1 /* 2 * Copyright (c) 1999, 2017, 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_ATOMIC_HPP 26 #define SHARE_VM_RUNTIME_ATOMIC_HPP 27 28 #include "memory/allocation.hpp" 29 #include "metaprogramming/conditional.hpp" 30 #include "metaprogramming/enableIf.hpp" 31 #include "metaprogramming/isIntegral.hpp" 32 #include "metaprogramming/isPointer.hpp" 33 #include "metaprogramming/isSame.hpp" 34 #include "metaprogramming/primitiveConversions.hpp" 35 #include "metaprogramming/removeCV.hpp" 36 #include "metaprogramming/removePointer.hpp" 37 #include "utilities/align.hpp" 38 #include "utilities/macros.hpp" 39 40 enum cmpxchg_memory_order { 41 memory_order_relaxed, 42 // Use value which doesn't interfere with C++2011. We need to be more conservative. 43 memory_order_conservative = 8 44 }; 45 46 class Atomic : AllStatic { 47 public: 48 // Atomic operations on jlong types are not available on all 32-bit 49 // platforms. If atomic ops on jlongs are defined here they must only 50 // be used from code that verifies they are available at runtime and 51 // can provide an alternative action if not - see supports_cx8() for 52 // a means to test availability. 53 54 // The memory operations that are mentioned with each of the atomic 55 // function families come from src/share/vm/runtime/orderAccess.hpp, 56 // e.g., <fence> is described in that file and is implemented by the 57 // OrderAccess::fence() function. See that file for the gory details 58 // on the Memory Access Ordering Model. 59 60 // All of the atomic operations that imply a read-modify-write action 61 // guarantee a two-way memory barrier across that operation. Historically 62 // these semantics reflect the strength of atomic operations that are 63 // provided on SPARC/X86. We assume that strength is necessary unless 64 // we can prove that a weaker form is sufficiently safe. 65 66 // Atomically store to a location 67 // The type T must be either a pointer type convertible to or equal 68 // to D, an integral/enum type equal to D, or a type equal to D that 69 // is primitive convertible using PrimitiveConversions. 70 template<typename T, typename D> 71 inline static void store(T store_value, volatile D* dest); 72 73 inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest) { 74 Atomic::store(store_value, dest); 75 } 76 77 inline static void store_ptr(void* store_value, volatile void* dest) { 78 Atomic::store(store_value, reinterpret_cast<void* volatile*>(dest)); 79 } 80 81 // Atomically load from a location 82 // The type T must be either a pointer type, an integral/enum type, 83 // or a type that is primitive convertible using PrimitiveConversions. 84 template<typename T> 85 inline static T load(const volatile T* dest); 86 87 // Atomically add to a location. Returns updated value. add*() provide: 88 // <fence> add-value-to-dest <membar StoreLoad|StoreStore> 89 90 template<typename I, typename D> 91 inline static D add(I add_value, D volatile* dest); 92 93 inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest) { 94 return add(add_value, dest); 95 } 96 97 inline static void* add_ptr(intptr_t add_value, volatile void* dest) { 98 return add(add_value, reinterpret_cast<char* volatile*>(dest)); 99 } 100 101 // Atomically increment location. inc() provide: 102 // <fence> increment-dest <membar StoreLoad|StoreStore> 103 // The type D may be either a pointer type, or an integral 104 // type. If it is a pointer type, then the increment is 105 // scaled to the size of the type pointed to by the pointer. 106 template<typename D> 107 inline static void inc(D volatile* dest); 108 109 // Atomically decrement a location. dec() provide: 110 // <fence> decrement-dest <membar StoreLoad|StoreStore> 111 // The type D may be either a pointer type, or an integral 112 // type. If it is a pointer type, then the decrement is 113 // scaled to the size of the type pointed to by the pointer. 114 template<typename D> 115 inline static void dec(D volatile* dest); 116 117 // Performs atomic exchange of *dest with exchange_value. Returns old 118 // prior value of *dest. xchg*() provide: 119 // <fence> exchange-value-with-dest <membar StoreLoad|StoreStore> 120 // The type T must be either a pointer type convertible to or equal 121 // to D, an integral/enum type equal to D, or a type equal to D that 122 // is primitive convertible using PrimitiveConversions. 