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llvm-6502/lib/VMCore/ConstantFold.cpp
Reid Spencer 4ada00d166 Add a comment to explain a folding transform. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35360 91177308-0d34-0410-b5e6-96231b3b80d8
2007-03-26 20:09:02 +00:00

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//===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and 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/ADT/SmallVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
#include <limits>
using namespace llvm;
//===----------------------------------------------------------------------===//
// ConstantFold*Instruction Implementations
//===----------------------------------------------------------------------===//
/// CastConstantVector - Convert the specified ConstantVector node to the
/// specified vector type. At this point, we know that the elements of the
/// input packed constant are all simple integer or FP values.
static Constant *CastConstantVector(ConstantVector *CV,
const VectorType *DstTy) {
unsigned SrcNumElts = CV->getType()->getNumElements();
unsigned DstNumElts = DstTy->getNumElements();
const Type *SrcEltTy = CV->getType()->getElementType();
const Type *DstEltTy = DstTy->getElementType();
// If both vectors have the same number of elements (thus, the elements
// are the same size), perform the conversion now.
if (SrcNumElts == DstNumElts) {
std::vector<Constant*> Result;
// If the src and dest elements are both integers, or both floats, we can
// just BitCast each element because the elements are the same size.
if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) ||
(SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) {
for (unsigned i = 0; i != SrcNumElts; ++i)
Result.push_back(
ConstantExpr::getBitCast(CV->getOperand(i), DstEltTy));
return ConstantVector::get(Result);
}
// If this is an int-to-fp cast ..
if (SrcEltTy->isInteger()) {
// Ensure that it is int-to-fp cast
assert(DstEltTy->isFloatingPoint());
if (DstEltTy->getTypeID() == Type::DoubleTyID) {
for (unsigned i = 0; i != SrcNumElts; ++i) {
ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
double V = CI->getValue().bitsToDouble();
Result.push_back(ConstantFP::get(Type::DoubleTy, V));
}
return ConstantVector::get(Result);
}
assert(DstEltTy == Type::FloatTy && "Unknown fp type!");
for (unsigned i = 0; i != SrcNumElts; ++i) {
ConstantInt *CI = cast<ConstantInt>(CV->getOperand(i));
float V = CI->getValue().bitsToFloat();
Result.push_back(ConstantFP::get(Type::FloatTy, V));
}
return ConstantVector::get(Result);
}
// Otherwise, this is an fp-to-int cast.
assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger());
if (SrcEltTy->getTypeID() == Type::DoubleTyID) {
for (unsigned i = 0; i != SrcNumElts; ++i) {
uint64_t V =
DoubleToBits(cast<ConstantFP>(CV->getOperand(i))->getValue());
Constant *C = ConstantInt::get(Type::Int64Ty, V);
Result.push_back(ConstantExpr::getBitCast(C, DstEltTy ));
}
return ConstantVector::get(Result);
}
assert(SrcEltTy->getTypeID() == Type::FloatTyID);
for (unsigned i = 0; i != SrcNumElts; ++i) {
uint32_t V = FloatToBits(cast<ConstantFP>(CV->getOperand(i))->getValue());
Constant *C = ConstantInt::get(Type::Int32Ty, V);
Result.push_back(ConstantExpr::getBitCast(C, DstEltTy));
}
return ConstantVector::get(Result);
}
// Otherwise, this is a cast that changes element count and size. Handle
// casts which shrink the elements here.
// FIXME: We need to know endianness to do this!
return 0;
}
/// 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.
