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llvm-6502/lib/VMCore/ConstantFold.cpp
Nick Lewycky 149cbc2a24 Peer through zext and sext to eliminate them when it is safe to do so. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82389 91177308-0d34-0410-b5e6-96231b3b80d8
2009-09-20 07:31:25 +00:00

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//===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements folding of constants for LLVM. This implements the
// (internal) ConstantFold.h interface, which is used by the
// ConstantExpr::get* methods to automatically fold constants when possible.
//
// The current constant folding implementation is implemented in two pieces: the
// pieces that don't need TargetData, and the pieces that do. This is to avoid
// a dependence in VMCore on Target.
//
//===----------------------------------------------------------------------===//
#include "ConstantFold.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
#include "llvm/LLVMContext.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
#include <limits>
using namespace llvm;
//===----------------------------------------------------------------------===//
// ConstantFold*Instruction Implementations
//===----------------------------------------------------------------------===//
/// BitCastConstantVector - Convert the specified ConstantVector node to the
/// specified vector type. At this point, we know that the elements of the
/// input vector constant are all simple integer or FP values.
static Constant *BitCastConstantVector(LLVMContext &Context, ConstantVector *CV,
const VectorType *DstTy) {
// If this cast changes element count then we can't handle it here:
// doing so requires endianness information. This should be handled by
// Analysis/ConstantFolding.cpp
unsigned NumElts = DstTy->getNumElements();
if (NumElts != CV->getNumOperands())
return 0;
// Check to verify that all elements of the input are simple.
for (unsigned i = 0; i != NumElts; ++i) {
if (!isa<ConstantInt>(CV->getOperand(i)) &&
!isa<ConstantFP>(CV->getOperand(i)))
return 0;
}
// Bitcast each element now.
std::vector<Constant*> Result;
const Type *DstEltTy = DstTy->getElementType();
for (unsigned i = 0; i != NumElts; ++i)
Result.push_back(ConstantExpr::getBitCast(CV->getOperand(i),
DstEltTy));
return ConstantVector::get(Result);
}
/// This function determines which opcode to use to fold two constant cast
/// expressions together. It uses CastInst::isEliminableCastPair to determine
/// the opcode. Consequently its just a wrapper around that function.
/// @brief Determine if it is valid to fold a cast of a cast
static unsigned
foldConstantCastPair(
unsigned opc, ///< opcode of the second cast constant expression
ConstantExpr *Op, ///< the first cast constant expression
const Type *DstTy ///< desintation type of the first cast
) {
assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
assert(CastInst::isCast(opc) && "Invalid cast opcode");
// The the types and opcodes for the two Cast constant expressions
const Type *SrcTy = Op->getOperand(0)->getType();
const Type *MidTy = Op->getType();
Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
Instruction::CastOps secondOp = Instruction::CastOps(opc);
// Let CastInst::isEliminableCastPair do the heavy lifting.
return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
Type::getInt64Ty(DstTy->getContext()));
}
static Constant *FoldBitCast(LLVMContext &Context,
Constant *V, const Type *DestTy) {
const Type *SrcTy = V->getType();
if (SrcTy == DestTy)
return V; // no-op cast
// Check to see if we are casting a pointer to an aggregate to a pointer to
// the first element. If so, return the appropriate GEP instruction.
if (const PointerType *PTy = dyn_cast<PointerType>(V->getType()))
if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy))
if (PTy->getAddressSpace() == DPTy->getAddressSpace()) {
SmallVector<Value*, 8> IdxList;
Value *Zero = Constant::getNullValue(Type::getInt32Ty(Context));
IdxList.push_back(Zero);
const Type *ElTy = PTy->getElementType();
while (ElTy != DPTy->getElementType()) {
if (const StructType *STy = dyn_cast<StructType>(ElTy)) {
if (STy->getNumElements() == 0) break;
ElTy = STy->getElementType(0);
IdxList.push_back(Zero);
} else if (const SequentialType *STy =
dyn_cast<SequentialType>(ElTy)) {
if (isa<PointerType>(ElTy)) break; // Can't index into pointers!
ElTy = STy->getElementType();
IdxList.push_back(Zero);
} else {
break;
}
}
if (ElTy == DPTy->getElementType())
// This GEP is inbounds because all indices are zero.
return ConstantExpr::getInBoundsGetElementPtr(V, &IdxList[0],
IdxList.size());
}
// Handle casts from one vector constant to another. We know that the src
// and dest type have the same size (otherwise its an illegal cast).
if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) {
assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() &&
"Not cast between same sized vectors!");
SrcTy = NULL;
// First, check for null. Undef is already handled.
if (isa<ConstantAggregateZero>(V))
return Constant::getNullValue(DestTy);
if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
return BitCastConstantVector(Context, CV, DestPTy);
}
// Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
// This allows for other simplifications (although some of them
// can only be handled by Analysis/ConstantFolding.cpp).
if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
return ConstantExpr::getBitCast(
ConstantVector::get(&V, 1), DestPTy);
}
// Finally, implement bitcast folding now. The code below doesn't handle
// bitcast right.
if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
return ConstantPointerNull::get(cast<PointerType>(DestTy));
// Handle integral constant input.
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
if (DestTy->isInteger())
// Integral -> Integral. This is a no-op because the bit widths must
// be the same. Consequently, we just fold to V.
return V;
if (DestTy->isFloatingPoint())
return ConstantFP::get(Context, APFloat(CI->getValue(),
DestTy != Type::getPPC_FP128Ty(Context)));
// Otherwise, can't fold this (vector?)
return 0;
}
// Handle ConstantFP input.
if (ConstantFP *FP = dyn_cast<ConstantFP>(V))
// FP -> Integral.
return ConstantInt::get(Context, FP->getValueAPF().bitcastToAPInt());
return 0;
}
Constant *llvm::ConstantFoldCastInstruction(LLVMContext &Context,
unsigned opc, Constant *V,
const Type *DestTy) {
if (isa<UndefValue>(V)) {
// zext(undef) = 0, because the top bits will be zero.
// sext(undef) = 0, because the top bits will all be the same.