123 template<typename T, typename D> 124 inline static D xchg(T exchange_value, volatile D* dest); 125 126 inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest) { 127 return xchg(exchange_value, dest); 128 } 129 130 inline static void* xchg_ptr(void* exchange_value, volatile void* dest) { 131 return xchg(exchange_value, reinterpret_cast<void* volatile*>(dest)); 132 } 133 134 // Performs atomic compare of *dest and compare_value, and exchanges 135 // *dest with exchange_value if the comparison succeeded. Returns prior 136 // value of *dest. cmpxchg*() provide: 137 // <fence> compare-and-exchange <membar StoreLoad|StoreStore> 138 139 template<typename T, typename D, typename U> 140 inline static D cmpxchg(T exchange_value, 141 D volatile* dest, 142 U compare_value, 143 cmpxchg_memory_order order = memory_order_conservative); 144 145 // Performs atomic compare of *dest and NULL, and replaces *dest 146 // with exchange_value if the comparison succeeded. Returns true if 147 // the comparison succeeded and the exchange occurred. This is 148 // often used as part of lazy initialization, as a lock-free 149 // alternative to the Double-Checked Locking Pattern. 150 template<typename T, typename D> 151 inline static bool replace_if_null(T* value, D* volatile* dest, 152 cmpxchg_memory_order order = memory_order_conservative); 153 154 inline static intptr_t cmpxchg_ptr(intptr_t exchange_value, 155 volatile intptr_t* dest, 156 intptr_t compare_value, 157 cmpxchg_memory_order order = memory_order_conservative) { 158 return cmpxchg(exchange_value, dest, compare_value, order); 159 } 160 161 inline static void* cmpxchg_ptr(void* exchange_value, 162 volatile void* dest, 163 void* compare_value, 164 cmpxchg_memory_order order = memory_order_conservative) { 165 return cmpxchg(exchange_value, 166 reinterpret_cast<void* volatile*>(dest), 167 compare_value, 168 order); 169 } 170 171 private: 172 // Test whether From is implicitly convertible to To. 173 // From and To must be pointer types. 174 // Note: Provides the limited subset of C++11 std::is_convertible 175 // that is needed here. 176 template<typename From, typename To> struct IsPointerConvertible; 177 178 // Dispatch handler for store. Provides type-based validity 179 // checking and limited conversions around calls to the platform- 180 // specific implementation layer provided by PlatformOp. 181 template<typename T, typename D, typename PlatformOp, typename Enable = void> 182 struct StoreImpl; 183 184 // Platform-specific implementation of store. Support for sizes 185 // of 1, 2, 4, and (if different) pointer size bytes are required. 186 // The class is a function object that must be default constructable, 187 // with these requirements: 188 // 189 // either: 190 // - dest is of type D*, an integral, enum or pointer type. 191 // - new_value are of type T, an integral, enum or pointer type D or 192 // pointer type convertible to D. 193 // or: 194 // - T and D are the same and are primitive convertible using PrimitiveConversions 195 // and either way: 196 // - platform_store is an object of type PlatformStore<sizeof(T)>. 197 // 198 // Then 199 // platform_store(new_value, dest) 200 // must be a valid expression. 201 // 202 // The default implementation is a volatile store. If a platform 203 // requires more for e.g. 64 bit stores, a specialization is required 204 template<size_t byte_size> struct PlatformStore; 205 206 // Dispatch handler for load. Provides type-based validity 207 // checking and limited conversions around calls to the platform- 208 // specific implementation layer provided by PlatformOp. 209 template<typename T, typename PlatformOp, typename Enable = void> 210 struct LoadImpl; 211 212 // Platform-specific implementation of load. Support for sizes of 213 // 1, 2, 4 bytes and (if different) pointer size bytes are required. 214 // The class is a function object that must be default 215 // constructable, with these requirements: 216 // 217 // - dest is of type T*, an integral, enum or pointer type, or 218 // T is convertible to a primitive type using PrimitiveConversions 219 // - platform_load is an object of type PlatformLoad<sizeof(T)>. 