1 /* 2 * Copyright (c) 1999, 2018, 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 int64 types are not available on all 32-bit 49 // platforms. If atomic ops on int64 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 // Atomically load from a location 74 // The type T must be either a pointer type, an integral/enum type, 75 // or a type that is primitive convertible using PrimitiveConversions. 76 template<typename T> 77 inline static T load(const volatile T* dest); 78 79 // Atomically add to a location. Returns updated value. add*() provide: 80 // <fence> add-value-to-dest <membar StoreLoad|StoreStore> 81 82 template<typename I, typename D> 83 inline static D add(I add_value, D volatile* dest); 84 85 template<typename I, typename D> 86 inline static D sub(I sub_value, D volatile* dest); 87 88 // Atomically increment location. inc() provide: 89 // <fence> increment-dest <membar StoreLoad|StoreStore> 90 // The type D may be either a pointer type, or an integral 91 // type. If it is a pointer type, then the increment is 92 // scaled to the size of the type pointed to by the pointer. 93 template<typename D> 94 inline static void inc(D volatile* dest); 95 96 // Atomically decrement a location. dec() provide: 97 // <fence> decrement-dest <membar StoreLoad|StoreStore> 98 // The type D may be either a pointer type, or an integral 99 // type. If it is a pointer type, then the decrement is 100 // scaled to the size of the type pointed to by the pointer. 101 template<typename D> 102 inline static void dec(D volatile* dest); 103 104 // Performs atomic exchange of *dest with exchange_value. Returns old 105 // prior value of *dest. xchg*() provide: 106 // <fence> exchange-value-with-dest <membar StoreLoad|StoreStore> 107 // The type T must be either a pointer type convertible to or equal 108 // to D, an integral/enum type equal to D, or a type equal to D that 109 // is primitive convertible using PrimitiveConversions. 110 template<typename T, typename D> 111 inline static D xchg(T exchange_value, volatile D* dest); 112 113 // Performs atomic compare of *dest and compare_value, and exchanges 114 // *dest with exchange_value if the comparison succeeded. Returns prior 115 // value of *dest. cmpxchg*() provide: 116 // <fence> compare-and-exchange <membar StoreLoad|StoreStore> 117 118 template<typename T, typename D, typename U> 119 inline static D cmpxchg(T exchange_value, 120 D volatile* dest, 121 U compare_value, 122 cmpxchg_memory_order order = memory_order_conservative); 123 124 // Performs atomic compare of *dest and NULL, and replaces *dest 125 // with exchange_value if the comparison succeeded. Returns true if 126 // the comparison succeeded and the exchange occurred. This is 127 // often used as part of lazy initialization, as a lock-free 128 // alternative to the Double-Checked Locking Pattern. 129 template<typename T, typename D> 130 inline static bool replace_if_null(T* value, D* volatile* dest, 131 cmpxchg_memory_order order = memory_order_conservative); 132 133 private: 134 WINDOWS_ONLY(public:) // VS2017 warns (C2027) use of undefined type if IsPointerConvertible is declared private 135 // Test whether From is implicitly convertible to To. 136 // From and To must be pointer types. 137 // Note: Provides the limited subset of C++11 std::is_convertible 138 // that is needed here. 139 template<typename From, typename To> struct IsPointerConvertible; 140 141 protected: 142 // Dispatch handler for store. Provides type-based validity 143 // checking and limited conversions around calls to the platform- 144 // specific implementation layer provided by PlatformOp. 145 template<typename T, typename D, typename PlatformOp, typename Enable = void> 146 struct StoreImpl; 147 148 // Platform-specific implementation of store. Support for sizes 149 // of 1, 2, 4, and (if different) pointer size bytes are required. 150 // The class is a function object that must be default constructable, 151 // with these requirements: 152 // 153 // either: 154 // - dest is of type D*, an integral, enum or pointer type. 155 // - new_value are of type T, an integral, enum or pointer type D or 156 // pointer type convertible to D. 157 // or: 158 // - T and D are the same and are primitive convertible using PrimitiveConversions 159 // and either way: 160 // - platform_store is an object of type PlatformStore<sizeof(T)>. 161 // 162 // Then 163 // platform_store(new_value, dest) 164 // must be a valid expression. 