In-object double fields unboxing (for 64-bit only).

test/cctest/test-unboxed-doubles.cc

+// Copyright 2014 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.
+
+#include <stdlib.h>
+#include <utility>
+
+#include "src/v8.h"
+
+#include "src/compilation-cache.h"
+#include "src/execution.h"
+#include "src/factory.h"
+#include "src/global-handles.h"
+#include "src/ic/ic.h"
+#include "src/macro-assembler.h"
+#include "test/cctest/cctest.h"
+
+using namespace v8::base;
+using namespace v8::internal;
+
+#if (V8_DOUBLE_FIELDS_UNBOXING)
+
+
+namespace v8 {
+namespace internal {
+
+class TestAccessor {
+ public:
+  static inline LayoutDescriptor* LayoutDescriptor_SetTagged(
+      LayoutDescriptor* layout_descriptor, int field_index, bool tagged) {
+    return layout_descriptor->SetTagged(field_index, tagged);
+  }
+
+  static inline int LayoutDescriptor_capacity(
+      LayoutDescriptor* layout_descriptor) {
+    return layout_descriptor->capacity();
+  }
+
+  static inline Handle<Map> Map_CopyInstallDescriptors(
+      Handle<Map> map, int new_descriptor, Handle<DescriptorArray> descriptors,
+      Handle<LayoutDescriptor> full_layout_descriptor) {
+    return Map::CopyInstallDescriptors(map, new_descriptor, descriptors,
+                                       full_layout_descriptor);
+  }
+};
+}
+}  // namespace v8::internal
+
+
+enum PropertyKind {
+  PROP_CONSTANT,
+  PROP_SMI,
+  PROP_DOUBLE,
+  PROP_TAGGED,
+  PROP_KIND_NUMBER,
+};
+
+static Representation representations[PROP_KIND_NUMBER] = {
+    Representation::None(), Representation::Smi(), Representation::Double(),
+    Representation::Tagged()};
+
+
+static Handle<DescriptorArray> CreateDescriptorArray(Isolate* isolate,
+                                                     PropertyKind* props,
+                                                     int kPropsCount) {
+  Factory* factory = isolate->factory();
+
+  Handle<String> func_name = factory->InternalizeUtf8String("func");
+  Handle<JSFunction> func = factory->NewFunction(func_name);
+
+  Handle<DescriptorArray> descriptors =
+      DescriptorArray::Allocate(isolate, 0, kPropsCount);
+
+  int next_field_offset = 0;
+  for (int i = 0; i < kPropsCount; i++) {
+    EmbeddedVector<char, 64> buffer;
+    SNPrintF(buffer, "prop%d", i);
+    Handle<String> name = factory->InternalizeUtf8String(buffer.start());
+
+    PropertyKind kind = props[i];
+
+    if (kind == PROP_CONSTANT) {
+      ConstantDescriptor d(name, func, NONE);
+      descriptors->Append(&d);
+
+    } else {
+      FieldDescriptor f(name, next_field_offset, NONE, representations[kind]);
+      next_field_offset += f.GetDetails().field_width_in_words();
+      descriptors->Append(&f);
+    }
+  }
+  return descriptors;
+}
+
+
+TEST(LayoutDescriptorBasicFast) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+
+  LayoutDescriptor* layout_desc = LayoutDescriptor::FastPointerLayout();
+
+  CHECK(!layout_desc->IsSlowLayout());
+  CHECK(layout_desc->IsFastPointerLayout());
+  CHECK_EQ(kSmiValueSize, TestAccessor::LayoutDescriptor_capacity(layout_desc));
+
+  for (int i = 0; i < kSmiValueSize + 13; i++) {
+    CHECK_EQ(true, layout_desc->IsTagged(i));
+  }
+  CHECK_EQ(true, layout_desc->IsTagged(-1));
+  CHECK_EQ(true, layout_desc->IsTagged(-12347));
+  CHECK_EQ(true, layout_desc->IsTagged(15635));
+  CHECK(layout_desc->IsFastPointerLayout());
+
+  for (int i = 0; i < kSmiValueSize; i++) {
+    layout_desc =
+        TestAccessor::LayoutDescriptor_SetTagged(layout_desc, i, false);
+    CHECK_EQ(false, layout_desc->IsTagged(i));
+    layout_desc =
+        TestAccessor::LayoutDescriptor_SetTagged(layout_desc, i, true);
+    CHECK_EQ(true, layout_desc->IsTagged(i));
+  }
+  CHECK(layout_desc->IsFastPointerLayout());
+}
+
+
+TEST(LayoutDescriptorBasicSlow) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    // All properties tagged.
