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llvm-6502/lib/VMCore/ConstantFold.cpp
Owen Anderson 0a5372ed3e Begin the painful process of tearing apart the rat'ss nest that is Constants.cpp and ConstantFold.cpp. 
This involves temporarily hard wiring some parts to use the global context.  This isn't ideal, but it's
the only way I could figure out to make this process vaguely incremental.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75445 91177308-0d34-0410-b5e6-96231b3b80d8
2009-07-13 04:09:18 +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
// template-based folder for simple primitive constants like ConstantInt, and
// the special case hackery that we use to symbolically evaluate expressions
// that use ConstantExprs.
//
//===----------------------------------------------------------------------===//
#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/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(Context.getConstantExprBitCast(CV->getOperand(i),
DstEltTy));
return Context.getConstantVector(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
const 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::Int64Ty);
}
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;
IdxList.push_back(Context.getNullValue(Type::Int32Ty));
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(Context.getNullValue(Type::Int32Ty));
} 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(IdxList[0]);
} else {
break;
}
}
if (ElTy == DPTy->getElementType())
return Context.getConstantExprGetElementPtr(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 Context.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 Context.getConstantExprBitCast(
Context.getConstantVector(&V, 1), DestPTy);
}
// Finally, implement bitcast folding now. The code below doesn't handle
// bitcast right.
if (isa<ConstantPointerNull>(V)) // ptr->ptr cast.
return Context.getConstantPointerNull(cast<PointerType>(DestTy));
// Handle integral constant input.
if (const 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 Context.getConstantFP(APFloat(CI->getValue(),
DestTy != Type::PPC_FP128Ty));
// Otherwise, can't fold this (vector?)
return 0;
}
// Handle ConstantFP input.
if (const ConstantFP *FP = dyn_cast<ConstantFP>(V))
// FP -> Integral.
return Context.getConstantInt(FP->getValueAPF().bitcastToAPInt());
return 0;
}
Constant *llvm::ConstantFoldCastInstruction(LLVMContext &Context,
unsigned opc, const 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 Context.getNullValue(DestTy);
return Context.getUndef(DestTy);
}
// No compile-time operations on this type yet.
if (V->getType() == Type::PPC_FP128Ty || DestTy == Type::PPC_FP128Ty)
return 0;
// If the cast operand is a constant expression, there's a few things we can
// do to try to simplify it.
if (const 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 Context.getConstantExprCast(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 Context.getConstantExprPointerCast(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 (const 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(Context.getConstantExprCast(opc,
CV->getOperand(i), DstEltTy));
return Context.getConstantVector(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 (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
bool ignored;
APFloat Val = FPC->getValueAPF();
Val.convert(DestTy == Type::FloatTy ? APFloat::IEEEsingle :
DestTy == Type::DoubleTy ? APFloat::IEEEdouble :
DestTy == Type::X86_FP80Ty ? APFloat::x87DoubleExtended :
DestTy == Type::FP128Ty ? APFloat::IEEEquad :
APFloat::Bogus,
APFloat::rmNearestTiesToEven, &ignored);
return Context.getConstantFP(Val);
}
return 0; // Can't fold.
case Instruction::FPToUI:
case Instruction::FPToSI:
if (const 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 Context.getConstantInt(Val);
}
return 0; // Can't fold.
case Instruction::IntToPtr: //always treated as unsigned
if (V->isNullValue()) // Is it an integral null value?
