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llvm-project/llvm/lib/Analysis/ConstantFolding.cpp

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//===-- ConstantFolding.cpp - Fold instructions into constants ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines routines for folding instructions into constants.
//
// Also, to supplement the basic IR ConstantExpr simplifications,
// this file defines some additional folding routines that can make use of
// DataLayout information. These functions cannot go in IR due to library
// dependency issues.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Config/config.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include <cerrno>
#include <cmath>
#ifdef HAVE_FENV_H
#include <fenv.h>
#endif
using namespace llvm;
//===----------------------------------------------------------------------===//
// Constant Folding internal helper functions
//===----------------------------------------------------------------------===//
/// Constant fold bitcast, symbolically evaluating it with DataLayout.
/// This always returns a non-null constant, but it may be a
/// ConstantExpr if unfoldable.
static Constant *FoldBitCast(Constant *C, Type *DestTy,
const DataLayout &TD) {
// Catch the obvious splat cases.
if (C->isNullValue() && !DestTy->isX86_MMXTy())
return Constant::getNullValue(DestTy);
if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() &&
!DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types!
return Constant::getAllOnesValue(DestTy);
// Handle a vector->integer cast.
if (IntegerType *IT = dyn_cast<IntegerType>(DestTy)) {
VectorType *VTy = dyn_cast<VectorType>(C->getType());
if (!VTy)
return ConstantExpr::getBitCast(C, DestTy);
unsigned NumSrcElts = VTy->getNumElements();
Type *SrcEltTy = VTy->getElementType();
// If the vector is a vector of floating point, convert it to vector of int
// to simplify things.
if (SrcEltTy->isFloatingPointTy()) {
unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
Type *SrcIVTy =
VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElts);
// Ask IR to do the conversion now that #elts line up.
C = ConstantExpr::getBitCast(C, SrcIVTy);
}
ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(C);
if (!CDV)
return ConstantExpr::getBitCast(C, DestTy);
// Now that we know that the input value is a vector of integers, just shift
// and insert them into our result.
unsigned BitShift = TD.getTypeAllocSizeInBits(SrcEltTy);
APInt Result(IT->getBitWidth(), 0);
for (unsigned i = 0; i != NumSrcElts; ++i) {
Result <<= BitShift;
if (TD.isLittleEndian())
Result |= CDV->getElementAsInteger(NumSrcElts-i-1);
else
Result |= CDV->getElementAsInteger(i);
}
return ConstantInt::get(IT, Result);
}
// The code below only handles casts to vectors currently.
VectorType *DestVTy = dyn_cast<VectorType>(DestTy);
if (!DestVTy)
return ConstantExpr::getBitCast(C, DestTy);
// If this is a scalar -> vector cast, convert the input into a <1 x scalar>
// vector so the code below can handle it uniformly.
if (isa<ConstantFP>(C) || isa<ConstantInt>(C)) {
Constant *Ops = C; // don't take the address of C!
return FoldBitCast(ConstantVector::get(Ops), DestTy, TD);
}
// If this is a bitcast from constant vector -> vector, fold it.
if (!isa<ConstantDataVector>(C) && !isa<ConstantVector>(C))
return ConstantExpr::getBitCast(C, DestTy);
// If the element types match, IR can fold it.
unsigned NumDstElt = DestVTy->getNumElements();
unsigned NumSrcElt = C->getType()->getVectorNumElements();
if (NumDstElt == NumSrcElt)
return ConstantExpr::getBitCast(C, DestTy);
Type *SrcEltTy = C->getType()->getVectorElementType();
Type *DstEltTy = DestVTy->getElementType();
// Otherwise, we're changing the number of elements in a vector, which
// requires endianness information to do the right thing. For example,
// bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
// folds to (little endian):
// <4 x i32> <i32 0, i32 0, i32 1, i32 0>
// and to (big endian):
// <4 x i32> <i32 0, i32 0, i32 0, i32 1>
// First thing is first. We only want to think about integer here, so if
// we have something in FP form, recast it as integer.
if (DstEltTy->isFloatingPointTy()) {
// Fold to an vector of integers with same size as our FP type.
unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
Type *DestIVTy =
VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumDstElt);
// Recursively handle this integer conversion, if possible.
C = FoldBitCast(C, DestIVTy, TD);
// Finally, IR can handle this now that #elts line up.
return ConstantExpr::getBitCast(C, DestTy);
}
// Okay, we know the destination is integer, if the input is FP, convert
// it to integer first.
if (SrcEltTy->isFloatingPointTy()) {
unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
Type *SrcIVTy =
VectorType::get(IntegerType::get(C->getContext(), FPWidth), NumSrcElt);
// Ask IR to do the conversion now that #elts line up.
C = ConstantExpr::getBitCast(C, SrcIVTy);
// If IR wasn't able to fold it, bail out.
if (!isa<ConstantVector>(C) && // FIXME: Remove ConstantVector.
!isa<ConstantDataVector>(C))
return C;
}
// Now we know that the input and output vectors are both integer vectors
// of the same size, and that their #elements is not the same. Do the
// conversion here, which depends on whether the input or output has
// more elements.
bool isLittleEndian = TD.isLittleEndian();
SmallVector<Constant*, 32> Result;
if (NumDstElt < NumSrcElt) {
// Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
Constant *Zero = Constant::getNullValue(DstEltTy);
unsigned Ratio = NumSrcElt/NumDstElt;
unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
unsigned SrcElt = 0;
for (unsigned i = 0; i != NumDstElt; ++i) {
// Build each element of the result.
Constant *Elt = Zero;
unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
for (unsigned j = 0; j != Ratio; ++j) {
Constant *Src =dyn_cast<ConstantInt>(C->getAggregateElement(SrcElt++));
if (!Src) // Reject constantexpr elements.
return ConstantExpr::getBitCast(C, DestTy);
// Zero extend the element to the right size.
Src = ConstantExpr::getZExt(Src, Elt->getType());
// Shift it to the right place, depending on endianness.
Src = ConstantExpr::getShl(Src,
ConstantInt::get(Src->getType(), ShiftAmt));
ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
// Mix it in.
Elt = ConstantExpr::getOr(Elt, Src);
}
Result.push_back(Elt);
}
return ConstantVector::get(Result);
}
// Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
unsigned Ratio = NumDstElt/NumSrcElt;
unsigned DstBitSize = TD.getTypeSizeInBits(DstEltTy);
// Loop over each source value, expanding into multiple results.
for (unsigned i = 0; i != NumSrcElt; ++i) {
Constant *Src = dyn_cast<ConstantInt>(C->getAggregateElement(i));
if (!Src) // Reject constantexpr elements.
return ConstantExpr::getBitCast(C, DestTy);
unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
for (unsigned j = 0; j != Ratio; ++j) {
// Shift the piece of the value into the right place, depending on
// endianness.
Constant *Elt = ConstantExpr::getLShr(Src,
ConstantInt::get(Src->getType(), ShiftAmt));
ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
// Truncate the element to an integer with the same pointer size and
// convert the element back to a pointer using a inttoptr.
if (DstEltTy->isPointerTy()) {
IntegerType *DstIntTy = Type::getIntNTy(C->getContext(), DstBitSize);
Constant *CE = ConstantExpr::getTrunc(Elt, DstIntTy);
Result.push_back(ConstantExpr::getIntToPtr(CE, DstEltTy));
continue;
}
// Truncate and remember this piece.
Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
}
}
return ConstantVector::get(Result);
}
/// If this constant is a constant offset from a global, return the global and
/// the constant. Because of constantexprs, this function is recursive.
static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
APInt &Offset, const DataLayout &TD) {
// Trivial case, constant is the global.
if ((GV = dyn_cast<GlobalValue>(C))) {
unsigned BitWidth = TD.getPointerTypeSizeInBits(GV->getType());
Offset = APInt(BitWidth, 0);
return true;
}
// Otherwise, if this isn't a constant expr, bail out.
ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
if (!CE) return false;
// Look through ptr->int and ptr->ptr casts.
if (CE->getOpcode() == Instruction::PtrToInt ||
CE->getOpcode() == Instruction::BitCast ||
CE->getOpcode() == Instruction::AddrSpaceCast)
return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
// i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
GEPOperator *GEP = dyn_cast<GEPOperator>(CE);
if (!GEP)
return false;
unsigned BitWidth = TD.getPointerTypeSizeInBits(GEP->getType());
APInt TmpOffset(BitWidth, 0);
// If the base isn't a global+constant, we aren't either.
if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, TmpOffset, TD))
return false;
// Otherwise, add any offset that our operands provide.
if (!GEP->accumulateConstantOffset(TD, TmpOffset))
return false;
Offset = TmpOffset;
return true;
}
/// Recursive helper to read bits out of global. C is the constant being copied
/// out of. ByteOffset is an offset into C. CurPtr is the pointer to copy
/// results into and BytesLeft is the number of bytes left in
/// the CurPtr buffer. TD is the target data.
static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
unsigned char *CurPtr, unsigned BytesLeft,
const DataLayout &TD) {
assert(ByteOffset <= TD.getTypeAllocSize(C->getType()) &&
"Out of range access");
// If this element is zero or undefined, we can just return since *CurPtr is
// zero initialized.
if (isa<ConstantAggregateZero>(C) || isa<UndefValue>(C))
return true;
if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
if (CI->getBitWidth() > 64 ||
(CI->getBitWidth() & 7) != 0)
return false;
uint64_t Val = CI->getZExtValue();
unsigned IntBytes = unsigned(CI->getBitWidth()/8);
for (unsigned i = 0; i != BytesLeft && ByteOffset != IntBytes; ++i) {
int n = ByteOffset;
if (!TD.isLittleEndian())
n = IntBytes - n - 1;
CurPtr[i] = (unsigned char)(Val >> (n * 8));
++ByteOffset;
}
return true;
}
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
if (CFP->getType()->isDoubleTy()) {
C = FoldBitCast(C, Type::getInt64Ty(C->getContext()), TD);
return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
}
if (CFP->getType()->isFloatTy()){
C = FoldBitCast(C, Type::getInt32Ty(C->getContext()), TD);
return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
}
if (CFP->getType()->isHalfTy()){
C = FoldBitCast(C, Type::getInt16Ty(C->getContext()), TD);
return ReadDataFromGlobal(C, ByteOffset, CurPtr, BytesLeft, TD);
}
return false;
}
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
const StructLayout *SL = TD.getStructLayout(CS->getType());
unsigned Index = SL->getElementContainingOffset(ByteOffset);
uint64_t CurEltOffset = SL->getElementOffset(Index);
ByteOffset -= CurEltOffset;
while (1) {
// If the element access is to the element itself and not to tail padding,
// read the bytes from the element.
uint64_t EltSize = TD.getTypeAllocSize(CS->getOperand(Index)->getType());
if (ByteOffset < EltSize &&
!ReadDataFromGlobal(CS->getOperand(Index), ByteOffset, CurPtr,
BytesLeft, TD))
return false;
++Index;
// Check to see if we read from the last struct element, if so we're done.
if (Index == CS->getType()->getNumElements())
return true;
// If we read all of the bytes we needed from this element we're done.
uint64_t NextEltOffset = SL->getElementOffset(Index);
if (BytesLeft <= NextEltOffset - CurEltOffset - ByteOffset)
return true;
// Move to the next element of the struct.
CurPtr += NextEltOffset - CurEltOffset - ByteOffset;
BytesLeft -= NextEltOffset - CurEltOffset - ByteOffset;
ByteOffset = 0;
CurEltOffset = NextEltOffset;
}
// not reached.
}
if (isa<ConstantArray>(C) || isa<ConstantVector>(C) ||
isa<ConstantDataSequential>(C)) {
Type *EltTy = C->getType()->getSequentialElementType();
uint64_t EltSize = TD.getTypeAllocSize(EltTy);
uint64_t Index = ByteOffset / EltSize;
uint64_t Offset = ByteOffset - Index * EltSize;
uint64_t NumElts;
if (ArrayType *AT = dyn_cast<ArrayType>(C->getType()))
NumElts = AT->getNumElements();
else
NumElts = C->getType()->getVectorNumElements();
for (; Index != NumElts; ++Index) {
if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr,
BytesLeft, TD))
return false;
uint64_t BytesWritten = EltSize - Offset;
assert(BytesWritten <= EltSize && "Not indexing into this element?");
if (BytesWritten >= BytesLeft)
return true;
Offset = 0;
BytesLeft -= BytesWritten;
CurPtr += BytesWritten;
}
return true;
}
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::IntToPtr &&
CE->getOperand(0)->getType() == TD.getIntPtrType(CE->getType())) {
return ReadDataFromGlobal(CE->getOperand(0), ByteOffset, CurPtr,
BytesLeft, TD);
}
}
// Otherwise, unknown initializer type.
return false;
}
static Constant *FoldReinterpretLoadFromConstPtr(Constant *C,
const DataLayout &TD) {
PointerType *PTy = cast<PointerType>(C->getType());
Type *LoadTy = PTy->getElementType();
IntegerType *IntType = dyn_cast<IntegerType>(LoadTy);
// If this isn't an integer load we can't fold it directly.
if (!IntType) {
unsigned AS = PTy->getAddressSpace();
// If this is a float/double load, we can try folding it as an int32/64 load
// and then bitcast the result. This can be useful for union cases. Note
// that address spaces don't matter here since we're not going to result in
// an actual new load.
Type *MapTy;
if (LoadTy->isHalfTy())
MapTy = Type::getInt16PtrTy(C->getContext(), AS);
else if (LoadTy->isFloatTy())
MapTy = Type::getInt32PtrTy(C->getContext(), AS);
else if (LoadTy->isDoubleTy())
MapTy = Type::getInt64PtrTy(C->getContext(), AS);
else if (LoadTy->isVectorTy()) {
MapTy = PointerType::getIntNPtrTy(C->getContext(),
TD.getTypeAllocSizeInBits(LoadTy),
AS);
} else
return nullptr;
C = FoldBitCast(C, MapTy, TD);
if (Constant *Res = FoldReinterpretLoadFromConstPtr(C, TD))
return FoldBitCast(Res, LoadTy, TD);
return nullptr;
}
unsigned BytesLoaded = (IntType->getBitWidth() + 7) / 8;
if (BytesLoaded > 32 || BytesLoaded == 0)
return nullptr;
GlobalValue *GVal;
APInt Offset;
if (!IsConstantOffsetFromGlobal(C, GVal, Offset, TD))
return nullptr;
GlobalVariable *GV = dyn_cast<GlobalVariable>(GVal);
if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
!GV->getInitializer()->getType()->isSized())
return nullptr;
// If we're loading off the beginning of the global, some bytes may be valid,
// but we don't try to handle this.
if (Offset.isNegative())
return nullptr;
// If we're not accessing anything in this constant, the result is undefined.
