Change how native require hook is registered

Summary:
Instead of two separate dispatches to the JavaScript thread, only do one. Avoid the strongSelf dance entirely.

This refactor does mean that the cost of registering the nativeRequire hook on the context is not measured by the `RCTPLRAMBundleLoad` tag. However it should be almost zero-cost to construct and set a single block, so I'm OK with that change.

Reviewed By: bnham

Differential Revision: D3542940

fbshipit-source-id: d6bd26e478d0d33b56f8116d7efe6aac80c91711

React/Executors/RCTJSCExecutor.mm

@@ -669,10 +669,14 @@ static void installBasicSynchronousHooksOnContext(JSContext *context)
     [_performanceLogger markStartForTag:RCTPLRAMBundleLoad];
     NSError *error;
     script = loadRAMBundle(sourceURL, &error, _randomAccessBundle);
-    [self registerNativeRequire];
     [_performanceLogger markStopForTag:RCTPLRAMBundleLoad];
     [_performanceLogger setValue:script.length forTag:RCTPLRAMStartupCodeSize];
 
+    // Reset the counters that the native require implementation uses
+    [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequires];
+    [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequiresCount];
+    [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequiresSize];
+
     if (error) {
       if (onComplete) {
         onComplete(error);
@@ -694,6 +698,10 @@ static void installBasicSynchronousHooksOnContext(JSContext *context)
     if (!self.isValid) {
       return;
     }
+    if (isRAMBundle) {
+      __weak RCTJSCExecutor *weakSelf = self;
+      self.context.context[@"nativeRequire"] = ^(NSNumber *moduleID) { [weakSelf _nativeRequire:moduleID]; };
+    }
     [self->_performanceLogger markStartForTag:RCTPLScriptExecution];
     NSError *error = executeApplicationScript(self->_jscWrapper, script, sourceURL, self->_context.context.JSGlobalContextRef);
     [self->_performanceLogger markStopForTag:RCTPLScriptExecution];
@@ -809,48 +817,34 @@ static void executeRandomAccessModule(RCTJSCExecutor *executor, uint32_t moduleI
   }
 }
 
-- (void)registerNativeRequire
+- (void)_nativeRequire:(NSNumber *)moduleID
 {
-  [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequires];
-  [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequiresCount];
-  [_performanceLogger setValue:0 forTag:RCTPLRAMNativeRequiresSize];
+  if (!moduleID) {
+    return;
+  }
 
-  [self executeBlockOnJavaScriptQueue:^{
-    if (!self.valid) {
+  [_performanceLogger addValue:1 forTag:RCTPLRAMNativeRequiresCount];
+  [_performanceLogger appendStartForTag:RCTPLRAMNativeRequires];
+  RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
+                          [@"nativeRequire_" stringByAppendingFormat:@"%@", moduleID], nil);
+
+  const uint32_t ID = [moduleID unsignedIntValue];
+
+  if (ID < _randomAccessBundle.numTableEntries) {
+    ModuleData *moduleData = &_randomAccessBundle.table[ID];
+    const uint32_t size = NSSwapLittleIntToHost(moduleData->size);
+
+    // sparse entry in the table -- module does not exist or is contained in the startup section
+    if (size == 0) {
       return;
     }
 
-    __weak RCTJSCExecutor *weakSelf = self;
-    self.context.context[@"nativeRequire"] = ^(NSNumber *moduleID) {
-      RCTJSCExecutor *strongSelf = weakSelf;
-      if (!strongSelf || !moduleID) {
-        return;
-      }
+    [_performanceLogger addValue:size forTag:RCTPLRAMNativeRequiresSize];
+    executeRandomAccessModule(self, ID, NSSwapLittleIntToHost(moduleData->offset), size);
+  }
 
-      [strongSelf->_performanceLogger addValue:1 forTag:RCTPLRAMNativeRequiresCount];
-      [strongSelf->_performanceLogger appendStartForTag:RCTPLRAMNativeRequires];
-      RCT_PROFILE_BEGIN_EVENT(RCTProfileTagAlways,
-                              [@"nativeRequire_" stringByAppendingFormat:@"%@", moduleID], nil);
-
-      const uint32_t ID = [moduleID unsignedIntValue];
-
-      if (ID < strongSelf->_randomAccessBundle.numTableEntries) {
-        ModuleData *moduleData = &strongSelf->_randomAccessBundle.table[ID];
-        const uint32_t size = NSSwapLittleIntToHost(moduleData->size);
-
-        // sparse entry in the table -- module does not exist or is contained in the startup section
-        if (size == 0) {
-          return;
-        }
-
-        [strongSelf->_performanceLogger addValue:size forTag:RCTPLRAMNativeRequiresSize];
-        executeRandomAccessModule(strongSelf, ID, NSSwapLittleIntToHost(moduleData->offset), size);
-      }
-
-      RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"js_call", nil);
-      [strongSelf->_performanceLogger appendStopForTag:RCTPLRAMNativeRequires];
-    };
-}];
+  RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"js_call", nil);
+  [_performanceLogger appendStopForTag:RCTPLRAMNativeRequires];
 }
 
 static RandomAccessBundleStartupCode readRAMBundle(file_ptr bundle, RandomAccessBundleData &randomAccessBundle)