[patch] stmt.c: Speed/clean up expand_case.

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi,

Attached is a patch to speed/clean up expand_case.

Now that we gimplify a switch statment,

1. we always have exactly one default label, and

2. the default label is at the end of TREE_VEC of CASE_LABEL_EXPRs.

By using the above facts, we can speed/clean up expand_case a little
bit.  Specifically, we can take care of the default label outside the
for loop in the second hunk of the patch.  In addition, we don't have
to worry about a missing default label (see the third hunk).

Taking an "if" outside of a "for" loop is a good thing.

Tested on i686-pc-linux-gnu.  OK to apply?

Kazu Hirata

2004-10-23  Kazu Hirata  <kazu@cs.umass.edu>

	* stmt.c (expand_case): Handle the default label outside of
	the for loop.  Remove code to handle a missing default label.

Index: stmt.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/stmt.c,v
retrieving revision 1.401
diff -c -p -r1.401 stmt.c
*** stmt.c	22 Oct 2004 18:52:19 -0000	1.401
--- stmt.c	23 Oct 2004 01:22:03 -0000
*************** expand_case (tree exp)
*** 2341,2347 ****
    struct case_node *case_list = 0;
  
    /* Label to jump to if no case matches.  */
!   tree default_label_decl = 0;
  
    /* The switch body is lowered in gimplify.c, we should never have
       switches with a non-NULL SWITCH_BODY here.  */
--- 2341,2347 ----
    struct case_node *case_list = 0;
  
    /* Label to jump to if no case matches.  */
!   tree default_label_decl;
  
    /* The switch body is lowered in gimplify.c, we should never have
       switches with a non-NULL SWITCH_BODY here.  */
*************** expand_case (tree exp)
*** 2353,2372 ****
    /* An ERROR_MARK occurs for various reasons including invalid data type.  */
    if (index_type != error_mark_node)
      {
!       for (i = TREE_VEC_LENGTH (vec); --i >= 0; )
! 	{
! 	  tree elt = TREE_VEC_ELT (vec, i);
  
! 	  /* Handle default labels specially.  */
! 	  if (!CASE_HIGH (elt) && !CASE_LOW (elt))
! 	    {
! 	      gcc_assert (!default_label_decl);
! 	      default_label_decl = CASE_LABEL (elt);
! 	    }
! 	  else
! 	    case_list = add_case_node (case_list, index_type,
! 				       CASE_LOW (elt), CASE_HIGH (elt),
! 				       CASE_LABEL (elt));
  	}
  
  
--- 2353,2373 ----
    /* An ERROR_MARK occurs for various reasons including invalid data type.  */
    if (index_type != error_mark_node)
      {
!       tree elt;
  
!       /* The default case is at the end of TREE_VEC.  */
!       elt = TREE_VEC_ELT (vec, TREE_VEC_LENGTH (vec) - 1);
!       gcc_assert (!CASE_HIGH (elt));
!       gcc_assert (!CASE_LOW (elt));
!       default_label_decl = CASE_LABEL (elt);
! 
!       for (i = TREE_VEC_LENGTH (vec) - 1; --i >= 0; )
! 	{
! 	  elt = TREE_VEC_ELT (vec, i);
! 	  gcc_assert (CASE_LOW (elt));
! 	  case_list = add_case_node (case_list, index_type,
! 				     CASE_LOW (elt), CASE_HIGH (elt),
! 				     CASE_LABEL (elt));
  	}
  
  
*************** expand_case (tree exp)
*** 2379,2392 ****
  	  start = get_last_insn ();
  	}
  
-       /* If we don't have a default-label, create one here,
- 	 after the body of the switch.  */
-       if (default_label_decl == 0)
- 	{
- 	  default_label_decl
- 	    = build_decl (LABEL_DECL, NULL_TREE, NULL_TREE);
- 	  expand_label (default_label_decl);
- 	}
        default_label = label_rtx (default_label_decl);
  
        before_case = get_last_insn ();
--- 2380,2385 ----