CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

//       copyright notice, this list of conditions and the following

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//       with the distribution.

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//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_PROPERTY_DETAILS_H_

#define V8_PROPERTY_DETAILS_H_

#include "../include/v8.h"

#include "allocation.h"

#include "utils.h"

// Ecma-262 3rd 8.6.1

enum PropertyAttributes {

  NONE              = v8::None,

  READ_ONLY         = v8::ReadOnly,

  DONT_ENUM         = v8::DontEnum,

  DONT_DELETE       = v8::DontDelete,

  SEALED            = DONT_DELETE,

  FROZEN            = SEALED | READ_ONLY,

  SYMBOLIC          = 8,  // Used to filter symbol names

  DONT_SHOW         = DONT_ENUM | SYMBOLIC,

  ABSENT            = 16  // Used in runtime to indicate a property is absent.

  // ABSENT can never be stored in or returned from a descriptor's attributes

  // bitfield.  It is only used as a return value meaning the attributes of

  // a non-existent property.

};

namespace v8 {

namespace internal {

class Smi;

class Type;

class TypeInfo;

// Type of properties.

// Order of properties is significant.

// Must fit in the BitField PropertyDetails::TypeField.

// A copy of this is in mirror-debugger.js.

enum PropertyType {

  // Only in slow mode.

  NORMAL                    = 0,

  // Only in fast mode.

  FIELD                     = 1,

  CONSTANT                  = 2,

  CALLBACKS                 = 3,

  // Only in lookup results, not in descriptors.

  HANDLER                   = 4,

  INTERCEPTOR               = 5,

  TRANSITION                = 6,

  // Only used as a marker in LookupResult.

  NONEXISTENT               = 7

};

class Representation {

 public:

  enum Kind {

    kNone,

    kByte,

    kSmi,

    kInteger32,

    kDouble,

    kHeapObject,

    kTagged,

    kExternal,

    kNumRepresentations

  };

  Representation() : kind_(kNone) { }

  static Representation None() { return Representation(kNone); }

  static Representation Tagged() { return Representation(kTagged); }

  static Representation Byte() { return Representation(kByte); }

  static Representation Smi() { return Representation(kSmi); }

  static Representation Integer32() { return Representation(kInteger32); }

  static Representation Double() { return Representation(kDouble); }

  static Representation HeapObject() { return Representation(kHeapObject); }

  static Representation External() { return Representation(kExternal); }

  static Representation FromKind(Kind kind) { return Representation(kind); }

  // TODO(rossberg): this should die eventually.

  static Representation FromType(TypeInfo info);

  static Representation FromType(Handle<Type> type);

  bool Equals(const Representation& other) const {

    return kind_ == other.kind_;

  }

  bool IsCompatibleForLoad(const Representation& other) const {

    return (IsDouble() && other.IsDouble()) ||

        (!IsDouble() && !other.IsDouble());

  }

  bool IsCompatibleForStore(const Representation& other) const {

    return Equals(other);

  }

  bool is_more_general_than(const Representation& other) const {

    ASSERT(kind_ != kExternal);

    ASSERT(other.kind_ != kExternal);

    if (IsHeapObject()) return other.IsDouble() || other.IsNone();

    return kind_ > other.kind_;

  }

  bool fits_into(const Representation& other) const {

    return other.is_more_general_than(*this) || other.Equals(*this);

  }

  Representation generalize(Representation other) {

    if (other.fits_into(*this)) return *this;

    if (other.is_more_general_than(*this)) return other;

    return Representation::Tagged();

  }

  Kind kind() const { return static_cast<Kind>(kind_); }

  bool IsNone() const { return kind_ == kNone; }

  bool IsByte() const { return kind_ == kByte; }

  bool IsTagged() const { return kind_ == kTagged; }

  bool IsSmi() const { return kind_ == kSmi; }

  bool IsSmiOrTagged() const { return IsSmi() || IsTagged(); }

  bool IsInteger32() const { return kind_ == kInteger32; }

  bool IsSmiOrInteger32() const { return IsSmi() || IsInteger32(); }

  bool IsDouble() const { return kind_ == kDouble; }

  bool IsHeapObject() const { return kind_ == kHeapObject; }

  bool IsExternal() const { return kind_ == kExternal; }

  bool IsSpecialization() const {

    return IsByte() || IsSmi() || IsInteger32() || IsDouble();

  }

  const char* Mnemonic() const;

 private:

  explicit Representation(Kind k) : kind_(k) { }

  // Make sure kind fits in int8.

