[dart2wasm] Implement jsifyRaw() of Dart lists in Dart

Currently `jsifyRaw()` on a Dart list calls out to JS which allocates an
array and then calls back into Dart for each array element, which uses
`jsifyRaw()` on the array elements.

The JS runtimes will not inline the call back into Dart. So there's
actually very little reason to do this in JS, so we can implement it in
Dart.

That in return will also make this more ammenable to tree shaking as the
`$listRead` and `$listLenght` aren't force-exported anymore.

Change-Id: I8b3b7f553ce9fa72880f6ca08edb95b900e98570
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/414781
Reviewed-by: Srujan Gaddam <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

pkg/dart2wasm/lib/js/runtime_blob.dart

@@ -72,19 +72,6 @@ class CompiledApp {
       throw "Unable to print message: " + js;
     }
 
-    // Converts a Dart List to a JS array. Any Dart objects will be converted, but
-    // this will be cheap for JSValues.
-    function arrayFromDartList(constructor, list) {
-      const exports = dartInstance.exports;
-      const read = exports.$listRead;
-      const length = exports.$listLength(list);
-      const array = new constructor(length);
-      for (let i = 0; i < length; i++) {
-        array[i] = read(list, i);
-      }
-      return array;
-    }
-
     // A special symbol attached to functions that wrap Dart functions.
     const jsWrappedDartFunctionSymbol = Symbol("JSWrappedDartFunction");
 

sdk/lib/_internal/wasm/lib/js_helper.dart

@@ -256,8 +256,14 @@ external WasmExternRef jsFloat64ArrayFromDartFloat64List(Float64List l);
 
 external WasmExternRef jsDataViewFromDartByteData(ByteData data, int length);
 
-WasmExternRef? jsArrayFromDartList(List<Object?> l) =>
-    JS<WasmExternRef?>('l => arrayFromDartList(Array, l)', l);
+WasmExternRef? _jsifyRawList(List<Object?> list) {
+  final length = list.length;
+  final result = JSArray<JSAny?>.withLength(length);
+  for (int i = 0; i < length; i++) {
+    result[i] = JSValue.box(jsifyRaw(list[i])) as JSAny?;
+  }
+  return (result as JSValue).toExternRef;
+}
 
 external JSStringImpl jsStringFromDartString(String s);
 external String jsStringToDartString(JSStringImpl s);
@@ -369,7 +375,7 @@ WasmExternRef? jsifyRaw(Object? o) {
     if (o is js_types.JSDataViewImpl) return o.toExternRef;
     if (o is ByteData) return jsDataViewFromDartByteData(o, o.lengthInBytes);
   } else if (o is List<Object?>) {
-    return jsArrayFromDartList(o);
+    return _jsifyRawList(o);
   } else if (o is ByteBuffer) {
     if (o is js_types.JSArrayBufferImpl) return o.toExternRef;
     return jsArrayBufferFromDartByteBuffer(o);
@@ -672,16 +678,3 @@ external T JS<T>(
   arg18,
   arg19,
 ]);
-
-/// Methods used by the wasm runtime.
-@pragma("wasm:export", "\$listLength")
-WasmI32 _listLength(WasmExternRef? ref) =>
-    unsafeCastOpaque<List>(
-      unsafeCast<WasmExternRef>(ref).internalize(),
-    ).length.toWasmI32();
-
-@pragma("wasm:export", "\$listRead")
-WasmExternRef? _listRead(WasmExternRef? ref, WasmI32 index) => jsifyRaw(
-  unsafeCastOpaque<List>(unsafeCast<WasmExternRef>(ref).internalize())[index
-      .toIntSigned()],
-);