[PATCH] D58147: [CodeGen] Fix calling llvm.var.annotation outside of a basic block.

Volodymyr Sapsai via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Feb 26 15:52:19 PST 2019

vsapsai added a comment.

In D58147#1398094 <https://reviews.llvm.org/D58147#1398094>, @rjmccall wrote:

> Okay.  Is it acceptable for the annotation to simply disappear in this case?  I don't really understand the purposes of annotations well enough to judge.

Looks like it is acceptable. The main justification for this behavior is that it is already happening for

  int after_return = __builtin_annotation(0, "annotation");

so I think it is correct to have the same IR for

  int after_return __attribute__((annotate("annotation"))) = 0;

Also looks like in the code we don't really use this intrinsic. And according to the documentation

> This intrinsic allows annotation of local variables with arbitrary
>  strings. This can be useful for special purpose optimizations that want
>  to look for these annotations. These have no other defined use; they are
>  ignored by code generation and optimization.

I think for the special purpose optimizations it would be more convenient not to know about the code after return instead of detecting it and ignoring explicitly.



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