[wasm] Call AsyncInstantiate directly when instantiating a module object

WebAssembly.instantiate is polymorphic, it can either take a module
object as parameter, or a buffer source which should be compiled first.
To share code between the two implementations, the module object was
first passed to a promise (i.e. which is the result of compilation).
However, passing the module object to a promise has a side effect if
the module object has a then function. To avoid this side effect I
remove this code sharing and call AsyncInstantiate directly in case
the parameter is a module object.

R=mstarzinger@chromium.org

Bug: chromium:836141
Change-Id: I67b76d0d7761c5aeb2cf1deda45b6842e494eed4
Reviewed-on: https://chromium-review.googlesource.com/1025774Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52755}

src/wasm/wasm-js.cc

@@ -346,25 +346,7 @@ MaybeLocal<Value> WebAssemblyInstantiateImpl(Isolate* isolate,
   return Utils::ToLocal(instance_object.ToHandleChecked());
 }
 
-// Entered as internal implementation detail of sync and async instantiate.
-// args[0] *must* be a WebAssembly.Module.
-void WebAssemblyInstantiateImplCallback(
-    const v8::FunctionCallbackInfo<v8::Value>& args) {
-  DCHECK_GE(args.Length(), 1);
-  v8::Isolate* isolate = args.GetIsolate();
-  MicrotasksScope does_not_run_microtasks(isolate,
-                                          MicrotasksScope::kDoNotRunMicrotasks);
-
-  HandleScope scope(args.GetIsolate());
-  Local<Value> module = args[0];
-  Local<Value> ffi = args.Data();
-  Local<Value> instance;
-  if (WebAssemblyInstantiateImpl(isolate, module, ffi).ToLocal(&instance)) {
-    args.GetReturnValue().Set(instance);
-  }
-}
-
-void WebAssemblyInstantiateToPairCallback(
+void WebAssemblyInstantiateCallback(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   DCHECK_GE(args.Length(), 1);
   Isolate* isolate = args.GetIsolate();
@@ -453,7 +435,7 @@ void WebAssemblyInstantiateStreaming(
   DCHECK(!module_promise.IsEmpty());
   Local<Value> data = args[1];
   ASSIGN(Function, instantiate_impl,
-         Function::New(context, WebAssemblyInstantiateToPairCallback, data));
+         Function::New(context, WebAssemblyInstantiateCallback, data));
   ASSIGN(Promise, result, module_promise->Then(context, instantiate_impl));
   args.GetReturnValue().Set(result);
 }
@@ -475,10 +457,12 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   Local<Context> context = isolate->GetCurrentContext();
 
   ASSIGN(Promise::Resolver, resolver, Promise::Resolver::New(context));
-  Local<Promise> module_promise = resolver->GetPromise();
-  args.GetReturnValue().Set(module_promise);
+  Local<Promise> promise = resolver->GetPromise();
+  args.GetReturnValue().Set(promise);
 
   Local<Value> first_arg_value = args[0];
+  // If args.Length < 2, this will be undefined - see FunctionCallbackInfo.
+  Local<Value> ffi = args[1];
   i::Handle<i::Object> first_arg = Utils::OpenHandle(*first_arg_value);
   if (!first_arg->IsJSObject()) {
     thrower.TypeError(
@@ -489,26 +473,35 @@ void WebAssemblyInstantiate(const v8::FunctionCallbackInfo<v8::Value>& args) {
     return;
   }
 
-  FunctionCallback instantiator = nullptr;
   if (first_arg->IsWasmModuleObject()) {
-    module_promise = resolver->GetPromise();
-    if (!resolver->Resolve(context, first_arg_value).IsJust()) return;
-    instantiator = WebAssemblyInstantiateImplCallback;
-  } else {
-    ASSIGN(Function, async_compile, Function::New(context, WebAssemblyCompile));
-    ASSIGN(Value, async_compile_retval,
-           async_compile->Call(context, args.Holder(), 1, &first_arg_value));
-    module_promise = Local<Promise>::Cast(async_compile_retval);
-    instantiator = WebAssemblyInstantiateToPairCallback;
+    i::Handle<i::WasmModuleObject> module_obj =
+        i::Handle<i::WasmModuleObject>::cast(first_arg);
+    // If args.Length < 2, this will be undefined - see FunctionCallbackInfo.
+    i::MaybeHandle<i::JSReceiver> maybe_imports =
+        GetValueAsImports(ffi, &thrower);
+
+    if (thrower.error()) {
+      auto maybe = resolver->Reject(context, Utils::ToLocal(thrower.Reify()));
+      CHECK_IMPLIES(!maybe.FromMaybe(false),
+                    i_isolate->has_scheduled_exception());
+      return;
+    }
+
+    i_isolate->wasm_engine()->AsyncInstantiate(
+        i_isolate, Utils::OpenHandle(*promise), module_obj, maybe_imports);
+    return;
   }
-  DCHECK(!module_promise.IsEmpty());
-  DCHECK_NOT_NULL(instantiator);
-  // If args.Length < 2, this will be undefined - see FunctionCallbackInfo.
-  // We'll check for that in WebAssemblyInstantiateImpl.
-  Local<Value> data = args[1];
+
+  // We did not get a WasmModuleObject as input, we first have to compile the
+  // input.
+  ASSIGN(Function, async_compile, Function::New(context, WebAssemblyCompile));
+  ASSIGN(Value, async_compile_retval,
+         async_compile->Call(context, args.Holder(), 1, &first_arg_value));
+  promise = Local<Promise>::Cast(async_compile_retval);
+  DCHECK(!promise.IsEmpty());
   ASSIGN(Function, instantiate_impl,
-         Function::New(context, instantiator, data));
-  ASSIGN(Promise, result, module_promise->Then(context, instantiate_impl));
+         Function::New(context, WebAssemblyInstantiateCallback, ffi));
+  ASSIGN(Promise, result, promise->Then(context, instantiate_impl));
   args.GetReturnValue().Set(result);
 }
 

test/mjsunit/regress/wasm/regress-836141.js

+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/wasm/wasm-constants.js');
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+const builder = new WasmModuleBuilder();
+builder.addMemory(16, 32);
+builder.addFunction("test", kSig_i_v).addBody([
+  kExprI32Const, 12,         // i32.const 0
+]);
+
+let bla = 0;
+let module = new WebAssembly.Module(builder.toBuffer());
+module.then = () => {
+  // Use setTimeout to get out of the promise chain.
+  setTimeout(assertUnreachable);
+};
+
+WebAssembly.instantiate(module);