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 /*

  * Copyright (c) 2000, 2012, 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

  * or visit www.oracle.com if you need additional information or have any

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  */

 #ifndef SHARE_VM_PRIMS_METHODCOMPARATOR_HPP

 #define SHARE_VM_PRIMS_METHODCOMPARATOR_HPP

 #include "interpreter/bytecodeStream.hpp"

 #include "oops/constantPool.hpp"

 #include "oops/method.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 ConstantPool* _old_cp;

   static ConstantPool* _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(Method* old_method, Method* 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(Method* old_method, Method* new_method);

   static bool methods_switchable(Method* old_method, Method* 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