// [us]itofp(undef) = 0, because the result value is bounded.
if (opc == Instruction::ZExt || opc == Instruction::SExt ||
opc == Instruction::UIToFP || opc == Instruction::SIToFP)
return Constant::getNullValue(DestTy);
return UndefValue::get(DestTy);
}
// No compile-time operations on this type yet.
if (V->getType() == Type::getPPC_FP128Ty(Context) || DestTy == Type::getPPC_FP128Ty(Context))
return 0;
// If the cast operand is a constant expression, there's a few things we can
// do to try to simplify it.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->isCast()) {
// Try hard to fold cast of cast because they are often eliminable.
if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy);
} else if (CE->getOpcode() == Instruction::GetElementPtr) {
// If all of the indexes in the GEP are null values, there is no pointer
// adjustment going on. We might as well cast the source pointer.
bool isAllNull = true;
for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
if (!CE->getOperand(i)->isNullValue()) {
isAllNull = false;
break;
}
if (isAllNull)
// This is casting one pointer type to another, always BitCast
return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy);
}
}
// If the cast operand is a constant vector, perform the cast by
// operating on each element. In the cast of bitcasts, the element
// count may be mismatched; don't attempt to handle that here.
if (ConstantVector *CV = dyn_cast<ConstantVector>(V))
if (isa<VectorType>(DestTy) &&
cast<VectorType>(DestTy)->getNumElements() ==
CV->getType()->getNumElements()) {
std::vector<Constant*> res;
const VectorType *DestVecTy = cast<VectorType>(DestTy);
const Type *DstEltTy = DestVecTy->getElementType();
for (unsigned i = 0, e = CV->getType()->getNumElements(); i != e; ++i)
res.push_back(ConstantExpr::getCast(opc,
CV->getOperand(i), DstEltTy));
return ConstantVector::get(DestVecTy, res);
}
// We actually have to do a cast now. Perform the cast according to the
// opcode specified.
switch (opc) {
case Instruction::FPTrunc:
case Instruction::FPExt:
if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
bool ignored;
APFloat Val = FPC->getValueAPF();
Val.convert(DestTy == Type::getFloatTy(Context) ? APFloat::IEEEsingle :
DestTy == Type::getDoubleTy(Context) ? APFloat::IEEEdouble :
DestTy == Type::getX86_FP80Ty(Context) ? APFloat::x87DoubleExtended :
DestTy == Type::getFP128Ty(Context) ? APFloat::IEEEquad :
APFloat::Bogus,
APFloat::rmNearestTiesToEven, &ignored);
return ConstantFP::get(Context, Val);
}
return 0; // Can't fold.
case Instruction::FPToUI:
case Instruction::FPToSI:
if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
const APFloat &V = FPC->getValueAPF();
bool ignored;
uint64_t x[2];
uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
(void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI,
APFloat::rmTowardZero, &ignored);
APInt Val(DestBitWidth, 2, x);
return ConstantInt::get(Context, Val);
}
return 0; // Can't fold.
case Instruction::IntToPtr: //always treated as unsigned
if (V->isNullValue()) // Is it an integral null value?
return ConstantPointerNull::get(cast<PointerType>(DestTy));
return 0; // Other pointer types cannot be casted
case Instruction::PtrToInt: // always treated as unsigned
if (V->isNullValue()) // is it a null pointer value?
return ConstantInt::get(DestTy, 0);
return 0; // Other pointer types cannot be casted
case Instruction::UIToFP:
case Instruction::SIToFP:
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
APInt api = CI->getValue();
const uint64_t zero[] = {0, 0};
APFloat apf = APFloat(APInt(DestTy->getPrimitiveSizeInBits(),
2, zero));
(void)apf.convertFromAPInt(api,
opc==Instruction::SIToFP,
APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, apf);
}
return 0;
case Instruction::ZExt:
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.zext(BitWidth);
return ConstantInt::get(Context, Result);
}
return 0;
case Instruction::SExt:
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.sext(BitWidth);
return ConstantInt::get(Context, Result);
}
return 0;
case Instruction::Trunc:
if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.trunc(BitWidth);
return ConstantInt::get(Context, Result);
}
return 0;
case Instruction::BitCast:
return FoldBitCast(Context, V, DestTy);
default:
assert(!"Invalid CE CastInst opcode");
break;
}
llvm_unreachable("Failed to cast constant expression");
return 0;
}
Constant *llvm::ConstantFoldSelectInstruction(LLVMContext&,
Constant *Cond,
Constant *V1, Constant *V2) {
if (ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
return CB->getZExtValue() ? V1 : V2;
if (isa<UndefValue>(V1)) return V2;
if (isa<UndefValue>(V2)) return V1;
if (isa<UndefValue>(Cond)) return V1;
if (V1 == V2) return V1;
return 0;
}
Constant *llvm::ConstantFoldExtractElementInstruction(LLVMContext &Context,
Constant *Val,
Constant *Idx) {
if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
return UndefValue::get(cast<VectorType>(Val->getType())->getElementType());
if (Val->isNullValue()) // ee(zero, x) -> zero
return Constant::getNullValue(
cast<VectorType>(Val->getType())->getElementType());
if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
return CVal->getOperand(CIdx->getZExtValue());
} else if (isa<UndefValue>(Idx)) {
// ee({w,x,y,z}, undef) -> w (an arbitrary value).
return CVal->getOperand(0);
}
}
return 0;
}
Constant *llvm::ConstantFoldInsertElementInstruction(LLVMContext &Context,
Constant *Val,
Constant *Elt,
Constant *Idx) {
ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
if (!CIdx) return 0;
APInt idxVal = CIdx->getValue();
if (isa<UndefValue>(Val)) {
// Insertion of scalar constant into vector undef
// Optimize away insertion of undef
if (isa<UndefValue>(Elt))
return Val;
// Otherwise break the aggregate undef into multiple undefs and do
// the insertion
unsigned numOps =
cast<VectorType>(Val->getType())->getNumElements();
std::vector<Constant*> Ops;
Ops.reserve(numOps);
for (unsigned i = 0; i < numOps; ++i) {
Constant *Op =
(idxVal == i) ? Elt : UndefValue::get(Elt->getType());
Ops.push_back(Op);
}
return ConstantVector::get(Ops);
}
if (isa<ConstantAggregateZero>(Val)) {
// Insertion of scalar constant into vector aggregate zero
// Optimize away insertion of zero
if (Elt->isNullValue())
return Val;
// Otherwise break the aggregate zero into multiple zeros and do
// the insertion
unsigned numOps =
cast<VectorType>(Val->getType())->getNumElements();
std::vector<Constant*> Ops;
Ops.reserve(numOps);
for (unsigned i = 0; i < numOps; ++i) {
Constant *Op =
(idxVal == i) ? Elt : Constant::getNullValue(Elt->getType());
Ops.push_back(Op);
}
return ConstantVector::get(Ops);
}
if (ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
// Insertion of scalar constant into vector constant
std::vector<Constant*> Ops;
Ops.reserve(CVal->getNumOperands());
for (unsigned i = 0; i < CVal->getNumOperands(); ++i) {
Constant *Op =
(idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
Ops.push_back(Op);
}
return ConstantVector::get(Ops);
}
return 0;
}
/// GetVectorElement - If C is a ConstantVector, ConstantAggregateZero or Undef
/// return the specified element value. Otherwise return null.
static Constant *GetVectorElement(LLVMContext &Context, Constant *C,
unsigned EltNo) {
if (ConstantVector *CV = dyn_cast<ConstantVector>(C))
return CV->getOperand(EltNo);
const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
if (isa<ConstantAggregateZero>(C))
return Constant::getNullValue(EltTy);
if (isa<UndefValue>(C))
return UndefValue::get(EltTy);
return 0;
}
Constant *llvm::ConstantFoldShuffleVectorInstruction(LLVMContext &Context,
Constant *V1,
Constant *V2,
Constant *Mask) {
// Undefined shuffle mask -> undefined value.
if (isa<UndefValue>(Mask)) return UndefValue::get(V1->getType());
unsigned MaskNumElts = cast<VectorType>(Mask->getType())->getNumElements();
unsigned SrcNumElts = cast<VectorType>(V1->getType())->getNumElements();
const Type *EltTy = cast<VectorType>(V1->getType())->getElementType();
// Loop over the shuffle mask, evaluating each element.
