[Bug middle-end/122594] New: gsi_split_seq_before is broken for singletons

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122594

            Bug ID: 122594
           Summary: gsi_split_seq_before is broken for singletons
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

If you feed gsi_split_seq_before an iterator pointing to the last and only stmt
in a sequence you get a non-empty head sequence plus a non-end updated
iterator.
The expected result is an empty head sequence.

g++.dg/torture/pr122589.C loops forever if you remove the
gimple_seq_singleton_p
check from gsi_replace_with_seq.