Try to do potentially costly operations in is_first_C_frame() as late…

… as possible

src/hotspot/share/runtime/os.cpp

@@ -1307,9 +1307,8 @@ bool os::is_first_C_frame(frame* fr) {
   uintptr_t old_sp = (uintptr_t)fr->sender_sp();
   if ((uintptr_t)fr->sender_sp() == (uintptr_t)-1 || is_pointer_bad(fr->sender_sp())) return true;
 
-  uintptr_t old_fp = (uintptr_t)fr->link_or_null();
-  if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp ||
-    is_pointer_bad(fr->link_or_null())) return true;
+  uintptr_t old_fp = (uintptr_t)fr->link();
+  if (old_fp == 0 || old_fp == (uintptr_t)-1 || old_fp == ufp) return true;
 
   // stack grows downwards; if old_fp is below current fp or if the stack
   // frame is too large, either the stack is corrupted or fp is not saved
@@ -1318,6 +1317,8 @@ bool os::is_first_C_frame(frame* fr) {
   if (old_fp < ufp) return true;
   if (old_fp - ufp > 64 * K) return true;
 
+  if (is_pointer_bad((intptr_t*) old_fp)) return true;
+
   return false;
 }