diff -r 000000000000 -r 6474c204b198 js/src/vm/ObjectImpl.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/vm/ObjectImpl.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,1014 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_ObjectImpl_h
+#define vm_ObjectImpl_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+
+#include <stdint.h>
+
+#include "jsfriendapi.h"
+#include "jsinfer.h"
+#include "NamespaceImports.h"
+
+#include "gc/Barrier.h"
+#include "gc/Heap.h"
+#include "gc/Marking.h"
+#include "js/Value.h"
+#include "vm/NumericConversions.h"
+#include "vm/Shape.h"
+#include "vm/String.h"
+
+namespace js {
+
+class ObjectImpl;
+class Nursery;
+class Shape;
+
+/*
+ * To really poison a set of values, using 'magic' or 'undefined' isn't good
+ * enough since often these will just be ignored by buggy code (see bug 629974)
+ * in debug builds and crash in release builds. Instead, we use a safe-for-crash
+ * pointer.
+ */
+static MOZ_ALWAYS_INLINE void
+Debug_SetValueRangeToCrashOnTouch(Value *beg, Value *end)
+{
+#ifdef DEBUG
+    for (Value *v = beg; v != end; ++v)
+        v->setObject(*reinterpret_cast<JSObject *>(0x42));
+#endif
+}
+
+static MOZ_ALWAYS_INLINE void
+Debug_SetValueRangeToCrashOnTouch(Value *vec, size_t len)
+{
+#ifdef DEBUG
+    Debug_SetValueRangeToCrashOnTouch(vec, vec + len);
+#endif
+}
+
+static MOZ_ALWAYS_INLINE void
+Debug_SetValueRangeToCrashOnTouch(HeapValue *vec, size_t len)
+{
+#ifdef DEBUG
+    Debug_SetValueRangeToCrashOnTouch((Value *) vec, len);
+#endif
+}
+
+static MOZ_ALWAYS_INLINE void
+Debug_SetSlotRangeToCrashOnTouch(HeapSlot *vec, uint32_t len)
+{
+#ifdef DEBUG
+    Debug_SetValueRangeToCrashOnTouch((Value *) vec, len);
+#endif
+}
+
+static MOZ_ALWAYS_INLINE void
+Debug_SetSlotRangeToCrashOnTouch(HeapSlot *begin, HeapSlot *end)
+{
+#ifdef DEBUG
+    Debug_SetValueRangeToCrashOnTouch((Value *) begin, end - begin);
+#endif
+}
+
+class ArrayObject;
+
+/*
+ * ES6 20130308 draft 8.4.2.4 ArraySetLength.
+ *
+ * |id| must be "length", |attrs| are the attributes to be used for the newly-
+ * changed length property, |value| is the value for the new length, and
+ * |setterIsStrict| indicates whether invalid changes will cause a TypeError
+ * to be thrown.
+ */
+template <ExecutionMode mode>
+extern bool
+ArraySetLength(typename ExecutionModeTraits<mode>::ContextType cx,
+               Handle<ArrayObject*> obj, HandleId id,
+               unsigned attrs, HandleValue value, bool setterIsStrict);
+
+/*
+ * Elements header used for all objects. The elements component of such objects
+ * offers an efficient representation for all or some of the indexed properties
+ * of the object, using a flat array of Values rather than a shape hierarchy
+ * stored in the object's slots. This structure is immediately followed by an
+ * array of elements, with the elements member in an object pointing to the
+ * beginning of that array (the end of this structure).
+ * See below for usage of this structure.
+ *
+ * The sets of properties represented by an object's elements and slots
+ * are disjoint. The elements contain only indexed properties, while the slots
+ * can contain both named and indexed properties; any indexes in the slots are
+ * distinct from those in the elements. If isIndexed() is false for an object,
+ * all indexed properties (if any) are stored in the dense elements.
+ *
+ * Indexes will be stored in the object's slots instead of its elements in
+ * the following case:
+ *  - there are more than MIN_SPARSE_INDEX slots total and the load factor
+ *    (COUNT / capacity) is less than 0.25
+ *  - a property is defined that has non-default property attributes.
+ *
+ * We track these pieces of metadata for dense elements:
+ *  - The length property as a uint32_t, accessible for array objects with
+ *    ArrayObject::{length,setLength}().  This is unused for non-arrays.
+ *  - The number of element slots (capacity), gettable with
+ *    getDenseElementsCapacity().
+ *  - The array's initialized length, accessible with
+ *    getDenseElementsInitializedLength().
+ *
+ * Holes in the array are represented by MagicValue(JS_ELEMENTS_HOLE) values.
+ * These indicate indexes which are not dense properties of the array. The
+ * property may, however, be held by the object's properties.
