1 /*
2 * Copyright (c) 1999, 2023, 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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciObject.hpp"
27 #include "ci/ciUtilities.inline.hpp"
28 #include "gc/shared/collectedHeap.inline.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/jniHandles.inline.hpp"
31
32 // ciObject
33 //
34 // This class represents an oop in the HotSpot virtual machine.
35 // Its subclasses are structured in a hierarchy which mirrors
36 // an aggregate of the VM's oop and klass hierarchies (see
37 // oopHierarchy.hpp). Each instance of ciObject holds a handle
38 // to a corresponding oop on the VM side and provides routines
39 // for accessing the information in its oop. By using the ciObject
40 // hierarchy for accessing oops in the VM, the compiler ensures
41 // that it is safe with respect to garbage collection; that is,
42 // GC and compilation can proceed independently without
43 // interference.
44 //
45 // Within the VM, the oop and klass hierarchies are separate.
46 // The compiler interface does not preserve this separation --
47 // the distinction between `Klass*' and `Klass' are not
48 // reflected in the interface and instead the Klass hierarchy
49 // is directly modeled as the subclasses of ciKlass.
50
51 // ------------------------------------------------------------------
52 // ciObject::ciObject
53 ciObject::ciObject(oop o) {
54 ASSERT_IN_VM;
55 if (ciObjectFactory::is_initialized()) {
56 _handle = JNIHandles::make_local(o);
57 } else {
58 Handle obj(Thread::current(), o);
59 _handle = JNIHandles::make_global(obj);
60 }
61 _klass = nullptr;
62 assert(oopDesc::is_oop_or_null(o), "Checking");
63 }
64
65 // ------------------------------------------------------------------
66 // ciObject::ciObject
67 //
68 ciObject::ciObject(Handle h) {
69 ASSERT_IN_VM;
70 if (ciObjectFactory::is_initialized()) {
71 _handle = JNIHandles::make_local(h());
72 } else {
73 _handle = JNIHandles::make_global(h);
74 }
75 _klass = nullptr;
76 assert(oopDesc::is_oop_or_null(h()), "Checking");
77 }
78
79 // ------------------------------------------------------------------
80 // ciObject::ciObject
81 //
82 // Unloaded klass/method variant. `klass' is the klass of the unloaded
83 // klass/method, if that makes sense.
84 ciObject::ciObject(ciKlass* klass) {
85 ASSERT_IN_VM;
86 assert(klass != nullptr, "must supply klass");
87 _handle = nullptr;
88 _klass = klass;
89 }
90
91 // ------------------------------------------------------------------
92 // ciObject::ciObject
93 //
94 // null variant. Used only by ciNullObject.
95 ciObject::ciObject() {
96 ASSERT_IN_VM;
97 _handle = nullptr;
98 _klass = nullptr;
99 }
100
101 // ------------------------------------------------------------------
102 // ciObject::get_oop
103 //
104 // Get the oop of this ciObject.
105 oop ciObject::get_oop() const {
106 return JNIHandles::resolve_non_null(_handle);
107 }
108
109 // ------------------------------------------------------------------
110 // ciObject::klass
111 //
112 // Get the ciKlass of this ciObject.
113 ciKlass* ciObject::klass() {
114 if (_klass == nullptr) {
115 if (_handle == nullptr) {
116 // When both _klass and _handle are null, we are dealing
117 // with the distinguished instance of ciNullObject.
118 // No one should ask it for its klass.
119 assert(is_null_object(), "must be null object");
120 ShouldNotReachHere();
121 return nullptr;
122 }
123
124 GUARDED_VM_ENTRY(
125 oop o = get_oop();
126 _klass = CURRENT_ENV->get_klass(o->klass());
127 );
128 }
129 return _klass;
130 }
131
132 // ------------------------------------------------------------------
133 // ciObject::equals
134 //
135 // Are two ciObjects equal?
136 bool ciObject::equals(ciObject* obj) {
137 return (this == obj);
138 }
139
140 // ------------------------------------------------------------------
141 // ciObject::hash
142 //
143 // A hash value for the convenience of compilers.
