[Bug tree-optimization/125917] New: Cleanup `gsi_afer_label, if(gsi_end) gsi_insert_after else gsi_insert_before` pattern

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125917

            Bug ID: 125917
           Summary: Cleanup `gsi_afer_label, if(gsi_end) gsi_insert_after
                    else gsi_insert_before` pattern
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

tree-ssa-phiopt.cc has the following code:
```
  gsi = gsi_after_labels (join_bb);
  if (gsi_end_p (gsi))
    {
      gsi = gsi_last_bb (join_bb);
      gsi_insert_after (&gsi, new_stmt, GSI_NEW_STMT);
    }
  else
    gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
```

But that can just be:
```
  gsi = gsi_after_labels (join_bb);
  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
```

This code dates from pre-tuples and looks like it was never cleaned up.