From aca09cae0aafec394be0492bb78e0463ebb874e3 Mon Sep 17 00:00:00 2001
From: Philip Chimento <pchimento@igalia.com>
Date: Fri, 16 Apr 2021 14:36:21 -0700
Subject: [PATCH] Short-circuit common case of comparing a calendar or time
 zone to itself

In CalendarEquals, TimeZoneEquals, and ConsolidateCalendars, remove the
observable toString() calls from the path where both calendars are the
same object.

See: #1425
---
 polyfill/lib/ecmascript.mjs |  3 +++
 spec/calendar.html          | 12 ++++++++++++
 spec/timezone.html          |  6 ++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/polyfill/lib/ecmascript.mjs b/polyfill/lib/ecmascript.mjs
index db9183ecbb..9010541866 100644
--- a/polyfill/lib/ecmascript.mjs
+++ b/polyfill/lib/ecmascript.mjs
@@ -1869,11 +1869,13 @@ export const ES = ObjectAssign({}, ES2020, {
     return cal1 < cal2 ? -1 : cal1 > cal2 ? 1 : 0;
   },
   CalendarEquals: (one, two) => {
+    if (one === two) return true;
     const cal1 = ES.ToString(one);
     const cal2 = ES.ToString(two);
     return cal1 === cal2;
   },
   ConsolidateCalendars: (one, two) => {
+    if (one === two) return two;
     const sOne = ES.ToString(one);
     const sTwo = ES.ToString(two);
     if (sOne === sTwo || sOne === 'iso8601') {
@@ -1918,6 +1920,7 @@ export const ES = ObjectAssign({}, ES2020, {
     return new TemporalTimeZone(timeZone);
   },
   TimeZoneEquals: (one, two) => {
+    if (one === two) return true;
     const tz1 = ES.ToString(one);
     const tz2 = ES.ToString(two);
     return tz1 === tz2;
diff --git a/spec/calendar.html b/spec/calendar.html
index 64334ab295..9f5a8c8a48 100644
--- a/spec/calendar.html
+++ b/spec/calendar.html
@@ -328,7 +328,13 @@ <h1>FormatCalendarAnnotation ( _id_, _showCalendar_ )</h1>
 
     <emu-clause id="sec-temporal-calendarequals" aoid="CalendarEquals">
       <h1>CalendarEquals ( _one_, _two_ )</h1>
+      <p>
+        The abstract operation CalendarEquals takes two arguments _one_ and _two_, which must be Objects.
+        It returns *true* if its arguments represent the same calendar.
+        It performs the following steps:
+      </p>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return *true*.
         1. Let _calendarOne_ be ? ToString(_one_).
         1. Let _calendarTwo_ be ? ToString(_two_).
         1. If _calendarOne_ is _calendarTwo_, return *true*.
@@ -338,7 +344,13 @@ <h1>CalendarEquals ( _one_, _two_ )</h1>
 
     <emu-clause id="sec-temporal-consolidatecalendars" aoid="ConsolidateCalendars">
       <h1>ConsolidateCalendars ( _one_, _two_ )</h1>
+      <p>
+        The abstract operation ConsolidateCalendars takes two arguments _one_ and _two_, which must be Objects.
+        It returns the calendar that should take priority when combining two Temporal objects with different calendars, or throws an exception if the calendars cannot be combined.
+        It performs the following steps:
+      </p>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return _two_.
         1. Let _calendarOne_ be ? ToString(_one_).
         1. Let _calendarTwo_ be ? ToString(_two_).
         1. If _calendarOne_ is _calendarTwo_, return _two_.
diff --git a/spec/timezone.html b/spec/timezone.html
index d0d96ff562..00b14e5976 100644
--- a/spec/timezone.html
+++ b/spec/timezone.html
@@ -644,10 +644,12 @@ <h1>GetPossibleInstantsFor ( _timeZone_, _dateTime_ )</h1>
     <emu-clause id="sec-temporal-timezoneequals" aoid="TimeZoneEquals">
       <h1>TimeZoneEquals ( _one_, _two_ )</h1>
       <p>
-        The abstract operation TimeZoneEquals returns *true* if the results of
-        calling `toString()` on its arguments are equal.
+        The abstract operation TimeZoneEquals takes two arguments _one_ and _two_, which must be Objects.
+        It returns *true* if its arguments represent the same time zone.
+        It performs the following steps:
       </p>
       <emu-alg>
+        1. If _one_ and _two_ are the same Object value, return *true*.
         1. Let _timeZoneOne_ be ? ToString(_one_).
         1. Let _timeZoneTwo_ be ? ToString(_two_).
         1. If _timeZoneOne_ is _timeZoneTwo_, return *true*.