assembler.h.svn-base

Google浏览器V8内核代码

// Copyright (c) 1994-2006 Sun Microsystems Inc.
// 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.
//
// - Redistribution in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// - Neither the name of Sun Microsystems or the names of 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 OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// The original source code covered by the above license above has been
// modified significantly by Google Inc.
// Copyright 2006-2008 the V8 project authors. All rights reserved.

#ifndef V8_ASSEMBLER_H_
#define V8_ASSEMBLER_H_

#include "runtime.h"
#include "top.h"
#include "zone-inl.h"

namespace v8 { namespace internal {


// -----------------------------------------------------------------------------
// Labels represent pc locations; they are typically jump or call targets.
// After declaration, a label can be freely used to denote known or (yet)
// unknown pc location. Assembler::bind() is used to bind a label to the
// current pc. A label can be bound only once.

class Label : public ZoneObject {  // ShadowLables are dynamically allocated.
 public:
  INLINE(Label())                 { Unuse(); }
  INLINE(~Label())                { ASSERT(!is_linked()); }

  INLINE(void Unuse())            { pos_ = 0; }

  INLINE(bool is_bound()  const)  { return pos_ <  0; }
  INLINE(bool is_unused() const)  { return pos_ == 0; }
  INLINE(bool is_linked() const)  { return pos_ >  0; }

  // Returns the position of bound or linked labels. Cannot be used
  // for unused labels.
  int pos() const;

 private:
  // pos_ encodes both the binding state (via its sign)
  // and the binding position (via its value) of a label.
  //
  // pos_ <  0  bound label, pos() returns the jump target position
  // pos_ == 0  unused label
  // pos_ >  0  linked label, pos() returns the last reference position
  int pos_;

  void bind_to(int pos)  {
    pos_ = -pos - 1;
    ASSERT(is_bound());
  }
  void link_to(int pos)  {
    pos_ =  pos + 1;
    ASSERT(is_linked());
  }

  friend class Assembler;
  friend class Displacement;
  friend class LabelShadow;
};


// A LabelShadow is a label that temporarily shadows another label. It
// is used to catch linking and binding of labels in certain scopes,
// e.g. try blocks. LabelShadows are themselves labels which can be
// used (only) after they are not shadowing anymore.
class LabelShadow: public Label {
 public:
  explicit LabelShadow(Label* shadowed) {
    ASSERT(shadowed != NULL);
    shadowed_ = shadowed;
    shadowed_pos_ = shadowed->pos_;
    shadowed->Unuse();
#ifdef DEBUG
    is_shadowing_ = true;
#endif
  }

  ~LabelShadow() {
    ASSERT(!is_shadowing_);
  }

  void StopShadowing() {
    ASSERT(is_shadowing_ && is_unused());
    pos_ = shadowed_->pos_;
    shadowed_->pos_ = shadowed_pos_;
#ifdef DEBUG
    is_shadowing_ = false;
#endif
  }

  Label* shadowed() const { return shadowed_; }

 private:
  Label* shadowed_;
  int shadowed_pos_;
#ifdef DEBUG
  bool is_shadowing_;
#endif
};


// -----------------------------------------------------------------------------
// Relocation information


// Relocation information consists of the address (pc) of the datum
// to which the relocation information applies, the relocation mode
// (rmode), and an optional data field. The relocation mode may be
// "descriptive" and not indicate a need for relocation, but simply
// describe a property of the datum. Such rmodes are useful for GC
// and nice disassembly output.

class RelocInfo BASE_EMBEDDED {
 public:
  // The constant kNoPosition is used with the collecting of source positions
  // in the relocation information. Two types of source positions are collected
  // "position" (RelocMode position) and "statement position" (RelocMode
  // statement_position). The "position" is collected at places in the source
  // code which are of interest when making stack traces to pin-point the source
  // location of a stack frame as close as possible. The "statement position" is
  // collected at the beginning at each statement, and is used to indicate
  // possible break locations. kNoPosition is used to indicate an
  // invalid/uninitialized position value.
  static const int kNoPosition = -1;

  enum Mode {
    // Please note the order is important (see IsCodeTarget, IsGCRelocMode).
    CONSTRUCT_CALL,  // code target that is a call to a JavaScript constructor.
    CODE_TARGET_CONTEXT,  // code target used for contextual loads.
    CODE_TARGET,         // code target which is not any of the above.
    EMBEDDED_OBJECT,
    EMBEDDED_STRING,

    // Everything after runtime_entry (inclusive) is not GC'ed.
    RUNTIME_ENTRY,
    JS_RETURN,  // Marks start of the ExitJSFrame code.
    COMMENT,
    POSITION,  // See comment for kNoPosition above.
    STATEMENT_POSITION,  // See comment for kNoPosition above.
    EXTERNAL_REFERENCE,  // The address of an external C++ function.
    INTERNAL_REFERENCE,  // An address inside the same function.

    // add more as needed
    // Pseudo-types
    NUMBER_OF_MODES,  // must be no greater than 14 - see RelocInfoWriter
    NONE,  // never recorded
    LAST_CODE_ENUM = CODE_TARGET,
    LAST_GCED_ENUM = EMBEDDED_STRING
  };


  RelocInfo() {}
  RelocInfo(byte* pc, Mode rmode, intptr_t data)
      : pc_(pc), rmode_(rmode), data_(data) {
  }

  static inline bool IsConstructCall(Mode mode) {
    return mode == CONSTRUCT_CALL;
  }
  static inline bool IsCodeTarget(Mode mode) {
    return mode <= LAST_CODE_ENUM;
  }
  // Is the relocation mode affected by GC?
  static inline bool IsGCRelocMode(Mode mode) {
    return mode <= LAST_GCED_ENUM;
  }
  static inline bool IsJSReturn(Mode mode) {
    return mode == JS_RETURN;
  }
  static inline bool IsComment(Mode mode) {
    return mode == COMMENT;
  }
  static inline bool IsPosition(Mode mode) {
    return mode == POSITION || mode == STATEMENT_POSITION;
  }
  static inline bool IsStatementPosition(Mode mode) {
    return mode == STATEMENT_POSITION;
  }
  static inline bool IsExternalReference(Mode mode) {
    return mode == EXTERNAL_REFERENCE;
  }
  static inline bool IsInternalReference(Mode mode) {
    return mode == INTERNAL_REFERENCE;
  }
  static inline int ModeMask(Mode mode) { return 1 << mode; }

  // Accessors
  byte* pc() const  { return pc_; }
  void set_pc(byte* pc) { pc_ = pc; }
  Mode rmode() const {  return rmode_; }
  intptr_t data() const  { return data_; }

  // Apply a relocation by delta bytes
  INLINE(void apply(int delta));

  // Read/modify the code target in the branch/call instruction this relocation
  // applies to; can only be called if IsCodeTarget(rmode_)
  INLINE(Address target_address());
  INLINE(void set_target_address(Address target));
  INLINE(Object* target_object());
  INLINE(Object** target_object_address());
  INLINE(void set_target_object(Object* target));

  // Read/modify the reference in the instruction this relocation
  // applies to; can only be called if rmode_ is external_reference
  INLINE(Address* target_reference_address());