[Bug tree-optimization/70623] New: [6 Regression] ICE in compute_antic at -O2

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70623

            Bug ID: 70623
           Summary: [6 Regression] ICE in compute_antic at -O2
           Product: gcc
           Version: 6.0
            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-6.0.0-alpha20160403 and gcc-6.0.0-alpha20160410 snippets ICE when compiling
the following reduced snippet at -O2:

int nm;
int *av;

void
h9(void)
{
  for (;;) {
    int wk, rc;
    int **ptr_10 = &av;
    if (*av != 0) {
    }
u4:
    wk = 0;
    for (rc = 0; rc < 3; ++rc) {
      int bc = (rc ? rc : nm);
      int ud = bc ? (*av ? 0 : rc) : 1;
      if (ud != 0) {
        if (*av != 0)
          goto u4;
        for (;;) {
        }
      }
    }
    while (wk < 3) {
      av = **ptr_10;
      ++wk;
    }
  }
}

% gcc-6.0.0-alpha20160410 -c -O2 oqqpkhyr.c           
oqqpkhyr.c: In function 'h9':
oqqpkhyr.c:25:10: warning: assignment makes pointer from integer without a cast
[-Wint-conversion]
       av = **ptr_10;
          ^
oqqpkhyr.c:5:1: internal compiler error: in compute_antic, at
tree-ssa-pre.c:2403
 h9(void)
 ^~

gcc-6.0.0-alpha20160110 doesn't ICE for me.