Reland [CloneObjectIC] overwrite monomorphic/polymorphic feedback if deprecated

An object with a deprecated Map which has already been cached in
CloneObjectIC feedback is still a valid Map for fast cloning --- but
to be consistent with other ICs, deprecated maps are ignored, and are
expected to be transitioned away from.

If the source object has a deprecated map, the instance is migrated.

BUG=v8:7611, chromium:867958, chromium:868586
R=jkummerow@chromium.org, mvstanton@chromium.org

Change-Id: I477aec6c8d0ae1e1648a70e85d2fd46146521d1c
Reviewed-on: https://chromium-review.googlesource.com/1154143
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54799}

src/feedback-vector.cc

@@ -756,13 +756,14 @@ void FeedbackNexus::ConfigureCloneObject(Handle<Map> source_map,
       SetFeedbackExtra(*result_map);
       break;
     case MONOMORPHIC:
-      if (maybe_feedback->IsClearedWeakHeapObject()) {
+      if (maybe_feedback->IsClearedWeakHeapObject() ||
+          feedback.is_identical_to(source_map) ||
+          Map::cast(*feedback)->is_deprecated()) {
         // Remain in MONOMORPHIC state if previous feedback has been collected.
         SetFeedback(HeapObjectReference::Weak(*source_map));
         SetFeedbackExtra(*result_map);
       } else {
         // Transition to POLYMORPHIC.
-        DCHECK_NE(*source_map, *feedback);
         Handle<WeakFixedArray> array =
             EnsureArrayOfSize(2 * kCloneObjectPolymorphicEntrySize);
         array->Set(0, maybe_feedback);
@@ -778,10 +779,12 @@ void FeedbackNexus::ConfigureCloneObject(Handle<Map> source_map,
       Handle<WeakFixedArray> array = Handle<WeakFixedArray>::cast(feedback);
       int i = 0;
       for (; i < array->length(); i += kCloneObjectPolymorphicEntrySize) {
-        if (array->Get(i)->IsClearedWeakHeapObject()) {
+        MaybeObject* feedback = array->Get(i);
+        if (!feedback->IsClearedWeakHeapObject()) break;
+        Handle<Map> cached_map(Map::cast(feedback->GetHeapObject()), isolate);
+        if (cached_map.is_identical_to(source_map) ||
+            cached_map->is_deprecated())
           break;
-        }
-        DCHECK_NE(array->Get(i)->GetHeapObject(), *source_map);
       }
 
       if (i >= array->length()) {

src/ic/ic.cc

@@ -2549,6 +2549,9 @@ RUNTIME_FUNCTION(Runtime_CloneObjectIC_Miss) {
   DCHECK_EQ(4, args.length());
   Handle<HeapObject> source = args.at<HeapObject>(0);
   int flags = args.smi_at(1);
+
+  MigrateDeprecated(source);
+
   FeedbackSlot slot = FeedbackVector::ToSlot(args.smi_at(2));
   Handle<FeedbackVector> vector = args.at<FeedbackVector>(3);
 

test/mjsunit/es9/regress/regress-867958.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.
+
+// Check that encountering deprecated Maps does not cause CloneObjectIC to
+// crash.
+var obj1 = { x: 1 };
+var obj2 = { x: 2 }; // same map
+obj2.x = null; // deprecate map
+
+function f() { return { ...obj1 } };
+assertEquals({ x: 1 }, f()); // missed, object migrated to cached new map
+assertEquals({ x: 1 }, f()); // monomorphic cache-hit