SmallVector<Constant*, 32> Result;
for (unsigned i = 0; i != MaskNumElts; ++i) {
Constant *InElt = GetVectorElement(Context, Mask, i);
if (InElt == 0) return 0;
if (isa<UndefValue>(InElt))
InElt = UndefValue::get(EltTy);
else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
unsigned Elt = CI->getZExtValue();
if (Elt >= SrcNumElts*2)
InElt = UndefValue::get(EltTy);
else if (Elt >= SrcNumElts)
InElt = GetVectorElement(Context, V2, Elt - SrcNumElts);
else
InElt = GetVectorElement(Context, V1, Elt);
if (InElt == 0) return 0;
} else {
// Unknown value.
return 0;
}
Result.push_back(InElt);
}
return ConstantVector::get(&Result[0], Result.size());
}
Constant *llvm::ConstantFoldExtractValueInstruction(LLVMContext &Context,
Constant *Agg,
const unsigned *Idxs,
unsigned NumIdx) {
// Base case: no indices, so return the entire value.
if (NumIdx == 0)
return Agg;
if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef
return UndefValue::get(ExtractValueInst::getIndexedType(Agg->getType(),
Idxs,
Idxs + NumIdx));
if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0
return
Constant::getNullValue(ExtractValueInst::getIndexedType(Agg->getType(),
Idxs,
Idxs + NumIdx));
// Otherwise recurse.
return ConstantFoldExtractValueInstruction(Context, Agg->getOperand(*Idxs),
Idxs+1, NumIdx-1);
}
Constant *llvm::ConstantFoldInsertValueInstruction(LLVMContext &Context,
Constant *Agg,
Constant *Val,
const unsigned *Idxs,
unsigned NumIdx) {
// Base case: no indices, so replace the entire value.
if (NumIdx == 0)
return Val;
if (isa<UndefValue>(Agg)) {
// Insertion of constant into aggregate undef
// Optimize away insertion of undef.
if (isa<UndefValue>(Val))
return Agg;
// Otherwise break the aggregate undef into multiple undefs and do
// the insertion.
const CompositeType *AggTy = cast<CompositeType>(Agg->getType());
unsigned numOps;
if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy))
numOps = AR->getNumElements();
else
numOps = cast<StructType>(AggTy)->getNumElements();
std::vector<Constant*> Ops(numOps);
for (unsigned i = 0; i < numOps; ++i) {
const Type *MemberTy = AggTy->getTypeAtIndex(i);
Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context, UndefValue::get(MemberTy),
Val, Idxs+1, NumIdx-1) :
UndefValue::get(MemberTy);
Ops[i] = Op;
}
if (const StructType* ST = dyn_cast<StructType>(AggTy))
return ConstantStruct::get(Context, Ops, ST->isPacked());
return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
}
if (isa<ConstantAggregateZero>(Agg)) {
// Insertion of constant into aggregate zero
// Optimize away insertion of zero.
if (Val->isNullValue())
return Agg;
// Otherwise break the aggregate zero into multiple zeros and do
// the insertion.
const CompositeType *AggTy = cast<CompositeType>(Agg->getType());
unsigned numOps;
if (const ArrayType *AR = dyn_cast<ArrayType>(AggTy))
numOps = AR->getNumElements();
else
numOps = cast<StructType>(AggTy)->getNumElements();
std::vector<Constant*> Ops(numOps);
for (unsigned i = 0; i < numOps; ++i) {
const Type *MemberTy = AggTy->getTypeAtIndex(i);
Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context,
Constant::getNullValue(MemberTy),
Val, Idxs+1, NumIdx-1) :
Constant::getNullValue(MemberTy);
Ops[i] = Op;
}
if (const StructType* ST = dyn_cast<StructType>(AggTy))
return ConstantStruct::get(Context, Ops, ST->isPacked());
return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
}
if (isa<ConstantStruct>(Agg) || isa<ConstantArray>(Agg)) {
// Insertion of constant into aggregate constant.
std::vector<Constant*> Ops(Agg->getNumOperands());
for (unsigned i = 0; i < Agg->getNumOperands(); ++i) {
Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context, Agg->getOperand(i),
Val, Idxs+1, NumIdx-1) :
Agg->getOperand(i);
Ops[i] = Op;
}
if (const StructType* ST = dyn_cast<StructType>(Agg->getType()))
return ConstantStruct::get(Context, Ops, ST->isPacked());
return ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops);
}
return 0;
}
Constant *llvm::ConstantFoldBinaryInstruction(LLVMContext &Context,
unsigned Opcode,
Constant *C1, Constant *C2) {
// No compile-time operations on this type yet.
if (C1->getType() == Type::getPPC_FP128Ty(Context))
return 0;
// Handle UndefValue up front.
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
switch (Opcode) {
case Instruction::Xor:
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
// Handle undef ^ undef -> 0 special case. This is a common
// idiom (misuse).
return Constant::getNullValue(C1->getType());
// Fallthrough
case Instruction::Add:
case Instruction::Sub:
return UndefValue::get(C1->getType());
case Instruction::Mul:
case Instruction::And:
return Constant::getNullValue(C1->getType());
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
if (!isa<UndefValue>(C2)) // undef / X -> 0
return Constant::getNullValue(C1->getType());
return C2; // X / undef -> undef
case Instruction::Or: // X | undef -> -1
if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
return Constant::getAllOnesValue(PTy);
return Constant::getAllOnesValue(C1->getType());
case Instruction::LShr:
if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
return C1; // undef lshr undef -> undef
return Constant::getNullValue(C1->getType()); // X lshr undef -> 0
// undef lshr X -> 0
case Instruction::AShr:
if (!isa<UndefValue>(C2))
return C1; // undef ashr X --> undef
else if (isa<UndefValue>(C1))
return C1; // undef ashr undef -> undef
else
return C1; // X ashr undef --> X
case Instruction::Shl:
// undef << X -> 0 or X << undef -> 0
return Constant::getNullValue(C1->getType());
}
}
// Handle simplifications when the RHS is a constant int.