+ *
+ * The capacity and length of an object's elements are almost entirely
+ * unrelated!  In general the length may be greater than, less than, or equal
+ * to the capacity.  The first case occurs with |new Array(100)|.  The length
+ * is 100, but the capacity remains 0 (indices below length and above capacity
+ * must be treated as holes) until elements between capacity and length are
+ * set.  The other two cases are common, depending upon the number of elements
+ * in an array and the underlying allocator used for element storage.
+ *
+ * The only case in which the capacity and length of an object's elements are
+ * related is when the object is an array with non-writable length.  In this
+ * case the capacity is always less than or equal to the length.  This permits
+ * JIT code to optimize away the check for non-writable length when assigning
+ * to possibly out-of-range elements: such code already has to check for
+ * |index < capacity|, and fallback code checks for non-writable length.
+ *
+ * The initialized length of an object specifies the number of elements that
+ * have been initialized. All elements above the initialized length are
+ * holes in the object, and the memory for all elements between the initialized
+ * length and capacity is left uninitialized. The initialized length is some
+ * value less than or equal to both the object's length and the object's
+ * capacity.
+ *
+ * There is flexibility in exactly the value the initialized length must hold,
+ * e.g. if an array has length 5, capacity 10, completely empty, it is valid
+ * for the initialized length to be any value between zero and 5, as long as
+ * the in memory values below the initialized length have been initialized with
+ * a hole value. However, in such cases we want to keep the initialized length
+ * as small as possible: if the object is known to have no hole values below
+ * its initialized length, then it is "packed" and can be accessed much faster
+ * by JIT code.
+ *
+ * Elements do not track property creation order, so enumerating the elements
+ * of an object does not necessarily visit indexes in the order they were
+ * created.
+ */
+class ObjectElements
+{
+  public:
+    enum Flags {
+        CONVERT_DOUBLE_ELEMENTS     = 0x1,
+
+        // Present only if these elements correspond to an array with
+        // non-writable length; never present for non-arrays.
+        NONWRITABLE_ARRAY_LENGTH    = 0x2
+    };
+
+  private:
+    friend class ::JSObject;
+    friend class ObjectImpl;
+    friend class ArrayObject;
+    friend class Nursery;
+
+    template <ExecutionMode mode>
+    friend bool
+    ArraySetLength(typename ExecutionModeTraits<mode>::ContextType cx,
+                   Handle<ArrayObject*> obj, HandleId id,
+                   unsigned attrs, HandleValue value, bool setterIsStrict);
+
+    /* See Flags enum above. */
+    uint32_t flags;
+
+    /*
+     * Number of initialized elements. This is <= the capacity, and for arrays
+     * is <= the length. Memory for elements above the initialized length is
+     * uninitialized, but values between the initialized length and the proper
+     * length are conceptually holes.
+     */
+    uint32_t initializedLength;
+
+    /* Number of allocated slots. */
+    uint32_t capacity;
+
+    /* 'length' property of array objects, unused for other objects. */
+    uint32_t length;
+
+    void staticAsserts() {
+        static_assert(sizeof(ObjectElements) == VALUES_PER_HEADER * sizeof(Value),
+                      "Elements size and values-per-Elements mismatch");
+    }
+
+    bool shouldConvertDoubleElements() const {
+        return flags & CONVERT_DOUBLE_ELEMENTS;
+    }
+    void setShouldConvertDoubleElements() {
+        flags |= CONVERT_DOUBLE_ELEMENTS;
+    }
+    void clearShouldConvertDoubleElements() {
+        flags &= ~CONVERT_DOUBLE_ELEMENTS;
+    }
+    bool hasNonwritableArrayLength() const {
+        return flags & NONWRITABLE_ARRAY_LENGTH;
+    }
+    void setNonwritableArrayLength() {
+        flags |= NONWRITABLE_ARRAY_LENGTH;
+    }
+
+  public:
+    MOZ_CONSTEXPR ObjectElements(uint32_t capacity, uint32_t length)
+      : flags(0), initializedLength(0), capacity(capacity), length(length)
+    {}
+
+    HeapSlot *elements() {
+        return reinterpret_cast<HeapSlot*>(uintptr_t(this) + sizeof(ObjectElements));
+    }
+    static ObjectElements * fromElements(HeapSlot *elems) {
+        return reinterpret_cast<ObjectElements*>(uintptr_t(elems) - sizeof(ObjectElements));
+    }
+
+    static int offsetOfFlags() {
+        return int(offsetof(ObjectElements, flags)) - int(sizeof(ObjectElements));
+    }
+    static int offsetOfInitializedLength() {
+        return int(offsetof(ObjectElements, initializedLength)) - int(sizeof(ObjectElements));
+    }
+    static int offsetOfCapacity() {
+        return int(offsetof(ObjectElements, capacity)) - int(sizeof(ObjectElements));
+    }
+    static int offsetOfLength() {
+        return int(offsetof(ObjectElements, length)) - int(sizeof(ObjectElements));
+    }
+
+    static bool ConvertElementsToDoubles(JSContext *cx, uintptr_t elements);
+
+    static const size_t VALUES_PER_HEADER = 2;
+};
+
+/* Shared singleton for objects with no elements. */
+extern HeapSlot *const emptyObjectElements;
+
+struct Class;
+struct GCMarker;
+struct ObjectOps;
+class Shape;
+
+class NewObjectCache;
+class TaggedProto;
+
+inline Value
+ObjectValue(ObjectImpl &obj);
+
+#ifdef DEBUG
+static inline bool
+IsObjectValueInCompartment(js::Value v, JSCompartment *comp);
+#endif
+
+/*
+ * ObjectImpl specifies the internal implementation of an object.  (In contrast
+ * JSObject specifies an "external" interface, at the conceptual level of that
+ * exposed in ECMAScript.)
