[Bug tree-optimization/115438] [15 Regression] 503.bwaves_r regressed 5-11% on different x86_64 machines at -Ofast -march=native since r15-1006-gd93353e6423eca

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115438

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I reproduced the larger regression with -march=zen3 on a zen4 machine.

   9.27%         94741  bwaves_r_peak.g  bwaves_r_peak.gcc7-m64  [.]
bi_cgstab_block_
   5.96%         60744  bwaves_r_base.g  bwaves_r_base.gcc7-m64  [.]
bi_cgstab_block_

in block_solver.F is the main regression.  There's no -fopt-info-vec
difference.

I think the difference is that with SLP we do not perform the
STMT_VINFO_FORCE_SINGLE_CYCLE transform.