src/share/vm/code/codeBlob.hpp

Wed, 14 Oct 2009 10:36:57 -0700

author
never
date
Wed, 14 Oct 2009 10:36:57 -0700
changeset 1449
8e954aedbb81
parent 1424
148e5441d916
child 1570
e66fd840cb6b
permissions
-rw-r--r--

6889869: assert(!Interpreter::bytecode_should_reexecute(code),"should not reexecute")
Reviewed-by: jrose, kvn, cfang, twisti

duke@435 1 /*
duke@435 2 * Copyright 1998-2007 Sun Microsystems, Inc. All Rights Reserved.
duke@435 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435 4 *
duke@435 5 * This code is free software; you can redistribute it and/or modify it
duke@435 6 * under the terms of the GNU General Public License version 2 only, as
duke@435 7 * published by the Free Software Foundation.
duke@435 8 *
duke@435 9 * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435 12 * version 2 for more details (a copy is included in the LICENSE file that
duke@435 13 * accompanied this code).
duke@435 14 *
duke@435 15 * You should have received a copy of the GNU General Public License version
duke@435 16 * 2 along with this work; if not, write to the Free Software Foundation,
duke@435 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435 18 *
duke@435 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435 20 * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435 21 * have any questions.
duke@435 22 *
duke@435 23 */
duke@435 24
duke@435 25 // CodeBlob - superclass for all entries in the CodeCache.
duke@435 26 //
duke@435 27 // Suptypes are:
duke@435 28 // nmethod : Compiled Java methods (include method that calls to native code)
duke@435 29 // RuntimeStub : Call to VM runtime methods
duke@435 30 // DeoptimizationBlob : Used for deoptimizatation
duke@435 31 // ExceptionBlob : Used for stack unrolling
duke@435 32 // SafepointBlob : Used to handle illegal instruction exceptions
duke@435 33 //
duke@435 34 //
duke@435 35 // Layout:
duke@435 36 // - header
duke@435 37 // - relocation
duke@435 38 // - instruction space
duke@435 39 // - data space
duke@435 40 class DeoptimizationBlob;
duke@435 41
duke@435 42 class CodeBlob VALUE_OBJ_CLASS_SPEC {
duke@435 43
duke@435 44 friend class VMStructs;
duke@435 45
duke@435 46 private:
duke@435 47 const char* _name;
duke@435 48 int _size; // total size of CodeBlob in bytes
duke@435 49 int _header_size; // size of header (depends on subclass)
duke@435 50 int _relocation_size; // size of relocation
duke@435 51 int _instructions_offset; // offset to where instructions region begins
duke@435 52 int _frame_complete_offset; // instruction offsets in [0.._frame_complete_offset) have
duke@435 53 // not finished setting up their frame. Beware of pc's in
duke@435 54 // that range. There is a similar range(s) on returns
duke@435 55 // which we don't detect.
duke@435 56 int _data_offset; // offset to where data region begins
duke@435 57 int _oops_offset; // offset to where embedded oop table begins (inside data)
duke@435 58 int _oops_length; // number of embedded oops
duke@435 59 int _frame_size; // size of stack frame
duke@435 60 OopMapSet* _oop_maps; // OopMap for this CodeBlob
duke@435 61 CodeComments _comments;
duke@435 62
duke@435 63 friend class OopRecorder;
duke@435 64
duke@435 65 void fix_oop_relocations(address begin, address end, bool initialize_immediates);
duke@435 66 inline void initialize_immediate_oop(oop* dest, jobject handle);
duke@435 67
duke@435 68 public:
duke@435 69 // Returns the space needed for CodeBlob
duke@435 70 static unsigned int allocation_size(CodeBuffer* cb, int header_size);
duke@435 71
duke@435 72 // Creation
duke@435 73 // a) simple CodeBlob
duke@435 74 // frame_complete is the offset from the beginning of the instructions
duke@435 75 // to where the frame setup (from stackwalk viewpoint) is complete.
