[PATCH] D72666: [IR] ArgMemOnly functions with WriteOnly ptr args do not read memory.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

In D72666#1818532 <https://reviews.llvm.org/D72666#1818532>, @jdoerfert wrote:

> In D72666#1818407 <https://reviews.llvm.org/D72666#1818407>, @efriedma wrote:
>
> > I'd prefer to just add writeonly markings in places where they're missing.  For llvm.memset in particular, can we mark it IntrWriteMem?
>


Yes we should probably just mark llvm.memset as IntrWriteMem.

> We could "deduce" it, based on this logic, and then add `writeonly`. That would work for non intrinsics as well.

Yep I think it might be beneficial to use the logic in the patch to set the write-only function attribute at the time attributes are added to a call/function. I am not sure how common this is (argmemonly + writeOnly/readOnly argument attributes), but that it was missing for an intrinsic like memset seems to indicate how easy things like that can be missed. Alternatively we could use the logic to warn/fail on missing attributes. WDYT?


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