+ *
+ * The |shape_| member stores the shape of the object, which includes the
+ * object's class and the layout of all its properties.
+ *
+ * The |type_| member stores the type of the object, which contains its
+ * prototype object and the possible types of its properties.
+ *
+ * The rest of the object stores its named properties and indexed elements.
+ * These are stored separately from one another. Objects are followed by a
+ * variable-sized array of values for inline storage, which may be used by
+ * either properties of native objects (fixed slots), by elements (fixed
+ * elements), or by other data for certain kinds of objects, such as
+ * ArrayBufferObjects and TypedArrayObjects.
+ *
+ * Two native objects with the same shape are guaranteed to have the same
+ * number of fixed slots.
+ *
+ * Named property storage can be split between fixed slots and a dynamically
+ * allocated array (the slots member). For an object with N fixed slots, shapes
+ * with slots [0..N-1] are stored in the fixed slots, and the remainder are
+ * stored in the dynamic array. If all properties fit in the fixed slots, the
+ * 'slots' member is nullptr.
+ *
+ * Elements are indexed via the 'elements' member. This member can point to
+ * either the shared emptyObjectElements singleton, into the inline value array
+ * (the address of the third value, to leave room for a ObjectElements header;
+ * in this case numFixedSlots() is zero) or to a dynamically allocated array.
+ *
+ * Only certain combinations of slots and elements storage are possible.
+ *
+ * - For native objects, slots and elements may both be non-empty. The
+ *   slots may be either names or indexes; no indexed property will be in both
+ *   the slots and elements.
+ *
+ * - For non-native objects, slots and elements are both empty.
+ *
+ * The members of this class are currently protected; in the long run this will
+ * will change so that some members are private, and only certain methods that
+ * act upon them will be protected.
+ */
+class ObjectImpl : public gc::BarrieredCell<ObjectImpl>
+{
+    friend Zone *js::gc::BarrieredCell<ObjectImpl>::zone() const;
+    friend Zone *js::gc::BarrieredCell<ObjectImpl>::zoneFromAnyThread() const;
+
+  protected:
+    /*
+     * Shape of the object, encodes the layout of the object's properties and
+     * all other information about its structure. See vm/Shape.h.
+     */
+    HeapPtrShape shape_;
+
+    /*
+     * The object's type and prototype. For objects with the LAZY_TYPE flag
+     * set, this is the prototype's default 'new' type and can only be used
+     * to get that prototype.
+     */
+    HeapPtrTypeObject type_;
+
+    HeapSlot *slots;     /* Slots for object properties. */
+    HeapSlot *elements;  /* Slots for object elements. */
+
+    friend bool
+    ArraySetLength(JSContext *cx, Handle<ArrayObject*> obj, HandleId id, unsigned attrs,
+                   HandleValue value, bool setterIsStrict);
+
+  private:
+    static void staticAsserts() {
+        static_assert(sizeof(ObjectImpl) == sizeof(shadow::Object),
+                      "shadow interface must match actual implementation");
+        static_assert(sizeof(ObjectImpl) % sizeof(Value) == 0,
+                      "fixed slots after an object must be aligned");
+
+        static_assert(offsetof(ObjectImpl, shape_) == offsetof(shadow::Object, shape),
+                      "shadow shape must match actual shape");
+        static_assert(offsetof(ObjectImpl, type_) == offsetof(shadow::Object, type),
+                      "shadow type must match actual type");
+        static_assert(offsetof(ObjectImpl, slots) == offsetof(shadow::Object, slots),
+                      "shadow slots must match actual slots");
+        static_assert(offsetof(ObjectImpl, elements) == offsetof(shadow::Object, _1),
+                      "shadow placeholder must match actual elements");
+    }
+
+    JSObject * asObjectPtr() { return reinterpret_cast<JSObject *>(this); }
+    const JSObject * asObjectPtr() const { return reinterpret_cast<const JSObject *>(this); }
+
+    friend inline Value ObjectValue(ObjectImpl &obj);
+
+    /* These functions are public, and they should remain public. */
+
+  public:
+    TaggedProto getTaggedProto() const {
+        return type_->proto();
+    }
+
+    bool hasTenuredProto() const;
+
+    const Class *getClass() const {
+        return type_->clasp();
+    }
+
+    static inline bool
+    isExtensible(ExclusiveContext *cx, Handle<ObjectImpl*> obj, bool *extensible);
+
+    // Indicates whether a non-proxy is extensible.  Don't call on proxies!
