- Value *Addr = new PtrToIntInst(NewGEP, IntPtrTy, "", GEP);
- Addr = BinaryOperator::CreateAdd(
- Addr, ConstantInt::get(IntPtrTy, AccumulativeByteOffset, true), "", GEP);
- Addr = new IntToPtrInst(Addr, GEP->getType(), "", GEP);
+ uint64_t ElementTypeSizeOfGEP =
+ DL->getTypeAllocSize(GEP->getType()->getElementType());
+ if (AccumulativeByteOffset % ElementTypeSizeOfGEP == 0) {
+ // Very likely. As long as %gep is natually aligned, the byte offset we
+ // extracted should be a multiple of sizeof(*%gep).
+ // Per ANSI C standard, signed / unsigned = unsigned. Therefore, we
+ // cast ElementTypeSizeOfGEP to signed.
+ int64_t Index =
+ AccumulativeByteOffset / static_cast<int64_t>(ElementTypeSizeOfGEP);
+ NewGEP = GetElementPtrInst::Create(
+ NewGEP, ConstantInt::get(IntPtrTy, Index, true), GEP->getName(), GEP);
+ } else {
+ // Unlikely but possible. For example,
+ // #pragma pack(1)
+ // struct S {
+ // int a[3];
+ // int64 b[8];
+ // };
+ // #pragma pack()
+ //
+ // Suppose the gep before extraction is &s[i + 1].b[j + 3]. After
+ // extraction, it becomes &s[i].b[j] and AccumulativeByteOffset is
+ // sizeof(S) + 3 * sizeof(int64) = 100, which is not a multiple of
+ // sizeof(int64).
+ //
+ // Emit an uglygep in this case.
+ Type *I8PtrTy = Type::getInt8PtrTy(GEP->getContext(),
+ GEP->getPointerAddressSpace());
+ NewGEP = new BitCastInst(NewGEP, I8PtrTy, "", GEP);
+ NewGEP = GetElementPtrInst::Create(
+ NewGEP, ConstantInt::get(IntPtrTy, AccumulativeByteOffset, true),
+ "uglygep", GEP);
+ if (GEP->getType() != I8PtrTy)
+ NewGEP = new BitCastInst(NewGEP, GEP->getType(), GEP->getName(), GEP);
+ }