[llvm-dev] Reliably mapping memcpy intrinsic

Hiroshi Yamauchi via llvm-dev llvm-dev at lists.llvm.org
Mon Mar 30 08:41:31 PDT 2020

I think setting MaxStoresPerMemcpy to zero (eg.
lib/Target/X86/X86ISelLowering.cpp) may do the trick. As it does not seem
to be a flag, it would require a source edit.

On Fri, Mar 27, 2020 at 9:26 AM Matt Fysh via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Similar to how `operator new(size)` can be overridden during linking, to
> capture and customize all memory allocation operations, I'd like to be able
> to capture all scenarios where memory is copied or moved. I've tried to use
> `--wrap memcpy` with some success, however I've noticed that in some
> instances (e.g. copying a small struct) the memcpy instruction in the IR is
> replaced with a sequence of movq instructions, and the wrap function is not
> able to hook into that piece of the code.
> Is there a way to ensure all llvm.memcpy intrinsics in the IR are always
> lowered to call the memcpy symbol?
> Failing that approach, can you suggest other ways to plug into the desired
> memory options? I'd like to hook into every memory operation that has a
> source and a destination address (copy, move, etc) so I can trace the
> passage of symbols through an executing program.
> Thankyou
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