| //===- 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 "InstCombine.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Support/ConstantRange.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/PatternMatch.h" |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| static ConstantInt *getOne(Constant *C) { |
| return ConstantInt::get(cast<IntegerType>(C->getType()), 1); |
| } |
| |
| /// AddOne - Add one to a ConstantInt |
| static Constant *AddOne(Constant *C) { |
| return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1)); |
| } |
| /// SubOne - Subtract one from a ConstantInt |
| static Constant *SubOne(Constant *C) { |
| return ConstantExpr::getSub(C, ConstantInt::get(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) |
| if (In2->getValue().isNegative()) |
| return Result->getValue().sgt(In1->getValue()); |
| else |
| return Result->getValue().slt(In1->getValue()); |
| else |
| return Result->getValue().ult(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 (const 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) |
| if (In2->getValue().isNegative()) |
| return Result->getValue().slt(In1->getValue()); |
| else |
| return Result->getValue().sgt(In1->getValue()); |
| else |
| return Result->getValue().ugt(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 (const 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->getValue() == |
| APInt::getSignedMaxValue(RHS->getType()->getPrimitiveSizeInBits()); |
| 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; |
| } |
| } |
| |
| // 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) { |
| // We need TD information to know the pointer size unless this is inbounds. |
| if (!GEP->isInBounds() && TD == 0) return 0; |
| |
| ConstantArray *Init = dyn_cast<ConstantArray>(GV->getInitializer()); |
| if (Init == 0 || Init->getNumOperands() > 1024) return 0; |
| |
| // 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 0; |
| |
| // 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; |
| |
| const Type *EltTy = cast<ArrayType>(Init->getType())->getElementType(); |
| for (unsigned i = 3, e = GEP->getNumOperands(); i != e; ++i) { |
| ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i)); |
| if (Idx == 0) return 0; // Variable index. |
| |
| uint64_t IdxVal = Idx->getZExtValue(); |
| if ((unsigned)IdxVal != IdxVal) return 0; // Too large array index. |
| |
| if (const StructType *STy = dyn_cast<StructType>(EltTy)) |
| EltTy = STy->getElementType(IdxVal); |
| else if (const ArrayType *ATy = dyn_cast<ArrayType>(EltTy)) { |
| if (IdxVal >= ATy->getNumElements()) return 0; |
| EltTy = ATy->getElementType(); |
| } else { |
| return 0; // 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 = Init->getNumOperands(); i != e; ++i) { |
| Constant *Elt = Init->getOperand(i); |
| |
| // If this is indexing an array of structures, get the structure element. |
| if (!LaterIndices.empty()) |
| Elt = ConstantExpr::getExtractValue(Elt, LaterIndices.data(), |
| LaterIndices.size()); |
| |
| // 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, TD); |
| // 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 0; |
| |
| // 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 0; |
| } |
| |
| // 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() && |
| Idx->getType()->getPrimitiveSizeInBits() > TD->getPointerSizeInBits()) |
| Idx = Builder->CreateTrunc(Idx, TD->getIntPtrType(Idx->getContext())); |
| |
| // 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, ConstantInt::getFalse(GEP->getContext())); |
| |
| 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, ConstantInt::getTrue(GEP->getContext())); |
| |
| 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 32-bit or 64-bit magic bitvector captures the entire comparison state |
| // of this load, replace it with computation that does: |
| // ((magic_cst >> i) & 1) != 0 |
| if (Init->getNumOperands() <= 32 || |
| (TD && Init->getNumOperands() <= 64 && TD->isLegalInteger(64))) { |
| const Type *Ty; |
| if (Init->getNumOperands() <= 32) |
| Ty = Type::getInt32Ty(Init->getContext()); |
| else |
| Ty = Type::getInt64Ty(Init->getContext()); |
| 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 0; |
| } |
| |
| |
| /// 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) { |
| TargetData &TD = *IC.getTargetData(); |
| 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 (const StructType *STy = dyn_cast<StructType>(*GTI)) { |
| Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); |
| } else { |
| uint64_t Size = TD.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 0; |
| |
| 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 = TD.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 0; |
