[PATCH][RFC] Share variable annotations for globals across functions

[Richard Guenther]

This removes the per-function variable annotation code we use for
global variables.  A scheme like this is only needed if we have aliasing
computed for multiple functions at a time.  For which we better find
a different solution.  For PR36291 we have tons of referenced global
vars (the usual chaining of global data problem) and tons of functions.
This results in

tree-dfa.c:153 (create_var_ann) 482008296:30.4%    0: 0.0%  0: 0.0%  43818936:30.6%    5477367

and a peak memory usage of about 2GB on x86_64 (without checking but with
mem-stats enabled).  If we share the variable annotations of globals
this goes down to

tree-dfa.c:150 (create_var_ann)  206016: 0.0%   15094400: 3.2%  142592: 0.1%   0: 0.0%     241297

and a peak memory usage of about 1GB.

Bootstrapped and tested on x86_64-unknown-linux-gnu for C and C++
(I expect I can remove the tree-ssa-alias.c hunk), full testing will 
follow.

Diego, I suppose tuples doesn't change the above picture, so is the
general idea ok?

Thanks,
Richard.

2008-05-22  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/36291
	* tree-flow-inline.h (var_ann): Simplify.
	* tree-ssa-alias.c (compute_may_aliases): Clear alias info
	from var_anns of globals.
	* tree-dfa.c (create_var_ann): Simplify.
	(remove_referenced_var): Clear alias info from var_anns of globals.
	* tree-ssa.c (delete_tree_ssa): Likewise.

Index: tree-flow-inline.h
===================================================================
*** tree-flow-inline.h	(revision 135753)
--- tree-flow-inline.h	(working copy)
*************** var_ann (const_tree t)
*** 192,213 ****
  {
    var_ann_t ann;
  
!   if (!MTAG_P (t)
!       && (TREE_STATIC (t) || DECL_EXTERNAL (t)))
!     {
!       struct static_var_ann_d *sann
!         = ((struct static_var_ann_d *)
! 	   htab_find_with_hash (gimple_var_anns (cfun), t, DECL_UID (t)));
!       if (!sann)
! 	return NULL;
!       ann = &sann->ann;
!     }
!   else
!     {
!       if (!t->base.ann)
! 	return NULL;
!       ann = (var_ann_t) t->base.ann;
!     }
  
    gcc_assert (ann->common.type == VAR_ANN);
  
--- 192,200 ----
  {
    var_ann_t ann;
  
!   if (!t->base.ann)
!     return NULL;
!   ann = (var_ann_t) t->base.ann;
  
    gcc_assert (ann->common.type == VAR_ANN);
  
Index: tree-ssa-alias.c
===================================================================
*** tree-ssa-alias.c	(revision 135753)
--- tree-ssa-alias.c	(working copy)
*************** compute_may_aliases (void)
*** 1705,1710 ****
--- 1705,1726 ----
    
    memset (&alias_stats, 0, sizeof (alias_stats));
  
+   /* Clear var anns of globals.  */
+   if (!gimple_aliases_computed_p (cfun))
+     {
+       referenced_var_iterator rvi;
+       tree var;
+ 
+       FOR_EACH_REFERENCED_VAR  (var, rvi)
+ 	if (!MTAG_P (var)
+ 	    && (TREE_STATIC (var) || DECL_EXTERNAL (var)))
+ 	  {
+ 	    var_ann_t v_ann = var_ann (var);
+ 	    v_ann->mpt = NULL_TREE;
+ 	    v_ann->symbol_mem_tag = NULL_TREE;
+ 	  }
+     }
+ 
    /* Initialize aliasing information.  */
    ai = init_alias_info ();
  
Index: tree-dfa.c
===================================================================
--- tree-dfa.c	(revision 135713)
+++ tree-dfa.c	(working copy)
@@ -142,33 +142,14 @@ var_ann_t
 create_var_ann (tree t)
 {
   var_ann_t ann;
-  struct static_var_ann_d *sann = NULL;
 
   gcc_assert (t);
   gcc_assert (DECL_P (t));
   gcc_assert (!t->base.ann || t->base.ann->common.type == VAR_ANN);
 
-  if (!MTAG_P (t) && (TREE_STATIC (t) || DECL_EXTERNAL (t)))
-    {
-      sann = GGC_CNEW (struct static_var_ann_d);
-      ann = &sann->ann;
-    }
-  else
-    ann = GGC_CNEW (struct var_ann_d);
-
+  ann = GGC_CNEW (struct var_ann_d);
   ann->common.type = VAR_ANN;
-
-  if (!MTAG_P (t) && (TREE_STATIC (t) || DECL_EXTERNAL (t)))
-    {
-       void **slot;
-       sann->uid = DECL_UID (t);
-       slot = htab_find_slot_with_hash (gimple_var_anns (cfun),
-				        t, DECL_UID (t), INSERT);
-       gcc_assert (!*slot);
-       *slot = sann;
-    }
-  else
-    t->base.ann = (tree_ann_t) ann;
+  t->base.ann = (tree_ann_t) ann;
 
   return ann;
 }
@@ -765,8 +746,20 @@ remove_referenced_var (tree var)
 
   clear_call_clobbered (var);
   if ((v_ann = var_ann (var)))
-    ggc_free (v_ann);
-  var->base.ann = NULL;
+    {
+      /* Preserve var_anns of globals, but clear their alias info.  */
+      if (MTAG_P (var)
+	  || (!TREE_STATIC (var) && !DECL_EXTERNAL (var)))
+	{
+	  ggc_free (v_ann);
+	  var->base.ann = NULL;
+	}
+      else
+	{
+	  v_ann->mpt = NULL_TREE;
+	  v_ann->symbol_mem_tag = NULL_TREE;
+	}
+    }
   gcc_assert (DECL_P (var));
   in.uid = uid;
   loc = htab_find_slot_with_hash (gimple_referenced_vars (cfun), &in, uid,
Index: tree-ssa.c
===================================================================
*** tree-ssa.c	(revision 135753)
--- tree-ssa.c	(working copy)
*************** delete_tree_ssa (void)
*** 998,1006 ****
        set_phi_nodes (bb, NULL);
      }
  
!   /* Remove annotations from every referenced variable.  */
    FOR_EACH_REFERENCED_VAR (var, rvi)
      {
        if (var->base.ann)
          ggc_free (var->base.ann);
        var->base.ann = NULL;
--- 998,1013 ----
        set_phi_nodes (bb, NULL);
      }
  
!   /* Remove annotations from every referenced local variable.  */
    FOR_EACH_REFERENCED_VAR (var, rvi)
      {
+       if (!MTAG_P (var)
+ 	  && (TREE_STATIC (var) || DECL_EXTERNAL (var)))
+ 	{
+ 	  var_ann (var)->mpt = NULL_TREE;
+ 	  var_ann (var)->symbol_mem_tag = NULL_TREE;
+ 	  continue;
+ 	}
        if (var->base.ann)
          ggc_free (var->base.ann);
        var->base.ann = NULL;