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)

Reply via email to