return Context.getConstantPointerNull(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 Context.getConstantInt(DestTy, 0);
return 0; // Other pointer types cannot be casted
case Instruction::UIToFP:
case Instruction::SIToFP:
if (const 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 Context.getConstantFP(apf);
}
return 0;
case Instruction::ZExt:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.zext(BitWidth);
return Context.getConstantInt(Result);
}
return 0;
case Instruction::SExt:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.sext(BitWidth);
return Context.getConstantInt(Result);
}
return 0;
case Instruction::Trunc:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Result(CI->getValue());
Result.trunc(BitWidth);
return Context.getConstantInt(Result);
}
return 0;
case Instruction::BitCast:
return FoldBitCast(Context, const_cast<Constant*>(V), DestTy);
default:
assert(!"Invalid CE CastInst opcode");
break;
}
LLVM_UNREACHABLE("Failed to cast constant expression");
return 0;
}
Constant *llvm::ConstantFoldSelectInstruction(LLVMContext&,
const Constant *Cond,
const Constant *V1,
const Constant *V2) {
if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond))
return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2);
if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2);
if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1);
if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1);
if (V1 == V2) return const_cast<Constant*>(V1);
return 0;
}
Constant *llvm::ConstantFoldExtractElementInstruction(LLVMContext &Context,
const Constant *Val,
const Constant *Idx) {
if (isa<UndefValue>(Val)) // ee(undef, x) -> undef
return Context.getUndef(cast<VectorType>(Val->getType())->getElementType());
if (Val->isNullValue()) // ee(zero, x) -> zero
return Context.getNullValue(
cast<VectorType>(Val->getType())->getElementType());
if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
if (const 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,
const Constant *Val,
const Constant *Elt,
const Constant *Idx) {
const 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 const_cast<Constant*>(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) {
const Constant *Op =
(idxVal == i) ? Elt : Context.getUndef(Elt->getType());
Ops.push_back(const_cast<Constant*>(Op));
}
return Context.getConstantVector(Ops);
}
if (isa<ConstantAggregateZero>(Val)) {
// Insertion of scalar constant into vector aggregate zero
// Optimize away insertion of zero
if (Elt->isNullValue())
return const_cast<Constant*>(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) {
const Constant *Op =
(idxVal == i) ? Elt : Context.getNullValue(Elt->getType());
Ops.push_back(const_cast<Constant*>(Op));
}
return Context.getConstantVector(Ops);
}
if (const 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) {
const Constant *Op =
(idxVal == i) ? Elt : cast<Constant>(CVal->getOperand(i));
Ops.push_back(const_cast<Constant*>(Op));
}
return Context.getConstantVector(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, const Constant *C,
unsigned EltNo) {
if (const ConstantVector *CV = dyn_cast<ConstantVector>(C))
return CV->getOperand(EltNo);
const Type *EltTy = cast<VectorType>(C->getType())->getElementType();
if (isa<ConstantAggregateZero>(C))
return Context.getNullValue(EltTy);
if (isa<UndefValue>(C))
return Context.getUndef(EltTy);
return 0;
}
Constant *llvm::ConstantFoldShuffleVectorInstruction(LLVMContext &Context,
const Constant *V1,
const Constant *V2,
const Constant *Mask) {
// Undefined shuffle mask -> undefined value.
if (isa<UndefValue>(Mask)) return Context.getUndef(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 = Context.getUndef(EltTy);
else if (ConstantInt *CI = dyn_cast<ConstantInt>(InElt)) {
unsigned Elt = CI->getZExtValue();
if (Elt >= SrcNumElts*2)
InElt = Context.getUndef(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 Context.getConstantVector(&Result[0], Result.size());
}
Constant *llvm::ConstantFoldExtractValueInstruction(LLVMContext &Context,
const Constant *Agg,
const unsigned *Idxs,
unsigned NumIdx) {
// Base case: no indices, so return the entire value.
if (NumIdx == 0)
return const_cast<Constant *>(Agg);
if (isa<UndefValue>(Agg)) // ev(undef, x) -> undef
return Context.getUndef(ExtractValueInst::getIndexedType(Agg->getType(),
Idxs,
Idxs + NumIdx));
if (isa<ConstantAggregateZero>(Agg)) // ev(0, x) -> 0
return
Context.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,
const Constant *Agg,
const Constant *Val,
const unsigned *Idxs,
unsigned NumIdx) {
// Base case: no indices, so replace the entire value.
if (NumIdx == 0)
return const_cast<Constant *>(Val);
if (isa<UndefValue>(Agg)) {
// Insertion of constant into aggregate undef
// Optimize away insertion of undef
if (isa<UndefValue>(Val))
return const_cast<Constant*>(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);
const Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context, Context.getUndef(MemberTy),
Val, Idxs+1, NumIdx-1) :
Context.getUndef(MemberTy);
Ops[i] = const_cast<Constant*>(Op);
}
if (isa<StructType>(AggTy))
return Context.getConstantStruct(Ops);
else
return Context.getConstantArray(cast<ArrayType>(AggTy), Ops);
}
if (isa<ConstantAggregateZero>(Agg)) {
// Insertion of constant into aggregate zero
// Optimize away insertion of zero
if (Val->isNullValue())
return const_cast<Constant*>(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);
const Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context,
Context.getNullValue(MemberTy),
Val, Idxs+1, NumIdx-1) :
Context.getNullValue(MemberTy);
Ops[i] = const_cast<Constant*>(Op);
}
if (isa<StructType>(AggTy))
return Context.getConstantStruct(Ops);
else
return Context.getConstantArray(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) {
const Constant *Op =
(*Idxs == i) ?
