1 /*
2 * Copyright (c) 1999, 2015, 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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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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20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #include "precompiled.hpp"
26 #include "ci/ciField.hpp"
27 #include "ci/ciInstanceKlass.hpp"
28 #include "ci/ciUtilities.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "gc/shared/collectedHeap.inline.hpp"
31 #include "interpreter/linkResolver.hpp"
32 #include "memory/universe.inline.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/fieldDescriptor.hpp"
35
36 // ciField
37 //
38 // This class represents the result of a field lookup in the VM.
39 // The lookup may not succeed, in which case the information in
40 // the ciField will be incomplete.
41
42 // The ciObjectFactory cannot create circular data structures in one query.
43 // To avoid vicious circularities, we initialize ciField::_type to NULL
44 // for reference types and derive it lazily from the ciField::_signature.
45 // Primitive types are eagerly initialized, and basic layout queries
46 // can succeed without initialization, using only the BasicType of the field.
47
48 // Notes on bootstrapping and shared CI objects: A field is shared if and
49 // only if it is (a) non-static and (b) declared by a shared instance klass.
50 // This allows non-static field lists to be cached on shared types.
51 // Because the _type field is lazily initialized, however, there is a
52 // special restriction that a shared field cannot cache an unshared type.
53 // This puts a small performance penalty on shared fields with unshared
54 // types, such as StackTraceElement[] Throwable.stackTrace.
55 // (Throwable is shared because ClassCastException is shared, but
56 // StackTraceElement is not presently shared.)
57
58 // It is not a vicious circularity for a ciField to recursively create
59 // the ciSymbols necessary to represent its name and signature.
60 // Therefore, these items are created eagerly, and the name and signature
61 // of a shared field are themselves shared symbols. This somewhat
62 // pollutes the set of shared CI objects: It grows from 50 to 93 items,
63 // with all of the additional 43 being uninteresting shared ciSymbols.
64 // This adds at most one step to the binary search, an amount which
65 // decreases for complex compilation tasks.
66
67 // ------------------------------------------------------------------
68 // ciField::ciField
69 ciField::ciField(ciInstanceKlass* klass, int index): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
70 ASSERT_IN_VM;
71 CompilerThread *thread = CompilerThread::current();
72
73 assert(ciObjectFactory::is_initialized(), "not a shared field");
74
75 assert(klass->get_instanceKlass()->is_linked(), "must be linked before using its constant-pool");
76
77 constantPoolHandle cpool(thread, klass->get_instanceKlass()->constants());
78
79 // Get the field's name, signature, and type.
80 Symbol* name = cpool->name_ref_at(index);
81 _name = ciEnv::current(thread)->get_symbol(name);
82
83 int nt_index = cpool->name_and_type_ref_index_at(index);
84 int sig_index = cpool->signature_ref_index_at(nt_index);
85 Symbol* signature = cpool->symbol_at(sig_index);
86 _signature = ciEnv::current(thread)->get_symbol(signature);
87
88 BasicType field_type = FieldType::basic_type(signature);
89
90 // If the field is a pointer type, get the klass of the
91 // field.
92 if (field_type == T_OBJECT || field_type == T_ARRAY) {
93 bool ignore;
94 // This is not really a class reference; the index always refers to the
95 // field's type signature, as a symbol. Linkage checks do not apply.
96 _type = ciEnv::current(thread)->get_klass_by_index(cpool, sig_index, ignore, klass);
97 } else {
98 _type = ciType::make(field_type);
99 }
100
101 _name = (ciSymbol*)ciEnv::current(thread)->get_symbol(name);
102
103 // Get the field's declared holder.
104 //
105 // Note: we actually create a ciInstanceKlass for this klass,
106 // even though we may not need to.
107 int holder_index = cpool->klass_ref_index_at(index);
108 bool holder_is_accessible;
109
110 ciKlass* generic_declared_holder = ciEnv::current(thread)->get_klass_by_index(cpool, holder_index,
111 holder_is_accessible,
112 klass);
113
114 if (generic_declared_holder->is_array_klass()) {
115 // If the declared holder of the field is an array class, assume that
116 // the canonical holder of that field is java.lang.Object. Arrays
117 // do not have fields; java.lang.Object is the only supertype of an
118 // array type that can declare fields and is therefore the canonical
119 // holder of the array type.
120 //
121 // Furthermore, the compilers assume that java.lang.Object does not
122 // have any fields. Therefore, the field is not looked up. Instead,
123 // the method returns partial information that will trigger special
124 // handling in ciField::will_link and will result in a
125 // java.lang.NoSuchFieldError exception being thrown by the compiled
126 // code (the expected behavior in this case).