220 // 221 // Then 222 // platform_load(src) 223 // must be a valid expression, returning a result convertible to T. 224 // 225 // The default implementation is a volatile load. If a platform 226 // requires more for e.g. 64 bit loads, a specialization is required 227 template<size_t byte_size> struct PlatformLoad; 228 229 // Dispatch handler for add. Provides type-based validity checking 230 // and limited conversions around calls to the platform-specific 231 // implementation layer provided by PlatformAdd. 232 template<typename I, typename D, typename Enable = void> 233 struct AddImpl; 234 235 // Platform-specific implementation of add. Support for sizes of 4 236 // bytes and (if different) pointer size bytes are required. The 237 // class is a function object that must be default constructable, 238 // with these requirements: 239 // 240 // - dest is of type D*, an integral or pointer type. 241 // - add_value is of type I, an integral type. 242 // - sizeof(I) == sizeof(D). 243 // - if D is an integral type, I == D. 244 // - platform_add is an object of type PlatformAdd<sizeof(D)>. 245 // 246 // Then 247 // platform_add(add_value, dest) 248 // must be a valid expression, returning a result convertible to D. 249 // 250 // No definition is provided; all platforms must explicitly define 251 // this class and any needed specializations. 252 template<size_t byte_size> struct PlatformAdd; 253 254 // Helper base classes for defining PlatformAdd. To use, define 255 // PlatformAdd or a specialization that derives from one of these, 256 // and include in the PlatformAdd definition the support function 257 // (described below) required by the base class. 258 // 259 // These classes implement the required function object protocol for 260 // PlatformAdd, using a support function template provided by the 261 // derived class. Let add_value (of type I) and dest (of type D) be 262 // the arguments the object is called with. If D is a pointer type 263 // P*, then let addend (of type I) be add_value * sizeof(P); 264 // otherwise, addend is add_value. 265 // 266 // FetchAndAdd requires the derived class to provide 267 // fetch_and_add(addend, dest) 268 // atomically adding addend to the value of dest, and returning the 269 // old value. 270 // 271 // AddAndFetch requires the derived class to provide 272 // add_and_fetch(addend, dest) 273 // atomically adding addend to the value of dest, and returning the 274 // new value. 275 // 276 // When D is a pointer type P*, both fetch_and_add and add_and_fetch 277 // treat it as if it were a uintptr_t; they do not perform any 278 // scaling of the addend, as that has already been done by the 279 // caller. 280 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11. 281 template<typename Derived> struct FetchAndAdd; 282 template<typename Derived> struct AddAndFetch; 283 private: 284 285 // Support for platforms that implement some variants of add using a 286 // (typically out of line) non-template helper function. The 287 // generic arguments passed to PlatformAdd need to be translated to 288 // the appropriate type for the helper function, the helper function 289 // invoked on the translated arguments, and the result translated 290 // back. Type is the parameter / return type of the helper 291 // function. No scaling of add_value is performed when D is a pointer 292 // type, so this function can be used to implement the support function 293 // required by AddAndFetch. 294 template<typename Type, typename Fn, typename I, typename D> 295 static D add_using_helper(Fn fn, I add_value, D volatile* dest); 296 297 // Dispatch handler for cmpxchg. Provides type-based validity 298 // checking and limited conversions around calls to the 299 // platform-specific implementation layer provided by 300 // PlatformCmpxchg. 301 template<typename T, typename D, typename U, typename Enable = void> 302 struct CmpxchgImpl; 303 304 // Platform-specific implementation of cmpxchg. Support for sizes 305 // of 1, 4, and 8 are required. The class is a function object that 306 // must be default constructable, with these requirements: 307 // 308 // - dest is of type T*. 309 // - exchange_value and compare_value are of type T. 310 // - order is of type cmpxchg_memory_order. 311 // - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>. 