https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113833
Bug ID: 113833
Summary: 435.gromacs fails verification on with -Ofast
-march={cascadelake,icelake-server} and PGO after
r14-7272-g57f611604e8bab
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
CC: fxue at os dot amperecomputing.com
Blocks: 26163
Target Milestone: ---
Host: x86_64-linux
Target: x86_64-linux
After r14-7272-g57f611604e8bab (Feng Xue: Do not count unused scalar
use when marking STMT_VINFO_LIVE_P [PR113091]), our runs of SPEC 2006
CPU benchmark 435.gromacs on Icelake-server CPU compiled with -Ofast
-march=native and PGO (with and without LTO) started failing with
miscompare error:
0002: 3.07684e+02
3.03476e+02
^
I subsequently verified the failure on an Intel CascadeLake and
bisected it to the aforementioned commit. We don't see it on our AMD
or Ampere testers (using -march=native).
I guess the miscomparison error may be well within what is expected
when using -Ofast but even in that case it would be nice to have it
documented here that that is indeed expected.
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)