/// @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);
}
Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
const Type *DestTy) {
const Type *SrcTy = V->getType();
if (isa<UndefValue>(V))
return UndefValue::get(DestTy);
// 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 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);
}
}
// 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))
return ConstantFP::get(DestTy, FPC->getValue());
return 0; // Can't fold.
case Instruction::FPToUI:
if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
return ConstantInt::get(Val);
}
return 0; // Can't fold.
case Instruction::FPToSI:
if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
APInt Val(APIntOps::RoundDoubleToAPInt(FPC->getValue(), DestBitWidth));
return ConstantInt::get(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:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
return ConstantFP::get(DestTy, CI->getValue().roundToDouble());
return 0;
case Instruction::SIToFP:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V))
return ConstantFP::get(DestTy, CI->getValue().signedRoundToDouble());
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 ConstantInt::get(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 ConstantInt::get(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 ConstantInt::get(Result);
}
return 0;
case Instruction::BitCast:
if (SrcTy == DestTy)
return (Constant*)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)) {
SmallVector<Value*, 8> IdxList;
IdxList.push_back(Constant::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(Constant::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 ConstantExpr::getGetElementPtr(
const_cast<Constant*>(V), &IdxList[0], IdxList.size());
}
// Handle casts from one packed 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!");
// First, check for null and undef
if (isa<ConstantAggregateZero>(V))
return Constant::getNullValue(DestTy);
if (isa<UndefValue>(V))
return UndefValue::get(DestTy);
if (const ConstantVector *CV = dyn_cast<ConstantVector>(V)) {
// This is a cast from a ConstantVector of one type to a
// ConstantVector of another type. Check to see if all elements of
// the input are simple.
bool AllSimpleConstants = true;
for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
if (!isa<ConstantInt>(CV->getOperand(i)) &&
!isa<ConstantFP>(CV->getOperand(i))) {
AllSimpleConstants = false;
break;
}
}
// If all of the elements are simple constants, we can fold this.
if (AllSimpleConstants)
return CastConstantVector(const_cast<ConstantVector*>(CV), 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 (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 const_cast<Constant*>(V);
if (DestTy->isFloatingPoint()) {
if (DestTy == Type::FloatTy)
return ConstantFP::get(DestTy, CI->getValue().bitsToFloat());
assert(DestTy == Type::DoubleTy && "Unknown FP type!");
return ConstantFP::get(DestTy, CI->getValue().bitsToDouble());
}
// Otherwise, can't fold this (packed?)
return 0;
}
// Handle ConstantFP input.
if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
// FP -> Integral.
if (DestTy == Type::Int32Ty) {
APInt Val(32, 0);
return ConstantInt::get(Val.floatToBits(FP->getValue()));
} else {
assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!");
APInt Val(64, 0);
return ConstantInt::get(Val.doubleToBits(FP->getValue()));
}
}
return 0;
default:
assert(!"Invalid CE CastInst opcode");
break;
}
assert(0 && "Failed to cast constant expression");
return 0;
}
Constant *llvm::ConstantFoldSelectInstruction(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(const Constant *Val,
const 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 (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {
return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue()));
} else if (isa<UndefValue>(Idx)) {
// ee({w,x,y,z}, undef) -> w (an arbitrary value).
return const_cast<Constant*>(CVal->getOperand(0));
}
}
return 0;
}
Constant *llvm::ConstantFoldInsertElementInstruction(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 packed 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 : UndefValue::get(Elt->getType());
Ops.push_back(const_cast<Constant*>(Op));
}
return ConstantVector::get(Ops);
}
if (isa<ConstantAggregateZero>(Val)) {
// Insertion of scalar constant into packed 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 : Constant::getNullValue(Elt->getType());
Ops.push_back(const_cast<Constant*>(Op));
}
return ConstantVector::get(Ops);
}
if (const ConstantVector *CVal = dyn_cast<ConstantVector>(Val)) {
// Insertion of scalar constant into packed 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 ConstantVector::get(Ops);
}
return 0;
}
Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1,
const Constant *V2,
const Constant *Mask) {
// TODO:
return 0;
}
/// EvalVectorOp - Given two packed constants and a function pointer, apply the
/// function pointer to each element pair, producing a new ConstantVector
/// constant.
