[Bug tree-optimization/81303] New: [8 Regression] 410.bwaves regression caused by r249919

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81303

            Bug ID: 81303
           Summary: [8 Regression] 410.bwaves regression caused by r249919
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

I see on Haswell with -march=native -Ofast a runtime increase from 177s to
254s.
This is caused by us vectorizing the innermost reduction loop in
block_solver.f:mat_times_vec using strided loads (and with -mprefer-avx128 even
peeling for alignment).