if (Offset.getZExtValue() >=
TD.getTypeAllocSize(GV->getInitializer()->getType()))
return UndefValue::get(IntType);
unsigned char RawBytes[32] = {0};
if (!ReadDataFromGlobal(GV->getInitializer(), Offset.getZExtValue(), RawBytes,
BytesLoaded, TD))
return nullptr;
APInt ResultVal = APInt(IntType->getBitWidth(), 0);
if (TD.isLittleEndian()) {
ResultVal = RawBytes[BytesLoaded - 1];
for (unsigned i = 1; i != BytesLoaded; ++i) {
ResultVal <<= 8;
ResultVal |= RawBytes[BytesLoaded - 1 - i];
}
} else {
ResultVal = RawBytes[0];
for (unsigned i = 1; i != BytesLoaded; ++i) {
ResultVal <<= 8;
ResultVal |= RawBytes[i];
}
}
return ConstantInt::get(IntType->getContext(), ResultVal);
}
static Constant *ConstantFoldLoadThroughBitcast(ConstantExpr *CE,
const DataLayout *DL) {
if (!DL)
return nullptr;
auto *DestPtrTy = dyn_cast<PointerType>(CE->getType());
if (!DestPtrTy)
return nullptr;
Type *DestTy = DestPtrTy->getElementType();
Constant *C = ConstantFoldLoadFromConstPtr(CE->getOperand(0), DL);
if (!C)
return nullptr;
do {
Type *SrcTy = C->getType();
// If the type sizes are the same and a cast is legal, just directly
// cast the constant.
if (DL->getTypeSizeInBits(DestTy) == DL->getTypeSizeInBits(SrcTy)) {
Instruction::CastOps Cast = Instruction::BitCast;
// If we are going from a pointer to int or vice versa, we spell the cast
// differently.
if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
Cast = Instruction::IntToPtr;
else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
Cast = Instruction::PtrToInt;
if (CastInst::castIsValid(Cast, C, DestTy))
return ConstantExpr::getCast(Cast, C, DestTy);
}
// If this isn't an aggregate type, there is nothing we can do to drill down
// and find a bitcastable constant.
if (!SrcTy->isAggregateType())
return nullptr;
// We're simulating a load through a pointer that was bitcast to point to
// a different type, so we can try to walk down through the initial
// elements of an aggregate to see if some part of th e aggregate is
// castable to implement the "load" semantic model.
C = C->getAggregateElement(0u);
} while (C);
return nullptr;
}
/// Return the value that a load from C would produce if it is constant and
/// determinable. If this is not determinable, return null.
Constant *llvm::ConstantFoldLoadFromConstPtr(Constant *C,
const DataLayout *TD) {
// First, try the easy cases:
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
return GV->getInitializer();
// If the loaded value isn't a constant expr, we can't handle it.
ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
if (!CE)
return nullptr;
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) {
if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return V;
}
}
}
if (CE->getOpcode() == Instruction::BitCast)
if (Constant *LoadedC = ConstantFoldLoadThroughBitcast(CE, TD))
return LoadedC;
// Instead of loading constant c string, use corresponding integer value
// directly if string length is small enough.
StringRef Str;
if (TD && getConstantStringInfo(CE, Str) && !Str.empty()) {
unsigned StrLen = Str.size();
Type *Ty = cast<PointerType>(CE->getType())->getElementType();
unsigned NumBits = Ty->getPrimitiveSizeInBits();
// Replace load with immediate integer if the result is an integer or fp
// value.
if ((NumBits >> 3) == StrLen + 1 && (NumBits & 7) == 0 &&
(isa<IntegerType>(Ty) || Ty->isFloatingPointTy())) {
APInt StrVal(NumBits, 0);
APInt SingleChar(NumBits, 0);
if (TD->isLittleEndian()) {
for (signed i = StrLen-1; i >= 0; i--) {
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
StrVal = (StrVal << 8) | SingleChar;
}
} else {
for (unsigned i = 0; i < StrLen; i++) {
SingleChar = (uint64_t) Str[i] & UCHAR_MAX;
StrVal = (StrVal << 8) | SingleChar;
}
// Append NULL at the end.
SingleChar = 0;
StrVal = (StrVal << 8) | SingleChar;
}
Constant *Res = ConstantInt::get(CE->getContext(), StrVal);
if (Ty->isFloatingPointTy())
Res = ConstantExpr::getBitCast(Res, Ty);
return Res;
}
}
// If this load comes from anywhere in a constant global, and if the global
// is all undef or zero, we know what it loads.
if (GlobalVariable *GV =
dyn_cast<GlobalVariable>(GetUnderlyingObject(CE, TD))) {
if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
Type *ResTy = cast<PointerType>(C->getType())->getElementType();
if (GV->getInitializer()->isNullValue())
return Constant::getNullValue(ResTy);
if (isa<UndefValue>(GV->getInitializer()))
return UndefValue::get(ResTy);
}
}
// Try hard to fold loads from bitcasted strange and non-type-safe things.
if (TD)
return FoldReinterpretLoadFromConstPtr(CE, *TD);
return nullptr;
}
static Constant *ConstantFoldLoadInst(const LoadInst *LI, const DataLayout *TD){
if (LI->isVolatile()) return nullptr;
if (Constant *C = dyn_cast<Constant>(LI->getOperand(0)))
return ConstantFoldLoadFromConstPtr(C, TD);
return nullptr;
}
/// One of Op0/Op1 is a constant expression.
/// Attempt to symbolically evaluate the result of a binary operator merging
/// these together. If target data info is available, it is provided as DL,
/// otherwise DL is null.
static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
Constant *Op1, const DataLayout *DL){
// SROA
// Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
// Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
// bits.
if (Opc == Instruction::And && DL) {
unsigned BitWidth = DL->getTypeSizeInBits(Op0->getType()->getScalarType());
APInt KnownZero0(BitWidth, 0), KnownOne0(BitWidth, 0);
APInt KnownZero1(BitWidth, 0), KnownOne1(BitWidth, 0);
computeKnownBits(Op0, KnownZero0, KnownOne0, DL);
computeKnownBits(Op1, KnownZero1, KnownOne1, DL);
if ((KnownOne1 | KnownZero0).isAllOnesValue()) {
// All the bits of Op0 that the 'and' could be masking are already zero.
return Op0;
}
if ((KnownOne0 | KnownZero1).isAllOnesValue()) {
// All the bits of Op1 that the 'and' could be masking are already zero.
return Op1;
}
APInt KnownZero = KnownZero0 | KnownZero1;
APInt KnownOne = KnownOne0 & KnownOne1;
if ((KnownZero | KnownOne).isAllOnesValue()) {
return ConstantInt::get(Op0->getType(), KnownOne);
}
}
// If the constant expr is something like &A[123] - &A[4].f, fold this into a
// constant. This happens frequently when iterating over a global array.
if (Opc == Instruction::Sub && DL) {
GlobalValue *GV1, *GV2;
APInt Offs1, Offs2;
if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *DL))
if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *DL) &&
GV1 == GV2) {
unsigned OpSize = DL->getTypeSizeInBits(Op0->getType());
// (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
// PtrToInt may change the bitwidth so we have convert to the right size
// first.
return ConstantInt::get(Op0->getType(), Offs1.zextOrTrunc(OpSize) -
Offs2.zextOrTrunc(OpSize));
}
}
return nullptr;
}
/// If array indices are not pointer-sized integers, explicitly cast them so
/// that they aren't implicitly casted by the getelementptr.
