cgraph.h (struct varpool_node): new used_from_object_file flag.

2010-06-28  Bingfeng Mei <bmei@broadcom.com>

        * cgraph.h (struct varpool_node): new used_from_object_file flag.
        (struct cgraph_local_info): new used_from_object_file flag.
        * cgraph.c (dump_cgraph_node): dump used_from_object_file flag.
        (cgraph_clone_node): initialize used_from_object_file.
        (cgraph_create_virtual_clone): initialize used_from_object_file.
        * lto-symbtab.c (lto_symtab_merge_decls_1): Set
        used_from_object_file flags for symbols of LDPR_PREVAILING_DEF
        when compiling with -fwhole-program.
        (lto_symtab_resolve_symbols) Use LDPR_PREVAILING_DEF_IRONLY for
	internal resolver.
        * ipa.c (function_and_variable_visibility): Set externally_visible
        flag of varpool_node if used_from_object_file flag is set.
        (cgraph_externally_visible_p): check used_from_object_file flag.
        * doc/invoke.texi (-fwhole-program option): Change description of
        externally_visible attribute accordingly.
        * doc/extend.texi (externally_visible): Ditto.

From-SVN: r161483

gcc/ChangeLog

@@ -1,3 +1,22 @@
+2010-06-28  Bingfeng Mei <bmei@broadcom.com>
+
+        * cgraph.h (struct varpool_node): new used_from_object_file flag.
+        (struct cgraph_local_info): new used_from_object_file flag.
+        * cgraph.c (dump_cgraph_node): dump used_from_object_file flag.
+        (cgraph_clone_node): initialize used_from_object_file.
+        (cgraph_create_virtual_clone): initialize used_from_object_file.
+        * lto-symbtab.c (lto_symtab_merge_decls_1): Set
+        used_from_object_file flags for symbols of LDPR_PREVAILING_DEF
+        when compiling with -fwhole-program.
+        (lto_symtab_resolve_symbols) Use LDPR_PREVAILING_DEF_IRONLY for
+	internal resolver.
+        * ipa.c (function_and_variable_visibility): Set externally_visible
+        flag of varpool_node if used_from_object_file flag is set.
+        (cgraph_externally_visible_p): check used_from_object_file flag.
+        * doc/invoke.texi (-fwhole-program option): Change description of
+        externally_visible attribute accordingly.
+        * doc/extend.texi (externally_visible): Ditto.
+
 2010-06-27  Jan Hubicka  <jh@suse.cz>
 
 	* params.def (max-inline-insns-auto): Default to 40.

gcc/cgraph.c

@@ -1825,6 +1825,8 @@ dump_cgraph_node (FILE *f, struct cgraph_node *node)
     fprintf (f, " local");
   if (node->local.externally_visible)
     fprintf (f, " externally_visible");
+  if (node->local.used_from_object_file)
+    fprintf (f, " used_from_object_file");
   if (node->local.finalized)
     fprintf (f, " finalized");
   if (node->local.disregard_inline_limits)
@@ -2075,6 +2077,7 @@ cgraph_clone_node (struct cgraph_node *n, tree decl, gcov_type count, int freq,
   new_node->analyzed = n->analyzed;
   new_node->local = n->local;
   new_node->local.externally_visible = false;
+  new_node->local.used_from_object_file = false;
   new_node->local.local = true;
   new_node->local.vtable_method = false;
   new_node->global = n->global;
@@ -2266,6 +2269,7 @@ cgraph_create_virtual_clone (struct cgraph_node *old_node,
   else
     new_node->clone.combined_args_to_skip = args_to_skip;
   new_node->local.externally_visible = 0;
+  new_node->local.used_from_object_file = 0;
   new_node->local.local = 1;
   new_node->lowered = true;
   new_node->reachable = true;

gcc/cgraph.h

@@ -102,6 +102,9 @@ struct GTY(()) cgraph_local_info {
   /* Set when function is visible by other units.  */
   unsigned externally_visible : 1;
 
+  /* Set when resolver determines that function is visible by other units.  */
+  unsigned used_from_object_file : 1;
+  
   /* Set once it has been finalized so we consider it to be output.  */
   unsigned finalized : 1;
 