+    // This method really shouldn't exist -- but there are a few internal
+    // places that want it (JITs and the like), and it'd be a pain to mark them
+    // all as friends.
+    bool nonProxyIsExtensible() const {
+        MOZ_ASSERT(!isProxy());
+
+        // [[Extensible]] for ordinary non-proxy objects is an object flag.
+        return !lastProperty()->hasObjectFlag(BaseShape::NOT_EXTENSIBLE);
+    }
+
+#ifdef DEBUG
+    bool isProxy() const;
+#endif
+
+    // Attempt to change the [[Extensible]] bit on |obj| to false.  Callers
+    // must ensure that |obj| is currently extensible before calling this!
+    static bool
+    preventExtensions(JSContext *cx, Handle<ObjectImpl*> obj);
+
+    HeapSlotArray getDenseElements() {
+        JS_ASSERT(isNative());
+        return HeapSlotArray(elements);
+    }
+    const Value &getDenseElement(uint32_t idx) {
+        JS_ASSERT(isNative());
+        MOZ_ASSERT(idx < getDenseInitializedLength());
+        return elements[idx];
+    }
+    bool containsDenseElement(uint32_t idx) {
+        JS_ASSERT(isNative());
+        return idx < getDenseInitializedLength() && !elements[idx].isMagic(JS_ELEMENTS_HOLE);
+    }
+    uint32_t getDenseInitializedLength() {
+        JS_ASSERT(getClass()->isNative());
+        return getElementsHeader()->initializedLength;
+    }
+    uint32_t getDenseCapacity() {
+        JS_ASSERT(getClass()->isNative());
+        return getElementsHeader()->capacity;
+    }
+
+  protected:
+#ifdef DEBUG
+    void checkShapeConsistency();
+#else
+    void checkShapeConsistency() { }
+#endif
+
+    Shape *
+    replaceWithNewEquivalentShape(ThreadSafeContext *cx,
+                                  Shape *existingShape, Shape *newShape = nullptr);
+
+    enum GenerateShape {
+        GENERATE_NONE,
+        GENERATE_SHAPE
+    };
+
+    bool setFlag(ExclusiveContext *cx, /*BaseShape::Flag*/ uint32_t flag,
+                 GenerateShape generateShape = GENERATE_NONE);
+    bool clearFlag(ExclusiveContext *cx, /*BaseShape::Flag*/ uint32_t flag);
+
+    bool toDictionaryMode(ThreadSafeContext *cx);
+
+  private:
+    friend class Nursery;
+
+    /*
+     * Get internal pointers to the range of values starting at start and
+     * running for length.
+     */
+    void getSlotRangeUnchecked(uint32_t start, uint32_t length,
+                               HeapSlot **fixedStart, HeapSlot **fixedEnd,
+                               HeapSlot **slotsStart, HeapSlot **slotsEnd)
+    {
+        MOZ_ASSERT(start + length >= start);
+
+        uint32_t fixed = numFixedSlots();
+        if (start < fixed) {
+            if (start + length < fixed) {
+                *fixedStart = &fixedSlots()[start];
+                *fixedEnd = &fixedSlots()[start + length];
+                *slotsStart = *slotsEnd = nullptr;
+            } else {
+                uint32_t localCopy = fixed - start;
+                *fixedStart = &fixedSlots()[start];
+                *fixedEnd = &fixedSlots()[start + localCopy];
+                *slotsStart = &slots[0];
+                *slotsEnd = &slots[length - localCopy];
+            }
+        } else {
+            *fixedStart = *fixedEnd = nullptr;
+            *slotsStart = &slots[start - fixed];
+            *slotsEnd = &slots[start - fixed + length];
+        }
+    }
+
+    void getSlotRange(uint32_t start, uint32_t length,
+                      HeapSlot **fixedStart, HeapSlot **fixedEnd,
+                      HeapSlot **slotsStart, HeapSlot **slotsEnd)
+    {
+        MOZ_ASSERT(slotInRange(start + length, SENTINEL_ALLOWED));
+        getSlotRangeUnchecked(start, length, fixedStart, fixedEnd, slotsStart, slotsEnd);
+    }
+
+  protected:
+    friend struct GCMarker;
+    friend class Shape;
+    friend class NewObjectCache;
+
+    void invalidateSlotRange(uint32_t start, uint32_t length) {
+#ifdef DEBUG
+        HeapSlot *fixedStart, *fixedEnd, *slotsStart, *slotsEnd;
+        getSlotRange(start, length, &fixedStart, &fixedEnd, &slotsStart, &slotsEnd);
+        Debug_SetSlotRangeToCrashOnTouch(fixedStart, fixedEnd);
+        Debug_SetSlotRangeToCrashOnTouch(slotsStart, slotsEnd);
+#endif /* DEBUG */
+    }
+
+    void initializeSlotRange(uint32_t start, uint32_t count);
+
+    /*
+     * Initialize a flat array of slots to this object at a start slot.  The
+     * caller must ensure that are enough slots.