144 //
145 // Implementation note: we use the address of the ciObject as the
146 // basis for the hash. Use the _ident field, which is well-behaved.
147 uint ciObject::hash() {
148 return ident() * 31;
149 }
150
151 // ------------------------------------------------------------------
152 // ciObject::constant_encoding
153 //
154 // The address which the compiler should embed into the
155 // generated code to represent this oop. This address
156 // is not the true address of the oop -- it will get patched
157 // during nmethod creation.
158 //
159 //
160 //
161 // Implementation note: we use the handle as the encoding. The
162 // nmethod constructor resolves the handle and patches in the oop.
163 //
164 // This method should be changed to return an generified address
165 // to discourage use of the JNI handle.
166 jobject ciObject::constant_encoding() {
167 assert(is_null_object() || handle() != nullptr, "cannot embed null pointer");
168 return handle();
169 }
170
171 // ------------------------------------------------------------------
172 // ciObject::check_constant_value_cache()
173 //
174 // Cache constant value lookups to ensure that consistent values are observed
175 // during compilation because fields may be (re-)initialized concurrently.
176 ciConstant ciObject::check_constant_value_cache(int off, BasicType bt) {
177 if (_constant_values != nullptr) {
178 for (int i = 0; i < _constant_values->length(); ++i) {
179 ConstantValue cached_val = _constant_values->at(i);
180 if (cached_val.off() == off) {
181 assert(cached_val.value().basic_type() == bt, "unexpected type");
182 return cached_val.value();
183 }
184 }
185 }
186 return ciConstant();
187 }
188
189 // ------------------------------------------------------------------
190 // ciObject::add_to_constant_value_cache()
191 //
192 // Add a constant value to the cache.
193 void ciObject::add_to_constant_value_cache(int off, ciConstant val) {
194 assert(val.is_valid(), "value must be valid");
195 assert(!check_constant_value_cache(off, val.basic_type()).is_valid(), "duplicate");
196 if (_constant_values == nullptr) {
197 Arena* arena = CURRENT_ENV->arena();
198 _constant_values = new (arena) GrowableArray<ConstantValue>(arena, 1, 0, ConstantValue());
199 }
200 _constant_values->append(ConstantValue(off, val));
201 }
202
203 // ------------------------------------------------------------------
204 // ciObject::should_be_constant()
205 bool ciObject::should_be_constant() {
206 if (ScavengeRootsInCode >= 2) return true; // force everybody to be a constant
207 if (is_null_object()) return true;
208
209 ciEnv* env = CURRENT_ENV;
210
211 // We want Strings and Classes to be embeddable by default since
212 // they used to be in the perm world. Not all Strings used to be
213 // embeddable but there's no easy way to distinguish the interned
214 // from the regulars ones so just treat them all that way.
215 if (klass() == env->String_klass() || klass() == env->Class_klass()) {
216 return true;
217 }
218 if (klass()->is_subclass_of(env->MethodHandle_klass()) ||
219 klass()->is_subclass_of(env->CallSite_klass())) {
220 // We want to treat these aggressively.
221 return true;
222 }
223
224 return handle() == nullptr;
225 }
226
227 // ------------------------------------------------------------------
228 // ciObject::print
229 //
230 // Print debugging output about this ciObject.
231 //
232 // Implementation note: dispatch to the virtual print_impl behavior
233 // for this ciObject.
234 void ciObject::print(outputStream* st) {
235 st->print("<%s", type_string());
236 GUARDED_VM_ENTRY(print_impl(st);)
237 st->print(" ident=%d address=" INTPTR_FORMAT ">", ident(), p2i(this));
238 }
239
240 // ------------------------------------------------------------------
241 // ciObject::print_oop
242 //
243 // Print debugging output about the oop this ciObject represents.
244 void ciObject::print_oop(outputStream* st) {
245 if (is_null_object()) {
246 st->print_cr("nullptr");
247 } else if (!is_loaded()) {
248 st->print_cr("UNLOADED");
249 } else {
250 GUARDED_VM_ENTRY(get_oop()->print_on(st);)
251 }
252 }