duke@435 76 CodeBlob(const char* name, int header_size, int size, int frame_complete, int locs_size);
duke@435 77
duke@435 78 // b) full CodeBlob
duke@435 79 CodeBlob(
duke@435 80 const char* name,
duke@435 81 CodeBuffer* cb,
duke@435 82 int header_size,
duke@435 83 int size,
duke@435 84 int frame_complete,
duke@435 85 int frame_size,
duke@435 86 OopMapSet* oop_maps
duke@435 87 );
duke@435 88
duke@435 89 // Deletion
duke@435 90 void flush();
duke@435 91
duke@435 92 // Typing
duke@435 93 virtual bool is_buffer_blob() const { return false; }
duke@435 94 virtual bool is_nmethod() const { return false; }
duke@435 95 virtual bool is_runtime_stub() const { return false; }
duke@435 96 virtual bool is_deoptimization_stub() const { return false; }
duke@435 97 virtual bool is_uncommon_trap_stub() const { return false; }
duke@435 98 virtual bool is_exception_stub() const { return false; }
duke@435 99 virtual bool is_safepoint_stub() const { return false; }
duke@435 100 virtual bool is_adapter_blob() const { return false; }
duke@435 101
duke@435 102 virtual bool is_compiled_by_c2() const { return false; }
duke@435 103 virtual bool is_compiled_by_c1() const { return false; }
duke@435 104
duke@435 105 // Boundaries
duke@435 106 address header_begin() const { return (address) this; }
duke@435 107 address header_end() const { return ((address) this) + _header_size; };
duke@435 108 relocInfo* relocation_begin() const { return (relocInfo*) header_end(); };
duke@435 109 relocInfo* relocation_end() const { return (relocInfo*)(header_end() + _relocation_size); }
duke@435 110 address instructions_begin() const { return (address) header_begin() + _instructions_offset; }
duke@435 111 address instructions_end() const { return (address) header_begin() + _data_offset; }
duke@435 112 address data_begin() const { return (address) header_begin() + _data_offset; }
duke@435 113 address data_end() const { return (address) header_begin() + _size; }
duke@435 114 oop* oops_begin() const { return (oop*) (header_begin() + _oops_offset); }
duke@435 115 oop* oops_end() const { return oops_begin() + _oops_length; }
duke@435 116
duke@435 117 // Offsets
duke@435 118 int relocation_offset() const { return _header_size; }
duke@435 119 int instructions_offset() const { return _instructions_offset; }
duke@435 120 int data_offset() const { return _data_offset; }
duke@435 121 int oops_offset() const { return _oops_offset; }
duke@435 122
duke@435 123 // Sizes
duke@435 124 int size() const { return _size; }
duke@435 125 int header_size() const { return _header_size; }
duke@435 126 int relocation_size() const { return (address) relocation_end() - (address) relocation_begin(); }
duke@435 127 int instructions_size() const { return instructions_end() - instructions_begin(); }
duke@435 128 int data_size() const { return data_end() - data_begin(); }
duke@435 129 int oops_size() const { return (address) oops_end() - (address) oops_begin(); }
duke@435 130
duke@435 131 // Containment
duke@435 132 bool blob_contains(address addr) const { return header_begin() <= addr && addr < data_end(); }
duke@435 133 bool relocation_contains(relocInfo* addr) const{ return relocation_begin() <= addr && addr < relocation_end(); }
duke@435 134 bool instructions_contains(address addr) const { return instructions_begin() <= addr && addr < instructions_end(); }
duke@435 135 bool data_contains(address addr) const { return data_begin() <= addr && addr < data_end(); }
duke@435 136 bool oops_contains(oop* addr) const { return oops_begin() <= addr && addr < oops_end(); }
duke@435 137 bool contains(address addr) const { return instructions_contains(addr); }
duke@435 138 bool is_frame_complete_at(address addr) const { return instructions_contains(addr) &&
duke@435 139 addr >= instructions_begin() + _frame_complete_offset; }
duke@435 140
duke@435 141 // Relocation support
duke@435 142 void fix_oop_relocations(address begin, address end) {
duke@435 143 fix_oop_relocations(begin, end, false);
duke@435 144 }
duke@435 145 void fix_oop_relocations() {
duke@435 146 fix_oop_relocations(NULL, NULL, false);
duke@435 147 }
duke@435 148 relocInfo::relocType reloc_type_for_address(address pc);
duke@435 149 bool is_at_poll_return(address pc);
duke@435 150 bool is_at_poll_or_poll_return(address pc);
duke@435 151
duke@435 152 // Support for oops in scopes and relocs:
duke@435 153 // Note: index 0 is reserved for null.
