[CFG] Loop unswitching patch

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello.

This patch enables removing of predictable paths for some more situations
(now that I've noticed that I must recount dominators the hard way anyway).

Zdenek

Changelog:
	* loop-new.c (try_remove_path): Modified.

Index: loop-new.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/loop-new.c,v
retrieving revision 1.1.2.6
diff -c -3 -p -r1.1.2.6 loop-new.c
*** loop-new.c	2002/02/28 22:38:50	1.1.2.6
--- loop-new.c	2002/02/28 23:13:45
*************** try_remove_path (loops, loop, e)
*** 741,770 ****
  {
    edge ae;
    basic_block *rem_bbs, *dom_bbs, from, *border_bbs;
!   int i, nrem, n_dom_bbs, n_border_bbs;
  
    /* First identify the branch.  */
    nrem = find_branch (e, loops->cfg.dom, loop, &rem_bbs);
  
!   /* Check whether we would not create unreachable blocks and whether
!      we would be able to recount dominators. Also remember border blocks.  */
!   border_bbs = xcalloc (n_basic_blocks, sizeof (basic_block));
!   n_border_bbs = 0;
    for (i = 0; i < nrem; i++)
!     for (ae = rem_bbs[i]->succ; ae; ae = ae->succ_next)
!       {
! 	basic_block dom_bb;
! 	if (flow_bb_inside_loop_p (loop, ae->dest))
! 	  continue;
! 	border_bbs[n_border_bbs++] = ae->dest;
! 	dom_bb = get_immediate_dominator (loops->cfg.dom, ae->dest);
! 	if (flow_bb_inside_loop_p (loop, dom_bb))
  	  {
  	    free (rem_bbs);
- 	    free (border_bbs);
  	    return 0;
  	  }
!       }
  
    /* OK. Remove the path.  */
    from = e->src;
--- 741,772 ----
  {
    edge ae;
    basic_block *rem_bbs, *dom_bbs, from, *border_bbs;
!   int i, j, nrem, n_dom_bbs, n_border_bbs;
  
    /* First identify the branch.  */
    nrem = find_branch (e, loops->cfg.dom, loop, &rem_bbs);
  
!   /* Check whether we would not create unreachable blocks.  */
    for (i = 0; i < nrem; i++)
!     {
!       n_dom_bbs = get_dominated_by (loops->cfg.dom, from, &dom_bbs);
!       for (j = 0; j < n_dom_bbs; j++)
!         if (!flow_bb_inside_loop_p (loop, dom_bbs[j]))
  	  {
+ 	    free (dom_bbs);
  	    free (rem_bbs);
  	    return 0;
  	  }
!       free (dom_bbs);
!     }
! 
!   /* Remember border blocks.  */
!   border_bbs = xcalloc (n_basic_blocks, sizeof (basic_block));
!   n_border_bbs = 0;
!   for (i = 0; i < nrem; i++)
!     for (ae = rem_bbs[i]->succ; ae; ae = ae->succ_next)
!       if (!flow_bb_inside_loop_p (loop, ae->dest))
! 	border_bbs[n_border_bbs++] = ae->dest;
  
    /* OK. Remove the path.  */
    from = e->src;