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
switch (Opcode) {
case Instruction::Add:
if (CI2->equalsInt(0)) return C1; // X + 0 == X
break;
case Instruction::Sub:
if (CI2->equalsInt(0)) return C1; // X - 0 == X
break;
case Instruction::Mul:
if (CI2->equalsInt(0)) return C2; // X * 0 == 0
if (CI2->equalsInt(1))
return C1; // X * 1 == X
break;
case Instruction::UDiv:
case Instruction::SDiv:
if (CI2->equalsInt(1))
return C1; // X / 1 == X
if (CI2->equalsInt(0))
return UndefValue::get(CI2->getType()); // X / 0 == undef
break;
case Instruction::URem:
case Instruction::SRem:
if (CI2->equalsInt(1))
return Constant::getNullValue(CI2->getType()); // X % 1 == 0
if (CI2->equalsInt(0))
return UndefValue::get(CI2->getType()); // X % 0 == undef
break;
case Instruction::And:
if (CI2->isZero()) return C2; // X & 0 == 0
if (CI2->isAllOnesValue())
return C1; // X & -1 == X
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
// (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
if (CE1->getOpcode() == Instruction::ZExt) {
unsigned DstWidth = CI2->getType()->getBitWidth();
unsigned SrcWidth =
CE1->getOperand(0)->getType()->getPrimitiveSizeInBits();
APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth));
if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits)
return C1;
}
// If and'ing the address of a global with a constant, fold it.
if (CE1->getOpcode() == Instruction::PtrToInt &&
isa<GlobalValue>(CE1->getOperand(0))) {
GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
// Functions are at least 4-byte aligned.
unsigned GVAlign = GV->getAlignment();
if (isa<Function>(GV))
GVAlign = std::max(GVAlign, 4U);
if (GVAlign > 1) {
unsigned DstWidth = CI2->getType()->getBitWidth();
unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign));
APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
// If checking bits we know are clear, return zero.
if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
return Constant::getNullValue(CI2->getType());
}
}
}
break;
case Instruction::Or:
if (CI2->equalsInt(0)) return C1; // X | 0 == X
if (CI2->isAllOnesValue())
return C2; // X | -1 == -1
break;
case Instruction::Xor:
if (CI2->equalsInt(0)) return C1; // X ^ 0 == X
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
switch (CE1->getOpcode()) {
default: break;
case Instruction::ICmp:
case Instruction::FCmp:
// cmp pred ^ true -> cmp !pred
assert(CI2->equalsInt(1));
CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate();
pred = CmpInst::getInversePredicate(pred);
return ConstantExpr::getCompare(pred, CE1->getOperand(0),
CE1->getOperand(1));
}
}
break;
case Instruction::AShr:
// ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
return ConstantExpr::getLShr(C1, C2);
break;
}
}
// At this point we know neither constant is an UndefValue.
if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
using namespace APIntOps;
const APInt &C1V = CI1->getValue();
const APInt &C2V = CI2->getValue();
switch (Opcode) {
default:
break;
case Instruction::Add:
return ConstantInt::get(Context, C1V + C2V);
case Instruction::Sub:
return ConstantInt::get(Context, C1V - C2V);
case Instruction::Mul:
return ConstantInt::get(Context, C1V * C2V);
case Instruction::UDiv:
assert(!CI2->isNullValue() && "Div by zero handled above");
return ConstantInt::get(Context, C1V.udiv(C2V));
case Instruction::SDiv:
assert(!CI2->isNullValue() && "Div by zero handled above");
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef
return ConstantInt::get(Context, C1V.sdiv(C2V));
case Instruction::URem:
assert(!CI2->isNullValue() && "Div by zero handled above");
return ConstantInt::get(Context, C1V.urem(C2V));
case Instruction::SRem:
assert(!CI2->isNullValue() && "Div by zero handled above");
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef
return ConstantInt::get(Context, C1V.srem(C2V));
case Instruction::And:
return ConstantInt::get(Context, C1V & C2V);
case Instruction::Or:
return ConstantInt::get(Context, C1V | C2V);
case Instruction::Xor:
return ConstantInt::get(Context, C1V ^ C2V);
case Instruction::Shl: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(Context, C1V.shl(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
}
case Instruction::LShr: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(Context, C1V.lshr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
}
case Instruction::AShr: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(Context, C1V.ashr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
}
}
}
switch (Opcode) {
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
if (CI1->equalsInt(0)) return C1;
break;
default:
break;
}
} else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
APFloat C1V = CFP1->getValueAPF();
APFloat C2V = CFP2->getValueAPF();
APFloat C3V = C1V; // copy for modification
switch (Opcode) {
default:
break;
case Instruction::FAdd:
(void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, C3V);
case Instruction::FSub:
(void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, C3V);
case Instruction::FMul:
(void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, C3V);
case Instruction::FDiv:
(void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, C3V);
case Instruction::FRem:
(void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
return ConstantFP::get(Context, C3V);
}
}
} else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
(CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
std::vector<Constant*> Res;
const Type* EltTy = VTy->getElementType();
Constant *C1 = 0;
Constant *C2 = 0;
switch (Opcode) {
default:
break;
case Instruction::Add:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getAdd(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::FAdd:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getFAdd(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::Sub:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getSub(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::FSub:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getFSub(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::Mul:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getMul(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::FMul:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getFMul(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::UDiv:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getUDiv(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::SDiv:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getSDiv(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::FDiv:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getFDiv(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::URem:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getURem(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::SRem:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getSRem(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::FRem:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getFRem(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::And:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getAnd(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::Or:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getOr(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::Xor:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getXor(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::LShr:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getLShr(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::AShr:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getAShr(C1, C2));
}
return ConstantVector::get(Res);
case Instruction::Shl:
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
C1 = CP1 ? CP1->getOperand(i) : Constant::getNullValue(EltTy);
C2 = CP2 ? CP2->getOperand(i) : Constant::getNullValue(EltTy);
Res.push_back(ConstantExpr::getShl(C1, C2));
}
return ConstantVector::get(Res);
}
}
}
if (isa<ConstantExpr>(C1)) {
// There are many possible foldings we could do here. We should probably
// at least fold add of a pointer with an integer into the appropriate
// getelementptr. This will improve alias analysis a bit.
} else if (isa<ConstantExpr>(C2)) {
// If C2 is a constant expr and C1 isn't, flop them around and fold the
// other way if possible.
switch (Opcode) {
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// No change of opcode required.
return ConstantFoldBinaryInstruction(Context, Opcode, C2, C1);
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::SDiv:
case Instruction::UDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
default: // These instructions cannot be flopped around.
break;
}
}
// i1 can be simplified in many cases.
if (C1->getType() == Type::getInt1Ty(Context)) {
switch (Opcode) {
case Instruction::Add:
case Instruction::Sub:
return ConstantExpr::getXor(C1, C2);
case Instruction::Mul:
return ConstantExpr::getAnd(C1, C2);
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
// We can assume that C2 == 0. If it were one the result would be
// undefined because the shift value is as large as the bitwidth.
return C1;
case Instruction::SDiv:
case Instruction::UDiv:
// We can assume that C2 == 1. If it were zero the result would be
// undefined through division by zero.
return C1;
case Instruction::URem:
case Instruction::SRem:
// We can assume that C2 == 1. If it were zero the result would be
// undefined through division by zero.
return ConstantInt::getFalse(Context);
default:
break;
}
}
// We don't know how to fold this.
return 0;
}
/// isZeroSizedType - This type is zero sized if its an array or structure of
/// zero sized types. The only leaf zero sized type is an empty structure.
static bool isMaybeZeroSizedType(const Type *Ty) {
if (isa<OpaqueType>(Ty)) return true; // Can't say.
if (const StructType *STy = dyn_cast<StructType>(Ty)) {
// If all of elements have zero size, this does too.
