static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
bool &VariableIdxFound, const TargetData &TD) {
// Skip over the first indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
/*skip along*/;
// Compute the offset implied by the rest of the indices.
int64_t Offset = 0;
for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
if (OpC == 0)
return VariableIdxFound = true;
if (OpC->isZero()) continue; // No offset.
// Handle struct indices, which add their field offset to the pointer.
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
continue;
}
// Otherwise, we have a sequential type like an array or vector. Multiply
// the index by the ElementSize.
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
Offset += Size*OpC->getSExtValue();
}
return Offset;
}
static void ComputeStructureFieldIndices(const Type *Ty, unsigned Offset,
std::vector<unsigned> &Idxs,
const TargetData &TD) {
if (Ty->isFirstClassType()) {
assert(Offset == 0 && "Illegal structure index!");
return;
}
if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
ComputeStructureFieldIndices(STy->getElementType(), Offset, Idxs, TD);
} else if (const StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TD.getStructLayout(STy);
std::vector<uint64_t>::const_iterator SI =
std::upper_bound(SL->MemberOffsets.begin(), SL->MemberOffsets.end(),
Offset);
assert(SI != SL->MemberOffsets.begin() && "Offset not in structure type!");
--SI;
assert(*SI <= Offset && "upper_bound didn't work");
assert((SI == SL->MemberOffsets.begin() || *(SI-1) < Offset) &&
(SI+1 == SL->MemberOffsets.end() || *(SI+1) > Offset) &&
"Upper bound didn't work!");
Offset -= *SI; // Skip over the offset to this structure field.
unsigned Idx = SI - SL->MemberOffsets.begin();
assert(Idx < STy->getNumElements() && "Illegal structure index");
Idxs.push_back(Idx);
ComputeStructureFieldIndices(STy->getElementType(Idx), Offset, Idxs, TD);
} else {
assert(0 && "Unknown type to index into!");
}
}
static unsigned getTypeSize(TargetData &TD, Type *type) {
if (type->isFunctionTy()) /* it is not sized, weird */
return TD.getPointerSize();
if (!type->isSized())
return 100; /* FIXME */
if (StructType *ST = dyn_cast<StructType>(type))
return TD.getStructLayout(ST)->getSizeInBytes();
return TD.getTypeAllocSize(type);
}
/// IsConstantOffsetFromGlobal - If this constant is actually 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,
int64_t &Offset, const TargetData &TD) {
// Trivial case, constant is the global.
if ((GV = dyn_cast<GlobalValue>(C))) {
Offset = 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)
return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
// i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
if (CE->getOpcode() == Instruction::GetElementPtr) {
// Cannot compute this if the element type of the pointer is missing size
// info.
if (!cast<PointerType>(CE->getOperand(0)->getType())->getElementType()->isSized())
return false;
// If the base isn't a global+constant, we aren't either.
if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
return false;
// Otherwise, add any offset that our operands provide.
gep_type_iterator GTI = gep_type_begin(CE);
for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i, ++GTI) {
ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(i));
if (!CI) return false; // Index isn't a simple constant?
if (CI->getZExtValue() == 0) continue; // Not adding anything.
if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
// N = N + Offset
Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
} else {
const SequentialType *SQT = cast<SequentialType>(*GTI);
Offset += TD.getTypeSize(SQT->getElementType())*CI->getSExtValue();
}
}
return true;
}
return false;
}