312 // 313 // Then 314 // platform_cmpxchg(exchange_value, dest, compare_value, order) 315 // must be a valid expression, returning a result convertible to T. 316 // 317 // A default definition is provided, which declares a function template 318 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const 319 // 320 // For each required size, a platform must either provide an 321 // appropriate definition of that function, or must entirely 322 // specialize the class template for that size. 323 template<size_t byte_size> struct PlatformCmpxchg; 324 325 // Support for platforms that implement some variants of cmpxchg 326 // using a (typically out of line) non-template helper function. 327 // The generic arguments passed to PlatformCmpxchg need to be 328 // translated to the appropriate type for the helper function, the 329 // helper invoked on the translated arguments, and the result 330 // translated back. Type is the parameter / return type of the 331 // helper function. 332 template<typename Type, typename Fn, typename T> 333 static T cmpxchg_using_helper(Fn fn, 334 T exchange_value, 335 T volatile* dest, 336 T compare_value); 337 338 // Support platforms that do not provide Read-Modify-Write 339 // byte-level atomic access. To use, derive PlatformCmpxchg<1> from 340 // this class. 341 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11. 342 struct CmpxchgByteUsingInt; 343 private: 344 345 // Dispatch handler for xchg. Provides type-based validity 346 // checking and limited conversions around calls to the 347 // platform-specific implementation layer provided by 348 // PlatformXchg. 349 template<typename T, typename D, typename Enable = void> 350 struct XchgImpl; 351 352 // Platform-specific implementation of xchg. Support for sizes 353 // of 4, and sizeof(intptr_t) are required. The class is a function 354 // object that must be default constructable, with these requirements: 355 // 356 // - dest is of type T*. 357 // - exchange_value is of type T. 358 // - platform_xchg is an object of type PlatformXchg<sizeof(T)>. 359 // 360 // Then 361 // platform_xchg(exchange_value, dest) 362 // must be a valid expression, returning a result convertible to T. 363 // 364 // A default definition is provided, which declares a function template 365 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const 366 // 367 // For each required size, a platform must either provide an 368 // appropriate definition of that function, or must entirely 369 // specialize the class template for that size. 370 template<size_t byte_size> struct PlatformXchg; 371 372 // Support for platforms that implement some variants of xchg 373 // using a (typically out of line) non-template helper function. 374 // The generic arguments passed to PlatformXchg need to be 375 // translated to the appropriate type for the helper function, the 376 // helper invoked on the translated arguments, and the result 377 // translated back. Type is the parameter / return type of the 378 // helper function. 379 template<typename Type, typename Fn, typename T> 380 static T xchg_using_helper(Fn fn, 381 T exchange_value, 382 T volatile* dest); 383 }; 384 385 template<typename From, typename To> 386 struct Atomic::IsPointerConvertible<From*, To*> : AllStatic { 387 // Determine whether From* is implicitly convertible to To*, using 388 // the "sizeof trick". 389 typedef char yes; 390 typedef char (&no)[2]; 391 392 static yes test(To*); 393 static no test(...); 394 static From* test_value; 395 396 static const bool value = (sizeof(yes) == sizeof(test(test_value))); 397 }; 398 399 // Handle load for pointer, integral and enum types. 400 template<typename T, typename PlatformOp> 401 struct Atomic::LoadImpl< 402 T, 403 PlatformOp, 404 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value || IsPointer<T>::value>::type> 405 VALUE_OBJ_CLASS_SPEC 406 { 407 T operator()(T const volatile* dest) const { 408 // Forward to the platform handler for the size of T. 409 return PlatformOp()(dest); 410 } 411 }; 412 413 // Handle load for types that have a translator. 414 // 415 // All the involved types must be identical. 416 // 417 // This translates the original call into a call on the decayed 418 // arguments, and returns the recovered result of that translated 419 // call. 420 template<typename T, typename PlatformOp> 421 struct Atomic::LoadImpl< 422 T, 423 PlatformOp, 424 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 425 VALUE_OBJ_CLASS_SPEC 426 { 427 T operator()(T const volatile* dest) const { 428 typedef PrimitiveConversions::Translate<T> Translator; 429 typedef typename Translator::Decayed Decayed; 430 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 431 Decayed result = PlatformOp()(reinterpret_cast<Decayed const volatile*>(dest)); 432 return Translator::recover(result); 433 } 434 }; 435 436 // Default implementation of atomic load if a specific platform 437 // does not provide a specialization for a certain size class. 