[wasm] Split the compilation and instantiation API into sync and async methods.

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index baec27d3cc5661af4d47b0a9bfc8d71c332c63ef..815e24cf1add87d797dd14f932634d6d2427d40a 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -31,6 +31,20 @@ using v8::internal::wasm::ErrorThrower;
 namespace v8 {
 
 namespace {
+// TODO(wasm): move brand check to the respective types, and don't throw
+// in it, rather, use a provided ErrorThrower, or let caller handle it.
+static bool HasBrand(i::Handle<i::Object> value, i::Handle<i::Symbol> sym) {
+  if (!value->IsJSObject()) return false;
+  i::Handle<i::JSObject> object = i::Handle<i::JSObject>::cast(value);
+  Maybe<bool> has_brand = i::JSObject::HasOwnProperty(object, sym);
+  return !has_brand.IsNothing() && has_brand.ToChecked();

[Clemens Hammacher, 2017/02/16 20:36:57]

return has_brand.FromMaybe(false);

[titzer, 2017/02/17 13:17:53]

Done.

+}
+
+static bool BrandCheck(ErrorThrower* thrower, i::Handle<i::Object> value,

[ahaas, 2017/02/17 12:19:04]

nit: having thrower as the third parameter would make the code easier to read.

[titzer, 2017/02/17 13:17:53]

Done.

I thought we were more consistent about putting the ErrorThrower earlier in the
parameter list, but alas, we aren't. I think this file is more the other way,
so, suggestion accepted.

+                       i::Handle<i::Symbol> sym, const char* msg) {
+  return HasBrand(value, sym) ? true : (thrower->TypeError("%s", msg), false);
+}
+
 i::Handle<i::String> v8_str(i::Isolate* isolate, const char* str) {
   return isolate->factory()->NewStringFromAsciiChecked(str);
 }
@@ -38,17 +52,38 @@ Local<String> v8_str(Isolate* isolate, const char* str) {
   return Utils::ToLocal(v8_str(reinterpret_cast<i::Isolate*>(isolate), str));
 }
 
-struct RawBuffer {
-  const byte* start;
-  const byte* end;
-  size_t size() { return static_cast<size_t>(end - start); }
-};
+i::MaybeHandle<i::WasmModuleObject> GetFirstArgumentAsModule(
+    const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) {
+  v8::Isolate* isolate = args.GetIsolate();
+  i::MaybeHandle<i::WasmModuleObject> nothing;
+  if (args.Length() < 1) {
+    thrower->TypeError("Argument 0 must be a WebAssembly.Module");
+    return nothing;

[Clemens Hammacher, 2017/02/16 20:36:57]

You really don't like "return {};"? What does {} represent if not "nothing"? ;)
(also everywhere below)

[titzer, 2017/02/17 13:17:53]

Done. Here and elsewhere in this file.

+  }
+
+  Local<Context> context = isolate->GetCurrentContext();
+  i::Handle<i::Context> i_context = Utils::OpenHandle(*context);
+  if (!BrandCheck(thrower, Utils::OpenHandle(*args[0]),
+                  i::Handle<i::Symbol>(i_context->wasm_module_sym()),

[Clemens Hammacher, 2017/02/16 20:36:57]

this can we shortened to i::handle(i->context...)

[titzer, 2017/02/17 13:17:53]

Done.

+                  "Argument 0 must be a WebAssembly.Module")) {
+    return nothing;
+  }
+
+  Local<Object> module_obj = Local<Object>::Cast(args[0]);
+  return i::Handle<i::WasmModuleObject>::cast(
+      v8::Utils::OpenHandle(*module_obj));
+}
+
+i::wasm::ModuleWireBytes GetFirstArgumentAsBytes(
+    const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) {
+  if (args.Length() < 1) {
+    thrower->TypeError("Argument 0 must be a buffer source");
+    return i::wasm::ModuleWireBytes(nullptr, nullptr);
+  }
 
-RawBuffer GetRawBufferSource(
-    v8::Local<v8::Value> source, ErrorThrower* thrower) {
   const byte* start = nullptr;
   const byte* end = nullptr;
-
+  v8::Local<v8::Value> source = args[0];
   if (source->IsArrayBuffer()) {
     // A raw array buffer was passed.
     Local<ArrayBuffer> buffer = Local<ArrayBuffer>::Cast(source);
@@ -74,55 +109,28 @@ RawBuffer GetRawBufferSource(
   if (start == nullptr || end == start) {
     thrower->CompileError("BufferSource argument is empty");
   }
-  return {start, end};
+  // TODO(titzer): use the handle as well?
+  return i::wasm::ModuleWireBytes(start, end);
 }
 
