[Bug rtl-optimization/124497] New: delete_unreachable_blocks vs cleanup_cfg after purge_all_dead_edges call

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124497

            Bug ID: 124497
           Summary: delete_unreachable_blocks vs cleanup_cfg after
                    purge_all_dead_edges call
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

So some places uses delete_unreachable_blocks while others cleanup_cfg after
the call to purge_all_dead_edges even in the same file/function.
dse.cc for an example:
```
  /* DSE can eliminate potentially-trapping MEMs.
     Remove any EH edges associated with them, since otherwise
     DF_LR_RUN_DCE will complain later.  */
  if ((locally_deleted || globally_deleted)
      && cfun->can_throw_non_call_exceptions
      && purge_all_dead_edges ())
    {
      free_dominance_info (CDI_DOMINATORS);
      delete_unreachable_blocks ();
    }

...
  /* DSE can eliminate potentially-trapping MEMs.
     Remove any EH edges associated with them.  */
  if ((locally_deleted || globally_deleted)
      && cfun->can_throw_non_call_exceptions
      && purge_all_dead_edges ())
    {
      free_dominance_info (CDI_DOMINATORS);
      cleanup_cfg (0);
    }
```

ira.cc has:
```
      if (purge_all_dead_edges ())
        delete_unreachable_blocks ();
```

While postreload.cc has:
```
  /* Reload_cse_regs can eliminate potentially-trapping MEMs.
     Remove any EH edges associated with them.  */
  if (fun->can_throw_non_call_exceptions
      && purge_all_dead_edges ())
    cleanup_cfg (0);
```

Note in the case of the ira.cc change, it is done after doing indirect to
direct jumps.