static Constant *EvalVectorOp(const ConstantVector *V1,
const ConstantVector *V2,
Constant *(*FP)(Constant*, Constant*)) {
std::vector<Constant*> Res;
for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i)
Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)),
const_cast<Constant*>(V2->getOperand(i))));
return ConstantVector::get(Res);
}
Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
const Constant *C1,
const Constant *C2) {
// Handle UndefValue up front
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
switch (Opcode) {
case Instruction::Add:
case Instruction::Sub:
case Instruction::Xor:
return UndefValue::get(C1->getType());
case Instruction::Mul:
case Instruction::And:
return Constant::getNullValue(C1->getType());
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::FDiv:
case Instruction::URem:
case Instruction::SRem:
case Instruction::FRem:
if (!isa<UndefValue>(C2)) // undef / X -> 0
return Constant::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 ConstantVector::getAllOnesValue(PTy);
return ConstantInt::getAllOnesValue(C1->getType());
case Instruction::LShr:
if (isa<UndefValue>(C2) && isa<UndefValue>(C1))
return const_cast<Constant*>(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 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 Constant::getNullValue(C1->getType());
}
}
if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
if (isa<ConstantExpr>(C2)) {
// 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 {
// Just implement a couple of simple identities.
switch (Opcode) {
case Instruction::Add:
if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X
break;
case Instruction::Sub:
if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X
break;
case Instruction::Mul:
if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->equalsInt(1))
return const_cast<Constant*>(C1); // X * 1 == X
break;
case Instruction::UDiv:
case Instruction::SDiv:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->equalsInt(1))
return const_cast<Constant*>(C1); // X / 1 == X
break;
case Instruction::URem:
case Instruction::SRem:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->equalsInt(1))
return Constant::getNullValue(CI->getType()); // X % 1 == 0
break;
case Instruction::And:
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) {
if (CI->isZero()) return const_cast<Constant*>(C2); // X & 0 == 0
if (CI->isAllOnesValue())
return const_cast<Constant*>(C1); // X & -1 == X
// (zext i32 to i64) & 4294967295 -> (zext i32 to i64)
if (CE1->getOpcode() == Instruction::ZExt) {
APInt PossiblySetBits
= cast<IntegerType>(CE1->getOperand(0)->getType())->getMask();
PossiblySetBits.zext(C1->getType()->getPrimitiveSizeInBits());
if ((PossiblySetBits & CI->getValue()) == PossiblySetBits)
return const_cast<Constant*>(C1);
}
}
if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) {
GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0));
// Functions are at least 4-byte aligned. If and'ing the address of a
// function with a constant < 4, fold it to zero.
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->getValue().ult(APInt(CI->getType()->getBitWidth(),4)) &&
isa<Function>(CPR))
return Constant::getNullValue(CI->getType());
}
break;
case Instruction::Or:
if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X
if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2))
if (CI->isAllOnesValue())
return const_cast<Constant*>(C2); // X | -1 == -1
break;
case Instruction::Xor:
if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X
break;
case Instruction::AShr:
// ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2
if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero.
return ConstantExpr::getLShr(const_cast<Constant*>(C1),
const_cast<Constant*>(C2));
break;
}
}
} 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::Mul:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor:
// No change of opcode required.
return ConstantFoldBinaryInstruction(Opcode, C2, C1);
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Sub:
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.
return 0;
}
}
// At this point we know neither constant is an UndefValue nor a ConstantExpr
// so look at directly computing the value.