| |
| // Compute the aggregate offset of constant indices. |
| if (CI->isZero()) continue; |
| |
| // Handle a struct index, which adds its field offset to the pointer. |
| if (const StructType *STy = dyn_cast<StructType>(*GTI)) { |
| Offset += TD.getStructLayout(STy)->getElementOffset(CI->getZExtValue()); |
| } else { |
| uint64_t Size = TD.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. |
| unsigned IntPtrWidth = TD.getPointerSizeInBits(); |
| 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) { |
| const Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext()); |
| 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 0; |
| |
| // Okay, we can do this evaluation. Start by converting the index to intptr. |
| const Type *IntPtrTy = TD.getIntPtrType(VariableIdx->getContext()); |
| 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) { |
| // Look through bitcasts. |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(RHS)) |
| RHS = BCI->getOperand(0); |
| |
| Value *PtrBase = GEPLHS->getOperand(0); |
| if (TD && 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); |
| |
| // If not, synthesize the offset the hard way. |
| if (Offset == 0) |
| 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(ICmpInst::getSignedPredicate(Cond), |
| GEPLHS->getOperand(0), GEPRHS->getOperand(0)); |
| |
| // Otherwise, the base pointers are different and the indices are |
| // different, bail out. |
| return 0; |
| } |
| |
| // If one of the GEPs has all zero indices, recurse. |
| bool AllZeros = true; |
| for (unsigned i = 1, e = GEPLHS->getNumOperands(); i != e; ++i) |
| if (!isa<Constant>(GEPLHS->getOperand(i)) || |
| !cast<Constant>(GEPLHS->getOperand(i))->isNullValue()) { |
| AllZeros = false; |
| break; |
| } |
| if (AllZeros) |
| return FoldGEPICmp(GEPRHS, GEPLHS->getOperand(0), |
| ICmpInst::getSwappedPredicate(Cond), I); |
| |
| // If the other GEP has all zero indices, recurse. |
| AllZeros = true; |
| for (unsigned i = 1, e = GEPRHS->getNumOperands(); i != e; ++i) |
| if (!isa<Constant>(GEPRHS->getOperand(i)) || |
| !cast<Constant>(GEPRHS->getOperand(i))->isNullValue()) { |
| AllZeros = false; |
| break; |
| } |
| if (AllZeros) |
| 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. |
| ConstantInt::get(Type::getInt1Ty(I.getContext()), |
| 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 (TD && |
| 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 0; |
| } |
| |
| /// FoldICmpAddOpCst - Fold "icmp pred (X+CI), X". |
| Instruction *InstCombiner::FoldICmpAddOpCst(ICmpInst &ICI, |
| Value *X, ConstantInt *CI, |
| ICmpInst::Predicate Pred, |
| Value *TheAdd) { |
| // If we have X+0, exit early (simplifying logic below) and let it get folded |
| // elsewhere. icmp X+0, X -> icmp X, X |
| if (CI->isZero()) { |
| bool isTrue = ICmpInst::isTrueWhenEqual(Pred); |
| return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); |
| } |
| |
| // (X+4) == X -> false. |
| if (Pred == ICmpInst::ICMP_EQ) |
| return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); |
| |
| // (X+4) != X -> true. |
| if (Pred == ICmpInst::ICMP_NE) |
| return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); |
| |
| // 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 = ConstantInt::get(X->getContext(), 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 0; |
| if (DivRHS->isZero()) |
| return 0; // The ProdOV computation fails on divide by zero. |
| if (DivIsSigned && DivRHS->isAllOnesValue()) |
| return 0; // 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 = 0, *HiBound = 0; |
| |
| 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->getValue().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 = 0; // 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, ConstantInt::getFalse(ICI.getContext())); |
| 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, ConstantInt::getTrue(ICI.getContext())); |
| 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, ConstantInt::getTrue(ICI.getContext())); |
| if (LoOverflow == -1) // Low bound is less than input range. |
| return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(ICI.getContext())); |
| 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, ConstantInt::getFalse(ICI.getContext())); |
| if (HiOverflow == -1) // High bound less than input range. |
| return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(ICI.getContext())); |
| 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 0; |
| |
| 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 0; |
| |
| // 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 0; |
| |
