[wasm][externref] Support default value for the table constructor

The WebAssembly.Table constructor supports a second parameter that was
not supported by V8 so far.

R=thibaudm@chromium.org

Bug: v8:7581
Change-Id: Id74c53a6b1bde7f49a4edea8397d1cab253e1a0e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3141571
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76660}

src/wasm/wasm-js.cc

@@ -1117,12 +1117,25 @@ void WebAssemblyTable(const v8::FunctionCallbackInfo<v8::Value>& args) {
   }
 
   i::Handle<i::FixedArray> fixed_array;
-  i::Handle<i::JSObject> table_obj =
+  i::Handle<i::WasmTableObject> table_obj =
       i::WasmTableObject::New(i_isolate, i::Handle<i::WasmInstanceObject>(),
                               type, static_cast<uint32_t>(initial), has_maximum,
                               static_cast<uint32_t>(maximum), &fixed_array);
+
+  if (initial > 0 && args.Length() >= 2 && !args[1]->IsUndefined()) {
+    i::Handle<i::Object> element = Utils::OpenHandle(*args[1]);
+    if (!i::WasmTableObject::IsValidElement(i_isolate, table_obj, element)) {
+      thrower.TypeError(
+          "Argument 2 must be undefined, null, or a value of type compatible "
+          "with the type of the new table.");
+      return;
+    }
+    for (uint32_t index = 0; index < static_cast<uint32_t>(initial); ++index) {
+      i::WasmTableObject::Set(i_isolate, table_obj, index, element);
+    }
+  }
   v8::ReturnValue<v8::Value> return_value = args.GetReturnValue();
-  return_value.Set(Utils::ToLocal(table_obj));
+  return_value.Set(Utils::ToLocal(i::Handle<i::JSObject>::cast(table_obj)));
 }
 
 void WebAssemblyMemory(const v8::FunctionCallbackInfo<v8::Value>& args) {

test/mjsunit/wasm/externref-table.js

@@ -79,3 +79,36 @@ d8.file.execute("test/mjsunit/wasm/wasm-module-builder.js");
 
   assertTraps(kTrapTableOutOfBounds, () => instance.exports.init());
 })();
+
+
+(function TestExternRefTableConstructorWithDefaultValue() {
+  print(arguments.callee.name);
+  const testObject = {};
+  const argument = { "element": "externref", "initial": 3 };
+  const table = new WebAssembly.Table(argument, testObject);
+  assertEquals(table.length, 3);
+  assertEquals(table.get(0), testObject);
+  assertEquals(table.get(1), testObject);
+  assertEquals(table.get(2), testObject);
+})();
+
+(function TestFuncRefTableConstructorWithDefaultValue() {
+  print(arguments.callee.name);
+
+  const expected = 6;
+  let dummy =
+      (() => {
+        let builder = new WasmModuleBuilder();
+        builder.addFunction('dummy', kSig_i_v)
+            .addBody([kExprI32Const, expected])
+            .exportAs('dummy');
+        return builder.instantiate().exports.dummy;
+      })();
+
+  const argument = { "element": "anyfunc", "initial": 3 };
+  const table = new WebAssembly.Table(argument, dummy);
+  assertEquals(table.length, 3);
+  assertEquals(table.get(0)(), expected);
+  assertEquals(table.get(1)(), expected);
+  assertEquals(table.get(2)(), expected);
+})();