assembler.h.svn-base

Google浏览器V8内核代码

  // Read/modify the address of a call instruction. This is used to relocate
  // the break points where straight-line code is patched with a call
  // instruction.
  INLINE(Address call_address());
  INLINE(void set_call_address(Address target));
  INLINE(Object* call_object());
  INLINE(Object** call_object_address());
  INLINE(void set_call_object(Object* target));

  // Patch the code with some other code.
  void patch_code(byte* instructions, int instruction_count);

  // Patch the code with a call.
  void patch_code_with_call(Address target, int guard_bytes);
  INLINE(bool is_call_instruction());

#ifdef ENABLE_DISASSEMBLER
  // Printing
  static const char* RelocModeName(Mode rmode);
  void Print();
#endif  // ENABLE_DISASSEMBLER
#ifdef DEBUG
  // Debugging
  void Verify();
#endif

  static const int kCodeTargetMask = (1 << (LAST_CODE_ENUM + 1)) - 1;
  static const int kPositionMask = 1 << POSITION | 1 << STATEMENT_POSITION;
  static const int kDebugMask = kPositionMask | 1 << COMMENT;
  static const int kApplyMask;  // Modes affected by apply. Depends on arch.

 private:
  // On ARM, note that pc_ is the address of the constant pool entry
  // to be relocated and not the address of the instruction
  // referencing the constant pool entry (except when rmode_ ==
  // comment).
  byte* pc_;
  Mode rmode_;
  intptr_t data_;
  friend class RelocIterator;
};


// RelocInfoWriter serializes a stream of relocation info. It writes towards
// lower addresses.
class RelocInfoWriter BASE_EMBEDDED {
 public:
  RelocInfoWriter() : pos_(NULL), last_pc_(NULL), last_data_(0) {}
  RelocInfoWriter(byte* pos, byte* pc) : pos_(pos), last_pc_(pc),
                                         last_data_(0) {}

  byte* pos() const { return pos_; }
  byte* last_pc() const { return last_pc_; }

  void Write(const RelocInfo* rinfo);

  // Update the state of the stream after reloc info buffer
  // and/or code is moved while the stream is active.
  void Reposition(byte* pos, byte* pc) {
    pos_ = pos;
    last_pc_ = pc;
  }

  // Max size (bytes) of a written RelocInfo.
  static const int kMaxSize = 12;

 private:
  inline uint32_t WriteVariableLengthPCJump(uint32_t pc_delta);
  inline void WriteTaggedPC(uint32_t pc_delta, int tag);
  inline void WriteExtraTaggedPC(uint32_t pc_delta, int extra_tag);
  inline void WriteExtraTaggedData(int32_t data_delta, int top_tag);
  inline void WriteTaggedData(int32_t data_delta, int tag);
  inline void WriteExtraTag(int extra_tag, int top_tag);

  byte* pos_;
  byte* last_pc_;
  intptr_t last_data_;
  DISALLOW_COPY_AND_ASSIGN(RelocInfoWriter);
};


// A RelocIterator iterates over relocation information.
// Typical use:
//
//   for (RelocIterator it(code); !it.done(); it.next()) {
//     // do something with it.rinfo() here
//   }
//
// A mask can be specified to skip unwanted modes.
class RelocIterator: public Malloced {
 public:
  // Create a new iterator positioned at
  // the beginning of the reloc info.
  // Relocation information with mode k is included in the
  // iteration iff bit k of mode_mask is set.
  explicit RelocIterator(Code* code, int mode_mask = -1);
  explicit RelocIterator(const CodeDesc& desc, int mode_mask = -1);

  // Iteration
  bool done() const  { return done_; }
  void next();

  // Return pointer valid until next next().
  RelocInfo* rinfo() {
    ASSERT(!done());
    return &rinfo_;
  }

 private:
  // Advance* moves the position before/after reading.
  // *Read* reads from current byte(s) into rinfo_.
  // *Get* just reads and returns info on current byte.
  void Advance(int bytes = 1) { pos_ -= bytes; }
  int AdvanceGetTag();
  int GetExtraTag();
  int GetTopTag();
  void ReadTaggedPC();
  void AdvanceReadPC();
  void AdvanceReadData();
  void AdvanceReadVariableLengthPCJump();
  int GetPositionTypeTag();
  void ReadTaggedData();

  static RelocInfo::Mode DebugInfoModeFromTag(int tag);

  // If the given mode is wanted, set it in rinfo_ and return true.
  // Else return false. Used for efficiently skipping unwanted modes.
  bool SetMode(RelocInfo::Mode mode) {
    return (mode_mask_ & 1 << mode) ? (rinfo_.rmode_ = mode, true) : false;
  }

  byte* pos_;
  byte* end_;
  RelocInfo rinfo_;
  bool done_;
  int mode_mask_;
  DISALLOW_COPY_AND_ASSIGN(RelocIterator);
};


//------------------------------------------------------------------------------
// External function

//----------------------------------------------------------------------------
class IC_Utility;
class Debug_Address;
class SCTableReference;

// An ExternalReference represents a C++ address called from the generated
// code. All references to C++ functions and must be encapsulated in an
// ExternalReference instance. This is done in order to track the origin of
// all external references in the code.
class ExternalReference BASE_EMBEDDED {
 public:
  explicit ExternalReference(Builtins::CFunctionId id);

  explicit ExternalReference(Builtins::Name name);

  explicit ExternalReference(Runtime::FunctionId id);

  explicit ExternalReference(Runtime::Function* f);

  explicit ExternalReference(const IC_Utility& ic_utility);

  explicit ExternalReference(const Debug_Address& debug_address);

  explicit ExternalReference(StatsCounter* counter);

  explicit ExternalReference(Top::AddressId id);

  explicit ExternalReference(const SCTableReference& table_ref);

  // One-of-a-kind references. These references are not part of a general
  // pattern. This means that they have to be added to the
  // ExternalReferenceTable in serialize.cc manually.

  static ExternalReference builtin_passed_function();

  // Static variable Factory::the_hole_value.location()
  static ExternalReference the_hole_value_location();

  // Static variable StackGuard::address_of_limit()
  static ExternalReference address_of_stack_guard_limit();

  // Function Debug::Break()
  static ExternalReference debug_break();

  // Static variable Heap::NewSpaceStart()
  static ExternalReference new_space_start();

  // Used for fast allocation in generated code.
  static ExternalReference new_space_allocation_top_address();
  static ExternalReference new_space_allocation_limit_address();

  // Used to check if single stepping is enabled in generated code.
  static ExternalReference debug_step_in_fp_address();

  Address address() const {return address_;}

 private:
  explicit ExternalReference(void* address)
    : address_(reinterpret_cast<Address>(address)) {}

  Address address_;
};


// -----------------------------------------------------------------------------
// Utility functions

// Move these into inline file?

static inline bool is_intn(int x, int n)  {
  return -(1 << (n-1)) <= x && x < (1 << (n-1));
}

static inline bool is_int24(int x)  { return is_intn(x, 24); }
static inline bool is_int8(int x)  { return is_intn(x, 8); }

static inline bool is_uintn(int x, int n) {
  return (x & -(1 << n)) == 0;
}

static inline bool is_uint3(int x)  { return is_uintn(x, 3); }
static inline bool is_uint4(int x)  { return is_uintn(x, 4); }
static inline bool is_uint5(int x)  { return is_uintn(x, 5); }
static inline bool is_uint8(int x)  { return is_uintn(x, 8); }
static inline bool is_uint12(int x)  { return is_uintn(x, 12); }
static inline bool is_uint16(int x)  { return is_uintn(x, 16); }
static inline bool is_uint24(int x)  { return is_uintn(x, 24); }

} }  // namespace v8::internal

#endif  // V8_ASSEMBLER_H_