[Bug tree-optimization/83887] New: [8 Regression] [graphite] ICE in verify_dominators, at dominance.c:1184 (error: dominator of 3 should be 21, not 18)

[asolokha at gmx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83887

            Bug ID: 83887
           Summary: [8 Regression] [graphite] ICE in verify_dominators, at
                    dominance.c:1184 (error: dominator of 3 should be 21,
                    not 18)
           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-alpha20180114 snapshot (r256677) ICEs when compiling the following
snippet w/ -O1 (-O2, -O3, -Ofast) -floop-nest-optimize -fno-tree-loop-im:

int z4, g7;

void
x3 (int my)
{
  while (my < 2)
    {
      for (z4 = 0; z4 < 2; ++z4)
        {
        }

      if (my != 0)
        for (g7 = 0; g7 < 2; ++g7)
          {
          }

      ++my;
    }
}

% gcc-8.0.0-alpha20180114 -O1 -floop-nest-optimize -fno-tree-loop-im -c
oiutipaf.c 
oiutipaf.c: In function 'x3':
oiutipaf.c:4:1: error: dominator of 3 should be 21, not 18
 x3 (int my)
 ^~
during GIMPLE pass: graphite
oiutipaf.c:4:1: internal compiler error: in verify_dominators, at
dominance.c:1184
0x5dbe5d verify_dominators(cdi_direction)
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/dominance.c:1184
0x8f5495 checking_verify_dominators
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/dominance.h:76
0x8f5495 calculate_dominance_info(cdi_direction)
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/dominance.c:746
0xd231b6 update_ssa(unsigned int)
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/tree-into-ssa.c:3332
0x1445a70 graphite_transform_loops()
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/graphite.c:425
0x1446e10 graphite_transforms
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/graphite.c:475
0x1446e10 execute
       
/var/tmp/portage/sys-devel/gcc-8.0.0_alpha20180114/work/gcc-8-20180114/gcc/graphite.c:552