[PATCH] D71539: [SCEV] Look through trivial PHIs.

Wed Aug 12 04:23:25 PDT 2020

fhahn added a comment.

In D71539#2212760 <https://reviews.llvm.org/D71539#2212760>, @xbolva00 wrote:

> https://llvm-compile-time-tracker.com/compare.php?from=9ceb192e14164ecf8a6f714a770c89765327c722&to=e441b7a7a0a72c28daf5a8e594559c667e5b4534&stat=instructions
>
> @fhahn, Can you look at mafft? Seems like 2-3 % compile time regression? Any data about runtime perf? It is better now?

Yes it seems like we hit the worst case here. By looking through phis we have to spend more time making sure LCSSA form is preserved during expansion. This causes some passes that use the expander to take significantly longer than previously. I'll revert shortly and see how we can avoid most of the extra work.

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https://reviews.llvm.org/D71539