+    props[i] = PROP_TAGGED;
+  }
+
+  {
+    Handle<DescriptorArray> descriptors =
+        CreateDescriptorArray(isolate, props, kPropsCount);
+
+    Handle<Map> map = Map::Create(isolate, kPropsCount);
+
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_EQ(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK_EQ(kSmiValueSize,
+             TestAccessor::LayoutDescriptor_capacity(*layout_descriptor));
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  props[0] = PROP_DOUBLE;
+  props[kPropsCount - 1] = PROP_DOUBLE;
+
+  Handle<DescriptorArray> descriptors =
+      CreateDescriptorArray(isolate, props, kPropsCount);
+
+  {
+    int inobject_properties = kPropsCount - 1;
+    Handle<Map> map = Map::Create(isolate, inobject_properties);
+
+    // Should be fast as the only double property is the first one.
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_NE(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK(!layout_descriptor->IsSlowLayout());
+    CHECK(!layout_descriptor->IsFastPointerLayout());
+
+    CHECK_EQ(false, layout_descriptor->IsTagged(0));
+    for (int i = 1; i < kPropsCount; i++) {
+      CHECK_EQ(true, layout_descriptor->IsTagged(i));
+    }
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    int inobject_properties = kPropsCount;
+    Handle<Map> map = Map::Create(isolate, inobject_properties);
+
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_NE(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK(layout_descriptor->IsSlowLayout());
+    CHECK(!layout_descriptor->IsFastPointerLayout());
+    CHECK(TestAccessor::LayoutDescriptor_capacity(*layout_descriptor) >
+          kSmiValueSize);
+
+    CHECK_EQ(false, layout_descriptor->IsTagged(0));
+    CHECK_EQ(false, layout_descriptor->IsTagged(kPropsCount - 1));
+    for (int i = 1; i < kPropsCount - 1; i++) {
+      CHECK_EQ(true, layout_descriptor->IsTagged(i));
+    }
+
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+
+    // Here we have truly slow layout descriptor, so play with the bits.
+    CHECK_EQ(true, layout_descriptor->IsTagged(-1));
+    CHECK_EQ(true, layout_descriptor->IsTagged(-12347));
+    CHECK_EQ(true, layout_descriptor->IsTagged(15635));
+
+    LayoutDescriptor* layout_desc = *layout_descriptor;
+    // Play with the bits but leave it in consistent state with map at the end.
+    for (int i = 1; i < kPropsCount - 1; i++) {
+      layout_desc =
+          TestAccessor::LayoutDescriptor_SetTagged(layout_desc, i, false);
+      CHECK_EQ(false, layout_desc->IsTagged(i));
+      layout_desc =
+          TestAccessor::LayoutDescriptor_SetTagged(layout_desc, i, true);
+      CHECK_EQ(true, layout_desc->IsTagged(i));
+    }
+    CHECK(layout_desc->IsSlowLayout());
+    CHECK(!layout_desc->IsFastPointerLayout());
+
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+}
+
+
+TEST(LayoutDescriptorCreateNewFast) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  PropertyKind props[] = {
+      PROP_CONSTANT,
+      PROP_TAGGED,  // field #0
+      PROP_CONSTANT,
+      PROP_DOUBLE,  // field #1
+      PROP_CONSTANT,
+      PROP_TAGGED,  // field #2
+      PROP_CONSTANT,
+  };
+  const int kPropsCount = arraysize(props);
+
+  Handle<DescriptorArray> descriptors =
+      CreateDescriptorArray(isolate, props, kPropsCount);
+
+  {
+    Handle<Map> map = Map::Create(isolate, 0);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_EQ(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    Handle<Map> map = Map::Create(isolate, 1);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_EQ(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    Handle<Map> map = Map::Create(isolate, 2);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_NE(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK(!layout_descriptor->IsSlowLayout());
+    CHECK_EQ(true, layout_descriptor->IsTagged(0));
+    CHECK_EQ(false, layout_descriptor->IsTagged(1));
+    CHECK_EQ(true, layout_descriptor->IsTagged(2));
+    CHECK_EQ(true, layout_descriptor->IsTagged(125));
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+}
+
+
+TEST(LayoutDescriptorCreateNewSlow) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    props[i] = static_cast<PropertyKind>(i % PROP_KIND_NUMBER);
+  }
+
+  Handle<DescriptorArray> descriptors =
+      CreateDescriptorArray(isolate, props, kPropsCount);
+
+  {
+    Handle<Map> map = Map::Create(isolate, 0);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_EQ(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    Handle<Map> map = Map::Create(isolate, 1);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_EQ(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    Handle<Map> map = Map::Create(isolate, 2);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_NE(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK(!layout_descriptor->IsSlowLayout());
+    CHECK_EQ(true, layout_descriptor->IsTagged(0));
+    CHECK_EQ(false, layout_descriptor->IsTagged(1));
+    CHECK_EQ(true, layout_descriptor->IsTagged(2));
+    CHECK_EQ(true, layout_descriptor->IsTagged(125));
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  }
+
+  {
+    int inobject_properties = kPropsCount / 2;
+    Handle<Map> map = Map::Create(isolate, inobject_properties);
+    layout_descriptor = LayoutDescriptor::New(map, descriptors, kPropsCount);
+    CHECK_NE(LayoutDescriptor::FastPointerLayout(), *layout_descriptor);
+    CHECK(layout_descriptor->IsSlowLayout());
+    for (int i = 0; i < inobject_properties; i++) {
+      // PROP_DOUBLE has index 1 among FIELD properties.
