Some more memory usage reductions in bitmaps

[Jan Hubicka]

Hi,
the bitmap statistic code shows few spots where rather large amount of memory
are allocated by not released early.  This patch hits two most common spots 
(expcept for new_insn_chain in reload.c I don't understand very well yet).
In the tree-out-of-ssa case the bitmap is most of time allocated even tought
the function returns early and don't need it.
In the tree-ssa-pre the bitmaps are kept on pass local obstack and even the
very temporary ones not freed.  While this seems rather safe, the bitmaps
grows almost to a gig on my favorite testcase before compilation aborts
on out-of-memory, so the change on two common spots makes the pass live
longer (before exhausting memory anyway)

Bootstrapped/regtested i686-linux, OK?

:ADDPATCH middle-end:
Honza

        * tree-outof-ssa.c (check_replaceable): Do not allocate def_vars
        bitmap when not needed.
        * tree-ssa-pre.c (bitmap_set_and, bitmap_set_and_compl): Free temporary
        bitmaps.
Index: tree-outof-ssa.c
===================================================================
-u -L tree-outof-ssa.c  (revision 115809) -L tree-outof-ssa.c   (working copy) 
.svn/text-base/tree-outof-ssa.c.svn-base tree-outof-ssa.c
--- tree-outof-ssa.c    (revision 115809)
+++ tree-outof-ssa.c    (working copy)
@@ -1556,7 +1556,7 @@ check_replaceable (temp_expr_table_p tab
   var_map map = tab->map;
   ssa_op_iter iter;
   tree call_expr;
-  bitmap def_vars = BITMAP_ALLOC (NULL), use_vars;
+  bitmap def_vars, use_vars;
 
   if (TREE_CODE (stmt) != MODIFY_EXPR)
     return false;
@@ -1588,6 +1588,7 @@ check_replaceable (temp_expr_table_p tab
 
   version = SSA_NAME_VERSION (def);
   basevar = SSA_NAME_VAR (def);
+  def_vars = BITMAP_ALLOC (NULL);
   bitmap_set_bit (def_vars, DECL_UID (basevar));
 
   /* Add this expression to the dependency list for each use partition.  */
Index: tree-ssa-pre.c
===================================================================
-u -L tree-ssa-pre.c    (revision 115809) -L tree-ssa-pre.c     (working copy) 
.svn/text-base/tree-ssa-pre.c.svn-base tree-ssa-pre.c
--- tree-ssa-pre.c      (revision 115809)
+++ tree-ssa-pre.c      (working copy)
@@ -624,7 +624,7 @@ bitmap_set_and (bitmap_set_t dest, bitma
       if (!bitmap_bit_p (dest->values, VALUE_HANDLE_ID (val)))
        bitmap_clear_bit (dest->expressions, i);
     }
-
+  BITMAP_FREE (temp);
 }
 
 /* Perform bitmapped value set operation DEST = DEST & ~ORIG.  */
@@ -645,6 +645,7 @@ bitmap_set_and_compl (bitmap_set_t dest,
       if (!bitmap_bit_p (dest->values, VALUE_HANDLE_ID (val)))
        bitmap_clear_bit (dest->expressions, i);
     }
+  BITMAP_FREE (temp);
 }
 
 /* Return true if the bitmap set SET is empty.  */