[Bug tree-optimization/98845] New: [8/9/10 Regression] ICE: SSA corruption (Unable to coalesce ssa_names 2 and 23 which are marked as MUST COALESCE.)

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98845

            Bug ID: 98845
           Summary: [8/9/10 Regression] ICE: SSA corruption (Unable to
                    coalesce ssa_names 2 and 23 which are marked as MUST
                    COALESCE.)
           Product: gcc
           Version: 11.0
            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-11.0.0-alpha20210124 snapshot (g:6b1633378b74bed1d999a0ae2549088515a30ba0)
ICEs when compiling the following testcase w/ -Os -fno-tree-dce:

int __attribute__ ((returns_twice))
func_58 (int);

int
func_215 (int func_215___trans_tmp_2, int g_180, int p_217, int p_218)
{
  if (func_215___trans_tmp_2)
    func_215 (0, 0, 0, 0);
  else if (g_180)
    {
      if (p_218)
        return 1;

      p_218 = p_217;
    }
  else
    {
      p_217 = 0;
      while (!p_217)
        {
        }
    }

  p_218 = 0;
  while (p_218)
    {
      func_58 (p_217);
      func_58 (p_217 + 1);
    }

  return 0;
}

% gcc-11.0.0 -Os -fno-tree-dce -c gdh96e2t.c

Unable to coalesce ssa_names 2 and 23 which are marked as MUST COALESCE.
p_217_2(ab) and  p_217_23(D)(ab)
during RTL pass: expand
gdh96e2t.c: In function 'func_215':
gdh96e2t.c:5:1: internal compiler error: SSA corruption
    5 | func_215 (int func_215___trans_tmp_2, int g_180, int p_217, int p_218)
      | ^~~~~~~~
0xf1d345 fail_abnormal_edge_coalesce
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/tree-ssa-coalesce.c:1003
0xf1d345 coalesce_partitions
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/tree-ssa-coalesce.c:1425
0xf1d345 coalesce_ssa_name(_var_map*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/tree-ssa-coalesce.c:1755
0xeb8fcc remove_ssa_form
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/tree-outof-ssa.c:1065
0xeb8fcc rewrite_out_of_ssa(ssaexpand*)
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/tree-outof-ssa.c:1323
0x961e60 execute
       
/var/tmp/portage/sys-devel/gcc-11.0.0_alpha20210124/work/gcc-11-20210124/gcc/cfgexpand.c:6533