methodComparator.hpp revision 1472:c18cbe5936b8 
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24
25class BciMap;
26
27// methodComparator provides an interface for determining if methods of
28// different versions of classes are equivalent or switchable
29
30class MethodComparator {
31 private:
32  static BytecodeStream *_s_old, *_s_new;
33  static constantPoolOop _old_cp, _new_cp;
34  static BciMap *_bci_map;
35  static bool _switchable_test;
36  static GrowableArray<int> *_fwd_jmps;
37
38  static bool args_same(Bytecodes::Code c_old, Bytecodes::Code c_new);
39  static int check_stack_and_locals_size(methodOop old_method, methodOop new_method);
40
41 public:
42  // Check if the new method is equivalent to the old one modulo constant pool (EMCP).
43  // Intuitive definition: two versions of the same method are EMCP, if they don't differ
44  // on the source code level. Practically, we check whether the only difference between
45  // method versions is some constantpool indices embedded into the bytecodes, and whether
46  // these indices eventually point to the same constants for both method versions.
47  static bool methods_EMCP(methodOop old_method, methodOop new_method);
48
49  static bool methods_switchable(methodOop old_method, methodOop new_method, BciMap &bci_map);
50};
51
52
53// ByteCode Index Map. For two versions of the same method, where the new version may contain
54// fragments not found in the old version, provides a mapping from an index of a bytecode in
55// the old method to the index of the same bytecode in the new method.
56
57class BciMap {
58 private:
59  int *_old_bci, *_new_st_bci, *_new_end_bci;
60  int _cur_size, _cur_pos;
61  int _pos;
62
63 public:
64  BciMap() {
65    _cur_size = 50;
66    _old_bci = (int*) malloc(sizeof(int) * _cur_size);
67    _new_st_bci = (int*) malloc(sizeof(int) * _cur_size);
68    _new_end_bci = (int*) malloc(sizeof(int) * _cur_size);
69    _cur_pos = 0;
70  }
71
72  ~BciMap() {
73    free(_old_bci);
74    free(_new_st_bci);
75    free(_new_end_bci);
76  }
77
78  // Store the position of an added fragment, e.g.
79  //
80  //                              |<- old_bci
81  // -----------------------------------------
82  // Old method   |invokevirtual 5|aload 1|...
83  // -----------------------------------------
84  //
85  //                                 |<- new_st_bci          |<- new_end_bci
86  // --------------------------------------------------------------------
87  // New method       |invokevirual 5|aload 2|invokevirtual 6|aload 1|...
88  // --------------------------------------------------------------------
89  //                                 ^^^^^^^^^^^^^^^^^^^^^^^^
90  //                                    Added fragment
91
92  void store_fragment_location(int old_bci, int new_st_bci, int new_end_bci) {
93    if (_cur_pos == _cur_size) {
94      _cur_size += 10;
95      _old_bci = (int*) realloc(_old_bci, sizeof(int) * _cur_size);
96      _new_st_bci = (int*) realloc(_new_st_bci, sizeof(int) * _cur_size);
97      _new_end_bci = (int*) realloc(_new_end_bci, sizeof(int) * _cur_size);
98    }
99    _old_bci[_cur_pos] = old_bci;
100    _new_st_bci[_cur_pos] = new_st_bci;
101    _new_end_bci[_cur_pos] = new_end_bci;
102    _cur_pos++;
103  }
104
105  int new_bci_for_old(int old_bci) {
106    if (_cur_pos == 0 || old_bci < _old_bci[0]) return old_bci;
107    _pos = 1;
108    while (_pos < _cur_pos && old_bci >= _old_bci[_pos])
109      _pos++;
110    return _new_end_bci[_pos-1] + (old_bci - _old_bci[_pos-1]);
111  }
112
113  // Test if two indexes - one in the old method and another in the new one - correspond
114  // to the same bytecode
115  bool old_and_new_locations_same(int old_dest_bci, int new_dest_bci) {
116    if (new_bci_for_old(old_dest_bci) == new_dest_bci)
117      return true;
118    else if (_old_bci[_pos-1] == old_dest_bci)
119      return (new_dest_bci == _new_st_bci[_pos-1]);
120    else return false;
121  }
122};
123