[PATCH] D101185: [LangRef] tbaa: type names can be used as hints to optimizations

[Jeroen Dobbelaere via Phabricator via llvm-commits]

jeroen.dobbelaere added a comment.

In D101185#2716977 <https://reviews.llvm.org/D101185#2716977>, @fhahn wrote:

> On a high level, encoding more Clang specifics into the `tbaa` spec and using it as heuristics seems a bit unfortunate to me, as it may pessimize frontends that for various reasons cannot use `tbaa`, especially because the additional information does not seem `tbaa` specific to me.
>
> I understand it is very convenient to use `tbaa` in this case, but I am worried about non-Clang frontends once this heuristic becomes important for performance. What will we suggest to frontends that want to opt-in to the optimizations (but `tbaa` in general is not suitable for them)?

We could introduce something like `!tb.struct` which point to the similar structured information as `!tbaa.struct`. When that is present, that information could also be used to expand `llvm.memcpy`, but without enforcing the type based aliasing implications.


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