src/assembler.h

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// 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 {  // LabelShadows 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 represents a label that is temporarily shadowed by another
// label (represented by the original label during shadowing). They are used
// to catch jumps to labels in certain contexts, e.g. try blocks.  After
// shadowing ends, the formerly shadowed label is again represented by the
// original label and the LabelShadow can be used as a label in its own
// right, representing the formerly shadowing label.
class LabelShadow : public Label {
 public:
  explicit LabelShadow(Label* original) {
    ASSERT(original != NULL);
    original_label_ = original;
    original_pos_ = original->pos_;
    original->Unuse();
#ifdef DEBUG
    is_shadowing_ = true;
#endif
  }

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

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

  Label* original_label() const { return original_label_; }

 private:
  // During shadowing, the currently shadowing label.  After shadowing, the
  // label that was shadowed.
  Label* original_label_;

  // During shadowing, the saved state of the original label.
  int original_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());

  // 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();
  static ExternalReference heap_always_allocate_scope_depth();

  // 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_