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
if (!isMaybeZeroSizedType(STy->getElementType(i))) return false;
return true;
} else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
return isMaybeZeroSizedType(ATy->getElementType());
}
return false;
}
/// IdxCompare - Compare the two constants as though they were getelementptr
/// indices. This allows coersion of the types to be the same thing.
///
/// If the two constants are the "same" (after coersion), return 0. If the
/// first is less than the second, return -1, if the second is less than the
/// first, return 1. If the constants are not integral, return -2.
///
static int IdxCompare(LLVMContext &Context, Constant *C1, Constant *C2,
const Type *ElTy) {
if (C1 == C2) return 0;
// Ok, we found a different index. If they are not ConstantInt, we can't do
// anything with them.
if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2))
return -2; // don't know!
// Ok, we have two differing integer indices. Sign extend them to be the same
// type. Long is always big enough, so we use it.
if (C1->getType() != Type::getInt64Ty(Context))
C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(Context));
if (C2->getType() != Type::getInt64Ty(Context))
C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(Context));
if (C1 == C2) return 0; // They are equal
// If the type being indexed over is really just a zero sized type, there is
// no pointer difference being made here.
if (isMaybeZeroSizedType(ElTy))
return -2; // dunno.
// If they are really different, now that they are the same type, then we
// found a difference!
if (cast<ConstantInt>(C1)->getSExtValue() <
cast<ConstantInt>(C2)->getSExtValue())
return -1;
else
return 1;
}
/// evaluateFCmpRelation - This function determines if there is anything we can
/// decide about the two constants provided. This doesn't need to handle simple
/// things like ConstantFP comparisons, but should instead handle ConstantExprs.
/// If we can determine that the two constants have a particular relation to
/// each other, we should return the corresponding FCmpInst predicate,
/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in
/// ConstantFoldCompareInstruction.
///
/// To simplify this code we canonicalize the relation so that the first
/// operand is always the most "complex" of the two. We consider ConstantFP
/// to be the simplest, and ConstantExprs to be the most complex.
static FCmpInst::Predicate evaluateFCmpRelation(LLVMContext &Context,
Constant *V1, Constant *V2) {
assert(V1->getType() == V2->getType() &&
"Cannot compare values of different types!");
// No compile-time operations on this type yet.
if (V1->getType() == Type::getPPC_FP128Ty(Context))
return FCmpInst::BAD_FCMP_PREDICATE;
// Handle degenerate case quickly
if (V1 == V2) return FCmpInst::FCMP_OEQ;
if (!isa<ConstantExpr>(V1)) {
if (!isa<ConstantExpr>(V2)) {
// We distilled thisUse the standard constant folder for a few cases
ConstantInt *R = 0;
R = dyn_cast<ConstantInt>(
ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2));
if (R && !R->isZero())
return FCmpInst::FCMP_OEQ;
R = dyn_cast<ConstantInt>(
ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2));
if (R && !R->isZero())
return FCmpInst::FCMP_OLT;
R = dyn_cast<ConstantInt>(
ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2));
if (R && !R->isZero())
return FCmpInst::FCMP_OGT;
// Nothing more we can do
return FCmpInst::BAD_FCMP_PREDICATE;
}
// If the first operand is simple and second is ConstantExpr, swap operands.
FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(Context, V2, V1);
if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE)
return FCmpInst::getSwappedPredicate(SwappedRelation);
} else {
// Ok, the LHS is known to be a constantexpr. The RHS can be any of a
// constantexpr or a simple constant.
ConstantExpr *CE1 = cast<ConstantExpr>(V1);
switch (CE1->getOpcode()) {
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::UIToFP:
case Instruction::SIToFP:
// We might be able to do something with these but we don't right now.
break;
default:
break;
}
}
// There are MANY other foldings that we could perform here. They will
// probably be added on demand, as they seem needed.
return FCmpInst::BAD_FCMP_PREDICATE;
}
/// evaluateICmpRelation - This function determines if there is anything we can
/// decide about the two constants provided. This doesn't need to handle simple
/// things like integer comparisons, but should instead handle ConstantExprs
/// and GlobalValues. If we can determine that the two constants have a
/// particular relation to each other, we should return the corresponding ICmp
/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.
///
/// To simplify this code we canonicalize the relation so that the first
/// operand is always the most "complex" of the two. We consider simple
/// constants (like ConstantInt) to be the simplest, followed by
/// GlobalValues, followed by ConstantExpr's (the most complex).
///
static ICmpInst::Predicate evaluateICmpRelation(LLVMContext &Context,
Constant *V1,
Constant *V2,
bool isSigned) {
assert(V1->getType() == V2->getType() &&
"Cannot compare different types of values!");
if (V1 == V2) return ICmpInst::ICMP_EQ;
if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) {
if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) {
// We distilled this down to a simple case, use the standard constant
// folder.
ConstantInt *R = 0;
ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2));
if (R && !R->isZero())
return pred;
// If we couldn't figure it out, bail.
return ICmpInst::BAD_ICMP_PREDICATE;
}
// If the first operand is simple, swap operands.
ICmpInst::Predicate SwappedRelation =
evaluateICmpRelation(Context, V2, V1, isSigned);
if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
return ICmpInst::getSwappedPredicate(SwappedRelation);
} else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) {
if (isa<ConstantExpr>(V2)) { // Swap as necessary.
ICmpInst::Predicate SwappedRelation =
evaluateICmpRelation(Context, V2, V1, isSigned);
if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
return ICmpInst::getSwappedPredicate(SwappedRelation);
else
return ICmpInst::BAD_ICMP_PREDICATE;
}
// Now we know that the RHS is a GlobalValue or simple constant,
// which (since the types must match) means that it's a ConstantPointerNull.
if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
// Don't try to decide equality of aliases.
if (!isa<GlobalAlias>(CPR1) && !isa<GlobalAlias>(CPR2))
if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
return ICmpInst::ICMP_NE;
} else {
assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
// GlobalVals can never be null. Don't try to evaluate aliases.
if (!CPR1->hasExternalWeakLinkage() && !isa<GlobalAlias>(CPR1))
return ICmpInst::ICMP_NE;
}
} else {
// Ok, the LHS is known to be a constantexpr. The RHS can be any of a
// constantexpr, a CPR, or a simple constant.
ConstantExpr *CE1 = cast<ConstantExpr>(V1);
Constant *CE1Op0 = CE1->getOperand(0);
switch (CE1->getOpcode()) {
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
break; // We can't evaluate floating point casts or truncations.
