methodComparator.hpp revision 1879:f95d63e2154a 
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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
32class BciMap;
33
34// methodComparator provides an interface for determining if methods of
35// different versions of classes are equivalent or switchable
36
37class 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 bool pool_constants_same(int cpi_old, int cpi_new);
47  static int check_stack_and_locals_size(methodOop old_method, methodOop 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(methodOop old_method, methodOop new_method);
56
57  static bool methods_switchable(methodOop old_method, methodOop new_method, BciMap &bci_map);
58};
59
60
61// ByteCode Index Map. For two versions of the same method, where the new version may contain
62// fragments not found in the old version, provides a mapping from an index of a bytecode in
63// the old method to the index of the same bytecode in the new method.
64
65class BciMap {
66 private:
67  int *_old_bci, *_new_st_bci, *_new_end_bci;
68  int _cur_size, _cur_pos;
69  int _pos;
70
71 public:
72  BciMap() {
73    _cur_size = 50;
74    _old_bci = (int*) malloc(sizeof(int) * _cur_size);
75    _new_st_bci = (int*) malloc(sizeof(int) * _cur_size);
76    _new_end_bci = (int*) malloc(sizeof(int) * _cur_size);
77    _cur_pos = 0;
78  }
79
80  ~BciMap() {
81    free(_old_bci);
82    free(_new_st_bci);
83    free(_new_end_bci);
84  }
85
86  // Store the position of an added fragment, e.g.
87  //
88  //                              |<- old_bci
89  // -----------------------------------------
90  // Old method   |invokevirtual 5|aload 1|...
91  // -----------------------------------------
92  //
93  //                                 |<- new_st_bci          |<- new_end_bci
94  // --------------------------------------------------------------------
95  // New method       |invokevirual 5|aload 2|invokevirtual 6|aload 1|...
96  // --------------------------------------------------------------------
97  //                                 ^^^^^^^^^^^^^^^^^^^^^^^^
98  //                                    Added fragment
99
100  void store_fragment_location(int old_bci, int new_st_bci, int new_end_bci) {
101    if (_cur_pos == _cur_size) {
102      _cur_size += 10;
103      _old_bci = (int*) realloc(_old_bci, sizeof(int) * _cur_size);
104      _new_st_bci = (int*) realloc(_new_st_bci, sizeof(int) * _cur_size);
105      _new_end_bci = (int*) realloc(_new_end_bci, sizeof(int) * _cur_size);
106    }
107    _old_bci[_cur_pos] = old_bci;
108    _new_st_bci[_cur_pos] = new_st_bci;
109    _new_end_bci[_cur_pos] = new_end_bci;
110    _cur_pos++;
111  }
112
113  int new_bci_for_old(int old_bci) {
114    if (_cur_pos == 0 || old_bci < _old_bci[0]) return old_bci;
115    _pos = 1;
116    while (_pos < _cur_pos && old_bci >= _old_bci[_pos])
117      _pos++;
118    return _new_end_bci[_pos-1] + (old_bci - _old_bci[_pos-1]);
119  }
120
121  // Test if two indexes - one in the old method and another in the new one - correspond
122  // to the same bytecode
123  bool old_and_new_locations_same(int old_dest_bci, int new_dest_bci) {
124    if (new_bci_for_old(old_dest_bci) == new_dest_bci)
125      return true;
126    else if (_old_bci[_pos-1] == old_dest_bci)
127      return (new_dest_bci == _new_st_bci[_pos-1]);
128    else return false;
129  }
130};
131
132#endif // SHARE_VM_PRIMS_METHODCOMPARATOR_HPP
133