438 // For increased safety, the default implementation only allows 439 // load types that are pointer sized or smaller. If a platform still 440 // supports wide atomics, then it has to use specialization 441 // of Atomic::PlatformLoad for that wider size class. 442 template<size_t byte_size> 443 struct Atomic::PlatformLoad VALUE_OBJ_CLASS_SPEC { 444 template<typename T> 445 T operator()(T const volatile* dest) const { 446 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization 447 return *dest; 448 } 449 }; 450 451 // Handle store for integral and enum types. 452 // 453 // All the involved types must be identical. 454 template<typename T, typename PlatformOp> 455 struct Atomic::StoreImpl< 456 T, T, 457 PlatformOp, 458 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 459 VALUE_OBJ_CLASS_SPEC 460 { 461 void operator()(T new_value, T volatile* dest) const { 462 // Forward to the platform handler for the size of T. 463 PlatformOp()(new_value, dest); 464 } 465 }; 466 467 // Handle store for pointer types. 468 // 469 // The new_value must be implicitly convertible to the 470 // destination's type; it must be type-correct to store the 471 // new_value in the destination. 472 template<typename T, typename D, typename PlatformOp> 473 struct Atomic::StoreImpl< 474 T*, D*, 475 PlatformOp, 476 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type> 477 VALUE_OBJ_CLASS_SPEC 478 { 479 void operator()(T* new_value, D* volatile* dest) const { 480 // Allow derived to base conversion, and adding cv-qualifiers. 481 D* value = new_value; 482 PlatformOp()(value, dest); 483 } 484 }; 485 486 // Handle store for types that have a translator. 487 // 488 // All the involved types must be identical. 489 // 490 // This translates the original call into a call on the decayed 491 // arguments. 492 template<typename T, typename PlatformOp> 493 struct Atomic::StoreImpl< 494 T, T, 495 PlatformOp, 496 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 497 VALUE_OBJ_CLASS_SPEC 498 { 499 void operator()(T new_value, T volatile* dest) const { 500 typedef PrimitiveConversions::Translate<T> Translator; 501 typedef typename Translator::Decayed Decayed; 502 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 503 PlatformOp()(Translator::decay(new_value), 504 reinterpret_cast<Decayed volatile*>(dest)); 505 } 506 }; 507 508 // Default implementation of atomic store if a specific platform 509 // does not provide a specialization for a certain size class. 510 // For increased safety, the default implementation only allows 511 // storing types that are pointer sized or smaller. If a platform still 512 // supports wide atomics, then it has to use specialization 513 // of Atomic::PlatformStore for that wider size class. 514 template<size_t byte_size> 515 struct Atomic::PlatformStore VALUE_OBJ_CLASS_SPEC { 516 template<typename T> 517 void operator()(T new_value, 518 T volatile* dest) const { 519 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization 520 (void)const_cast<T&>(*dest = new_value); 521 } 522 }; 523 524 // Define FetchAndAdd and AddAndFetch helper classes before including 525 // platform file, which may use these as base classes, requiring they 526 // be complete. 527 528 template<typename Derived> 529 struct Atomic::FetchAndAdd VALUE_OBJ_CLASS_SPEC { 530 template<typename I, typename D> 531 D operator()(I add_value, D volatile* dest) const; 532 }; 533 534 template<typename Derived> 535 struct Atomic::AddAndFetch VALUE_OBJ_CLASS_SPEC { 536 template<typename I, typename D> 537 D operator()(I add_value, D volatile* dest) const; 538 }; 539 540 template<typename D> 541 inline void Atomic::inc(D volatile* dest) { 542 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value); 543 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I; 544 Atomic::add(I(1), dest); 545 } 546 547 template<typename D> 548 inline void Atomic::dec(D volatile* dest) { 549 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value); 550 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I; 551 // Assumes two's complement integer representation. 