[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.

In D84108#2227709 <https://reviews.llvm.org/D84108#2227709>, @dmgreen wrote:

> We saw performance improvements from this patch. They were a little bit up-and-down, but definitely an improvement overall.

Right. I think you're still in scientific computing yes? The internal and external benchmarks are fairly straightforward scalar code. I.e. if they were vectorizable we'd probably have done so ages ago for the internal and the external are things like bytecode interpreters etc. So the patch is penalizing things that just aren't vectorizable for things that might be - and I'm not sure that's the right tradeoff to make here. Let's start an llvm-dev discussion and bring in a few more people as well. I'd be very interested in Kit's perspective here too.


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