[patch] for PR 23475

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

Hello,

this patch implements updating of frequencies after empty loop removal,
which is currently missing.  Bootstrapped & regtested on i686.

Zdenek

	PR tree-optimization/23475
	* tree-ssa-loop-ivcanon.c (remove_empty_loop): Update frequencies
	and counts.

Index: tree-ssa-loop-ivcanon.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-loop-ivcanon.c,v
retrieving revision 2.20
diff -c -3 -p -r2.20 tree-ssa-loop-ivcanon.c
*** tree-ssa-loop-ivcanon.c	13 Aug 2005 17:28:40 -0000	2.20
--- tree-ssa-loop-ivcanon.c	27 Aug 2005 08:03:18 -0000
*************** empty_loop_p (struct loop *loop)
*** 491,499 ****
  static void
  remove_empty_loop (struct loop *loop)
  {
!   edge exit = single_dom_exit (loop);
    tree cond_stmt = last_stmt (exit->src);
    tree do_exit;
  
    if (exit->flags & EDGE_TRUE_VALUE)
      do_exit = boolean_true_node;
--- 491,506 ----
  static void
  remove_empty_loop (struct loop *loop)
  {
!   edge exit = single_dom_exit (loop), non_exit;
    tree cond_stmt = last_stmt (exit->src);
    tree do_exit;
+   basic_block *body;
+   unsigned n_before, freq_in, freq_h;
+   gcov_type exit_count = exit->count;
+ 
+   non_exit = EDGE_SUCC (exit->src, 0);
+   if (non_exit == exit)
+     non_exit = EDGE_SUCC (exit->src, 1);
  
    if (exit->flags & EDGE_TRUE_VALUE)
      do_exit = boolean_true_node;
*************** remove_empty_loop (struct loop *loop)
*** 502,507 ****
--- 509,542 ----
  
    COND_EXPR_COND (cond_stmt) = do_exit;
    update_stmt (cond_stmt);
+ 
+   /* Let us set the probabilities of the edges coming from the exit block.  */
+   exit->probability = REG_BR_PROB_BASE;
+   non_exit->probability = 0;
+   non_exit->count = 0;
+ 
+   /* Update frequencies and counts.  Everything before
+      the exit needs to be scaled FREQ_H/FREQ_IN times,
+      where FREQ_IN is the frequency of the entry edge
+      and FREQ_H is the frequency of the loop header.
+      Everything after the exit has zero frequency.  */
+   freq_h = loop->header->frequency;
+   freq_in = EDGE_FREQUENCY (loop_preheader_edge (loop));
+   if (freq_h != 0)
+     {
+       body = get_loop_body_in_dom_order (loop);
+       for (n_before = 1; n_before <= loop->num_nodes; n_before++)
+ 	if (body[n_before - 1] == exit->src)
+ 	  break;
+       scale_bbs_frequencies_int (body, n_before, freq_in, freq_h);
+       scale_bbs_frequencies_int (body + n_before, loop->num_nodes - n_before,
+ 				 0, 1);
+       free (body);
+     }
+ 
+   /* Number of executions of exit is not changed, thus we need to restore
+      the original value.  */
+   exit->count = exit_count;
  }
  
  /* Removes LOOP if it is empty.  Returns true if LOOP is removed.  CHANGED