Bug 1662140 - Add javascript.options.off_thread_parse_global pref and --no-off-thread-parse-global shell option. r=tcampbell

This adds the preference, JS shell option, and {ContextOptions,CompileOptions} fields,
but the value isn't read and the code always acts as it's set to true.

Differential Revision: https://phabricator.services.mozilla.com/D88922

dom/workers/RuntimeService.cpp

@@ -290,7 +290,9 @@ void LoadContextOptions(const char* aPrefName, void* /* aClosure */) {
       .setPrivateClassFields(
           GetWorkerPref<bool>("experimental.private_fields"_ns))
       .setPrivateClassMethods(
-          GetWorkerPref<bool>("experimental.private_methods"_ns));
+          GetWorkerPref<bool>("experimental.private_methods"_ns))
+      .setUseOffThreadParseGlobal(
+          GetWorkerPref<bool>("off_thread_parse_global"_ns));
 
   nsCOMPtr<nsIXULRuntime> xr = do_GetService("@mozilla.org/xre/runtime;1");
   if (xr) {

js/public/CompileOptions.h

@@ -133,6 +133,11 @@ class JS_PUBLIC_API TransitiveCompileOptions {
   bool privateClassFields = false;
   bool privateClassMethods = false;
 
+  // True if off-thread parsing should use a parse GlobalObject in order to
+  // directly allocate to the GC from a helper thread. If false, transfer the
+  // CompilationStencil back to main thread before allocating GC objects.
+  bool useOffThreadParseGlobal = true;
+
   /**
    * |introductionType| is a statically allocated C string: one of "eval",
    * "Function", or "GeneratorFunction".

js/public/ContextOptions.h

@@ -45,7 +45,8 @@ class JS_PUBLIC_API ContextOptions {
 #endif
         fuzzing_(false),
         privateClassFields_(false),
-        privateClassMethods_(false) {
+        privateClassMethods_(false),
+        useOffThreadParseGlobal_(true) {
   }
 
   bool asmJS() const { return asmJS_; }
@@ -153,6 +154,12 @@ class JS_PUBLIC_API ContextOptions {
     return *this;
   }
 
+  bool useOffThreadParseGlobal() const { return useOffThreadParseGlobal_; }
+  ContextOptions& setUseOffThreadParseGlobal(bool use) {
+    useOffThreadParseGlobal_ = use;
+    return *this;
+  }
+
   // Override to allow disabling the eval restriction security checks for
   // this context.
   bool disableEvalSecurityChecks() const { return disableEvalSecurityChecks_; }
@@ -262,6 +269,9 @@ class JS_PUBLIC_API ContextOptions {
   bool fuzzing_ : 1;
   bool privateClassFields_ : 1;
   bool privateClassMethods_ : 1;
+
+  // See TransitiveCompileOptions.useOffThreadParseGlobal.
+  bool useOffThreadParseGlobal_ : 1;
 };
 
 JS_PUBLIC_API ContextOptions& ContextOptionsRef(JSContext* cx);

js/src/builtin/TestingFunctions.cpp

@@ -175,6 +175,13 @@ static bool GetRealmConfiguration(JSContext* cx, unsigned argc, Value* vp) {
     return false;
   }
 
+  bool offThreadParseGlobal = cx->options().useOffThreadParseGlobal();
+  if (!JS_SetProperty(
+          cx, info, "offThreadParseGlobal",
+          offThreadParseGlobal ? TrueHandleValue : FalseHandleValue)) {
+    return false;
+  }
+
   args.rval().setObject(*info);
   return true;
 }

js/src/jsapi.cpp

@@ -3466,6 +3466,7 @@ void JS::TransitiveCompileOptions::copyPODTransitiveOptions(
   nonSyntacticScope = rhs.nonSyntacticScope;
   privateClassFields = rhs.privateClassFields;
   privateClassMethods = rhs.privateClassMethods;
+  useOffThreadParseGlobal = rhs.useOffThreadParseGlobal;
 };
 
 void JS::ReadOnlyCompileOptions::copyPODNonTransitiveOptions(
@@ -3559,6 +3560,7 @@ JS::CompileOptions::CompileOptions(JSContext* cx)
       cx->options().throwOnAsmJSValidationFailure();
   privateClassFields = cx->options().privateClassFields();
   privateClassMethods = cx->options().privateClassMethods();
+  useOffThreadParseGlobal = cx->options().useOffThreadParseGlobal();
 
