[Bug debug/70935] New: [6/7 Regression] ICE: verify_ssa failed (error: definition in block 9 does not dominate use in block 12) w/ -O3 -g

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70935

            Bug ID: 70935
           Summary: [6/7 Regression] ICE: verify_ssa failed (error:
                    definition in block 9 does not dominate use in block
                    12) w/ -O3 -g
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

gcc 6 and 7 ICE when compiling the following reduced snippet at -O3 (or -Ofast)
w/ -g:

int d0, sj, v0, rp, zi;

void
zn(void)
{
  if (v0 != 0)
    {
      int *js, *r3;
      int pm, gc;

      for (gc = 0; gc < 1; ++gc)
        {
          sj = 1;
          while (sj != 0)
            ;
        }
      r3 = &pm;
      *js = &gc;
ka:
      for (d0 = 0; d0 < 2; ++d0)
        {
          d0 = zi;
          if (zi)
            for (pm = 2; pm != 0; --pm)
              ;
        }
      while (*r3 != 0)
        {
          while (pm)
            ;
          ++r3;
        }
    }
  rp = 0;
  goto ka;
}

% gcc-7.0.0-alpha20160501 -c -O3 -g fngq6pkt.c 
fngq6pkt.c: In function 'zn':
fngq6pkt.c:18:11: warning: assignment makes integer from pointer without a cast
[-Wint-conversion]
       *js = &gc;
           ^
fngq6pkt.c:4:1: error: definition in block 9 does not dominate use in block 12
 zn(void)
 ^~
for SSA_NAME: pm.7_34 in statement:
# DEBUG pm => pm.7_34
fngq6pkt.c:4:1: internal compiler error: verify_ssa failed