Fix PR lto/62026 on mainline

[Jan Hubicka]

Hi,
this is mainline version of the fix for thunk creation I comitted to gcc-4.9 
branch week ago.
Bootstrapped/regtested x86_64-linux, comitted.

Honza

        PR lto/62026
        * lto/pr62026.C: New testcase.

        * cgraphclones.c (duplicate_thunk_for_node): Get body to have args
        to duplicate.
        * lto-streamer-out.c (lto_output): Handle correctly thunks that was born
        at WPA time.
Index: testsuite/g++.dg/lto/pr62026.C
===================================================================
--- testsuite/g++.dg/lto/pr62026.C      (revision 0)
+++ testsuite/g++.dg/lto/pr62026.C      (revision 0)
@@ -0,0 +1,22 @@
+// { dg-lto-do link }
+// { dg-lto-options {{-flto -O3 -r -nostdlib}} }
+class C;
+class F {
+  virtual C m_fn1();
+};
+class C {
+ public:
+  virtual int *m_fn3(int);
+};
+class G : F, C {
+  int offsets;
+  int *m_fn3(int);
+};
+C *a;
+int *G::m_fn3(int) {
+  if (offsets) return 0;
+}
+
+void fn1() {
+  for (;;) a->m_fn3(0);
+}
Index: cgraphclones.c
===================================================================
--- cgraphclones.c      (revision 216272)
+++ cgraphclones.c      (working copy)
@@ -295,6 +295,9 @@ duplicate_thunk_for_node (cgraph_node *t
   if (thunk_of->thunk.thunk_p)
     node = duplicate_thunk_for_node (thunk_of, node);
 
+  if (!DECL_ARGUMENTS (thunk->decl))
+    thunk->get_body ();
+
   cgraph_edge *cs;
   for (cs = node->callers; cs; cs = cs->next_caller)
     if (cs->caller->thunk.thunk_p
Index: lto-streamer-out.c
===================================================================
--- lto-streamer-out.c  (revision 216272)
+++ lto-streamer-out.c  (working copy)
@@ -2249,7 +2249,10 @@ lto_output (void)
 #endif
              decl_state = lto_new_out_decl_state ();
              lto_push_out_decl_state (decl_state);
-             if (gimple_has_body_p (node->decl) || !flag_wpa)
+             if (gimple_has_body_p (node->decl) || !flag_wpa
+                 /* Thunks have no body but they may be synthetized
+                    at WPA time.  */
+                 || DECL_ARGUMENTS (node->decl))
                output_function (node);
              else
                copy_function_or_variable (node);