1 /*
2 * Copyright (c) 2000, 2010, 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/constantPoolOop.hpp"
30 #include "oops/methodOop.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 constantPoolOop _old_cp, _new_cp;
41 static BciMap *_bci_map;
42 static bool _switchable_test;
43 static GrowableArray<int> *_fwd_jmps;
44
45 static bool args_same(Bytecodes::Code c_old, Bytecodes::Code c_new);
46 static int check_stack_and_locals_size(methodOop old_method, methodOop new_method);
47
48 public:
49 // Check if the new method is equivalent to the old one modulo constant pool (EMCP).
50 // Intuitive definition: two versions of the same method are EMCP, if they don't differ
51 // on the source code level. Practically, we check whether the only difference between
52 // method versions is some constantpool indices embedded into the bytecodes, and whether
53 // these indices eventually point to the same constants for both method versions.
54 static bool methods_EMCP(methodOop old_method, methodOop new_method);
55
56 static bool methods_switchable(methodOop old_method, methodOop new_method, BciMap &bci_map);
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 // Store the position of an added fragment, e.g.
86 //
87 // |<- old_bci
88 // -----------------------------------------
89 // Old method |invokevirtual 5|aload 1|...
90 // -----------------------------------------
91 //
92 // |<- new_st_bci |<- new_end_bci
93 // --------------------------------------------------------------------
94 // New method |invokevirual 5|aload 2|invokevirtual 6|aload 1|...
95 // --------------------------------------------------------------------
96 // ^^^^^^^^^^^^^^^^^^^^^^^^
97 // Added fragment
98
99 void store_fragment_location(int old_bci, int new_st_bci, int new_end_bci) {
100 if (_cur_pos == _cur_size) {
101 _cur_size += 10;
102 _old_bci = (int*) realloc(_old_bci, sizeof(int) * _cur_size);
103 _new_st_bci = (int*) realloc(_new_st_bci, sizeof(int) * _cur_size);
104 _new_end_bci = (int*) realloc(_new_end_bci, sizeof(int) * _cur_size);
105 }
106 _old_bci[_cur_pos] = old_bci;
107 _new_st_bci[_cur_pos] = new_st_bci;
108 _new_end_bci[_cur_pos] = new_end_bci;
109 _cur_pos++;
110 }
111
112 int new_bci_for_old(int old_bci) {
113 if (_cur_pos == 0 || old_bci < _old_bci[0]) return old_bci;
114 _pos = 1;
115 while (_pos < _cur_pos && old_bci >= _old_bci[_pos])
116 _pos++;
117 return _new_end_bci[_pos-1] + (old_bci - _old_bci[_pos-1]);
118 }
119
120 // Test if two indexes - one in the old method and another in the new one - correspond
121 // to the same bytecode
122 bool old_and_new_locations_same(int old_dest_bci, int new_dest_bci) {
123 if (new_bci_for_old(old_dest_bci) == new_dest_bci)
124 return true;
125 else if (_old_bci[_pos-1] == old_dest_bci)
126 return (new_dest_bci == _new_st_bci[_pos-1]);
127 else return false;
128 }
129 };
130
131 #endif // SHARE_VM_PRIMS_METHODCOMPARATOR_HPP