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comparison: src/share/vm/runtime/jfieldIDWorkaround.hpp
src/share/vm/runtime/jfieldIDWorkaround.hpp
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| 1 /* | |
| 2 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 20 * or visit www.oracle.com if you need additional information or have any | |
| 21 * questions. | |
| 22 * | |
| 23 */ | |
| 24 | |
| 25 #ifndef SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP | |
| 26 #define SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP | |
| 27 | |
| 28 class jfieldIDWorkaround: AllStatic { | |
| 29 // This workaround is because JVMTI doesn't have distinct entry points | |
| 30 // for methods that use static jfieldIDs and instance jfieldIDs. | |
| 31 // The workaround is to steal a low-order bit: | |
| 32 // a 1 means the jfieldID is an instance jfieldID, | |
| 33 // and the rest of the word is the offset of the field. | |
| 34 // a 0 means the jfieldID is a static jfieldID, | |
| 35 // and the rest of the word is the JNIid*. | |
| 36 // | |
| 37 // Another low-order bit is used to mark if an instance field | |
| 38 // is accompanied by an indication of which class it applies to. | |
| 39 // | |
| 40 // Bit-format of a jfieldID (most significant first): | |
| 41 // address:30 instance=0:1 checked=0:1 | |
| 42 // offset:30 instance=1:1 checked=0:1 | |
| 43 // klass:23 offset:7 instance=1:1 checked=1:1 | |
| 44 // | |
| 45 // If the offset does not fit in 7 bits, or if the fieldID is | |
| 46 // not checked, then the checked bit is zero and the rest of | |
| 47 // the word (30 bits) contains only the offset. | |
| 48 // | |
| 49 private: | |
| 50 enum { | |
| 51 checked_bits = 1, | |
| 52 instance_bits = 1, | |
| 53 address_bits = BitsPerWord - checked_bits - instance_bits, | |
| 54 | |
| 55 large_offset_bits = address_bits, // unioned with address | |
| 56 small_offset_bits = 7, | |
| 57 klass_bits = address_bits - small_offset_bits, | |
| 58 | |
| 59 checked_shift = 0, | |
| 60 instance_shift = checked_shift + checked_bits, | |
| 61 address_shift = instance_shift + instance_bits, | |
| 62 | |
| 63 offset_shift = address_shift, // unioned with address | |
| 64 klass_shift = offset_shift + small_offset_bits, | |
| 65 | |
| 66 checked_mask_in_place = right_n_bits(checked_bits) << checked_shift, | |
| 67 instance_mask_in_place = right_n_bits(instance_bits) << instance_shift, | |
| 68 #ifndef _WIN64 | |
| 69 large_offset_mask = right_n_bits(large_offset_bits), | |
| 70 small_offset_mask = right_n_bits(small_offset_bits), | |
| 71 klass_mask = right_n_bits(klass_bits) | |
| 72 #endif | |
| 73 }; | |
| 74 | |
| 75 #ifdef _WIN64 | |
| 76 // These values are too big for Win64 | |
| 77 const static uintptr_t large_offset_mask = right_n_bits(large_offset_bits); | |
| 78 const static uintptr_t small_offset_mask = right_n_bits(small_offset_bits); | |
| 79 const static uintptr_t klass_mask = right_n_bits(klass_bits); | |
| 80 #endif | |
| 81 | |
| 82 // helper routines: | |
| 83 static bool is_checked_jfieldID(jfieldID id) { | |
| 84 uintptr_t as_uint = (uintptr_t) id; | |
| 85 return ((as_uint & checked_mask_in_place) != 0); | |
| 86 } | |
| 87 static intptr_t raw_instance_offset(jfieldID id) { | |
| 88 uintptr_t result = (uintptr_t) id >> address_shift; | |
| 89 if (VerifyJNIFields && is_checked_jfieldID(id)) { | |
| 90 result &= small_offset_mask; // cut off the hash bits | |
| 91 } | |
| 92 return (intptr_t)result; | |
| 93 } | |
| 94 static intptr_t encode_klass_hash(Klass* k, intptr_t offset); | |
| 95 static bool klass_hash_ok(Klass* k, jfieldID id); | |
| 96 static void verify_instance_jfieldID(Klass* k, jfieldID id); | |
| 97 | |
| 98 public: | |
| 99 static bool is_valid_jfieldID(Klass* k, jfieldID id); | |
| 100 | |
| 101 static bool is_instance_jfieldID(Klass* k, jfieldID id) { | |
| 102 uintptr_t as_uint = (uintptr_t) id; | |
| 103 return ((as_uint & instance_mask_in_place) != 0); | |
| 104 } | |
| 105 static bool is_static_jfieldID(jfieldID id) { | |
| 106 uintptr_t as_uint = (uintptr_t) id; | |
| 107 return ((as_uint & instance_mask_in_place) == 0); | |
| 108 } | |
| 109 | |
| 110 static jfieldID to_instance_jfieldID(Klass* k, int offset) { | |
| 111 intptr_t as_uint = ((offset & large_offset_mask) << offset_shift) | instance_mask_in_place; | |
| 112 if (VerifyJNIFields) { | |
| 113 as_uint |= encode_klass_hash(k, offset); | |
| 114 } | |
| 115 jfieldID result = (jfieldID) as_uint; | |
| 116 #ifndef ASSERT | |
| 117 // always verify in debug mode; switchable in anything else | |
| 118 if (VerifyJNIFields) | |
| 119 #endif // ASSERT | |
| 120 { | |
| 121 verify_instance_jfieldID(k, result); | |
| 122 } | |
| 123 assert(raw_instance_offset(result) == (offset & large_offset_mask), "extract right offset"); | |
| 124 return result; | |
| 125 } | |
| 126 | |
| 127 static intptr_t from_instance_jfieldID(Klass* k, jfieldID id) { | |
| 128 #ifndef ASSERT | |
| 129 // always verify in debug mode; switchable in anything else | |
| 130 if (VerifyJNIFields) | |
| 131 #endif // ASSERT | |
| 132 { | |
| 133 verify_instance_jfieldID(k, id); | |
| 134 } | |
| 135 return raw_instance_offset(id); | |
| 136 } | |
| 137 | |
| 138 static jfieldID to_static_jfieldID(JNIid* id) { | |
| 139 assert(id->is_static_field_id(), "from_JNIid, but not static field id"); | |
| 140 jfieldID result = (jfieldID) id; | |
| 141 assert(from_static_jfieldID(result) == id, "must produce the same static id"); | |
| 142 return result; | |
| 143 } | |
| 144 | |
| 145 static JNIid* from_static_jfieldID(jfieldID id) { | |
| 146 assert(jfieldIDWorkaround::is_static_jfieldID(id), | |
| 147 "to_JNIid, but not static jfieldID"); | |
| 148 JNIid* result = (JNIid*) id; | |
| 149 assert(result->is_static_field_id(), "to_JNIid, but not static field id"); | |
| 150 return result; | |
| 151 } | |
| 152 | |
| 153 static jfieldID to_jfieldID(instanceKlassHandle k, int offset, bool is_static) { | |
| 154 if (is_static) { | |
| 155 JNIid *id = k->jni_id_for(offset); | |
| 156 debug_only(id->set_is_static_field_id()); | |
| 157 return jfieldIDWorkaround::to_static_jfieldID(id); | |
| 158 } else { | |
| 159 return jfieldIDWorkaround::to_instance_jfieldID(k(), offset); | |
| 160 } | |
| 161 } | |
| 162 }; | |
| 163 | |
| 164 #endif // SHARE_VM_RUNTIME_JFIELDIDWORKAROUND_HPP |