-static i::MaybeHandle<i::WasmModuleObject> CreateModuleObject(
-    v8::Isolate* isolate, const v8::Local<v8::Value> source,
-    ErrorThrower* thrower) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  i::MaybeHandle<i::JSObject> nothing;
-
-  RawBuffer buffer = GetRawBufferSource(source, thrower);
-  if (buffer.start == nullptr) return i::MaybeHandle<i::WasmModuleObject>();
-
-  DCHECK(source->IsArrayBuffer() || source->IsTypedArray());
-  return i::wasm::CreateModuleObjectFromBytes(
-      i_isolate, buffer.start, buffer.end, thrower, i::wasm::kWasmOrigin,
-      i::Handle<i::Script>::null(), i::Vector<const byte>::empty());
-}
-
-static bool ValidateModule(v8::Isolate* isolate,
-                           const v8::Local<v8::Value> source,
-                           ErrorThrower* thrower) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  i::MaybeHandle<i::JSObject> nothing;
-
-  RawBuffer buffer = GetRawBufferSource(source, thrower);
-  if (buffer.start == nullptr) return false;
-
-  DCHECK(source->IsArrayBuffer() || source->IsTypedArray());
-  return i::wasm::ValidateModuleBytes(i_isolate, buffer.start, buffer.end,
-                                      thrower,
-                                      i::wasm::ModuleOrigin::kWasmOrigin);
-}
-
-// TODO(wasm): move brand check to the respective types, and don't throw
-// in it, rather, use a provided ErrorThrower, or let caller handle it.
-static bool HasBrand(i::Handle<i::Object> value, i::Handle<i::Symbol> sym) {
-  if (!value->IsJSObject()) return false;
-  i::Handle<i::JSObject> object = i::Handle<i::JSObject>::cast(value);
-  Maybe<bool> has_brand = i::JSObject::HasOwnProperty(object, sym);
-  return !has_brand.IsNothing() && has_brand.ToChecked();
-}
+i::MaybeHandle<i::JSReceiver> GetSecondArgumentAsImports(
+    const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) {
+  i::MaybeHandle<i::WasmModuleObject> nothing;
+  if (args.Length() < 2) return nothing;
+  if (args[1]->IsUndefined()) return nothing;
 
-static bool BrandCheck(ErrorThrower* thrower, i::Handle<i::Object> value,
-                       i::Handle<i::Symbol> sym, const char* msg) {
-  return HasBrand(value, sym) ? true : (thrower->TypeError("%s", msg), false);
+  if (!args[1]->IsObject()) {

[ahaas, 2017/02/17 12:19:04]

Independent question: why is this function called "IsObject" when what it
actually does is "Utils::OpenHandle(this)->IsJSReceiver()".

[titzer, 2017/02/17 13:17:53]

Don't have an answer to that :-/

+    thrower->TypeError("Argument 1 must be an object");
+    return nothing;
+  }
+  Local<Object> obj = Local<Object>::Cast(args[1]);
+  return i::Handle<i::JSReceiver>::cast(v8::Utils::OpenHandle(*obj));
 }
 
+// WebAssembly.compile(bytes) -> Promise
 void WebAssemblyCompile(const v8::FunctionCallbackInfo<v8::Value>& args) {

[ahaas, 2017/02/17 12:19:04]

I would prefer a function name which refers to the asynchronous nature of this
function.

[titzer, 2017/02/17 13:17:53]

The name here is chosen to reflect the JavaScript function name
"WebAssembly.compile", as are the others.

   v8::Isolate* isolate = args.GetIsolate();
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   HandleScope scope(isolate);
   ErrorThrower thrower(reinterpret_cast<i::Isolate*>(isolate),
                        "WebAssembly.compile()");
@@ -133,34 +141,28 @@ void WebAssemblyCompile(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::ReturnValue<v8::Value> return_value = args.GetReturnValue();
   return_value.Set(resolver->GetPromise());
 
