https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102058
Bug ID: 102058
Summary: 450.soplex regressed on x86_64 with -Ofast
-march=generic (by 8-15%)
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
CC: rguenth at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
All three LNT x86_64 testers have experienced a regression when
running SPECFP 2006 benchmark 450.soplex compiled with -Ofast
-march=generic (as opposed to -march=native builds which seem not to
be affected).
A znver2 machine regressed by 15%:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=414.150.0&plot.1=300.150.0&;
A znver1 machine regressed by 8%:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=451.150.0&plot.1=27.150.0&;
An Intel Kabylake machine regressed by 9%:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=429.150.0&plot.1=25.150.0&;
I have bisected the regression (on another znver2 machine) to revision
r12-2733-g31855ba6b16:
31855ba6b16cd138d7484076a08cd40d609654b8 is the first bad commit
commit 31855ba6b16cd138d7484076a08cd40d609654b8
Author: Richard Biener <rguent...@suse.de>
Date: Thu Jul 29 14:14:48 2021 +0200
Add emulated gather capability to the vectorizer
This adds a gather vectorization capability to the vectorizer
without target support by decomposing the offset vector, doing
sclar loads and then building a vector from the result. This
is aimed mainly at cases where vectorizing the rest of the loop
offsets the cost of vectorizing the gather.
[...]
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)