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::BitCast:
case Instruction::ZExt:
case Instruction::SExt:
// If the cast is not actually changing bits, and the second operand is a
// null pointer, do the comparison with the pre-casted value.
if (V2->isNullValue() &&
(isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) {
if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
return evaluateICmpRelation(Context, CE1Op0,
Constant::getNullValue(CE1Op0->getType()),
isSigned);
}
break;
case Instruction::GetElementPtr:
// Ok, since this is a getelementptr, we know that the constant has a
// pointer type. Check the various cases.
if (isa<ConstantPointerNull>(V2)) {
// If we are comparing a GEP to a null pointer, check to see if the base
// of the GEP equals the null pointer.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
if (GV->hasExternalWeakLinkage())
// Weak linkage GVals could be zero or not. We're comparing that
// to null pointer so its greater-or-equal
return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE;
else
// If its not weak linkage, the GVal must have a non-zero address
// so the result is greater-than
return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
} else if (isa<ConstantPointerNull>(CE1Op0)) {
// If we are indexing from a null pointer, check to see if we have any
// non-zero indices.
for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i)
if (!CE1->getOperand(i)->isNullValue())
// Offsetting from null, must not be equal.
return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
// Only zero indexes from null, must still be zero.
return ICmpInst::ICMP_EQ;
}
// Otherwise, we can't really say if the first operand is null or not.
} else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) {
if (isa<ConstantPointerNull>(CE1Op0)) {
if (CPR2->hasExternalWeakLinkage())
// Weak linkage GVals could be zero or not. We're comparing it to
// a null pointer, so its less-or-equal
return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE;
else
// If its not weak linkage, the GVal must have a non-zero address
// so the result is less-than
return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
} else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) {
if (CPR1 == CPR2) {
// If this is a getelementptr of the same global, then it must be
// different. Because the types must match, the getelementptr could
// only have at most one index, and because we fold getelementptr's
// with a single zero index, it must be nonzero.
assert(CE1->getNumOperands() == 2 &&
!CE1->getOperand(1)->isNullValue() &&
"Suprising getelementptr!");
return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
} else {
// If they are different globals, we don't know what the value is,
// but they can't be equal.
return ICmpInst::ICMP_NE;
}
}
} else {
ConstantExpr *CE2 = cast<ConstantExpr>(V2);
Constant *CE2Op0 = CE2->getOperand(0);
// There are MANY other foldings that we could perform here. They will
// probably be added on demand, as they seem needed.
switch (CE2->getOpcode()) {
default: break;
case Instruction::GetElementPtr:
// By far the most common case to handle is when the base pointers are
// obviously to the same or different globals.
if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal
return ICmpInst::ICMP_NE;
// Ok, we know that both getelementptr instructions are based on the
// same global. From this, we can precisely determine the relative
// ordering of the resultant pointers.
unsigned i = 1;
// The logic below assumes that the result of the comparison
// can be determined by finding the first index that differs.
// This doesn't work if there is over-indexing in any
// subsequent indices, so check for that case first.
if (!CE1->isGEPWithNoNotionalOverIndexing() ||
!CE2->isGEPWithNoNotionalOverIndexing())
return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
// Compare all of the operands the GEP's have in common.
gep_type_iterator GTI = gep_type_begin(CE1);
for (;i != CE1->getNumOperands() && i != CE2->getNumOperands();
++i, ++GTI)
switch (IdxCompare(Context, CE1->getOperand(i),
CE2->getOperand(i), GTI.getIndexedType())) {
case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT;
case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT;
case -2: return ICmpInst::BAD_ICMP_PREDICATE;
}
// Ok, we ran out of things they have in common. If any leftovers
// are non-zero then we have a difference, otherwise we are equal.
for (; i < CE1->getNumOperands(); ++i)
if (!CE1->getOperand(i)->isNullValue()) {
if (isa<ConstantInt>(CE1->getOperand(i)))
return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
else
return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
}
for (; i < CE2->getNumOperands(); ++i)
if (!CE2->getOperand(i)->isNullValue()) {
if (isa<ConstantInt>(CE2->getOperand(i)))
return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
else
return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal.
}
return ICmpInst::ICMP_EQ;
}
}
}
default:
break;
}
}
return ICmpInst::BAD_ICMP_PREDICATE;
}
Constant *llvm::ConstantFoldCompareInstruction(LLVMContext &Context,
unsigned short pred,
Constant *C1, Constant *C2) {
const Type *ResultTy;
if (const VectorType *VT = dyn_cast<VectorType>(C1->getType()))
ResultTy = VectorType::get(Type::getInt1Ty(Context), VT->getNumElements());
else
ResultTy = Type::getInt1Ty(Context);
// Fold FCMP_FALSE/FCMP_TRUE unconditionally.
if (pred == FCmpInst::FCMP_FALSE)
return Constant::getNullValue(ResultTy);
if (pred == FCmpInst::FCMP_TRUE)
return Constant::getAllOnesValue(ResultTy);
// Handle some degenerate cases first
if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
return UndefValue::get(ResultTy);
// No compile-time operations on this type yet.
if (C1->getType() == Type::getPPC_FP128Ty(Context))
return 0;
// icmp eq/ne(null,GV) -> false/true
if (C1->isNullValue()) {
if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
// Don't try to evaluate aliases. External weak GV can be null.
if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
if (pred == ICmpInst::ICMP_EQ)
return ConstantInt::getFalse(Context);
else if (pred == ICmpInst::ICMP_NE)
return ConstantInt::getTrue(Context);
}
// icmp eq/ne(GV,null) -> false/true
} else if (C2->isNullValue()) {
if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
// Don't try to evaluate aliases. External weak GV can be null.
if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) {
if (pred == ICmpInst::ICMP_EQ)
return ConstantInt::getFalse(Context);
else if (pred == ICmpInst::ICMP_NE)
return ConstantInt::getTrue(Context);
}
}
// If the comparison is a comparison between two i1's, simplify it.
