Add ability to disable the stats timer

Summary:
Recording timing stats for every JS<->C++ transition has some overhead, so add the ability for applications where such transitions are extremely frequent to disable the stats timer.

Use this in the recently added JSI microbenchmark.

Reviewed By: mhorowitz

Differential Revision: D32055120

fbshipit-source-id: 5d173c58e82ea1fbf6fdad2f6b37ab7d4f235f42

API/hermes/hermes.cpp

@@ -249,6 +249,17 @@ class StackRuntime {
 
 } // namespace
 
+// Recording timing stats for every JS<->C++ transition has some overhead, so
+// applications where such transitions are extremely frequent may want to define
+// the HERMESJSI_DISABLE_STATS_TIMER symbol to save this overhead.
+#ifdef HERMESJSI_DISABLE_STATS_TIMER
+#define STATS_TIMER(rt, desc, field)
+#else
+#define STATS_TIMER(rt, desc, field)              \
+  auto &_stats = (rt).runtime_.getRuntimeStats(); \
+  const vm::instrumentation::RAIITimer _timer{desc, _stats, _stats.field};
+#endif
+
 class HermesRuntimeImpl final : public HermesRuntime,
                                 private InstallHermesFatalErrorHandler,
                                 private jsi::Instrumentation {
@@ -837,9 +848,7 @@ class HermesRuntimeImpl final : public HermesRuntime,
         : rt_(rt), ho_(ho) {}
 
     vm::CallResult<vm::HermesValue> get(vm::SymbolID id) override {
-      auto &stats = rt_.runtime_.getRuntimeStats();
-      const vm::instrumentation::RAIITimer timer{
-          "HostObject.get", stats, stats.hostFunction};
+      STATS_TIMER(rt_, "HostObject.get", hostFunction);
       jsi::PropNameID sym =
           rt_.add<jsi::PropNameID>(vm::HermesValue::encodeSymbolValue(id));
       jsi::Value ret;
@@ -873,9 +882,7 @@ class HermesRuntimeImpl final : public HermesRuntime,
     }
 
     vm::CallResult<bool> set(vm::SymbolID id, vm::HermesValue value) override {
-      auto &stats = rt_.runtime_.getRuntimeStats();
-      const vm::instrumentation::RAIITimer timer{
-          "HostObject.set", stats, stats.hostFunction};
+      STATS_TIMER(rt_, "HostObject.set", hostFunction);
       jsi::PropNameID sym =
           rt_.add<jsi::PropNameID>(vm::HermesValue::encodeSymbolValue(id));
       try {
@@ -907,9 +914,7 @@ class HermesRuntimeImpl final : public HermesRuntime,
     }
 
     vm::CallResult<vm::Handle<vm::JSArray>> getHostPropertyNames() override {
-      auto &stats = rt_.runtime_.getRuntimeStats();
-      const vm::instrumentation::RAIITimer timer{
-          "HostObject.getHostPropertyNames", stats, stats.hostFunction};
+      STATS_TIMER(rt_, "HostObject.getHostPropertyNames", hostFunction);
       try {
         auto names = ho_->getPropertyNames(rt_);
 
@@ -959,9 +964,7 @@ class HermesRuntimeImpl final : public HermesRuntime,
       HFContext *hfc = reinterpret_cast<HFContext *>(context);
       HermesRuntimeImpl &rt = hfc->hermesRuntimeImpl;
       assert(runtime == &rt.runtime_);
-      auto &stats = rt.runtime_.getRuntimeStats();
-      const vm::instrumentation::RAIITimer timer{
-          "Host Function", stats, stats.hostFunction};
+      STATS_TIMER(rt, "Host Function", hostFunction);
 
       llvh::SmallVector<jsi::Value, 8> apiArgs;
       for (vm::HermesValue hv : hvArgs) {
@@ -1476,9 +1479,7 @@ jsi::Value HermesRuntimeImpl::evaluatePreparedJavaScript(
     assert(
         dynamic_cast<const HermesPreparedJavaScript *>(js.get()) &&
         "js must be an instance of HermesPreparedJavaScript");
-    auto &stats = runtime_.getRuntimeStats();
-    const vm::instrumentation::RAIITimer timer{
-        "Evaluate JS", stats, stats.evaluateJS};
+    STATS_TIMER(*this, "Evaluate JS", evaluateJS);
     const auto *hermesPrep =
         static_cast<const HermesPreparedJavaScript *>(js.get());
     vm::GCScope gcScope(&runtime_);
@@ -2008,9 +2009,7 @@ jsi::Value HermesRuntimeImpl::call(
           "HermesRuntimeImpl::call: Unable to call function: stack overflow");
     }
 
-    auto &stats = runtime_.getRuntimeStats();
-    const vm::instrumentation::RAIITimer timer{
-        "Incoming Function", stats, stats.incomingFunction};
+    STATS_TIMER(*this, "Incoming Function", incomingFunction);
     vm::ScopedNativeCallFrame newFrame{
         &runtime_,
         static_cast<uint32_t>(count),
@@ -2049,11 +2048,8 @@ jsi::Value HermesRuntimeImpl::callAsConstructor(
           "HermesRuntimeImpl::call: Unable to call function: stack overflow");
     }
 
-    auto &stats = runtime_.getRuntimeStats();
-    const vm::instrumentation::RAIITimer timer{
-        "Incoming Function: Call As Constructor",
-        stats,
-        stats.incomingFunction};
+    STATS_TIMER(
+        *this, "Incoming Function: Call As Constructor", incomingFunction);
 
     // We follow es5 13.2.2 [[Construct]] here. Below F == func.
     // 13.2.2.5: