diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/InstCombine/CMakeLists.txt | 1 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombine.h | 18 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 2443 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstructionCombining.cpp | 2450 |
4 files changed, 2477 insertions, 2435 deletions
diff --git a/lib/Transforms/InstCombine/CMakeLists.txt b/lib/Transforms/InstCombine/CMakeLists.txt index 665903064a..96b016650e 100644 --- a/lib/Transforms/InstCombine/CMakeLists.txt +++ b/lib/Transforms/InstCombine/CMakeLists.txt @@ -1,5 +1,6 @@ add_llvm_library(LLVMInstCombine InstructionCombining.cpp + InstCombineCompares.cpp InstCombineSimplifyDemanded.cpp ) diff --git a/lib/Transforms/InstCombine/InstCombine.h b/lib/Transforms/InstCombine/InstCombine.h index d4d26f8e34..a1e9f2ffe3 100644 --- a/lib/Transforms/InstCombine/InstCombine.h +++ b/lib/Transforms/InstCombine/InstCombine.h @@ -32,6 +32,20 @@ enum SelectPatternFlavor { SPF_SMAX, SPF_UMAX //SPF_ABS - TODO. }; + +/// getComplexity: Assign a complexity or rank value to LLVM Values... +/// 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst +static inline unsigned getComplexity(Value *V) { + if (isa<Instruction>(V)) { + if (BinaryOperator::isNeg(V) || + BinaryOperator::isFNeg(V) || + BinaryOperator::isNot(V)) + return 3; + return 4; + } + if (isa<Argument>(V)) return 3; + return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2; +} /// InstCombineIRInserter - This is an IRBuilder insertion helper that works @@ -179,6 +193,8 @@ public: Instruction *visitInstruction(Instruction &I) { return 0; } private: + Value *dyn_castNegVal(Value *V) const; + Instruction *visitCallSite(CallSite CS); bool transformConstExprCastCall(CallSite CS); Instruction *transformCallThroughTrampoline(CallSite CS); @@ -186,7 +202,7 @@ private: bool DoXform = true); bool WillNotOverflowSignedAdd(Value *LHS, Value *RHS); DbgDeclareInst *hasOneUsePlusDeclare(Value *V); - + Value *EmitGEPOffset(User *GEP); public: // InsertNewInstBefore - insert an instruction New before instruction Old diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp new file mode 100644 index 0000000000..005f1a0bc4 --- /dev/null +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -0,0 +1,2443 @@ +//===- 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; + +/// 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(ConstantInt *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.set(Min.getBitWidth()-1); + Max.clear(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) { + 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 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, Instruction &I, + 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) + VariableIdx = new TruncInst(VariableIdx, + TD.getIntPtrType(VariableIdx->getContext()), + VariableIdx->getName(), &I); + 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 = CastInst::CreateIntegerCast(VariableIdx, IntPtrTy, + true /*SExt*/, + VariableIdx->getName(), &I); + Constant *OffsetVal = ConstantInt::get(IntPtrTy, NewOffs); + return BinaryOperator::CreateAdd(VariableIdx, OffsetVal, "offset", &I); +} + +/// 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, I, *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); + + 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) { + 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 && + (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())); + + // If this is an instruction (as opposed to constantexpr) get NUW/NSW info. + bool isNUW = false, isNSW = false; + if (BinaryOperator *Add = dyn_cast<BinaryOperator>(TheAdd)) { + isNUW = Add->hasNoUnsignedWrap(); + isNSW = Add->hasNoSignedWrap(); + } + + // From this point on, we know that (X+C <= X) --> (X+C < X) because C != 0, + // so the values can never be equal. Similiarly 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) { + // If this is an NUW add, then this is always false. + if (isNUW) + return ReplaceInstUsesWith(ICI, ConstantInt::getFalse(X->getContext())); + + Value *R = ConstantExpr::getSub(ConstantInt::get(CI->getType(), -1ULL), 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) { + // If this is an NUW add, then this is always true. + if (isNUW) + return ReplaceInstUsesWith(ICI, ConstantInt::getTrue(X->getContext())); + 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) { + // If this is an NSW add, then we have two cases: if the constant is + // positive, then this is always false, if negative, this is always true. + if (isNSW) { + bool isTrue = CI->getValue().isNegative(); + return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); + } + + 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 + + // If this is an NSW add, then we have two cases: if the constant is + // positive, then this is always true, if negative, this is always false. + if (isNSW) { + bool isTrue = !CI->getValue().isNegative(); + return ReplaceInstUsesWith(ICI, ConstantInt::get(ICI.getType(), isTrue)); + } + + 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()) + return 0; // Not worth bothering, and eliminates some funny cases + // with INT_MIN. + + // 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(); + + // 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). + / |