[PATCH] D84108: [SimplifyCFG][LoopRotate] SimplifyCFG: disable common instruction hoisting by default, enable late in pipeline

[Eric Christopher via Phabricator via llvm-commits]

echristo added a comment.

So, we're seeing several significant (20-30%) regressions due to this in various different library benchmarks. Usually around things that are compression/decompression loops, but also other places.

I'm uncertain what we can do, but I think this might need a wider range of discussion rather than the phabricator review.

Would you mind terribly reverting and starting a thread on llvm-dev about this? I think that'll give us an opportunity to weigh some of the tradeoffs in a wider space.

-eric


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https://reviews.llvm.org/D84108