if (C1->getType() == Type::getInt1Ty(Context)) {
switch(pred) {
case ICmpInst::ICMP_EQ:
if (isa<ConstantInt>(C2))
return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
case ICmpInst::ICMP_NE:
return ConstantExpr::getXor(C1, C2);
default:
break;
}
}
if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
APInt V1 = cast<ConstantInt>(C1)->getValue();
APInt V2 = cast<ConstantInt>(C2)->getValue();
switch (pred) {
default: llvm_unreachable("Invalid ICmp Predicate"); return 0;
case ICmpInst::ICMP_EQ:
return ConstantInt::get(Type::getInt1Ty(Context), V1 == V2);
case ICmpInst::ICMP_NE:
return ConstantInt::get(Type::getInt1Ty(Context), V1 != V2);
case ICmpInst::ICMP_SLT:
return ConstantInt::get(Type::getInt1Ty(Context), V1.slt(V2));
case ICmpInst::ICMP_SGT:
return ConstantInt::get(Type::getInt1Ty(Context), V1.sgt(V2));
case ICmpInst::ICMP_SLE:
return ConstantInt::get(Type::getInt1Ty(Context), V1.sle(V2));
case ICmpInst::ICMP_SGE:
return ConstantInt::get(Type::getInt1Ty(Context), V1.sge(V2));
case ICmpInst::ICMP_ULT:
return ConstantInt::get(Type::getInt1Ty(Context), V1.ult(V2));
case ICmpInst::ICMP_UGT:
return ConstantInt::get(Type::getInt1Ty(Context), V1.ugt(V2));
case ICmpInst::ICMP_ULE:
return ConstantInt::get(Type::getInt1Ty(Context), V1.ule(V2));
case ICmpInst::ICMP_UGE:
return ConstantInt::get(Type::getInt1Ty(Context), V1.uge(V2));
}
} else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
APFloat C1V = cast<ConstantFP>(C1)->getValueAPF();
APFloat C2V = cast<ConstantFP>(C2)->getValueAPF();
APFloat::cmpResult R = C1V.compare(C2V);
switch (pred) {
default: llvm_unreachable("Invalid FCmp Predicate"); return 0;
case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(Context);
case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(Context);
case FCmpInst::FCMP_UNO:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpUnordered);
case FCmpInst::FCMP_ORD:
return ConstantInt::get(Type::getInt1Ty(Context), R!=APFloat::cmpUnordered);
case FCmpInst::FCMP_UEQ:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpUnordered ||
R==APFloat::cmpEqual);
case FCmpInst::FCMP_OEQ:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpEqual);
case FCmpInst::FCMP_UNE:
return ConstantInt::get(Type::getInt1Ty(Context), R!=APFloat::cmpEqual);
case FCmpInst::FCMP_ONE:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpLessThan ||
R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_ULT:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpUnordered ||
R==APFloat::cmpLessThan);
case FCmpInst::FCMP_OLT:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpLessThan);
case FCmpInst::FCMP_UGT:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpUnordered ||
R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_OGT:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_ULE:
return ConstantInt::get(Type::getInt1Ty(Context), R!=APFloat::cmpGreaterThan);
case FCmpInst::FCMP_OLE:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpLessThan ||
R==APFloat::cmpEqual);
case FCmpInst::FCMP_UGE:
return ConstantInt::get(Type::getInt1Ty(Context), R!=APFloat::cmpLessThan);
case FCmpInst::FCMP_OGE:
return ConstantInt::get(Type::getInt1Ty(Context), R==APFloat::cmpGreaterThan ||
R==APFloat::cmpEqual);
}
} else if (isa<VectorType>(C1->getType())) {
SmallVector<Constant*, 16> C1Elts, C2Elts;
C1->getVectorElements(Context, C1Elts);
C2->getVectorElements(Context, C2Elts);
// If we can constant fold the comparison of each element, constant fold
// the whole vector comparison.
SmallVector<Constant*, 4> ResElts;
for (unsigned i = 0, e = C1Elts.size(); i != e; ++i) {
// Compare the elements, producing an i1 result or constant expr.
ResElts.push_back(
ConstantExpr::getCompare(pred, C1Elts[i], C2Elts[i]));
}
return ConstantVector::get(&ResElts[0], ResElts.size());
}
if (C1->getType()->isFloatingPoint()) {
int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
switch (evaluateFCmpRelation(Context, C1, C2)) {
default: llvm_unreachable("Unknown relation!");
case FCmpInst::FCMP_UNO:
case FCmpInst::FCMP_ORD:
case FCmpInst::FCMP_UEQ:
case FCmpInst::FCMP_UNE:
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_ULE:
case FCmpInst::FCMP_UGE:
case FCmpInst::FCMP_TRUE:
case FCmpInst::FCMP_FALSE:
case FCmpInst::BAD_FCMP_PREDICATE:
break; // Couldn't determine anything about these constants.
case FCmpInst::FCMP_OEQ: // We know that C1 == C2
Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
break;
case FCmpInst::FCMP_OLT: // We know that C1 < C2
Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
break;
case FCmpInst::FCMP_OGT: // We know that C1 > C2
Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
break;
case FCmpInst::FCMP_OLE: // We know that C1 <= C2
// We can only partially decide this relation.
if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
Result = 0;
else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
Result = 1;
break;
case FCmpInst::FCMP_OGE: // We known that C1 >= C2
// We can only partially decide this relation.
if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
Result = 0;
else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
Result = 1;
break;
case ICmpInst::ICMP_NE: // We know that C1 != C2
// We can only partially decide this relation.
if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ)
Result = 0;
else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
Result = 1;
break;
}
// If we evaluated the result, return it now.
if (Result != -1)
return ConstantInt::get(Type::getInt1Ty(Context), Result);
} else {
// Evaluate the relation between the two constants, per the predicate.
int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
switch (evaluateICmpRelation(Context, C1, C2, CmpInst::isSigned(pred))) {
default: llvm_unreachable("Unknown relational!");
case ICmpInst::BAD_ICMP_PREDICATE:
break; // Couldn't determine anything about these constants.
case ICmpInst::ICMP_EQ: // We know the constants are equal!
// If we know the constants are equal, we can decide the result of this
// computation precisely.
Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred);
break;
case ICmpInst::ICMP_ULT:
switch (pred) {
case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
Result = 1; break;
case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
Result = 0; break;
}
break;
case ICmpInst::ICMP_SLT:
switch (pred) {
case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
Result = 1; break;
case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
Result = 0; break;
}
break;
case ICmpInst::ICMP_UGT:
switch (pred) {
case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
Result = 1; break;
case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
Result = 0; break;
}
break;
case ICmpInst::ICMP_SGT:
switch (pred) {
case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
Result = 1; break;
case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
Result = 0; break;
}
break;
case ICmpInst::ICMP_ULE:
if (pred == ICmpInst::ICMP_UGT) Result = 0;
if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1;
break;
case ICmpInst::ICMP_SLE:
if (pred == ICmpInst::ICMP_SGT) Result = 0;
if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1;
break;
case ICmpInst::ICMP_UGE:
if (pred == ICmpInst::ICMP_ULT) Result = 0;
if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1;
break;
case ICmpInst::ICMP_SGE:
if (pred == ICmpInst::ICMP_SLT) Result = 0;
if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1;
break;
case ICmpInst::ICMP_NE:
if (pred == ICmpInst::ICMP_EQ) Result = 0;
if (pred == ICmpInst::ICMP_NE) Result = 1;
break;
}
// If we evaluated the result, return it now.
if (Result != -1)
return ConstantInt::get(Type::getInt1Ty(Context), Result);
// If the right hand side is a bitcast, try using its inverse to simplify
// it by moving it to the left hand side.
if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
if (CE2->getOpcode() == Instruction::BitCast) {
Constant *CE2Op0 = CE2->getOperand(0);
Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
}
}
// If the left hand side is an extension, try eliminating it.
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
if (CE1->getOpcode() == Instruction::SExt ||
CE1->getOpcode() == Instruction::ZExt) {
Constant *CE1Op0 = CE1->getOperand(0);
Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType());
if (CE1Inverse == CE1Op0) {
// Check whether we can safely truncate the right hand side.
Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType());
if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) {
return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse);
}
}
}
}
if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
// If C2 is a constant expr and C1 isn't, flip them around and fold the
// other way if possible.
switch (pred) {
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_NE:
// No change of predicate required.
return ConstantFoldCompareInstruction(Context, pred, C2, C1);
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_ULE:
case ICmpInst::ICMP_SLE:
case ICmpInst::ICMP_UGE:
case ICmpInst::ICMP_SGE:
// Change the predicate as necessary to swap the operands.
pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred);
return ConstantFoldCompareInstruction(Context, pred, C2, C1);
default: // These predicates cannot be flopped around.
break;
}
}
}
return 0;
}
/// isInBoundsIndices - Test whether the given sequence of *normalized* indices
/// is "inbounds".
static bool isInBoundsIndices(Constant *const *Idxs, size_t NumIdx) {
// No indices means nothing that could be out of bounds.
if (NumIdx == 0) return true;
// If the first index is zero, it's in bounds.
if (Idxs[0]->isNullValue()) return true;
// If the first index is one and all the rest are zero, it's in bounds,
// by the one-past-the-end rule.
if (!cast<ConstantInt>(Idxs[0])->isOne())
return false;
for (unsigned i = 1, e = NumIdx; i != e; ++i)
if (!Idxs[i]->isNullValue())
return false;
return true;
}
Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
Constant *C,
bool inBounds,
Constant* const *Idxs,
unsigned NumIdx) {
if (NumIdx == 0 ||
(NumIdx == 1 && Idxs[0]->isNullValue()))
return C;
if (isa<UndefValue>(C)) {
const PointerType *Ptr = cast<PointerType>(C->getType());
const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
(Value **)Idxs,
(Value **)Idxs+NumIdx);
assert(Ty != 0 && "Invalid indices for GEP!");
return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace()));
}
Constant *Idx0 = Idxs[0];
if (C->isNullValue()) {
bool isNull = true;
for (unsigned i = 0, e = NumIdx; i != e; ++i)
if (!Idxs[i]->isNullValue()) {
isNull = false;
break;
}
if (isNull) {
const PointerType *Ptr = cast<PointerType>(C->getType());
const Type *Ty = GetElementPtrInst::getIndexedType(Ptr,
(Value**)Idxs,
(Value**)Idxs+NumIdx);
assert(Ty != 0 && "Invalid indices for GEP!");
return ConstantPointerNull::get(
PointerType::get(Ty,Ptr->getAddressSpace()));
}
}
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
//
if (CE->getOpcode() == Instruction::GetElementPtr) {
const Type *LastTy = 0;
for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
I != E; ++I)
LastTy = *I;
if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) {
SmallVector<Value*, 16> NewIndices;
NewIndices.reserve(NumIdx + CE->getNumOperands());
for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i)
NewIndices.push_back(CE->getOperand(i));
// Add the last index of the source with the first index of the new GEP.
// Make sure to handle the case when they are actually different types.
Constant *Combined = CE->getOperand(CE->getNumOperands()-1);
// Otherwise it must be an array.
if (!Idx0->isNullValue()) {
const Type *IdxTy = Combined->getType();
if (IdxTy != Idx0->getType()) {
Constant *C1 =
ConstantExpr::getSExtOrBitCast(Idx0, Type::getInt64Ty(Context));
Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
Type::getInt64Ty(Context));
Combined = ConstantExpr::get(Instruction::Add, C1, C2);
} else {
Combined =
ConstantExpr::get(Instruction::Add, Idx0, Combined);
}
}
NewIndices.push_back(Combined);
NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
return (inBounds && cast<GEPOperator>(CE)->isInBounds()) ?
ConstantExpr::getInBoundsGetElementPtr(CE->getOperand(0),
&NewIndices[0],
NewIndices.size()) :
ConstantExpr::getGetElementPtr(CE->getOperand(0),
&NewIndices[0],
NewIndices.size());
}
}
// Implement folding of:
// int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*),
// long 0, long 0)
// To: int* getelementptr ([3 x int]* %X, long 0, long 0)
//
if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
if (const PointerType *SPT =
dyn_cast<PointerType>(CE->getOperand(0)->getType()))
if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
if (const ArrayType *CAT =
dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType()))
if (CAT->getElementType() == SAT->getElementType())
return inBounds ?
ConstantExpr::getInBoundsGetElementPtr(
(Constant*)CE->getOperand(0), Idxs, NumIdx) :
ConstantExpr::getGetElementPtr(
(Constant*)CE->getOperand(0), Idxs, NumIdx);
}
// Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
// Into: inttoptr (i64 0 to i8*)
// This happens with pointers to member functions in C++.
if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
cast<PointerType>(CE->getType())->getElementType() == Type::getInt8Ty(Context)) {
Constant *Base = CE->getOperand(0);
Constant *Offset = Idxs[0];
// Convert the smaller integer to the larger type.
if (Offset->getType()->getPrimitiveSizeInBits() <
Base->getType()->getPrimitiveSizeInBits())
Offset = ConstantExpr::getSExt(Offset, Base->getType());
else if (Base->getType()->getPrimitiveSizeInBits() <
Offset->getType()->getPrimitiveSizeInBits())
Base = ConstantExpr::getZExt(Base, Offset->getType());
Base = ConstantExpr::getAdd(Base, Offset);
return ConstantExpr::getIntToPtr(Base, CE->getType());
}
}
// Check to see if any array indices are not within the corresponding
// notional array bounds. If so, try to determine if they can be factored
// out into preceding dimensions.
bool Unknown = false;
SmallVector<Constant *, 8> NewIdxs;
const Type *Ty = C->getType();
const Type *Prev = 0;
for (unsigned i = 0; i != NumIdx;
Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty))
if (ATy->getNumElements() <= INT64_MAX &&
ATy->getNumElements() != 0 &&
CI->getSExtValue() >= (int64_t)ATy->getNumElements()) {
if (isa<SequentialType>(Prev)) {
// It's out of range, but we can factor it into the prior
// dimension.
NewIdxs.resize(NumIdx);
ConstantInt *Factor = ConstantInt::get(CI->getType(),
ATy->getNumElements());
NewIdxs[i] = ConstantExpr::getSRem(CI, Factor);
Constant *PrevIdx = Idxs[i-1];
Constant *Div = ConstantExpr::getSDiv(CI, Factor);
// Before adding, extend both operands to i64 to avoid
// overflow trouble.
if (PrevIdx->getType() != Type::getInt64Ty(Context))
PrevIdx = ConstantExpr::getSExt(PrevIdx,
Type::getInt64Ty(Context));
if (Div->getType() != Type::getInt64Ty(Context))
Div = ConstantExpr::getSExt(Div,
Type::getInt64Ty(Context));
NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div);
} else {
// It's out of range, but the prior dimension is a struct
// so we can't do anything about it.
Unknown = true;
}
}
} else {
// We don't know if it's in range or not.
Unknown = true;
}
}
// If we did any factoring, start over with the adjusted indices.
if (!NewIdxs.empty()) {
for (unsigned i = 0; i != NumIdx; ++i)
if (!NewIdxs[i]) NewIdxs[i] = Idxs[i];
return inBounds ?
ConstantExpr::getInBoundsGetElementPtr(C, NewIdxs.data(),
NewIdxs.size()) :
ConstantExpr::getGetElementPtr(C, NewIdxs.data(), NewIdxs.size());
}
// If all indices are known integers and normalized, we can do a simple
// check for the "inbounds" property.
if (!Unknown && !inBounds &&
isa<GlobalVariable>(C) && isInBoundsIndices(Idxs, NumIdx))
return ConstantExpr::getInBoundsGetElementPtr(C, Idxs, NumIdx);
return 0;
}
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