552 #pragma warning(suppress: 4146) 553 Atomic::add(I(-1), dest); 554 } 555 556 // Define the class before including platform file, which may specialize 557 // the operator definition. No generic definition of specializations 558 // of the operator template are provided, nor are there any generic 559 // specializations of the class. The platform file is responsible for 560 // providing those. 561 template<size_t byte_size> 562 struct Atomic::PlatformCmpxchg VALUE_OBJ_CLASS_SPEC { 563 template<typename T> 564 T operator()(T exchange_value, 565 T volatile* dest, 566 T compare_value, 567 cmpxchg_memory_order order) const; 568 }; 569 570 // Define the class before including platform file, which may use this 571 // as a base class, requiring it be complete. The definition is later 572 // in this file, near the other definitions related to cmpxchg. 573 struct Atomic::CmpxchgByteUsingInt VALUE_OBJ_CLASS_SPEC { 574 template<typename T> 575 T operator()(T exchange_value, 576 T volatile* dest, 577 T compare_value, 578 cmpxchg_memory_order order) const; 579 }; 580 581 // Define the class before including platform file, which may specialize 582 // the operator definition. No generic definition of specializations 583 // of the operator template are provided, nor are there any generic 584 // specializations of the class. The platform file is responsible for 585 // providing those. 586 template<size_t byte_size> 587 struct Atomic::PlatformXchg VALUE_OBJ_CLASS_SPEC { 588 template<typename T> 589 T operator()(T exchange_value, 590 T volatile* dest) const; 591 }; 592 593 // platform specific in-line definitions - must come before shared definitions 594 595 #include OS_CPU_HEADER(atomic) 596 597 // shared in-line definitions 598 599 // size_t casts... 600 #if (SIZE_MAX != UINTPTR_MAX) 601 #error size_t is not WORD_SIZE, interesting platform, but missing implementation here 602 #endif 603 604 template<typename T> 605 inline T Atomic::load(const volatile T* dest) { 606 return LoadImpl<T, PlatformLoad<sizeof(T)> >()(dest); 607 } 608 609 template<typename T, typename D> 610 inline void Atomic::store(T store_value, volatile D* dest) { 611 StoreImpl<T, D, PlatformStore<sizeof(D)> >()(store_value, dest); 612 } 613 614 template<typename I, typename D> 615 inline D Atomic::add(I add_value, D volatile* dest) { 616 return AddImpl<I, D>()(add_value, dest); 617 } 618 619 template<typename I, typename D> 620 struct Atomic::AddImpl< 621 I, D, 622 typename EnableIf<IsIntegral<I>::value && 623 IsIntegral<D>::value && 624 (sizeof(I) <= sizeof(D)) && 625 (IsSigned<I>::value == IsSigned<D>::value)>::type> 626 VALUE_OBJ_CLASS_SPEC 627 { 628 D operator()(I add_value, D volatile* dest) const { 629 D addend = add_value; 630 return PlatformAdd<sizeof(D)>()(addend, dest); 631 } 632 }; 633 634 template<typename I, typename P> 635 struct Atomic::AddImpl< 636 I, P*, 637 typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type> 638 VALUE_OBJ_CLASS_SPEC 639 { 640 P* operator()(I add_value, P* volatile* dest) const { 641 STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*)); 642 STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*)); 643 typedef typename Conditional<IsSigned<I>::value, 644 intptr_t, 645 uintptr_t>::type CI; 646 CI addend = add_value; 647 return PlatformAdd<sizeof(P*)>()(addend, dest); 648 } 649 }; 650 651 // Most platforms do not support atomic add on a 2-byte value. However, 652 // if the value occupies the most significant 16 bits of an aligned 32-bit 653 // word, then we can do this with an atomic add of (add_value << 16) 654 // to the 32-bit word. 655 // 656 // The least significant parts of this 32-bit word will never be affected, even 657 // in case of overflow/underflow. 658 // 659 // Use the ATOMIC_SHORT_PAIR macro (see macros.hpp) to get the desired alignment. 660 template<> 661 struct Atomic::AddImpl<jshort, jshort> VALUE_OBJ_CLASS_SPEC { 662 jshort operator()(jshort add_value, jshort volatile* dest) const { 663 #ifdef VM_LITTLE_ENDIAN 664 assert((intx(dest) & 0x03) == 0x02, "wrong alignment"); 665 jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest-1)); 666 #else 667 assert((intx(dest) & 0x03) == 0x00, "wrong alignment"); 668 jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest)); 669 #endif 670 return (jshort)(new_value >> 16); // preserves sign 671 } 672 }; 673 674 template<typename Derived> 675 template<typename I, typename D> 676 inline D Atomic::FetchAndAdd<Derived>::operator()(I add_value, D volatile* dest) const { 677 I addend = add_value; 678 // If D is a pointer type P*, scale by sizeof(P). 