-  if (args.Length() < 1) {
-    thrower.TypeError("Argument 0 must be a buffer source");
-    resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-    return;
-  }
-  i::MaybeHandle<i::JSObject> module_obj =
-      CreateModuleObject(isolate, args[0], &thrower);
-
+  auto bytes = GetFirstArgumentAsBytes(args, &thrower);
   if (thrower.error()) {
     resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-  } else {
-    resolver->Resolve(context, Utils::ToLocal(module_obj.ToHandleChecked()));
+    return;
   }
+  i::Handle<i::JSPromise> promise = Utils::OpenHandle(*resolver->GetPromise());
+  i::wasm::AsyncCompile(i_isolate, promise, bytes);
 }
 
+// WebAssembly.validate(bytes) -> bool
 void WebAssemblyValidate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   HandleScope scope(isolate);
   ErrorThrower thrower(reinterpret_cast<i::Isolate*>(isolate),
                        "WebAssembly.validate()");
 
-  if (args.Length() < 1) {
-    thrower.TypeError("Argument 0 must be a buffer source");
-    return;
-  }
+  auto bytes = GetFirstArgumentAsBytes(args, &thrower);
 
   v8::ReturnValue<v8::Value> return_value = args.GetReturnValue();
-  if (ValidateModule(isolate, args[0], &thrower)) {
+  if (!thrower.error() &&
+      i::wasm::SyncValidate(reinterpret_cast<i::Isolate*>(isolate), &thrower,
+                            bytes)) {
     return_value.Set(v8::True(isolate));
   } else {
     if (thrower.wasm_error()) thrower.Reify();  // Clear error.
@@ -168,84 +170,26 @@ void WebAssemblyValidate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   }
 }
 
+// new WebAssembly.Module(bytes) -> WebAssembly.Module
 void WebAssemblyModule(const v8::FunctionCallbackInfo<v8::Value>& args) {

[ahaas, 2017/02/17 12:19:04]

And a name which points to the synchronous nature here.

[titzer, 2017/02/17 13:17:53]

Same as above. It's named to reflect the JS API.

   v8::Isolate* isolate = args.GetIsolate();
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   HandleScope scope(isolate);

[Clemens Hammacher, 2017/02/16 20:36:57]

What does this line do? It's also not clang-formatted BTW.

[titzer, 2017/02/17 13:17:53]

Not sure which line you mean, as the lines seem pretty straightforward. One
opens a HandleScope and the other creates an on-stack ErrorThrower.

[Clemens Hammacher, 2017/02/17 13:54:05]

Never mind, Rietviel was missing some lines when showing the "context", so it
seemed as if the Scope is left immediately after that line.

   ErrorThrower thrower(reinterpret_cast<i::Isolate*>(isolate),
                        "WebAssembly.Module()");
 
-  if (args.Length() < 1) {
-    thrower.TypeError("Argument 0 must be a buffer source");
-    return;
-  }
+  auto bytes = GetFirstArgumentAsBytes(args, &thrower);
+  if (thrower.error()) return;
 
-  i::MaybeHandle<i::JSObject> module_obj =
-      CreateModuleObject(isolate, args[0], &thrower);
+  i::MaybeHandle<i::Object> module_obj =
+      i::wasm::SyncCompile(i_isolate, &thrower, bytes);
   if (module_obj.is_null()) return;
 
   v8::ReturnValue<v8::Value> return_value = args.GetReturnValue();
   return_value.Set(Utils::ToLocal(module_obj.ToHandleChecked()));
 }
 
