Bug 1840424 - Part 2: Add a one element cache for time zone objects. r=spidermonkey-reviewers,dminor

In addition to caching the default time zone, also add a one element cache for
named time zones. A one element cache is enough for simple test cases like in
bug 1961480.

Differential Revision: https://phabricator.services.mozilla.com/D255271

Author: anba

js/src/builtin/intl/GlobalIntlData.cpp

@@ -273,6 +273,33 @@ temporal::TimeZoneObject* js::intl::GlobalIntlData::getOrCreateDefaultTimeZone(
   return &defaultTimeZoneObject_->as<temporal::TimeZoneObject>();
 }
 
+temporal::TimeZoneObject* js::intl::GlobalIntlData::getOrCreateTimeZone(
+    JSContext* cx, Handle<JSLinearString*> identifier,
+    Handle<JSLinearString*> primaryIdentifier) {
+  // If there's a cached time zone, check if the identifiers are equal.
+  if (timeZoneObject_) {
+    auto* timeZone = &timeZoneObject_->as<temporal::TimeZoneObject>();
+    if (EqualStrings(timeZone->identifier(), identifier)) {
+      // Primary identifier must match when the identifiers are equal.
+      MOZ_ASSERT(
+          EqualStrings(timeZone->primaryIdentifier(), primaryIdentifier));
+
+      // Return the cached time zone.
+      return timeZone;
+    }
+  }
+
+  // If we didn't have a cache hit, create a new time zone.
+  auto* timeZone =
+      temporal::CreateTimeZoneObject(cx, identifier, primaryIdentifier);
+  if (!timeZone) {
+    return nullptr;
+  }
+  timeZoneObject_ = timeZone;
+
+  return &timeZone->as<temporal::TimeZoneObject>();
+}
+
 void js::intl::GlobalIntlData::trace(JSTracer* trc) {
   TraceNullableEdge(trc, &runtimeDefaultLocale_,
                     "GlobalIntlData::runtimeDefaultLocale_");
@@ -283,6 +310,7 @@ void js::intl::GlobalIntlData::trace(JSTracer* trc) {
   TraceNullableEdge(trc, &defaultTimeZone_, "GlobalIntlData::defaultTimeZone_");
   TraceNullableEdge(trc, &defaultTimeZoneObject_,
                     "GlobalIntlData::defaultTimeZoneObject_");
+  TraceNullableEdge(trc, &timeZoneObject_, "GlobalIntlData::timeZoneObject_");
 
   TraceNullableEdge(trc, &collatorLocale_, "GlobalIntlData::collatorLocale_");
   TraceNullableEdge(trc, &collator_, "GlobalIntlData::collator_");

js/src/builtin/intl/GlobalIntlData.h

@@ -63,6 +63,12 @@ class GlobalIntlData {
    */
   GCPtr<JSObject*> defaultTimeZoneObject_;
 
+  /**
+   * Cached temporal::TimeZoneObject of the last request to create a named
+   * time zone.
+   */
+  GCPtr<JSObject*> timeZoneObject_;
+
   /**
    * Locale string passed to the last call to localeCompare String method. Not
    * necessarily the actual locale when the string can't be resolved to a
@@ -137,6 +143,16 @@ class GlobalIntlData {
    */
   temporal::TimeZoneObject* getOrCreateDefaultTimeZone(JSContext* cx);
 
+  /**
+   * Get or create the time zone for the IANA time zone name |identifier|.
+   * |primaryIdentifier| must be the primary identifier for |identifier|, i.e.
+   * if |identifier| is a time zone link name, |primaryIdentifier| must be the
+   * link's target time zone.
+   */
+  temporal::TimeZoneObject* getOrCreateTimeZone(
+      JSContext* cx, JS::Handle<JSLinearString*> identifier,
+      JS::Handle<JSLinearString*> primaryIdentifier);
+
   /**
    * Get or create the Intl.Collator instance for |locale|. The default locale
    * is used when |locale| is null.

js/src/builtin/temporal/TimeZone.cpp

@@ -101,8 +101,6 @@ static JSLinearString* FormatOffsetTimeZoneIdentifier(JSContext* cx,
 TimeZoneObject* js::temporal::CreateTimeZoneObject(
     JSContext* cx, Handle<JSLinearString*> identifier,
     Handle<JSLinearString*> primaryIdentifier) {
-  // TODO: Implement a built-in time zone object cache.
-
   auto* object = NewObjectWithGivenProto<TimeZoneObject>(cx, nullptr);
   if (!object) {
     return nullptr;
@@ -119,6 +117,13 @@ TimeZoneObject* js::temporal::CreateTimeZoneObject(
   return object;
 }
 
+static TimeZoneObject* GetOrCreateTimeZoneObject(
+    JSContext* cx, Handle<JSLinearString*> identifier,
+    Handle<JSLinearString*> primaryIdentifier) {
+  return cx->global()->globalIntlData().getOrCreateTimeZone(cx, identifier,
+                                                            primaryIdentifier);
+}
+
 static TimeZoneObject* CreateTimeZoneObject(JSContext* cx,
                                             int32_t offsetMinutes) {
   // TODO: It's unclear if offset time zones should also be cached. Real world
@@ -687,7 +692,7 @@ bool js::temporal::ToTemporalTimeZone(JSContext* cx,
   }
 
   // Step 9.
-  auto* obj = CreateTimeZoneObject(cx, identifier, primaryIdentifier);
+  auto* obj = GetOrCreateTimeZoneObject(cx, identifier, primaryIdentifier);
   if (!obj) {
     return false;
   }
@@ -1169,7 +1174,7 @@ bool js::temporal::WrapTimeZoneValueObject(
   }
 
   auto* obj =
-      CreateTimeZoneObject(cx, identifierLinear, primaryIdentifierLinear);
+      GetOrCreateTimeZoneObject(cx, identifierLinear, primaryIdentifierLinear);
   if (!obj) {
     return false;
   }