[Bug tree-optimization/87342] New: [9 Regression] ICE: verify_ssa failed (error: definition in block 10 does not dominate use in block 8)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87342

            Bug ID: 87342
           Summary: [9 Regression] ICE: verify_ssa failed (error:
                    definition in block 10 does not dominate use in block
                    8)
           Product: gcc
           Version: 9.0
            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-9.0.0-alpha20180916 snapshot (r264351) ICEs when compiling the following
snippet w/ -O1 or -Og:

int ix;

void
o6 (int rh)
{
  if (rh == 0)
    {
      ix = 0;
      while (ix < 1)
        {
        }

      for (;;)
        if (ix == 0)
          while (rh < 1)
            {
              if (rh == 0)
                {
                  __builtin_unreachable ();

 kp:
                  if (ix == 0)
                    {
 hk:
                      ix = 0;
                    }
                }

              while (rh < 1)
                if (ix == 0)
                  goto kp;

              while (rh < 1)
                {
                }
            }
        else
          goto kp;
    }

  goto hk;
}

% gcc-9.0.0-alpha20180916 -O1 -c ifjkuamu.c
ifjkuamu.c: In function 'o6':
ifjkuamu.c:42:1: error: definition in block 10 does not dominate use in block 8
42 | }
   | ^
for SSA_NAME: ix.3_4 in statement:
if (ix.3_4 == 0)
during GIMPLE pass: fre
ifjkuamu.c:42:1: internal compiler error: verify_ssa failed
0xec982e verify_ssa(bool, bool)
       
/var/tmp/portage/sys-devel/gcc-9.0.0_alpha20180916/work/gcc-9-20180916/gcc/tree-ssa.c:1188
0xbe75ad execute_function_todo
       
/var/tmp/portage/sys-devel/gcc-9.0.0_alpha20180916/work/gcc-9-20180916/gcc/passes.c:1950
0xbe839e execute_todo
       
/var/tmp/portage/sys-devel/gcc-9.0.0_alpha20180916/work/gcc-9-20180916/gcc/passes.c:1997