+     */
+    void initSlotRange(uint32_t start, const Value *vector, uint32_t length);
+
+    /*
+     * Copy a flat array of slots to this object at a start slot. Caller must
+     * ensure there are enough slots in this object.
+     */
+    void copySlotRange(uint32_t start, const Value *vector, uint32_t length);
+
+#ifdef DEBUG
+    enum SentinelAllowed {
+        SENTINEL_NOT_ALLOWED,
+        SENTINEL_ALLOWED
+    };
+
+    /*
+     * Check that slot is in range for the object's allocated slots.
+     * If sentinelAllowed then slot may equal the slot capacity.
+     */
+    bool slotInRange(uint32_t slot, SentinelAllowed sentinel = SENTINEL_NOT_ALLOWED) const;
+#endif
+
+    /*
+     * Minimum size for dynamically allocated slots in normal Objects.
+     * ArrayObjects don't use this limit and can have a lower slot capacity,
+     * since they normally don't have a lot of slots.
+     */
+    static const uint32_t SLOT_CAPACITY_MIN = 8;
+
+    HeapSlot *fixedSlots() const {
+        return reinterpret_cast<HeapSlot *>(uintptr_t(this) + sizeof(ObjectImpl));
+    }
+
+    /*
+     * These functions are currently public for simplicity; in the long run
+     * it may make sense to make at least some of them private.
+     */
+
+  public:
+    Shape * lastProperty() const {
+        MOZ_ASSERT(shape_);
+        return shape_;
+    }
+
+    bool generateOwnShape(ThreadSafeContext *cx, js::Shape *newShape = nullptr) {
+        return replaceWithNewEquivalentShape(cx, lastProperty(), newShape);
+    }
+
+    JSCompartment *compartment() const {
+        return lastProperty()->base()->compartment();
+    }
+
+    bool isNative() const {
+        return lastProperty()->isNative();
+    }
+
+    types::TypeObject *type() const {
+        MOZ_ASSERT(!hasLazyType());
+        return typeRaw();
+    }
+
+    types::TypeObject *typeRaw() const {
+        return type_;
+    }
+
+    uint32_t numFixedSlots() const {
+        return reinterpret_cast<const shadow::Object *>(this)->numFixedSlots();
+    }
+
+    /*
+     * Whether this is the only object which has its specified type. This
+     * object will have its type constructed lazily as needed by analysis.
+     */
+    bool hasSingletonType() const {
+        return !!type_->singleton();
+    }
+
+    /*
+     * Whether the object's type has not been constructed yet. If an object
+     * might have a lazy type, use getType() below, otherwise type().
+     */
+    bool hasLazyType() const {
+        return type_->lazy();
+    }
+
+    uint32_t slotSpan() const {
+        if (inDictionaryMode())
+            return lastProperty()->base()->slotSpan();
+        return lastProperty()->slotSpan();
+    }
+
+    /* Compute dynamicSlotsCount() for this object. */
+    uint32_t numDynamicSlots() const {
+        return dynamicSlotsCount(numFixedSlots(), slotSpan(), getClass());
+    }
+
+
+    Shape *nativeLookup(ExclusiveContext *cx, jsid id);
+    Shape *nativeLookup(ExclusiveContext *cx, PropertyName *name) {
+        return nativeLookup(cx, NameToId(name));
+    }
+
+    bool nativeContains(ExclusiveContext *cx, jsid id) {
+        return nativeLookup(cx, id) != nullptr;
+    }
+    bool nativeContains(ExclusiveContext *cx, PropertyName* name) {
+        return nativeLookup(cx, name) != nullptr;
+    }
+    bool nativeContains(ExclusiveContext *cx, Shape* shape) {
+        return nativeLookup(cx, shape->propid()) == shape;
+    }
+
+    /* Contextless; can be called from parallel code. */
+    Shape *nativeLookupPure(jsid id);
+    Shape *nativeLookupPure(PropertyName *name) {
+        return nativeLookupPure(NameToId(name));
+    }
+
+    bool nativeContainsPure(jsid id) {
+        return nativeLookupPure(id) != nullptr;
+    }
+    bool nativeContainsPure(PropertyName* name) {
+        return nativeContainsPure(NameToId(name));
+    }
+    bool nativeContainsPure(Shape* shape) {
+        return nativeLookupPure(shape->propid()) == shape;
+    }
+
+    const JSClass *getJSClass() const {
+        return Jsvalify(getClass());
+    }
+    bool hasClass(const Class *c) const {
+        return getClass() == c;
+    }
+    const ObjectOps *getOps() const {
+        return &getClass()->ops;
+    }
+
+    /*
+     * An object is a delegate if it is on another object's prototype or scope
+     * chain, and therefore the delegate might be asked implicitly to get or
+     * set a property on behalf of another object. Delegates may be accessed
+     * directly too, as may any object, but only those objects linked after the
+     * head of any prototype or scope chain are flagged as delegates. This
+     * definition helps to optimize shape-based property cache invalidation
+     * (see Purge{Scope,Proto}Chain in jsobj.cpp).