@@ -487,6 +490,8 @@ struct GTY((chain_next ("%h.next"), chain_prev ("%h.prev"))) varpool_node {
   unsigned output : 1;
   /* Set when function is visible by other units.  */
   unsigned externally_visible : 1;
+  /* Set when resolver determines that variable is visible by other units.  */
+  unsigned used_from_object_file : 1;
   /* Set for aliases once they got through assemble_alias.  Also set for
      extra name aliases in varpool_extra_name_alias.  */
   unsigned alias : 1;

gcc/doc/extend.texi

@@ -2296,7 +2296,7 @@ attribute is present.
 @cindex @code{externally_visible} attribute.
 This attribute, attached to a global variable or function, nullifies
 the effect of the @option{-fwhole-program} command-line option, so the
-object remains visible outside the current compilation unit.
+object remains visible outside the current compilation unit. If @option{-fwhole-program} is used together with @option{-flto} and @command{gold} is used as the linker plugin, @code{externally_visible} attributes are automatically added to functions (not variable yet due to a current @command{gold} issue) that are accessed outside of LTO objects according to resolution file produced by @command{gold}.  For other linkers that cannot generate resolution file, explicit @code{externally_visible} attributes are still necessary.
 
 @item far
 @cindex functions which handle memory bank switching

gcc/doc/invoke.texi

@@ -7310,7 +7310,7 @@ Enabled by default with @option{-funroll-loops}.
 Assume that the current compilation unit represents the whole program being
 compiled.  All public functions and variables with the exception of @code{main}
 and those merged by attribute @code{externally_visible} become static functions
-and in effect are optimized more aggressively by interprocedural optimizers.
+and in effect are optimized more aggressively by interprocedural optimizers. If @command{gold} is used as the linker plugin, @code{externally_visible} attributes are automatically added to functions (not variable yet due to a current @command{gold} issue) that are accessed outside of LTO objects according to resolution file produced by @command{gold}.  For other linkers that cannot generate resolution file, explicit @code{externally_visible} attributes are still necessary.
 While this option is equivalent to proper use of the @code{static} keyword for
 programs consisting of a single file, in combination with option
 @option{-combine}, @option{-flto} or @option{-fwhopr} this flag can be used to

gcc/ipa.c

@@ -576,6 +576,8 @@ cgraph_externally_visible_p (struct cgraph_node *node, bool whole_program)
     return false;
   if (!whole_program)
     return true;
+  if (node->local.used_from_object_file)
+    return true;
   if (DECL_PRESERVE_P (node->decl))
     return true;
   /* COMDAT functions must be shared only if they have address taken,
@@ -729,6 +731,7 @@ function_and_variable_visibility (bool whole_program)
 	         we start reordering datastructures.  */
 	      || DECL_COMDAT (vnode->decl)
 	      || DECL_WEAK (vnode->decl)
+              || vnode->used_from_object_file
 	      || lookup_attribute ("externally_visible",
 				   DECL_ATTRIBUTES (vnode->decl))))
 	vnode->externally_visible = true;

gcc/lto-symtab.c

@@ -530,11 +530,20 @@ lto_symtab_resolve_symbols (void **slot)
     return;
 
 found:
-  if (TREE_CODE (prevailing->decl) == VAR_DECL
-      && TREE_READONLY (prevailing->decl))
+  /* If current lto files represent the whole program,
+    it is correct to use LDPR_PREVALING_DEF_IRONLY.
+    If current lto files are part of whole program, internal
+    resolver doesn't know if it is LDPR_PREVAILING_DEF
+    or LDPR_PREVAILING_DEF_IRONLY.  Use IRONLY conforms to
+    using -fwhole-program.  Otherwise, it doesn't
+    matter using either LDPR_PREVAILING_DEF or
+    LDPR_PREVAILING_DEF_IRONLY
+    
+    FIXME: above workaround due to gold plugin makes some
+    variables IRONLY, which are indeed PREVAILING_DEF in
+    resolution file.  These variables still need manual
+    externally_visible attribute.  */
     prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY;
-  else
-    prevailing->resolution = LDPR_PREVAILING_DEF;
 }
 
 /* Merge all decls in the symbol table chain to the prevailing decl and
@@ -698,6 +707,24 @@ lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED)
       && TREE_CODE (prevailing->decl) != VAR_DECL)
     prevailing->next = NULL;
 
+  /* Set externally_visible flags for declaration of LDPR_PREVAILING_DEF */
+  if (flag_whole_program)
+    {
+      if (prevailing->resolution == LDPR_PREVAILING_DEF)
+        {
+          if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
+            prevailing->node->local.used_from_object_file = true;
+          else
+            prevailing->vnode->used_from_object_file = true;
+        }
+      else if (prevailing->resolution == LDPR_PREVAILING_DEF_IRONLY)
+        {
+          if (TREE_CODE (prevailing->decl) == FUNCTION_DECL)
+            prevailing->node->local.used_from_object_file = false;
+          else
+            prevailing->vnode->used_from_object_file = false;
+        }
+    }
   return 1;
 }