if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
using namespace APIntOps;
APInt C1V = CI1->getValue();
APInt C2V = CI2->getValue();
switch (Opcode) {
default:
break;
case Instruction::Add:
return ConstantInt::get(C1V + C2V);
case Instruction::Sub:
return ConstantInt::get(C1V - C2V);
case Instruction::Mul:
return ConstantInt::get(C1V * C2V);
case Instruction::UDiv:
if (CI2->isNullValue())
return 0; // X / 0 -> can't fold
return ConstantInt::get(C1V.udiv(C2V));
case Instruction::SDiv:
if (CI2->isNullValue())
return 0; // X / 0 -> can't fold
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return 0; // MIN_INT / -1 -> overflow
return ConstantInt::get(C1V.sdiv(C2V));
case Instruction::URem:
if (C2->isNullValue())
return 0; // X / 0 -> can't fold
return ConstantInt::get(C1V.urem(C2V));
case Instruction::SRem:
if (CI2->isNullValue())
return 0; // X % 0 -> can't fold
if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
return 0; // MIN_INT % -1 -> overflow
return ConstantInt::get(C1V.srem(C2V));
case Instruction::And:
return ConstantInt::get(C1V & C2V);
case Instruction::Or:
return ConstantInt::get(C1V | C2V);
case Instruction::Xor:
return ConstantInt::get(C1V ^ C2V);
case Instruction::Shl:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1V.shl(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
return const_cast<ConstantInt*>(CI1); // Zero shift is identity
case Instruction::LShr:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1V.lshr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
return const_cast<ConstantInt*>(CI1); // Zero shift is identity
case Instruction::AShr:
if (uint32_t shiftAmt = C2V.getZExtValue())
if (shiftAmt < C1V.getBitWidth())
return ConstantInt::get(C1V.ashr(shiftAmt));
else
return UndefValue::get(C1->getType()); // too big shift is undef
return const_cast<ConstantInt*>(CI1); // Zero shift is identity
}
}
} else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
double C1Val = CFP1->getValue();
double C2Val = CFP2->getValue();
switch (Opcode) {
default:
break;
case Instruction::Add:
return ConstantFP::get(CFP1->getType(), C1Val + C2Val);
case Instruction::Sub:
return ConstantFP::get(CFP1->getType(), C1Val - C2Val);
case Instruction::Mul:
return ConstantFP::get(CFP1->getType(), C1Val * C2Val);
case Instruction::FDiv:
if (CFP2->isExactlyValue(0.0) || CFP2->isExactlyValue(-0.0))
if (CFP1->isExactlyValue(0.0) || CFP1->isExactlyValue(-0.0))
// IEEE 754, Section 7.1, #4
return ConstantFP::get(CFP1->getType(),
std::numeric_limits<double>::quiet_NaN());
else if (CFP2->isExactlyValue(-0.0) || C1Val < 0.0)
// IEEE 754, Section 7.2, negative infinity case
return ConstantFP::get(CFP1->getType(),
-std::numeric_limits<double>::infinity());
else
// IEEE 754, Section 7.2, positive infinity case
return ConstantFP::get(CFP1->getType(),
std::numeric_limits<double>::infinity());
return ConstantFP::get(CFP1->getType(), C1Val / C2Val);
case Instruction::FRem:
if (CFP2->isExactlyValue(0.0) || CFP2->isExactlyValue(-0.0))
// IEEE 754, Section 7.1, #5
return ConstantFP::get(CFP1->getType(),
std::numeric_limits<double>::quiet_NaN());
return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val));
}
}
} else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
switch (Opcode) {
default:
break;
case Instruction::Add:
return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd);
case Instruction::Sub:
return EvalVectorOp(CP1, CP2, ConstantExpr::getSub);
case Instruction::Mul:
return EvalVectorOp(CP1, CP2, ConstantExpr::getMul);
case Instruction::UDiv:
return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv);
case Instruction::SDiv:
return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv);
case Instruction::FDiv:
return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv);
case Instruction::URem:
return EvalVectorOp(CP1, CP2, ConstantExpr::getURem);
case Instruction::SRem:
return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem);
case Instruction::FRem:
return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem);
case Instruction::And:
return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd);
case Instruction::Or:
return EvalVectorOp(CP1, CP2, ConstantExpr::getOr);
case Instruction::Xor:
return EvalVectorOp(CP1, CP2, ConstantExpr::getXor);
}
}
}
// 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(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 = ConstantExpr::getSExt(C1, Type::Int64Ty);
if (C2->getType() != Type::Int64Ty)
C2 = ConstantExpr::getSExt(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(const Constant *V1,
const Constant *V2) {
assert(V1->getType() == V2->getType() &&
"Cannot compare values of different types!");
// 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>(
ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2));
if (R && !R->isZero())
return FCmpInst::FCMP_OEQ;
R = dyn_cast<ConstantInt>(
ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2));
if (R && !R->isZero())
return FCmpInst::FCMP_OLT;
R = dyn_cast<ConstantInt>(
ConstantExpr::getFCmp(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(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(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>(ConstantExpr::getICmp(pred, C1, C2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT;
R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2));
if (R && !R->isZero())
return pred;
pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT;
R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(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(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(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)) {
if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage())
return ICmpInst::ICMP_NE;
} else {
// GlobalVals can never be null.
assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!");
if (!CPR1->hasExternalWeakLinkage())
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::IntToPtr:
case Instruction::BitCast:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::PtrToInt:
// 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 = CE1->getOpcode() == Instruction::ZExt ? false :
(CE1->getOpcode() == Instruction::SExt ? true :
(CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
return evaluateICmpRelation(
CE1Op0, Constant::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 = CE1->getOpcode() == Instruction::ZExt ? false :
(CE1->getOpcode() == Instruction::SExt ? true :
(CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned));
return evaluateICmpRelation(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(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(unsigned short pred,
const Constant *C1,
const Constant *C2) {
// Handle some degenerate cases first
if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
return UndefValue::get(Type::Int1Ty);
// icmp eq/ne(null,GV) -> false/true
if (C1->isNullValue()) {
if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2))
if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
if (pred == ICmpInst::ICMP_EQ)
return ConstantInt::getFalse();
else if (pred == ICmpInst::ICMP_NE)
return ConstantInt::getTrue();
// icmp eq/ne(GV,null) -> false/true
} else if (C2->isNullValue()) {
if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1))
if (!GV->hasExternalWeakLinkage()) // External weak GV can be null
if (pred == ICmpInst::ICMP_EQ)
return ConstantInt::getFalse();
else if (pred == ICmpInst::ICMP_NE)
return ConstantInt::getTrue();
}
if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
APInt V1 = cast<ConstantInt>(C1)->getValue();
APInt V2 = cast<ConstantInt>(C2)->getValue();
switch (pred) {
default: assert(0 && "Invalid ICmp Predicate"); return 0;
case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2);
case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2);
case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1.slt(V2));
case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1.sgt(V2));
case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1.sle(V2));
case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1.sge(V2));
case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1.ult(V2));
case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1.ugt(V2));
case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1.ule(V2));
case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1.uge(V2));
}
} else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
double C1Val = cast<ConstantFP>(C1)->getValue();
double C2Val = cast<ConstantFP>(C2)->getValue();
switch (pred) {
default: assert(0 && "Invalid FCmp Predicate"); return 0;
case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse();
case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue();
case FCmpInst::FCMP_UNO:
return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val);
case FCmpInst::FCMP_ORD:
return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val);
case FCmpInst::FCMP_UEQ:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_OEQ:
return ConstantInt::get(Type::Int1Ty, C1Val == C2Val);
case FCmpInst::FCMP_UNE:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_ONE:
return ConstantInt::get(Type::Int1Ty, C1Val != C2Val);
case FCmpInst::FCMP_ULT:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_OLT:
return ConstantInt::get(Type::Int1Ty, C1Val < C2Val);
case FCmpInst::FCMP_UGT:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_OGT:
return ConstantInt::get(Type::Int1Ty, C1Val > C2Val);
case FCmpInst::FCMP_ULE:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_OLE:
return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val);
case FCmpInst::FCMP_UGE:
if (C1Val != C1Val || C2Val != C2Val)
return ConstantInt::getTrue();
/* FALL THROUGH */
case FCmpInst::FCMP_OGE:
return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val);
}
} else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) {
if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) {
if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) {
for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ,
const_cast<Constant*>(CP1->getOperand(i)),
const_cast<Constant*>(CP2->getOperand(i)));
if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
return CB;
}
// Otherwise, could not decide from any element pairs.
