifferences++) break; + DiffOperand = i; + } + } + + if (NumDifferences == 0) // SAME GEP? + return ReplaceInstUsesWith(I, // No comparison is needed here. + Builder->getInt1(ICmpInst::isTrueWhenEqual(Cond))); + + else if (NumDifferences == 1 && GEPsInBounds) { + Value *LHSV = GEPLHS->getOperand(DiffOperand); + Value *RHSV = GEPRHS->getOperand(DiffOperand); + // Make sure we do a signed comparison here. + return new ICmpInst(ICmpInst::getSignedPredicate(Cond), LHSV, RHSV); + } + } + + // Only lower this if the icmp is the only user of the GEP or if we expect + // the result to fold to a constant! + if (GEPsInBounds && (isa<ConstantExpr>(GEPLHS) || GEPLHS->hasOneUse()) && + (isa<ConstantExpr>(GEPRHS) || GEPRHS->hasOneUse())) { + // ((gep Ptr, OFFSET1) cmp (gep Ptr, OFFSET2) ---> (OFFSET1 cmp OFFSET2) + Value *L = EmitGEPOffset(GEPLHS); + Value *R = EmitGEPOffset(GEPRHS); + return new ICmpInst(ICmpInst::getSignedPredicate(Cond), L, R); + } + } + return nullptr; +} + +/// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X". +Instruction *InstCombiner::FoldICmpAddOpCst(Instruction &ICI, + Value *X, ConstantInt *CI, + ICmpInst::Predicate Pred) { + // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0, + // so the values can never be equal. Similarly for all other "or equals" + // operators. + + // (X+1) <u X --> X >u (MAXUINT-1) --> X == 255 + // (X+2) <u X --> X >u (MAXUINT-2) --> X > 253 + // (X+MAXUINT) <u X --> X >u (MAXUINT-MAXUINT) --> X != 0 + if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) { + Value *R = + ConstantExpr::getSub(ConstantInt::getAllOnesValue(CI->getType()), CI); + return new ICmpInst(ICmpInst::ICMP_UGT, X, R); + } + + // (X+1) >u X --> X <u (0-1) --> X != 255 + // (X+2) >u X --> X <u (0-2) --> X <u 254 + // (X+MAXUINT) >u X --> X <u (0-MAXUINT) --> X <u 1 --> X == 0 + if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) + return new ICmpInst(ICmpInst::ICMP_ULT, X, ConstantExpr::getNeg(CI)); + + unsigned BitWidth = CI->getType()->getPrimitiveSizeInBits(); + ConstantInt *SMax = ConstantInt::get(X->getContext(), + APInt::getSignedMaxValue(BitWidth)); + + // (X+ 1) <s X --> X >s (MAXSINT-1) --> X == 127 + // (X+ 2) <s X --> X >s (MAXSINT-2) --> X >s 125 + // (X+MAXSINT) <s X --> X >s (MAXSINT-MAXSINT) --> X >s 0 + // (X+MINSINT) <s X --> X >s (MAXSINT-MINSINT) --> X >s -1 + // (X+ -2) <s X --> X >s (MAXSINT- -2) --> X >s 126 + // (X+ -1) <s X --> X >s (MAXSINT- -1) --> X != 127 + if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) + return new ICmpInst(ICmpInst::ICMP_SGT, X, ConstantExpr::getSub(SMax, CI)); + + // (X+ 1) >s X --> X <s (MAXSINT-(1-1)) --> X != 127 + // (X+ 2) >s X --> X <s (MAXSINT-(2-1)) --> X <s 126 + // (X+MAXSINT) >s X --> X <s (MAXSINT-(MAXSINT-1)) --> X <s 1 + // (X+MINSINT) >s X --> X <s (MAXSINT-(MINSINT-1)) --> X <s -2 + // (X+ -2) >s X --> X <s (MAXSINT-(-2-1)) --> X <s -126 + // (X+ -1) >s X --> X <s (MAXSINT-(-1-1)) --> X == -128 + + assert(Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE); + Constant *C = Builder->getInt(CI->getValue()-1); + return new ICmpInst(ICmpInst::ICMP_SLT, X, ConstantExpr::getSub(SMax, C)); +} + +/// FoldICmpDivCst - Fold "icmp pred, ([su]div X, DivRHS), CmpRHS" where DivRHS +/// and CmpRHS are both known to be integer constants. +Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI, + ConstantInt *DivRHS) { + ConstantInt *CmpRHS = cast<ConstantInt>(ICI.getOperand(1)); + const APInt &CmpRHSV = CmpRHS->getValue(); + + // FIXME: If the operand types don't match the type of the divide + // then don't attempt this transform. The code below doesn't have the + // logic to deal with a signed divide and an unsigned compare (and + // vice versa). This is because (x /s C1) <s C2 produces different + // results than (x /s C1) <u C2 or (x /u C1) <s C2 or even + // (x /u C1) <u C2. Simply casting the operands and result won't + // work. :( The if statement below tests that condition and bails + // if it finds it. + bool DivIsSigned = DivI->getOpcode() == Instruction::SDiv; + if (!ICI.isEquality() && DivIsSigned != ICI.isSigned()) + return nullptr; + if (DivRHS->isZero()) + return nullptr; // The ProdOV computation fails on divide by zero. + if (DivIsSigned && DivRHS->isAllOnesValue()) + return nullptr; // The overflow computation also screws up here + if (DivRHS->isOne()) { + // This eliminates some funny cases with INT_MIN. + ICI.setOperand(0, DivI->getOperand(0)); // X/1 == X. + return &ICI; + } + + // Compute Prod = CI * DivRHS. We are essentially solving an equation + // of form X/C1=C2. We solve for X by multiplying C1 (DivRHS) and + // C2 (CI). By solving for X we can turn this into a range check + // instead of computing a divide. + Constant *Prod = ConstantExpr::getMul(CmpRHS, DivRHS); + + // Determine if the product overflows by seeing if the product is + // not equal to the divide. Make sure we do the same kind of divide + // as in the LHS instruction that we're folding. + bool ProdOV = (DivIsSigned ? ConstantExpr::getSDiv(Prod, DivRHS) : + ConstantExpr::getUDiv(Prod, DivRHS)) != CmpRHS; + + // Get the ICmp opcode + ICmpInst::Predicate Pred = ICI.getPredicate(); + + /// If the division is known to be exact, then there is no remainder from the + /// divide, so the covered range size is unit, otherwise it is the divisor. + ConstantInt *RangeSize = DivI->isExact() ? getOne(Prod) : DivRHS; + + // Figure out the interval that is being checked. For example, a comparison + // like "X /u 5 == 0" is really checking that X is in the interval [0, 5). + // Compute this interval based on the constants involved and the signedness of + // the compare/divide. This computes a half-open interval, keeping track of + // whether either value in the interval overflows. After analysis each + // overflow variable is set to 0 if it's corresponding bound variable is valid + // -1 if overflowed off the bottom end, or +1 if overflowed off the top end. + int LoOverflow = 0, HiOverflow = 0; + Constant *LoBound = nullptr, *HiBound = nullptr; + + if (!DivIsSigned) { // udiv + // e.g. X/5 op 3 --> [15, 20) + LoBound = Prod; + HiOverflow = LoOverflow = ProdOV; + if (!HiOverflow) { + // If this is not an exact divide, then many values in the range collapse + // to the same result value. + HiOverflow = AddWithOverflow(HiBound, LoBound, RangeSize, false); + } + + } else if (DivRHS->getValue().isStrictlyPositive()) { // Divisor is > 0. + if (CmpRHSV == 0) { // (X / pos) op 0 + // Can't overflow. e.g. X/2 op 0 --> [-1, 2) + LoBound = ConstantExpr::getNeg(SubOne(RangeSize)); + HiBound = RangeSize; + } else if (CmpRHSV.isStrictlyPositive()) { // (X / pos) op pos + LoBound = Prod; // e.g. X/5 op 3 --> [15, 20) + HiOverflow = LoOverflow = ProdOV; + if (!HiOverflow) + HiOverflow = AddWithOverflow(HiBound, Prod, RangeSize, true); + } else { // (X / pos) op neg + // e.g. X/5 op -3 --> [-15-4, -15+1) --> [-19, -14) + HiBound = AddOne(Prod); + LoOverflow = HiOverflow = ProdOV ? -1 : 0; + if (!LoOverflow) { + ConstantInt *DivNeg =cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); + LoOverflow = AddWithOverflow(LoBound, HiBound, DivNeg, true) ? -1 : 0; + } + } + } else if (DivRHS->isNegative()) { // Divisor is < 0. + if (DivI->isExact()) + RangeSize = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); + if (CmpRHSV == 0) { // (X / neg) op 0 + // e.g. X/-5 op 0 --> [-4, 5) + LoBound = AddOne(RangeSize); + HiBound = cast<ConstantInt>(ConstantExpr::getNeg(RangeSize)); + if (HiBound == DivRHS) { // -INTMIN = INTMIN + HiOverflow = 1; // [INTMIN+1, overflow) + HiBound = nullptr; // e.g. X/INTMIN = 0 --> X > INTMIN + } + } else if (CmpRHSV.isStrictlyPositive()) { // (X / neg) op pos + // e.g. X/-5 op 3 --> [-19, -14) + HiBound = AddOne(Prod); + HiOverflow = LoOverflow = ProdOV ? -1 : 0; + if (!LoOverflow) + LoOverflow = AddWithOverflow(LoBound, HiBound, RangeSize, true) ? -1:0; + } else { // (X / neg) op neg + LoBound = Prod; // e.g. X/-5 op -3 --> [15, 20) + LoOverflow = HiOverflow = ProdOV; + if (!HiOverflow) + HiOverflow = SubWithOverflow(HiBound, Prod, RangeSize, true); + } + + // Dividing by a negative swaps the condition. LT <-> GT + Pred = ICmpInst::getSwappedPredicate(Pred); + } + + Value *X = DivI->getOperand(0); + switch (Pred) { + default: llvm_unreachable("Unhandled icmp opcode!"); + case ICmpInst::ICMP_EQ: + if (LoOverflow && HiOverflow) + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + if (HiOverflow) + return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : + ICmpInst::ICMP_UGE, X, LoBound); + if (LoOverflow) + return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : + ICmpInst::ICMP_ULT, X, HiBound); + return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound, + DivIsSigned, true)); + case ICmpInst::ICMP_NE: + if (LoOverflow && HiOverflow) + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + if (HiOverflow) + return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SLT : + ICmpInst::ICMP_ULT, X, LoBound); + if (LoOverflow) + return new ICmpInst(DivIsSigned ? ICmpInst::ICMP_SGE : + ICmpInst::ICMP_UGE, X, HiBound); + return ReplaceInstUsesWith(ICI, InsertRangeTest(X, LoBound, HiBound, + DivIsSigned, false)); + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_SLT: + if (LoOverflow == +1) // Low bound is greater than input range. + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + if (LoOverflow == -1) // Low bound is less than input range. + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + return new ICmpInst(Pred, X, LoBound); + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_SGT: + if (HiOverflow == +1) // High bound greater than input range. + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + if (HiOverflow == -1) // High bound less than input range. + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + if (Pred == ICmpInst::ICMP_UGT) + return new ICmpInst(ICmpInst::ICMP_UGE, X, HiBound); + return new ICmpInst(ICmpInst::ICMP_SGE, X, HiBound); + } +} + +/// FoldICmpShrCst - Handle "icmp(([al]shr X, cst1), cst2)". +Instruction *InstCombiner::FoldICmpShrCst(ICmpInst &ICI, BinaryOperator *Shr, + ConstantInt *ShAmt) { + const APInt &CmpRHSV = cast<ConstantInt>(ICI.getOperand(1))->getValue(); + + // Check that the shift amount is in range. If not, don't perform + // undefined shifts. When the shift is visited it will be + // simplified. + uint32_t TypeBits = CmpRHSV.getBitWidth(); + uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); + if (ShAmtVal >= TypeBits || ShAmtVal == 0) + return nullptr; + + if (!ICI.isEquality()) { + // If we have an unsigned comparison and an ashr, we can't simplify this. + // Similarly for signed comparisons with lshr. + if (ICI.isSigned() != (Shr->getOpcode() == Instruction::AShr)) + return nullptr; + + // Otherwise, all lshr and most exact ashr's are equivalent to a udiv/sdiv + // by a power of 2. Since we already have logic to simplify these, + // transform to div and then simplify the resultant comparison. + if (Shr->getOpcode() == Instruction::AShr && + (!Shr->isExact() || ShAmtVal == TypeBits - 1)) + return nullptr; + + // Revisit the shift (to delete it). + Worklist.Add(Shr); + + Constant *DivCst = + ConstantInt::get(Shr->getType(), APInt::getOneBitSet(TypeBits, ShAmtVal)); + + Value *Tmp = + Shr->getOpcode() == Instruction::AShr ? + Builder->CreateSDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()) : + Builder->CreateUDiv(Shr->getOperand(0), DivCst, "", Shr->isExact()); + + ICI.setOperand(0, Tmp); + + // If the builder folded the binop, just return it. + BinaryOperator *TheDiv = dyn_cast<BinaryOperator>(Tmp); + if (!TheDiv) + return &ICI; + + // Otherwise, fold this div/compare. + assert(TheDiv->getOpcode() == Instruction::SDiv || + TheDiv->getOpcode() == Instruction::UDiv); + + Instruction *Res = FoldICmpDivCst(ICI, TheDiv, cast<ConstantInt>(DivCst)); + assert(Res && "This div/cst should have folded!"); + return Res; + } + + + // If we are comparing against bits always shifted out, the + // comparison cannot succeed. + APInt Comp = CmpRHSV << ShAmtVal; + ConstantInt *ShiftedCmpRHS = Builder->getInt(Comp); + if (Shr->getOpcode() == Instruction::LShr) + Comp = Comp.lshr(ShAmtVal); + else + Comp = Comp.ashr(ShAmtVal); + + if (Comp != CmpRHSV) { // Comparing against a bit that we know is zero. + bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; + Constant *Cst = Builder->getInt1(IsICMP_NE); + return ReplaceInstUsesWith(ICI, Cst); + } + + // Otherwise, check to see if the bits shifted out are known to be zero. + // If so, we can compare against the unshifted value: + // (X & 4) >> 1 == 2 --> (X & 4) == 4. + if (Shr->hasOneUse() && Shr->isExact()) + return new ICmpInst(ICI.getPredicate(), Shr->getOperand(0), ShiftedCmpRHS); + + if (Shr->hasOneUse()) { + // Otherwise strength reduce the shift into an and. + APInt Val(APInt::getHighBitsSet(TypeBits, TypeBits - ShAmtVal)); + Constant *Mask = Builder->getInt(Val); + + Value *And = Builder->CreateAnd(Shr->getOperand(0), + Mask, Shr->getName()+".mask"); + return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS); + } + return nullptr; +} + +/// FoldICmpCstShrCst - Handle "(icmp eq/ne (ashr/lshr const2, A), const1)" -> +/// (icmp eq/ne A, Log2(const2/const1)) -> +/// (icmp eq/ne A, Log2(const2) - Log2(const1)). +Instruction *InstCombiner::FoldICmpCstShrCst(ICmpInst &I, Value *Op, Value *A, + ConstantInt *CI1, + ConstantInt *CI2) { + assert(I.isEquality() && "Cannot fold icmp gt/lt"); + + auto getConstant = [&I, this](bool IsTrue) { + if (I.getPredicate() == I.ICMP_NE) + IsTrue = !IsTrue; + return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), IsTrue)); + }; + + auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) { + if (I.getPredicate() == I.ICMP_NE) + Pred = CmpInst::getInversePredicate(Pred); + return new ICmpInst(Pred, LHS, RHS); + }; + + APInt AP1 = CI1->getValue(); + APInt AP2 = CI2->getValue(); + + // Don't bother doing any work for cases which InstSimplify handles. + if (AP2 == 0) + return nullptr; + bool IsAShr = isa<AShrOperator>(Op); + if (IsAShr) { + if (AP2.isAllOnesValue()) + return nullptr; + if (AP2.isNegative() != AP1.isNegative()) + return nullptr; + if (AP2.sgt(AP1)) + return nullptr; + } + + if (!AP1) + // 'A' must be large enough to shift out the highest set bit. + return getICmp(I.ICMP_UGT, A, + ConstantInt::get(A->getType(), AP2.logBase2())); + + if (AP1 == AP2) + return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType())); + + // Get the distance between the highest bit that's set. + int Shift; + // Both the constants are negative, take their positive to calculate log. + if (IsAShr && AP1.isNegative()) + // Get the ones' complement of AP2 and AP1 when computing the distance. + Shift = (~AP2).logBase2() - (~AP1).logBase2(); + else + Shift = AP2.logBase2() - AP1.logBase2(); + + if (Shift > 0) { + if (IsAShr ? AP1 == AP2.ashr(Shift) : AP1 == AP2.lshr(Shift)) + return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift)); + } + // Shifting const2 will never be equal to const1. + return getConstant(false); +} + +/// FoldICmpCstShlCst - Handle "(icmp eq/ne (shl const2, A), const1)" -> +/// (icmp eq/ne A, TrailingZeros(const1) - TrailingZeros(const2)). +Instruction *InstCombiner::FoldICmpCstShlCst(ICmpInst &I, Value *Op, Value *A, + ConstantInt *CI1, + ConstantInt *CI2) { + assert(I.isEquality() && "Cannot fold icmp gt/lt"); + + auto getConstant = [&I, this](bool IsTrue) { + if (I.getPredicate() == I.ICMP_NE) + IsTrue = !IsTrue; + return ReplaceInstUsesWith(I, ConstantInt::get(I.getType(), IsTrue)); + }; + + auto getICmp = [&I](CmpInst::Predicate Pred, Value *LHS, Value *RHS) { + if (I.getPredicate() == I.ICMP_NE) + Pred = CmpInst::getInversePredicate(Pred); + return new ICmpInst(Pred, LHS, RHS); + }; + + APInt AP1 = CI1->getValue(); + APInt AP2 = CI2->getValue(); + + // Don't bother doing any work for cases which InstSimplify handles. + if (AP2 == 0) + return nullptr; + + unsigned AP2TrailingZeros = AP2.countTrailingZeros(); + + if (!AP1 && AP2TrailingZeros != 0) + return getICmp(I.ICMP_UGE, A, + ConstantInt::get(A->getType(), AP2.getBitWidth() - AP2TrailingZeros)); + + if (AP1 == AP2) + return getICmp(I.ICMP_EQ, A, ConstantInt::getNullValue(A->getType())); + + // Get the distance between the lowest bits that are set. + int Shift = AP1.countTrailingZeros() - AP2TrailingZeros; + + if (Shift > 0 && AP2.shl(Shift) == AP1) + return getICmp(I.ICMP_EQ, A, ConstantInt::get(A->getType(), Shift)); + + // Shifting const2 will never be equal to const1. + return getConstant(false); +} + +/// visitICmpInstWithInstAndIntCst - Handle "icmp (instr, intcst)". +/// +Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, + Instruction *LHSI, + ConstantInt *RHS) { + const APInt &RHSV = RHS->getValue(); + + switch (LHSI->getOpcode()) { + case Instruction::Trunc: + if (ICI.isEquality() && LHSI->hasOneUse()) { + // Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all + // of the high bits truncated out of x are known. + unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(), + SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits(); + APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0); + computeKnownBits(LHSI->getOperand(0), KnownZero, KnownOne, 0, &ICI); + + // If all the high bits are known, we can do this xform. + if ((KnownZero|KnownOne).countLeadingOnes() >= SrcBits-DstBits) { + // Pull in the high bits from known-ones set. + APInt NewRHS = RHS->getValue().zext(SrcBits); + NewRHS |= KnownOne & APInt::getHighBitsSet(SrcBits, SrcBits-DstBits); + return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), + Builder->getInt(NewRHS)); + } + } + break; + + case Instruction::Xor: // (icmp pred (xor X, XorCst), CI) + if (ConstantInt *XorCst = dyn_cast<ConstantInt>(LHSI->getOperand(1))) { + // If this is a comparison that tests the signbit (X < 0) or (x > -1), + // fold the xor. + if ((ICI.getPredicate() == ICmpInst::ICMP_SLT && RHSV == 0) || + (ICI.getPredicate() == ICmpInst::ICMP_SGT && RHSV.isAllOnesValue())) { + Value *CompareVal = LHSI->getOperand(0); + + // If the sign bit of the XorCst is not set, there is no change to + // the operation, just stop using the Xor. + if (!XorCst->isNegative()) { + ICI.setOperand(0, CompareVal); + Worklist.Add(LHSI); + return &ICI; + } + + // Was the old condition true if the operand is positive? + bool isTrueIfPositive = ICI.getPredicate() == ICmpInst::ICMP_SGT; + + // If so, the new one isn't. + isTrueIfPositive ^= true; + + if (isTrueIfPositive) + return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, + SubOne(RHS)); + else + return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, + AddOne(RHS)); + } + + if (LHSI->hasOneUse()) { + // (icmp u/s (xor A SignBit), C) -> (icmp s/u A, (xor C SignBit)) + if (!ICI.isEquality() && XorCst->getValue().isSignBit()) { + const APInt &SignBit = XorCst->getValue(); + ICmpInst::Predicate Pred = ICI.isSigned() + ? ICI.getUnsignedPredicate() + : ICI.getSignedPredicate(); + return new ICmpInst(Pred, LHSI->getOperand(0), + Builder->getInt(RHSV ^ SignBit)); + } + + // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A) + if (!ICI.isEquality() && XorCst->isMaxValue(true)) { + const APInt &NotSignBit = XorCst->getValue(); + ICmpInst::Predicate Pred = ICI.isSigned() + ? ICI.getUnsignedPredicate() + : ICI.getSignedPredicate(); + Pred = ICI.getSwappedPredicate(Pred); + return new ICmpInst(Pred, LHSI->getOperand(0), + Builder->getInt(RHSV ^ NotSignBit)); + } + } + + // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C) + // iff -C is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_UGT && + XorCst->getValue() == ~RHSV && (RHSV + 1).isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), XorCst); + + // (icmp ult (xor X, C), -C) -> (icmp uge X, C) + // iff -C is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_ULT && + XorCst->getValue() == -RHSV && RHSV.isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), XorCst); + } + break; + case Instruction::And: // (icmp pred (and X, AndCst), RHS) + if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) && + LHSI->getOperand(0)->hasOneUse()) { + ConstantInt *AndCst = cast<ConstantInt>(LHSI->getOperand(1)); + + // If the LHS is an AND of a truncating cast, we can widen the + // and/compare to be the input width without changing the value + // produced, eliminating a cast. + if (TruncInst *Cast = dyn_cast<TruncInst>(LHSI->getOperand(0))) { + // We can do this transformation if either the AND constant does not + // have its sign bit set or if it is an equality comparison. + // Extending a relational comparison when we're checking the sign + // bit would not work. + if (ICI.isEquality() || + (!AndCst->isNegative() && RHSV.isNonNegative())) { + Value *NewAnd = + Builder->CreateAnd(Cast->getOperand(0), + ConstantExpr::getZExt(AndCst, Cast->getSrcTy())); + NewAnd->takeName(LHSI); + return new ICmpInst(ICI.getPredicate(), NewAnd, + ConstantExpr::getZExt(RHS, Cast->getSrcTy())); + } + } + + // If the LHS is an AND of a zext, and we have an equality compare, we can + // shrink the and/compare to the smaller type, eliminating the cast. + if (ZExtInst *Cast = dyn_cast<ZExtInst>(LHSI->getOperand(0))) { + IntegerType *Ty = cast<IntegerType>(Cast->getSrcTy()); + // Make sure we don't compare the upper bits, SimplifyDemandedBits + // should fold the icmp to true/false in that case. + if (ICI.isEquality() && RHSV.getActiveBits() <= Ty->getBitWidth()) { + Value *NewAnd = + Builder->CreateAnd(Cast->getOperand(0), + ConstantExpr::getTrunc(AndCst, Ty)); + NewAnd->takeName(LHSI); + return new ICmpInst(ICI.getPredicate(), NewAnd, + ConstantExpr::getTrunc(RHS, Ty)); + } + } + + // If this is: (X >> C1) & C2 != C3 (where any shift and any compare + // could exist), turn it into (X & (C2 << C1)) != (C3 << C1). This + // happens a LOT in code produced by the C front-end, for bitfield + // access. + BinaryOperator *Shift = dyn_cast<BinaryOperator>(LHSI->getOperand(0)); + if (Shift && !Shift->isShift()) + Shift = nullptr; + + ConstantInt *ShAmt; + ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : nullptr; + + // This seemingly simple opportunity to fold away a shift turns out to + // be rather complicated. See PR17827 + // ( http://llvm.org/bugs/show_bug.cgi?id=17827 ) for details. + if (ShAmt) { + bool CanFold = false; + unsigned ShiftOpcode = Shift->getOpcode(); + if (ShiftOpcode == Instruction::AShr) { + // There may be some constraints that make this possible, + // but nothing simple has been discovered yet. + CanFold = false; + } else if (ShiftOpcode == Instruction::Shl) { + // For a left shift, we can fold if the comparison is not signed. + // We can also fold a signed comparison if the mask value and + // comparison value are not negative. These constraints may not be + // obvious, but we can prove that they are correct using an SMT + // solver. + if (!ICI.isSigned() || (!AndCst->isNegative() && !RHS->isNegative())) + CanFold = true; + } else if (ShiftOpcode == Instruction::LShr) { + // For a logical right shift, we can fold if the comparison is not + // signed. We can also fold a signed comparison if the shifted mask + // value and the shifted comparison value are not negative. + // These constraints may not be obvious, but we can prove that they + // are correct using an SMT solver. + if (!ICI.isSigned()) + CanFold = true; + else { + ConstantInt *ShiftedAndCst = + cast<ConstantInt>(ConstantExpr::getShl(AndCst, ShAmt)); + ConstantInt *ShiftedRHSCst = + cast<ConstantInt>(ConstantExpr::getShl(RHS, ShAmt)); + + if (!ShiftedAndCst->isNegative() && !ShiftedRHSCst->isNegative()) + CanFold = true; + } + } + + if (CanFold) { + Constant *NewCst; + if (ShiftOpcode == Instruction::Shl) + NewCst = ConstantExpr::getLShr(RHS, ShAmt); + else + NewCst = ConstantExpr::getShl(RHS, ShAmt); + + // Check to see if we are shifting out any of the bits being + // compared. + if (ConstantExpr::get(ShiftOpcode, NewCst, ShAmt) != RHS) { + // If we shifted bits out, the fold is not going to work out. + // As a special case, check to see if this means that the + // result is always true or false now. + if (ICI.getPredicate() == ICmpInst::ICMP_EQ) + return ReplaceInstUsesWith(ICI, Builder->getFalse()); + if (ICI.getPredicate() == ICmpInst::ICMP_NE) + return ReplaceInstUsesWith(ICI, Builder->getTrue()); + } else { + ICI.setOperand(1, NewCst); + Constant *NewAndCst; + if (ShiftOpcode == Instruction::Shl) + NewAndCst = ConstantExpr::getLShr(AndCst, ShAmt); + else + NewAndCst = ConstantExpr::getShl(AndCst, ShAmt); + LHSI->setOperand(1, NewAndCst); + LHSI->setOperand(0, Shift->getOperand(0)); + Worklist.Add(Shift); // Shift is dead. + return &ICI; + } + } + } + + // Turn ((X >> Y) & C) == 0 into (X & (C << Y)) == 0. The later is + // preferable because it allows the C<<Y expression to be hoisted out + // of a loop if Y is invariant and X is not. + if (Shift && Shift->hasOneUse() && RHSV == 0 && + ICI.isEquality() && !Shift->isArithmeticShift() && + !isa<Constant>(Shift->getOperand(0))) { + // Compute C << Y. + Value *NS; + if (Shift->getOpcode() == Instruction::LShr) { + NS = Builder->CreateShl(AndCst, Shift->getOperand(1)); + } else { + // Insert a logical shift. + NS = Builder->CreateLShr(AndCst, Shift->getOperand(1)); + } + + // Compute X & (C << Y). + Value *NewAnd = + Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName()); + + ICI.setOperand(0, NewAnd); + return &ICI; + } + + // (icmp pred (and (or (lshr X, Y), X), 1), 0) --> + // (icmp pred (and X, (or (shl 1, Y), 1), 0)) + // + // iff pred isn't signed + { + Value *X, *Y, *LShr; + if (!ICI.isSigned() && RHSV == 0) { + if (match(LHSI->getOperand(1), m_One())) { + Constant *One = cast<Constant>(LHSI->getOperand(1)); + Value *Or = LHSI->getOperand(0); + if (match(Or, m_Or(m_Value(LShr), m_Value(X))) && + match(LShr, m_LShr(m_Specific(X), m_Value(Y)))) { + unsigned UsesRemoved = 0; + if (LHSI->hasOneUse()) + ++UsesRemoved; + if (Or->hasOneUse()) + ++UsesRemoved; + if (LShr->hasOneUse()) + ++UsesRemoved; + Value *NewOr = nullptr; + // Compute X & ((1 << Y) | 1) + if (auto *C = dyn_cast<Constant>(Y)) { + if (UsesRemoved >= 1) + NewOr = + ConstantExpr::getOr(ConstantExpr::getNUWShl(One, C), One); + } else { + if (UsesRemoved >= 3) + NewOr = Builder->CreateOr(Builder->CreateShl(One, Y, + LShr->getName(), + /*HasNUW=*/true), + One, Or->getName()); + } + if (NewOr) { + Value *NewAnd = Builder->CreateAnd(X, NewOr, LHSI->getName()); + ICI.setOperand(0, NewAnd); + return &ICI; + } + } + } + } + } + + // Replace ((X & AndCst) > RHSV) with ((X & AndCst) != 0), if any + // bit set in (X & AndCst) will produce a result greater than RHSV. + if (ICI.getPredicate() == ICmpInst::ICMP_UGT) { + unsigned NTZ = AndCst->getValue().countTrailingZeros(); + if ((NTZ < AndCst->getBitWidth()) && + APInt::getOneBitSet(AndCst->getBitWidth(), NTZ).ugt(RHSV)) + return new ICmpInst(ICmpInst::ICMP_NE, LHSI, + Constant::getNullValue(RHS->getType())); + } + } + + // Try to optimize things like "A[i]&42 == 0" to index computations. + if (LoadInst *LI = dyn_cast<LoadInst>(LHSI->getOperand(0))) { + if (GetElementPtrInst *GEP = + dyn_cast<GetElementPtrInst>(LI->getOperand(0))) + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) + if (GV->isConstant() && GV->hasDefinitiveInitializer() && + !LI->isVolatile() && isa<ConstantInt>(LHSI->getOperand(1))) { + ConstantInt *C = cast<ConstantInt>(LHSI->getOperand(1)); + if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV,ICI, C)) + return Res; + } + } + + // X & -C == -C -> X > u ~C + // X & -C != -C -> X <= u ~C + // iff C is a power of 2 + if (ICI.isEquality() && RHS == LHSI->getOperand(1) && (-RHSV).isPowerOf2()) + return new ICmpInst( + ICI.getPredicate() == ICmpInst::ICMP_EQ ? ICmpInst::ICMP_UGT + : ICmpInst::ICMP_ULE, + LHSI->getOperand(0), SubOne(RHS)); + break; + + case Instruction::Or: { + if (!ICI.isEquality() || !RHS->isNullValue() || !LHSI->hasOneUse()) + break; + Value *P, *Q; + if (match(LHSI, m_Or(m_PtrToInt(m_Value(P)), m_PtrToInt(m_Value(Q))))) { + // Simplify icmp eq (or (ptrtoint P), (ptrtoint Q)), 0 + // -> and (icmp eq P, null), (icmp eq Q, null). + Value *ICIP = Builder->CreateICmp(ICI.getPredicate(), P, + Constant::getNullValue(P->getType())); + Value *ICIQ = Builder->CreateICmp(ICI.getPredicate(), Q, + Constant::getNullValue(Q->getType())); + Instruction *Op; + if (ICI.getPredicate() == ICmpInst::ICMP_EQ) + Op = BinaryOperator::CreateAnd(ICIP, ICIQ); + else + Op = BinaryOperator::CreateOr(ICIP, ICIQ); + return Op; + } + break; + } + + case Instruction::Mul: { // (icmp pred (mul X, Val), CI) + ConstantInt *Val = dyn_cast<ConstantInt>(LHSI->getOperand(1)); + if (!Val) break; + + // If this is a signed comparison to 0 and the mul is sign preserving, + // use the mul LHS operand instead. + ICmpInst::Predicate pred = ICI.getPredicate(); + if (isSignTest(pred, RHS) && !Val->isZero() && + cast<BinaryOperator>(LHSI)->hasNoSignedWrap()) + return new ICmpInst(Val->isNegative() ? + ICmpInst::getSwappedPredicate(pred) : pred, + LHSI->getOperand(0), + Constant::getNullValue(RHS->getType())); + + break; + } + + case Instruction::Shl: { // (icmp pred (shl X, ShAmt), CI) + uint32_t TypeBits = RHSV.getBitWidth(); + ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); + if (!ShAmt) { + Value *X; + // (1 << X) pred P2 -> X pred Log2(P2) + if (match(LHSI, m_Shl(m_One(), m_Value(X)))) { + bool RHSVIsPowerOf2 = RHSV.isPowerOf2(); + ICmpInst::Predicate Pred = ICI.getPredicate(); + if (ICI.isUnsigned()) { + if (!RHSVIsPowerOf2) { + // (1 << X) < 30 -> X <= 4 + // (1 << X) <= 30 -> X <= 4 + // (1 << X) >= 30 -> X > 4 + // (1 << X) > 30 -> X > 4 + if (Pred == ICmpInst::ICMP_ULT) + Pred = ICmpInst::ICMP_ULE; + else if (Pred == ICmpInst::ICMP_UGE) + Pred = ICmpInst::ICMP_UGT; + } + unsigned RHSLog2 = RHSV.logBase2(); + + // (1 << X) >= 2147483648 -> X >= 31 -> X == 31 + // (1 << X) < 2147483648 -> X < 31 -> X != 31 + if (RHSLog2 == TypeBits-1) { + if (Pred == ICmpInst::ICMP_UGE) + Pred = ICmpInst::ICMP_EQ; + else if (Pred == ICmpInst::ICMP_ULT) + Pred = ICmpInst::ICMP_NE; + } + + return new ICmpInst(Pred, X, + ConstantInt::get(RHS->getType(), RHSLog2)); + } else if (ICI.isSigned()) { + if (RHSV.isAllOnesValue()) { + // (1 << X) <= -1 -> X == 31 + if (Pred == ICmpInst::ICMP_SLE) + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + + // (1 << X) > -1 -> X != 31 + if (Pred == ICmpInst::ICMP_SGT) + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + } else if (!RHSV) { + // (1 << X) < 0 -> X == 31 + // (1 << X) <= 0 -> X == 31 + if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + + // (1 << X) >= 0 -> X != 31 + // (1 << X) > 0 -> X != 31 + if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(RHS->getType(), TypeBits-1)); + } + } else if (ICI.isEquality()) { + if (RHSVIsPowerOf2) + return new ICmpInst( + Pred, X, ConstantInt::get(RHS->getType(), RHSV.logBase2())); + } + } + break; + } + + // Check that the shift amount is in range. If not, don't perform + // undefined shifts. When the shift is visited it will be + // simplified. + if (ShAmt->uge(TypeBits)) + break; + + if (ICI.isEquality()) { + // If we are comparing against bits always shifted out, the + // comparison cannot succeed. + Constant *Comp = + ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt), + ShAmt); + if (Comp != RHS) {// Comparing against a bit that we know is zero. + bool IsICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; + Constant *Cst = Builder->getInt1(IsICMP_NE); + return ReplaceInstUsesWith(ICI, Cst); + } + + // If the shift is NUW, then it is just shifting out zeros, no need for an + // AND. + if (cast<BinaryOperator>(LHSI)->hasNoUnsignedWrap()) + return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), + ConstantExpr::getLShr(RHS, ShAmt)); + + // If the shift is NSW and we compare to 0, then it is just shifting out + // sign bits, no need for an AND either. + if (cast<BinaryOperator>(LHSI)->hasNoSignedWrap() && RHSV == 0) + return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), + ConstantExpr::getLShr(RHS, ShAmt)); + + if (LHSI->hasOneUse()) { + // Otherwise strength reduce the shift into an and. + uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); + Constant *Mask = Builder->getInt(APInt::getLowBitsSet(TypeBits, + TypeBits - ShAmtVal)); + + Value *And = + Builder->CreateAnd(LHSI->getOperand(0),Mask, LHSI->getName()+".mask"); + return new ICmpInst(ICI.getPredicate(), And, + ConstantExpr::getLShr(RHS, ShAmt)); + } + } + + // If this is a signed comparison to 0 and the shift is sign preserving, + // use the shift LHS operand instead. + ICmpInst::Predicate pred = ICI.getPredicate(); + if (isSignTest(pred, RHS) && + cast<BinaryOperator>(LHSI)->hasNoSignedWrap()) + return new ICmpInst(pred, + LHSI->getOperand(0), + Constant::getNullValue(RHS->getType())); + + // Otherwise, if this is a comparison of the sign bit, simplify to and/test. + bool TrueIfSigned = false; + if (LHSI->hasOneUse() && + isSignBitCheck(ICI.getPredicate(), RHS, TrueIfSigned)) { + // (X << 31) <s 0 --> (X&1) != 0 + Constant *Mask = ConstantInt::get(LHSI->getOperand(0)->getType(), + APInt::getOneBitSet(TypeBits, + TypeBits-ShAmt->getZExtValue()-1)); + Value *And = + Builder->CreateAnd(LHSI->getOperand(0), Mask, LHSI->getName()+".mask"); + return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ, + And, Constant::getNullValue(And->getType())); + } + + // Transform (icmp pred iM (shl iM %v, N), CI) + // -> (icmp pred i(M-N) (trunc %v iM to i(M-N)), (trunc (CI>>N)) + // Transform the shl to a trunc if (trunc (CI>>N)) has no loss and M-N. + // This enables to get rid of the shift in favor of a trunc which can be + // free on the target. It has the additional benefit of comparing to a + // smaller constant, which will be target friendly. + unsigned Amt = ShAmt->getLimitedValue(TypeBits-1); + if (LHSI->hasOneUse() && + Amt != 0 && RHSV.countTrailingZeros() >= Amt) { + Type *NTy = IntegerType::get(ICI.getContext(), TypeBits - Amt); + Constant *NCI = ConstantExpr::getTrunc( + ConstantExpr::getAShr(RHS, + ConstantInt::get(RHS->getType(), Amt)), + NTy); + return new ICmpInst(ICI.getPredicate(), + Builder->CreateTrunc(LHSI->getOperand(0), NTy), + NCI); + } + + break; + } + + case Instruction::LShr: // (icmp pred (shr X, ShAmt), CI) + case Instruction::AShr: { + // Handle equality comparisons of shift-by-constant. + BinaryOperator *BO = cast<BinaryOperator>(LHSI); + if (ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1))) { + if (Instruction *Res = FoldICmpShrCst(ICI, BO, ShAmt)) + return Res; + } + + // Handle exact shr's. + if (ICI.isEquality() && BO->isExact() && BO->hasOneUse()) { + if (RHSV.isMinValue()) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), RHS); + } + break; + } + + case Instruction::SDiv: + case Instruction::UDiv: + // Fold: icmp pred ([us]div X, C1), C2 -> range test + // Fold this div into the comparison, producing a range check. + // Determine, based on the divide type, what the range is being + // checked. If there is an overflow on the low or high side, remember + // it, otherwise compute the range [low, hi) bounding the new value. + // See: InsertRangeTest above for the kinds of replacements possible. + if (ConstantInt *DivRHS = dyn_cast<ConstantInt>(LHSI->getOperand(1))) + if (Instruction *R = FoldICmpDivCst(ICI, cast<BinaryOperator>(LHSI), + DivRHS)) + return R; + break; + + case Instruction::Sub: { + ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(0)); + if (!LHSC) break; + const APInt &LHSV = LHSC->getValue(); + + // C1-X <u C2 -> (X|(C2-1)) == C1 + // iff C1 & (C2-1) == C2-1 + // C2 is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() && + RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == (RHSV - 1)) + return new ICmpInst(ICmpInst::ICMP_EQ, + Builder->CreateOr(LHSI->getOperand(1), RHSV - 1), + LHSC); + + // C1-X >u C2 -> (X|C2) != C1 + // iff C1 & C2 == C2 + // C2+1 is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() && + (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == RHSV) + return new ICmpInst(ICmpInst::ICMP_NE, + Builder->CreateOr(LHSI->getOperand(1), RHSV), LHSC); + break; + } + + case Instruction::Add: + // Fold: icmp pred (add X, C1), C2 + if (!ICI.isEquality()) { + ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(1)); + if (!LHSC) break; + const APInt &LHSV = LHSC->getValue(); + + ConstantRange CR = ICI.makeConstantRange(ICI.getPredicate(), RHSV) + .subtract(LHSV); + + if (ICI.isSigned()) { + if (CR.getLower().isSignBit()) { + return new ICmpInst(ICmpInst::ICMP_SLT, LHSI->getOperand(0), + Builder->getInt(CR.getUpper())); + } else if (CR.getUpper().isSignBit()) { + return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0), + Builder->getInt(CR.getLower())); + } + } else { + if (CR.getLower().isMinValue()) { + return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), + Builder->getInt(CR.getUpper())); + } else if (CR.getUpper().isMinValue()) { + return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), + Builder->getInt(CR.getLower())); + } + } + + // X-C1 <u C2 -> (X & -C2) == C1 + // iff C1 & (C2-1) == 0 + // C2 is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() && + RHSV.isPowerOf2() && (LHSV & (RHSV - 1)) == 0) + return new ICmpInst(ICmpInst::ICMP_EQ, + Builder->CreateAnd(LHSI->getOperand(0), -RHSV), + ConstantExpr::getNeg(LHSC)); + + // X-C1 >u C2 -> (X & ~C2) != C1 + // iff C1 & C2 == 0 + // C2+1 is a power of 2 + if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() && + (RHSV + 1).isPowerOf2() && (LHSV & RHSV) == 0) + return new ICmpInst(ICmpInst::ICMP_NE, + Builder->CreateAnd(LHSI->getOperand(0), ~RHSV), + ConstantExpr::getNeg(LHSC)); + } + break; + } + + // Simplify icmp_eq and icmp_ne instructions with integer constant RHS. + if (ICI.isEquality()) { + bool isICMP_NE = ICI.getPredicate() == ICmpInst::ICMP_NE; + + // If the first operand is (add|sub|and|or|xor|rem) with a constant, and + // the second operand is a constant, simplify a bit. + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(LHSI)) { + switch (BO->getOpcode()) { + case Instruction::SRem: + // If we have a signed (X % (2^c)) == 0, turn it into an unsigned one. + if (RHSV == 0 && isa<ConstantInt>(BO->getOperand(1)) &&BO->hasOneUse()){ + const APInt &V = cast<ConstantInt>(BO->getOperand(1))->getValue(); + if (V.sgt(1) && V.isPowerOf2()) { + Value *NewRem = + Builder->CreateURem(BO->getOperand(0), BO->getOperand(1), + BO->getName()); + return new ICmpInst(ICI.getPredicate(), NewRem, + Constant::getNullValue(BO->getType())); + } + } + break; + case Instruction::Add: + // Replace ((add A, B) != C) with (A != C-B) if B & C are constants. + if (ConstantInt *BOp1C = dyn_cast<ConstantInt>(BO->getOperand(1))) { + if (BO->hasOneUse()) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + ConstantExpr::getSub(RHS, BOp1C)); + } else if (RHSV == 0) { + // Replace ((add A, B) != 0) with (A != -B) if A or B is + // efficiently invertible, or if the add has just this one use. + Value *BOp0 = BO->getOperand(0), *BOp1 = BO->getOperand(1); + + if (Value *NegVal = dyn_castNegVal(BOp1)) + return new ICmpInst(ICI.getPredicate(), BOp0, NegVal); + if (Value *NegVal = dyn_castNegVal(BOp0)) + return new ICmpInst(ICI.getPredicate(), NegVal, BOp1); + if (BO->hasOneUse()) { + Value *Neg = Builder->CreateNeg(BOp1); + Neg->takeName(BO); + return new ICmpInst(ICI.getPredicate(), BOp0, Neg); + } + } + break; + case Instruction::Xor: + // For the xor case, we can xor two constants together, eliminating + // the explicit xor. + if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) { + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + ConstantExpr::getXor(RHS, BOC)); + } else if (RHSV == 0) { + // Replace ((xor A, B) != 0) with (A != B) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + BO->getOperand(1)); + } + break; + case Instruction::Sub: + // Replace ((sub A, B) != C) with (B != A-C) if A & C are constants. + if (ConstantInt *BOp0C = dyn_cast<ConstantInt>(BO->getOperand(0))) { + if (BO->hasOneUse()) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(1), + ConstantExpr::getSub(BOp0C, RHS)); + } else if (RHSV == 0) { + // Replace ((sub A, B) != 0) with (A != B) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + BO->getOperand(1)); + } + break; + case Instruction::Or: + // If bits are being or'd in that are not present in the constant we + // are comparing against, then the comparison could never succeed! + if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { + Constant *NotCI = ConstantExpr::getNot(RHS); + if (!ConstantExpr::getAnd(BOC, NotCI)->isNullValue()) + return ReplaceInstUsesWith(ICI, Builder->getInt1(isICMP_NE)); + } + break; + + case Instruction::And: + if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { + // If bits are being compared against that are and'd out, then the + // comparison can never succeed! + if ((RHSV & ~BOC->getValue()) != 0) + return ReplaceInstUsesWith(ICI, Builder->getInt1(isICMP_NE)); + + // If we have ((X & C) == C), turn it into ((X & C) != 0). + if (RHS == BOC && RHSV.isPowerOf2()) + return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : + ICmpInst::ICMP_NE, LHSI, + Constant::getNullValue(RHS->getType())); + + // Don't perform the following transforms if the AND has multiple uses + if (!BO->hasOneUse()) + break; + + // Replace (and X, (1 << size(X)-1) != 0) with x s< 0 + if (BOC->getValue().isSignBit()) { + Value *X = BO->getOperand(0); + Constant *Zero = Constant::getNullValue(X->getType()); + ICmpInst::Predicate pred = isICMP_NE ? + ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE; + return new ICmpInst(pred, X, Zero); + } + + // ((X & ~7) == 0) --> X < 8 + if (RHSV == 0 && isHighOnes(BOC)) { + Value *X = BO->getOperand(0); + Constant *NegX = ConstantExpr::getNeg(BOC); + ICmpInst::Predicate pred = isICMP_NE ? + ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT; + return new ICmpInst(pred, X, NegX); + } + } + break; + case Instruction::Mul: + if (RHSV == 0 && BO->hasNoSignedWrap()) { + if (ConstantInt *BOC = dyn_cast<ConstantInt>(BO->getOperand(1))) { + // The trivial case (mul X, 0) is handled by InstSimplify + // General case : (mul X, C) != 0 iff X != 0 + // (mul X, C) == 0 iff X == 0 + if (!BOC->isZero()) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + Constant::getNullValue(RHS->getType())); + } + } + break; + default: break; + } + } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(LHSI)) { + // Handle icmp {eq|ne} <intrinsic>, intcst. + switch (II->getIntrinsicID()) { + case Intrinsic::bswap: + Worklist.Add(II); + ICI.setOperand(0, II->getArgOperand(0)); + ICI.setOperand(1, Builder->getInt(RHSV.byteSwap())); + return &ICI; + case Intrinsic::ctlz: + case Intrinsic::cttz: + // ctz(A) == bitwidth(a) -> A == 0 and likewise for != + if (RHSV == RHS->getType()->getBitWidth()) { + Worklist.Add(II); + ICI.setOperand(0, II->getArgOperand(0)); + ICI.setOperand(1, ConstantInt::get(RHS->getType(), 0)); + return &ICI; + } + break; + case Intrinsic::ctpop: + // popcount(A) == 0 -> A == 0 and likewise for != + if (RHS->isZero()) { + Worklist.Add(II); + ICI.setOperand(0, II->getArgOperand(0)); + ICI.setOperand(1, RHS); + return &ICI; + } + break; + default: + break; + } + } + } + return nullptr; +} + +/// visitICmpInstWithCastAndCast - Handle icmp (cast x to y), (cast/cst). +/// We only handle extending casts so far. +/// +Instruction *InstCombiner::visitICmpInstWithCastAndCast(ICmpInst &ICI) { + const CastInst *LHSCI = cast<CastInst>(ICI.getOperand(0)); + Value *LHSCIOp = LHSCI->getOperand(0); + Type *SrcTy = LHSCIOp->getType(); + Type *DestTy = LHSCI->getType(); + Value *RHSCIOp; + + // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the + // integer type is the same size as the pointer type. + if (LHSCI->getOpcode() == Instruction::PtrToInt && + DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) { + Value *RHSOp = nullptr; + if (PtrToIntOperator *RHSC = dyn_cast<PtrToIntOperator>(ICI.getOperand(1))) { + Value *RHSCIOp = RHSC->getOperand(0); + if (RHSCIOp->getType()->getPointerAddressSpace() == + LHSCIOp->getType()->getPointerAddressSpace()) { + RHSOp = RHSC->getOperand(0); + // If the pointer types don't match, insert a bitcast. + if (LHSCIOp->getType() != RHSOp->getType()) + RHSOp = Builder->CreateBitCast(RHSOp, LHSCIOp->getType()); + } + } else if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) + RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy); + + if (RHSOp) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSOp); + } + + // The code below only handles extension cast instructions, so far. + // Enforce this. + if (LHSCI->getOpcode() != Instruction::ZExt && + LHSCI->getOpcode() != Instruction::SExt) + return nullptr; + + bool isSignedExt = LHSCI->getOpcode() == Instruction::SExt; + bool isSignedCmp = ICI.isSigned(); + + if (CastInst *CI = dyn_cast<CastInst>(ICI.getOperand(1))) { + // Not an extension from the same type? + RHSCIOp = CI->getOperand(0); + if (RHSCIOp->getType() != LHSCIOp->getType()) + return nullptr; + + // If the signedness of the two casts doesn't agree (i.e. one is a sext + // and the other is a zext), then we can't handle this. + if (CI->getOpcode() != LHSCI->getOpcode()) + return nullptr; + + // Deal with equality cases early. + if (ICI.isEquality()) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); + + // A signed comparison of sign extended values simplifies into a + // signed comparison. + if (isSignedCmp && isSignedExt) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, RHSCIOp); + + // The other three cases all fold into an unsigned comparison. + return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, RHSCIOp); + } + + // If we aren't dealing with a constant on the RHS, exit early + ConstantInt *CI = dyn_cast<ConstantInt>(ICI.getOperand(1)); + if (!CI) + return nullptr; + + // Compute the constant that would happen if we truncated to SrcTy then + // reextended to DestTy. + Constant *Res1 = ConstantExpr::getTrunc(CI, SrcTy); + Constant *Res2 = ConstantExpr::getCast(LHSCI->getOpcode(), + Res1, DestTy); + + // If the re-extended constant didn't change... + if (Res2 == CI) { + // Deal with equality cases early. + if (ICI.isEquality()) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); + + // A signed comparison of sign extended values simplifies into a + // signed comparison. + if (isSignedExt && isSignedCmp) + return new ICmpInst(ICI.getPredicate(), LHSCIOp, Res1); + + // The other three cases all fold into an unsigned comparison. + return new ICmpInst(ICI.getUnsignedPredicate(), LHSCIOp, Res1); + } + + // The re-extended constant changed so the constant cannot be represented + // in the shorter type. Consequently, we cannot emit a simple comparison. + // All the cases that fold to true or false will have already been handled + // by SimplifyICmpInst, so only deal with the tricky case. + + if (isSignedCmp || !isSignedExt) + return nullptr; + + // Evaluate the comparison for LT (we invert for GT below). LE and GE cases + // should have been folded away previously and not enter in here. + + // We're performing an unsigned comp with a sign extended value. + // This is true if the input is >= 0. [aka >s -1] + Constant *NegOne = Constant::getAllOnesValue(SrcTy); + Value *Result = Builder->CreateICmpSGT(LHSCIOp, NegOne, ICI.getName()); + + // Finally, return the value computed. + if (ICI.getPredicate() == ICmpInst::ICMP_ULT) + return ReplaceInstUsesWith(ICI, Result); + + assert(ICI.