/*

 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

#ifndef SHARE_VM_PRIMS_METHODCOMPARATOR_HPP

#define SHARE_VM_PRIMS_METHODCOMPARATOR_HPP

#include "interpreter/bytecodeStream.hpp"

#include "oops/constantPoolOop.hpp"

#include "oops/methodOop.hpp"

class BciMap;

// methodComparator provides an interface for determining if methods of

// different versions of classes are equivalent or switchable

class MethodComparator {

 private:

  static BytecodeStream *_s_old, *_s_new;

  static constantPoolOop _old_cp, _new_cp;

  static BciMap *_bci_map;

  static bool _switchable_test;

  static GrowableArray<int> *_fwd_jmps;

  static bool args_same(Bytecodes::Code c_old, Bytecodes::Code c_new);

  static bool pool_constants_same(int cpi_old, int cpi_new);

  static int check_stack_and_locals_size(methodOop old_method, methodOop new_method);

 public:

  // Check if the new method is equivalent to the old one modulo constant pool (EMCP).

  // Intuitive definition: two versions of the same method are EMCP, if they don't differ

  // on the source code level. Practically, we check whether the only difference between

  // method versions is some constantpool indices embedded into the bytecodes, and whether

  // these indices eventually point to the same constants for both method versions.

  static bool methods_EMCP(methodOop old_method, methodOop new_method);

  static bool methods_switchable(methodOop old_method, methodOop new_method, BciMap &bci_map);

};

// ByteCode Index Map. For two versions of the same method, where the new version may contain

// fragments not found in the old version, provides a mapping from an index of a bytecode in

// the old method to the index of the same bytecode in the new method.

class BciMap {

 private:

  int *_old_bci, *_new_st_bci, *_new_end_bci;

  int _cur_size, _cur_pos;

  int _pos;

 public:

  BciMap() {

    _cur_size = 50;

    _old_bci = (int*) malloc(sizeof(int) * _cur_size);

    _new_st_bci = (int*) malloc(sizeof(int) * _cur_size);

    _new_end_bci = (int*) malloc(sizeof(int) * _cur_size);

    _cur_pos = 0;

  }

  ~BciMap() {

    free(_old_bci);

    free(_new_st_bci);

    free(_new_end_bci);

  }

  // Store the position of an added fragment, e.g.

  //

  //                              |<- old_bci

  // -----------------------------------------

  // Old method   |invokevirtual 5|aload 1|...

  // -----------------------------------------

  //

  //                                 |<- new_st_bci          |<- new_end_bci

  // --------------------------------------------------------------------

  // New method       |invokevirual 5|aload 2|invokevirtual 6|aload 1|...

  // --------------------------------------------------------------------

  //                                 ^^^^^^^^^^^^^^^^^^^^^^^^

  //                                    Added fragment

  void store_fragment_location(int old_bci, int new_st_bci, int new_end_bci) {

    if (_cur_pos == _cur_size) {

      _cur_size += 10;

      _old_bci = (int*) realloc(_old_bci, sizeof(int) * _cur_size);

      _new_st_bci = (int*) realloc(_new_st_bci, sizeof(int) * _cur_size);

      _new_end_bci = (int*) realloc(_new_end_bci, sizeof(int) * _cur_size);

    }

    _old_bci[_cur_pos] = old_bci;

    _new_st_bci[_cur_pos] = new_st_bci;

    _new_end_bci[_cur_pos] = new_end_bci;

    _cur_pos++;

  }

  int new_bci_for_old(int old_bci) {

    if (_cur_pos == 0 || old_bci < _old_bci[0]) return old_bci;

    _pos = 1;

    while (_pos < _cur_pos && old_bci >= _old_bci[_pos])

      _pos++;

    return _new_end_bci[_pos-1] + (old_bci - _old_bci[_pos-1]);

  }

  // Test if two indexes - one in the old method and another in the new one - correspond

  // to the same bytecode

  bool old_and_new_locations_same(int old_dest_bci, int new_dest_bci) {

    if (new_bci_for_old(old_dest_bci) == new_dest_bci)

      return true;

    else if (_old_bci[_pos-1] == old_dest_bci)

      return (new_dest_bci == _new_st_bci[_pos-1]);

    else return false;

  }

};

#endif // SHARE_VM_PRIMS_METHODCOMPARATOR_HPP