165 // 166 // The default implementation is a volatile store. If a platform 167 // requires more for e.g. 64 bit stores, a specialization is required 168 template<size_t byte_size> struct PlatformStore; 169 170 // Dispatch handler for load. Provides type-based validity 171 // checking and limited conversions around calls to the platform- 172 // specific implementation layer provided by PlatformOp. 173 template<typename T, typename PlatformOp, typename Enable = void> 174 struct LoadImpl; 175 176 // Platform-specific implementation of load. Support for sizes of 177 // 1, 2, 4 bytes and (if different) pointer size bytes are required. 178 // The class is a function object that must be default 179 // constructable, with these requirements: 180 // 181 // - dest is of type T*, an integral, enum or pointer type, or 182 // T is convertible to a primitive type using PrimitiveConversions 183 // - platform_load is an object of type PlatformLoad<sizeof(T)>. 184 // 185 // Then 186 // platform_load(src) 187 // must be a valid expression, returning a result convertible to T. 188 // 189 // The default implementation is a volatile load. If a platform 190 // requires more for e.g. 64 bit loads, a specialization is required 191 template<size_t byte_size> struct PlatformLoad; 192 193 private: 194 // Dispatch handler for add. Provides type-based validity checking 195 // and limited conversions around calls to the platform-specific 196 // implementation layer provided by PlatformAdd. 197 template<typename I, typename D, typename Enable = void> 198 struct AddImpl; 199 200 // Platform-specific implementation of add. Support for sizes of 4 201 // bytes and (if different) pointer size bytes are required. The 202 // class is a function object that must be default constructable, 203 // with these requirements: 204 // 205 // - dest is of type D*, an integral or pointer type. 206 // - add_value is of type I, an integral type. 207 // - sizeof(I) == sizeof(D). 208 // - if D is an integral type, I == D. 209 // - platform_add is an object of type PlatformAdd<sizeof(D)>. 210 // 211 // Then 212 // platform_add(add_value, dest) 213 // must be a valid expression, returning a result convertible to D. 214 // 215 // No definition is provided; all platforms must explicitly define 216 // this class and any needed specializations. 217 template<size_t byte_size> struct PlatformAdd; 218 219 // Helper base classes for defining PlatformAdd. To use, define 220 // PlatformAdd or a specialization that derives from one of these, 221 // and include in the PlatformAdd definition the support function 222 // (described below) required by the base class. 223 // 224 // These classes implement the required function object protocol for 225 // PlatformAdd, using a support function template provided by the 226 // derived class. Let add_value (of type I) and dest (of type D) be 227 // the arguments the object is called with. If D is a pointer type 228 // P*, then let addend (of type I) be add_value * sizeof(P); 229 // otherwise, addend is add_value. 230 // 231 // FetchAndAdd requires the derived class to provide 232 // fetch_and_add(addend, dest) 233 // atomically adding addend to the value of dest, and returning the 234 // old value. 235 // 236 // AddAndFetch requires the derived class to provide 237 // add_and_fetch(addend, dest) 238 // atomically adding addend to the value of dest, and returning the 239 // new value. 240 // 241 // When D is a pointer type P*, both fetch_and_add and add_and_fetch 242 // treat it as if it were a uintptr_t; they do not perform any 243 // scaling of the addend, as that has already been done by the 244 // caller. 245 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11. 246 template<typename Derived> struct FetchAndAdd; 247 template<typename Derived> struct AddAndFetch; 248 private: 249 250 // Support for platforms that implement some variants of add using a 251 // (typically out of line) non-template helper function. The 252 // generic arguments passed to PlatformAdd need to be translated to 253 // the appropriate type for the helper function, the helper function 254 // invoked on the translated arguments, and the result translated 255 // back. Type is the parameter / return type of the helper 256 // function. No scaling of add_value is performed when D is a pointer 257 // type, so this function can be used to implement the support function 258 // required by AddAndFetch. 