ConstantFoldInsertValueInstruction(Context, Agg->getOperand(i),
Val, Idxs+1, NumIdx-1) :
Agg->getOperand(i);
Ops[i] = const_cast<Constant*>(Op);
}
Constant *C;
if (isa<StructType>(Agg->getType()))
C = Context.getConstantStruct(Ops);
else
C = Context.getConstantArray(cast<ArrayType>(Agg->getType()), Ops);
return C;
}
return 0;
}
/// EvalVectorOp - Given two vector constants and a function pointer, apply the
/// function pointer to each element pair, producing a new ConstantVector
/// constant. Either or both of V1 and V2 may be NULL, meaning a
/// ConstantAggregateZero operand.
static Constant *EvalVectorOp(LLVMContext &Context, const ConstantVector *V1,
const ConstantVector *V2,
const VectorType *VTy,
Constant *(*FP)(Constant*, Constant*)) {
std::vector<Constant*> Res;
const Type *EltTy = VTy->getElementType();
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {
const Constant *C1 = V1 ? V1->getOperand(i) : Context.getNullValue(EltTy);
const Constant *C2 = V2 ? V2->getOperand(i) : Context.getNullValue(EltTy);
Res.push_back(FP(const_cast<Constant*>(C1),
const_cast<Constant*>(C2)));
}
return Context.getConstantVector(Res);
}
Constant *llvm::ConstantFoldBinaryInstruction(LLVMContext &Context,
unsigned Opcode,
const Constant *C1,
const Constant *C2) {
// No compile-time operations on this type yet.
if (C1->getType() == Type::PPC_FP128Ty)
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 Context.getNullValue(C1->getType());
// Fallthrough
case Instruction::Add:
case Instruction::Sub:
return Context.getUndef(C1->getType());
case Instruction::Mul:
case Instruction::And:
return Context.getNullValue(C1->getType());
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
if (!isa<UndefValue>(C2)) // undef / X -> 0
return Context.getNullValue(C1->getType());
return const_cast<Constant*>(C2); // X / undef -> undef
case Instruction::Or: // X | undef -> -1
if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType()))
return Context.getAllOnesValue(PTy);
return Context.getAllOnesValue(C1->getType());
case Instruction::LShr:
if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
return const_cast<Constant*>(C1); // undef lshr undef -> undef
return Context.getNullValue(C1->getType()); // X lshr undef -> 0
// undef lshr X -> 0
case Instruction::AShr:
if (!isa<UndefValue>(C2))
return const_cast<Constant*>(C1); // undef ashr X --> undef
else if (isa<UndefValue>(C1))
return const_cast<Constant*>(C1); // undef ashr undef -> undef
else
return const_cast<Constant*>(C1); // X ashr undef --> X
case Instruction::Shl:
// undef << X -> 0 or X << undef -> 0
return Context.getNullValue(C1->getType());
}
}
// Handle simplifications when the RHS is a constant int.
if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
switch (Opcode) {
case Instruction::Add:
if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X + 0 == X
break;
case Instruction::Sub:
if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X - 0 == X
break;
case Instruction::Mul:
if (CI2->equalsInt(0)) return const_cast<Constant*>(C2); // X * 0 == 0
if (CI2->equalsInt(1))
return const_cast<Constant*>(C1); // X * 1 == X
break;
case Instruction::UDiv:
case Instruction::SDiv:
if (CI2->equalsInt(1))
return const_cast<Constant*>(C1); // X / 1 == X
if (CI2->equalsInt(0))
return Context.getUndef(CI2->getType()); // X / 0 == undef
break;
case Instruction::URem:
case Instruction::SRem:
if (CI2->equalsInt(1))
return Context.getNullValue(CI2->getType()); // X % 1 == 0
if (CI2->equalsInt(0))
return Context.getUndef(CI2->getType()); // X % 0 == undef
break;
case Instruction::And:
if (CI2->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
if (CI2->isAllOnesValue())
return const_cast<Constant*>(C1); // X & -1 == X
if (const 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 const_cast<Constant*>(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 Context.getNullValue(CI2->getType());
}
}
}
break;
case Instruction::Or:
if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X | 0 == X
if (CI2->isAllOnesValue())
return const_cast<Constant*>(C2); // X | -1 == -1
break;
case Instruction::Xor:
if (CI2->equalsInt(0)) return const_cast<Constant*>(C1); // X ^ 0 == X
break;
case Instruction::AShr:
// ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1))
if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
return Context.getConstantExprLShr(const_cast<Constant*>(C1),
const_cast<Constant*>(C2));
break;
}
}
// At this point we know neither constant is an UndefValue.
