From 1d625e01f3afc348bf016395700211b7f8d8175e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9=20Bargull?= <andre.bargull@gmail.com>
Date: Wed, 24 Jan 2024 09:57:02 +0000
Subject: [PATCH] Bug 1874373 - Part 2: Call String.p.codePointAt in
 StringIteratorNext. r=jandem

Directly call `String.p.codePointAt` instead of manually computing the code
point in `StringIteratorNext`.

Depends on D198360

Differential Revision: https://phabricator.services.mozilla.com/D199350
---
 js/src/builtin/String.cpp |  2 +-
 js/src/builtin/String.h   |  2 ++
 js/src/builtin/String.js  | 14 +++-----------
 js/src/vm/SelfHosting.cpp |  2 ++
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/js/src/builtin/String.cpp b/js/src/builtin/String.cpp
index 957c3f8d409cf..d815e6462f394 100644
--- a/js/src/builtin/String.cpp
+++ b/js/src/builtin/String.cpp
@@ -1893,7 +1893,7 @@ bool js::str_charCodeAt(JSContext* cx, unsigned argc, Value* vp) {
  *
  * ES2024 draft rev 7d2644968bd56d54d2886c012d18698ff3f72c35
  */
-static bool str_codePointAt(JSContext* cx, unsigned argc, Value* vp) {
+bool js::str_codePointAt(JSContext* cx, unsigned argc, Value* vp) {
   AutoJSMethodProfilerEntry pseudoFrame(cx, "String.prototype", "codePointAt");
   CallArgs args = CallArgsFromVp(argc, vp);
 
diff --git a/js/src/builtin/String.h b/js/src/builtin/String.h
index 0262af36e0a37..556bc92488e30 100644
--- a/js/src/builtin/String.h
+++ b/js/src/builtin/String.h
@@ -36,6 +36,8 @@ extern bool str_toString(JSContext* cx, unsigned argc, Value* vp);
 
 extern bool str_charCodeAt(JSContext* cx, unsigned argc, Value* vp);
 
+extern bool str_codePointAt(JSContext* cx, unsigned argc, Value* vp);
+
 extern bool str_endsWith(JSContext* cx, unsigned argc, Value* vp);
 
 #if JS_HAS_INTL_API
diff --git a/js/src/builtin/String.js b/js/src/builtin/String.js
index 822b7f0741354..864c6ad588ec2 100644
--- a/js/src/builtin/String.js
+++ b/js/src/builtin/String.js
@@ -819,20 +819,12 @@ function StringIteratorNext() {
     return result;
   }
 
-  var charCount = 1;
-  var first = callFunction(std_String_charCodeAt, S, index);
-  if (first >= 0xd800 && first <= 0xdbff && index + 1 < size) {
-    var second = callFunction(std_String_charCodeAt, S, index + 1);
-    if (second >= 0xdc00 && second <= 0xdfff) {
-      first = (first - 0xd800) * 0x400 + (second - 0xdc00) + 0x10000;
-      charCount = 2;
-    }
-  }
+  var codePoint = callFunction(std_String_codePointAt, S, index);
+  var charCount = 1 + (codePoint > 0xffff);
 
   UnsafeSetReservedSlot(obj, ITERATOR_SLOT_NEXT_INDEX, index + charCount);
 
-  // Communicate |first|'s possible range to the compiler.
-  result.value = callFunction(std_String_fromCodePoint, null, first & 0x1fffff);
+  result.value = callFunction(std_String_fromCodePoint, null, codePoint);
 
   return result;
 }
diff --git a/js/src/vm/SelfHosting.cpp b/js/src/vm/SelfHosting.cpp
index ccba11f65bef7..4fcb6f5ae2708 100644
--- a/js/src/vm/SelfHosting.cpp
+++ b/js/src/vm/SelfHosting.cpp
@@ -2299,6 +2299,8 @@ static const JSFunctionSpec intrinsic_functions[] = {
     JS_FN("std_Set_values", SetObject::values, 0, 0),
     JS_INLINABLE_FN("std_String_charCodeAt", str_charCodeAt, 1, 0,
                     StringCharCodeAt),
+    JS_INLINABLE_FN("std_String_codePointAt", str_codePointAt, 1, 0,
+                    StringCodePointAt),
     JS_INLINABLE_FN("std_String_endsWith", str_endsWith, 1, 0, StringEndsWith),
     JS_INLINABLE_FN("std_String_fromCharCode", str_fromCharCode, 1, 0,
                     StringFromCharCode),