+     */
+    bool isDelegate() const {
+        return lastProperty()->hasObjectFlag(BaseShape::DELEGATE);
+    }
+
+    /*
+     * Return true if this object is a native one that has been converted from
+     * shared-immutable prototype-rooted shape storage to dictionary-shapes in
+     * a doubly-linked list.
+     */
+    bool inDictionaryMode() const {
+        return lastProperty()->inDictionary();
+    }
+
+    const Value &getSlot(uint32_t slot) const {
+        MOZ_ASSERT(slotInRange(slot));
+        uint32_t fixed = numFixedSlots();
+        if (slot < fixed)
+            return fixedSlots()[slot];
+        return slots[slot - fixed];
+    }
+
+    const HeapSlot *getSlotAddressUnchecked(uint32_t slot) const {
+        uint32_t fixed = numFixedSlots();
+        if (slot < fixed)
+            return fixedSlots() + slot;
+        return slots + (slot - fixed);
+    }
+
+    HeapSlot *getSlotAddressUnchecked(uint32_t slot) {
+        const ObjectImpl *obj = static_cast<const ObjectImpl*>(this);
+        return const_cast<HeapSlot*>(obj->getSlotAddressUnchecked(slot));
+    }
+
+    HeapSlot *getSlotAddress(uint32_t slot) {
+        /*
+         * This can be used to get the address of the end of the slots for the
+         * object, which may be necessary when fetching zero-length arrays of
+         * slots (e.g. for callObjVarArray).
+         */
+        MOZ_ASSERT(slotInRange(slot, SENTINEL_ALLOWED));
+        return getSlotAddressUnchecked(slot);
+    }
+
+    const HeapSlot *getSlotAddress(uint32_t slot) const {
+        /*
+         * This can be used to get the address of the end of the slots for the
+         * object, which may be necessary when fetching zero-length arrays of
+         * slots (e.g. for callObjVarArray).
+         */
+        MOZ_ASSERT(slotInRange(slot, SENTINEL_ALLOWED));
+        return getSlotAddressUnchecked(slot);
+    }
+
+    HeapSlot &getSlotRef(uint32_t slot) {
+        MOZ_ASSERT(slotInRange(slot));
+        return *getSlotAddress(slot);
+    }
+
+    const HeapSlot &getSlotRef(uint32_t slot) const {
+        MOZ_ASSERT(slotInRange(slot));
+        return *getSlotAddress(slot);
+    }
+
+    HeapSlot &nativeGetSlotRef(uint32_t slot) {
+        JS_ASSERT(isNative() && slot < slotSpan());
+        return getSlotRef(slot);
+    }
+    const Value &nativeGetSlot(uint32_t slot) const {
+        JS_ASSERT(isNative() && slot < slotSpan());
+        return getSlot(slot);
+    }
+
+    void setSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(slotInRange(slot));
+        MOZ_ASSERT(IsObjectValueInCompartment(value, compartment()));
+        getSlotRef(slot).set(this->asObjectPtr(), HeapSlot::Slot, slot, value);
+    }
+
+    inline void setCrossCompartmentSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(slotInRange(slot));
+        getSlotRef(slot).set(this->asObjectPtr(), HeapSlot::Slot, slot, value);
+    }
+
+    void initSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(getSlot(slot).isUndefined());
+        MOZ_ASSERT(slotInRange(slot));
+        MOZ_ASSERT(IsObjectValueInCompartment(value, compartment()));
+        initSlotUnchecked(slot, value);
+    }
+
+    void initCrossCompartmentSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(getSlot(slot).isUndefined());
+        MOZ_ASSERT(slotInRange(slot));
+        initSlotUnchecked(slot, value);
+    }
+
+    void initSlotUnchecked(uint32_t slot, const Value &value) {
+        getSlotAddressUnchecked(slot)->init(this->asObjectPtr(), HeapSlot::Slot, slot, value);
+    }
+
+    /* For slots which are known to always be fixed, due to the way they are allocated. */
+
+    HeapSlot &getFixedSlotRef(uint32_t slot) {
+        MOZ_ASSERT(slot < numFixedSlots());
+        return fixedSlots()[slot];
+    }
+
+    const Value &getFixedSlot(uint32_t slot) const {
+        MOZ_ASSERT(slot < numFixedSlots());
+        return fixedSlots()[slot];
+    }
+
+    void setFixedSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(slot < numFixedSlots());
+        fixedSlots()[slot].set(this->asObjectPtr(), HeapSlot::Slot, slot, value);
+    }
+
+    void initFixedSlot(uint32_t slot, const Value &value) {
+        MOZ_ASSERT(slot < numFixedSlots());
+        fixedSlots()[slot].init(this->asObjectPtr(), HeapSlot::Slot, slot, value);
+    }
+
+    /*
+     * Get the number of dynamic slots to allocate to cover the properties in
+     * an object with the given number of fixed slots and slot span. The slot
+     * capacity is not stored explicitly, and the allocated size of the slot
+     * array is kept in sync with this count.
