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b8f1c1657f
llvm/lib/VMCore/ConstantFold.cpp
Reid Spencer b8f1c1657f Fix constant fold of div by zero and rem by zero to match IEEE 754 
requirements. We must return NaN in some cases and correctly signed
infinity in other cases. Passes CFP2006 (not that that says much).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35277 91177308-0d34-0410-b5e6-96231b3b80d8
2007-03-23 05:33:23 +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->isAllOnesValue())
return const_cast<Constant*>(C1); // X & -1 == X
if (C2->isNullValue()) return const_cast<Constant*>(C2); // X & 0 == 0
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;
}
}
} 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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