259 template<typename Type, typename Fn, typename I, typename D> 260 static D add_using_helper(Fn fn, I add_value, D volatile* dest); 261 262 // Dispatch handler for cmpxchg. Provides type-based validity 263 // checking and limited conversions around calls to the 264 // platform-specific implementation layer provided by 265 // PlatformCmpxchg. 266 template<typename T, typename D, typename U, typename Enable = void> 267 struct CmpxchgImpl; 268 269 // Platform-specific implementation of cmpxchg. Support for sizes 270 // of 1, 4, and 8 are required. The class is a function object that 271 // must be default constructable, with these requirements: 272 // 273 // - dest is of type T*. 274 // - exchange_value and compare_value are of type T. 275 // - order is of type cmpxchg_memory_order. 276 // - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>. 277 // 278 // Then 279 // platform_cmpxchg(exchange_value, dest, compare_value, order) 280 // must be a valid expression, returning a result convertible to T. 281 // 282 // A default definition is provided, which declares a function template 283 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const 284 // 285 // For each required size, a platform must either provide an 286 // appropriate definition of that function, or must entirely 287 // specialize the class template for that size. 288 template<size_t byte_size> struct PlatformCmpxchg; 289 290 // Support for platforms that implement some variants of cmpxchg 291 // using a (typically out of line) non-template helper function. 292 // The generic arguments passed to PlatformCmpxchg need to be 293 // translated to the appropriate type for the helper function, the 294 // helper invoked on the translated arguments, and the result 295 // translated back. Type is the parameter / return type of the 296 // helper function. 297 template<typename Type, typename Fn, typename T> 298 static T cmpxchg_using_helper(Fn fn, 299 T exchange_value, 300 T volatile* dest, 301 T compare_value); 302 303 // Support platforms that do not provide Read-Modify-Write 304 // byte-level atomic access. To use, derive PlatformCmpxchg<1> from 305 // this class. 306 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11. 307 struct CmpxchgByteUsingInt; 308 private: 309 310 // Dispatch handler for xchg. Provides type-based validity 311 // checking and limited conversions around calls to the 312 // platform-specific implementation layer provided by 313 // PlatformXchg. 314 template<typename T, typename D, typename Enable = void> 315 struct XchgImpl; 316 317 // Platform-specific implementation of xchg. Support for sizes 318 // of 4, and sizeof(intptr_t) are required. The class is a function 319 // object that must be default constructable, with these requirements: 320 // 321 // - dest is of type T*. 322 // - exchange_value is of type T. 323 // - platform_xchg is an object of type PlatformXchg<sizeof(T)>. 324 // 325 // Then 326 // platform_xchg(exchange_value, dest) 327 // must be a valid expression, returning a result convertible to T. 328 // 329 // A default definition is provided, which declares a function template 330 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const 331 // 332 // For each required size, a platform must either provide an 333 // appropriate definition of that function, or must entirely 334 // specialize the class template for that size. 335 template<size_t byte_size> struct PlatformXchg; 336 337 // Support for platforms that implement some variants of xchg 338 // using a (typically out of line) non-template helper function. 339 // The generic arguments passed to PlatformXchg need to be 340 // translated to the appropriate type for the helper function, the 341 // helper invoked on the translated arguments, and the result 342 // translated back. Type is the parameter / return type of the 343 // helper function. 344 template<typename Type, typename Fn, typename T> 345 static T xchg_using_helper(Fn fn, 346 T exchange_value, 347 T volatile* dest); 348 }; 349 350 template<typename From, typename To> 351 struct Atomic::IsPointerConvertible<From*, To*> : AllStatic { 352 // Determine whether From* is implicitly convertible to To*, using 353 // the "sizeof trick". 354 typedef char yes; 355 typedef char (&no)[2]; 356 357 static yes test(To*); 358 static no test(...); 359 static From* test_value; 360 361 static const bool value = (sizeof(yes) == sizeof(test(test_value))); 362 }; 363 364 // Handle load for pointer, integral and enum types. 