if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
if (const 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 Context.getConstantInt(C1V + C2V);
case Instruction::Sub:
return Context.getConstantInt(C1V - C2V);
case Instruction::Mul:
return Context.getConstantInt(C1V * C2V);
case Instruction::UDiv:
assert(!CI2->isNullValue() && "Div by zero handled above");
return Context.getConstantInt(C1V.udiv(C2V));
case Instruction::SDiv:
assert(!CI2->isNullValue() && "Div by zero handled above");
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return Context.getUndef(CI1->getType()); // MIN_INT / -1 -> undef
return Context.getConstantInt(C1V.sdiv(C2V));
case Instruction::URem:
assert(!CI2->isNullValue() && "Div by zero handled above");
return Context.getConstantInt(C1V.urem(C2V));
case Instruction::SRem:
assert(!CI2->isNullValue() && "Div by zero handled above");
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return Context.getUndef(CI1->getType()); // MIN_INT % -1 -> undef
return Context.getConstantInt(C1V.srem(C2V));
case Instruction::And:
return Context.getConstantInt(C1V & C2V);
case Instruction::Or:
return Context.getConstantInt(C1V | C2V);
case Instruction::Xor:
return Context.getConstantInt(C1V ^ C2V);
case Instruction::Shl: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return Context.getConstantInt(C1V.shl(shiftAmt));
else
return Context.getUndef(C1->getType()); // too big shift is undef
}
case Instruction::LShr: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return Context.getConstantInt(C1V.lshr(shiftAmt));
else
return Context.getUndef(C1->getType()); // too big shift is undef
}
case Instruction::AShr: {
uint32_t shiftAmt = C2V.getZExtValue();
if (shiftAmt < C1V.getBitWidth())
return Context.getConstantInt(C1V.ashr(shiftAmt));
else
return Context.getUndef(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 const_cast<Constant*>(C1);
break;
default:
break;
}
} else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
if (const 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 Context.getConstantFP(C3V);
case Instruction::FSub:
(void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
return Context.getConstantFP(C3V);
case Instruction::FMul:
(void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
return Context.getConstantFP(C3V);
case Instruction::FDiv:
(void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
return Context.getConstantFP(C3V);
case Instruction::FRem:
(void)C3V.mod(C2V, APFloat::rmNearestTiesToEven);
return Context.getConstantFP(C3V);
}
}
} else if (const VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1);
const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2);
if ((CP1 != NULL || isa<ConstantAggregateZero>(C1)) &&
(CP2 != NULL || isa<ConstantAggregateZero>(C2))) {
switch (Opcode) {
default:
break;
case Instruction::Add:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getAdd);
case Instruction::FAdd:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getFAdd);
case Instruction::Sub:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getSub);
case Instruction::FSub:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getFSub);
case Instruction::Mul:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getMul);
case Instruction::FMul:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getFMul);
case Instruction::UDiv:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getUDiv);
case Instruction::SDiv:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getSDiv);
case Instruction::FDiv:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getFDiv);
case Instruction::URem:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getURem);
case Instruction::SRem:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getSRem);
case Instruction::FRem:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getFRem);
case Instruction::And:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getAnd);
case Instruction::Or:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getOr);
case Instruction::Xor:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getXor);
case Instruction::LShr:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getLShr);
case Instruction::AShr:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getAShr);
case Instruction::Shl:
return EvalVectorOp(Context, CP1, CP2, VTy, ConstantExpr::getShl);
}
}
}
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;
}
}
// 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::Int64Ty)
C1 = Context.getConstantExprSExt(C1, Type::Int64Ty);
if (C2->getType() != Type::Int64Ty)
C2 = Context.getConstantExprSExt(C2, Type::Int64Ty);
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,
const Constant *V1,
const 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::PPC_FP128Ty)
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;
Constant *C1 = const_cast<Constant*>(V1);
Constant *C2 = const_cast<Constant*>(V2);
R = dyn_cast<ConstantInt>(
Context.getConstantExprFCmp(FCmpInst::FCMP_OEQ, C1, C2));
if (R && !R->isZero())
return FCmpInst::FCMP_OEQ;
R = dyn_cast<ConstantInt>(
Context.getConstantExprFCmp(FCmpInst::FCMP_OLT, C1, C2));
if (R && !R->isZero())
return FCmpInst::FCMP_OLT;
R = dyn_cast<ConstantInt>(
Context.getConstantExprFCmp(FCmpInst::FCMP_OGT, C1, C2));
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.