duke@435 154 oop oop_at(int index) const { return index == 0? (oop)NULL: *oop_addr_at(index); }
duke@435 155 oop* oop_addr_at(int index) const{ // for GC
duke@435 156 // relocation indexes are biased by 1 (because 0 is reserved)
duke@435 157 assert(index > 0 && index <= _oops_length, "must be a valid non-zero index");
duke@435 158 return &oops_begin()[index-1];
duke@435 159 }
duke@435 160
duke@435 161 void copy_oops(GrowableArray<jobject>* oops);
duke@435 162
duke@435 163 // CodeCache support: really only used by the nmethods, but in order to get
duke@435 164 // asserts and certain bookkeeping to work in the CodeCache they are defined
duke@435 165 // virtual here.
duke@435 166 virtual bool is_zombie() const { return false; }
duke@435 167 virtual bool is_locked_by_vm() const { return false; }
duke@435 168
duke@435 169 virtual bool is_unloaded() const { return false; }
duke@435 170 virtual bool is_not_entrant() const { return false; }
duke@435 171
duke@435 172 // GC support
duke@435 173 virtual bool is_alive() const = 0;
duke@435 174 virtual void do_unloading(BoolObjectClosure* is_alive,
duke@435 175 OopClosure* keep_alive,
duke@435 176 bool unloading_occurred);
duke@435 177 virtual void oops_do(OopClosure* f) = 0;
jrose@1424 178 // (All CodeBlob subtypes other than NMethod currently have
jrose@1424 179 // an empty oops_do() method.
duke@435 180
duke@435 181 // OopMap for frame
duke@435 182 OopMapSet* oop_maps() const { return _oop_maps; }
duke@435 183 void set_oop_maps(OopMapSet* p);
duke@435 184 OopMap* oop_map_for_return_address(address return_address);
duke@435 185 virtual void preserve_callee_argument_oops(frame fr, const RegisterMap* reg_map, OopClosure* f) { ShouldNotReachHere(); }
duke@435 186
duke@435 187 // Frame support
duke@435 188 int frame_size() const { return _frame_size; }
duke@435 189 void set_frame_size(int size) { _frame_size = size; }
duke@435 190
duke@435 191 // Returns true, if the next frame is responsible for GC'ing oops passed as arguments
duke@435 192 virtual bool caller_must_gc_arguments(JavaThread* thread) const { return false; }
duke@435 193
duke@435 194 // Naming
duke@435 195 const char* name() const { return _name; }
duke@435 196 void set_name(const char* name) { _name = name; }
duke@435 197
duke@435 198 // Debugging
duke@435 199 virtual void verify();
duke@435 200 virtual void print() const PRODUCT_RETURN;
duke@435 201 virtual void print_value_on(outputStream* st) const PRODUCT_RETURN;
duke@435 202
duke@435 203 // Print the comment associated with offset on stream, if there is one
duke@435 204 void print_block_comment(outputStream* stream, intptr_t offset) {
duke@435 205 _comments.print_block_comment(stream, offset);
duke@435 206 }
duke@435 207
duke@435 208 // Transfer ownership of comments to this CodeBlob
duke@435 209 void set_comments(CodeComments& comments) {
duke@435 210 _comments.assign(comments);
duke@435 211 }
duke@435 212 };
duke@435 213
duke@435 214
duke@435 215 //----------------------------------------------------------------------------------------------------
duke@435 216 // BufferBlob: used to hold non-relocatable machine code such as the interpreter, stubroutines, etc.
