-/// GetBaseWithConstantOffset - Analyze the specified pointer to see if it can
-/// be expressed as a base pointer plus a constant offset. Return the base and
-/// offset to the caller.
-static Value *GetBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
- const TargetData &TD) {
- Operator *PtrOp = dyn_cast<Operator>(Ptr);
- if (PtrOp == 0) return Ptr;
-
- // Just look through bitcasts.
- if (PtrOp->getOpcode() == Instruction::BitCast)
- return GetBaseWithConstantOffset(PtrOp->getOperand(0), Offset, TD);
-
- // If this is a GEP with constant indices, we can look through it.
- GEPOperator *GEP = dyn_cast<GEPOperator>(PtrOp);
- if (GEP == 0 || !GEP->hasAllConstantIndices()) return Ptr;
-
- gep_type_iterator GTI = gep_type_begin(GEP);
- for (User::op_iterator I = GEP->idx_begin(), E = GEP->idx_end(); I != E;
- ++I, ++GTI) {
- ConstantInt *OpC = cast<ConstantInt>(*I);
- if (OpC->isZero()) continue;
-
- // Handle a struct and array indices which add their offset to the pointer.
- if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
- Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
- } else {
- uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
- Offset += OpC->getSExtValue()*Size;
- }
- }
-
- // Re-sign extend from the pointer size if needed to get overflow edge cases
- // right.
- unsigned PtrSize = TD.getPointerSizeInBits();
- if (PtrSize < 64)
- Offset = (Offset << (64-PtrSize)) >> (64-PtrSize);
-
- return GetBaseWithConstantOffset(GEP->getPointerOperand(), Offset, TD);
-}
-
-