127 _holder = ciEnv::current(thread)->Object_klass();
128 _offset = -1;
129 _is_constant = false;
130 return;
131 }
132
133 ciInstanceKlass* declared_holder = generic_declared_holder->as_instance_klass();
134
135 // The declared holder of this field may not have been loaded.
136 // Bail out with partial field information.
137 if (!holder_is_accessible) {
138 // _type has already been set.
139 // The default values for _flags and _constant_value will suffice.
140 // We need values for _holder, _offset, and _is_constant,
141 _holder = declared_holder;
142 _offset = -1;
143 _is_constant = false;
144 return;
145 }
146
147 InstanceKlass* loaded_decl_holder = declared_holder->get_instanceKlass();
148
149 // Perform the field lookup.
150 fieldDescriptor field_desc;
151 Klass* canonical_holder =
152 loaded_decl_holder->find_field(name, signature, &field_desc);
153 if (canonical_holder == NULL) {
154 // Field lookup failed. Will be detected by will_link.
155 _holder = declared_holder;
156 _offset = -1;
157 _is_constant = false;
158 return;
159 }
160
161 // Access check based on declared_holder. canonical_holder should not be used
162 // to check access because it can erroneously succeed. If this check fails,
163 // propagate the declared holder to will_link() which in turn will bail out
164 // compilation for this field access.
165 if (!Reflection::verify_field_access(klass->get_Klass(), declared_holder->get_Klass(), canonical_holder, field_desc.access_flags(), true)) {
166 _holder = declared_holder;
167 _offset = -1;
168 _is_constant = false;
169 return;
170 }
171
172 assert(canonical_holder == field_desc.field_holder(), "just checking");
173 initialize_from(&field_desc);
174 }
175
176 ciField::ciField(fieldDescriptor *fd): _known_to_link_with_put(NULL), _known_to_link_with_get(NULL) {
177 ASSERT_IN_VM;
178
179 // Get the field's name, signature, and type.
180 ciEnv* env = CURRENT_ENV;
181 _name = env->get_symbol(fd->name());
182 _signature = env->get_symbol(fd->signature());
183
184 BasicType field_type = fd->field_type();
185
186 // If the field is a pointer type, get the klass of the
187 // field.
188 if (field_type == T_OBJECT || field_type == T_ARRAY) {
189 _type = NULL; // must call compute_type on first access
190 } else {
191 _type = ciType::make(field_type);
192 }
193
194 initialize_from(fd);
195
196 // Either (a) it is marked shared, or else (b) we are done bootstrapping.
197 assert(is_shared() || ciObjectFactory::is_initialized(),
198 "bootstrap classes must not create & cache unshared fields");
199 }
200
201 void ciField::initialize_from(fieldDescriptor* fd) {
202 // Get the flags, offset, and canonical holder of the field.
203 _flags = ciFlags(fd->access_flags());
204 _offset = fd->offset();
205 _holder = CURRENT_ENV->get_instance_klass(fd->field_holder());
206
207 // Check to see if the field is constant.
208 Klass* k = _holder->get_Klass();
209 bool is_stable_field = FoldStableValues && is_stable();
210 assert(SystemDictionary::CallSite_klass() != NULL, "should be already initialized");
211 if (is_stable_field ||
212 (k == SystemDictionary::CallSite_klass() &&
213 _offset == java_lang_invoke_CallSite::target_offset_in_bytes())) {
214 _is_constant = true;
215 } else {
216 _is_constant = false;
217 }
218 }
219
220 // ------------------------------------------------------------------
221 // ciField::constant_value
222 // Get the constant value of a this static field.
223 ciConstant ciField::constant_value() {
224 assert(is_static() && is_constant(), "illegal call to constant_value()");
225 if (!_holder->is_initialized()) {
226 return ciConstant(); // Not initialized yet
227 }
228 if (_constant_value.basic_type() == T_ILLEGAL) {
229 // Static fields are placed in mirror objects.
230 VM_ENTRY_MARK;
231 ciInstance* mirror = CURRENT_ENV->get_instance(_holder->get_Klass()->java_mirror());
232 _constant_value = mirror->field_value_impl(type()->basic_type(), offset());
233 }
234 if (FoldStableValues && is_stable() && _constant_value.is_null_or_zero()) {
235 return ciConstant();
236 }
237 return _constant_value;
238 }
239
240 // ------------------------------------------------------------------
241 // ciField::constant_value_of
242 // Get the constant value of non-static final field in the given object.
