[LLVMdev] Getting load/store byte size

[Alexander Potapenko]

You can take a look at
http://code.google.com/p/data-race-test/source/browse/trunk/llvm/opt/ThreadSanitizer/ThreadSanitizer.cpp,
where I do practically the same. The routine that obtains the size is
getMopPtrSize(), getting the addresses is done in instrumentMop().

Alex

On Thu, Feb 17, 2011 at 9:06 PM, nullnull <null.function at gmail.com> wrote:
> I'm instrumenting memory loads and stores in a LLVM module pass. In this
> work, I need to do
> (1) Getting memory address of the operand, (Looks I've done correctly)
> (2) Getting memory read/write size, (Question)
> (3) Location id of the load/store instruction. (Easy, I've done)
>
> For example, say that I'm reading a local variable 'a':
>
> %1 = load i32* %a, align 4
>
> I need to know the address of the variable 'a' and the size. Of course,
> memory loads/stores could be from general GEP or global variables.
>
> Getting the address was easily doable by using
> "PtrToIntInst(load_inst->getPointerOperand(), ...)". However, getting
> load/store size wasn't that straight forward. In this example, it should be
> four bytes. I tried to get the Type* from the getPointerOperand() and tried
> to retrieve the size of the type, but failed.
>
> Question:
> [1] How can I retrieve the read/write size of load/store instruction?
>
>
> I have another question. If I can get the size, then what would be the
> maximum size? Obviously, 1 ~ 8 bytes for built-in types, but wondering even
> the larger size could be obtained. I suspect a vector load instruction could
> load up to 32 bytes (= 256 bits, in case of x86 AVX).
>
> Question:
> [2] What would be the maximum size of load/store operand?
>
>
> Thank you!