Bug 1364118 - List JS bytecode cache preferences in all.js. r=mrbkap

dom/base/test/test_script_loader_js_cache.html

@@ -116,14 +116,14 @@
       // trace these and resolve a promise with the path taken by the
       // script loader.
       //
-      // Setting dom.script_loader.force_bytecode_cache causes the
+      // Setting dom.script_loader.bytecode_cache.eager causes the
       // nsScriptLoadRequest to force all the conditions necessary to make a
       // script be saved as bytecode in the alternate data storage provided
       // by the channel (necko cache).
       await SpecialPowers.pushPrefEnv({set: [
         ['dom.script_loader.bytecode_cache.enabled', true],
         ['dom.expose_test_interfaces', true],
-        ['dom.script_loader.force_bytecode_cache', true]
+        ['dom.script_loader.bytecode_cache.eager', true]
       ]});
 
       // Load the test page, and verify that the code path taken by the
@@ -174,7 +174,7 @@
       await SpecialPowers.pushPrefEnv({set: [
         ['dom.script_loader.bytecode_cache.enabled', true],
         ['dom.expose_test_interfaces', true],
-        ['dom.script_loader.force_bytecode_cache', true]
+        ['dom.script_loader.bytecode_cache.eager', true]
       ]});
 
       // The test page add a new script which generate a "ping" event, which

dom/script/ScriptLoader.cpp

@@ -818,6 +818,21 @@ ScriptLoader::IsBytecodeCacheEnabled()
   return sExposeTestInterfaceEnabled;
 }
 
+/* static */ bool
+ScriptLoader::IsEagerBytecodeCache()
+{
+  // When testing, we want to force use of the bytecode cache.
+  static bool sEagerBytecodeCache = false;
+  static bool sForceBytecodeCachePrefCached = false;
+  if (!sForceBytecodeCachePrefCached) {
+    sForceBytecodeCachePrefCached = true;
+    Preferences::AddBoolVarCache(&sEagerBytecodeCache,
+                                 "dom.script_loader.bytecode_cache.eager",
+                                 false);
+  }
+  return sEagerBytecodeCache;
+}
+
 nsresult
 ScriptLoader::RestartLoad(ScriptLoadRequest* aRequest)
 {
@@ -1864,19 +1879,10 @@ ScriptLoader::FillCompileOptionsForRequest(const AutoJSAPI&jsapi,
     aOptions->setElement(&elementVal.toObject());
   }
 
-  // When testing, we want to force use of the bytecode cache.
-  static bool sForceBytecodeCacheEnabled = false;
-  static bool sForceBytecodeCachePrefCached = false;
-  if (!sForceBytecodeCachePrefCached) {
-    sForceBytecodeCachePrefCached = true;
-    Preferences::AddBoolVarCache(&sForceBytecodeCacheEnabled,
-                                 "dom.script_loader.force_bytecode_cache",
-                                 false);
-  }
   // At the moment, the bytecode cache is only triggered if a script is large
   // enough to be parsed out of the main thread.  Thus, for testing purposes, we
   // force parsing any script out of the main thread.
-  if (sForceBytecodeCacheEnabled) {
+  if (IsEagerBytecodeCache()) {
     aOptions->forceAsync = true;
   }
 

dom/script/ScriptLoader.h

@@ -471,6 +471,9 @@ private:
   static bool
   IsBytecodeCacheEnabled();
 
+  static bool
+  IsEagerBytecodeCache();
+
   nsresult CreateModuleScript(ModuleLoadRequest* aRequest);
   nsresult ProcessFetchedModuleSource(ModuleLoadRequest* aRequest);
   void ProcessLoadedModuleTree(ModuleLoadRequest* aRequest);

modules/libpref/init/all.js

@@ -209,6 +209,16 @@ pref("dom.keyboardevent.dispatch_during_composition", false);
 // significantly increase the number of compartments in the system.
 pref("dom.compartment_per_addon", true);
 
+// Whether to enable the JavaScript start-up cache. This causes one of the first
+// execution to record the bytecode of the JavaScript function used, and save it
+// in the existing cache entry. On the following loads of the same script, the
+// bytecode would be loaded from the cache instead of being generated once more.
+pref("dom.script_loader.bytecode_cache.enabled", false); // Not tuned yet.
+
+// Ignore the heuristics of the bytecode cache, and always record on the first
+// visit. (used for testing purposes).
+pref("dom.script_loader.bytecode_cache.eager", false);
+
 // Fastback caching - if this pref is negative, then we calculate the number
 // of content viewers to cache based on the amount of available memory.
 pref("browser.sessionhistory.max_total_viewers", -1);