| // 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 == 0) |
| 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 = ConstantInt::get(ICI.getContext(), 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 = ConstantInt::get(Type::getInt1Ty(ICI.getContext()), |
| 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 = ConstantInt::get(ICI.getContext(), Val); |
| |
| Value *And = Builder->CreateAnd(Shr->getOperand(0), |
| Mask, Shr->getName()+".mask"); |
| return new ICmpInst(ICI.getPredicate(), And, ShiftedCmpRHS); |
| } |
| return 0; |
| } |
| |
| |
| /// 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 Mask(APInt::getHighBitsSet(SrcBits, SrcBits-DstBits)); |
| APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0); |
| ComputeMaskedBits(LHSI->getOperand(0), Mask, KnownZero, KnownOne); |
| |
| // 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; |
| return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0), |
| ConstantInt::get(ICI.getContext(), 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->getValue().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), |
| ConstantInt::get(ICI.getContext(), |
| RHSV ^ SignBit)); |
| } |
| |
| // (icmp u/s (xor A ~SignBit), C) -> (icmp s/u (xor C ~SignBit), A) |
| if (!ICI.isEquality() && XorCST->getValue().isMaxSignedValue()) { |
| 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), |
| ConstantInt::get(ICI.getContext(), |
| RHSV ^ NotSignBit)); |
| } |
| } |
| } |
| 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->getValue().isNonNegative() && 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))) { |
| const 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 = 0; |
| |
| ConstantInt *ShAmt; |
| ShAmt = Shift ? dyn_cast<ConstantInt>(Shift->getOperand(1)) : 0; |
| const Type *Ty = Shift ? Shift->getType() : 0; // Type of the shift. |
| const Type *AndTy = AndCST->getType(); // Type of the and. |
| |
| // We can fold this as long as we can't shift unknown bits |
| // into the mask. This can only happen with signed shift |
| // rights, as they sign-extend. |
| if (ShAmt) { |
| bool CanFold = Shift->isLogicalShift(); |
| if (!CanFold) { |
| // To test for the bad case of the signed shr, see if any |
| // of the bits shifted in could be tested after the mask. |
| uint32_t TyBits = Ty->getPrimitiveSizeInBits(); |
| int ShAmtVal = TyBits - ShAmt->getLimitedValue(TyBits); |
| |
| uint32_t BitWidth = AndTy->getPrimitiveSizeInBits(); |
| if ((APInt::getHighBitsSet(BitWidth, BitWidth-ShAmtVal) & |
| AndCST->getValue()) == 0) |
| CanFold = true; |
| } |
| |
| if (CanFold) { |
| Constant *NewCst; |
| if (Shift->getOpcode() == 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(Shift->getOpcode(), |
| 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, |
| ConstantInt::getFalse(ICI.getContext())); |
| if (ICI.getPredicate() == ICmpInst::ICMP_NE) |
| return ReplaceInstUsesWith(ICI, |
| ConstantInt::getTrue(ICI.getContext())); |
| } else { |
| ICI.setOperand(1, NewCst); |
| Constant *NewAndCST; |
| if (Shift->getOpcode() == 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), "tmp"); |
| } else { |
| // Insert a logical shift. |
| NS = Builder->CreateLShr(AndCST, Shift->getOperand(1), "tmp"); |
| } |
| |
| // Compute X & (C << Y). |
| Value *NewAnd = |
| Builder->CreateAnd(Shift->getOperand(0), NS, LHSI->getName()); |
| |
| ICI.setOperand(0, NewAnd); |
| return &ICI; |
| } |
| } |
| |
| // 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; |
| } |
| } |
| 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::Shl: { // (icmp pred (shl X, ShAmt), CI) |
| ConstantInt *ShAmt = dyn_cast<ConstantInt>(LHSI->getOperand(1)); |
| if (!ShAmt) break; |
| |
| uint32_t TypeBits = RHSV.getBitWidth(); |
| |
| // 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 = |
| ConstantInt::get(Type::getInt1Ty(ICI.getContext()), 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 (LHSI->hasOneUse()) { |
| // Otherwise strength reduce the shift into an and. |
| uint32_t ShAmtVal = (uint32_t)ShAmt->getLimitedValue(TypeBits); |
| Constant *Mask = |
| ConstantInt::get(ICI.getContext(), 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)); |
| } |
| } |
| |
| // 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())); |
| } |
| 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::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), |
| ConstantInt::get(ICI.getContext(),CR.getUpper())); |
| } else if (CR.getUpper().isSignBit()) { |
| return new ICmpInst(ICmpInst::ICMP_SGE, LHSI->getOperand(0), |
| ConstantInt::get(ICI.getContext(),CR.getLower())); |
| } |
| } else { |
| if (CR.getLower().isMinValue()) { |