   sourcePragmas_ = cx->options().sourcePragmas();
 

js/src/shell/js.cpp

@@ -521,6 +521,7 @@ bool shell::enablePropertyErrorMessageFix = false;
 bool shell::enableIteratorHelpers = false;
 bool shell::enablePrivateClassFields = false;
 bool shell::enablePrivateClassMethods = false;
+bool shell::useOffThreadParseGlobal = true;
 #ifdef JS_GC_ZEAL
 uint32_t shell::gZealBits = 0;
 uint32_t shell::gZealFrequency = 0;
@@ -10251,6 +10252,7 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   enablePrivateClassFields = op.getBoolOption("enable-private-fields") ||
                              op.getBoolOption("enable-private-methods");
   enablePrivateClassMethods = op.getBoolOption("enable-private-methods");
+  useOffThreadParseGlobal = !op.getBoolOption("no-off-thread-parse-global");
 
   JS::ContextOptionsRef(cx)
       .setAsmJS(enableAsmJS)
@@ -10277,7 +10279,8 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
       .setAsyncStack(enableAsyncStacks)
       .setAsyncStackCaptureDebuggeeOnly(enableAsyncStackCaptureDebuggeeOnly)
       .setPrivateClassFields(enablePrivateClassFields)
-      .setPrivateClassMethods(enablePrivateClassMethods);
+      .setPrivateClassMethods(enablePrivateClassMethods)
+      .setUseOffThreadParseGlobal(useOffThreadParseGlobal);
 
   if (op.getBoolOption("no-ion-for-main-context")) {
     JS::ContextOptionsRef(cx).setDisableIon();
@@ -11143,6 +11146,9 @@ int main(int argc, char** argv, char** envp) {
                         "Enable private class fields") ||
       !op.addBoolOption('\0', "enable-private-methods",
                         "Enable private class methods") ||
+      !op.addBoolOption('\0', "no-off-thread-parse-global",
+                        "Do not use parseGlobal in off-thread compilation and "
+                        "instead instantiate stencil in main-thread") ||
       !op.addStringOption('\0', "shared-memory", "on/off",
                           "SharedArrayBuffer and Atomics "
 #if SHARED_MEMORY_DEFAULT

js/src/shell/jsshell.h

@@ -135,6 +135,7 @@ extern bool enableReadableStreamPipeTo;
 extern bool enableWeakRefs;
 extern bool enableToSource;
 extern bool enablePropertyErrorMessageFix;
+extern bool useOffThreadParseGlobal;
 extern bool enableIteratorHelpers;
 extern bool enablePrivateClassFields;
 extern bool enablePrivateClassMethods;

js/xpconnect/src/XPCJSContext.cpp

@@ -974,6 +974,9 @@ static void ReloadPrefsCallback(const char* pref, void* aXpccx) {
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.private_methods");
 #endif
 
+  bool useOffThreadParseGlobal =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "off_thread_parse_global");
+
 #ifdef JS_GC_ZEAL
   int32_t zeal = Preferences::GetInt(JS_OPTIONS_DOT_STR "gczeal", -1);
   int32_t zeal_frequency = Preferences::GetInt(
@@ -1017,7 +1020,8 @@ static void ReloadPrefsCallback(const char* pref, void* aXpccx) {
       .setThrowOnDebuggeeWouldRun(throwOnDebuggeeWouldRun)
       .setDumpStackOnDebuggeeWouldRun(dumpStackOnDebuggeeWouldRun)
       .setPrivateClassFields(privateFieldsEnabled)
-      .setPrivateClassMethods(privateMethodsEnabled);
+      .setPrivateClassMethods(privateMethodsEnabled)
+      .setUseOffThreadParseGlobal(useOffThreadParseGlobal);
 
   nsCOMPtr<nsIXULRuntime> xr = do_GetService("@mozilla.org/xre/runtime;1");
   if (xr) {

modules/libpref/init/StaticPrefList.yaml

@@ -4995,6 +4995,14 @@
 #endif
   mirror: always
 
+# True if off-thread parsing should use a parse GlobalObject in order to
+# directly allocate to the GC from a helper thread. If false, transfer the
+# CompilationStencil back to main thread before allocating GC objects.
+- name: javascript.options.off_thread_parse_global
+  type: bool
+  value: true
+  mirror: once
+
 #---------------------------------------------------------------------------
 # Prefs starting with "layers."
 #---------------------------------------------------------------------------