[Bug tree-optimization/81418] New: [8 Regression] ICE in vect_get_vec_def_for_stmt_copy

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81418

            Bug ID: 81418
           Summary: [8 Regression] ICE in vect_get_vec_def_for_stmt_copy
           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-alpha20170709 ICEs when compiling the following snippet w/ -O1
-ftree-loop-vectorize:

int
ol (int ku)
{
  int zq = 0;

  while (ku < 1)
    {
      int y6;

      for (y6 = 0; y6 < 3; ++y6)
        zq += (char)ku;
      ++ku;
    }

  return zq;
}

% gcc-8.0.0-alpha20170709 -O1 -ftree-loop-vectorize -c -w mndyhqic.c
during GIMPLE pass: vect
mndyhqic.c: In function 'ol':
mndyhqic.c:2:1: internal compiler error: in vect_get_vec_def_for_stmt_copy, at
tree-vect-stmts.c:1522
 ol (int ku)
 ^~

(As a side note, when compiling this w/ -O2 or higher, -ftree-loop-vectorize
makes 8 branch generate something absolutely hilarious:
https://godbolt.org/g/R4YW3b).