return 0;
} else if (pred == ICmpInst::ICMP_EQ) {
for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) {
Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ,
const_cast<Constant*>(CP1->getOperand(i)),
const_cast<Constant*>(CP2->getOperand(i)));
if (ConstantInt *CB = dyn_cast<ConstantInt>(C))
return CB;
}
// Otherwise, could not decide from any element pairs.
return 0;
}
}
}
if (C1->getType()->isFloatingPoint()) {
switch (evaluateFCmpRelation(C1, C2)) {
default: assert(0 && "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
return ConstantInt::get(Type::Int1Ty,
pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ ||
pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE ||
pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
case FCmpInst::FCMP_OLT: // We know that C1 < C2
return ConstantInt::get(Type::Int1Ty,
pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT ||
pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE);
case FCmpInst::FCMP_OGT: // We know that C1 > C2
return ConstantInt::get(Type::Int1Ty,
pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE ||
pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT ||
pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE);
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)
return ConstantInt::getFalse();
if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT)
return ConstantInt::getTrue();
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)
return ConstantInt::getFalse();
if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT)
return ConstantInt::getTrue();
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)
return ConstantInt::getFalse();
if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE)
return ConstantInt::getTrue();
break;
}
} else {
// Evaluate the relation between the two constants, per the predicate.
switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) {
default: assert(0 && "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.
return ConstantInt::get(Type::Int1Ty,
pred == ICmpInst::ICMP_EQ ||
pred == ICmpInst::ICMP_ULE ||
pred == ICmpInst::ICMP_SLE ||
pred == ICmpInst::ICMP_UGE ||
pred == ICmpInst::ICMP_SGE);
case ICmpInst::ICMP_ULT:
// If we know that C1 < C2, we can decide the result of this computation
// precisely.
return ConstantInt::get(Type::Int1Ty,
pred == ICmpInst::ICMP_ULT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_ULE);
case ICmpInst::ICMP_SLT:
// If we know that C1 < C2, we can decide the result of this computation
// precisely.
return ConstantInt::get(Type::Int1Ty,
pred == ICmpInst::ICMP_SLT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_SLE);
case ICmpInst::ICMP_UGT:
// If we know that C1 > C2, we can decide the result of this computation
// precisely.
return ConstantInt::get(Type::Int1Ty,
pred == ICmpInst::ICMP_UGT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_UGE);
case ICmpInst::ICMP_SGT:
// If we know that C1 > C2, we can decide the result of this computation
// precisely.
return ConstantInt::get(Type::Int1Ty,
pred == ICmpInst::ICMP_SGT ||
pred == ICmpInst::ICMP_NE ||
pred == ICmpInst::ICMP_SGE);
case ICmpInst::ICMP_ULE:
// If we know that C1 <= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse();
if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue();
break;
case ICmpInst::ICMP_SLE:
// If we know that C1 <= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse();
if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue();
break;
case ICmpInst::ICMP_UGE:
// If we know that C1 >= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse();
if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue();
break;
case ICmpInst::ICMP_SGE:
// If we know that C1 >= C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse();
if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue();
break;
case ICmpInst::ICMP_NE:
// If we know that C1 != C2, we can only partially decide this relation.
if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse();
if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue();
break;
}
if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
// If C2 is a constant expr and C1 isn't, flop 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(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(pred, C2, C1);
default: // These predicates cannot be flopped around.
break;
}
}
}
return 0;
}
Constant *llvm::ConstantFoldGetElementPtr(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 Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
(Value**)Idxs, NumIdx,
true);
assert(Ty != 0 && "Invalid indices for GEP!");
return UndefValue::get(PointerType::get(Ty));
}
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 Type *Ty = GetElementPtrInst::getIndexedType(C->getType(),
(Value**)Idxs, NumIdx,
true);
assert(Ty != 0 && "Invalid indices for GEP!");
return ConstantPointerNull::get(PointerType::get(Ty));
}
}
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 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty);
Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined,
Type::Int64Ty);
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 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 ConstantExpr::getGetElementPtr(
(Constant*)CE->getOperand(0), Idxs, NumIdx);
}
return 0;
}
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