[PATCH] D143631: [LTO] Don't let InstCombine re-sink the vastly more expensive fdiv

[David Sherwood via Phabricator via llvm-commits]

david-arm added a comment.

Hi @spatel @craig.topper, I did think about trying to change InstCombine to avoid sinking, but given resistance to this approach in the past I wasn't sure if this was the right approach. However, certainly it's unfortunate that we run InstCombine so many times in the LTO pipeline that we end up with this problem. I agree that adding another LICM pass at the end increases compilation time too, which isn't great. I think ultimately we have to decide between 1) increased compilation time without changing InstCombine, 2) reduce compilation time and increase performance by not sinking the fdiv in InstCombine. I'm not particularly attached to either approach, but I definitely do want to fix it. :)


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https://reviews.llvm.org/D143631