| return new ICmpInst(ICmpInst::ICMP_ULT, LHSI->getOperand(0), |
| ConstantInt::get(ICI.getContext(),CR.getUpper())); |
| } else if (CR.getUpper().isMinValue()) { |
| return new ICmpInst(ICmpInst::ICMP_UGE, LHSI->getOperand(0), |
| ConstantInt::get(ICI.getContext(),CR.getLower())); |
| } |
| } |
| } |
| 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, |
| ConstantInt::get(Type::getInt1Ty(ICI.getContext()), |
| 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, |
| ConstantInt::get(Type::getInt1Ty(ICI.getContext()), |
| 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); |
| } |
| } |
| 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, ConstantInt::get(II->getContext(), 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 0; |
| } |
| |
| /// 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); |
| const Type *SrcTy = LHSCIOp->getType(); |
| const 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 (TD && LHSCI->getOpcode() == Instruction::PtrToInt && |
| TD->getPointerSizeInBits() == |
| cast<IntegerType>(DestTy)->getBitWidth()) { |
| Value *RHSOp = 0; |
| if (Constant *RHSC = dyn_cast<Constant>(ICI.getOperand(1))) { |
| RHSOp = ConstantExpr::getIntToPtr(RHSC, SrcTy); |
| } else if (PtrToIntInst *RHSC = dyn_cast<PtrToIntInst>(ICI.getOperand(1))) { |
| 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()); |
| } |
| |
| 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 0; |
| |
| 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 0; |
| |
| // 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 0; |
| |
| // 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 0; |
| |
| // 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 0; |
| |
| // 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 0; |
| |
| // If CI2 is 2^7, 2^15, 2^31, then it might be an sadd.with.overflow. |
| if (!CI2->getValue().isPowerOf2()) return 0; |
| unsigned NewWidth = CI2->getValue().countTrailingZeros(); |
| if (NewWidth != 7 && NewWidth != 15 && NewWidth != 31) return 0; |
| |
| // 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 0; |
| |
| // 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 (Value::use_iterator UI = OrigAdd->use_begin(), E = OrigAdd->use_end(); |
| UI != E; ++UI) { |
| if (*UI == 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>(*UI); |
| if (TI == 0 || |
| TI->getType()->getPrimitiveSizeInBits() > NewWidth) return 0; |
| } |
| |
| // 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(); |
| |
| const Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth); |
| Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow, |
| &NewType, 1); |
| |
| 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->CreateCall2(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"); |
| } |
| |
| static Instruction *ProcessUAddIdiom(Instruction &I, Value *OrigAddV, |
| InstCombiner &IC) { |
| // Don't bother doing this transformation for pointers, don't do it for |
| // vectors. |
| if (!isa<IntegerType>(OrigAddV->getType())) return 0; |
| |
| // If the add is a constant expr, then we don't bother transforming it. |
| Instruction *OrigAdd = dyn_cast<Instruction>(OrigAddV); |
| if (OrigAdd == 0) return 0; |
| |
| Value *LHS = OrigAdd->getOperand(0), *RHS = OrigAdd->getOperand(1); |
| |
| // Put the new code above the original add, in case there are any uses of the |
| // add between the add and the compare. |
| InstCombiner::BuilderTy *Builder = IC.Builder; |
| Builder->SetInsertPoint(OrigAdd); |
| |
| Module *M = I.getParent()->getParent()->getParent(); |
| const Type *Ty = LHS->getType(); |
| Value *F = Intrinsic::getDeclaration(M, Intrinsic::uadd_with_overflow, &Ty,1); |
| CallInst *Call = Builder->CreateCall2(F, LHS, RHS, "uadd"); |
| Value *Add = Builder->CreateExtractValue(Call, 0); |
| |
| IC.ReplaceInstUsesWith(*OrigAdd, Add); |
| |
| // The original icmp gets replaced with the overflow value. |
| return ExtractValueInst::Create(Call, 1, "uadd.overflow"); |
| } |
| |
| // 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); |
| } |
| |
| } |
| |
| Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { |
| bool Changed = false; |
| Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); |
| |
| /// 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(Op0) < getComplexity(Op1)) { |
| I.swapOperands(); |
| std::swap(Op0, Op1); |
| Changed = true; |
| } |
| |
| if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, TD)) |
| return ReplaceInstUsesWith(I, V); |
| |
| const 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 if (TD) // Pointers require TD info to get their size. |
| BitWidth = TD->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 = 0, *B = 0; |
| |
