Prune BLOCK_VARs lists in free_lang_data

[Jan Hubicka]

Hi,
this is last of my patches to improve partitionability of programs. 
This patch compacts BLOCK_VARs lists and trows away TYPE_DECLs for -g0
and redundant TYPE_DECLs on all levels. It does make noticeable difference
on firefox, but I managed to erase the numbers (can re-test them if requested)

Bootstrapped/regtested x86_64-linux, OK?

        * tree.c (needed_in_block_vars_p): New function.
        (free_lang_data_in_decl): Use it.
Index: tree.c
===================================================================
--- tree.c      (revision 232407)
+++ tree.c      (working copy)
@@ -5343,6 +5343,42 @@ need_assembler_name_p (tree decl)
   return true;
 }
 
+/* Return true if DECL should stay in BLOCK_VARs list.  */
+
+static inline bool
+needed_in_block_vars_p (const_tree decl)
+{
+  if (TREE_CODE (decl) == VAR_DECL && TREE_USED (decl)
+      && (!TREE_STATIC (decl) || DECL_EXTERNAL (decl)))
+    return true;
+  if (TREE_CODE (decl) == RESULT_DECL)
+    return true;
+  /* Dwarf2out output non-fortran and non-ada const decls when the
+     enum is output and it will not consider language to be ada or fortran
+     in LTO.  */
+  if (TREE_CODE (decl) == CONST_DECL)
+    return false;
+  if (debug_info_level >= DINFO_LEVEL_TERSE)
+    return false;
+  /* Strip builtins from the translation-unit BLOCK.  We still have targets
+     without builtin_decl_explicit support and also builtins are shared
+     nodes and thus we can't use TREE_CHAIN in multiple lists.  */
+  if (TREE_CODE (decl) == FUNCTION_DECL
+      && DECL_BUILT_IN (decl))
+    return false;
+  if (DECL_IGNORED_P (decl))
+    return false;
+  if (TREE_CODE (decl) == TYPE_DECL
+      && is_redundant_typedef (decl))
+    return false;
+  gcc_checking_assert (TREE_CODE (decl) == TYPE_DECL
+                      || TREE_CODE (decl) == VAR_DECL
+                      || TREE_CODE (decl) == FUNCTION_DECL
+                      || TREE_CODE (decl) == LABEL_DECL
+                      || TREE_CODE (decl) == RESULT_DECL);
+  return true;
+}
+
 
 /* Reset all language specific information still present in symbol
    DECL.  */
@@ -5445,15 +5481,11 @@ free_lang_data_in_decl (tree decl)
            && DECL_INITIAL (decl)
            && TREE_CODE (DECL_INITIAL (decl)) == BLOCK)
     {
-      /* Strip builtins from the translation-unit BLOCK.  We still have targets
-        without builtin_decl_explicit support and also builtins are shared
-        nodes and thus we can't use TREE_CHAIN in multiple lists.  */
       tree *nextp = &BLOCK_VARS (DECL_INITIAL (decl));
       while (*nextp)
         {
           tree var = *nextp;
-          if (TREE_CODE (var) == FUNCTION_DECL
-              && DECL_BUILT_IN (var))
+          if (needed_in_block_vars_p (var))
            *nextp = TREE_CHAIN (var);
          else
            nextp = &TREE_CHAIN (var);