static Constant *CastGEPIndices(ArrayRef<Constant *> Ops,
Type *ResultTy, const DataLayout *TD,
const TargetLibraryInfo *TLI) {
if (!TD)
return nullptr;
Type *IntPtrTy = TD->getIntPtrType(ResultTy);
bool Any = false;
SmallVector<Constant*, 32> NewIdxs;
for (unsigned i = 1, e = Ops.size(); i != e; ++i) {
if ((i == 1 ||
!isa<StructType>(GetElementPtrInst::getIndexedType(
Ops[0]->getType(),
Ops.slice(1, i - 1)))) &&
Ops[i]->getType() != IntPtrTy) {
Any = true;
NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
true,
IntPtrTy,
true),
Ops[i], IntPtrTy));
} else
NewIdxs.push_back(Ops[i]);
}
if (!Any)
return nullptr;
Constant *C = ConstantExpr::getGetElementPtr(Ops[0], NewIdxs);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (Constant *Folded = ConstantFoldConstantExpression(CE, TD, TLI))
C = Folded;
}
return C;
}
/// Strip the pointer casts, but preserve the address space information.
static Constant* StripPtrCastKeepAS(Constant* Ptr) {
assert(Ptr->getType()->isPointerTy() && "Not a pointer type");
PointerType *OldPtrTy = cast<PointerType>(Ptr->getType());
Ptr = Ptr->stripPointerCasts();
PointerType *NewPtrTy = cast<PointerType>(Ptr->getType());
// Preserve the address space number of the pointer.
if (NewPtrTy->getAddressSpace() != OldPtrTy->getAddressSpace()) {
NewPtrTy = NewPtrTy->getElementType()->getPointerTo(
OldPtrTy->getAddressSpace());
Ptr = ConstantExpr::getPointerCast(Ptr, NewPtrTy);
}
return Ptr;
}
/// If we can symbolically evaluate the GEP constant expression, do so.
static Constant *SymbolicallyEvaluateGEP(ArrayRef<Constant *> Ops,
Type *ResultTy, const DataLayout *TD,
const TargetLibraryInfo *TLI) {
Constant *Ptr = Ops[0];
if (!TD || !Ptr->getType()->getPointerElementType()->isSized() ||
!Ptr->getType()->isPointerTy())
return nullptr;
Type *IntPtrTy = TD->getIntPtrType(Ptr->getType());
Type *ResultElementTy = ResultTy->getPointerElementType();
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
for (unsigned i = 1, e = Ops.size(); i != e; ++i)
if (!isa<ConstantInt>(Ops[i])) {
// If this is "gep i8* Ptr, (sub 0, V)", fold this as:
// "inttoptr (sub (ptrtoint Ptr), V)"
if (Ops.size() == 2 && ResultElementTy->isIntegerTy(8)) {
ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[1]);
assert((!CE || CE->getType() == IntPtrTy) &&
"CastGEPIndices didn't canonicalize index types!");
if (CE && CE->getOpcode() == Instruction::Sub &&
CE->getOperand(0)->isNullValue()) {
Constant *Res = ConstantExpr::getPtrToInt(Ptr, CE->getType());
Res = ConstantExpr::getSub(Res, CE->getOperand(1));
Res = ConstantExpr::getIntToPtr(Res, ResultTy);
if (ConstantExpr *ResCE = dyn_cast<ConstantExpr>(Res))
Res = ConstantFoldConstantExpression(ResCE, TD, TLI);
return Res;
}
}
return nullptr;
}
unsigned BitWidth = TD->getTypeSizeInBits(IntPtrTy);
APInt Offset =
APInt(BitWidth, TD->getIndexedOffset(Ptr->getType(),
makeArrayRef((Value *const*)
Ops.data() + 1,
Ops.size() - 1)));
Ptr = StripPtrCastKeepAS(Ptr);
// If this is a GEP of a GEP, fold it all into a single GEP.
while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
SmallVector<Value *, 4> NestedOps(GEP->op_begin() + 1, GEP->op_end());
// Do not try the incorporate the sub-GEP if some index is not a number.
bool AllConstantInt = true;
for (unsigned i = 0, e = NestedOps.size(); i != e; ++i)
if (!isa<ConstantInt>(NestedOps[i])) {
AllConstantInt = false;
break;
}
if (!AllConstantInt)
break;
Ptr = cast<Constant>(GEP->getOperand(0));
Offset += APInt(BitWidth,
TD->getIndexedOffset(Ptr->getType(), NestedOps));
Ptr = StripPtrCastKeepAS(Ptr);
}
// If the base value for this address is a literal integer value, fold the
// getelementptr to the resulting integer value casted to the pointer type.
APInt BasePtr(BitWidth, 0);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
if (CE->getOpcode() == Instruction::IntToPtr) {
if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
BasePtr = Base->getValue().zextOrTrunc(BitWidth);
}
}
if (Ptr->isNullValue() || BasePtr != 0) {
Constant *C = ConstantInt::get(Ptr->getContext(), Offset + BasePtr);
return ConstantExpr::getIntToPtr(C, ResultTy);
}
// Otherwise form a regular getelementptr. Recompute the indices so that
// we eliminate over-indexing of the notional static type array bounds.
// This makes it easy to determine if the getelementptr is "inbounds".
// Also, this helps GlobalOpt do SROA on GlobalVariables.
Type *Ty = Ptr->getType();
assert(Ty->isPointerTy() && "Forming regular GEP of non-pointer type");
SmallVector<Constant *, 32> NewIdxs;
do {
if (SequentialType *ATy = dyn_cast<SequentialType>(Ty)) {
if (ATy->isPointerTy()) {
// The only pointer indexing we'll do is on the first index of the GEP.
if (!NewIdxs.empty())
break;
// Only handle pointers to sized types, not pointers to functions.
if (!ATy->getElementType()->isSized())
return nullptr;
}
// Determine which element of the array the offset points into.
APInt ElemSize(BitWidth, TD->getTypeAllocSize(ATy->getElementType()));
if (ElemSize == 0)
// The element size is 0. This may be [0 x Ty]*, so just use a zero
// index for this level and proceed to the next level to see if it can
// accommodate the offset.
NewIdxs.push_back(ConstantInt::get(IntPtrTy, 0));
else {
// The element size is non-zero divide the offset by the element
// size (rounding down), to compute the index at this level.
APInt NewIdx = Offset.udiv(ElemSize);
Offset -= NewIdx * ElemSize;
NewIdxs.push_back(ConstantInt::get(IntPtrTy, NewIdx));
}
Ty = ATy->getElementType();
} else if (StructType *STy = dyn_cast<StructType>(Ty)) {
// If we end up with an offset that isn't valid for this struct type, we
// can't re-form this GEP in a regular form, so bail out. The pointer
// operand likely went through casts that are necessary to make the GEP
// sensible.
const StructLayout &SL = *TD->getStructLayout(STy);
if (Offset.uge(SL.getSizeInBytes()))
break;
// Determine which field of the struct the offset points into. The
// getZExtValue is fine as we've already ensured that the offset is
// within the range representable by the StructLayout API.
unsigned ElIdx = SL.getElementContainingOffset(Offset.getZExtValue());
NewIdxs.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
ElIdx));
Offset -= APInt(BitWidth, SL.getElementOffset(ElIdx));
Ty = STy->getTypeAtIndex(ElIdx);
} else {
// We've reached some non-indexable type.
break;
}
} while (Ty != ResultElementTy);
// If we haven't used up the entire offset by descending the static
// type, then the offset is pointing into the middle of an indivisible
// member, so we can't simplify it.
if (Offset != 0)
return nullptr;
// Create a GEP.
Constant *C = ConstantExpr::getGetElementPtr(Ptr, NewIdxs);
assert(C->getType()->getPointerElementType() == Ty &&
"Computed GetElementPtr has unexpected type!");
// If we ended up indexing a member with a type that doesn't match
// the type of what the original indices indexed, add a cast.
if (Ty != ResultElementTy)
C = FoldBitCast(C, ResultTy, *TD);
return C;
}
//===----------------------------------------------------------------------===//
// Constant Folding public APIs
//===----------------------------------------------------------------------===//
/// Try to constant fold the specified instruction.