const 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,
const Constant *V1,
const 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;
Constant *C1 = const_cast<Constant*>(V1);
Constant *C2 = const_cast<Constant*>(V2);
ICmpInst::Predicate pred = ICmpInst::ICMP_EQ;
R = dyn_cast<ConstantInt>(Context.getConstantExprICmp(pred, C1, C2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
R = dyn_cast<ConstantInt>(Context.getConstantExprICmp(pred, C1, C2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
R = dyn_cast<ConstantInt>(Context.getConstantExprICmp(pred, C1, C2));
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.
const ConstantExpr *CE1 = cast<ConstantExpr>(V1);
const 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())) {
bool sgnd = isSigned;
if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
return evaluateICmpRelation(Context, CE1Op0,
Context.getNullValue(CE1Op0->getType()),
sgnd);
}
// If the dest type is a pointer type, and the RHS is a constantexpr cast
// from the same type as the src of the LHS, evaluate the inputs. This is
// important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)",
// which happens a lot in compilers with tagged integers.
if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2))
if (CE2->isCast() && isa<PointerType>(CE1->getType()) &&
CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() &&
CE1->getOperand(0)->getType()->isInteger()) {
bool sgnd = isSigned;
if (CE1->getOpcode() == Instruction::ZExt) isSigned = false;
if (CE1->getOpcode() == Instruction::SExt) isSigned = true;
return evaluateICmpRelation(Context, CE1->getOperand(0),
CE2->getOperand(0), sgnd);
}
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 {
const ConstantExpr *CE2 = cast<ConstantExpr>(V2);
const 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;
// 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,
const Constant *C1,
const Constant *C2) {
const Type *ResultTy;
if (const VectorType *VT = dyn_cast<VectorType>(C1->getType()))
ResultTy = Context.getVectorType(Type::Int1Ty, VT->getNumElements());
else
ResultTy = Type::Int1Ty;
// Fold FCMP_FALSE/FCMP_TRUE unconditionally.
if (pred == FCmpInst::FCMP_FALSE)
return Context.getNullValue(ResultTy);
if (pred == FCmpInst::FCMP_TRUE)
return Context.getAllOnesValue(ResultTy);
// Handle some degenerate cases first
if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
return Context.getUndef(ResultTy);
// No compile-time operations on this type yet.
if (C1->getType() == Type::PPC_FP128Ty)
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 Context.getConstantIntFalse();
else if (pred == ICmpInst::ICMP_NE)
return Context.getConstantIntTrue();
}
// 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 Context.getConstantIntFalse();
else if (pred == ICmpInst::ICMP_NE)
return Context.getConstantIntTrue();
}
}
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 Context.getConstantInt(Type::Int1Ty, V1 == V2);
case ICmpInst::ICMP_NE:
return Context.getConstantInt(Type::Int1Ty, V1 != V2);
case ICmpInst::ICMP_SLT:
return Context.getConstantInt(Type::Int1Ty, V1.slt(V2));
case ICmpInst::ICMP_SGT:
return Context.getConstantInt(Type::Int1Ty, V1.sgt(V2));
case ICmpInst::ICMP_SLE:
return Context.getConstantInt(Type::Int1Ty, V1.sle(V2));
case ICmpInst::ICMP_SGE:
return Context.getConstantInt(Type::Int1Ty, V1.sge(V2));
case ICmpInst::ICMP_ULT:
return Context.getConstantInt(Type::Int1Ty, V1.ult(V2));
case ICmpInst::ICMP_UGT:
return Context.getConstantInt(Type::Int1Ty, V1.ugt(V2));
case ICmpInst::ICMP_ULE:
return Context.getConstantInt(Type::Int1Ty, V1.ule(V2));
case ICmpInst::ICMP_UGE:
return Context.getConstantInt(Type::Int1Ty, 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 Context.getConstantIntFalse();
case FCmpInst::FCMP_TRUE: return Context.getConstantIntTrue();
case FCmpInst::FCMP_UNO:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpUnordered);
case FCmpInst::FCMP_ORD:
return Context.getConstantInt(Type::Int1Ty, R!=APFloat::cmpUnordered);
case FCmpInst::FCMP_UEQ:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpUnordered ||
R==APFloat::cmpEqual);
case FCmpInst::FCMP_OEQ:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpEqual);
case FCmpInst::FCMP_UNE:
return Context.getConstantInt(Type::Int1Ty, R!=APFloat::cmpEqual);
case FCmpInst::FCMP_ONE:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpLessThan ||
R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_ULT:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpUnordered ||
R==APFloat::cmpLessThan);
