rewrite only if changed.

* vm_trace.c (update_global_event_hook): rewrite ISeqs only when
  effective events are changed.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60765 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

vm_trace.c

@@ -59,11 +59,22 @@ rb_vm_trace_mark_event_hooks(rb_hook_list_t *hooks)
 
 /* ruby_vm_event_flags management */
 
+#define RUBY_EVENTS_TRACE_BY_ISEQ (RUBY_EVENT_LINE  | \
+				   RUBY_EVENT_CLASS | \
+				   RUBY_EVENT_END   | \
+				   RUBY_EVENT_CALL  | \
+				   RUBY_EVENT_RETURN| \
+				   RUBY_EVENT_B_CALL| \
+				   RUBY_EVENT_B_RETURN)
+
 static void
 update_global_event_hook(rb_event_flag_t vm_events)
 {
+    if ((vm_events & RUBY_EVENTS_TRACE_BY_ISEQ) !=
+	(ruby_vm_event_flags & RUBY_EVENTS_TRACE_BY_ISEQ)) {
+	rb_iseq_trace_set_all(vm_events);
+    }
     ruby_vm_event_flags = vm_events;
-    rb_iseq_trace_set_all(vm_events);
     rb_objspace_set_event_hook(vm_events);
 }