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//===- Local.cpp - Functions to perform local transformations -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This family of functions perform various local transformations to the
// program.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Utils/Local.h"
#include "llvm/ADT/Twine.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.h"
using namespace llvm;
Value *llvm::emitGEPOffset(IRBuilderBase *Builder, const DataLayout &DL,
User *GEP, bool NoAssumptions) {
GEPOperator *GEPOp = cast<GEPOperator>(GEP);
Type *IntIdxTy = DL.getIndexType(GEP->getType());
Value *Result = nullptr;
// If the GEP is inbounds, we know that none of the addressing operations will
// overflow in a signed sense.
bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
// Build a mask for high order bits.
unsigned IntPtrWidth = IntIdxTy->getScalarType()->getIntegerBitWidth();
uint64_t PtrSizeMask =
std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
++i, ++GTI) {
Value *Op = *i;
uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
Value *Offset;
if (Constant *OpC = dyn_cast<Constant>(Op)) {
if (OpC->isZeroValue())
continue;
// Handle a struct index, which adds its field offset to the pointer.
if (StructType *STy = GTI.getStructTypeOrNull()) {
uint64_t OpValue = OpC->getUniqueInteger().getZExtValue();
Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
if (!Size)
continue;
Offset = ConstantInt::get(IntIdxTy, Size);
} else {
// Splat the constant if needed.
if (IntIdxTy->isVectorTy() && !OpC->getType()->isVectorTy())
OpC = ConstantVector::getSplat(
cast<VectorType>(IntIdxTy)->getElementCount(), OpC);
Constant *Scale = ConstantInt::get(IntIdxTy, Size);
Constant *OC =
ConstantExpr::getIntegerCast(OpC, IntIdxTy, true /*SExt*/);
Offset =
ConstantExpr::getMul(OC, Scale, false /*NUW*/, isInBounds /*NSW*/);
}
} else {
// Splat the index if needed.
if (IntIdxTy->isVectorTy() && !Op->getType()->isVectorTy())
Op = Builder->CreateVectorSplat(
cast<FixedVectorType>(IntIdxTy)->getNumElements(), Op);
// Convert to correct type.
if (Op->getType() != IntIdxTy)
Op = Builder->CreateIntCast(Op, IntIdxTy, true, Op->getName() + ".c");
if (Size != 1) {
// We'll let instcombine(mul) convert this to a shl if possible.
Op = Builder->CreateMul(Op, ConstantInt::get(IntIdxTy, Size),
GEP->getName() + ".idx", false /*NUW*/,
isInBounds /*NSW*/);
}
Offset = Op;
}
if (Result)
Result = Builder->CreateAdd(Result, Offset, GEP->getName() + ".offs",
false /*NUW*/, isInBounds /*NSW*/);
else
Result = Offset;
}
return Result ? Result : Constant::getNullValue(IntIdxTy);
}
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