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

[Hal Finkel via Phabricator via llvm-commits]

hfinkel added a comment.

In https://reviews.llvm.org/D38566#910739, @spatel wrote:

> Patch updated:
>  Now that we have SimplifyCFGOptions exposed to the pass managers, we can use a precise disablement of sinking common instructions to only the first instantiation of -simplifycfg (the one that runs before early-cse).


Why? The selects also hurt GVN, etc. I thought we were going to delay this until the end of the canonicalization phase. Only then might be have more "phases" in this sense.

> Depending on your perspective, this is either a redefinition of "canonical form" or we've created a new "pre-canonical form".
> 
> Given the comments in PR34603, I suspect we want to limit simplifycfg sinking even more, but that should be a follow-up patch with more phase ordering tests, so we know exactly what kind of patterns we're affecting.




https://reviews.llvm.org/D38566