243 ciConstant ciField::constant_value_of(ciObject* object) {
244 assert(!is_static() && is_constant(), "only if field is non-static constant");
245 assert(object->is_instance(), "must be instance");
246 ciConstant field_value = object->as_instance()->field_value(this);
247 if (FoldStableValues && is_stable() && field_value.is_null_or_zero()) {
248 return ciConstant();
249 }
250 return field_value;
251 }
252
253 // ------------------------------------------------------------------
254 // ciField::compute_type
255 //
256 // Lazily compute the type, if it is an instance klass.
257 ciType* ciField::compute_type() {
258 GUARDED_VM_ENTRY(return compute_type_impl();)
259 }
260
261 ciType* ciField::compute_type_impl() {
262 ciKlass* type = CURRENT_ENV->get_klass_by_name_impl(_holder, constantPoolHandle(), _signature, false);
263 if (!type->is_primitive_type() && is_shared()) {
264 // We must not cache a pointer to an unshared type, in a shared field.
265 bool type_is_also_shared = false;
266 if (type->is_type_array_klass()) {
267 type_is_also_shared = true; // int[] etc. are explicitly bootstrapped
268 } else if (type->is_instance_klass()) {
269 type_is_also_shared = type->as_instance_klass()->is_shared();
270 } else {
271 // Currently there is no 'shared' query for array types.
272 type_is_also_shared = !ciObjectFactory::is_initialized();
273 }
274 if (!type_is_also_shared)
275 return type; // Bummer.
276 }
277 _type = type;
278 return type;
279 }
280
281
282 // ------------------------------------------------------------------
283 // ciField::will_link
284 //
285 // Can a specific access to this field be made without causing
286 // link errors?
287 bool ciField::will_link(ciInstanceKlass* accessing_klass,
288 ciMethod* accessing_method,
289 Bytecodes::Code bc) {
290 VM_ENTRY_MARK;
291 assert(bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic ||
292 bc == Bytecodes::_getfield || bc == Bytecodes::_putfield,
293 "unexpected bytecode");
294
295 if (_offset == -1) {
296 // at creation we couldn't link to our holder so we need to
297 // maintain that stance, otherwise there's no safe way to use this
298 // ciField.
299 return false;
300 }
301
302 // Check for static/nonstatic mismatch
303 bool is_static = (bc == Bytecodes::_getstatic || bc == Bytecodes::_putstatic);
304 if (is_static != this->is_static()) {
305 return false;
306 }
307
308 // Get and put can have different accessibility rules
309 bool is_put = (bc == Bytecodes::_putfield || bc == Bytecodes::_putstatic);
310 if (is_put) {
311 if (_known_to_link_with_put == accessing_klass) {
312 return true;
313 }
314 } else {
315 if (_known_to_link_with_get == accessing_klass) {
316 return true;
317 }
318 }
319
320 LinkInfo link_info(_holder->get_instanceKlass(),
321 _name->get_symbol(), _signature->get_symbol(),
322 accessing_klass->get_Klass(), accessing_method->get_Method());
323 fieldDescriptor result;
324 LinkResolver::resolve_field(result, link_info, bc, false, KILL_COMPILE_ON_FATAL_(false));
325
326 // update the hit-cache, unless there is a problem with memory scoping:
327 if (accessing_klass->is_shared() || !is_shared()) {
328 if (is_put) {
329 _known_to_link_with_put = accessing_klass;
330 } else {
331 _known_to_link_with_get = accessing_klass;
332 }
333 }
334
335 return true;
336 }
337
338 // ------------------------------------------------------------------
339 // ciField::print
340 void ciField::print() {
341 tty->print("<ciField name=");
342 _holder->print_name();
343 tty->print(".");
344 _name->print_symbol();
345 tty->print(" signature=");
346 _signature->print_symbol();
347 tty->print(" offset=%d type=", _offset);
348 if (_type != NULL)
349 _type->print_name();
350 else
351 tty->print("(reference)");
352 tty->print(" flags=%04x", flags().as_int());
353 tty->print(" is_constant=%s", bool_to_str(_is_constant));
354 if (_is_constant && is_static()) {
355 tty->print(" constant_value=");
356 _constant_value.print();
357 }
358 tty->print(">");
359 }
360
361 // ------------------------------------------------------------------
362 // ciField::print_name_on
363 //
364 // Print the name of this field
365 void ciField::print_name_on(outputStream* st) {
366 name()->print_symbol_on(st);
367 }