Introduce RuntimeCallStats::IsEnabled

src/counters.h

Index: src/counters.h
diff --git a/src/counters.h b/src/counters.h
index 0cd0def57a00ea5c06ed1950f4bbe017def32134..bd882aa83817e8ea99f95824fb5a9fe5503ccb20 100644
--- a/src/counters.h
+++ b/src/counters.h
@@ -805,6 +805,13 @@ class RuntimeCallStats {
   static void CorrectCurrentCounterId(RuntimeCallStats* stats,
                                       CounterId counter_id);
 
+  // Returns true if RuntimeCallStats are enabled either through a flag or
+  // with tracing.
+  static bool IsEnabled() {

[fmeawad, 2016/10/28 21:54:25]

Wouldn't that add an extra call per check? Why a method and not a macro?

[Camillo Bruni, 2016/10/31 09:57:18]

From what I've seen so far is that clang inlines very aggressively, so I'm
pretty confident that this actually works as intended.

+    return V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED()) ||
+           FLAG_runtime_call_stats;

[Camillo Bruni, 2016/10/31 09:57:58]

nit: put the V8_UNLIKELY around the whole clause, we generally expect the
runtime stats to be disabled

+  }
+
   void Reset();
   void Print(std::ostream& os);
   V8_NOINLINE void Dump(v8::tracing::TracedValue* value);
@@ -824,14 +831,13 @@ class RuntimeCallStats {
   bool in_use_;
 };
 
-#define TRACE_RUNTIME_CALL_STATS(isolate, counter_name)                 \
-  do {                                                                  \
-    if (V8_UNLIKELY(TRACE_EVENT_RUNTIME_CALL_STATS_TRACING_ENABLED() || \
-                    FLAG_runtime_call_stats)) {                         \
-      RuntimeCallStats::CorrectCurrentCounterId(                        \
-          isolate->counters()->runtime_call_stats(),                    \
-          &RuntimeCallStats::counter_name);                             \
-    }                                                                   \
+#define TRACE_RUNTIME_CALL_STATS(isolate, counter_name) \
+  do {                                                  \
+    if (RuntimeCallStats::IsEnabled()) {                \
+      RuntimeCallStats::CorrectCurrentCounterId(        \
+          isolate->counters()->runtime_call_stats(),    \
+          &RuntimeCallStats::counter_name);             \
+    }                                                   \
   } while (false)
 
 #define TRACE_HANDLER_STATS(isolate, counter_name) \