On Mon, Mar 6, 2017 at 11:32 PM, Dibyendu Majumdar <mobile@xxxxxxxxxxxxxxx> wrote: > > Sparse-llvm appears to bypass the normal struct GEP in LLVM. It > basically casts everything to char *, uses GEP to obtain a pointer to > member, and then casts it back to member type. So this should work for > structs and unions. That is exactly my question. I haven't understand how this by pass can work in all the situation. > > This case is more about handing pointer arithmetic correctly. Here GEP > is being used as array element access and not for struct member > access. Even using array element access, I still have some question regarding the the mapping process of the array index. Correct me if I am wrong, the GEP indices are express as array index. So after convert to (char*) + offset, the offset will express as n*(sizeof(element type)). "n" is the array index. However, the OP_ADD instruction, the offset is byte offset value. The offset part might not be align to n*(sizeof(array_elelment)). Assume we can use some pack struct to get some member located not at the natural alignment offset. Even if the offset is at the type size alignment, shouldn't the indices express as ( offset / sizeof(element type))? What do I miss? Chris -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
