[PATCH] Allow different vector types for stmt groups

[Michael Matz]

Hello,

On Thu, 14 Oct 2021, Richard Biener via Gcc-patches wrote:

> > I have bisected an AMD zen2 10% performance regression of SPEC 2006 FP
> > 433.milc bechmark when compiled with -Ofast -march=native -flto to this
> > commit.  See also:
> > 
> >   https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=412.70.0&plot.1=289.70.0&
> > 
> > I am not sure if a bugzilla bug is in order because I cannot reproduce
> > the regression neither on an AMD zen3 machine nor on Intel CascadeLake,
> 
> It's for sure worth a PR for tracking purposes.  But I've not been
> very successful in identifying regression causes on Zen2 - what perf
> points to is usually exactly the same assembly in both base and peak :/

Well, in this case it's at least a fairly impressive (40%) difference in 
samples for add_force_to_mom* :

> > BEFORE:
> >     18.47%        105497  milc_peak.mine-  milc_peak.mine-lto-nat  [.] add_force_to_mom
> > 
> > AFTER:
> >     24.04%        149010  milc_peak.mine-  milc_peak.mine-lto-nat  [.] add_force_to_mom

(as the change was in the vectorizer this shouldn't be different inlining 
decisions hopefully).


Ciao,
Michael.