[Bug tree-optimization/102809] New: Some TSVC benchmarks are slower after r12-4195-gec0124e0acb556cd

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102809

            Bug ID: 102809
           Summary: Some TSVC benchmarks are slower after
                    r12-4195-gec0124e0acb556cd
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
                CC: aldyh at gcc dot gnu.org
  Target Milestone: ---

Tested with https://github.com/UoB-HPC/TSVC_2/pull/2 where one can run a single
benchmark.

Happens with -Ofast -march=native on znver1 machine:

gcc-bisect.py 'gcc *.c -lm -Ofast -march=native -fuse-ld=bfd && timeout 100.7
./a.out va' -l -e r12-4194-g1f51e9af7b615838 -s r12-4195-gec0124e0acb556cd

Bisecting latest revisions
  ec0124e0acb556cd(05 Oct 2021 18:24)(aldyh@redhat.com): [took: 7.050s] result:
OK
Loop    Time(sec)       Checksum
   va        3.719      1.644725
  1f51e9af7b615838(05 Oct 2021 16:47)(jwakely@redhat.com): [took: 5.433s]
result: OK
Loop    Time(sec)       Checksum
   va        2.006      1.644725

and can be seen here:
https://lnt.opensuse.org/db_default/v4/CPP/graph?plot.0=14.920.0
https://lnt.opensuse.org/db_default/v4/CPP/graph?plot.0=14.887.0
https://lnt.opensuse.org/db_default/v4/CPP/graph?plot.0=14.943.0