duke@435 217
duke@435 218 class BufferBlob: public CodeBlob {
duke@435 219 friend class VMStructs;
duke@435 220 private:
duke@435 221 // Creation support
duke@435 222 BufferBlob(const char* name, int size);
duke@435 223 BufferBlob(const char* name, int size, CodeBuffer* cb);
duke@435 224
duke@435 225 void* operator new(size_t s, unsigned size);
duke@435 226
duke@435 227 public:
duke@435 228 // Creation
duke@435 229 static BufferBlob* create(const char* name, int buffer_size);
duke@435 230 static BufferBlob* create(const char* name, CodeBuffer* cb);
duke@435 231
duke@435 232 static void free(BufferBlob* buf);
duke@435 233
duke@435 234 // Typing
duke@435 235 bool is_buffer_blob() const { return true; }
duke@435 236 bool is_adapter_blob() const;
duke@435 237
duke@435 238 // GC/Verification support
duke@435 239 void preserve_callee_argument_oops(frame fr, const RegisterMap* reg_map, OopClosure* f) { /* nothing to do */ }
duke@435 240 bool is_alive() const { return true; }
duke@435 241 void do_unloading(BoolObjectClosure* is_alive,
duke@435 242 OopClosure* keep_alive,
duke@435 243 bool unloading_occurred) { /* do nothing */ }
duke@435 244
duke@435 245 void oops_do(OopClosure* f) { /* do nothing*/ }
duke@435 246
duke@435 247 void verify();
duke@435 248 void print() const PRODUCT_RETURN;
duke@435 249 void print_value_on(outputStream* st) const PRODUCT_RETURN;
duke@435 250 };
duke@435 251
duke@435 252
duke@435 253 //----------------------------------------------------------------------------------------------------
duke@435 254 // RuntimeStub: describes stubs used by compiled code to call a (static) C++ runtime routine
duke@435 255
duke@435 256 class RuntimeStub: public CodeBlob {
duke@435 257 friend class VMStructs;
duke@435 258 private:
duke@435 259 bool _caller_must_gc_arguments;
duke@435 260
duke@435 261 // Creation support
duke@435 262 RuntimeStub(
duke@435 263 const char* name,
duke@435 264 CodeBuffer* cb,
duke@435 265 int size,
duke@435 266 int frame_complete,
duke@435 267 int frame_size,
duke@435 268 OopMapSet* oop_maps,
duke@435 269 bool caller_must_gc_arguments
duke@435 270 );
duke@435 271
duke@435 272 void* operator new(size_t s, unsigned size);
duke@435 273
duke@435 274 public:
duke@435 275 // Creation
duke@435 276 static RuntimeStub* new_runtime_stub(
duke@435 277 const char* stub_name,
duke@435 278 CodeBuffer* cb,
duke@435 279 int frame_complete,
duke@435 280 int frame_size,
duke@435 281 OopMapSet* oop_maps,
duke@435 282 bool caller_must_gc_arguments
duke@435 283 );
duke@435 284
duke@435 285 // Typing
duke@435 286 bool is_runtime_stub() const { return true; }
duke@435 287
duke@435 288 // GC support
duke@435 289 bool caller_must_gc_arguments(JavaThread* thread) const { return _caller_must_gc_arguments; }
duke@435 290
duke@435 291 address entry_point() { return instructions_begin(); }
duke@435 292
duke@435 293 // GC/Verification support
duke@435 294 void preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) { /* nothing to do */ }
duke@435 295 bool is_alive() const { return true; }
duke@435 296 void do_unloading(BoolObjectClosure* is_alive,
duke@435 297 OopClosure* keep_alive,
duke@435 298 bool unloading_occurred) { /* do nothing */ }
duke@435 299 void oops_do(OopClosure* f) { /* do-nothing*/ }
duke@435 300
duke@435 301 void verify();
duke@435 302 void print() const PRODUCT_RETURN;
duke@435 303 void print_value_on(outputStream* st) const PRODUCT_RETURN;
duke@435 304 };
duke@435 305
duke@435 306
duke@435 307 //----------------------------------------------------------------------------------------------------
duke@435 308 // Super-class for all blobs that exist in only one instance. Implements default behaviour.
