re PR lto/61886 (LTO breaks fread with _FORTIFY_SOURCE=2)

	PR ipa/61886
	* symtab.c (ultimate_transparent_alias_target): New inline function.
	(symbol_table::assembler_names_equal_p): New method; break out from ...
	(symbol_table::decl_assembler_name_equal): ... here.
	(symbol_table::change_decl_assembler_name): Also update names and
	translation links of transparent aliases.
	(symtab_node::dump_base): Dump transparent_alias.
	(symtab_node::verify_base): Implement basic transparent alias
	verification.
	(symtab_node::make_decl_local): Support localization of weakrefs;
	recurse to transparent aliases; set TREE_STATIC.
	(symtab_node::ultimate_alias_target_1): Handle visibility of
	transparent aliases.
	(symtab_node::resolve_alias): New parmaeter transparent; handle
	transparent aliases; recurse to aliases of aliases to fix comdat
	groups.
	(symtab_node::get_partitioning_class): Handle transparent aliases.
	* ipa-visibility.c (cgraph_externally_visible_p,
	varpool_node::externally_visible_p): Visibility of transparent alias
	depends on its target.
	(function_and_variable_visibility): Do not tweak visibility of
	transparent laiases.
	(function_and_variable_visibility): Likewise.
	* ipa.c (symbol_table::remove_unreachable_nodes): Clear
	transparent_alias flag.
	* alias.c (cgraph_node::create_alias, cgraph_node::get_availability):
	Support transparent aliases.
	* cgraph.h (symtab_node): Update prototype of resolve_alias;
	add transparent_alias flag.
	(symbol_table: Add assembler_names_equal_p.
	(symtab_node::real_symbol_p): Skip transparent aliases.
	* cgraphunit.c (cgraph_node::reset): Reset transparent_alias flag.
	(handle_alias_pairs): Set transparent_alias for weakref.
	(cgraph_node::assemble_thunks_and_aliases): Do not asemble transparent
	aliases.
	* lto-cgraph.c (lto_output_node): When outputting same_comdat_group
	skip symbols not put into boundary; stream transparent_alias.
	(lto_output_varpool_node): Likewise.
	(input_overwrite_node, input_varpool_node): Stream transparent alias.
	* varpool.c (ctor_for_folding, varpool_node::get_availability,
	varpool_node::assemble_aliases,
	symbol_table::remove_unreferenced_decls): Handle transparent aliase.
	(varpool_node::create_alias): Set transparent_alias.

	* lto-partition.c (add_symbol_to_partition_1, contained_in_symbol,
	rename_statics, rename_statics): Handle transparent aliases.

From-SVN: r231373

1 files changed, 30 insertions, 1 deletions

diff --git a/gcc/cgraph.h b/gcc/cgraph.h
index e689fcd..7c643502 100644
--- a/gcc/cgraph.h
+++ b/gcc/cgraph.h
@@ -249,9 +249,10 @@ public:
   inline symtab_node *next_defined_symbol (void);
 
   /* Add reference recording that symtab node is alias of TARGET.
+     If TRANSPARENT is true make the alias to be transparent alias.
      The function can fail in the case of aliasing cycles; in this case
      it returns false.  */
-  bool resolve_alias (symtab_node *target);
+  bool resolve_alias (symtab_node *target, bool transparent = false);
 
   /* C++ FE sometimes change linkage flags after producing same
      body aliases.  */
@@ -421,6 +422,28 @@ public:
   /* True when symbol is an alias.
      Set by ssemble_alias.  */
   unsigned alias : 1;
+  /* When true the alias is translated into its target symbol either by GCC
+     or assembler (it also may just be a duplicate declaration of the same
+     linker name).
+
+     Currently transparent aliases come in three different flavors
+       - aliases having the same assembler name as their target (aka duplicated
+	 declarations). In this case the assembler names compare via
+	 assembler_names_equal_p and weakref is false
+       - aliases that are renamed at a time being output to final file
+	 by varasm.c. For those DECL_ASSEMBLER_NAME have
+	 IDENTIFIER_TRANSPARENT_ALIAS set and thus also their assembler
+	 name must be unique.
+	 Weakrefs belong to this cateogry when we target assembler without
+	 .weakref directive.
+       - weakrefs that are renamed by assembler via .weakref directive.
+	 In this case the alias may or may not be definition (depending if
+	 target declaration was seen by the compiler), weakref is set.
+	 Unless we are before renaming statics, assembler names are different.
+
+     Given that we now support duplicate declarations, the second option is
+     redundant and will be removed.  */
+  unsigned transparent_alias : 1;
   /* True when alias is a weakref.  */
   unsigned weakref : 1;
   /* C++ frontend produce same body aliases and extra name aliases for
@@ -2098,6 +2121,10 @@ public:
   /* Set the DECL_ASSEMBLER_NAME and update symtab hashtables.  */
   void change_decl_assembler_name (tree decl, tree name);
 
+  /* Return true if assembler names NAME1 and NAME2 leads to the same symbol
+     name.  */
+  static bool assembler_names_equal_p (const char *name1, const char *name2);
+
   int cgraph_count;
   int cgraph_max_uid;
   int cgraph_max_summary_uid;
@@ -2251,6 +2278,8 @@ symtab_node::real_symbol_p (void)
 
   if (DECL_ABSTRACT_P (decl))
     return false;
+  if (transparent_alias && definition)
+    return false;
   if (!is_a <cgraph_node *> (this))
     return true;
   cnode = dyn_cast <cgraph_node *> (this);