[Bug tree-optimization/84419] New: [8 Regression] SPEC CPU2017/CPU2006 521/621, 527/627, 554/654, 445, 454, 481, 416 runfails after r256628 with march=skylake-avx512

[alexander.nesterovskiy at intel dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84419

            Bug ID: 84419
           Summary: [8 Regression] SPEC CPU2017/CPU2006 521/621, 527/627,
                    554/654, 445, 454, 481, 416 runfails after r256628
                    with march=skylake-avx512
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alexander.nesterovskiy at intel dot com
  Target Milestone: ---

There are runfails for the following benchmarks since r256628:
SPEC2017 fp-rate/fp-speed:
 521/621
 527/627
 554/654
SPEC2006 int-speed:
 445
SPEC2006 fp-rate/fp-speed:
 454
 481
 416

Minimal optset to reproduce is "-O3 -march=skylake-avx512".

Reverting changes in tree-ssa-loop-ivopts.c fixes the problem in current
revisions (r257682 at least).