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

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

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)?



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Comment at: llvm/docs/LangRef.rst:5811
+example, ``"any pointer"`` and ``"vtable pointer"`` might be recognized and
+used to select a different, but equivalent, code generation.
 
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I think from that formulation it is still not clear *what* kind of meaning is assigned to those special strings. 

Unless I am missing something, it is still not clear *where*  and *how* frontends should use/emit those special names. I think it would be good if the description would be clear on how new frontends should use the special names.


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  https://reviews.llvm.org/D101185/new/

https://reviews.llvm.org/D101185