+      const bool tagged = (i % (PROP_KIND_NUMBER - 1)) != 1;
+      CHECK_EQ(tagged, layout_descriptor->IsTagged(i));
+    }
+    // Every property after inobject_properties must be tagged.
+    for (int i = inobject_properties; i < kPropsCount; i++) {
+      CHECK_EQ(true, layout_descriptor->IsTagged(i));
+    }
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+    DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+
+    // Now test LayoutDescriptor::cast_gc_safe().
+    Handle<LayoutDescriptor> layout_descriptor_copy =
+        LayoutDescriptor::New(map, descriptors, kPropsCount);
+
+    LayoutDescriptor* layout_desc = *layout_descriptor;
+    CHECK_EQ(layout_desc, LayoutDescriptor::cast(layout_desc));
+    CHECK_EQ(layout_desc, LayoutDescriptor::cast_gc_safe(layout_desc));
+    CHECK(layout_descriptor->IsFixedTypedArrayBase());
+    // Now make it look like a forwarding pointer to layout_descriptor_copy.
+    MapWord map_word = layout_desc->map_word();
+    CHECK(!map_word.IsForwardingAddress());
+    layout_desc->set_map_word(
+        MapWord::FromForwardingAddress(*layout_descriptor_copy));
+    CHECK(layout_desc->map_word().IsForwardingAddress());
+    CHECK_EQ(*layout_descriptor_copy,
+             LayoutDescriptor::cast_gc_safe(layout_desc));
+
+    // Restore it back.
+    layout_desc->set_map_word(map_word);
+    CHECK_EQ(layout_desc, LayoutDescriptor::cast(layout_desc));
+  }
+}
+
+
+static Handle<LayoutDescriptor> TestLayoutDescriptorAppend(
+    Isolate* isolate, int inobject_properties, PropertyKind* props,
+    int kPropsCount) {
+  Factory* factory = isolate->factory();
+
+  Handle<String> func_name = factory->InternalizeUtf8String("func");
+  Handle<JSFunction> func = factory->NewFunction(func_name);
+
+  Handle<DescriptorArray> descriptors =
+      DescriptorArray::Allocate(isolate, 0, kPropsCount);
+
+  Handle<Map> map = Map::Create(isolate, inobject_properties);
+  map->InitializeDescriptors(*descriptors,
+                             LayoutDescriptor::FastPointerLayout());
+
+  int next_field_offset = 0;
+  for (int i = 0; i < kPropsCount; i++) {
+    EmbeddedVector<char, 64> buffer;
+    SNPrintF(buffer, "prop%d", i);
+    Handle<String> name = factory->InternalizeUtf8String(buffer.start());
+
+    Handle<LayoutDescriptor> layout_descriptor;
+    PropertyKind kind = props[i];
+    if (kind == PROP_CONSTANT) {
+      ConstantDescriptor d(name, func, NONE);
+      layout_descriptor = LayoutDescriptor::Append(map, d.GetDetails());
+      descriptors->Append(&d);
+
+    } else {
+      FieldDescriptor f(name, next_field_offset, NONE, representations[kind]);
+      int field_width_in_words = f.GetDetails().field_width_in_words();
+      next_field_offset += field_width_in_words;
+      layout_descriptor = LayoutDescriptor::Append(map, f.GetDetails());
+      descriptors->Append(&f);
+
+      int field_index = f.GetDetails().field_index();
+      bool is_inobject = field_index < map->inobject_properties();
+      for (int bit = 0; bit < field_width_in_words; bit++) {
+        CHECK_EQ(is_inobject && (kind == PROP_DOUBLE),
+                 !layout_descriptor->IsTagged(field_index + bit));
+      }
+      CHECK(layout_descriptor->IsTagged(next_field_offset));
+    }
+    map->InitializeDescriptors(*descriptors, *layout_descriptor);
+  }
+  Handle<LayoutDescriptor> layout_descriptor(map->layout_descriptor(), isolate);
+  DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  return layout_descriptor;
+}
+
+
+TEST(LayoutDescriptorAppend) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    props[i] = static_cast<PropertyKind>(i % PROP_KIND_NUMBER);
+  }
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, 0, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, 13, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, kSmiValueSize, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppend(isolate, kSmiValueSize * 2,
+                                                 props, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, kPropsCount, props, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+}
+
+
+TEST(LayoutDescriptorAppendAllDoubles) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    props[i] = PROP_DOUBLE;
+  }
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, 0, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, 13, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, kSmiValueSize, props, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppend(isolate, kSmiValueSize + 1,