+     */
+    static uint32_t dynamicSlotsCount(uint32_t nfixed, uint32_t span, const Class *clasp);
+
+    /* Memory usage functions. */
+    size_t tenuredSizeOfThis() const {
+        return js::gc::Arena::thingSize(tenuredGetAllocKind());
+    }
+
+    /* Elements accessors. */
+
+    ObjectElements * getElementsHeader() const {
+        return ObjectElements::fromElements(elements);
+    }
+
+    inline HeapSlot *fixedElements() const {
+        static_assert(2 * sizeof(Value) == sizeof(ObjectElements),
+                      "when elements are stored inline, the first two "
+                      "slots will hold the ObjectElements header");
+        return &fixedSlots()[2];
+    }
+
+#ifdef DEBUG
+    bool canHaveNonEmptyElements();
+#endif
+
+    void setFixedElements() {
+        JS_ASSERT(canHaveNonEmptyElements());
+        this->elements = fixedElements();
+    }
+
+    inline bool hasDynamicElements() const {
+        /*
+         * Note: for objects with zero fixed slots this could potentially give
+         * a spurious 'true' result, if the end of this object is exactly
+         * aligned with the end of its arena and dynamic slots are allocated
+         * immediately afterwards. Such cases cannot occur for dense arrays
+         * (which have at least two fixed slots) and can only result in a leak.
+         */
+        return !hasEmptyElements() && elements != fixedElements();
+    }
+
+    inline bool hasFixedElements() const {
+        return elements == fixedElements();
+    }
+
+    inline bool hasEmptyElements() const {
+        return elements == emptyObjectElements;
+    }
+
+    /*
+     * Get a pointer to the unused data in the object's allocation immediately
+     * following this object, for use with objects which allocate a larger size
+     * class than they need and store non-elements data inline.
+     */
+    inline void *fixedData(size_t nslots) const;
+
+    /* GC support. */
+    static ThingRootKind rootKind() { return THING_ROOT_OBJECT; }
+
+    inline void privateWriteBarrierPre(void **oldval);
+
+    void privateWriteBarrierPost(void **pprivate) {
+#ifdef JSGC_GENERATIONAL
+        shadowRuntimeFromAnyThread()->gcStoreBufferPtr()->putCell(reinterpret_cast<js::gc::Cell **>(pprivate));
+#endif
+    }
+
+    void markChildren(JSTracer *trc);
+
+    /* Private data accessors. */
+
+    inline void *&privateRef(uint32_t nfixed) const { /* XXX should be private, not protected! */
+        /*
+         * The private pointer of an object can hold any word sized value.
+         * Private pointers are stored immediately after the last fixed slot of
+         * the object.
