[CloneObjectIC] clone MutableHeapNumbers only if !FLAG_unbox_double_fields

Change the macros added in bf84766a to
only do the hard work if FLAG_unbox_double_fields is unset (otherwise,
they will attempt to dereference raw float64s, which is bad!)

Also adds a write barrier in CopyPropertyArrayValues for each store if
it's possible that a MutableHeapNumber is cloned.

BUG=chromium:901301, chromium:902965, chromium:903070, v8:7611
R=cbruni@chromium.org, jkummerow@chromium.org, ishell@chromium.org

Change-Id: I224d3c4e7b0a887684bff68985b4d97021ba4cfb
Reviewed-on: https://chromium-review.googlesource.com/c/1323911
Commit-Queue: Caitlin Potter <caitp@igalia.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57368}

src/builtins/builtins-constructor-gen.cc

@@ -526,8 +526,7 @@ Node* ConstructorBuiltinsAssembler::EmitCreateShallowObjectLiteral(
     Label continue_with_write_barrier(this), done_init(this);
     TVARIABLE(IntPtrT, offset, IntPtrConstant(JSObject::kHeaderSize));
     // Mutable heap numbers only occur on 32-bit platforms.
-    bool may_use_mutable_heap_numbers =
-        FLAG_track_double_fields && !FLAG_unbox_double_fields;
+    bool may_use_mutable_heap_numbers = !FLAG_unbox_double_fields;
     {
       Comment("Copy in-object properties fast");
       Label continue_fast(this, &offset);

src/code-stub-assembler.cc

@@ -5053,6 +5053,13 @@ void CodeStubAssembler::CopyPropertyArrayValues(Node* from_array,
   Comment("[ CopyPropertyArrayValues");
 
   bool needs_write_barrier = barrier_mode == UPDATE_WRITE_BARRIER;
+
+  if (destroy_source == DestroySource::kNo) {
+    // PropertyArray may contain MutableHeapNumbers, which will be cloned on the
+    // heap, requiring a write barrier.
+    needs_write_barrier = true;
+  }
+
   Node* start = IntPtrOrSmiConstant(0, mode);
   ElementsKind kind = PACKED_ELEMENTS;
   BuildFastFixedArrayForEach(

src/ic/accessor-assembler.cc

@@ -3566,7 +3566,7 @@ void AccessorAssembler::GenerateCloneObjectIC_Slow() {
 
 void AccessorAssembler::GenerateCloneObjectIC() {
   typedef CloneObjectWithVectorDescriptor Descriptor;
-  Node* source = Parameter(Descriptor::kSource);
+  TNode<HeapObject> source = CAST(Parameter(Descriptor::kSource));
   Node* flags = Parameter(Descriptor::kFlags);
   Node* slot = Parameter(Descriptor::kSlot);
   Node* vector = Parameter(Descriptor::kVector);
@@ -3576,8 +3576,7 @@ void AccessorAssembler::GenerateCloneObjectIC() {
   Label miss(this, Label::kDeferred), try_polymorphic(this, Label::kDeferred),
       try_megamorphic(this, Label::kDeferred);
 
-  CSA_SLOW_ASSERT(this, TaggedIsNotSmi(source));
-  Node* source_map = LoadMap(UncheckedCast<HeapObject>(source));
+  TNode<Map> source_map = LoadMap(UncheckedCast<HeapObject>(source));
   GotoIf(IsDeprecatedMap(source_map), &miss);
   TNode<MaybeObject> feedback = TryMonomorphicCase(
       slot, vector, source_map, &if_handler, &var_handler, &try_polymorphic);
@@ -3598,7 +3597,7 @@ void AccessorAssembler::GenerateCloneObjectIC() {
 
     // The IC fast case should only be taken if the result map a compatible
     // elements kind with the source object.
-    TNode<FixedArrayBase> source_elements = LoadElements(source);
+    TNode<FixedArrayBase> source_elements = LoadElements(CAST(source));
 
     auto flags = ExtractFixedArrayFlag::kAllFixedArraysDontCopyCOW;
     var_elements = CAST(CloneFixedArray(source_elements, flags));
@@ -3633,22 +3632,43 @@ void AccessorAssembler::GenerateCloneObjectIC() {
     // Lastly, clone any in-object properties.
     // Determine the inobject property capacity of both objects, and copy the
     // smaller number into the resulting object.
-    Node* source_start = LoadMapInobjectPropertiesStartInWords(source_map);
-    Node* source_size = LoadMapInstanceSizeInWords(source_map);
-    Node* result_start = LoadMapInobjectPropertiesStartInWords(result_map);
-    Node* field_offset_difference =
+    TNode<IntPtrT> source_start =
+        LoadMapInobjectPropertiesStartInWords(source_map);
+    TNode<IntPtrT> source_size = LoadMapInstanceSizeInWords(source_map);
+    TNode<IntPtrT> result_start =
+        LoadMapInobjectPropertiesStartInWords(result_map);
+    TNode<IntPtrT> field_offset_difference =
         TimesPointerSize(IntPtrSub(result_start, source_start));
-    BuildFastLoop(source_start, source_size,
-                  [=](Node* field_index) {
-                    Node* field_offset = TimesPointerSize(field_index);
-                    TNode<Object> field = LoadObjectField(source, field_offset);
-                    field = CloneIfMutablePrimitive(field);
-                    Node* result_offset =
-                        IntPtrAdd(field_offset, field_offset_difference);
-                    StoreObjectFieldNoWriteBarrier(object, result_offset,
-                                                   field);
-                  },
-                  1, INTPTR_PARAMETERS, IndexAdvanceMode::kPost);
+
+    // If MutableHeapNumbers may be present in-object, allocations may occur
+    // within this loop, thus the write barrier is required.
+    //
+    // TODO(caitp): skip the write barrier until the first MutableHeapNumber
+    // field is found
+    const bool may_use_mutable_heap_numbers = !FLAG_unbox_double_fields;
+
+    BuildFastLoop(
+        source_start, source_size,
+        [=](Node* field_index) {
+          TNode<IntPtrT> field_offset =
+              TimesPointerSize(UncheckedCast<IntPtrT>(field_index));
+
+          if (may_use_mutable_heap_numbers) {
+            TNode<Object> field = LoadObjectField(source, field_offset);
+            field = CloneIfMutablePrimitive(field);
+            TNode<IntPtrT> result_offset =
+                IntPtrAdd(field_offset, field_offset_difference);
+            StoreObjectField(object, result_offset, field);
+          } else {
+            // Copy fields as raw data.
+            TNode<IntPtrT> field =
+                LoadObjectField<IntPtrT>(source, field_offset);
+            TNode<IntPtrT> result_offset =
+                IntPtrAdd(field_offset, field_offset_difference);
+            StoreObjectFieldNoWriteBarrier(object, result_offset, field);
+          }
+        },
+        1, INTPTR_PARAMETERS, IndexAdvanceMode::kPost);
     Return(object);
   }
 

test/mjsunit/es9/regress/regress-902965.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.
+
+// Previously, spreading in-object properties would always treat double fields
+// as tagged, potentially dereferencing a Float64.
+function inobjectDouble() {
+  "use strict";
+  this.x = -3.9;
+}
+const instance = new inobjectDouble();
+const clone = { ...instance, };

test/mjsunit/es9/regress/regress-903070.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.
+
+function clone(src) {
+  return { ...src };
+}
+
+function inobjectDoubles() {
+  "use strict";
+  this.p0 = -6400510997704731;
+}
+
+// Check that unboxed double is not treated as tagged
+assertEquals({ p0: -6400510997704731 }, clone(new inobjectDoubles()));