jniFastGetField.hpp revision 1472:c18cbe5936b8 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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).
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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.
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24
25// Basic logic of a fast version of jni_Get<Primitive>Field:
26//
27// (See safepoint.hpp for a description of _safepoint_counter)
28//
29// load _safepoint_counter into old_counter
30// IF old_counter is odd THEN
31//   a safepoint is going on, return jni_GetXXXField
32// ELSE
33//   load the primitive field value into result (speculatively)
34//   load _safepoint_counter into new_counter
35//   IF (old_counter == new_counter) THEN
36//     no safepoint happened during the field access, return result
37//   ELSE
38//     a safepoint might have happened in-between, return jni_GetXXXField()
39//   ENDIF
40// ENDIF
41//
42// LoadLoad membars to maintain the load order may be necessary
43// for some platforms.
44//
45// The fast versions don't check for pending suspension request.
46// This is fine since it's totally read-only and doesn't create new race.
47//
48// There is a hypothetical safepoint counter wraparound. But it's not
49// a practical concern.
50
51class JNI_FastGetField : AllStatic {
52 private:
53  enum { LIST_CAPACITY = 40 };      // a conservative number for the number of
54                                    // speculative loads on all the platforms
55  static address speculative_load_pclist [];
56  static address slowcase_entry_pclist   [];
57  static int     count;
58
59  static address generate_fast_get_int_field0(BasicType type);
60  static address generate_fast_get_float_field0(BasicType type);
61
62 public:
63#if defined(_WINDOWS) && !defined(_WIN64)
64  static GetBooleanField_t jni_fast_GetBooleanField_fp;
65  static GetByteField_t    jni_fast_GetByteField_fp;
66  static GetCharField_t    jni_fast_GetCharField_fp;
67  static GetShortField_t   jni_fast_GetShortField_fp;
68  static GetIntField_t     jni_fast_GetIntField_fp;
69  static GetLongField_t    jni_fast_GetLongField_fp;
70  static GetFloatField_t   jni_fast_GetFloatField_fp;
71  static GetDoubleField_t  jni_fast_GetDoubleField_fp;
72#endif
73
74  static address generate_fast_get_boolean_field();
75  static address generate_fast_get_byte_field();
76  static address generate_fast_get_char_field();
77  static address generate_fast_get_short_field();
78  static address generate_fast_get_int_field();
79  static address generate_fast_get_long_field();
80  static address generate_fast_get_float_field();
81  static address generate_fast_get_double_field();
82
83  // If pc is in speculative_load_pclist, return the corresponding
84  // slow case entry pc. Otherwise, return -1.
85  // This is used by signal/exception handler to handle such case:
86  // After an even safepoint counter is loaded and a fast field access
87  // is about to begin, a GC kicks in and shrinks the heap. Then the
88  // field access may fault. The signal/exception handler needs to
89  // return to the slow case.
90  //
91  // The GC may decide to temporarily stuff some bad values into handles,
92  // for example, for debugging purpose, in which case we need the mapping also.
93  static address find_slowcase_pc(address pc);
94};
95