duke@435 309
duke@435 310 class SingletonBlob: public CodeBlob {
duke@435 311 friend class VMStructs;
duke@435 312 public:
duke@435 313 SingletonBlob(
duke@435 314 const char* name,
duke@435 315 CodeBuffer* cb,
duke@435 316 int header_size,
duke@435 317 int size,
duke@435 318 int frame_size,
duke@435 319 OopMapSet* oop_maps
duke@435 320 )
duke@435 321 : CodeBlob(name, cb, header_size, size, CodeOffsets::frame_never_safe, frame_size, oop_maps)
duke@435 322 {};
duke@435 323
duke@435 324 bool is_alive() const { return true; }
duke@435 325 void do_unloading(BoolObjectClosure* is_alive,
duke@435 326 OopClosure* keep_alive,
duke@435 327 bool unloading_occurred) { /* do-nothing*/ }
duke@435 328
duke@435 329 void verify(); // does nothing
duke@435 330 void print() const PRODUCT_RETURN;
duke@435 331 void print_value_on(outputStream* st) const PRODUCT_RETURN;
duke@435 332 };
duke@435 333
duke@435 334
duke@435 335 //----------------------------------------------------------------------------------------------------
duke@435 336 // DeoptimizationBlob
duke@435 337
duke@435 338 class DeoptimizationBlob: public SingletonBlob {
duke@435 339 friend class VMStructs;
duke@435 340 private:
duke@435 341 int _unpack_offset;
duke@435 342 int _unpack_with_exception;
duke@435 343 int _unpack_with_reexecution;
duke@435 344
duke@435 345 int _unpack_with_exception_in_tls;
duke@435 346
duke@435 347 // Creation support
duke@435 348 DeoptimizationBlob(
duke@435 349 CodeBuffer* cb,
duke@435 350 int size,
duke@435 351 OopMapSet* oop_maps,
duke@435 352 int unpack_offset,
duke@435 353 int unpack_with_exception_offset,
duke@435 354 int unpack_with_reexecution_offset,
duke@435 355 int frame_size
duke@435 356 );
duke@435 357
duke@435 358 void* operator new(size_t s, unsigned size);
duke@435 359
duke@435 360 public:
duke@435 361 // Creation
duke@435 362 static DeoptimizationBlob* create(
duke@435 363 CodeBuffer* cb,
duke@435 364 OopMapSet* oop_maps,
duke@435 365 int unpack_offset,
duke@435 366 int unpack_with_exception_offset,
duke@435 367 int unpack_with_reexecution_offset,
duke@435 368 int frame_size
duke@435 369 );
duke@435 370
duke@435 371 // Typing
duke@435 372 bool is_deoptimization_stub() const { return true; }
duke@435 373 const DeoptimizationBlob *as_deoptimization_stub() const { return this; }
duke@435 374 bool exception_address_is_unpack_entry(address pc) const {
duke@435 375 address unpack_pc = unpack();
duke@435 376 return (pc == unpack_pc || (pc + frame::pc_return_offset) == unpack_pc);
duke@435 377 }
duke@435 378
duke@435 379
duke@435 380
duke@435 381
duke@435 382 // GC for args
duke@435 383 void preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) { /* Nothing to do */ }
duke@435 384
duke@435 385 // Iteration
duke@435 386 void oops_do(OopClosure* f) {}
duke@435 387
duke@435 388 // Printing
duke@435 389 void print_value_on(outputStream* st) const PRODUCT_RETURN;
duke@435 390
duke@435 391 address unpack() const { return instructions_begin() + _unpack_offset; }
duke@435 392 address unpack_with_exception() const { return instructions_begin() + _unpack_with_exception; }
duke@435 393 address unpack_with_reexecution() const { return instructions_begin() + _unpack_with_reexecution; }
duke@435 394
duke@435 395 // Alternate entry point for C1 where the exception and issuing pc
duke@435 396 // are in JavaThread::_exception_oop and JavaThread::_exception_pc
duke@435 397 // instead of being in registers. This is needed because C1 doesn't
duke@435 398 // model exception paths in a way that keeps these registers free so
duke@435 399 // there may be live values in those registers during deopt.