  STATIC_ASSERT(kNumRepresentations <= (1 << kBitsPerByte));

  int8_t kind_;

};

// PropertyDetails captures type and attributes for a property.

// They are used both in property dictionaries and instance descriptors.

class PropertyDetails BASE_EMBEDDED {

 public:

  PropertyDetails(PropertyAttributes attributes,

                  PropertyType type,

                  int index) {

    value_ = TypeField::encode(type)

        | AttributesField::encode(attributes)

        | DictionaryStorageField::encode(index);

    ASSERT(type == this->type());

    ASSERT(attributes == this->attributes());

  }

  PropertyDetails(PropertyAttributes attributes,

                  PropertyType type,

                  Representation representation,

                  int field_index = 0) {

    value_ = TypeField::encode(type)

        | AttributesField::encode(attributes)

        | RepresentationField::encode(EncodeRepresentation(representation))

        | FieldIndexField::encode(field_index);

  }

  int pointer() { return DescriptorPointer::decode(value_); }

  PropertyDetails set_pointer(int i) { return PropertyDetails(value_, i); }

  PropertyDetails CopyWithRepresentation(Representation representation) {

    return PropertyDetails(value_, representation);

  }

  PropertyDetails CopyAddAttributes(PropertyAttributes new_attributes) {

    new_attributes =

        static_cast<PropertyAttributes>(attributes() | new_attributes);

    return PropertyDetails(value_, new_attributes);

  }

  // Conversion for storing details as Object*.

  explicit inline PropertyDetails(Smi* smi);

  inline Smi* AsSmi();

  static uint8_t EncodeRepresentation(Representation representation) {

    return representation.kind();

  }

  static Representation DecodeRepresentation(uint32_t bits) {

    return Representation::FromKind(static_cast<Representation::Kind>(bits));

  }

  PropertyType type() { return TypeField::decode(value_); }

  PropertyAttributes attributes() const {

    return AttributesField::decode(value_);

  }

  int dictionary_index() {

    return DictionaryStorageField::decode(value_);

  }

  Representation representation() {

    ASSERT(type() != NORMAL);

    return DecodeRepresentation(RepresentationField::decode(value_));

  }

  int  field_index() {

    return FieldIndexField::decode(value_);

  }

  inline PropertyDetails AsDeleted();

  static bool IsValidIndex(int index) {

    return DictionaryStorageField::is_valid(index);

  }

  bool IsReadOnly() const { return (attributes() & READ_ONLY) != 0; }

  bool IsDontDelete() const { return (attributes() & DONT_DELETE) != 0; }

  bool IsDontEnum() const { return (attributes() & DONT_ENUM) != 0; }

  bool IsDeleted() const { return DeletedField::decode(value_) != 0;}

  // Bit fields in value_ (type, shift, size). Must be public so the

  // constants can be embedded in generated code.

  class TypeField:                public BitField<PropertyType,       0,  3> {};

  class AttributesField:          public BitField<PropertyAttributes, 3,  3> {};

  // Bit fields for normalized objects.

  class DeletedField:             public BitField<uint32_t,           6,  1> {};

  class DictionaryStorageField:   public BitField<uint32_t,           7, 24> {};

  // Bit fields for fast objects.

  class DescriptorPointer:        public BitField<uint32_t,           6, 11> {};

  class RepresentationField:      public BitField<uint32_t,          17,  3> {};

  class FieldIndexField:          public BitField<uint32_t,          20, 11> {};

  static const int kInitialIndex = 1;

 private:

  PropertyDetails(int value, int pointer) {

    value_ = DescriptorPointer::update(value, pointer);

  }

  PropertyDetails(int value, Representation representation) {

    value_ = RepresentationField::update(

        value, EncodeRepresentation(representation));

  }

  PropertyDetails(int value, PropertyAttributes attributes) {

    value_ = AttributesField::update(value, attributes);

  }

  uint32_t value_;

};

} }  // namespace v8::internal

#endif  // V8_PROPERTY_DETAILS_H_