[Bug tree-optimization/126045] New: spaceship_replacement has some dead code in it dealing with COND_EXPR

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126045

            Bug ID: 126045
           Summary: spaceship_replacement has some dead code in it dealing
                    with COND_EXPR
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

```
      else if (gimple_assign_rhs_code (use_stmt) == COND_EXPR)
        {
          tree cond = gimple_assign_rhs1 (use_stmt);
          if (!COMPARISON_CLASS_P (cond))
            return false;
          cmp = TREE_CODE (cond);
          lhs = TREE_OPERAND (cond, 0);
          rhs = TREE_OPERAND (cond, 1);
        }
...

  else
    {
      tree cond = build2 (res_cmp, TREE_TYPE (gimple_assign_rhs1 (use_stmt)),
                          clhs1, crhs1);
      gimple_assign_set_rhs1 (use_stmt, cond);
    }
```

cond here is always SSA_NAME or a constant. So this code can be removed.

This has been dead since r13-707-g68e0063397ba82 when COND_EXPR no longer could
have a conditional in rhs1.