-MaybeLocal<Value> InstantiateModuleImpl(
-    i::Isolate* i_isolate, i::Handle<i::WasmModuleObject> i_module_obj,
-    const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) {
-  // It so happens that in both the WebAssembly.instantiate, as well as
-  // WebAssembly.Instance ctor, the positions of the ffi object and memory
-  // are the same. If that changes later, we refactor the consts into
-  // parameters.
-  static const int kFfiOffset = 1;
-
-  MaybeLocal<Value> nothing;
-  i::Handle<i::JSReceiver> ffi = i::Handle<i::JSObject>::null();
-  // This is a first - level validation of the argument. If present, we only
-  // check its type. {Instantiate} will further check that if the module
-  // has imports, the argument must be present, as well as piecemeal
-  // import satisfaction.
-  if (args.Length() > kFfiOffset && !args[kFfiOffset]->IsUndefined()) {
-    if (!args[kFfiOffset]->IsObject()) {
-      thrower->TypeError("Argument %d must be an object", kFfiOffset);
-      return nothing;
-    }
-    Local<Object> obj = Local<Object>::Cast(args[kFfiOffset]);
-    ffi = i::Handle<i::JSReceiver>::cast(v8::Utils::OpenHandle(*obj));
-  }
-
-  i::MaybeHandle<i::JSObject> instance =
-      i::wasm::WasmModule::Instantiate(i_isolate, thrower, i_module_obj, ffi);
-  if (instance.is_null()) {
-    if (!thrower->error())
-      thrower->RuntimeError("Could not instantiate module");
-    return nothing;
-  }
-  DCHECK(!i_isolate->has_pending_exception());
-  return Utils::ToLocal(instance.ToHandleChecked());
-}
-
-namespace {
-i::MaybeHandle<i::WasmModuleObject> GetFirstArgumentAsModule(
-    const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) {
-  v8::Isolate* isolate = args.GetIsolate();
-  i::MaybeHandle<i::WasmModuleObject> nothing;
-  if (args.Length() < 1) {
-    thrower->TypeError("Argument 0 must be a WebAssembly.Module");
-    return nothing;
-  }
-
-  Local<Context> context = isolate->GetCurrentContext();
-  i::Handle<i::Context> i_context = Utils::OpenHandle(*context);
-  if (!BrandCheck(thrower, Utils::OpenHandle(*args[0]),
-                  i::Handle<i::Symbol>(i_context->wasm_module_sym()),
-                  "Argument 0 must be a WebAssembly.Module")) {
-    return nothing;
-  }
-
-  Local<Object> module_obj = Local<Object>::Cast(args[0]);
-  return i::Handle<i::WasmModuleObject>::cast(
-      v8::Utils::OpenHandle(*module_obj));
-}
-}  // namespace
-
+// WebAssembly.Module.imports(module) -> Array<Import>
 void WebAssemblyModuleImports(const v8::FunctionCallbackInfo<v8::Value>& args) {
   HandleScope scope(args.GetIsolate());
   v8::Isolate* isolate = args.GetIsolate();
@@ -253,14 +197,12 @@ void WebAssemblyModuleImports(const v8::FunctionCallbackInfo<v8::Value>& args) {
   ErrorThrower thrower(i_isolate, "WebAssembly.Module.imports()");
 
   auto maybe_module = GetFirstArgumentAsModule(args, &thrower);
-
-  if (!maybe_module.is_null()) {
-    auto imports =
-        i::wasm::GetImports(i_isolate, maybe_module.ToHandleChecked());
-    args.GetReturnValue().Set(Utils::ToLocal(imports));
-  }
+  if (thrower.error()) return;

[ahaas, 2017/02/17 12:19:04]

Is it okay that the actual error reason is lost here? Does it get lost?

[titzer, 2017/02/17 13:17:53]

The destructor of ErrorThrower will schedule it to be thrown in the isolate (see
wasm-result.cc:93)

+  auto imports = i::wasm::GetImports(i_isolate, maybe_module.ToHandleChecked());
+  args.GetReturnValue().Set(Utils::ToLocal(imports));
 }
 
+// WebAssembly.Module.imports(module) -> Array<Export>

[Clemens Hammacher, 2017/02/16 20:36:57]

exports, not imports.

[titzer, 2017/02/17 13:17:53]

Done.

 void WebAssemblyModuleExports(const v8::FunctionCallbackInfo<v8::Value>& args) {
   HandleScope scope(args.GetIsolate());
   v8::Isolate* isolate = args.GetIsolate();
@@ -268,14 +210,12 @@ void WebAssemblyModuleExports(const v8::FunctionCallbackInfo<v8::Value>& args) {
   ErrorThrower thrower(i_isolate, "WebAssembly.Module.exports()");
 
   auto maybe_module = GetFirstArgumentAsModule(args, &thrower);
-
-  if (!maybe_module.is_null()) {
-    auto exports =
-        i::wasm::GetExports(i_isolate, maybe_module.ToHandleChecked());
-    args.GetReturnValue().Set(Utils::ToLocal(exports));
-  }
+  if (thrower.error()) return;

[ahaas, 2017/02/17 12:19:04]

same here.

[titzer, 2017/02/17 13:17:53]

Acknowledged.