+                                                 props, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppend(isolate, kSmiValueSize * 2,
+                                                 props, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor =
+      TestLayoutDescriptorAppend(isolate, kPropsCount, props, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  {
+    // Ensure layout descriptor switches into slow mode at the right moment.
+    layout_descriptor =
+        TestLayoutDescriptorAppend(isolate, kPropsCount, props, kSmiValueSize);
+    CHECK(!layout_descriptor->IsSlowLayout());
+
+    layout_descriptor = TestLayoutDescriptorAppend(isolate, kPropsCount, props,
+                                                   kSmiValueSize + 1);
+    CHECK(layout_descriptor->IsSlowLayout());
+  }
+}
+
+
+static Handle<LayoutDescriptor> TestLayoutDescriptorAppendIfFastOrUseFull(
+    Isolate* isolate, int inobject_properties,
+    Handle<DescriptorArray> descriptors, int number_of_descriptors) {
+  Handle<Map> map = Map::Create(isolate, inobject_properties);
+
+  Handle<LayoutDescriptor> full_layout_descriptor = LayoutDescriptor::New(
+      map, descriptors, descriptors->number_of_descriptors());
+
+  int nof = 0;
+  bool switched_to_slow_mode = false;
+
+  for (int i = 0; i < number_of_descriptors; i++) {
+    PropertyDetails details = descriptors->GetDetails(i);
+
+    // This method calls LayoutDescriptor::AppendIfFastOrUseFull() internally
+    // and does all the required map-descriptors related book keeping.
+    map = TestAccessor::Map_CopyInstallDescriptors(map, i, descriptors,
+                                                   full_layout_descriptor);
+
+    LayoutDescriptor* layout_desc = map->layout_descriptor();
+
+    if (layout_desc->IsSlowLayout()) {
+      switched_to_slow_mode = true;
+      CHECK_EQ(*full_layout_descriptor, layout_desc);
+    } else {
+      CHECK(!switched_to_slow_mode);
+      if (details.type() == FIELD) {
+        nof++;
+        int field_index = details.field_index();
+        int field_width_in_words = details.field_width_in_words();
+
+        bool is_inobject = field_index < map->inobject_properties();
+        for (int bit = 0; bit < field_width_in_words; bit++) {
+          CHECK_EQ(is_inobject && details.representation().IsDouble(),
+                   !layout_desc->IsTagged(field_index + bit));
+        }
+        CHECK(layout_desc->IsTagged(field_index + field_width_in_words));
+      }
+    }
+    DCHECK(map->layout_descriptor()->IsConsistentWithMap(*map));
+  }
+
+  Handle<LayoutDescriptor> layout_descriptor = map->GetLayoutDescriptor();
+  DCHECK(layout_descriptor->IsConsistentWithMap(*map));
+  return layout_descriptor;
+}
+
+
+TEST(LayoutDescriptorAppendIfFastOrUseFull) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    props[i] = static_cast<PropertyKind>(i % PROP_KIND_NUMBER);
+  }
+  Handle<DescriptorArray> descriptors =
+      CreateDescriptorArray(isolate, props, kPropsCount);
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, 0, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, 13, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kSmiValueSize, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kSmiValueSize * 2, descriptors, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kPropsCount, descriptors, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+}
+
+
+TEST(LayoutDescriptorAppendIfFastOrUseFullAllDoubles) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<LayoutDescriptor> layout_descriptor;
+  const int kPropsCount = kSmiValueSize * 3;
+  PropertyKind props[kPropsCount];
+  for (int i = 0; i < kPropsCount; i++) {
+    props[i] = PROP_DOUBLE;
+  }
+  Handle<DescriptorArray> descriptors =
+      CreateDescriptorArray(isolate, props, kPropsCount);
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, 0, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, 13, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kSmiValueSize, descriptors, kPropsCount);
+  CHECK(!layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kSmiValueSize + 1, descriptors, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kSmiValueSize * 2, descriptors, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+      isolate, kPropsCount, descriptors, kPropsCount);
+  CHECK(layout_descriptor->IsSlowLayout());
+
+  {
+    // Ensure layout descriptor switches into slow mode at the right moment.
