cgraph.c (cgraph_function_body_availability): Do not check cgrpah flags.

	* cgraph.c (cgraph_function_body_availability): Do not check cgrpah flags.
	* cgraph.h (symtab_for_node_and_aliases, symtab_nonoverwritable_alias,
	symtab_node_availability): Declare.
	* ipa.c (can_replace_by_local_alias): New.
	(function_and_variable_visibility): Use it.
	* symtab.c (symtab_for_node_and_aliases, symtab_nonoverwritable_alias_1,
	symtab_nonoverwritable_alias): New.

Co-Authored-By: Martin Liska <marxin.liska@gmail.com>

From-SVN: r201439

1 files changed, 45 insertions, 1 deletions

diff --git a/gcc/ipa.c b/gcc/ipa.c
index 085454d..f42de4d 100644
--- a/gcc/ipa.c
+++ b/gcc/ipa.c
@@ -751,6 +751,21 @@ varpool_externally_visible_p (struct varpool_node *vnode)
   return false;
 }
 
+/* Return true if reference to NODE can be replaced by a local alias.
+   Local aliases save dynamic linking overhead and enable more optimizations.
+ */
+
+bool
+can_replace_by_local_alias (symtab_node node)
+{
+  return (symtab_node_availability (node) > AVAIL_OVERWRITABLE
+	  && !DECL_EXTERNAL (node->symbol.decl)
+	  && (!DECL_ONE_ONLY (node->symbol.decl)
+	      || node->symbol.resolution == LDPR_PREVAILING_DEF
+	      || node->symbol.resolution == LDPR_PREVAILING_DEF_IRONLY
+	      || node->symbol.resolution == LDPR_PREVAILING_DEF_IRONLY_EXP));
+}
+
 /* Mark visibility of all functions.
 
    A local function is one whose calls can occur only in the current
@@ -872,7 +887,36 @@ function_and_variable_visibility (bool whole_program)
 	}
     }
   FOR_EACH_DEFINED_FUNCTION (node)
-    node->local.local = cgraph_local_node_p (node);
+    {
+      node->local.local = cgraph_local_node_p (node);
+
+      /* If we know that function can not be overwritten by a different semantics
+	 and moreover its section can not be discarded, replace all direct calls
+	 by calls to an nonoverwritable alias.  This make dynamic linking
+	 cheaper and enable more optimization.
+
+	 TODO: We can also update virtual tables.  */
+      if (node->callers && can_replace_by_local_alias ((symtab_node)node))
+	{
+	  struct cgraph_node *alias = cgraph (symtab_nonoverwritable_alias ((symtab_node) node));
+
+	  if (alias != node)
+	    {
+	      while (node->callers)
+		{
+		  struct cgraph_edge *e = node->callers;
+
+		  cgraph_redirect_edge_callee (e, alias);
+		  if (!flag_wpa)
+		    {
+		      push_cfun (DECL_STRUCT_FUNCTION (e->caller->symbol.decl));
+		      cgraph_redirect_edge_call_stmt_to_callee (e);
+		      pop_cfun ();
+		    }
+		}
+	    }
+	}
+    }
   FOR_EACH_VARIABLE (vnode)
     {
       /* weak flag makes no sense on local variables.  */