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//===- Local.h - Functions to perform local transformations -----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This family of functions perform various local transformations to the
// program.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_UTILS_LOCAL_H
#define LLVM_ANALYSIS_UTILS_LOCAL_H
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
namespace llvm {
/// Given a getelementptr instruction/constantexpr, emit the code necessary to
/// compute the offset from the base pointer (without adding in the base
/// pointer). Return the result as a signed integer of intptr size.
/// When NoAssumptions is true, no assumptions about index computation not
/// overflowing is made.
template <typename IRBuilderTy>
Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
bool NoAssumptions = false) {
GEPOperator *GEPOp = cast<GEPOperator>(GEP);
Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
Value *Result = Constant::getNullValue(IntPtrTy);
// If the GEP is inbounds, we know that none of the addressing operations will
// overflow in an unsigned sense.
bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
// Build a mask for high order bits.
unsigned IntPtrWidth = IntPtrTy->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;
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()) {
if (OpC->getType()->isVectorTy())
OpC = OpC->getSplatValue();
uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
if (Size)
Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
GEP->getName()+".offs");
continue;
}
Constant *Scale = ConstantInt::get(IntPtrTy, Size);
Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
// Emit an add instruction.
Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
continue;
}
// Convert to correct type.
if (Op->getType() != IntPtrTy)
Op = Builder->CreateIntCast(Op, IntPtrTy, 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(IntPtrTy, Size),
GEP->getName()+".idx", isInBounds /*NUW*/);
}
// Emit an add instruction.
Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
}
return Result;
}
}
#endif // LLVM_TRANSFORMS_UTILS_LOCAL_H
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