/// If successful, the constant result is returned, if not, null is returned.
/// Note that this fails if not all of the operands are constant. Otherwise,
/// this function can only fail when attempting to fold instructions like loads
/// and stores, which have no constant expression form.
Constant *llvm::ConstantFoldInstruction(Instruction *I,
const DataLayout *TD,
const TargetLibraryInfo *TLI) {
// Handle PHI nodes quickly here...
if (PHINode *PN = dyn_cast<PHINode>(I)) {
Constant *CommonValue = nullptr;
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *Incoming = PN->getIncomingValue(i);
// If the incoming value is undef then skip it. Note that while we could
// skip the value if it is equal to the phi node itself we choose not to
// because that would break the rule that constant folding only applies if
// all operands are constants.
if (isa<UndefValue>(Incoming))
continue;
// If the incoming value is not a constant, then give up.
Constant *C = dyn_cast<Constant>(Incoming);
if (!C)
return nullptr;
// Fold the PHI's operands.
if (ConstantExpr *NewC = dyn_cast<ConstantExpr>(C))
C = ConstantFoldConstantExpression(NewC, TD, TLI);
// If the incoming value is a different constant to
// the one we saw previously, then give up.
if (CommonValue && C != CommonValue)
return nullptr;
CommonValue = C;
}
// If we reach here, all incoming values are the same constant or undef.
return CommonValue ? CommonValue : UndefValue::get(PN->getType());
}
// Scan the operand list, checking to see if they are all constants, if so,
// hand off to ConstantFoldInstOperands.
SmallVector<Constant*, 8> Ops;
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
Constant *Op = dyn_cast<Constant>(*i);
if (!Op)
return nullptr; // All operands not constant!
// Fold the Instruction's operands.
if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(Op))
Op = ConstantFoldConstantExpression(NewCE, TD, TLI);
Ops.push_back(Op);
}
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
TD, TLI);
if (const LoadInst *LI = dyn_cast<LoadInst>(I))
return ConstantFoldLoadInst(LI, TD);
if (InsertValueInst *IVI = dyn_cast<InsertValueInst>(I)) {
return ConstantExpr::getInsertValue(
cast<Constant>(IVI->getAggregateOperand()),
cast<Constant>(IVI->getInsertedValueOperand()),
IVI->getIndices());
}
if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I)) {
return ConstantExpr::getExtractValue(
cast<Constant>(EVI->getAggregateOperand()),
EVI->getIndices());
}
return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops, TD, TLI);
}
static Constant *
ConstantFoldConstantExpressionImpl(const ConstantExpr *CE, const DataLayout *TD,
const TargetLibraryInfo *TLI,
SmallPtrSetImpl<ConstantExpr *> &FoldedOps) {
SmallVector<Constant *, 8> Ops;
for (User::const_op_iterator i = CE->op_begin(), e = CE->op_end(); i != e;
++i) {
Constant *NewC = cast<Constant>(*i);
// Recursively fold the ConstantExpr's operands. If we have already folded
// a ConstantExpr, we don't have to process it again.
if (ConstantExpr *NewCE = dyn_cast<ConstantExpr>(NewC)) {
if (FoldedOps.insert(NewCE))
NewC = ConstantFoldConstantExpressionImpl(NewCE, TD, TLI, FoldedOps);
}
Ops.push_back(NewC);
}
if (CE->isCompare())
return ConstantFoldCompareInstOperands(CE->getPredicate(), Ops[0], Ops[1],
TD, TLI);
return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(), Ops, TD, TLI);
}
/// Attempt to fold the constant expression
/// using the specified DataLayout. If successful, the constant result is
/// result is returned, if not, null is returned.
Constant *llvm::ConstantFoldConstantExpression(const ConstantExpr *CE,
const DataLayout *TD,
const TargetLibraryInfo *TLI) {
SmallPtrSet<ConstantExpr *, 4> FoldedOps;
return ConstantFoldConstantExpressionImpl(CE, TD, TLI, FoldedOps);
}
/// Attempt to constant fold an instruction with the
/// specified opcode and operands. If successful, the constant result is
/// returned, if not, null is returned. Note that this function can fail when
/// attempting to fold instructions like loads and stores, which have no
/// constant expression form.
///
/// TODO: This function neither utilizes nor preserves nsw/nuw/inbounds/etc
/// information, due to only being passed an opcode and operands. Constant
/// folding using this function strips this information.
///
Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, Type *DestTy,
ArrayRef<Constant *> Ops,
const DataLayout *TD,
const TargetLibraryInfo *TLI) {
// Handle easy binops first.
if (Instruction::isBinaryOp(Opcode)) {
if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1])) {
if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
return C;
}
return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
}
switch (Opcode) {
default: return nullptr;
case Instruction::ICmp:
case Instruction::FCmp: llvm_unreachable("Invalid for compares");
case Instruction::Call:
if (Function *F = dyn_cast<Function>(Ops.back()))
if (canConstantFoldCallTo(F))
return ConstantFoldCall(F, Ops.slice(0, Ops.size() - 1), TLI);
return nullptr;
case Instruction::PtrToInt:
// If the input is a inttoptr, eliminate the pair. This requires knowing
// the width of a pointer, so it can't be done in ConstantExpr::getCast.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && CE->getOpcode() == Instruction::IntToPtr) {
Constant *Input = CE->getOperand(0);
unsigned InWidth = Input->getType()->getScalarSizeInBits();
unsigned PtrWidth = TD->getPointerTypeSizeInBits(CE->getType());
if (PtrWidth < InWidth) {
Constant *Mask =
ConstantInt::get(CE->getContext(),
APInt::getLowBitsSet(InWidth, PtrWidth));
Input = ConstantExpr::getAnd(Input, Mask);
}
// Do a zext or trunc to get to the dest size.
return ConstantExpr::getIntegerCast(Input, DestTy, false);
}
}
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::IntToPtr:
// If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
// the int size is >= the ptr size and the address spaces are the same.
// This requires knowing the width of a pointer, so it can't be done in
// ConstantExpr::getCast.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && CE->getOpcode() == Instruction::PtrToInt) {
Constant *SrcPtr = CE->getOperand(0);
unsigned SrcPtrSize = TD->getPointerTypeSizeInBits(SrcPtr->getType());
unsigned MidIntSize = CE->getType()->getScalarSizeInBits();
if (MidIntSize >= SrcPtrSize) {
unsigned SrcAS = SrcPtr->getType()->getPointerAddressSpace();
if (SrcAS == DestTy->getPointerAddressSpace())
return FoldBitCast(CE->getOperand(0), DestTy, *TD);
}
}
}
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::AddrSpaceCast:
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::BitCast:
if (TD)
return FoldBitCast(Ops[0], DestTy, *TD);
return ConstantExpr::getBitCast(Ops[0], DestTy);
case Instruction::Select:
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
case Instruction::ExtractElement:
return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
case Instruction::InsertElement:
return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
case Instruction::ShuffleVector:
return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
case Instruction::GetElementPtr:
if (Constant *C = CastGEPIndices(Ops, DestTy, TD, TLI))
return C;
if (Constant *C = SymbolicallyEvaluateGEP(Ops, DestTy, TD, TLI))
return C;
return ConstantExpr::getGetElementPtr(Ops[0], Ops.slice(1));
}
}
/// Attempt to constant fold a compare
/// instruction (icmp/fcmp) with the specified operands. If it fails, it
/// returns a constant expression of the specified operands.
Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
Constant *Ops0, Constant *Ops1,
const DataLayout *TD,
const TargetLibraryInfo *TLI) {
// fold: icmp (inttoptr x), null -> icmp x, 0
// fold: icmp (ptrtoint x), 0 -> icmp x, null
// fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
// fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
//
// ConstantExpr::getCompare cannot do this, because it doesn't have TD
// around to know if bit truncation is happening.
if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops0)) {
if (TD && Ops1->isNullValue()) {
if (CE0->getOpcode() == Instruction::IntToPtr) {
Type *IntPtrTy = TD->getIntPtrType(CE0->getType());
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *Null = Constant::getNullValue(C->getType());
return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if (CE0->getOpcode() == Instruction::PtrToInt) {
Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType());
if (CE0->getType() == IntPtrTy) {
Constant *C = CE0->getOperand(0);
Constant *Null = Constant::getNullValue(C->getType());
return ConstantFoldCompareInstOperands(Predicate, C, Null, TD, TLI);
}
}
}
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops1)) {
if (TD && CE0->getOpcode() == CE1->getOpcode()) {
if (CE0->getOpcode() == Instruction::IntToPtr) {
Type *IntPtrTy = TD->getIntPtrType(CE0->getType());
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
IntPtrTy, false);
return ConstantFoldCompareInstOperands(Predicate, C0, C1, TD, TLI);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if (CE0->getOpcode() == Instruction::PtrToInt) {
Type *IntPtrTy = TD->getIntPtrType(CE0->getOperand(0)->getType());
if (CE0->getType() == IntPtrTy &&
CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType()) {
return ConstantFoldCompareInstOperands(Predicate,
CE0->getOperand(0),
CE1->getOperand(0),
TD,
TLI);
}
}
}
}
// icmp eq (or x, y), 0 -> (icmp eq x, 0) & (icmp eq y, 0)
// icmp ne (or x, y), 0 -> (icmp ne x, 0) | (icmp ne y, 0)
if ((Predicate == ICmpInst::ICMP_EQ || Predicate == ICmpInst::ICMP_NE) &&
CE0->getOpcode() == Instruction::Or && Ops1->isNullValue()) {
Constant *LHS =
ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(0), Ops1,
TD, TLI);
Constant *RHS =
ConstantFoldCompareInstOperands(Predicate, CE0->getOperand(1), Ops1,
TD, TLI);
unsigned OpC =
Predicate == ICmpInst::ICMP_EQ ? Instruction::And : Instruction::Or;
Constant *Ops[] = { LHS, RHS };
return ConstantFoldInstOperands(OpC, LHS->getType(), Ops, TD, TLI);
}
}
return ConstantExpr::getCompare(Predicate, Ops0, Ops1);
}
/// Given a constant and a getelementptr constantexpr, return the constant value
/// being addressed by the constant expression, or null if something is funny
/// and we can't decide.
Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
ConstantExpr *CE) {
if (!CE->getOperand(1)->isNullValue())
return nullptr; // Do not allow stepping over the value!
// Loop over all of the operands, tracking down which value we are
// addressing.
for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i) {
C = C->getAggregateElement(CE->getOperand(i));
if (!C)
return nullptr;
}
return C;
}
/// Given a constant and getelementptr indices (with an *implied* zero pointer
/// index that is not in the list), return the constant value being addressed by
/// a virtual load, or null if something is funny and we can't decide.
Constant *llvm::ConstantFoldLoadThroughGEPIndices(Constant *C,
ArrayRef<Constant*> Indices) {
// Loop over all of the operands, tracking down which value we are
// addressing.
for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
C = C->getAggregateElement(Indices[i]);
if (!C)
return nullptr;
}
return C;
}
//===----------------------------------------------------------------------===//
// Constant Folding for Calls
//
/// Return true if it's even possible to fold a call to the specified function.
bool llvm::canConstantFoldCallTo(const Function *F) {
switch (F->getIntrinsicID()) {
case Intrinsic::fabs:
case Intrinsic::minnum:
case Intrinsic::maxnum:
case Intrinsic::log:
case Intrinsic::log2:
case Intrinsic::log10:
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::floor:
case Intrinsic::ceil:
case Intrinsic::sqrt:
case Intrinsic::pow:
case Intrinsic::powi:
case Intrinsic::bswap:
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
case Intrinsic::fma:
case Intrinsic::fmuladd:
case Intrinsic::copysign:
case Intrinsic::round:
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::umul_with_overflow:
case Intrinsic::convert_from_fp16:
case Intrinsic::convert_to_fp16:
case Intrinsic::x86_sse_cvtss2si:
case Intrinsic::x86_sse_cvtss2si64:
case Intrinsic::x86_sse_cvttss2si:
case Intrinsic::x86_sse_cvttss2si64:
case Intrinsic::x86_sse2_cvtsd2si:
case Intrinsic::x86_sse2_cvtsd2si64:
case Intrinsic::x86_sse2_cvttsd2si:
case Intrinsic::x86_sse2_cvttsd2si64:
return true;
default:
return false;
case 0: break;
}
if (!F->hasName())
return false;
StringRef Name = F->getName();
// In these cases, the check of the length is required. We don't want to
// return true for a name like "cos\0blah" which strcmp would return equal to
// "cos", but has length 8.
switch (Name[0]) {
default: return false;
case 'a':
return Name == "acos" || Name == "asin" || Name == "atan" || Name =="atan2";
case 'c':
return Name == "cos" || Name == "ceil" || Name == "cosf" || Name == "cosh";
case 'e':
return Name == "exp" || Name == "exp2";
case 'f':
return Name == "fabs" || Name == "fmod" || Name == "floor";
case 'l':
return Name == "log" || Name == "log10";
case 'p':
return Name == "pow";
case 's':
return Name == "sin" || Name == "sinh" || Name == "sqrt" ||
Name == "sinf" || Name == "sqrtf";
case 't':
return Name == "tan" || Name == "tanh";
}
}
static Constant *GetConstantFoldFPValue(double V, Type *Ty) {
if (Ty->isHalfTy()) {
APFloat APF(V);
bool unused;
APF.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &unused);
return ConstantFP::get(Ty->getContext(), APF);
}
if (Ty->isFloatTy())
return ConstantFP::get(Ty->getContext(), APFloat((float)V));
if (Ty->isDoubleTy())
return ConstantFP::get(Ty->getContext(), APFloat(V));
llvm_unreachable("Can only constant fold half/float/double");
}
namespace {
/// Clear the floating-point exception state.
static inline void llvm_fenv_clearexcept() {
#if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT
feclearexcept(FE_ALL_EXCEPT);
#endif
errno = 0;
}
/// Test if a floating-point exception was raised.
static inline bool llvm_fenv_testexcept() {
int errno_val = errno;
if (errno_val == ERANGE || errno_val == EDOM)
return true;
#if defined(HAVE_FENV_H) && HAVE_DECL_FE_ALL_EXCEPT && HAVE_DECL_FE_INEXACT
if (fetestexcept(FE_ALL_EXCEPT & ~FE_INEXACT))
return true;
#endif
return false;
}
} // End namespace
static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
Type *Ty) {
llvm_fenv_clearexcept();
V = NativeFP(V);
if (llvm_fenv_testexcept()) {
llvm_fenv_clearexcept();
return nullptr;
}
return GetConstantFoldFPValue(V, Ty);
}
static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
double V, double W, Type *Ty) {
llvm_fenv_clearexcept();
V = NativeFP(V, W);
if (llvm_fenv_testexcept()) {
llvm_fenv_clearexcept();
return nullptr;
}
return GetConstantFoldFPValue(V, Ty);
}
/// Attempt to fold an SSE floating point to integer conversion of a constant
/// floating point. If roundTowardZero is false, the default IEEE rounding is
/// used (toward nearest, ties to even). This matches the behavior of the
/// non-truncating SSE instructions in the default rounding mode. The desired
/// integer type Ty is used to select how many bits are available for the
/// result. Returns null if the conversion cannot be performed, otherwise
/// returns the Constant value resulting from the conversion.
