Bug 1495072 - Part 2: Add pref for the await fix. r=arai

Differential Revision: https://phabricator.services.mozilla.com/D24255

--HG--
extra : moz-landing-system : lando

js/public/RealmOptions.h

@@ -146,6 +146,12 @@ class JS_PUBLIC_API RealmCreationOptions {
     return *this;
   }
 
+  bool getAwaitFixEnabled() const { return awaitFix_; }
+  RealmCreationOptions& setAwaitFixEnabled(bool flag) {
+    awaitFix_ = flag;
+    return *this;
+  }
+
   // This flag doesn't affect JS engine behavior.  It is used by Gecko to
   // mark whether content windows and workers are "Secure Context"s. See
   // https://w3c.github.io/webappsec-secure-contexts/
@@ -177,6 +183,7 @@ class JS_PUBLIC_API RealmCreationOptions {
   bool streams_ = false;
   bool bigint_ = false;
   bool fields_ = false;
+  bool awaitFix_ = false;
   bool secureContext_ = false;
   bool clampAndJitterTime_ = true;
 };

js/src/fuzz-tests/tests.cpp

@@ -45,7 +45,8 @@ static JSObject* jsfuzz_createGlobal(JSContext* cx, JSPrincipals* principals) {
   options.creationOptions()
       .setStreamsEnabled(true)
       .setBigIntEnabled(true)
-      .setFieldsEnabled(false);
+      .setFieldsEnabled(false)
+      .setAwaitFixEnabled(true);
   newGlobal = JS_NewGlobalObject(cx, getGlobalClass(), principals,
                                  JS::FireOnNewGlobalHook, options);
   if (!newGlobal) {

js/src/jsapi-tests/tests.cpp

@@ -82,7 +82,8 @@ JSObject* JSAPITest::createGlobal(JSPrincipals* principals) {
   options.creationOptions()
       .setStreamsEnabled(true)
       .setBigIntEnabled(true)
-      .setFieldsEnabled(true);
+      .setFieldsEnabled(true)
+      .setAwaitFixEnabled(true);
   newGlobal = JS_NewGlobalObject(cx, getGlobalClass(), principals,
                                  JS::FireOnNewGlobalHook, options);
   if (!newGlobal) {

js/src/shell/js.cpp

@@ -505,6 +505,7 @@ static bool enableAsyncStacks = false;
 static bool enableStreams = false;
 static bool enableBigInt = false;
 static bool enableFields = false;
+static bool enableAwaitFix = false;
 #ifdef JS_GC_ZEAL
 static uint32_t gZealBits = 0;
 static uint32_t gZealFrequency = 0;
@@ -3766,7 +3767,8 @@ static void SetStandardRealmOptions(JS::RealmOptions& options) {
       .setSharedMemoryAndAtomicsEnabled(enableSharedMemory)
       .setBigIntEnabled(enableBigInt)
       .setStreamsEnabled(enableStreams)
-      .setFieldsEnabled(enableFields);
+      .setFieldsEnabled(enableFields)
+      .setAwaitFixEnabled(enableAwaitFix);
 }
 
 static MOZ_MUST_USE bool CheckRealmOptions(JSContext* cx,
@@ -10163,6 +10165,7 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   enableStreams = !op.getBoolOption("no-streams");
   enableBigInt = !op.getBoolOption("no-bigint");
   enableFields = op.getBoolOption("enable-experimental-fields");
+  enableAwaitFix = op.getBoolOption("enable-experimental-await-fix");
 
   JS::ContextOptionsRef(cx)
       .setBaseline(enableBaseline)
@@ -10876,6 +10879,8 @@ int main(int argc, char** argv, char** envp) {
       !op.addBoolOption('\0', "no-bigint", "Disable BigInt support") ||
       !op.addBoolOption('\0', "enable-experimental-fields",
                         "Enable fields in classes") ||
+      !op.addBoolOption('\0', "enable-experimental-await-fix",
+                        "Enable new, faster await semantics") ||
       !op.addStringOption('\0', "shared-memory", "on/off",
                           "SharedArrayBuffer and Atomics "
 #if SHARED_MEMORY_DEFAULT

js/xpconnect/src/XPCJSContext.cpp

@@ -761,13 +761,15 @@ static mozilla::Atomic<bool> sSharedMemoryEnabled(false);
 static mozilla::Atomic<bool> sStreamsEnabled(false);
 static mozilla::Atomic<bool> sBigIntEnabled(false);
 static mozilla::Atomic<bool> sFieldsEnabled(false);
+static mozilla::Atomic<bool> sAwaitFixEnabled(false);
 
 void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
   options.creationOptions()
       .setSharedMemoryAndAtomicsEnabled(sSharedMemoryEnabled)
       .setBigIntEnabled(sBigIntEnabled)
       .setStreamsEnabled(sStreamsEnabled)
-      .setFieldsEnabled(sFieldsEnabled);
+      .setFieldsEnabled(sFieldsEnabled)
+      .setAwaitFixEnabled(sAwaitFixEnabled);
 }
 
 static void ReloadPrefsCallback(const char* pref, XPCJSContext* xpccx) {
@@ -848,6 +850,8 @@ static void ReloadPrefsCallback(const char* pref, XPCJSContext* xpccx) {
   sStreamsEnabled = Preferences::GetBool(JS_OPTIONS_DOT_STR "streams");
   sFieldsEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.fields");
+  sAwaitFixEnabled =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.await_fix");
 
 #ifdef DEBUG
   sExtraWarningsForSystemJS =

modules/libpref/init/StaticPrefList.h

@@ -1156,6 +1156,12 @@ VARCACHE_PREF(
   RelaxedAtomicBool, false
 )
 
+VARCACHE_PREF(
+  "javascript.options.experimental.await_fix",
+   javascript_options_experimental_await_fix,
+  RelaxedAtomicBool, false
+)
+
 
 //---------------------------------------------------------------------------
 // Media prefs

modules/libpref/init/all.js

@@ -1606,6 +1606,8 @@ pref("javascript.options.bigint", false);
 
 pref("javascript.options.experimental.fields", false);
 
+pref("javascript.options.experimental.await_fix", false);
+
 // Dynamic module import.
 pref("javascript.options.dynamicImport", true);