+  auto exports = i::wasm::GetExports(i_isolate, maybe_module.ToHandleChecked());
+  args.GetReturnValue().Set(Utils::ToLocal(exports));
 }
 
+// WebAssembly.Module.customSections(module, name) -> Array<Section>
 void WebAssemblyModuleCustomSections(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   HandleScope scope(args.GetIsolate());
@@ -284,6 +224,7 @@ void WebAssemblyModuleCustomSections(
   ErrorThrower thrower(i_isolate, "WebAssembly.Module.customSections()");
 
   auto maybe_module = GetFirstArgumentAsModule(args, &thrower);
+  if (thrower.error()) return;
 
   if (args.Length() < 2) {
     thrower.TypeError("Argument 1 must be a string");
@@ -296,16 +237,15 @@ void WebAssemblyModuleCustomSections(
     return;
   }
 
-  if (!maybe_module.is_null()) {
-    auto custom_sections =
-        i::wasm::GetCustomSections(i_isolate, maybe_module.ToHandleChecked(),
-                                   i::Handle<i::String>::cast(name), &thrower);
-    if (!thrower.error()) {
-      args.GetReturnValue().Set(Utils::ToLocal(custom_sections));
-    }
+  auto custom_sections =
+      i::wasm::GetCustomSections(i_isolate, maybe_module.ToHandleChecked(),
+                                 i::Handle<i::String>::cast(name), &thrower);
+  if (!thrower.error()) {

[Clemens Hammacher, 2017/02/16 20:36:57]

"if (thrower.error()) return;" would be more consistent.

[titzer, 2017/02/17 13:17:53]

Done.

+    args.GetReturnValue().Set(Utils::ToLocal(custom_sections));
   }
 }
 
+// new WebAssembly.Instance(module, imports) -> WebAssembly.Instance
 void WebAssemblyInstance(const v8::FunctionCallbackInfo<v8::Value>& args) {
   HandleScope scope(args.GetIsolate());
   v8::Isolate* isolate = args.GetIsolate();
@@ -313,19 +253,23 @@ void WebAssemblyInstance(const v8::FunctionCallbackInfo<v8::Value>& args) {
   ErrorThrower thrower(i_isolate, "WebAssembly.Instance()");
 
   auto maybe_module = GetFirstArgumentAsModule(args, &thrower);
+  if (thrower.error()) return;
 
-  if (!maybe_module.is_null()) {
-    MaybeLocal<Value> instance = InstantiateModuleImpl(
-        i_isolate, maybe_module.ToHandleChecked(), args, &thrower);
+  auto maybe_imports = GetSecondArgumentAsImports(args, &thrower);
+  if (thrower.error()) return;
 
-    if (instance.IsEmpty()) {
-      DCHECK(thrower.error());
-      return;
-    }
-    args.GetReturnValue().Set(instance.ToLocalChecked());
+  i::MaybeHandle<i::Object> instance_object = i::wasm::SyncInstantiate(
+      i_isolate, &thrower, maybe_module.ToHandleChecked(), maybe_imports,
+      i::MaybeHandle<i::JSArrayBuffer>());
+  if (!instance_object.is_null()) {

[Clemens Hammacher, 2017/02/16 20:36:57]

if (thrower.error()) return;

[titzer, 2017/02/17 13:17:53]

Done.

+    args.GetReturnValue().Set(
+        Utils::ToLocal(instance_object.ToHandleChecked()));
   }
 }
 
+// WebAssembly.instantiate(module, imports) -> WebAssembly.Instance
+// WebAssembly.instantiate(bytes, imports) -> {WebAssembly.Module,
+// WebAssembly.Instance}

[Clemens Hammacher, 2017/02/16 20:36:57]

That line break is annoying. Can you indent it a bit?

[titzer, 2017/02/17 13:17:53]

Done.