679 if (IsPointer<D>::value) { 680 addend *= sizeof(typename RemovePointer<D>::type); 681 } 682 D old = static_cast<const Derived*>(this)->fetch_and_add(addend, dest); 683 return old + add_value; 684 } 685 686 template<typename Derived> 687 template<typename I, typename D> 688 inline D Atomic::AddAndFetch<Derived>::operator()(I add_value, D volatile* dest) const { 689 // If D is a pointer type P*, scale by sizeof(P). 690 if (IsPointer<D>::value) { 691 add_value *= sizeof(typename RemovePointer<D>::type); 692 } 693 return static_cast<const Derived*>(this)->add_and_fetch(add_value, dest); 694 } 695 696 template<typename Type, typename Fn, typename I, typename D> 697 inline D Atomic::add_using_helper(Fn fn, I add_value, D volatile* dest) { 698 return PrimitiveConversions::cast<D>( 699 fn(PrimitiveConversions::cast<Type>(add_value), 700 reinterpret_cast<Type volatile*>(dest))); 701 } 702 703 template<typename T, typename D, typename U> 704 inline D Atomic::cmpxchg(T exchange_value, 705 D volatile* dest, 706 U compare_value, 707 cmpxchg_memory_order order) { 708 return CmpxchgImpl<T, D, U>()(exchange_value, dest, compare_value, order); 709 } 710 711 template<typename T, typename D> 712 inline bool Atomic::replace_if_null(T* value, D* volatile* dest, 713 cmpxchg_memory_order order) { 714 // Presently using a trivial implementation in terms of cmpxchg. 715 // Consider adding platform support, to permit the use of compiler 716 // intrinsics like gcc's __sync_bool_compare_and_swap. 717 D* expected_null = NULL; 718 return expected_null == cmpxchg(value, dest, expected_null, order); 719 } 720 721 // Handle cmpxchg for integral and enum types. 722 // 723 // All the involved types must be identical. 724 template<typename T> 725 struct Atomic::CmpxchgImpl< 726 T, T, T, 727 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 728 VALUE_OBJ_CLASS_SPEC 729 { 730 T operator()(T exchange_value, T volatile* dest, T compare_value, 731 cmpxchg_memory_order order) const { 732 // Forward to the platform handler for the size of T. 733 return PlatformCmpxchg<sizeof(T)>()(exchange_value, 734 dest, 735 compare_value, 736 order); 737 } 738 }; 739 740 // Handle cmpxchg for pointer types. 741 // 742 // The destination's type and the compare_value type must be the same, 743 // ignoring cv-qualifiers; we don't care about the cv-qualifiers of 744 // the compare_value. 745 // 746 // The exchange_value must be implicitly convertible to the 747 // destination's type; it must be type-correct to store the 748 // exchange_value in the destination. 749 template<typename T, typename D, typename U> 750 struct Atomic::CmpxchgImpl< 751 T*, D*, U*, 752 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value && 753 IsSame<typename RemoveCV<D>::type, 754 typename RemoveCV<U>::type>::value>::type> 755 VALUE_OBJ_CLASS_SPEC 756 { 757 D* operator()(T* exchange_value, D* volatile* dest, U* compare_value, 758 cmpxchg_memory_order order) const { 759 // Allow derived to base conversion, and adding cv-qualifiers. 760 D* new_value = exchange_value; 761 // Don't care what the CV qualifiers for compare_value are, 762 // but we need to match D* when calling platform support. 763 D* old_value = const_cast<D*>(compare_value); 764 return PlatformCmpxchg<sizeof(D*)>()(new_value, dest, old_value, order); 765 } 766 }; 767 768 // Handle cmpxchg for types that have a translator. 769 // 770 // All the involved types must be identical. 771 // 772 // This translates the original call into a call on the decayed 773 // arguments, and returns the recovered result of that translated 774 // call. 775 template<typename T> 776 struct Atomic::CmpxchgImpl< 777 T, T, T, 778 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 779 VALUE_OBJ_CLASS_SPEC 780 { 781 T operator()(T exchange_value, T volatile* dest, T compare_value, 782 cmpxchg_memory_order order) const { 783 typedef PrimitiveConversions::Translate<T> Translator; 784 typedef typename Translator::Decayed Decayed; 785 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 786 return Translator::recover( 787 cmpxchg(Translator::decay(exchange_value), 788 reinterpret_cast<Decayed volatile*>(dest), 789 Translator::decay(compare_value), 790 order)); 791 } 792 }; 793 794 template<typename Type, typename Fn, typename T> 795 inline T Atomic::cmpxchg_using_helper(Fn fn, 796 T exchange_value, 797 T volatile* dest, 798 T compare_value) { 799 STATIC_ASSERT(sizeof(Type) == sizeof(T)); 800 return PrimitiveConversions::cast<T>( 801 fn(PrimitiveConversions::cast<Type>(exchange_value), 802 reinterpret_cast<Type volatile*>(dest), 803 PrimitiveConversions::cast<Type>(compare_value))); 804 } 805 806 template<typename T> 807 inline T Atomic::CmpxchgByteUsingInt::operator()(T exchange_value, 808 T volatile* dest, 809 T compare_value, 810 cmpxchg_memory_order order) const { 811 STATIC_ASSERT(sizeof(T) == sizeof(uint8_t)); 812 uint8_t canon_exchange_value = exchange_value; 813 uint8_t canon_compare_value = compare_value; 814 volatile uint32_t* aligned_dest 815 = reinterpret_cast<volatile uint32_t*>(align_down(dest, sizeof(uint32_t))); 816 size_t offset = pointer_delta(dest, aligned_dest, 1); 817 uint32_t cur = *aligned_dest; 818 uint8_t* cur_as_bytes = reinterpret_cast<uint8_t*>(&cur); 819 820 // current value may not be what we are looking for, so force it 821 // to that value so the initial cmpxchg will fail if it is different 822 cur_as_bytes[offset] = canon_compare_value; 823 824 // always execute a real cmpxchg so that we get the required memory 825 // barriers even on initial failure 826 do { 827 // value to swap in matches current value ... 828 uint32_t new_value = cur; 829 // ... except for the one jbyte we want to update 830 reinterpret_cast<uint8_t*>(&new_value)[offset] = canon_exchange_value; 831 832 uint32_t res = cmpxchg(new_value, aligned_dest, cur, order); 833 if (res == cur) break; // success 834 835 // at least one byte in the int changed value, so update 836 // our view of the current int 837 cur = res; 838 // if our byte is still as cur we loop and try again 839 } while (cur_as_bytes[offset] == canon_compare_value); 840 841 return PrimitiveConversions::cast<T>(cur_as_bytes[offset]); 842 } 843 844 // Handle xchg for integral and enum types. 845 // 846 // All the involved types must be identical. 847 template<typename T> 848 struct Atomic::XchgImpl< 849 T, T, 850 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 851 VALUE_OBJ_CLASS_SPEC 852 { 853 T operator()(T exchange_value, T volatile* dest) const { 854 // Forward to the platform handler for the size of T. 855 return PlatformXchg<sizeof(T)>()(exchange_value, dest); 856 } 857 }; 858 859 // Handle xchg for pointer types. 860 // 861 // The exchange_value must be implicitly convertible to the 862 // destination's type; it must be type-correct to store the 863 // exchange_value in the destination. 864 template<typename T, typename D> 865 struct Atomic::XchgImpl< 866 T*, D*, 867 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type> 868 VALUE_OBJ_CLASS_SPEC 869 { 870 D* operator()(T* exchange_value, D* volatile* dest) const { 871 // Allow derived to base conversion, and adding cv-qualifiers. 872 D* new_value = exchange_value; 873 return PlatformXchg<sizeof(D*)>()(new_value, dest); 874 } 875 }; 876 877 // Handle xchg for types that have a translator. 878 // 879 // All the involved types must be identical. 880 // 881 // This translates the original call into a call on the decayed 882 // arguments, and returns the recovered result of that translated 883 // call. 884 template<typename T> 885 struct Atomic::XchgImpl< 886 T, T, 887 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 888 VALUE_OBJ_CLASS_SPEC 889 { 890 T operator()(T exchange_value, T volatile* dest) const { 891 typedef PrimitiveConversions::Translate<T> Translator; 892 typedef typename Translator::Decayed Decayed; 893 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 894 return Translator::recover( 895 xchg(Translator::decay(exchange_value), 896 reinterpret_cast<Decayed volatile*>(dest))); 897 } 898 }; 899 900 template<typename Type, typename Fn, typename T> 901 inline T Atomic::xchg_using_helper(Fn fn, 902 T exchange_value, 903 T volatile* dest) { 904 STATIC_ASSERT(sizeof(Type) == sizeof(T)); 905 return PrimitiveConversions::cast<T>( 906 fn(PrimitiveConversions::cast<Type>(exchange_value), 907 reinterpret_cast<Type volatile*>(dest))); 908 } 909 910 template<typename T, typename D> 911 inline D Atomic::xchg(T exchange_value, volatile D* dest) { 912 return XchgImpl<T, D>()(exchange_value, dest); 913 } 914 915 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP