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comparison src/share/vm/prims/jniFastGetField.hpp @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2004 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
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
51 class 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 };