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
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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// methodComparator provides an interface for determining if methods of
33// different versions of classes are equivalent or switchable
34
35class MethodComparator {
36 private:
37  static BytecodeStream *_s_old, *_s_new;
38  static ConstantPool* _old_cp;
39  static ConstantPool* _new_cp;
40
41  static bool args_same(Bytecodes::Code c_old, Bytecodes::Code c_new);
42  static bool pool_constants_same(int cpi_old, int cpi_new);
43  static int check_stack_and_locals_size(Method* old_method, Method* new_method);
44
45 public:
46  // Check if the new method is equivalent to the old one modulo constant pool (EMCP).
47  // Intuitive definition: two versions of the same method are EMCP, if they don't differ
48  // on the source code level. Practically, we check whether the only difference between
49  // method versions is some constantpool indices embedded into the bytecodes, and whether
50  // these indices eventually point to the same constants for both method versions.
51  static bool methods_EMCP(Method* old_method, Method* new_method);
52
53};
54
55#endif // SHARE_VM_PRIMS_METHODCOMPARATOR_HPP
56