[Ada] Fix interfacing with C++ methods on 32-bit Windows

[Eric Botcazou]

Gigi fails to set the "thiscall" calling convention on a method imported from 
C++ if the class has no virtual member functions on the C++ side.

Tested on x86-windows, applied on the mainline.


2015-02-08  Eric Botcazou  <ebotca...@adacore.com>

        * gcc-interface/decl.c (is_cplusplus_method): Use Is_Primitive flag to
        detect primitive operations of tagged and untagged types.


-- 
Eric Botcazou
Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 220511)
+++ gcc-interface/decl.c	(working copy)
@@ -5448,16 +5448,17 @@ is_cplusplus_method (Entity_Id gnat_enti
   if (Convention (gnat_entity) != Convention_CPP)
     return false;
 
-  /* This is the main case: C++ method imported as a primitive operation.  */
-  if (Is_Dispatching_Operation (gnat_entity))
+  /* This is the main case: C++ method imported as a primitive operation.
+     Note that a C++ class with no virtual functions can be imported as a
+     limited record type so the operation is not necessarily dispatching.  */
+  if (Is_Primitive (gnat_entity))
     return true;
 
   /* A thunk needs to be handled like its associated primitive operation.  */
   if (Is_Subprogram (gnat_entity) && Is_Thunk (gnat_entity))
     return true;
 
-  /* C++ classes with no virtual functions can be imported as limited
-     record types, but we need to return true for the constructors.  */
+  /* A constructor is a method on the C++ side.  */
   if (Is_Constructor (gnat_entity))
     return true;