static Constant *ConstantFoldConvertToInt(const APFloat &Val,
bool roundTowardZero, Type *Ty) {
// All of these conversion intrinsics form an integer of at most 64bits.
unsigned ResultWidth = Ty->getIntegerBitWidth();
assert(ResultWidth <= 64 &&
"Can only constant fold conversions to 64 and 32 bit ints");
uint64_t UIntVal;
bool isExact = false;
APFloat::roundingMode mode = roundTowardZero? APFloat::rmTowardZero
: APFloat::rmNearestTiesToEven;
APFloat::opStatus status = Val.convertToInteger(&UIntVal, ResultWidth,
/*isSigned=*/true, mode,
&isExact);
if (status != APFloat::opOK && status != APFloat::opInexact)
return nullptr;
return ConstantInt::get(Ty, UIntVal, /*isSigned=*/true);
}
static double getValueAsDouble(ConstantFP *Op) {
Type *Ty = Op->getType();
if (Ty->isFloatTy())
return Op->getValueAPF().convertToFloat();
if (Ty->isDoubleTy())
return Op->getValueAPF().convertToDouble();
bool unused;
APFloat APF = Op->getValueAPF();
APF.convert(APFloat::IEEEdouble, APFloat::rmNearestTiesToEven, &unused);
return APF.convertToDouble();
}
static Constant *ConstantFoldScalarCall(StringRef Name, unsigned IntrinsicID,
Type *Ty, ArrayRef<Constant *> Operands,
const TargetLibraryInfo *TLI) {
if (Operands.size() == 1) {
if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
if (IntrinsicID == Intrinsic::convert_to_fp16) {
APFloat Val(Op->getValueAPF());
bool lost = false;
Val.convert(APFloat::IEEEhalf, APFloat::rmNearestTiesToEven, &lost);
return ConstantInt::get(Ty->getContext(), Val.bitcastToAPInt());
}
if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
return nullptr;
if (IntrinsicID == Intrinsic::round) {
APFloat V = Op->getValueAPF();
V.roundToIntegral(APFloat::rmNearestTiesToAway);
return ConstantFP::get(Ty->getContext(), V);
}
/// We only fold functions with finite arguments. Folding NaN and inf is
/// likely to be aborted with an exception anyway, and some host libms
/// have known errors raising exceptions.
if (Op->getValueAPF().isNaN() || Op->getValueAPF().isInfinity())
return nullptr;
/// Currently APFloat versions of these functions do not exist, so we use
/// the host native double versions. Float versions are not called
/// directly but for all these it is true (float)(f((double)arg)) ==
/// f(arg). Long double not supported yet.
double V = getValueAsDouble(Op);
switch (IntrinsicID) {
default: break;
case Intrinsic::fabs:
return ConstantFoldFP(fabs, V, Ty);
#if HAVE_LOG2
case Intrinsic::log2:
return ConstantFoldFP(log2, V, Ty);
#endif
#if HAVE_LOG
case Intrinsic::log:
return ConstantFoldFP(log, V, Ty);
#endif
#if HAVE_LOG10
case Intrinsic::log10:
return ConstantFoldFP(log10, V, Ty);
#endif
#if HAVE_EXP
case Intrinsic::exp:
return ConstantFoldFP(exp, V, Ty);
#endif
#if HAVE_EXP2
case Intrinsic::exp2:
return ConstantFoldFP(exp2, V, Ty);
#endif
case Intrinsic::floor:
return ConstantFoldFP(floor, V, Ty);
case Intrinsic::ceil:
return ConstantFoldFP(ceil, V, Ty);
}
if (!TLI)
return nullptr;
switch (Name[0]) {
case 'a':
if (Name == "acos" && TLI->has(LibFunc::acos))
return ConstantFoldFP(acos, V, Ty);
else if (Name == "asin" && TLI->has(LibFunc::asin))
return ConstantFoldFP(asin, V, Ty);
else if (Name == "atan" && TLI->has(LibFunc::atan))
return ConstantFoldFP(atan, V, Ty);
break;
case 'c':
if (Name == "ceil" && TLI->has(LibFunc::ceil))
return ConstantFoldFP(ceil, V, Ty);
else if (Name == "cos" && TLI->has(LibFunc::cos))
return ConstantFoldFP(cos, V, Ty);
else if (Name == "cosh" && TLI->has(LibFunc::cosh))
return ConstantFoldFP(cosh, V, Ty);
else if (Name == "cosf" && TLI->has(LibFunc::cosf))
return ConstantFoldFP(cos, V, Ty);
break;
case 'e':
if (Name == "exp" && TLI->has(LibFunc::exp))
return ConstantFoldFP(exp, V, Ty);
if (Name == "exp2" && TLI->has(LibFunc::exp2)) {
// Constant fold exp2(x) as pow(2,x) in case the host doesn't have a
// C99 library.
return ConstantFoldBinaryFP(pow, 2.0, V, Ty);
}
break;
case 'f':
if (Name == "fabs" && TLI->has(LibFunc::fabs))
return ConstantFoldFP(fabs, V, Ty);
else if (Name == "floor" && TLI->has(LibFunc::floor))
return ConstantFoldFP(floor, V, Ty);
break;
case 'l':
if (Name == "log" && V > 0 && TLI->has(LibFunc::log))
return ConstantFoldFP(log, V, Ty);
else if (Name == "log10" && V > 0 && TLI->has(LibFunc::log10))
return ConstantFoldFP(log10, V, Ty);
else if (IntrinsicID == Intrinsic::sqrt &&
(Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy())) {
if (V >= -0.0)
return ConstantFoldFP(sqrt, V, Ty);
else {
// Unlike the sqrt definitions in C/C++, POSIX, and IEEE-754 - which
// all guarantee or favor returning NaN - the square root of a
// negative number is not defined for the LLVM sqrt intrinsic.
// This is because the intrinsic should only be emitted in place of
// libm's sqrt function when using "no-nans-fp-math".
return UndefValue::get(Ty);
}
}
break;
case 's':
if (Name == "sin" && TLI->has(LibFunc::sin))
return ConstantFoldFP(sin, V, Ty);
else if (Name == "sinh" && TLI->has(LibFunc::sinh))
return ConstantFoldFP(sinh, V, Ty);
else if (Name == "sqrt" && V >= 0 && TLI->has(LibFunc::sqrt))
return ConstantFoldFP(sqrt, V, Ty);
else if (Name == "sqrtf" && V >= 0 && TLI->has(LibFunc::sqrtf))
return ConstantFoldFP(sqrt, V, Ty);
else if (Name == "sinf" && TLI->has(LibFunc::sinf))
return ConstantFoldFP(sin, V, Ty);
break;
case 't':
if (Name == "tan" && TLI->has(LibFunc::tan))
return ConstantFoldFP(tan, V, Ty);
else if (Name == "tanh" && TLI->has(LibFunc::tanh))
return ConstantFoldFP(tanh, V, Ty);
break;
default:
break;
}
return nullptr;
}
if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
switch (IntrinsicID) {
case Intrinsic::bswap:
return ConstantInt::get(Ty->getContext(), Op->getValue().byteSwap());
case Intrinsic::ctpop:
return ConstantInt::get(Ty, Op->getValue().countPopulation());
case Intrinsic::convert_from_fp16: {
APFloat Val(APFloat::IEEEhalf, Op->getValue());
bool lost = false;
APFloat::opStatus status =
Val.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven, &lost);
// Conversion is always precise.