+         */
+        MOZ_ASSERT(nfixed == numFixedSlots());
+        MOZ_ASSERT(hasPrivate());
+        HeapSlot *end = &fixedSlots()[nfixed];
+        return *reinterpret_cast<void**>(end);
+    }
+
+    bool hasPrivate() const {
+        return getClass()->hasPrivate();
+    }
+    void *getPrivate() const {
+        return privateRef(numFixedSlots());
+    }
+    void setPrivate(void *data) {
+        void **pprivate = &privateRef(numFixedSlots());
+        privateWriteBarrierPre(pprivate);
+        *pprivate = data;
+    }
+
+    void setPrivateGCThing(gc::Cell *cell) {
+        void **pprivate = &privateRef(numFixedSlots());
+        privateWriteBarrierPre(pprivate);
+        *pprivate = reinterpret_cast<void *>(cell);
+        privateWriteBarrierPost(pprivate);
+    }
+
+    void setPrivateUnbarriered(void *data) {
+        void **pprivate = &privateRef(numFixedSlots());
+        *pprivate = data;
+    }
+    void initPrivate(void *data) {
+        privateRef(numFixedSlots()) = data;
+    }
+
+    /* Access private data for an object with a known number of fixed slots. */
+    inline void *getPrivate(uint32_t nfixed) const {
+        return privateRef(nfixed);
+    }
+
+    /* GC Accessors */
+    void setInitialSlots(HeapSlot *newSlots) { slots = newSlots; }
+
+    /* JIT Accessors */
+    static size_t offsetOfShape() { return offsetof(ObjectImpl, shape_); }
+    HeapPtrShape *addressOfShape() { return &shape_; }
+
+    static size_t offsetOfType() { return offsetof(ObjectImpl, type_); }
+    HeapPtrTypeObject *addressOfType() { return &type_; }
+
+    static size_t offsetOfElements() { return offsetof(ObjectImpl, elements); }
+    static size_t offsetOfFixedElements() {
+        return sizeof(ObjectImpl) + sizeof(ObjectElements);
+    }
+
+    static size_t getFixedSlotOffset(size_t slot) {
+        return sizeof(ObjectImpl) + slot * sizeof(Value);
+    }
+    static size_t getPrivateDataOffset(size_t nfixed) { return getFixedSlotOffset(nfixed); }
+    static size_t offsetOfSlots() { return offsetof(ObjectImpl, slots); }
+};
+
+namespace gc {
+
+template <>
+MOZ_ALWAYS_INLINE Zone *
+BarrieredCell<ObjectImpl>::zone() const
+{
+    const ObjectImpl* obj = static_cast<const ObjectImpl*>(this);
+    JS::Zone *zone = obj->shape_->zone();
+    JS_ASSERT(CurrentThreadCanAccessZone(zone));
+    return zone;
+}
+
+template <>
+MOZ_ALWAYS_INLINE Zone *
+BarrieredCell<ObjectImpl>::zoneFromAnyThread() const
+{
+    const ObjectImpl* obj = static_cast<const ObjectImpl*>(this);
+    return obj->shape_->zoneFromAnyThread();
+}
+
+// TypeScript::global uses 0x1 as a special value.
+template<>
+/* static */ inline bool
+BarrieredCell<ObjectImpl>::isNullLike(ObjectImpl *obj)
+{
+    return IsNullTaggedPointer(obj);
+}
+
+template<>
+/* static */ inline void
+BarrieredCell<ObjectImpl>::writeBarrierPost(ObjectImpl *obj, void *addr)
+{
+#ifdef JSGC_GENERATIONAL
+    if (IsNullTaggedPointer(obj))
+        return;
+    obj->shadowRuntimeFromAnyThread()->gcStoreBufferPtr()->putCell((Cell **)addr);
+#endif
+}
+
+template<>
+/* static */ inline void
+BarrieredCell<ObjectImpl>::writeBarrierPostRelocate(ObjectImpl *obj, void *addr)
+{
+#ifdef JSGC_GENERATIONAL
+    obj->shadowRuntimeFromAnyThread()->gcStoreBufferPtr()->putRelocatableCell((Cell **)addr);
+#endif
+}
+
+template<>
+/* static */ inline void
+BarrieredCell<ObjectImpl>::writeBarrierPostRemove(ObjectImpl *obj, void *addr)
+{
+#ifdef JSGC_GENERATIONAL
+    obj->shadowRuntimeFromAnyThread()->gcStoreBufferPtr()->removeRelocatableCell((Cell **)addr);
+#endif
+}
+
+} // namespace gc
+
+inline void
+ObjectImpl::privateWriteBarrierPre(void **oldval)
+{
+#ifdef JSGC_INCREMENTAL
+    JS::shadow::Zone *shadowZone = this->shadowZoneFromAnyThread();
+    if (shadowZone->needsBarrier()) {
+        if (*oldval && getClass()->trace)
+            getClass()->trace(shadowZone->barrierTracer(), this->asObjectPtr());
+    }
+#endif
+}
+
+inline Value
+ObjectValue(ObjectImpl &obj)
+{
+    Value v;
+    v.setObject(*obj.asObjectPtr());
+    return v;
+}
+
+inline Handle<JSObject*>
+Downcast(Handle<ObjectImpl*> obj)
+{
+    return Handle<JSObject*>::fromMarkedLocation(reinterpret_cast<JSObject* const*>(obj.address()));
+}
+
+#ifdef DEBUG
+static inline bool
+IsObjectValueInCompartment(js::Value v, JSCompartment *comp)
+{
+    if (!v.isObject())
+        return true;
+    return reinterpret_cast<ObjectImpl*>(&v.toObject())->compartment() == comp;
+}
+#endif
+
+} /* namespace js */
+
+#endif /* vm_ObjectImpl_h */