[PATCH] D109368: [LV] Don't vectorize if we can prove RT + vector cost >= scalar cost.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

In D109368#3144716 <https://reviews.llvm.org/D109368#3144716>, @fhahn wrote:

> In D109368#3099132 <https://reviews.llvm.org/D109368#3099132>, @fhahn wrote:
>
>> 
>
> I also collected a first set of numbers for AArch64 with -O3 for Geekbench and SPEC2017. So far it looks like there is only one notable change: 544.nab_r regressed by 18%. So overall not too bad, but this one needs investigating. If anybody would be able to collect numbers for other platforms/benchmarks, that would also be extremely helpful.

I think I tracked down the remaining regression to the SCEVExpander creating very bad code when expanding SCEV predicates for certain cases (like @dmgreen mentioned earlier). I'll put up a few small patches for SCEVExpander to improve things starting with D116696 <https://reviews.llvm.org/D116696>. After that, I think the patch should be good to go both in terms of compile-time and runtime perf.


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