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!"); + return BinaryOperator::CreateNot(Result); +} + +/// ProcessUGT_ADDCST_ADD - The caller has matched a pattern of the form: +/// I = icmp ugt (add (add A, B), CI2), CI1 +/// If this is of the form: +/// sum = a + b +/// if (sum+128 >u 255) +/// Then replace it with llvm.sadd.with.overflow.i8. +/// +static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B, + ConstantInt *CI2, ConstantInt *CI1, + InstCombiner &IC) { + // The transformation we're trying to do here is to transform this into an + // llvm.sadd.with.overflow. To do this, we have to replace the original add + // with a narrower add, and discard the add-with-constant that is part of the + // range check (if we can't eliminate it, this isn't profitable). + + // In order to eliminate the add-with-constant, the compare can be its only + // use. + Instruction *AddWithCst = cast<Instruction>(I.getOperand(0)); + if (!AddWithCst->hasOneUse()) return nullptr; + + // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow. + if (!CI2->getValue().isPowerOf2()) return nullptr; + unsigned NewWidth = CI2->getValue().countTrailingZeros(); + if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31) return nullptr; + + // The width of the new add formed is 1 more than the bias. + ++NewWidth; + + // Check to see that CI1 is an all-ones value with NewWidth bits. + if (CI1->getBitWidth() == NewWidth || + CI1->getValue() != APInt::getLowBitsSet(CI1->getBitWidth(), NewWidth)) + return nullptr; + + // This is only really a signed overflow check if the inputs have been + // sign-extended; check for that condition. For example, if CI2 is 2^31 and + // the operands of the add are 64 bits wide, we need at least 33 sign bits. + unsigned NeededSignBits = CI1->getBitWidth() - NewWidth + 1; + if (IC.ComputeNumSignBits(A, 0, &I) < NeededSignBits || + IC.ComputeNumSignBits(B, 0, &I) < NeededSignBits) + return nullptr; + + // In order to replace the original add with a narrower + // llvm.sadd.with.overflow, the only uses allowed are the add-with-constant + // and truncates that discard the high bits of the add. Verify that this is + // the case. + Instruction *OrigAdd = cast<Instruction>(AddWithCst->getOperand(0)); + for (User *U : OrigAdd->users()) { + if (U == AddWithCst) continue; + + // Only accept truncates for now. We would really like a nice recursive + // predicate like SimplifyDemandedBits, but which goes downwards the use-def + // chain to see which bits of a value are actually demanded. If the + // original add had another add which was then immediately truncated, we + // could still do the transformation. + TruncInst *TI = dyn_cast<TruncInst>(U); + if (!TI || TI->getType()->getPrimitiveSizeInBits() > NewWidth) + return nullptr; + } + + // If the pattern matches, truncate the inputs to the narrower type and + // use the sadd_with_overflow intrinsic to efficiently compute both the + // result and the overflow bit. + Module *M = I.getParent()->getParent()->getParent(); + + Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth); + Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow, + NewType); + + InstCombiner::BuilderTy *Builder = IC.Builder; + + // Put the new code above the original add, in case there are any uses of the + // add between the add and the compare. + Builder->SetInsertPoint(OrigAdd); + + Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc"); + Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc"); + CallInst *Call = Builder->CreateCall(F, {TruncA, TruncB}, "sadd"); + Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result"); + Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType()); + + // The inner add was the result of the narrow add, zero extended to the + // wider type. Replace it with the result computed by the intrinsic. + IC.ReplaceInstUsesWith(*OrigAdd, ZExt); + + // The original icmp gets replaced with the overflow value. + return ExtractValueInst::Create(Call, 1, "sadd.overflow"); +} + +bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS, + Value *RHS, Instruction &OrigI, + Value *&Result, Constant *&Overflow) { + assert((!OrigI.isCommutative() || + !(isa<Constant>(LHS) && !isa<Constant>(RHS))) && + "call with a constant RHS if possible!"); + + auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) { + Result = OpResult; + Overflow = OverflowVal; + if (ReuseName) + Result->takeName(&OrigI); + return true; + }; + + switch (OCF) { + case OCF_INVALID: + llvm_unreachable("bad overflow check kind!"); + + case OCF_UNSIGNED_ADD: { + OverflowResult OR = computeOverflowForUnsignedAdd(LHS, RHS, &OrigI); + if (OR == OverflowResult::NeverOverflows) + return SetResult(Builder->CreateNUWAdd(LHS, RHS), Builder->getFalse(), + true); + + if (OR == OverflowResult::AlwaysOverflows) + return SetResult(Builder->CreateAdd(LHS, RHS), Builder->getTrue(), true); + } + // FALL THROUGH uadd into sadd + case OCF_SIGNED_ADD: { + // X + 0 -> {X, false} + if (match(RHS, m_Zero())) + return SetResult(LHS, Builder->getFalse(), false); + + // We can strength reduce this signed add into a regular add if we can prove + // that it will never overflow. + if (OCF == OCF_SIGNED_ADD) + if (WillNotOverflowSignedAdd(LHS, RHS, OrigI)) + return SetResult(Builder->CreateNSWAdd(LHS, RHS), Builder->getFalse(), + true); + } + + case OCF_UNSIGNED_SUB: + case OCF_SIGNED_SUB: { + // X - 0 -> {X, false} + if (match(RHS, m_Zero())) + return SetResult(LHS, Builder->getFalse(), false); + + if (OCF == OCF_SIGNED_SUB) { + if (WillNotOverflowSignedSub(LHS, RHS, OrigI)) + return SetResult(Builder->CreateNSWSub(LHS, RHS), Builder->getFalse(), + true); + } else { + if (WillNotOverflowUnsignedSub(LHS, RHS, OrigI)) + return SetResult(Builder->CreateNUWSub(LHS, RHS), Builder->getFalse(), + true); + } + break; + } + + case OCF_UNSIGNED_MUL: { + OverflowResult OR = computeOverflowForUnsignedMul(LHS, RHS, &OrigI); + if (OR == OverflowResult::NeverOverflows) + return SetResult(Builder->CreateNUWMul(LHS, RHS), Builder->getFalse(), + true); + if (OR == OverflowResult::AlwaysOverflows) + return SetResult(Builder->CreateMul(LHS, RHS), Builder->getTrue(), true); + } // FALL THROUGH + case OCF_SIGNED_MUL: + // X * undef -> undef + if (isa<UndefValue>(RHS)) + return SetResult(RHS, UndefValue::get(Builder->getInt1Ty()), false); + + // X * 0 -> {0, false} + if (match(RHS, m_Zero())) + return SetResult(RHS, Builder->getFalse(), false); + + // X * 1 -> {X, false} + if (match(RHS, m_One())) + return SetResult(LHS, Builder->getFalse(), false); + + if (OCF == OCF_SIGNED_MUL) + if (WillNotOverflowSignedMul(LHS, RHS, OrigI)) + return SetResult(Builder->CreateNSWMul(LHS, RHS), Builder->getFalse(), + true); + } + + return false; +} + +/// \brief Recognize and process idiom involving test for multiplication +/// overflow. +/// +/// The caller has matched a pattern of the form: +/// I = cmp u (mul(zext A, zext B), V +/// The function checks if this is a test for overflow and if so replaces +/// multiplication with call to 'mul.with.overflow' intrinsic. +/// +/// \param I Compare instruction. +/// \param MulVal Result of 'mult' instruction. It is one of the arguments of +/// the compare instruction. Must be of integer type. +/// \param OtherVal The other argument of compare instruction. +/// \returns Instruction which must replace the compare instruction, NULL if no +/// replacement required. +static Instruction *ProcessUMulZExtIdiom(ICmpInst &I, Value *MulVal, + Value *OtherVal, InstCombiner &IC) { + // Don't bother doing this transformation for pointers, don't do it for + // vectors. + if (!isa<IntegerType>(MulVal->getType())) + return nullptr; + + assert(I.getOperand(0) == MulVal || I.getOperand(1) == MulVal); + assert(I.getOperand(0) == OtherVal || I.getOperand(1) == OtherVal); + Instruction *MulInstr = cast<Instruction>(MulVal); + assert(MulInstr->getOpcode() == Instruction::Mul); + + auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)), + *RHS = cast<ZExtOperator>(MulInstr->getOperand(1)); + assert(LHS->getOpcode() == Instruction::ZExt); + assert(RHS->getOpcode() == Instruction::ZExt); + Value *A = LHS->getOperand(0), *B = RHS->getOperand(0); + + // Calculate type and width of the result produced by mul.with.overflow. + Type *TyA = A->getType(), *TyB = B->getType(); + unsigned WidthA = TyA->getPrimitiveSizeInBits(), + WidthB = TyB->getPrimitiveSizeInBits(); + unsigned MulWidth; + Type *MulType; + if (WidthB > WidthA) { + MulWidth = WidthB; + MulType = TyB; + } else { + MulWidth = WidthA; + MulType = TyA; + } + + // In order to replace the original mul with a narrower mul.with.overflow, + // all uses must ignore upper bits of the product. The number of used low + // bits must be not greater than the width of mul.with.overflow. + if (MulVal->hasNUsesOrMore(2)) + for (User *U : MulVal->users()) { + if (U == &I) + continue; + if (TruncInst *TI = dyn_cast<TruncInst>(U)) { + // Check if truncation ignores bits above MulWidth. + unsigned TruncWidth = TI->getType()->getPrimitiveSizeInBits(); + if (TruncWidth > MulWidth) + return nullptr; + } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) { + // Check if AND ignores bits above MulWidth. + if (BO->getOpcode() != Instruction::And) + return nullptr; + if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->getOperand(1))) { + const APInt &CVal = CI->getValue(); + if (CVal.getBitWidth() - CVal.countLeadingZeros() > MulWidth) + return nullptr; + } + } else { + // Other uses prohibit this transformation. + return nullptr; + } + } + + // Recognize patterns + switch (I.getPredicate()) { + case ICmpInst::ICMP_EQ: + case ICmpInst::ICMP_NE: + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp eq/neq mulval, zext trunc mulval + if (ZExtInst *Zext = dyn_cast<ZExtInst>(OtherVal)) + if (Zext->hasOneUse()) { + Value *ZextArg = Zext->getOperand(0); + if (TruncInst *Trunc = dyn_cast<TruncInst>(ZextArg)) + if (Trunc->getType()->getPrimitiveSizeInBits() == MulWidth) + break; //Recognized + } + + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp eq/neq mulval, and(mulval, mask), mask selects low MulWidth bits. + ConstantInt *CI; + Value *ValToMask; + if (match(OtherVal, m_And(m_Value(ValToMask), m_ConstantInt(CI)))) { + if (ValToMask != MulVal) + return nullptr; + const APInt &CVal = CI->getValue() + 1; + if (CVal.isPowerOf2()) { + unsigned MaskWidth = CVal.logBase2(); + if (MaskWidth == MulWidth) + break; // Recognized + } + } + return nullptr; + + case ICmpInst::ICMP_UGT: + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp ugt mulval, max + if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) { + APInt MaxVal = APInt::getMaxValue(MulWidth); + MaxVal = MaxVal.zext(CI->getBitWidth()); + if (MaxVal.eq(CI->getValue())) + break; // Recognized + } + return nullptr; + + case ICmpInst::ICMP_UGE: + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp uge mulval, max+1 + if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) { + APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth); + if (MaxVal.eq(CI->getValue())) + break; // Recognized + } + return nullptr; + + case ICmpInst::ICMP_ULE: + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp ule mulval, max + if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) { + APInt MaxVal = APInt::getMaxValue(MulWidth); + MaxVal = MaxVal.zext(CI->getBitWidth()); + if (MaxVal.eq(CI->getValue())) + break; // Recognized + } + return nullptr; + + case ICmpInst::ICMP_ULT: + // Recognize pattern: + // mulval = mul(zext A, zext B) + // cmp ule mulval, max + 1 + if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) { + APInt MaxVal = APInt::getOneBitSet(CI->getBitWidth(), MulWidth); + if (MaxVal.eq(CI->getValue())) + break; // Recognized + } + return nullptr; + + default: + return nullptr; + } + + InstCombiner::BuilderTy *Builder = IC.Builder; + Builder->SetInsertPoint(MulInstr); + Module *M = I.getParent()->getParent()->getParent(); + + // Replace: mul(zext A, zext B) --> mul.with.overflow(A, B) + Value *MulA = A, *MulB = B; + if (WidthA < MulWidth) + MulA = Builder->CreateZExt(A, MulType); + if (WidthB < MulWidth) + MulB = Builder->CreateZExt(B, MulType); + Value *F = + Intrinsic::getDeclaration(M, Intrinsic::umul_with_overflow, MulType); + CallInst *Call = Builder->CreateCall(F, {MulA, MulB}, "umul"); + IC.Worklist.Add(MulInstr); + + // If there are uses of mul result other than the comparison, we know that + // they are truncation or binary AND. Change them to use result of + // mul.with.overflow and adjust properly mask/size. + if (MulVal->hasNUsesOrMore(2)) { + Value *Mul = Builder->CreateExtractValue(Call, 0, "umul.value"); + for (User *U : MulVal->users()) { + if (U == &I || U == OtherVal) + continue; + if (TruncInst *TI = dyn_cast<TruncInst>(U)) { + if (TI->getType()->getPrimitiveSizeInBits() == MulWidth) + IC.ReplaceInstUsesWith(*TI, Mul); + else + TI->setOperand(0, Mul); + } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) { + assert(BO->getOpcode() == Instruction::And); + // Replace (mul & mask) --> zext (mul.with.overflow & short_mask) + ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1)); + APInt ShortMask = CI->getValue().trunc(MulWidth); + Value *ShortAnd = Builder->CreateAnd(Mul, ShortMask); + Instruction *Zext = + cast<Instruction>(Builder->CreateZExt(ShortAnd, BO->getType())); + IC.Worklist.Add(Zext); + IC.ReplaceInstUsesWith(*BO, Zext); + } else { + llvm_unreachable("Unexpected Binary operation"); + } + IC.Worklist.Add(cast<Instruction>(U)); + } + } + if (isa<Instruction>(OtherVal)) + IC.Worklist.Add(cast<Instruction>(OtherVal)); + + // The original icmp gets replaced with the overflow value, maybe inverted + // depending on predicate. + bool Inverse = false; + switch (I.getPredicate()) { + case ICmpInst::ICMP_NE: + break; + case ICmpInst::ICMP_EQ: + Inverse = true; + break; + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_UGE: + if (I.getOperand(0) == MulVal) + break; + Inverse = true; + break; + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_ULE: + if (I.getOperand(1) == MulVal) + break; + Inverse = true; + break; + default: + llvm_unreachable("Unexpected predicate"); + } + if (Inverse) { + Value *Res = Builder->CreateExtractValue(Call, 1); + return BinaryOperator::CreateNot(Res); + } + + return ExtractValueInst::Create(Call, 1); +} + +// DemandedBitsLHSMask - When performing a comparison against a constant, +// it is possible that not all the bits in the LHS are demanded. This helper +// method computes the mask that IS demanded. +static APInt DemandedBitsLHSMask(ICmpInst &I, + unsigned BitWidth, bool isSignCheck) { + if (isSignCheck) + return APInt::getSignBit(BitWidth); + + ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand(1)); + if (!CI) return APInt::getAllOnesValue(BitWidth); + const APInt &RHS = CI->getValue(); + + switch (I.getPredicate()) { + // For a UGT comparison, we don't care about any bits that + // correspond to the trailing ones of the comparand. The value of these + // bits doesn't impact the outcome of the comparison, because any value + // greater than the RHS must differ in a bit higher than these due to carry. + case ICmpInst::ICMP_UGT: { + unsigned trailingOnes = RHS.countTrailingOnes(); + APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingOnes); + return ~lowBitsSet; + } + + // Similarly, for a ULT comparison, we don't care about the trailing zeros. + // Any value less than the RHS must differ in a higher bit because of carries. + case ICmpInst::ICMP_ULT: { + unsigned trailingZeros = RHS.countTrailingZeros(); + APInt lowBitsSet = APInt::getLowBitsSet(BitWidth, trailingZeros); + return ~lowBitsSet; + } + + default: + return APInt::getAllOnesValue(BitWidth); + } + +} + +/// \brief Check if the order of \p Op0 and \p Op1 as operand in an ICmpInst +/// should be swapped. +/// The decision is based on how many times these two operands are reused +/// as subtract operands and their positions in those instructions. +/// The rational is that several architectures use the same instruction for +/// both subtract and cmp, thus it is better if the order of those operands +/// match. +/// \return true if Op0 and Op1 should be swapped. +static bool swapMayExposeCSEOpportunities(const Value * Op0, + const Value * Op1) { + // Filter out pointer value as those cannot appears directly in subtract. + // FIXME: we may want to go through inttoptrs or bitcasts. + if (Op0->getType()->isPointerTy()) + return false; + // Count every uses of both Op0 and Op1 in a subtract. + // Each time Op0 is the first operand, count -1: swapping is bad, the + // subtract has already the same layout as the compare. + // Each time Op0 is the second operand, count +1: swapping is good, the + // subtract has a different layout as the compare. + // At the end, if the benefit is greater than 0, Op0 should come second to + // expose more CSE opportunities. + int GlobalSwapBenefits = 0; + for (const User *U : Op0->users()) { + const BinaryOperator *BinOp = dyn_cast<BinaryOperator>(U); + if (!BinOp || BinOp->getOpcode() != Instruction::Sub) + continue; + // If Op0 is the first argument, this is not beneficial to swap the + // arguments. + int LocalSwapBenefits = -1; + unsigned Op1Idx = 1; + if (BinOp->getOperand(Op1Idx) == Op0) { + Op1Idx = 0; + LocalSwapBenefits = 1; + } + if (BinOp->getOperand(Op1Idx) != Op1) + continue; + GlobalSwapBenefits += LocalSwapBenefits; + } + return GlobalSwapBenefits > 0; +} + +/// \brief Check that one use is in the same block as the definition and all +/// other uses are in blocks dominated by a given block +/// +/// \param DI Definition +/// \param UI Use +/// \param DB Block that must dominate all uses of \p DI outside +/// the parent block +/// \return true when \p UI is the only use of \p DI in the parent block +/// and all other uses of \p DI are in blocks dominated by \p DB. +/// +bool InstCombiner::dominatesAllUses(const Instruction *DI, + const Instruction *UI, + const BasicBlock *DB) const { + assert(DI && UI && "Instruction not defined\n"); + // ignore incomplete definitions + if (!DI->getParent()) + return false; + // DI and UI must be in the same block + if (DI->getParent() != UI->getParent()) + return false; + // Protect from self-referencing blocks + if (DI->getParent() == DB) + return false; + // DominatorTree available? + if (!DT) + return false; + for (const User *U : DI->users()) { + auto *Usr = cast<Instruction>(U); + if (Usr != UI && !DT->dominates(DB, Usr->getParent())) + return false; + } + return true; +} + +/// +/// true when the instruction sequence within a block is select-cmp-br. +/// +static bool isChainSelectCmpBranch(const SelectInst *SI) { + const BasicBlock *BB = SI->getParent(); + if (!BB) + return false; + auto *BI = dyn_cast_or_null<BranchInst>(BB->getTerminator()); + if (!BI || BI->getNumSuccessors() != 2) + return false; + auto *IC = dyn_cast<ICmpInst>(BI->getCondition()); + if (!IC || (IC->getOperand(0) != SI && IC->getOperand(1) != SI)) + return false; + return true; +} + +/// +/// \brief True when a select result is replaced by one of its operands +/// in select-icmp sequence. This will eventually result in the elimination +/// of the select. +/// +/// \param SI Select instruction +/// \param Icmp Compare instruction +/// \param SIOpd Operand that replaces the select +/// +/// Notes: +/// - The replacement is global and requires dominator information +/// - The caller is responsible for the actual replacement +/// +/// Example: +/// +/// entry: +/// %4 = select i1 %3, %C* %0, %C* null +/// %5 = icmp eq %C* %4, null +/// br i1 %5, label %9, label %7 +/// ... +/// ; <label>:7 ; preds = %entry +/// %8 = getelementptr inbounds %C* %4, i64 0, i32 0 +/// ... +/// +/// can be transformed to +/// +/// %5 = icmp eq %C* %0, null +/// %6 = select i1 %3, i1 %5, i1 true +/// br i1 %6, label %9, label %7 +/// ... +/// ; <label>:7 ; preds = %entry +/// %8 = getelementptr inbounds %C* %0, i64 0, i32 0 // replace by %0! +/// +/// Similar when the first operand of the select is a constant or/and +/// the compare is for not equal rather than equal. +/// +/// NOTE: The function is only called when the select and compare constants +/// are equal, the optimization can work only for EQ predicates. This is not a +/// major restriction since a NE compare should be 'normalized' to an equal +/// compare, which usually happens in the combiner and test case +/// select-cmp-br.ll +/// checks for it. +bool InstCombiner::replacedSelectWithOperand(SelectInst *SI, + const ICmpInst *Icmp, + const unsigned SIOpd) { + assert((SIOpd == 1 || SIOpd == 2) && "Invalid select operand!"); + if (isChainSelectCmpBranch(SI) && Icmp->getPredicate() == ICmpInst::ICMP_EQ) { + BasicBlock *Succ = SI->getParent()->getTerminator()->getSuccessor(1); + // The check for the unique predecessor is not the best that can be + // done. But it protects efficiently against cases like when SI's + // home block has two successors, Succ and Succ1, and Succ1 predecessor + // of Succ. Then SI can't be replaced by SIOpd because the use that gets + // replaced can be reached on either path. So the uniqueness check + // guarantees that the path all uses of SI (outside SI's parent) are on + // is disjoint from all other paths out of SI. But that information + // is more expensive to compute, and the trade-off here is in favor + // of compile-time. + if (Succ->getUniquePredecessor() && dominatesAllUses(SI, Icmp, Succ)) { + NumSel++; + SI->replaceUsesOutsideBlock(SI->getOperand(SIOpd), SI->getParent()); + return true; + } + } + return false; +} + +Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { + bool Changed = false; + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + unsigned Op0Cplxity = getComplexity(Op0); + unsigned Op1Cplxity = getComplexity(Op1); + + /// Orders the operands of the compare so that they are listed from most + /// complex to least complex. This puts constants before unary operators, + /// before binary operators. + if (Op0Cplxity < Op1Cplxity || + (Op0Cplxity == Op1Cplxity && + swapMayExposeCSEOpportunities(Op0, Op1))) { + I.swapOperands(); + std::swap(Op0, Op1); + Changed = true; + } + + if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC)) + return ReplaceInstUsesWith(I, V); + + // comparing -val or val with non-zero is the same as just comparing val + // ie, abs(val) != 0 -> val != 0 + if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero())) + { + Value *Cond, *SelectTrue, *SelectFalse; + if (match(Op0, m_Select(m_Value(Cond), m_Value(SelectTrue), + m_Value(SelectFalse)))) { + if (Value *V = dyn_castNegVal(SelectTrue)) { + if (V == SelectFalse) + return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1); + } + else if (Value *V = dyn_castNegVal(SelectFalse)) { + if (V == SelectTrue) + return CmpInst::Create(Instruction::ICmp, I.getPredicate(), V, Op1); + } + } + } + + Type *Ty = Op0->getType(); + + // icmp's with boolean values can always be turned into bitwise operations + if (Ty->isIntegerTy(1)) { + switch (I.getPredicate()) { + default: llvm_unreachable("Invalid icmp instruction!"); + case ICmpInst::ICMP_EQ: { // icmp eq i1 A, B -> ~(A^B) + Value *Xor = Builder->CreateXor(Op0, Op1, I.getName()+"tmp"); + return BinaryOperator::CreateNot(Xor); + } + case ICmpInst::ICMP_NE: // icmp eq i1 A, B -> A^B + return BinaryOperator::CreateXor(Op0, Op1); + + case ICmpInst::ICMP_UGT: + std::swap(Op0, Op1); // Change icmp ugt -> icmp ult + // FALL THROUGH + case ICmpInst::ICMP_ULT:{ // icmp ult i1 A, B -> ~A & B + Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); + return BinaryOperator::CreateAnd(Not, Op1); + } + case ICmpInst::ICMP_SGT: + std::swap(Op0, Op1); // Change icmp sgt -> icmp slt + // FALL THROUGH + case ICmpInst::ICMP_SLT: { // icmp slt i1 A, B -> A & ~B + Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); + return BinaryOperator::CreateAnd(Not, Op0); + } + case ICmpInst::ICMP_UGE: + std::swap(Op0, Op1); // Change icmp uge -> icmp ule + // FALL THROUGH + case ICmpInst::ICMP_ULE: { // icmp ule i1 A, B -> ~A | B + Value *Not = Builder->CreateNot(Op0, I.getName()+"tmp"); + return BinaryOperator::CreateOr(Not, Op1); + } + case ICmpInst::ICMP_SGE: + std::swap(Op0, Op1); // Change icmp sge -> icmp sle + // FALL THROUGH + case ICmpInst::ICMP_SLE: { // icmp sle i1 A, B -> A | ~B + Value *Not = Builder->CreateNot(Op1, I.getName()+"tmp"); + return BinaryOperator::CreateOr(Not, Op0); + } + } + } + + unsigned BitWidth = 0; + if (Ty->isIntOrIntVectorTy()) + BitWidth = Ty->getScalarSizeInBits(); + else // Get pointer size. + BitWidth = DL.getTypeSizeInBits(Ty->getScalarType()); + + bool isSignBit = false; + + // See if we are doing a comparison with a constant. + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + Value *A = nullptr, *B = nullptr; + + // Match the following pattern, which is a common idiom when writing + // overflow-safe integer arithmetic function. The source performs an + // addition in wider type, and explicitly checks for overflow using + // comparisons against INT_MIN and INT_MAX. Simplify this by using the + // sadd_with_overflow intrinsic. + // + // TODO: This could probably be generalized to handle other overflow-safe + // operations if we worked out the formulas to compute the appropriate + // magic constants. + // + // sum = a + b + // if (sum+128 >u 255) ... -> llvm.sadd.with.overflow.i8 + { + ConstantInt *CI2; // I = icmp ugt (add (add A, B), CI2), CI + if (I.getPredicate() == ICmpInst::ICMP_UGT && + match(Op0, m_Add(m_Add(m_Value(A), m_Value(B)), m_ConstantInt(CI2)))) + if (Instruction *Res = ProcessUGT_ADDCST_ADD(I, A, B, CI2, CI, *this)) + return Res; + } + + // The following transforms are only 'worth it' if the only user of the + // subtraction is the icmp. + if (Op0->hasOneUse()) { + // (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B) + if (I.isEquality() && CI->isZero() && + match(Op0, m_Sub(m_Value(A), m_Value(B)))) + return new ICmpInst(I.getPredicate(), A, B); + + // (icmp sgt (sub nsw A B), -1) -> (icmp sge A, B) + if (I.getPredicate() == ICmpInst::ICMP_SGT && CI->isAllOnesValue() && + match(Op0, m_NSWSub(m_Value(A), m_Value(B)))) + return new ICmpInst(ICmpInst::ICMP_SGE, A, B); + + // (icmp sgt (sub nsw A B), 0) -> (icmp sgt A, B) + if (I.getPredicate() == ICmpInst::ICMP_SGT && CI->isZero() && + match(Op0, m_NSWSub(m_Value(A), m_Value(B)))) + return new ICmpInst(ICmpInst::ICMP_SGT, A, B); + + // (icmp slt (sub nsw A B), 0) -> (icmp slt A, B) + if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isZero() && + match(Op0, m_NSWSub(m_Value(A), m_Value(B)))) + return new ICmpInst(ICmpInst::ICMP_SLT, A, B); + + // (icmp slt (sub nsw A B), 1) -> (icmp sle A, B) + if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isOne() && + match(Op0, m_NSWSub(m_Value(A), m_Value(B)))) + return new ICmpInst(ICmpInst::ICMP_SLE, A, B); + } + + // If we have an icmp le or icmp ge instruction, turn it into the + // appropriate icmp lt or icmp gt instruction. This allows us to rely on + // them being folded in the code below. The SimplifyICmpInst code has + // already handled the edge cases for us, so we just assert on them. + switch (I.getPredicate()) { + default: break; + case ICmpInst::ICMP_ULE: + assert(!CI->isMaxValue(false)); // A <=u MAX -> TRUE + return new ICmpInst(ICmpInst::ICMP_ULT, Op0, + Builder->getInt(CI->getValue()+1)); + case ICmpInst::ICMP_SLE: + assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE + return new ICmpInst(ICmpInst::ICMP_SLT, Op0, + Builder->getInt(CI->getValue()+1)); + case ICmpInst::ICMP_UGE: + assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE + return new ICmpInst(ICmpInst::ICMP_UGT, Op0, + Builder->getInt(CI->getValue()-1)); + case ICmpInst::ICMP_SGE: + assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE + return new ICmpInst(ICmpInst::ICMP_SGT, Op0, + Builder->getInt(CI->getValue()-1)); + } + + if (I.isEquality()) { + ConstantInt *CI2; + if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) || + match(Op0, m_LShr(m_ConstantInt(CI2), m_Value(A)))) { + // (icmp eq/ne (ashr/lshr const2, A), const1) + if (Instruction *Inst = FoldICmpCstShrCst(I, Op0, A, CI, CI2)) + return Inst; + } + if (match(Op0, m_Shl(m_ConstantInt(CI2), m_Value(A)))) { + // (icmp eq/ne (shl const2, A), const1) + if (Instruction *Inst = FoldICmpCstShlCst(I, Op0, A, CI, CI2)) + return Inst; + } + } + + // If this comparison is a normal comparison, it demands all + // bits, if it is a sign bit comparison, it only demands the sign bit. + bool UnusedBit; + isSignBit = isSignBitCheck(I.getPredicate(), CI, UnusedBit); + } + + // See if we can fold the comparison based on range information we can get + // by checking whether bits are known to be zero or one