[Ada] Small tweak in LTO mode

[Eric Botcazou]

This make sure the TREE_READONLY flag is set consistently on the definition 
and the references of public entities in LTO mode.

Tested on x86_64-suse-linux, applied on the mainline.


2016-07-11  Eric Botcazou  <ebotca...@adacore.com>

        * gcc-interface/trans.c (add_decl_expr): Minor tweak.
        * gcc-interface/utils.c (create_var_decl): For an external variable,
        also clear TREE_READONLY in LTO mode if the initializer is not a valid
        constant and set DECL_READONLY_ONCE_ELAB instead.

-- 
Eric Botcazou
Index: gcc-interface/utils.c
===================================================================
--- gcc-interface/utils.c	(revision 323148)
+++ gcc-interface/utils.c	(revision 323149)
@@ -2430,8 +2430,9 @@ create_var_decl (tree name, tree asm_nam
      and may be used for scalars in general but not for aggregates.  */
   tree var_decl
     = build_decl (input_location,
-		  (constant_p && const_decl_allowed_p
-		   && !AGGREGATE_TYPE_P (type)) ? CONST_DECL : VAR_DECL,
+		  (constant_p
+		   && const_decl_allowed_p
+		   && !AGGREGATE_TYPE_P (type) ? CONST_DECL : VAR_DECL),
 		  name, type);
 
   /* Detect constants created by the front-end to hold 'reference to function
@@ -2456,9 +2457,20 @@ create_var_decl (tree name, tree asm_nam
      constant initialization and save any variable elaborations for the
      elaboration routine.  If we are just annotating types, throw away the
      initialization if it isn't a constant.  */
-  if ((extern_flag && !constant_p)
+  if ((extern_flag && init && !constant_p)
       || (type_annotate_only && init && !TREE_CONSTANT (init)))
-    init = NULL_TREE;
+    {
+      init = NULL_TREE;
+
+      /* In LTO mode, also clear TREE_READONLY the same way add_decl_expr
+	 would do it if the initializer was not thrown away here, as the
+	 WPA phase requires a consistent view across compilation units.  */
+      if (const_flag && flag_generate_lto)
+	{
+	  const_flag = false;
+	  DECL_READONLY_ONCE_ELAB (var_decl) = 1;
+	}
+    }
 
   /* At the global level, a non-constant initializer generates elaboration
      statements.  Check that such statements are allowed, that is to say,
Index: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c	(revision 323148)
+++ gcc-interface/trans.c	(revision 323149)
@@ -8014,7 +8014,7 @@ void
 add_decl_expr (tree gnu_decl, Entity_Id gnat_entity)
 {
   tree type = TREE_TYPE (gnu_decl);
-  tree gnu_stmt, gnu_init, t;
+  tree gnu_stmt, gnu_init;
 
   /* If this is a variable that Gigi is to ignore, we may have been given
      an ERROR_MARK.  So test for it.  We also might have been given a
@@ -8061,15 +8061,6 @@ add_decl_expr (tree gnu_decl, Entity_Id
 	      && !initializer_constant_valid_p (gnu_init,
 						TREE_TYPE (gnu_init)))))
     {
-      /* If GNU_DECL has a padded type, convert it to the unpadded
-	 type so the assignment is done properly.  */
-      if (TYPE_IS_PADDING_P (type))
-	t = convert (TREE_TYPE (TYPE_FIELDS (type)), gnu_decl);
-      else
-	t = gnu_decl;
-
-      gnu_stmt = build_binary_op (INIT_EXPR, NULL_TREE, t, gnu_init);
-
       DECL_INITIAL (gnu_decl) = NULL_TREE;
       if (TREE_READONLY (gnu_decl))
 	{
@@ -8077,6 +8068,12 @@ add_decl_expr (tree gnu_decl, Entity_Id
 	  DECL_READONLY_ONCE_ELAB (gnu_decl) = 1;
 	}
 
+      /* If GNU_DECL has a padded type, convert it to the unpadded
+	 type so the assignment is done properly.  */
+      if (TYPE_IS_PADDING_P (type))
+	gnu_decl = convert (TREE_TYPE (TYPE_FIELDS (type)), gnu_decl);
+
+      gnu_stmt = build_binary_op (INIT_EXPR, NULL_TREE, gnu_decl, gnu_init);
       add_stmt_with_node (gnu_stmt, gnat_entity);
     }
 }