/*

 * Copyright 1997-2008 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

// A Location describes a concrete machine variable location

// (such as integer or floating point register or a stack-held

// variable). Used when generating debug-information for nmethods.

//

// Encoding:

//

// bits (use low bits for best compression):

//  Type:   [3..0]

//  Where:  [4]

//  Offset: [31..5]

class Location VALUE_OBJ_CLASS_SPEC {

  friend class VMStructs;

 public:

  enum Where {

    on_stack,

    in_register

  };

  enum Type {

    invalid,                    // Invalid location

    normal,                     // Ints, floats, double halves

    oop,                        // Oop (please GC me!)

    int_in_long,                // Integer held in long register

    lng,                        // Long held in one register

    float_in_dbl,               // Float held in double register

    dbl,                        // Double held in one register

    addr,                       // JSR return address

    narrowoop                   // Narrow Oop (please GC me!)

  };

 private:

  enum {

    TYPE_MASK    = (juint) 0x0F,

    TYPE_SHIFT   = 0,

    WHERE_MASK   = (juint) 0x10,

    WHERE_SHIFT  = 4,

    OFFSET_MASK  = (juint) 0xFFFFFFE0,

    OFFSET_SHIFT = 5

  };

  juint _value;

  // Create a bit-packed Location

  Location(Where where_, Type type_, unsigned offset_) {

    set(where_, type_, offset_);

    assert( where () == where_ , "" );

    assert( type  () == type_  , "" );

    assert( offset() == offset_, "" );

  }

  inline void set(Where where_, Type type_, unsigned offset_) {

    _value = (juint) ((where_  << WHERE_SHIFT) |

                      (type_   << TYPE_SHIFT)  |

                      ((offset_ << OFFSET_SHIFT) & OFFSET_MASK));

  }

 public:

  // Stack location Factory.  Offset is 4-byte aligned; remove low bits

  static Location new_stk_loc( Type t, int offset ) { return Location(on_stack,t,offset>>LogBytesPerInt); }

  // Register location Factory

  static Location new_reg_loc( Type t, VMReg reg ) { return Location(in_register, t, reg->value()); }

  // Default constructor

  Location() { set(on_stack,invalid,0); }

  // Bit field accessors

  Where where()  const { return (Where)       ((_value & WHERE_MASK)  >> WHERE_SHIFT);}

  Type  type()   const { return (Type)        ((_value & TYPE_MASK)   >> TYPE_SHIFT); }

  unsigned offset() const { return (unsigned) ((_value & OFFSET_MASK) >> OFFSET_SHIFT); }

  // Accessors

  bool is_register() const    { return where() == in_register; }

  bool is_stack() const       { return where() == on_stack;    }

  int stack_offset() const    { assert(where() == on_stack,    "wrong Where"); return offset()<<LogBytesPerInt; }

  int register_number() const { assert(where() == in_register, "wrong Where"); return offset()   ; }

  VMReg reg() const { assert(where() == in_register, "wrong Where"); return VMRegImpl::as_VMReg(offset())   ; }

  // Printing

  void print_on(outputStream* st) const;

  // Serialization of debugging information

  Location(DebugInfoReadStream* stream);

  void write_on(DebugInfoWriteStream* stream);

  // check

  static bool legal_offset_in_bytes(int offset_in_bytes);

};