c/7344: performance regression on huge case statements

[Jan Hubicka]

Hi,
this second patch makes CFG construction to take 0.88 second instead of
29 seconds it did originally.

Honza

Fri Oct 11 16:50:55 CEST 2002  Jan Hubicka  <jh@suse.cz>
	* cfgbuild.c (make_edges): Create edge cache when we do have
	large jumptable.
	(do_tablejump): Note size of maximal jumptable.
	* function.c (prepare_function_start): Zero out size.
	* function.h (function): Add max_jumptable_ents.
Index: cfgbuild.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cfgbuild.c,v
retrieving revision 1.27
diff -c -3 -p -r1.27 cfgbuild.c
*** cfgbuild.c	5 Aug 2002 18:46:32 -0000	1.27
--- cfgbuild.c	11 Oct 2002 14:49:54 -0000
*************** make_edges (label_value_list, min, max, 
*** 292,298 ****
    /* Heavy use of computed goto in machine-generated code can lead to
       nearly fully-connected CFGs.  In that case we spend a significant
       amount of time searching the edge lists for duplicates.  */
!   if (forced_labels || label_value_list)
      {
        edge_cache = sbitmap_vector_alloc (last_basic_block, last_basic_block);
        sbitmap_vector_zero (edge_cache, last_basic_block);
--- 292,298 ----
    /* Heavy use of computed goto in machine-generated code can lead to
       nearly fully-connected CFGs.  In that case we spend a significant
       amount of time searching the edge lists for duplicates.  */
!   if (forced_labels || label_value_list || cfun->max_jumptable_ents > 100)
      {
        edge_cache = sbitmap_vector_alloc (last_basic_block, last_basic_block);
        sbitmap_vector_zero (edge_cache, last_basic_block);
Index: expr.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/expr.c,v
retrieving revision 1.486
diff -c -3 -p -r1.486 expr.c
*** expr.c	7 Oct 2002 07:37:09 -0000	1.486
--- expr.c	11 Oct 2002 14:49:57 -0000
*************** do_tablejump (index, mode, range, table_
*** 10941,10946 ****
--- 10930,10938 ----
       enum machine_mode mode;
  {
    rtx temp, vector;
+ 
+   if (range > cfun->max_jumptable_ents)
+     cfun->max_jumptable_ents = range;
  
    /* Do an unsigned comparison (in the proper mode) between the index
       expression and the value which represents the length of the range.
Index: function.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/function.c,v
retrieving revision 1.385
diff -c -3 -p -r1.385 function.c
*** function.c	11 Oct 2002 01:28:24 -0000	1.385
--- function.c	11 Oct 2002 14:49:59 -0000
*************** prepare_function_start ()
*** 6295,6300 ****
--- 6295,6302 ----
  
    cfun->function_frequency = FUNCTION_FREQUENCY_NORMAL;
  
+   cfun->max_jumptable_ents = 0;
+ 
    (*lang_hooks.function.init) (cfun);
    if (init_machine_status)
      cfun->machine = (*init_machine_status) ();
Index: function.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/function.h,v
retrieving revision 1.88
diff -c -3 -p -r1.88 function.h
*** function.h	22 Sep 2002 14:09:33 -0000	1.88
--- function.h	11 Oct 2002 14:49:59 -0000
*************** struct function GTY(())
*** 500,505 ****
--- 500,509 ----
         (set only when profile feedback is available).  */
      FUNCTION_FREQUENCY_HOT
    } function_frequency;
+ 
+   /* Maximal number of entities in the single jumptable.  Used to estimate
+      final flowgraph size.  */
+   int max_jumptable_ents;
  };
  
  /* The function currently being compiled.  */