in the input. + if (BitWidth != 0) { + APInt Op0KnownZero(BitWidth, 0), Op0KnownOne(BitWidth, 0); + APInt Op1KnownZero(BitWidth, 0), Op1KnownOne(BitWidth, 0); + + if (SimplifyDemandedBits(I.getOperandUse(0), + DemandedBitsLHSMask(I, BitWidth, isSignBit), + Op0KnownZero, Op0KnownOne, 0)) + return &I; + if (SimplifyDemandedBits(I.getOperandUse(1), + APInt::getAllOnesValue(BitWidth), Op1KnownZero, + Op1KnownOne, 0)) + return &I; + + // Given the known and unknown bits, compute a range that the LHS could be + // in. Compute the Min, Max and RHS values based on the known bits. For the + // EQ and NE we use unsigned values. + APInt Op0Min(BitWidth, 0), Op0Max(BitWidth, 0); + APInt Op1Min(BitWidth, 0), Op1Max(BitWidth, 0); + if (I.isSigned()) { + ComputeSignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, + Op0Min, Op0Max); + ComputeSignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, + Op1Min, Op1Max); + } else { + ComputeUnsignedMinMaxValuesFromKnownBits(Op0KnownZero, Op0KnownOne, + Op0Min, Op0Max); + ComputeUnsignedMinMaxValuesFromKnownBits(Op1KnownZero, Op1KnownOne, + Op1Min, Op1Max); + } + + // If Min and Max are known to be the same, then SimplifyDemandedBits + // figured out that the LHS is a constant. Just constant fold this now so + // that code below can assume that Min != Max. + if (!isa<Constant>(Op0) && Op0Min == Op0Max) + return new ICmpInst(I.getPredicate(), + ConstantInt::get(Op0->getType(), Op0Min), Op1); + if (!isa<Constant>(Op1) && Op1Min == Op1Max) + return new ICmpInst(I.getPredicate(), Op0, + ConstantInt::get(Op1->getType(), Op1Min)); + + // Based on the range information we know about the LHS, see if we can + // simplify this comparison. For example, (x&4) < 8 is always true. + switch (I.getPredicate()) { + default: llvm_unreachable("Unknown icmp opcode!"); + case ICmpInst::ICMP_EQ: { + if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + + // If all bits are known zero except for one, then we know at most one + // bit is set. If the comparison is against zero, then this is a check + // to see if *that* bit is set. + APInt Op0KnownZeroInverted = ~Op0KnownZero; + if (~Op1KnownZero == 0) { + // If the LHS is an AND with the same constant, look through it. + Value *LHS = nullptr; + ConstantInt *LHSC = nullptr; + if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || + LHSC->getValue() != Op0KnownZeroInverted) + LHS = Op0; + + // If the LHS is 1 << x, and we know the result is a power of 2 like 8, + // then turn "((1 << x)&8) == 0" into "x != 3". + // or turn "((1 << x)&7) == 0" into "x > 2". + Value *X = nullptr; + if (match(LHS, m_Shl(m_One(), m_Value(X)))) { + APInt ValToCheck = Op0KnownZeroInverted; + if (ValToCheck.isPowerOf2()) { + unsigned CmpVal = ValToCheck.countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(X->getType(), CmpVal)); + } else if ((++ValToCheck).isPowerOf2()) { + unsigned CmpVal = ValToCheck.countTrailingZeros() - 1; + return new ICmpInst(ICmpInst::ICMP_UGT, X, + ConstantInt::get(X->getType(), CmpVal)); + } + } + + // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, + // then turn "((8 >>u x)&1) == 0" into "x != 3". + const APInt *CI; + if (Op0KnownZeroInverted == 1 && + match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) + return new ICmpInst(ICmpInst::ICMP_NE, X, + ConstantInt::get(X->getType(), + CI->countTrailingZeros())); + } + + break; + } + case ICmpInst::ICMP_NE: { + if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max)) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + + // If all bits are known zero except for one, then we know at most one + // bit is set. If the comparison is against zero, then this is a check + // to see if *that* bit is set. + APInt Op0KnownZeroInverted = ~Op0KnownZero; + if (~Op1KnownZero == 0) { + // If the LHS is an AND with the same constant, look through it. + Value *LHS = nullptr; + ConstantInt *LHSC = nullptr; + if (!match(Op0, m_And(m_Value(LHS), m_ConstantInt(LHSC))) || + LHSC->getValue() != Op0KnownZeroInverted) + LHS = Op0; + + // If the LHS is 1 << x, and we know the result is a power of 2 like 8, + // then turn "((1 << x)&8) != 0" into "x == 3". + // or turn "((1 << x)&7) != 0" into "x < 3". + Value *X = nullptr; + if (match(LHS, m_Shl(m_One(), m_Value(X)))) { + APInt ValToCheck = Op0KnownZeroInverted; + if (ValToCheck.isPowerOf2()) { + unsigned CmpVal = ValToCheck.countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(X->getType(), CmpVal)); + } else if ((++ValToCheck).isPowerOf2()) { + unsigned CmpVal = ValToCheck.countTrailingZeros(); + return new ICmpInst(ICmpInst::ICMP_ULT, X, + ConstantInt::get(X->getType(), CmpVal)); + } + } + + // If the LHS is 8 >>u x, and we know the result is a power of 2 like 1, + // then turn "((8 >>u x)&1) != 0" into "x == 3". + const APInt *CI; + if (Op0KnownZeroInverted == 1 && + match(LHS, m_LShr(m_Power2(CI), m_Value(X)))) + return new ICmpInst(ICmpInst::ICMP_EQ, X, + ConstantInt::get(X->getType(), + CI->countTrailingZeros())); + } + + break; + } + case ICmpInst::ICMP_ULT: + if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + if (Op1Min == Op0Max) // A <u B -> A != B if max(A) == min(B) + return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + if (Op1Max == Op0Min+1) // A <u C -> A == C-1 if min(A)+1 == C + return new ICmpInst(ICmpInst::ICMP_EQ, Op0, + Builder->getInt(CI->getValue()-1)); + + // (x <u 2147483648) -> (x >s -1) -> true if sign bit clear + if (CI->isMinValue(true)) + return new ICmpInst(ICmpInst::ICMP_SGT, Op0, + Constant::getAllOnesValue(Op0->getType())); + } + break; + case ICmpInst::ICMP_UGT: + if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + + if (Op1Max == Op0Min) // A >u B -> A != B if min(A) == max(B) + return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + if (Op1Min == Op0Max-1) // A >u C -> A == C+1 if max(a)-1 == C + return new ICmpInst(ICmpInst::ICMP_EQ, Op0, + Builder->getInt(CI->getValue()+1)); + + // (x >u 2147483647) -> (x <s 0) -> true if sign bit set + if (CI->isMaxValue(true)) + return new ICmpInst(ICmpInst::ICMP_SLT, Op0, + Constant::getNullValue(Op0->getType())); + } + break; + case ICmpInst::ICMP_SLT: + if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + if (Op1Min == Op0Max) // A <s B -> A != B if max(A) == min(B) + return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + if (Op1Max == Op0Min+1) // A <s C -> A == C-1 if min(A)+1 == C + return new ICmpInst(ICmpInst::ICMP_EQ, Op0, + Builder->getInt(CI->getValue()-1)); + } + break; + case ICmpInst::ICMP_SGT: + if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + + if (Op1Max == Op0Min) // A >s B -> A != B if min(A) == max(B) + return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1); + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + if (Op1Min == Op0Max-1) // A >s C -> A == C+1 if max(A)-1 == C + return new ICmpInst(ICmpInst::ICMP_EQ, Op0, + Builder->getInt(CI->getValue()+1)); + } + break; + case ICmpInst::ICMP_SGE: + assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!"); + if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + break; + case ICmpInst::ICMP_SLE: + assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!"); + if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + break; + case ICmpInst::ICMP_UGE: + assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!"); + if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + break; + case ICmpInst::ICMP_ULE: + assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!"); + if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B) + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B) + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + break; + } + + // Turn a signed comparison into an unsigned one if both operands + // are known to have the same sign. + if (I.isSigned() && + ((Op0KnownZero.isNegative() && Op1KnownZero.isNegative()) || + (Op0KnownOne.isNegative() && Op1KnownOne.isNegative()))) + return new ICmpInst(I.getUnsignedPredicate(), Op0, Op1); + } + + // Test if the ICmpInst instruction is used exclusively by a select as + // part of a minimum or maximum operation. If so, refrain from doing + // any other folding. This helps out other analyses which understand + // non-obfuscated minimum and maximum idioms, such as ScalarEvolution + // and CodeGen. And in this case, at least one of the comparison + // operands has at least one user besides the compare (the select), + // which would often largely negate the benefit of folding anyway. + if (I.hasOneUse()) + if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin())) + if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || + (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) + return nullptr; + + // See if we are doing a comparison between a constant and an instruction that + // can be folded into the comparison. + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + // Since the RHS is a ConstantInt (CI), if the left hand side is an + // instruction, see if that instruction also has constants so that the + // instruction can be folded into the icmp + if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) + if (Instruction *Res = visitICmpInstWithInstAndIntCst(I, LHSI, CI)) + return Res; + } + + // Handle icmp with constant (but not simple integer constant) RHS + if (Constant *RHSC = dyn_cast<Constant>(Op1)) { + if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) + switch (LHSI->getOpcode()) { + case Instruction::GetElementPtr: + // icmp pred GEP (P, int 0, int 0, int 0), null -> icmp pred P, null + if (RHSC->isNullValue() && + cast<GetElementPtrInst>(LHSI)->hasAllZeroIndices()) + return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), + Constant::getNullValue(LHSI->getOperand(0)->getType())); + break; + case Instruction::PHI: + // Only fold icmp into the PHI if the phi and icmp are in the same + // block. If in the same block, we're encouraging jump threading. If + // not, we are just pessimizing the code by making an i1 phi. + if (LHSI->getParent() == I.getParent()) + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + break; + case Instruction::Select: { + // If either operand of the select is a constant, we can fold the + // comparison into the select arms, which will cause one to be + // constant folded and the select turned into a bitwise or. + Value *Op1 = nullptr, *Op2 = nullptr; + ConstantInt *CI = 0; + if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { + Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); + CI = dyn_cast<ConstantInt>(Op1); + } + if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { + Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); + CI = dyn_cast<ConstantInt>(Op2); + } + + // We only want to perform this transformation if it will not lead to + // additional code. This is true if either both sides of the select + // fold to a constant (in which case the icmp is replaced with a select + // which will usually simplify) or this is the only user of the + // select (in which case we are trading a select+icmp for a simpler + // select+icmp) or all uses of the select can be replaced based on + // dominance information ("Global cases"). + bool Transform = false; + if (Op1 && Op2) + Transform = true; + else if (Op1 || Op2) { + // Local case + if (LHSI->hasOneUse()) + Transform = true; + // Global cases + else if (CI && !CI->isZero()) + // When Op1 is constant try replacing select with second operand. + // Otherwise Op2 is constant and try replacing select with first + // operand. + Transform = replacedSelectWithOperand(cast<SelectInst>(LHSI), &I, + Op1 ? 2 : 1); + } + if (Transform) { + if (!Op1) + Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1), + RHSC, I.getName()); + if (!Op2) + Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), + RHSC, I.getName()); + return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); + } + break; + } + case Instruction::IntToPtr: + // icmp pred inttoptr(X), null -> icmp pred X, 0 + if (RHSC->isNullValue() && + DL.getIntPtrType(RHSC->getType()) == LHSI->getOperand(0)->getType()) + return new ICmpInst(I.getPredicate(), LHSI->getOperand(0), + Constant::getNullValue(LHSI->getOperand(0)->getType())); + break; + + case Instruction::Load: + // Try to optimize things like "A[i] > 4" to index computations. + if (GetElementPtrInst *GEP = + dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) + if (GV->isConstant() && GV->hasDefinitiveInitializer() && + !cast<LoadInst>(LHSI)->isVolatile()) + if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) + return Res; + } + break; + } + } + + // If we can optimize a 'icmp GEP, P' or 'icmp P, GEP', do so now. + if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op0)) + if (Instruction *NI = FoldGEPICmp(GEP, Op1, I.getPredicate(), I)) + return NI; + if (GEPOperator *GEP = dyn_cast<GEPOperator>(Op1)) + if (Instruction *NI = FoldGEPICmp(GEP, Op0, + ICmpInst::getSwappedPredicate(I.getPredicate()), I)) + return NI; + + // Test to see if the operands of the icmp are casted versions of other + // values. If the ptr->ptr cast can be stripped off both arguments, we do so + // now. + if (BitCastInst *CI = dyn_cast<BitCastInst>(Op0)) { + if (Op0->getType()->isPointerTy() && + (isa<Constant>(Op1) || isa<BitCastInst>(Op1))) { + // We keep moving the cast from the left operand over to the right + // operand, where it can often be eliminated completely. + Op0 = CI->getOperand(0); + + // If operand #1 is a bitcast instruction, it must also be a ptr->ptr cast + // so eliminate it as well. + if (BitCastInst *CI2 = dyn_cast<BitCastInst>(Op1)) + Op1 = CI2->getOperand(0); + + // If Op1 is a constant, we can fold the cast into the constant. + if (Op0->getType() != Op1->getType()) { + if (Constant *Op1C = dyn_cast<Constant>(Op1)) { + Op1 = ConstantExpr::getBitCast(Op1C, Op0->getType()); + } else { + // Otherwise, cast the RHS right before the icmp + Op1 = Builder->CreateBitCast(Op1, Op0->getType()); + } + } + return new ICmpInst(I.getPredicate(), Op0, Op1); + } + } + + if (isa<CastInst>(Op0)) { + // Handle the special case of: icmp (cast bool to X), <cst> + // This comes up when you have code like + // int X = A < B; + // if (X) ... + // For generality, we handle any zero-extension of any operand comparison + // with a constant or another cast from the same type. + if (isa<Constant>(Op1) || isa<CastInst>(Op1)) + if (Instruction *R = visitICmpInstWithCastAndCast(I)) + return R; + } + + // Special logic for binary operators. + BinaryOperator *BO0 = dyn_cast<BinaryOperator>(Op0); + BinaryOperator *BO1 = dyn_cast<BinaryOperator>(Op1); + if (BO0 || BO1) { + CmpInst::Predicate Pred = I.getPredicate(); + bool NoOp0WrapProblem = false, NoOp1WrapProblem = false; + if (BO0 && isa<OverflowingBinaryOperator>(BO0)) + NoOp0WrapProblem = ICmpInst::isEquality(Pred) || + (CmpInst::isUnsigned(Pred) && BO0->hasNoUnsignedWrap()) || + (CmpInst::isSigned(Pred) && BO0->hasNoSignedWrap()); + if (BO1 && isa<OverflowingBinaryOperator>(BO1)) + NoOp1WrapProblem = ICmpInst::isEquality(Pred) || + (CmpInst::isUnsigned(Pred) && BO1->hasNoUnsignedWrap()) || + (CmpInst::isSigned(Pred) && BO1->hasNoSignedWrap()); + + // Analyze the case when either Op0 or Op1 is an add instruction. + // Op0 = A + B (or A and B are null); Op1 = C + D (or C and D are null). + Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr; + if (BO0 && BO0->getOpcode() == Instruction::Add) + A = BO0->getOperand(0), B = BO0->getOperand(1); + if (BO1 && BO1->getOpcode() == Instruction::Add) + C = BO1->getOperand(0), D = BO1->getOperand(1); + + // icmp (X+cst) < 0 --> X < -cst + if (NoOp0WrapProblem && ICmpInst::isSigned(Pred) && match(Op1, m_Zero())) + if (ConstantInt *RHSC = dyn_cast_or_null<ConstantInt>(B)) + if (!RHSC->isMinValue(/*isSigned=*/true)) + return new ICmpInst(Pred, A, ConstantExpr::getNeg(RHSC)); + + // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. + if ((A == Op1 || B == Op1) && NoOp0WrapProblem) + return new ICmpInst(Pred, A == Op1 ? B : A, + Constant::getNullValue(Op1->getType())); + + // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. + if ((C == Op0 || D == Op0) && NoOp1WrapProblem) + return new ICmpInst(Pred, Constant::getNullValue(Op0->getType()), + C == Op0 ? D : C); + + // icmp (X+Y), (X+Z) -> icmp Y, Z for equalities or if there is no overflow. + if (A && C && (A == C || A == D || B == C || B == D) && + NoOp0WrapProblem && NoOp1WrapProblem && + // Try not to increase register pressure. + BO0->hasOneUse() && BO1->hasOneUse()) { + // Determine Y and Z in the form icmp (X+Y), (X+Z). + Value *Y, *Z; + if (A == C) { + // C + B == C + D -> B == D + Y = B; + Z = D; + } else if (A == D) { + // D + B == C + D -> B == C + Y = B; + Z = C; + } else if (B == C) { + // A + C == C + D -> A == D + Y = A; + Z = D; + } else { + assert(B == D); + // A + D == C + D -> A == C + Y = A; + Z = C; + } + return new ICmpInst(Pred, Y, Z); + } + + // icmp slt (X + -1), Y -> icmp sle X, Y + if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLT && + match(B, m_AllOnes())) + return new ICmpInst(CmpInst::ICMP_SLE, A, Op1); + + // icmp sge (X + -1), Y -> icmp sgt X, Y + if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGE && + match(B, m_AllOnes())) + return new ICmpInst(CmpInst::ICMP_SGT, A, Op1); + + // icmp sle (X + 1), Y -> icmp slt X, Y + if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SLE && + match(B, m_One())) + return new ICmpInst(CmpInst::ICMP_SLT, A, Op1); + + // icmp sgt (X + 1), Y -> icmp sge X, Y + if (A && NoOp0WrapProblem && Pred == CmpInst::ICMP_SGT && + match(B, m_One())) + return new ICmpInst(CmpInst::ICMP_SGE, A, Op1); + + // if C1 has greater magnitude than C2: + // icmp (X + C1), (Y + C2) -> icmp (X + C3), Y + // s.t. C3 = C1 - C2 + // + // if C2 has greater magnitude than C1: + // icmp (X + C1), (Y + C2) -> icmp X, (Y + C3) + // s.t. C3 = C2 - C1 + if (A && C && NoOp0WrapProblem && NoOp1WrapProblem && + (BO0->hasOneUse() || BO1->hasOneUse()) && !I.isUnsigned()) + if (ConstantInt *C1 = dyn_cast<ConstantInt>(B)) + if (ConstantInt *C2 = dyn_cast<ConstantInt>(D)) { + const APInt &AP1 = C1->getValue(); + const APInt &AP2 = C2->getValue(); + if (AP1.isNegative() == AP2.isNegative()) { + APInt AP1Abs = C1->getValue().abs(); + APInt AP2Abs = C2->getValue().abs(); + if (AP1Abs.uge(AP2Abs)) { + ConstantInt *C3 = Builder->getInt(AP1 - AP2); + Value *NewAdd = Builder->CreateNSWAdd(A, C3); + return new ICmpInst(Pred, NewAdd, C); + } else { + ConstantInt *C3 = Builder->getInt(AP2 - AP1); + Value *NewAdd = Builder->CreateNSWAdd(C, C3); + return new ICmpInst(Pred, A, NewAdd); + } + } + } + + + // Analyze the case when either Op0 or Op1 is a sub instruction. + // Op0 = A - B (or A and B are null); Op1 = C - D (or C and D are null). + A = nullptr; B = nullptr; C = nullptr; D = nullptr; + if (BO0 && BO0->getOpcode() == Instruction::Sub) + A = BO0->getOperand(0), B = BO0->getOperand(1); + if (BO1 && BO1->getOpcode() == Instruction::Sub) + C = BO1->getOperand(0), D = BO1->getOperand(1); + + // icmp (X-Y), X -> icmp 0, Y for equalities or if there is no overflow. + if (A == Op1 && NoOp0WrapProblem) + return new ICmpInst(Pred, Constant::getNullValue(Op1->getType()), B); + + // icmp X, (X-Y) -> icmp Y, 0 for equalities or if there is no overflow. + if (C == Op0 && NoOp1WrapProblem) + return new ICmpInst(Pred, D, Constant::getNullValue(Op0->getType())); + + // icmp (Y-X), (Z-X) -> icmp Y, Z for equalities or if there is no overflow. + if (B && D && B == D && NoOp0WrapProblem && NoOp1WrapProblem && + // Try not to increase register pressure. + BO0->hasOneUse() && BO1->hasOneUse()) + return new ICmpInst(Pred, A, C); + + // icmp (X-Y), (X-Z) -> icmp Z, Y for equalities or if there is no overflow. + if (A && C && A == C && NoOp0WrapProblem && NoOp1WrapProblem && + // Try not to increase register pressure. + BO0->hasOneUse() && BO1->hasOneUse()) + return new ICmpInst(Pred, D, B); + + // icmp (0-X) < cst --> x > -cst + if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) { + Value *X; + if (match(BO0, m_Neg(m_Value(X)))) + if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1)) + if (!RHSC->isMinValue(/*isSigned=*/true)) + return new ICmpInst(I.getSwappedPredicate(), X, + ConstantExpr::getNeg(RHSC)); + } + + BinaryOperator *SRem = nullptr; + // icmp (srem X, Y), Y + if (BO0 && BO0->getOpcode() == Instruction::SRem && + Op1 == BO0->getOperand(1)) + SRem = BO0; + // icmp Y, (srem X, Y) + else if (BO1 && BO1->getOpcode() == Instruction::SRem && + Op0 == BO1->getOperand(1)) + SRem = BO1; + if (SRem) { + // We don't check hasOneUse to avoid increasing register pressure because + // the value we use is the same value this instruction was already using. + switch (SRem == BO0 ? ICmpInst::getSwappedPredicate(Pred) : Pred) { + default: break; + case ICmpInst::ICMP_EQ: + return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType())); + case ICmpInst::ICMP_NE: + return ReplaceInstUsesWith(I, ConstantInt::getTrue(I.getType())); + case ICmpInst::ICMP_SGT: + case ICmpInst::ICMP_SGE: + return new ICmpInst(ICmpInst::ICMP_SGT, SRem->getOperand(1), + Constant::getAllOnesValue(SRem->getType())); + case ICmpInst::ICMP_SLT: + case ICmpInst::ICMP_SLE: + return new ICmpInst(ICmpInst::ICMP_SLT, SRem->getOperand(1), + Constant::getNullValue(SRem->getType())); + } + } + + if (BO0 && BO1 && BO0->getOpcode() == BO1->getOpcode() && + BO0->hasOneUse() && BO1->hasOneUse() && + BO0->getOperand(1) == BO1->getOperand(1)) { + switch (BO0->getOpcode()) { + default: break; + case Instruction::Add: + case Instruction::Sub: + case Instruction::Xor: + if (I.isEquality()) // a+x icmp eq/ne b+x --> a icmp b + return new ICmpInst(I.getPredicate(), BO0->getOperand(0), + BO1->getOperand(0)); + // icmp u/s (a ^ signbit), (b ^ signbit) --> icmp s/u a, b + if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) { + if (CI->getValue().isSignBit()) { + ICmpInst::Predicate Pred = I.isSigned() + ? I.getUnsignedPredicate() + : I.getSignedPredicate(); + return new ICmpInst(Pred, BO0->getOperand(0), + BO1->getOperand(0)); + } + + if (CI->isMaxValue(true)) { + ICmpInst::Predicate Pred = I.isSigned() + ? I.getUnsignedPredicate() + : I.getSignedPredicate(); + Pred = I.getSwappedPredicate(Pred); + return new ICmpInst(Pred, BO0->getOperand(0), + BO1->getOperand(0)); + } + } + break; + case Instruction::Mul: + if (!I.isEquality()) + break; + + if (ConstantInt *CI = dyn_cast<ConstantInt>(BO0->getOperand(1))) { + // a * Cst icmp eq/ne b * Cst --> a & Mask icmp b & Mask + // Mask = -1 >> count-trailing-zeros(Cst). + if (!CI->isZero() && !CI->isOne()) { + const APInt &AP = CI->getValue(); + ConstantInt *Mask = ConstantInt::get(I.getContext(), + APInt::getLowBitsSet(AP.getBitWidth(), + AP.getBitWidth() - + AP.countTrailingZeros())); + Value *And1 = Builder->CreateAnd(BO0->getOperand(0), Mask); + Value *And2 = Builder->CreateAnd(BO1->getOperand(0), Mask); + return new ICmpInst(I.getPredicate(), And1, And2); + } + } + break; + case Instruction::UDiv: + case Instruction::LShr: + if (I.isSigned()) + break; + // fall-through + case Instruction::SDiv: + case Instruction::AShr: + if (!BO0->isExact() || !BO1->isExact()) + break; + return new ICmpInst(I.getPredicate(), BO0->getOperand(0), + BO1->getOperand(0)); + case Instruction::Shl: { + bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap(); + bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap(); + if (!NUW && !NSW) + break; + if (!NSW && I.isSigned()) + break; + return new ICmpInst(I.getPredicate(), BO0->getOperand(0), + BO1->getOperand(0)); + } + } + } + } + + { Value *A, *B; + // Transform (A & ~B) == 0 --> (A & B) != 0 + // and (A & ~B) != 0 --> (A & B) == 0 + // if A is a power of 2. + if (match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) && + match(Op1, m_Zero()) && + isKnownToBeAPowerOfTwo(A, DL, false, 0, AC, &I, DT) && I.isEquality()) + return new ICmpInst(I.getInversePredicate(), + Builder->CreateAnd(A, B), + Op1); + + // ~x < ~y --> y < x + // ~x < cst --> ~cst < x + if (match(Op0, m_Not(m_Value(A)))) { + if (match(Op1, m_Not(m_Value(B)))) + return new ICmpInst(I.getPredicate(), B, A); + if (ConstantInt *RHSC = dyn_cast<ConstantInt>(Op1)) + return new ICmpInst(I.getPredicate(), ConstantExpr::getNot(RHSC), A); + } + + Instruction *AddI = nullptr; + if (match(&I, m_UAddWithOverflow(m_Value(A), m_Value(B), + m_Instruction(AddI))) && + isa<IntegerType>(A->getType())) { + Value *Result; + Constant *Overflow; + if (OptimizeOverflowCheck(OCF_UNSIGNED_ADD, A, B, *AddI, Result, + Overflow)) { + ReplaceInstUsesWith(*AddI, Result); + return ReplaceInstUsesWith(I, Overflow); + } + } + + // (zext a) * (zext b) --> llvm.umul.with.overflow. + if (match(Op0, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) { + if (Instruction *R = ProcessUMulZExtIdiom(I, Op0, Op1, *this)) + return R; + } + if (match(Op1, m_Mul(m_ZExt(m_Value(A)), m_ZExt(m_Value(B))))) { + if (Instruction *R = ProcessUMulZExtIdiom(I, Op1, Op0, *this)) + return R; + } + } + + if (I.isEquality()) { + Value *A, *B, *C, *D; + + if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) { + if (A == Op1 || B == Op1) { // (A^B) == A -> B == 0 + Value *OtherVal = A == Op1 ? B : A; + return new ICmpInst(I.getPredicate(), OtherVal, + Constant::getNullValue(A->getType())); + } + + if (match(Op1, m_Xor(m_Value(C), m_Value(D)))) { + // A^c1 == C^c2 --> A == C^(c1^c2) + ConstantInt *C1, *C2; + if (match(B, m_ConstantInt(C1)) && + match(D, m_ConstantInt(C2)) && Op1->hasOneUse()) { + Constant *NC = Builder->getInt(C1->getValue() ^ C2->getValue()); + Value *Xor = Builder->CreateXor(C, NC); + return new ICmpInst(I.getPredicate(), A, Xor); + } + + // A^B == A^D -> B == D + if (A == C) return new ICmpInst(I.getPredicate(), B, D); + if (A == D) return new ICmpInst(I.getPredicate(), B, C); + if (B == C) return new ICmpInst(I.getPredicate(), A, D); + if (B == D) return new ICmpInst(I.getPredicate(), A, C); + } + } + + if (match(Op1, m_Xor(m_Value(A), m_Value(B))) && + (A == Op0 || B == Op0)) { + // A == (A^B) -> B == 0 + Value *OtherVal = A == Op0 ? B : A; + return new ICmpInst(I.getPredicate(), OtherVal, + Constant::getNullValue(A->getType())); + } + + // (X&Z) == (Y&Z) -> (X^Y) & Z == 0 + if (match(Op0, m_OneUse(m_And(m_Value(A), m_Value(B)))) && + match(Op1, m_OneUse(m_And(m_Value(C), m_Value(D))))) { + Value *X = nullptr, *Y = nullptr, *Z = nullptr; + + if (A == C) { + X = B; Y = D; Z = A; + } else if (A == D) { + X = B; Y = C; Z = A; + } else if (B == C) { + X = A; Y = D; Z = B; + } else if (B == D) { + X = A; Y = C; Z = B; + } + + if (X) { // Build (X^Y) & Z + Op1 = Builder->CreateXor(X, Y); + Op1 = Builder->CreateAnd(Op1, Z); + I.setOperand(0, Op1); + I.setOperand(1, Constant::getNullValue(Op1->getType())); + return &I; + } + } + + // Transform (zext A) == (B & (1<<X)-1) --> A == (trunc B) + // and (B & (1<<X)-1) == (zext A) --> A == (trunc B) + ConstantInt *Cst1; + if ((Op0->hasOneUse() && + match(Op0, m_ZExt(m_Value(A))) && + match(Op1, m_And(m_Value(B), m_ConstantInt(Cst1)))) || + (Op1->hasOneUse() && + match(Op0, m_And(m_Value(B), m_ConstantInt(Cst1))) && + match(Op1, m_ZExt(m_Value(A))))) { + APInt Pow2 = Cst1->getValue() + 1; + if (Pow2.isPowerOf2() && isa<IntegerType>(A->getType()) && + Pow2.logBase2() == cast<IntegerType>(A->getType())->getBitWidth()) + return new ICmpInst(I.getPredicate(), A, + Builder->CreateTrunc(B, A->getType())); + } + + // (A >> C) == (B >> C) --> (A^B) u< (1 << C) + // For lshr and ashr pairs. + if ((match(Op0, m_OneUse(m_LShr(m_Value(A), m_ConstantInt(Cst1)))) && + match(Op1, m_OneUse(m_LShr(m_Value(B), m_Specific(Cst1))))) || + (match(Op0, m_OneUse(m_AShr(m_Value(A), m_ConstantInt(Cst1)))) && + match(Op1, m_OneUse(m_AShr(m_Value(B), m_Specific(Cst1)))))) { + unsigned TypeBits = Cst1->getBitWidth(); + unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits); + if (ShAmt < TypeBits && ShAmt != 0) { + ICmpInst::Predicate Pred = I.getPredicate() == ICmpInst::ICMP_NE + ? ICmpInst::ICMP_UGE + : ICmpInst::ICMP_ULT; + Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted"); + APInt CmpVal = APInt::getOneBitSet(TypeBits, ShAmt); + return new ICmpInst(Pred, Xor, Builder->getInt(CmpVal)); + } + } + + // (A << C) == (B << C) --> ((A^B) & (~0U >> C)) == 0 + if (match(Op0, m_OneUse(m_Shl(m_Value(A), m_ConstantInt(Cst1)))) && + match(Op1, m_OneUse(m_Shl(m_Value(B), m_Specific(Cst1))))) { + unsigned TypeBits = Cst1->getBitWidth(); + unsigned ShAmt = (unsigned)Cst1->getLimitedValue(TypeBits); + if (ShAmt < TypeBits && ShAmt != 0) { + Value *Xor = Builder->CreateXor(A, B, I.getName() + ".unshifted"); + APInt AndVal = APInt::getLowBitsSet(TypeBits, TypeBits - ShAmt); + Value *And = Builder->CreateAnd(Xor, Builder->getInt(AndVal), + I.getName() + ".mask"); + return new ICmpInst(I.getPredicate(), And, + Constant::getNullValue(Cst1->getType())); + } + } + + // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to + // "icmp (and X, mask), cst" + uint64_t ShAmt = 0; + if (Op0->hasOneUse() && + match(Op0, m_Trunc(m_OneUse(m_LShr(m_Value(A), + m_ConstantInt(ShAmt))))) && + match(Op1, m_ConstantInt(Cst1)) && + // Only do this when A has multiple uses. This is most important to do + // when it exposes other optimizations. + !A->hasOneUse()) { + unsigned ASize =cast<IntegerType>(A->getType())->getPrimitiveSizeInBits(); + + if (ShAmt < ASize) { + APInt MaskV = + APInt::getLowBitsSet(ASize, Op0->getType()->getPrimitiveSizeInBits()); + MaskV <<= ShAmt; + + APInt CmpV = Cst1->getValue().zext(ASize); + CmpV <<= ShAmt; + + Value *Mask = Builder->CreateAnd(A, Builder->getInt(MaskV)); + return new ICmpInst(I.getPredicate(), Mask, Builder->getInt(CmpV)); + } + } + } + + // The 'cmpxchg' instruction returns an aggregate containing the old value and + // an i1 which indicates whether or not we successfully did the swap. + // + // Replace comparisons between the old value and the expected value with the + // indicator that 'cmpxchg' returns. + // + // N.B. This transform is only valid when the 'cmpxchg' is not permitted to + // spuriously fail. In those cases, the old value may equal the expected + // value but it is possible for the swap to not occur. + if (I.getPredicate() == ICmpInst::ICMP_EQ) + if (auto *EVI = dyn_cast<ExtractValueInst>(Op0)) + if (auto *ACXI = dyn_cast<AtomicCmpXchgInst>(EVI->getAggregateOperand())) + if (EVI->getIndices()[0] == 0 && ACXI->getCompareOperand() == Op1 && + !ACXI->isWeak()) + return ExtractValueInst::Create(ACXI, 1); + + { + Value *X; ConstantInt *Cst; + // icmp X+Cst, X + if (match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op1 == X) + return FoldICmpAddOpCst(I, X, Cst, I.getPredicate()); + + // icmp X, X+Cst + if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X) + return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate()); + } + return Changed ? &I : nullptr; +} + +/// FoldFCmp_IntToFP_Cst - Fold fcmp ([us]itofp x, cst) if possible. +Instruction *InstCombiner::FoldFCmp_IntToFP_Cst(FCmpInst &I, + Instruction *LHSI, + Constant *RHSC) { + if (!isa<ConstantFP>(RHSC)) return nullptr; + const APFloat &RHS = cast<ConstantFP>(RHSC)->getValueAPF(); + + // Get the width of the mantissa. We don't want to hack on conversions that + // might lose information from the integer, e.g. "i64 -> float" + int MantissaWidth = LHSI->getType()->getFPMantissaWidth(); + if (MantissaWidth == -1) return nullptr; // Unknown. + + IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType()); + + // Check to see that the input is converted from an integer type that is small + // enough that preserves all bits. TODO: check here for "known" sign bits. + // This would allow us to handle (fptosi (x >>s 62) to float) if x is i64 f.e. + unsigned InputSize = IntTy->getScalarSizeInBits(); + + // If this is a uitofp instruction, we need an extra bit to hold the sign. + bool LHSUnsigned = isa<UIToFPInst>(LHSI); + if (LHSUnsigned) + ++InputSize; + + if (I.isEquality()) { + FCmpInst::Predicate P = I.getPredicate(); + bool IsExact = false; + APSInt RHSCvt(IntTy->getBitWidth(), LHSUnsigned); + RHS.convertToInteger(RHSCvt, APFloat::rmNearestTiesToEven, &IsExact); + + // If the floating point constant isn't an integer value, we know if we will + // ever compare equal / not equal to it. + if (!IsExact) { + // TODO: Can never be -0.0 and other non-representable values + APFloat RHSRoundInt(RHS); + RHSRoundInt.roundToIntegral(APFloat::rmNearestTiesToEven); + if (RHS.compare(RHSRoundInt) != APFloat::cmpEqual) { + if (P == FCmpInst::FCMP_OEQ || P == FCmpInst::FCMP_UEQ) + return ReplaceInstUsesWith(I, Builder->getFalse()); + + assert(P == FCmpInst::FCMP_ONE || P == FCmpInst::FCMP_UNE); + return ReplaceInstUsesWith(I, Builder->getTrue()); + } + } + + // TODO: If the constant is exactly representable, is it always OK to do + // equality compares as integer? + } + + // Comparisons with zero are a special case where we know we won't lose + // information. + bool IsCmpZero = RHS.isPosZero(); + + // If the conversion would lose info, don't hack on this. + if ((int)InputSize > MantissaWidth && !IsCmpZero) + return nullptr; + + // Otherwise, we can potentially simplify the comparison. We know that it + // will always come through as an integer value and we know the constant is + // not a NAN (it would have been previously simplified). + assert(!RHS.isNaN() && "NaN comparison not already folded!"); + + ICmpInst::Predicate Pred; + switch (I.getPredicate()) { + default: llvm_unreachable("Unexpected predicate!"); + case FCmpInst::FCMP_UEQ: + case FCmpInst::FCMP_OEQ: + Pred = ICmpInst::ICMP_EQ; + break; + case FCmpInst::FCMP_UGT: + case FCmpInst::FCMP_OGT: + Pred = LHSUnsigned ? ICmpInst::ICMP_UGT : ICmpInst::ICMP_SGT; + break; + case FCmpInst::FCMP_UGE: + case FCmpInst::FCMP_OGE: + Pred = LHSUnsigned ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_SGE; + break; + case FCmpInst::FCMP_ULT: + case FCmpInst::FCMP_OLT: + Pred = LHSUnsigned ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_SLT; + break; + case FCmpInst::FCMP_ULE: + case FCmpInst::FCMP_OLE: + Pred = LHSUnsigned ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_SLE; + break; + case FCmpInst::FCMP_UNE: + case FCmpInst::FCMP_ONE: + Pred = ICmpInst::ICMP_NE; + break; + case FCmpInst::FCMP_ORD: + return ReplaceInstUsesWith(I, Builder->getTrue()); + case FCmpInst::FCMP_UNO: + return ReplaceInstUsesWith(I, Builder->getFalse()); + } + + // Now we know that the APFloat is a normal number, zero or inf. + + // See if the FP constant is too large for the integer. For example, + // comparing an i8 to 300.0. + unsigned IntWidth = IntTy->getScalarSizeInBits(); + + if (!LHSUnsigned) { + // If the RHS value is > SignedMax, fold the comparison. This handles +INF + // and large values. + APFloat SMax(RHS.getSemantics()); + SMax.convertFromAPInt(APInt::getSignedMaxValue(IntWidth), true, + APFloat::rmNearestTiesToEven); + if (SMax.compare(RHS) == APFloat::cmpLessThan) { // smax < 13123.0 + if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SLT || + Pred == ICmpInst::ICMP_SLE) + return ReplaceInstUsesWith(I, Builder->getTrue()); + return ReplaceInstUsesWith(I, Builder->getFalse()); + } + } else { + // If the RHS value is > UnsignedMax, fold the comparison. This handles + // +INF and large values. + APFloat UMax(RHS.getSemantics()); + UMax.convertFromAPInt(APInt::getMaxValue(IntWidth), false, + APFloat::rmNearestTiesToEven); + if (UMax.compare(RHS) == APFloat::cmpLessThan) { // umax < 13123.0 + if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_ULT || + Pred == ICmpInst::ICMP_ULE) + return ReplaceInstUsesWith(I, Builder->getTrue()); + return ReplaceInstUsesWith(I, Builder->getFalse()); + } + } + + if (!LHSUnsigned) { + // See if the RHS value is < SignedMin. + APFloat SMin(RHS.getSemantics()); + SMin.convertFromAPInt(APInt::getSignedMinValue(IntWidth), true, + APFloat::rmNearestTiesToEven); + if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // smin > 12312.0 + if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_SGT || + Pred == ICmpInst::ICMP_SGE) + return ReplaceInstUsesWith(I, Builder->getTrue()); + return ReplaceInstUsesWith(I, Builder->getFalse()); + } + } else { + // See if the RHS value is < UnsignedMin. + APFloat SMin(RHS.getSemantics()); + SMin.convertFromAPInt(APInt::getMinValue(IntWidth), true, + APFloat::rmNearestTiesToEven); + if (SMin.compare(RHS) == APFloat::cmpGreaterThan) { // umin > 12312.0 + if (Pred == ICmpInst::ICMP_NE || Pred == ICmpInst::ICMP_UGT || + Pred == ICmpInst::ICMP_UGE) + return ReplaceInstUsesWith(I, Builder->getTrue()); + return ReplaceInstUsesWith(I, Builder->getFalse()); + } + } + + // Okay, now we know that the FP constant fits in the range [SMIN, SMAX] or + // [0, UMAX], but it may still be fractional. See if it is fractional by + // casting the FP value to the integer value and back, checking for equality. + // Don't do this for zero, because -0.0 is not fractional. + Constant *RHSInt = LHSUnsigned + ? ConstantExpr::getFPToUI(RHSC, IntTy) + : ConstantExpr::getFPToSI(RHSC, IntTy); + if (!RHS.isZero()) { + bool Equal = LHSUnsigned + ? ConstantExpr::getUIToFP(RHSInt, RHSC->getType()) == RHSC + : ConstantExpr::getSIToFP(RHSInt, RHSC->getType()) == RHSC; + if (!Equal) { + // If we had a comparison against a fractional value, we have to adjust + // the compare predicate and sometimes the value. RHSC is rounded towards + // zero at this point. + switch (Pred) { + default: llvm_unreachable("Unexpected integer comparison!"); + case ICmpInst::ICMP_NE: // (float)int != 4.4 --> true + return ReplaceInstUsesWith(I, Builder->getTrue()); + case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false + return ReplaceInstUsesWith(I, Builder->getFalse()); + case ICmpInst::ICMP_ULE: + // (float)int <= 4.4 --> int <= 4 + // (float)int <= -4.4 --> false + if (RHS.isNegative()) + return ReplaceInstUsesWith(I, Builder->getFalse()); + break; + case ICmpInst::ICMP_SLE: + // (float)int <= 4.4 --> int <= 4 + // (float)int <= -4.4 --> int < -4 + if (RHS.isNegative()) + Pred = ICmpInst::ICMP_SLT; + break; + case ICmpInst::ICMP_ULT: + // (float)int < -4.4 --> false + // (float)int < 4.4 --> int <= 4 + if (RHS.isNegative()) + return ReplaceInstUsesWith(I, Builder->getFalse()); + Pred = ICmpInst::ICMP_ULE; + break; + case ICmpInst::ICMP_SLT: + // (float)int < -4.4 --> int < -4 + // (float)int < 4.4 --> int <= 4 + if (!RHS.isNegative()) + Pred = ICmpInst::ICMP_SLE; + break; + case ICmpInst::ICMP_UGT: + // (float)int > 4.4 --> int > 4 + // (float)int > -4.4 --> true + if (RHS.isNegative()) + return ReplaceInstUsesWith(I, Builder->getTrue()); + break; + case ICmpInst::ICMP_SGT: + // (float)int > 4.4 --> int > 4 + // (float)int > -4.4 --> int >= -4 + if (RHS.isNegative()) + Pred = ICmpInst::ICMP_SGE; + break; + case ICmpInst::ICMP_UGE: + // (float)int >= -4.4 --> true + // (float)int >= 4.4 --> int > 4 + if (RHS.isNegative()) + return ReplaceInstUsesWith(I, Builder->getTrue()); + Pred = ICmpInst::ICMP_UGT; + break; + case ICmpInst::ICMP_SGE: + // (float)int >= -4.4 --> int >= -4 + // (float)int >= 4.4 --> int > 4 + if (!RHS.isNegative()) + Pred = ICmpInst::ICMP_SGT; + break; + } + } + } + + // Lower this FP comparison into an appropriate integer version of the + // comparison. + return new ICmpInst(Pred, LHSI->getOperand(0), RHSInt); +} + +Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) { + bool Changed = false; + + /// Orders the operands of the compare so that they are listed from most + /// complex to least complex. This puts constants before unary operators, + /// before binary operators. + if (getComplexity(I.getOperand(0)) < getComplexity(I.getOperand(1))) { + I.swapOperands(); + Changed = true; + } + + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyFCmpInst(I.getPredicate(), Op0, Op1, DL, TLI, DT, AC)) + return ReplaceInstUsesWith(I, V); + + // Simplify 'fcmp pred X, X' + if (Op0 == Op1) { + switch (I.getPredicate()) { + default: llvm_unreachable("Unknown predicate!"); + case FCmpInst::FCMP_UNO: // True if unordered: isnan(X) | isnan(Y) + case FCmpInst::FCMP_ULT: // True if unordered or less than + case FCmpInst::FCMP_UGT: // True if unordered or greater than + case FCmpInst::FCMP_UNE: // True if unordered or not equal + // Canonicalize these to be 'fcmp uno %X, 0.0'. + I.setPredicate(FCmpInst::FCMP_UNO); + I.setOperand(1, Constant::getNullValue(Op0->getType())); + return &I; + + case FCmpInst::FCMP_ORD: // True if ordered (no nans) + case FCmpInst::FCMP_OEQ: // True if ordered and equal + case FCmpInst::FCMP_OGE: // True if ordered and greater than or equal + case FCmpInst::FCMP_OLE: // True if ordered and less than or equal + // Canonicalize these to be 'fcmp ord %X, 0.0'. + I.setPredicate(FCmpInst::FCMP_ORD); + I.setOperand(1, Constant::getNullValue(Op0->getType())); + return &I; + } + } + + // Test if the FCmpInst instruction is used exclusively by a select as + // part of a minimum or maximum operation. If so, refrain from doing + // any other folding. This helps out other analyses which understand + // non-obfuscated minimum and maximum idioms, such as ScalarEvolution + // and CodeGen. And in this case, at least one of the comparison + // operands has at least one user besides the compare (the select), + // which would often largely negate the benefit of folding anyway. + if (I.hasOneUse()) + if (SelectInst *SI = dyn_cast<SelectInst>(*I.user_begin())) + if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || + (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) + return nullptr; + + // Handle fcmp with constant RHS + if (Constant *RHSC = dyn_cast<Constant>(Op1)) { + if (Instruction *LHSI = dyn_cast<Instruction>(Op0)) + switch (LHSI->getOpcode()) { + case Instruction::FPExt: { + // fcmp (fpext x), C -> fcmp x, (fptrunc C) if fptrunc is lossless + FPExtInst *LHSExt = cast<FPExtInst>(LHSI); + ConstantFP *RHSF = dyn_cast<ConstantFP>(RHSC); + if (!RHSF) + break; + + const fltSemantics *Sem; + // FIXME: This shouldn't be here. + if (LHSExt->getSrcTy()->isHalfTy()) + Sem = &APFloat::IEEEhalf; + else if (LHSExt->getSrcTy()->isFloatTy()) + Sem = &APFloat::IEEEsingle; + else if (LHSExt->getSrcTy()->isDoubleTy()) + Sem = &APFloat::IEEEdouble; + else if (LHSExt->getSrcTy()->isFP128Ty()) + Sem = &APFloat::IEEEquad; + else if (LHSExt->getSrcTy()->isX86_FP80Ty()) + Sem = &APFloat::x87DoubleExtended; + else if (LHSExt->getSrcTy()->isPPC_FP128Ty()) + Sem = &APFloat::PPCDoubleDouble; + else + break; + + bool Lossy; + APFloat F = RHSF->getValueAPF(); + F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy); + + // Avoid lossy conversions and denormals. Zero is a special case + // that's OK to convert. + APFloat Fabs = F; + Fabs.clearSign(); + if (!Lossy && + ((Fabs.compare(APFloat::getSmallestNormalized(*Sem)) != + APFloat::cmpLessThan) || Fabs.isZero())) + + return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0), + ConstantFP::get(RHSC->getContext(), F)); + break; + } + case Instruction::PHI: + // Only fold fcmp into the PHI if the phi and fcmp are in the same + // block. If in the same block, we're encouraging jump threading. If + // not, we are just pessimizing the code by making an i1 phi. + if (LHSI->getParent() == I.getParent()) + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + break; + case Instruction::SIToFP: + case Instruction::UIToFP: + if (Instruction *NV = FoldFCmp_IntToFP_Cst(I, LHSI, RHSC)) + return NV; + break; + case Instruction::FSub: { + // fcmp pred (fneg x), C -> fcmp swap(pred) x, -C + Value *Op; + if (match(LHSI, m_FNeg(m_Value(Op)))) + return new FCmpInst(I.getSwappedPredicate(), Op, + ConstantExpr::getFNeg(RHSC)); + break; + } + case Instruction::Load: + if (GetElementPtrInst *GEP = + dyn_cast<GetElementPtrInst>(LHSI->getOperand(0))) { + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0))) + if (GV->isConstant() && GV->hasDefinitiveInitializer() && + !cast<LoadInst>(LHSI)->isVolatile()) + if (Instruction *Res = FoldCmpLoadFromIndexedGlobal(GEP, GV, I)) + return Res; + } + break; + case Instruction::Call: { + if (!RHSC->isNullValue()) + break; + + CallInst *CI = cast<CallInst>(LHSI); + const Function *F = CI->getCalledFunction(); + if (!F) + break; + + // Various optimization for fabs compared with zero. + LibFunc::Func Func; + if (F->getIntrinsicID() == Intrinsic::fabs || + (TLI->getLibFunc(F->getName(), Func) && TLI->has(Func) && + (Func == LibFunc::fabs || Func == LibFunc::fabsf || + Func == LibFunc::fabsl))) { + switch (I.getPredicate()) { + default: + break; + // fabs(x) < 0 --> false + case FCmpInst::FCMP_OLT: + return ReplaceInstUsesWith(I, Builder->getFalse()); + // fabs(x) > 0 --> x != 0 + case FCmpInst::FCMP_OGT: + return new FCmpInst(FCmpInst::FCMP_ONE, CI->getArgOperand(0), RHSC); + // fabs(x) <= 0 --> x == 0 + case FCmpInst::FCMP_OLE: + return new FCmpInst(FCmpInst::FCMP_OEQ, CI->getArgOperand(0), RHSC); + // fabs(x) >= 0 --> !isnan(x) + case FCmpInst::FCMP_OGE: + return new FCmpInst(FCmpInst::FCMP_ORD, CI->getArgOperand(0), RHSC); + // fabs(x) == 0 --> x == 0 + // fabs(x) != 0 --> x != 0 + case FCmpInst::FCMP_OEQ: + case FCmpInst::FCMP_UEQ: + case FCmpInst::FCMP_ONE: + case FCmpInst::FCMP_UNE: + return new FCmpInst(I.getPredicate(), CI->getArgOperand(0), RHSC); + } + } + } + } + } + + // fcmp pred (fneg x), (fneg y) -> fcmp swap(pred) x, y + Value *X, *Y; + if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y)))) + return new FCmpInst(I.getSwappedPredicate(), X, Y); + + // fcmp (fpext x), (fpext y) -> fcmp x, y + if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0)) + if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1)) + if (LHSExt->getSrcTy() == RHSExt->getSrcTy()) + return new FCmpInst(I.getPredicate(), LHSExt->getOperand(0), + RHSExt->getOperand(0)); + + return Changed ? &I : nullptr; +} |