case FCmpInst::FCMP_OLT:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpLessThan);
case FCmpInst::FCMP_UGT:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpUnordered ||
R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_OGT:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpGreaterThan);
case FCmpInst::FCMP_ULE:
return Context.getConstantInt(Type::Int1Ty, R!=APFloat::cmpGreaterThan);
case FCmpInst::FCMP_OLE:
return Context.getConstantInt(Type::Int1Ty, R==APFloat::cmpLessThan ||
R==APFloat::cmpEqual);
case FCmpInst::FCMP_UGE:
return Context.getConstantInt(Type::Int1Ty, R!=APFloat::cmpLessThan);
case FCmpInst::FCMP_OGE:
return Context.getConstantInt(Type::Int1Ty, 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(
Context.getConstantExprCompare(pred, C1Elts[i], C2Elts[i]));
}
return Context.getConstantVector(&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 Context.getConstantInt(Type::Int1Ty, 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 = (pred == ICmpInst::ICMP_EQ ||
pred == ICmpInst::ICMP_ULE ||
pred == ICmpInst::ICMP_SLE ||
pred == ICmpInst::ICMP_UGE ||
pred == ICmpInst::ICMP_SGE);
break;
case ICmpInst::ICMP_ULT:
// If we know that C1 < C2, we can decide the result of this computation
// precisely.
Result = (pred == ICmpInst::ICMP_ULT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_ULE);
break;
case ICmpInst::ICMP_SLT:
// If we know that C1 < C2, we can decide the result of this computation
// precisely.
Result = (pred == ICmpInst::ICMP_SLT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_SLE);
break;
case ICmpInst::ICMP_UGT:
// If we know that C1 > C2, we can decide the result of this computation
// precisely.
Result = (pred == ICmpInst::ICMP_UGT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_UGE);
break;
case ICmpInst::ICMP_SGT:
// If we know that C1 > C2, we can decide the result of this computation
// precisely.
Result = (pred == ICmpInst::ICMP_SGT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_SGE);
break;
case ICmpInst::ICMP_ULE:
// If we know that C1 <= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_UGT) Result = 0;
if (pred == ICmpInst::ICMP_ULT) Result = 1;
break;
case ICmpInst::ICMP_SLE:
// If we know that C1 <= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_SGT) Result = 0;
if (pred == ICmpInst::ICMP_SLT) Result = 1;
break;
case ICmpInst::ICMP_UGE:
// If we know that C1 >= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_ULT) Result = 0;
if (pred == ICmpInst::ICMP_UGT) Result = 1;
break;
case ICmpInst::ICMP_SGE:
// If we know that C1 >= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_SLT) Result = 0;
if (pred == ICmpInst::ICMP_SGT) Result = 1;
break;
case ICmpInst::ICMP_NE:
// If we know that C1 != C2, we can only partially decide this relation.
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 Context.getConstantInt(Type::Int1Ty, Result);
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;
}
Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
const Constant *C,
Constant* const *Idxs,
unsigned NumIdx) {
if (NumIdx == 0 ||
(NumIdx == 1 && Idxs[0]->isNullValue()))
return const_cast<Constant*>(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 Context.getUndef(Context.getPointerType(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 Context.getConstantPointerNull(
Context.getPointerType(Ty,Ptr->getAddressSpace()));
}
}
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(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 =
Context.getConstantExprSExtOrBitCast(Idx0, Type::Int64Ty);
Constant *C2 = Context.getConstantExprSExtOrBitCast(Combined,
Type::Int64Ty);
Combined = Context.getConstantExpr(Instruction::Add, C1, C2);
} else {
Combined =
Context.getConstantExpr(Instruction::Add, Idx0, Combined);
}
}
NewIndices.push_back(Combined);
NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx);
return Context.getConstantExprGetElementPtr(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 Context.getConstantExprGetElementPtr(
(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::Int8Ty) {
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 = Context.getConstantExprSExt(Offset, Base->getType());
else if (Base->getType()->getPrimitiveSizeInBits() <
Offset->getType()->getPrimitiveSizeInBits())
Base = Context.getConstantExprZExt(Base, Offset->getType());
Base = Context.getConstantExprAdd(Base, Offset);
return Context.getConstantExprIntToPtr(Base, CE->getType());
}
}
return 0;
}
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