[Ada] Do not propagate Object_Size onto Size for composite types

2019-12-18  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* layout.adb (Layout_Type): In the case of composite types, do
	not copy the Esize onto the RM_Size if the latter is not set.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Record_Type>:
	Also cap the alignment if an Object_Size clause has been
	specified.  Pass VAR_DECL in the call to validate_size for the
	Esize of a type.
	(validate_size): Be prepared to give an error on an Object_Size
	clause.

From-SVN: r279507

gcc/ada/ChangeLog

 2019-12-18  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* layout.adb (Layout_Type): In the case of composite types, do
+	not copy the Esize onto the RM_Size if the latter is not set.
+	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Record_Type>:
+	Also cap the alignment if an Object_Size clause has been
+	specified.  Pass VAR_DECL in the call to validate_size for the
+	Esize of a type.
+	(validate_size): Be prepared to give an error on an Object_Size
+	clause.
+
+2019-12-18  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* einfo.ads (Handling of Type'Size Value): Add references to the
 	introduction of Object_Size in Ada 2020.
 	* sem_eval.adb (Subtypes_Statically_Match): Likewise.

gcc/ada/gcc-interface/decl.c

@@ -3054,6 +3054,15 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 		if (max_align < BIGGEST_ALIGNMENT)
 		  TYPE_MAX_ALIGN (gnu_type) = max_align;
 	      }
+
+	    /* Similarly if an Object_Size clause has been specified.  */
+	    else if (Known_Esize (gnat_entity))
+	      {
+		unsigned int max_size = UI_To_Int (Esize (gnat_entity));
+		unsigned int max_align = max_size & -max_size;
+		if (max_align < BIGGEST_ALIGNMENT)
+		  TYPE_MAX_ALIGN (gnu_type) = max_align;
+	      }
 	  }
 
 	/* If we have a Parent_Subtype, make a field for the parent.  If
@@ -4241,11 +4250,15 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	 non-constant).  */
       if (!gnu_size && kind != E_String_Literal_Subtype)
 	{
-	  Uint gnat_size = Known_Esize (gnat_entity)
-			   ? Esize (gnat_entity) : RM_Size (gnat_entity);
-	  gnu_size
-	    = validate_size (gnat_size, gnu_type, gnat_entity, TYPE_DECL,
-			     false, Has_Size_Clause (gnat_entity), NULL, NULL);
+	  if (Known_Esize (gnat_entity))
+	    gnu_size
+	      = validate_size (Esize (gnat_entity), gnu_type, gnat_entity,
+			       VAR_DECL, false, false, NULL, NULL);
+	  else
+	    gnu_size
+	      = validate_size (RM_Size (gnat_entity), gnu_type, gnat_entity,
+			       TYPE_DECL, false, Has_Size_Clause (gnat_entity),
+			       NULL, NULL);
 	}
 
       /* If a size was specified, see if we can make a new type of that size
@@ -8872,6 +8885,8 @@ validate_size (Uint uint_size, tree gnu_type, Entity_Id gnat_object,
     gnat_error_node = Last_Bit (Component_Clause (gnat_object));
   else if (Present (Size_Clause (gnat_object)))
     gnat_error_node = Expression (Size_Clause (gnat_object));
+  else if (Has_Object_Size_Clause (gnat_object))
+    gnat_error_node = Expression (Object_Size_Clause (gnat_object));
   else
     gnat_error_node = gnat_object;
 

gcc/ada/layout.adb

@@ -435,14 +435,6 @@ package body Layout is
             end;
          end if;
 
-         --  If Esize is set, and RM_Size is not, RM_Size is copied from Esize.
-         --  At least for now this seems reasonable, and is in any case needed
-         --  for compatibility with old versions of gigi.
-
-         if Known_Esize (E) and then Unknown_RM_Size (E) then
-            Set_RM_Size (E, Esize (E));
-         end if;
-
          --  For array base types, set the component size if object size of the
          --  component type is known and is a small power of 2 (8, 16, 32, 64),
          --  since this is what will always be used, except if a very large