| // 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; |
| } |
| |
| // (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)))) { |
| // (icmp cond A B) if cond is equality |
| return new ICmpInst(I.getPredicate(), 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, |
| ConstantInt::get(CI->getContext(), CI->getValue()+1)); |
| case ICmpInst::ICMP_SLE: |
| assert(!CI->isMaxValue(true)); // A <=s MAX -> TRUE |
| return new ICmpInst(ICmpInst::ICMP_SLT, Op0, |
| ConstantInt::get(CI->getContext(), CI->getValue()+1)); |
| case ICmpInst::ICMP_UGE: |
| assert(!CI->isMinValue(false)); // A >=u MIN -> TRUE |
| return new ICmpInst(ICmpInst::ICMP_UGT, Op0, |
| ConstantInt::get(CI->getContext(), CI->getValue()-1)); |
| case ICmpInst::ICMP_SGE: |
| assert(!CI->isMinValue(true)); // A >=s MIN -> TRUE |
| return new ICmpInst(ICmpInst::ICMP_SGT, Op0, |
| ConstantInt::get(CI->getContext(), CI->getValue()-1)); |
| } |
| |
| // 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 && Op0KnownZeroInverted.isPowerOf2()) { |
| // If the LHS is an AND with the same constant, look through it. |
| Value *LHS = 0; |
| ConstantInt *LHSC = 0; |
| 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". |
| Value *X = 0; |
| if (match(LHS, m_Shl(m_One(), m_Value(X)))) { |
| unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); |
| return new ICmpInst(ICmpInst::ICMP_NE, 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 && Op0KnownZeroInverted.isPowerOf2()) { |
| // If the LHS is an AND with the same constant, look through it. |
| Value *LHS = 0; |
| ConstantInt *LHSC = 0; |
| 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". |
| Value *X = 0; |
| if (match(LHS, m_Shl(m_One(), m_Value(X)))) { |
| unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros(); |
| return new ICmpInst(ICmpInst::ICMP_EQ, 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, |
| ConstantInt::get(CI->getContext(), 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, |
| ConstantInt::get(CI->getContext(), 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, |
| ConstantInt::get(CI->getContext(), 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, |
| ConstantInt::get(CI->getContext(), 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.use_begin())) |
| if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || |
| (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) |
| return 0; |
| |
| // 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 = 0, *Op2 = 0; |
| if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) |
| Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); |
| if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) |
| Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); |
| |
| // 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). |
| if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) { |
| 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() && TD && |
| TD->getIntPtrType(RHSC->getContext()) == |
| 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 = 0, *B = 0, *C = 0, *D = 0; |
| 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+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 = (A == C || A == D) ? B : A; |
| Value *Z = (C == A || C == B) ? D : C; |
| return new ICmpInst(Pred, Y, Z); |
| } |
| |
| // 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 = 0; B = 0; C = 0; D = 0; |
| 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); |
| |
| BinaryOperator *SRem = NULL; |
| // 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->getValue().isMaxSignedValue()) { |
| 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; |
| // ~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); |
| } |
| |
| // (a+b) <u a --> llvm.uadd.with.overflow. |
| // (a+b) <u b --> llvm.uadd.with.overflow. |
| if (I.getPredicate() == ICmpInst::ICMP_ULT && |
| match(Op0, m_Add(m_Value(A), m_Value(B))) && |
| (Op1 == A || Op1 == B)) |
| if (Instruction *R = ProcessUAddIdiom(I, Op0, *this)) |
| return R; |
| |
| // a >u (a+b) --> llvm.uadd.with.overflow. |
| // b >u (a+b) --> llvm.uadd.with.overflow. |
| if (I.getPredicate() == ICmpInst::ICMP_UGT && |
| match(Op1, m_Add(m_Value(A), m_Value(B))) && |
| (Op0 == A || Op0 == B)) |
| if (Instruction *R = ProcessUAddIdiom(I, Op1, *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 = ConstantInt::get(I.getContext(), |
| C1->getValue() ^ C2->getValue()); |
| Value *Xor = Builder->CreateXor(C, NC, "tmp"); |
| 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 = 0, *Y = 0, *Z = 0; |
| |
| 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, "tmp"); |
| Op1 = Builder->CreateAnd(Op1, Z, "tmp"); |
| I.setOperand(0, Op1); |
