1/*
2 * Copyright (c) 2004, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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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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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23 */
24
25#ifndef SHARE_PRIMS_JNIFASTGETFIELD_HPP
26#define SHARE_PRIMS_JNIFASTGETFIELD_HPP
27
28#include "memory/allocation.hpp"
29#include "prims/jvm_misc.hpp"
30
31// Basic logic of a fast version of jni_Get<Primitive>Field:
32//
33// (See safepoint.hpp for a description of _safepoint_counter)
34//
35// load _safepoint_counter into old_counter
36// IF old_counter is odd THEN
37// a safepoint is going on, return jni_GetXXXField
38// ELSE
39// load the primitive field value into result (speculatively)
40// load _safepoint_counter into new_counter
41// IF (old_counter == new_counter) THEN
42// no safepoint happened during the field access, return result
43// ELSE
44// a safepoint might have happened in-between, return jni_GetXXXField()
45// ENDIF
46// ENDIF
47//
48// LoadLoad membars to maintain the load order may be necessary
49// for some platforms.
50//
51// The fast versions don't check for pending suspension request.
52// This is fine since it's totally read-only and doesn't create new race.
53//
54// There is a hypothetical safepoint counter wraparound. But it's not
55// a practical concern.
56
57class JNI_FastGetField : AllStatic {
58 private:
59 enum { LIST_CAPACITY = 40 }; // a conservative number for the number of
60 // speculative loads on all the platforms
61 static address speculative_load_pclist [];
62 static address slowcase_entry_pclist [];
63 static int count;
64
65 static address generate_fast_get_int_field0(BasicType type);
66 static address generate_fast_get_float_field0(BasicType type);
67
68 public:
69#if defined(_WINDOWS) && !defined(_WIN64)
70 static GetBooleanField_t jni_fast_GetBooleanField_fp;
71 static GetByteField_t jni_fast_GetByteField_fp;
72 static GetCharField_t jni_fast_GetCharField_fp;
73 static GetShortField_t jni_fast_GetShortField_fp;
74 static GetIntField_t jni_fast_GetIntField_fp;
75 static GetLongField_t jni_fast_GetLongField_fp;
76 static GetFloatField_t jni_fast_GetFloatField_fp;
77 static GetDoubleField_t jni_fast_GetDoubleField_fp;
78#endif
79
80 static address generate_fast_get_boolean_field();
81 static address generate_fast_get_byte_field();
82 static address generate_fast_get_char_field();
83 static address generate_fast_get_short_field();
84 static address generate_fast_get_int_field();
85 static address generate_fast_get_long_field();
86 static address generate_fast_get_float_field();
87 static address generate_fast_get_double_field();
88
89 // If pc is in speculative_load_pclist, return the corresponding
90 // slow case entry pc. Otherwise, return -1.
91 // This is used by signal/exception handler to handle such case:
92 // After an even safepoint counter is loaded and a fast field access
93 // is about to begin, a GC kicks in and shrinks the heap. Then the
94 // field access may fault. The signal/exception handler needs to
95 // return to the slow case.
96 //
97 // The GC may decide to temporarily stuff some bad values into handles,
98 // for example, for debugging purpose, in which case we need the mapping also.
99 static address find_slowcase_pc(address pc);
100};
101
102#endif // SHARE_PRIMS_JNIFASTGETFIELD_HPP
103