[PATCH] D153453: [MemCpyOpt] implement single BB stack-move optimization which unify the static unescaped allocas

Fri Jul 14 05:29:06 PDT 2023

nikic added a comment.

In D153453#4500558 <https://reviews.llvm.org/D153453#4500558>, @serge-sans-paille wrote:

> In D153453#4500396 <https://reviews.llvm.org/D153453#4500396>, @nikic wrote:
>
>> We shouldn't use dominates() in this patch, as it's not always semantically correct.
>
> Can you explain why?

A lot of these comesBefore() are actually reachability queries. This reduces to comesBefore() within one block, but is not the same as dominates() across blocks.

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https://reviews.llvm.org/D153453