 void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ -356,50 +300,28 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
     resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
     return;
   }
-  bool want_pair =
-      !HasBrand(first_arg, i::Handle<i::Symbol>(i_context->wasm_module_sym()));
-  i::Handle<i::WasmModuleObject> module_obj;
-  if (want_pair) {
-    i::MaybeHandle<i::WasmModuleObject> maybe_module_obj =
-        CreateModuleObject(isolate, args[0], &thrower);
-    if (!maybe_module_obj.ToHandle(&module_obj)) {
-      DCHECK(thrower.error());
-      resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
-      return;
-    }
-  } else {
-    module_obj = i::Handle<i::WasmModuleObject>::cast(first_arg);
-  }
-  DCHECK(!module_obj.is_null());
-  MaybeLocal<Value> instance =
-      InstantiateModuleImpl(i_isolate, module_obj, args, &thrower);
-  if (instance.IsEmpty()) {
-    DCHECK(thrower.error());
+
+  auto maybe_imports = GetSecondArgumentAsImports(args, &thrower);
+  if (thrower.error()) {
     resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
+    return;
+  }
+  i::Handle<i::JSPromise> promise = Utils::OpenHandle(*resolver->GetPromise());
+
+  if (HasBrand(first_arg, i::Handle<i::Symbol>(i_context->wasm_module_sym()))) {
+    // WebAssembly.instantiate(module, imports) -> WebAssembly.Instance
+    auto module_object = GetFirstArgumentAsModule(args, &thrower);
+    i::wasm::AsyncInstantiate(i_isolate, promise,
+                              module_object.ToHandleChecked(), maybe_imports);
   } else {
-    DCHECK(!thrower.error());
-    Local<Value> retval;
-    if (want_pair) {
-      i::Handle<i::JSFunction> object_function = i::Handle<i::JSFunction>(
-          i_isolate->native_context()->object_function(), i_isolate);
-
-      i::Handle<i::JSObject> i_retval =
-          i_isolate->factory()->NewJSObject(object_function, i::TENURED);
-      i::Handle<i::String> module_property_name =
-          i_isolate->factory()->InternalizeUtf8String("module");
-      i::Handle<i::String> instance_property_name =
-          i_isolate->factory()->InternalizeUtf8String("instance");
-      i::JSObject::AddProperty(i_retval, module_property_name, module_obj,
-                               i::NONE);
-      i::JSObject::AddProperty(i_retval, instance_property_name,
-                               Utils::OpenHandle(*instance.ToLocalChecked()),
-                               i::NONE);
-      retval = Utils::ToLocal(i_retval);
-    } else {
-      retval = instance.ToLocalChecked();
+    // WebAssembly.instantiate(bytes, imports) -> {module, instance}
+    auto bytes = GetFirstArgumentAsBytes(args, &thrower);
+    if (thrower.error()) {
+      resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
+      return;
     }
-    DCHECK(!retval.IsEmpty());
-    resolver->Resolve(context, retval);
+    i::wasm::AsyncCompileAndInstantiate(i_isolate, promise, bytes, nullptr,
+                                        maybe_imports);
   }
 }
 
@@ -430,6 +352,7 @@ bool GetIntegerProperty(v8::Isolate* isolate, ErrorThrower* thrower,
   return false;
 }
 
+// new WebAssembly.Table(args) -> WebAssembly.Table
 void WebAssemblyTable(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   HandleScope scope(isolate);
@@ -546,6 +469,7 @@ void WebAssemblyTableGetLength(
       v8::Number::New(isolate, receiver->current_length()));
 }
 
+// WebAssembly.Table.grow(num) -> num
 void WebAssemblyTableGrow(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   ErrorThrower thrower(reinterpret_cast<i::Isolate*>(isolate),
@@ -599,6 +523,7 @@ void WebAssemblyTableGrow(const v8::FunctionCallbackInfo<v8::Value>& args) {
   return_value.Set(old_size);
 }
 
+// WebAssembly.Table.get(num) -> JSFunction
 void WebAssemblyTableGet(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ -626,6 +551,7 @@ void WebAssemblyTableGet(const v8::FunctionCallbackInfo<v8::Value>& args) {
   return_value.Set(Utils::ToLocal(value));
 }
 
+// WebAssembly.Table.set(num, JSFunction)
 void WebAssemblyTableSet(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ -673,6 +599,7 @@ void WebAssemblyTableSet(const v8::FunctionCallbackInfo<v8::Value>& args) {
   i::Handle<i::FixedArray>::cast(array)->set(i, *value);
 }
 
+// WebAssembly.Memory.grow(num) -> num
 void WebAssemblyMemoryGrow(const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ -715,6 +642,7 @@ void WebAssemblyMemoryGrow(const v8::FunctionCallbackInfo<v8::Value>& args) {
   return_value.Set(ret);
 }
 
+// WebAssembly.Memory.buffer -> ArrayBuffer
 void WebAssemblyMemoryGetBuffer(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Isolate* isolate = args.GetIsolate();