[Bug c/80775] New: -O3 produces ice in group_case_labels_stmt

["dcb314 at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80775

            Bug ID: 80775
           Summary: -O3 produces ice in group_case_labels_stmt
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

Created attachment 41362
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41362&action=edit
C source code

The attached code and flag -O3 does this with recent trunk:

XmL.c:599:1: internal compiler error: Segmentation fault
0xc3ddcf crash_signal
        ../../trunk/gcc/toplev.c:337
0xc810ac group_case_labels_stmt(gswitch*)
        ../../trunk/gcc/tree-cfg.c:1684
0xc81b5a group_case_labels()
        ../../trunk/gcc/tree-cfg.c:1755
0xc8f766 execute_cleanup_cfg_post_optimizing
        ../../trunk/gcc/tree-cfgcleanup.c:1203

I'll have a go at reducing the code and providing a range of
revisions where I think the gcc bug is.