llvm dev - Feb 2011 - [LLVMdev] Getting load/store byte size

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!
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Hi nullnull,
> 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)
use getTypeStoreSize defined in TargetData.

Ciao, Duncan.

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!