| I.setOperand(1, Constant::getNullValue(Op1->getType())); |
| return &I; |
| } |
| } |
| |
| // Transform "icmp eq (trunc (lshr(X, cst1)), cst" to |
| // "icmp (and X, mask), cst" |
| uint64_t ShAmt = 0; |
| ConstantInt *Cst1; |
| 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)); |
| } |
| } |
| } |
| |
| { |
| 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(), Op0); |
| |
| // icmp X, X+Cst |
| if (match(Op1, m_Add(m_Value(X), m_ConstantInt(Cst))) && Op0 == X) |
| return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate(), Op1); |
| } |
| return Changed ? &I : 0; |
| } |
| |
| |
| |
| |
| |
| |
| /// 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 0; |
| 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 0; // Unknown. |
| |
| // 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 = LHSI->getOperand(0)->getType()->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 the conversion would lose info, don't hack on this. |
| if ((int)InputSize > MantissaWidth) |
| return 0; |
| |
| // 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, ConstantInt::getTrue(I.getContext())); |
| case FCmpInst::FCMP_UNO: |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| } |
| |
| const IntegerType *IntTy = cast<IntegerType>(LHSI->getOperand(0)->getType()); |
| |
| // 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(), APFloat::fcZero, false); |
| 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, ConstantInt::getTrue(I.getContext())); |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| } |
| } else { |
| // If the RHS value is > UnsignedMax, fold the comparison. This handles |
| // +INF and large values. |
| APFloat UMax(RHS.getSemantics(), APFloat::fcZero, false); |
| 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, ConstantInt::getTrue(I.getContext())); |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| } |
| } |
| |
| if (!LHSUnsigned) { |
| // See if the RHS value is < SignedMin. |
| APFloat SMin(RHS.getSemantics(), APFloat::fcZero, false); |
| 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, ConstantInt::getTrue(I.getContext())); |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| } |
| } |
| |
| // 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, ConstantInt::getTrue(I.getContext())); |
| case ICmpInst::ICMP_EQ: // (float)int == 4.4 --> false |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| case ICmpInst::ICMP_ULE: |
| // (float)int <= 4.4 --> int <= 4 |
| // (float)int <= -4.4 --> false |
| if (RHS.isNegative()) |
| return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getContext())); |
| 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, ConstantInt::getFalse(I.getContext())); |
| 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, ConstantInt::getTrue(I.getContext())); |
| 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, ConstantInt::getTrue(I.getContext())); |
| 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, TD)) |
| 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; |
| } |
| } |
| |
| // 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; |
| |
| // We can't convert a PPC double double. |
| if (RHSF->getType()->isPPC_FP128Ty()) |
| break; |
| |
| const fltSemantics *Sem; |
| // FIXME: This shouldn't be here. |
| 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 |
| break; |
| |
| bool Lossy; |
| APFloat F = RHSF->getValueAPF(); |
| F.convert(*Sem, APFloat::rmNearestTiesToEven, &Lossy); |
| |
| // Avoid lossy conversions and denormals. |
| if (!Lossy && |
| F.compare(APFloat::getSmallestNormalized(*Sem)) != |
| APFloat::cmpLessThan) |
| 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::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 = 0, *Op2 = 0; |
| if (LHSI->hasOneUse()) { |
| if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { |
| // Fold the known value into the constant operand. |
| Op1 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); |
| // Insert a new FCmp of the other select operand. |
| Op2 = Builder->CreateFCmp(I.getPredicate(), |
| LHSI->getOperand(2), RHSC, I.getName()); |
| } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { |
| // Fold the known value into the constant operand. |
| Op2 = ConstantExpr::getCompare(I.getPredicate(), C, RHSC); |
| // Insert a new FCmp of the other select operand. |
| Op1 = Builder->CreateFCmp(I.getPredicate(), LHSI->getOperand(1), |
| RHSC, I.getName()); |
| } |
| } |
| |
| if (Op1) |
| return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); |
| 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; |
| } |
| } |
| |
| // 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 : 0; |
| } |