[Bug tree-optimization/81945] New: [8 Regression] ICE in operator[], at vec.h:749

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81945

            Bug ID: 81945
           Summary: [8 Regression] ICE in operator[], at vec.h:749
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc-8.0.0-alpha20170820 snapshot (r251211) ICEs when compiling the following
snippet w/ -O3 (-Ofast) -ftree-parallelize-loops=2 -floop-nest-optimize:

unsigned long int cj;

void
at (int sa, int gb)
{
  long int *ne = &at;

  do
    {
      int **lm;

      while (gb != 0)
        {
        }
      cj *= 2;
      **lm = *ne;
      ++sa;
    }
  while (sa < 1);
}

% gcc-8.0.0-alpha20170820 -O3 -ftree-parallelize-loops=2 -floop-nest-optimize
-c -w mrglrqyu.c
during GIMPLE pass: vect
mrglrqyu.c: In function 'at._loopfn.1':
mrglrqyu.c:19:3: internal compiler error: in operator[], at vec.h:749
   while (sa < 1);
   ^

I wonder if this PR can be somehow related to the failures reported in PR80928
comment 5 and below.