From 932ed2e364276e97f48acb6abfe9341be885ccc5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=96mer=20Sinan=20A=C4=9Facan?= <omersa@google.com>
Date: Tue, 14 Nov 2023 11:42:23 +0000
Subject: [PATCH] [dart2wasm] Allocate TextDecoder once when decoding UTF-8 to
 JSStringImpl
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Improves a protobuf decoding benchmark from 348ms to 305ms.

Change-Id: Ib47d4271981c16c196594e435c807fecb8fb02f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/336020
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Ömer Ağacan <omersa@google.com>
---
 pkg/dart2wasm/lib/js/runtime_generator.dart   |  3 +-
 pkg/dart2wasm/lib/target.dart                 |  2 +
 .../lib/convert_patch.dart                    | 61 ++++++++-----------
 3 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/pkg/dart2wasm/lib/js/runtime_generator.dart b/pkg/dart2wasm/lib/js/runtime_generator.dart
index 343d3f67129..d6708e28830 100644
--- a/pkg/dart2wasm/lib/js/runtime_generator.dart
+++ b/pkg/dart2wasm/lib/js/runtime_generator.dart
@@ -35,8 +35,9 @@ JSMethods _performJSInteropTransformations(
       additionalCoreLibraries: {
         '_js_helper',
         '_js_types',
+        'convert',
         'js_interop',
-        'js_interop_unsafe'
+        'js_interop_unsafe',
       });
   for (Library library in interopDependentLibraries) {
     staticInteropClassEraser.visitLibrary(library);
diff --git a/pkg/dart2wasm/lib/target.dart b/pkg/dart2wasm/lib/target.dart
index ff4aec70d1e..d845d0ff36b 100644
--- a/pkg/dart2wasm/lib/target.dart
+++ b/pkg/dart2wasm/lib/target.dart
@@ -251,6 +251,8 @@ class WasmTarget extends Target {
           component, Uri.parse("dart:_js_annotations")),
       ...?jsInteropHelper.calculateTransitiveImportsOfJsInteropIfUsed(
           component, Uri.parse("dart:js_interop")),
+      ...?jsInteropHelper.calculateTransitiveImportsOfJsInteropIfUsed(
+          component, Uri.parse("dart:convert")),
     };
     if (transitiveImportingJSInterop.isEmpty) {
       logger?.call("Skipped JS interop transformations");
diff --git a/sdk/lib/_internal/wasm_js_compatibility/lib/convert_patch.dart b/sdk/lib/_internal/wasm_js_compatibility/lib/convert_patch.dart
index f4fd5876bec..6147ae0fb25 100644
--- a/sdk/lib/_internal/wasm_js_compatibility/lib/convert_patch.dart
+++ b/sdk/lib/_internal/wasm_js_compatibility/lib/convert_patch.dart
@@ -52,30 +52,19 @@ class Utf8Decoder {
 
   static String? _convertInterceptedUint8List(
       bool allowMalformed, JSUint8ArrayImpl codeUnits, int start, int end) {
-    // TODO(omersa): There's a bug somewhere when compiling lazy statics that
-    // return `WasmExternRef`?
-    // final WasmExternRef? decoder = allowMalformed ? _decoderNonfatal : _decoder;
-    // if (decoder == WasmExternRef.nullRef) {
-    //   return null;
-    // }
-    final WasmExternRef? decoder;
-    try {
-      decoder = allowMalformed
-          ? js.JS<WasmExternRef?>(
-              '() => new TextDecoder("utf-8", {fatal: false})')
-          : js.JS<WasmExternRef?>(
-              '() => new TextDecoder("utf-8", {fatal: true})');
-    } catch (e) {
+    final JSAny? decoder = allowMalformed ? _decoderNonFatal : _decoder;
+    if (decoder == null) {
       return null;
     }
 
     if (0 == start && end == codeUnits.length) {
-      return _useTextDecoder(decoder, codeUnits.toJSArrayExternRef());
+      return _useTextDecoder(
+          externRefForJSAny(decoder), codeUnits.toJSArrayExternRef());
     }
     RangeError.checkValidRange(start, end, codeUnits.length);
     final length = end - start;
-    return _useTextDecoder(
-        decoder, codeUnits.toJSArrayExternRef(start, length));
+    return _useTextDecoder(externRefForJSAny(decoder),
+        codeUnits.toJSArrayExternRef(start, length));
   }
 
   static String? _useTextDecoder(
@@ -92,26 +81,28 @@ class Utf8Decoder {
     return null;
   }
 
-  // TODO(omersa): These values seem to be miscompiled at the use sites, see
-  // above.
+  // TextDecoder is not defined on some browsers and on the stand-alone d8 and
+  // jsshell engines. Use a lazy initializer to do feature detection once.
   //
-  // // TextDecoder is not defined on some browsers and on the stand-alone d8 and
-  // // jsshell engines. Use a lazy initializer to do feature detection once.
-  // static final WasmExternRef? _decoder = () {
-  //   try {
-  //     return js
-  //         .JS<WasmExternRef?>('() => new TextDecoder("utf-8", {fatal: true})');
-  //   } catch (e) {}
-  //   return null;
-  // }();
+  // Globls need to return boxed Dart values, so these return `JSAny?` instead
+  // of `WasmExternRef?`.
+  static final JSAny? _decoder = () {
+    try {
+      return js
+          .JS<WasmExternRef>('() => new TextDecoder("utf-8", {fatal: true})')
+          .toJS;
+    } catch (e) {}
+    return null;
+  }();
 
-  // static final WasmExternRef? _decoderNonfatal = () {
-  //   try {
-  //     return js
-  //         .JS<WasmExternRef?>('() => new TextDecoder("utf-8", {fatal: false})');
-  //   } catch (e) {}
-  //   return null;
-  // }();
+  static final JSAny? _decoderNonFatal = () {
+    try {
+      return js
+          .JS<WasmExternRef>('() => new TextDecoder("utf-8", {fatal: false})')
+          .toJS;
+    } catch (e) {}
+    return null;
+  }();
 }
 
 //// Implementation ///////////////////////////////////////////////////////////