[PATCH 04/18] remove TREE_CHAIN from SSA_NAME nodes

[Nathan Froyd <froydnj@codesourcery.com>]

This conversion is straightforward.  The tricky part is converting
FREE_SSANAMES into a VEC to eliminate the only use of TREE_CHAIN on
SSA_NAMEs.

-Nathan

gcc/
	* tree-flow.h (struct gimple_df): Make free_ssanames a VEC.
	* tree-ssanames.c (fini_ssanames): VEC_free it.
	(make_ssa_name_fn): Update for VECness of free_ssanames.
	(release_ssa_name, release_dead_ssa_names): Likewise.
	* tree.h (struct tree_ssa_name): Include typed_tree instead of
	tree_common.
	* tree.c (initialize_tree_contains_struct): Mark TS_SSA_NAME as
	TS_TYPED instead of TS_COMMON.

diff --git a/gcc/tree-flow.h b/gcc/tree-flow.h
index 14c8827..6b48697 100644
--- a/gcc/tree-flow.h
+++ b/gcc/tree-flow.h
@@ -61,7 +61,7 @@ struct GTY(()) gimple_df {
   struct pointer_map_t * GTY((skip(""))) decls_to_pointers;
 
   /* Free list of SSA_NAMEs.  */
-  tree free_ssanames;
+  VEC(tree,gc) *free_ssanames;
 
   /* Hashtable holding definition for symbol.  If this field is not NULL, it
      means that the first reference to this variable in the function is a
diff --git a/gcc/tree-ssanames.c b/gcc/tree-ssanames.c
index c76dba5..06cdbee 100644
--- a/gcc/tree-ssanames.c
+++ b/gcc/tree-ssanames.c
@@ -96,7 +96,7 @@ void
 fini_ssanames (void)
 {
   VEC_free (tree, gc, SSANAMES (cfun));
-  FREE_SSANAMES (cfun) = NULL;
+  VEC_free (tree, gc, FREE_SSANAMES (cfun));
 }
 
 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes.  */
@@ -124,10 +124,9 @@ make_ssa_name_fn (struct function *fn, tree var, gimple stmt)
   gcc_assert (DECL_P (var));
 
   /* If our free list has an element, then use it.  */
-  if (FREE_SSANAMES (fn))
+  if (!VEC_empty (tree, FREE_SSANAMES (fn)))
     {
-      t = FREE_SSANAMES (fn);
-      FREE_SSANAMES (fn) = TREE_CHAIN (FREE_SSANAMES (fn));
+      t = VEC_pop (tree, FREE_SSANAMES (fn));
 #ifdef GATHER_STATISTICS
       ssa_name_nodes_reused++;
 #endif
@@ -234,9 +233,8 @@ release_ssa_name (tree var)
       /* Note this SSA_NAME is now in the first list.  */
       SSA_NAME_IN_FREE_LIST (var) = 1;
 
-      /* And finally link it into the free list.  */
-      TREE_CHAIN (var) = FREE_SSANAMES (cfun);
-      FREE_SSANAMES (cfun) = var;
+      /* And finally put it on the free list.  */
+      VEC_safe_push (tree, gc, FREE_SSANAMES (cfun), var);
     }
 }
 
@@ -334,8 +332,8 @@ replace_ssa_name_symbol (tree ssa_name, tree sym)
 static unsigned int
 release_dead_ssa_names (void)
 {
-  tree t, next;
-  int n = 0;
+  tree t;
+  int n = VEC_length (tree, FREE_SSANAMES (cfun));
   referenced_var_iterator rvi;
 
   /* Current defs point to various dead SSA names that in turn point to
@@ -343,17 +341,7 @@ release_dead_ssa_names (void)
   FOR_EACH_REFERENCED_VAR (cfun, t, rvi)
     set_current_def (t, NULL);
   /* Now release the freelist.  */
-  for (t = FREE_SSANAMES (cfun); t; t = next)
-    {
-      next = TREE_CHAIN (t);
-      /* Dangling pointers might make GGC to still see dead SSA names, so it is
- 	 important to unlink the list and avoid GGC from seeing all subsequent
-	 SSA names.  In longer run we want to have all dangling pointers here
-	 removed (since they usually go through dead statements that consume
-	 considerable amounts of memory).  */
-      TREE_CHAIN (t) = NULL_TREE;
-      n++;
-    }
+  VEC_free (tree, gc, FREE_SSANAMES (cfun));
   FREE_SSANAMES (cfun) = NULL;
 
   statistics_counter_event (cfun, "SSA names released", n);
diff --git a/gcc/tree.c b/gcc/tree.c
index 7d73c74..072ff19 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -376,6 +376,7 @@ initialize_tree_contains_struct (void)
 	case TS_VECTOR:
 	case TS_STRING:
 	case TS_COMPLEX:
+	case TS_SSA_NAME:
 	  MARK_TS_TYPED (code);
 	  break;
 
@@ -385,7 +386,6 @@ initialize_tree_contains_struct (void)
 	case TS_LIST:
 	case TS_VEC:
 	case TS_EXP:
-	case TS_SSA_NAME:
 	case TS_BLOCK:
 	case TS_BINFO:
 	case TS_STATEMENT_LIST:
diff --git a/gcc/tree.h b/gcc/tree.h
index 11c2f83..80888bc 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1970,7 +1970,7 @@ typedef struct GTY(()) ssa_use_operand_d {
 #define SSA_NAME_IMM_USE_NODE(NODE) SSA_NAME_CHECK (NODE)->ssa_name.imm_uses
 
 struct GTY(()) tree_ssa_name {
-  struct tree_common common;
+  struct typed_tree typed;
 
   /* _DECL wrapped by this SSA name.  */
   tree var;
-- 
1.7.0.4