duke@435 400 void set_unpack_with_exception_in_tls_offset(int offset) {
duke@435 401 _unpack_with_exception_in_tls = offset;
duke@435 402 assert(contains(instructions_begin() + _unpack_with_exception_in_tls), "must be PC inside codeblob");
duke@435 403 }
duke@435 404 address unpack_with_exception_in_tls() const { return instructions_begin() + _unpack_with_exception_in_tls; }
duke@435 405 };
duke@435 406
duke@435 407
duke@435 408 //----------------------------------------------------------------------------------------------------
duke@435 409 // UncommonTrapBlob (currently only used by Compiler 2)
duke@435 410
duke@435 411 #ifdef COMPILER2
duke@435 412
duke@435 413 class UncommonTrapBlob: public SingletonBlob {
duke@435 414 friend class VMStructs;
duke@435 415 private:
duke@435 416 // Creation support
duke@435 417 UncommonTrapBlob(
duke@435 418 CodeBuffer* cb,
duke@435 419 int size,
duke@435 420 OopMapSet* oop_maps,
duke@435 421 int frame_size
duke@435 422 );
duke@435 423
duke@435 424 void* operator new(size_t s, unsigned size);
duke@435 425
duke@435 426 public:
duke@435 427 // Creation
duke@435 428 static UncommonTrapBlob* create(
duke@435 429 CodeBuffer* cb,
duke@435 430 OopMapSet* oop_maps,
duke@435 431 int frame_size
duke@435 432 );
duke@435 433
duke@435 434 // GC for args
duke@435 435 void preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) { /* nothing to do */ }
duke@435 436
duke@435 437 // Typing
duke@435 438 bool is_uncommon_trap_stub() const { return true; }
duke@435 439
duke@435 440 // Iteration
duke@435 441 void oops_do(OopClosure* f) {}
duke@435 442 };
duke@435 443
duke@435 444
duke@435 445 //----------------------------------------------------------------------------------------------------
duke@435 446 // ExceptionBlob: used for exception unwinding in compiled code (currently only used by Compiler 2)
duke@435 447
duke@435 448 class ExceptionBlob: public SingletonBlob {
duke@435 449 friend class VMStructs;
duke@435 450 private:
duke@435 451 // Creation support
duke@435 452 ExceptionBlob(
duke@435 453 CodeBuffer* cb,
duke@435 454 int size,
duke@435 455 OopMapSet* oop_maps,
duke@435 456 int frame_size
duke@435 457 );
duke@435 458
duke@435 459 void* operator new(size_t s, unsigned size);
duke@435 460
duke@435 461 public:
duke@435 462 // Creation
duke@435 463 static ExceptionBlob* create(
duke@435 464 CodeBuffer* cb,
duke@435 465 OopMapSet* oop_maps,
duke@435 466 int frame_size
duke@435 467 );
duke@435 468
duke@435 469 // GC for args
duke@435 470 void preserve_callee_argument_oops(frame fr, const RegisterMap* reg_map, OopClosure* f) { /* nothing to do */ }
duke@435 471
duke@435 472 // Typing
duke@435 473 bool is_exception_stub() const { return true; }
duke@435 474
duke@435 475 // Iteration
duke@435 476 void oops_do(OopClosure* f) {}
duke@435 477 };
duke@435 478 #endif // COMPILER2
duke@435 479
duke@435 480
duke@435 481 //----------------------------------------------------------------------------------------------------
duke@435 482 // SafepointBlob: handles illegal_instruction exceptions during a safepoint
duke@435 483
duke@435 484 class SafepointBlob: public SingletonBlob {
duke@435 485 friend class VMStructs;
duke@435 486 private:
duke@435 487 // Creation support
duke@435 488 SafepointBlob(
duke@435 489 CodeBuffer* cb,
duke@435 490 int size,
duke@435 491 OopMapSet* oop_maps,
duke@435 492 int frame_size
duke@435 493 );
duke@435 494
duke@435 495 void* operator new(size_t s, unsigned size);
duke@435 496
duke@435 497 public:
duke@435 498 // Creation
duke@435 499 static SafepointBlob* create(
duke@435 500 CodeBuffer* cb,
duke@435 501 OopMapSet* oop_maps,
duke@435 502 int frame_size
duke@435 503 );
duke@435 504
duke@435 505 // GC for args
duke@435 506 void preserve_callee_argument_oops(frame fr, const RegisterMap* reg_map, OopClosure* f) { /* nothing to do */ }
duke@435 507
duke@435 508 // Typing
duke@435 509 bool is_safepoint_stub() const { return true; }
duke@435 510
duke@435 511 // Iteration
duke@435 512 void oops_do(OopClosure* f) {}
duke@435 513 };

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