[promise] Remove incorrect fast path

Previously we would directly take the result from a fulfilled native
promise bypassing the microtask queue. This is observably different
from the spec.

Note: Our variant of the bluebird benchmark is heavily favored towards
fulfilled native promises because we don't use setTimeout (unlike the
original benchmark). I suspect this pattern doesn't appear often in
the wild so it's fine to take this hit for now.

PSA for Perf sheriffs: this is going to tank some benchmarks.

Bug: chromium:800651, v8:5691, v8:6007
Change-Id: Ic273bf2195529424b0d87359d28d5267060d5252
Reviewed-on: https://chromium-review.googlesource.com/895416
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51010}

src/builtins/builtins-promise-gen.cc

@@ -587,14 +587,6 @@ void PromiseBuiltinsAssembler::InternalResolvePromise(Node* context,
   // reusing the value from the promise.
   BIND(&if_nativepromise);
   {
-    Node* const thenable_status = PromiseStatus(result);
-    Node* const thenable_value =
-        LoadObjectField(result, JSPromise::kReactionsOrResultOffset);
-
-    Label if_isnotpending(this);
-    GotoIfNot(IsPromiseStatus(thenable_status, v8::Promise::kPending),
-              &if_isnotpending);
-
     // TODO(gsathya): Use a marker here instead of the actual then
     // callback, and check for the marker in PromiseResolveThenableJob
     // and perform PromiseThen.
@@ -602,39 +594,6 @@ void PromiseBuiltinsAssembler::InternalResolvePromise(Node* context,
         LoadContextElement(native_context, Context::PROMISE_THEN_INDEX);
     var_then.Bind(then);
     Goto(&do_enqueue);
-
-    BIND(&if_isnotpending);
-    {
-      Label if_fulfilled(this), if_rejected(this);
-      Branch(IsPromiseStatus(thenable_status, v8::Promise::kFulfilled),
-             &if_fulfilled, &if_rejected);
-
-      BIND(&if_fulfilled);
-      {
-        PromiseFulfill(context, promise, thenable_value,
-                       v8::Promise::kFulfilled);
-        PromiseSetHasHandler(promise);
-        Goto(&out);
-      }
-
-      BIND(&if_rejected);
-      {
-        Label reject(this);
-        Node* const has_handler = PromiseHasHandler(result);
-
-        // Promise has already been rejected, but had no handler.
-        // Revoke previously triggered reject event.
-        GotoIf(has_handler, &reject);
-        CallRuntime(Runtime::kPromiseRevokeReject, context, result);
-        Goto(&reject);
-
-        BIND(&reject);
-        // Don't cause a debug event as this case is forwarding a rejection.
-        InternalPromiseReject(context, promise, thenable_value, false);
-        PromiseSetHasHandler(result);
-        Goto(&out);
-      }
-    }
   }
 
   BIND(&if_notnativepromise);

test/mjsunit/regress/regress-5691.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.
+//
+// Flags: --allow-natives-syntax
+
+var log = "";
+var result;
+Promise.resolve()
+  .then(() => log += "|turn1")
+  .then(() => log += "|turn2")
+  .then(() => log += "|turn3")
+  .then(() => log += "|turn4")
+  .then(() => result = "|start|turn1|fast-resolve|turn2|turn3|slow-resolve|turn4\n"+log)
+  .catch(e => print("ERROR", e));
+
+Promise.resolve(Promise.resolve()).then(() => log += "|fast-resolve");
+(class extends Promise {}).resolve(Promise.resolve()).then(() => log += "|slow-resolve");
+
+log += "|start";
+  %RunMicrotasks();
+assertEquals("|start|turn1|fast-resolve|turn2|turn3|slow-resolve|turn4\n\
+|start|turn1|fast-resolve|turn2|turn3|slow-resolve|turn4", result);

test/mjsunit/regress/regress-800651.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.
+//
+// Flags: --allow-natives-syntax
+
+var list = [];
+function log(item) { list.push(item); }
+async function f() {
+  try {
+    let namespace = await import(/a/);
+  } catch(e) {
+    log(1);
+  }
+}
+f();
+
+async function g() {
+  try {
+    let namespace = await import({ get toString() { return undefined; }});
+  } catch(e) {
+    log(2);
+  }
+}
+g();
+  %RunMicrotasks();
+assertEquals(list, [1,2]);