+    layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+        isolate, kPropsCount, descriptors, kSmiValueSize);
+    CHECK(!layout_descriptor->IsSlowLayout());
+
+    layout_descriptor = TestLayoutDescriptorAppendIfFastOrUseFull(
+        isolate, kPropsCount, descriptors, kSmiValueSize + 1);
+    CHECK(layout_descriptor->IsSlowLayout());
+  }
+}
+
+
+TEST(StoreBufferScanOnScavenge) {
+  CcTest::InitializeVM();
+  Isolate* isolate = CcTest::i_isolate();
+  Factory* factory = isolate->factory();
+  v8::HandleScope scope(CcTest::isolate());
+
+  CompileRun(
+      "function A() {"
+      "  this.x = 42.5;"
+      "  this.o = {};"
+      "};"
+      "var o = new A();");
+
+  Handle<String> obj_name = factory->InternalizeUtf8String("o");
+
+  Handle<Object> obj_value =
+      Object::GetProperty(isolate->global_object(), obj_name).ToHandleChecked();
+  CHECK(obj_value->IsJSObject());
+  Handle<JSObject> obj = Handle<JSObject>::cast(obj_value);
+
+  {
+    // Ensure the object is properly set up.
+    Map* map = obj->map();
+    DescriptorArray* descriptors = map->instance_descriptors();
+    CHECK(map->NumberOfOwnDescriptors() == 2);
+    CHECK(descriptors->GetDetails(0).representation().IsDouble());
+    CHECK(descriptors->GetDetails(1).representation().IsHeapObject());
+    FieldIndex field_index = FieldIndex::ForDescriptor(map, 0);
+    CHECK(field_index.is_inobject() && field_index.is_double());
+    CHECK_EQ(FLAG_unbox_double_fields, map->IsUnboxedDoubleField(field_index));
+    if (FLAG_unbox_double_fields) {
+      CHECK_EQ(42.5, obj->RawFastDoublePropertyAt(field_index));
+    }
+  }
+  CHECK(isolate->heap()->new_space()->Contains(*obj));
+
+  // Trigger GCs so that the newly allocated object moves to old gen.
+  SimulateFullSpace(CcTest::heap()->old_pointer_space());
+  CcTest::heap()->CollectGarbage(i::NEW_SPACE);  // in survivor space now
+  CcTest::heap()->CollectGarbage(i::NEW_SPACE);  // in old gen now
+
+  CHECK(isolate->heap()->old_pointer_space()->Contains(*obj));
+
+  // Create temp object in the new space.
+  Handle<JSArray> temp = factory->NewJSArray(FAST_ELEMENTS, NOT_TENURED);
+  CHECK(isolate->heap()->new_space()->Contains(*temp));
+
+  // Construct a double value that looks like a pointer to the new space object
+  // and store it into the obj.
+  Address fake_object = reinterpret_cast<Address>(*temp) + kPointerSize;
+  double boom_value = bit_cast<double>(fake_object);
+
+  FieldIndex field_index = FieldIndex::ForDescriptor(obj->map(), 0);
+  obj->FastPropertyAtPut(field_index,
+                         *factory->NewHeapNumber(boom_value, MUTABLE));
+
+  // Enforce scan on scavenge for the obj's page.
+  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
+  chunk->set_scan_on_scavenge(true);
+
+  // Trigger GCs and force evacuation. Should not crash there.
+  CcTest::heap()->CollectAllGarbage(i::Heap::kNoGCFlags);
+}
+
+#endif