[PATCH] D38566: [SimplifyCFG] don't sink common insts too soon (PR34603)

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D38566#889637, @hfinkel wrote:

> Thanks for the explanation. So, to be clear, we're only delaying the "sinking through PHIs" type of sinking until late?


Correct - everything is still here, but we're using the existing def of "late" to limit when it happens.

> I'm a bit concerned about the fact that LateSimplyCFG currently runs right after the SLP vectorizer, but we probably want to do select formation aggressively before the SLP vectorizer. We might, in fact, want to form selects more aggressively before the loop vectorizer too. In short, I'm not sure that this variety of "late" is the same as our existing concept of "late" (which is something that interferes with loop structure, and thus, should come after vectorization (at least loop vectorization)).

Ok - it sounds like I should proceed with using the optional bits within the pass manager(s). I'll make it so that we're only preventing the sinking on the first instantiation of simplifycfg (the one before early-cse).


https://reviews.llvm.org/D38566