(void)status;
assert(status == APFloat::opOK && !lost &&
"Precision lost during fp16 constfolding");
return ConstantFP::get(Ty->getContext(), Val);
}
default:
return nullptr;
}
}
// Support ConstantVector in case we have an Undef in the top.
if (isa<ConstantVector>(Operands[0]) ||
isa<ConstantDataVector>(Operands[0])) {
Constant *Op = cast<Constant>(Operands[0]);
switch (IntrinsicID) {
default: break;
case Intrinsic::x86_sse_cvtss2si:
case Intrinsic::x86_sse_cvtss2si64:
case Intrinsic::x86_sse2_cvtsd2si:
case Intrinsic::x86_sse2_cvtsd2si64:
if (ConstantFP *FPOp =
dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
return ConstantFoldConvertToInt(FPOp->getValueAPF(),
/*roundTowardZero=*/false, Ty);
case Intrinsic::x86_sse_cvttss2si:
case Intrinsic::x86_sse_cvttss2si64:
case Intrinsic::x86_sse2_cvttsd2si:
case Intrinsic::x86_sse2_cvttsd2si64:
if (ConstantFP *FPOp =
dyn_cast_or_null<ConstantFP>(Op->getAggregateElement(0U)))
return ConstantFoldConvertToInt(FPOp->getValueAPF(),
/*roundTowardZero=*/true, Ty);
}
}
if (isa<UndefValue>(Operands[0])) {
if (IntrinsicID == Intrinsic::bswap)
return Operands[0];
return nullptr;
}
return nullptr;
}
if (Operands.size() == 2) {
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
if (!Ty->isHalfTy() && !Ty->isFloatTy() && !Ty->isDoubleTy())
return nullptr;
double Op1V = getValueAsDouble(Op1);
if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
if (Op2->getType() != Op1->getType())
return nullptr;
double Op2V = getValueAsDouble(Op2);
if (IntrinsicID == Intrinsic::pow) {
return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
}
if (IntrinsicID == Intrinsic::copysign) {
APFloat V1 = Op1->getValueAPF();
APFloat V2 = Op2->getValueAPF();
V1.copySign(V2);
return ConstantFP::get(Ty->getContext(), V1);
}
if (IntrinsicID == Intrinsic::minnum) {
const APFloat &C1 = Op1->getValueAPF();
const APFloat &C2 = Op2->getValueAPF();
return ConstantFP::get(Ty->getContext(), minnum(C1, C2));
}
if (IntrinsicID == Intrinsic::maxnum) {
const APFloat &C1 = Op1->getValueAPF();
const APFloat &C2 = Op2->getValueAPF();
return ConstantFP::get(Ty->getContext(), maxnum(C1, C2));
}
if (!TLI)
return nullptr;
if (Name == "pow" && TLI->has(LibFunc::pow))
return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
if (Name == "fmod" && TLI->has(LibFunc::fmod))
return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
if (Name == "atan2" && TLI->has(LibFunc::atan2))
return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
} else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
if (IntrinsicID == Intrinsic::powi && Ty->isHalfTy())
return ConstantFP::get(Ty->getContext(),
APFloat((float)std::pow((float)Op1V,
(int)Op2C->getZExtValue())));
if (IntrinsicID == Intrinsic::powi && Ty->isFloatTy())
return ConstantFP::get(Ty->getContext(),
APFloat((float)std::pow((float)Op1V,
(int)Op2C->getZExtValue())));
if (IntrinsicID == Intrinsic::powi && Ty->isDoubleTy())
return ConstantFP::get(Ty->getContext(),
APFloat((double)std::pow((double)Op1V,
(int)Op2C->getZExtValue())));
}
return nullptr;
}
if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
switch (IntrinsicID) {
default: break;
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow:
case Intrinsic::ssub_with_overflow:
case Intrinsic::usub_with_overflow:
case Intrinsic::smul_with_overflow:
case Intrinsic::umul_with_overflow: {
APInt Res;
bool Overflow;
switch (IntrinsicID) {
default: llvm_unreachable("Invalid case");
case Intrinsic::sadd_with_overflow:
Res = Op1->getValue().sadd_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::uadd_with_overflow:
Res = Op1->getValue().uadd_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::ssub_with_overflow:
Res = Op1->getValue().ssub_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::usub_with_overflow:
Res = Op1->getValue().usub_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::smul_with_overflow:
Res = Op1->getValue().smul_ov(Op2->getValue(), Overflow);
break;
case Intrinsic::umul_with_overflow:
Res = Op1->getValue().umul_ov(Op2->getValue(), Overflow);
break;
}
Constant *Ops[] = {
ConstantInt::get(Ty->getContext(), Res),
ConstantInt::get(Type::getInt1Ty(Ty->getContext()), Overflow)
};
return ConstantStruct::get(cast<StructType>(Ty), Ops);
}
case Intrinsic::cttz:
if (Op2->isOne() && Op1->isZero()) // cttz(0, 1) is undef.
return UndefValue::get(Ty);
return ConstantInt::get(Ty, Op1->getValue().countTrailingZeros());
case Intrinsic::ctlz:
if (Op2->isOne() && Op1->isZero()) // ctlz(0, 1) is undef.
return UndefValue::get(Ty);
return ConstantInt::get(Ty, Op1->getValue().countLeadingZeros());
}
}
return nullptr;
}
return nullptr;
}
if (Operands.size() != 3)
return nullptr;
if (const ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
if (const ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
if (const ConstantFP *Op3 = dyn_cast<ConstantFP>(Operands[2])) {
switch (IntrinsicID) {
default: break;
case Intrinsic::fma:
case Intrinsic::fmuladd: {
APFloat V = Op1->getValueAPF();
APFloat::opStatus s = V.fusedMultiplyAdd(Op2->getValueAPF(),
Op3->getValueAPF(),
APFloat::rmNearestTiesToEven);
if (s != APFloat::opInvalidOp)
return ConstantFP::get(Ty->getContext(), V);
return nullptr;
}
}
}
}
}
return nullptr;
}
static Constant *ConstantFoldVectorCall(StringRef Name, unsigned IntrinsicID,
VectorType *VTy,
ArrayRef<Constant *> Operands,
const TargetLibraryInfo *TLI) {
SmallVector<Constant *, 4> Result(VTy->getNumElements());
SmallVector<Constant *, 4> Lane(Operands.size());
Type *Ty = VTy->getElementType();
for (unsigned I = 0, E = VTy->getNumElements(); I != E; ++I) {
// Gather a column of constants.
for (unsigned J = 0, JE = Operands.size(); J != JE; ++J) {
Constant *Agg = Operands[J]->getAggregateElement(I);
if (!Agg)
return nullptr;
Lane[J] = Agg;
}
// Use the regular scalar folding to simplify this column.
Constant *Folded = ConstantFoldScalarCall(Name, IntrinsicID, Ty, Lane, TLI);
if (!Folded)
return nullptr;
Result[I] = Folded;
}
return ConstantVector::get(Result);
}
/// Attempt to constant fold a call to the specified function
/// with the specified arguments, returning null if unsuccessful.
Constant *
llvm::ConstantFoldCall(Function *F, ArrayRef<Constant *> Operands,
const TargetLibraryInfo *TLI) {
if (!F->hasName())
return nullptr;
StringRef Name = F->getName();
Type *Ty = F->getReturnType();
if (VectorType *VTy = dyn_cast<VectorType>(Ty))
return ConstantFoldVectorCall(Name, F->getIntrinsicID(), VTy, Operands, TLI);
return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI);
}
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