Save GGC garbage produced by gimplifier

[Jan Hubicka <jh at suse dot cz>]

Hi,
the memory usage of varrays increased dramatically since 3.4 accounting now
about 20% of memory overhead.  About 60% of it (at -O0) accounts to varray
"stack" used by gimplifier that needs not to live in ggc at all.

Bootstrapped/regtessed on i686-pc-gnu-linux.
I don't like the need to use GENERIC_PTR for trees.  An alternative is
to add explicit ggc_free to release the varray that looks slightly
inferrior because of the fragmentation, but if it is preffered, I can do
that too.

Honza

	* gimplify.c (gimplify_compound_lval): Move "stack" varray out of
	GGC.
Index: gimplify.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/gimplify.c,v
retrieving revision 1.1.2.141.2.9
diff -c -3 -p -r1.1.2.141.2.9 gimplify.c
*** gimplify.c	2 Aug 2004 23:11:48 -0000	1.1.2.141.2.9
--- gimplify.c	1 Sep 2004 19:59:58 -0000
*************** gimplify_compound_lval (tree *expr_p, tr
*** 1510,1517 ****
    int i;
  
    /* Create a stack of the subexpressions so later we can walk them in
!      order from inner to outer.  */
!   VARRAY_TREE_INIT (stack, 10, "stack");
  
    /* We can either handle REALPART_EXPR, IMAGEPART_EXPR anything that
       handled_components can deal with.  */
--- 1510,1520 ----
    int i;
  
    /* Create a stack of the subexpressions so later we can walk them in
!      order from inner to outer.  
! 
!      This array is very memory consuming.  Don't even think of making
!      it VARRAY_TREE.  */
!   VARRAY_GENERIC_PTR_NOGC_INIT (stack, 10, "stack");
  
    /* We can either handle REALPART_EXPR, IMAGEPART_EXPR anything that
       handled_components can deal with.  */
*************** gimplify_compound_lval (tree *expr_p, tr
*** 1519,1525 ****
         (handled_component_p (*p)
  	|| TREE_CODE (*p) == REALPART_EXPR || TREE_CODE (*p) == IMAGPART_EXPR);
         p = &TREE_OPERAND (*p, 0))
!     VARRAY_PUSH_TREE (stack, *p);
  
  #if defined ENABLE_CHECKING
    if (VARRAY_ACTIVE_SIZE (stack) == 0)
--- 1522,1528 ----
         (handled_component_p (*p)
  	|| TREE_CODE (*p) == REALPART_EXPR || TREE_CODE (*p) == IMAGPART_EXPR);
         p = &TREE_OPERAND (*p, 0))
!     VARRAY_PUSH_GENERIC_PTR_NOGC (stack, *p);
  
  #if defined ENABLE_CHECKING
    if (VARRAY_ACTIVE_SIZE (stack) == 0)
*************** gimplify_compound_lval (tree *expr_p, tr
*** 1540,1546 ****
       then we gimplify any indices, from left to right.  */
    for (i = VARRAY_ACTIVE_SIZE (stack) - 1; i >= 0; i--)
      {
!       tree t = VARRAY_TREE (stack, i);
  
        if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
  	{
--- 1543,1549 ----
       then we gimplify any indices, from left to right.  */
    for (i = VARRAY_ACTIVE_SIZE (stack) - 1; i >= 0; i--)
      {
!       tree t = VARRAY_GENERIC_PTR_NOGC (stack, i);
  
        if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
  	{
*************** gimplify_compound_lval (tree *expr_p, tr
*** 1659,1664 ****
--- 1662,1669 ----
        ret = MIN (ret, GS_OK);
      }
  
+   VARRAY_FREE (stack);
+ 
    return ret;
  }