1 /*
   2  * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_PRIMS_METHODCOMPARATOR_HPP
  26 #define SHARE_VM_PRIMS_METHODCOMPARATOR_HPP
  27 
  28 #include "interpreter/bytecodeStream.hpp"
  29 #include "oops/constantPool.hpp"
  30 #include "oops/method.hpp"
  31 
  32 class BciMap;
  33 
  34 // methodComparator provides an interface for determining if methods of
  35 // different versions of classes are equivalent or switchable
  36 
  37 class MethodComparator {
  38  private:
  39   static BytecodeStream *_s_old, *_s_new;
  40   static ConstantPool* _old_cp;
  41   static ConstantPool* _new_cp;
  42   static BciMap *_bci_map;
  43   static GrowableArray<int> *_fwd_jmps;
  44 
  45   static bool args_same(Bytecodes::Code c_old, Bytecodes::Code c_new);
  46   static bool pool_constants_same(int cpi_old, int cpi_new);
  47   static int check_stack_and_locals_size(Method* old_method, Method* new_method);
  48 
  49  public:
  50   // Check if the new method is equivalent to the old one modulo constant pool (EMCP).
  51   // Intuitive definition: two versions of the same method are EMCP, if they don't differ
  52   // on the source code level. Practically, we check whether the only difference between
  53   // method versions is some constantpool indices embedded into the bytecodes, and whether
  54   // these indices eventually point to the same constants for both method versions.
  55   static bool methods_EMCP(Method* old_method, Method* new_method);
  56 
  57 };
  58 
  59 
  60 // ByteCode Index Map. For two versions of the same method, where the new version may contain
  61 // fragments not found in the old version, provides a mapping from an index of a bytecode in
  62 // the old method to the index of the same bytecode in the new method.
  63 
  64 class BciMap {
  65  private:
  66   int *_old_bci, *_new_st_bci, *_new_end_bci;
  67   int _cur_size, _cur_pos;
  68   int _pos;
  69 
  70  public:
  71   BciMap() {
  72     _cur_size = 50;
  73     _old_bci = (int*) malloc(sizeof(int) * _cur_size);
  74     _new_st_bci = (int*) malloc(sizeof(int) * _cur_size);
  75     _new_end_bci = (int*) malloc(sizeof(int) * _cur_size);
  76     _cur_pos = 0;
  77   }
  78 
  79   ~BciMap() {
  80     free(_old_bci);
  81     free(_new_st_bci);
  82     free(_new_end_bci);
  83   }
  84 
  85   int new_bci_for_old(int old_bci) {
  86     if (_cur_pos == 0 || old_bci < _old_bci[0]) return old_bci;
  87     _pos = 1;
  88     while (_pos < _cur_pos && old_bci >= _old_bci[_pos])
  89       _pos++;
  90     return _new_end_bci[_pos-1] + (old_bci - _old_bci[_pos-1]);
  91   }
  92 
  93   // Test if two indexes - one in the old method and another in the new one - correspond
  94   // to the same bytecode
  95   bool old_and_new_locations_same(int old_dest_bci, int new_dest_bci) {
  96     if (new_bci_for_old(old_dest_bci) == new_dest_bci)
  97       return true;
  98     else if (_old_bci[_pos-1] == old_dest_bci)
  99       return (new_dest_bci == _new_st_bci[_pos-1]);
 100     else return false;
 101   }
 102 };
 103 
 104 #endif // SHARE_VM_PRIMS_METHODCOMPARATOR_HPP