[PATCH] D102002: [PassManager] unify vector passes between regular and LTO pipelines

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D102002#2744200 <https://reviews.llvm.org/D102002#2744200>, @spatel wrote:

> In D102002#2742902 <https://reviews.llvm.org/D102002#2742902>, @dmgreen wrote:
>
>> Without a lot of evidence that this is better across a range of architectures, I would recommend trying to be conservative, taking things a step at a time.
>> We have one test where this patch would make it 88% worse. That might be a pathological case but no one is going to put up with on tenth of the speed :-)
>
> Agreed - I should try to move the LTO variations to be more like the regular pipeline in small steps. 
> I'm curious if we can already see the big slowdown when compiling with "-flto" then?



> Similarly for the rawspeed benchmark shown by @lebedev.ri - does the reduction in SLP vectorization show up when compiling with -flto independently of this patch?

Eh, i would love to tell :) As i've just discovered, apparently some weird miscompile was introduced post-clang-12,
so i can't run the benchmark. I guess i'll have to bisect it first.
I can not tell if it is in X86 backend, or in a middle-end opt passes.


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