ifcvt.c question

[Steven Bosscher <stevenb@suse.de>]

Hi,

ifcvt.c has this code in find_if_block():

  2718    /* If the THEN block has no successors, conditional execution can still
  2719       make a conditional call.  Don't do this unless the ELSE block has
  2720       only one incoming edge -- the CFG manipulation is too ugly otherwise.
  2721       Check for the last insn of the THEN block being an indirect jump, which
  2722       is listed as not having any successors, but confuses the rest of the CE
  2723       code processing.  ??? we should fix this in the future.  */
  2724    if (EDGE_COUNT (then_bb->succs) == 0)
  2725      {
  2726        if (single_pred_p (else_bb))
  2727          {
  2728            rtx last_insn = BB_END (then_bb);
  2729
  2730            while (last_insn
  2731                   && NOTE_P (last_insn)
  2732                   && last_insn != BB_HEAD (then_bb))
  2733              last_insn = PREV_INSN (last_insn);
  2734
  2735            if (last_insn
  2736                && JUMP_P (last_insn)
  2737                && ! simplejump_p (last_insn))
  2738              return FALSE;
  2739
  2740            join_bb = else_bb;
  2741            else_bb = NULL_BLOCK;
  2742          }
  2743        else
  2744          return FALSE;
  2745      }
  2746

I don't understand what lines 2728 to 2741 are for.  Could someone give
an example of when we can have a then_bb that has no successors, but
still ends in something that satisfies simplejump_p()?  What kind of
strange indirect jump would that be?  And shouldn't the check just use
computed_jump_p() if that is what it is looking for??

Gr.
Steven