365 template<typename T, typename PlatformOp> 366 struct Atomic::LoadImpl< 367 T, 368 PlatformOp, 369 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value || IsPointer<T>::value>::type> 370 { 371 T operator()(T const volatile* dest) const { 372 // Forward to the platform handler for the size of T. 373 return PlatformOp()(dest); 374 } 375 }; 376 377 // Handle load for types that have a translator. 378 // 379 // All the involved types must be identical. 380 // 381 // This translates the original call into a call on the decayed 382 // arguments, and returns the recovered result of that translated 383 // call. 384 template<typename T, typename PlatformOp> 385 struct Atomic::LoadImpl< 386 T, 387 PlatformOp, 388 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 389 { 390 T operator()(T const volatile* dest) const { 391 typedef PrimitiveConversions::Translate<T> Translator; 392 typedef typename Translator::Decayed Decayed; 393 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 394 Decayed result = PlatformOp()(reinterpret_cast<Decayed const volatile*>(dest)); 395 return Translator::recover(result); 396 } 397 }; 398 399 // Default implementation of atomic load if a specific platform 400 // does not provide a specialization for a certain size class. 401 // For increased safety, the default implementation only allows 402 // load types that are pointer sized or smaller. If a platform still 403 // supports wide atomics, then it has to use specialization 404 // of Atomic::PlatformLoad for that wider size class. 405 template<size_t byte_size> 406 struct Atomic::PlatformLoad { 407 template<typename T> 408 T operator()(T const volatile* dest) const { 409 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization 410 return *dest; 411 } 412 }; 413 414 // Handle store for integral and enum types. 415 // 416 // All the involved types must be identical. 417 template<typename T, typename PlatformOp> 418 struct Atomic::StoreImpl< 419 T, T, 420 PlatformOp, 421 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 422 { 423 void operator()(T new_value, T volatile* dest) const { 424 // Forward to the platform handler for the size of T. 425 PlatformOp()(new_value, dest); 426 } 427 }; 428 429 // Handle store for pointer types. 430 // 431 // The new_value must be implicitly convertible to the 432 // destination's type; it must be type-correct to store the 433 // new_value in the destination. 434 template<typename T, typename D, typename PlatformOp> 435 struct Atomic::StoreImpl< 436 T*, D*, 437 PlatformOp, 438 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type> 439 { 440 void operator()(T* new_value, D* volatile* dest) const { 441 // Allow derived to base conversion, and adding cv-qualifiers. 442 D* value = new_value; 443 PlatformOp()(value, dest); 444 } 445 }; 446 447 // Handle store for types that have a translator. 448 // 449 // All the involved types must be identical. 450 // 451 // This translates the original call into a call on the decayed 452 // arguments. 453 template<typename T, typename PlatformOp> 454 struct Atomic::StoreImpl< 455 T, T, 456 PlatformOp, 457 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 458 { 459 void operator()(T new_value, T volatile* dest) const { 460 typedef PrimitiveConversions::Translate<T> Translator; 461 typedef typename Translator::Decayed Decayed; 462 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 463 PlatformOp()(Translator::decay(new_value), 464 reinterpret_cast<Decayed volatile*>(dest)); 465 } 466 }; 467 468 // Default implementation of atomic store if a specific platform 469 // does not provide a specialization for a certain size class. 470 // For increased safety, the default implementation only allows 471 // storing types that are pointer sized or smaller. If a platform still 472 // supports wide atomics, then it has to use specialization 473 // of Atomic::PlatformStore for that wider size class. 474 template<size_t byte_size> 475 struct Atomic::PlatformStore { 476 template<typename T> 477 void operator()(T new_value, 478 T volatile* dest) const { 479 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization 480 (void)const_cast<T&>(*dest = new_value); 481 } 482 }; 483 484 // Define FetchAndAdd and AddAndFetch helper classes before including 485 // platform file, which may use these as base classes, requiring they 486 // be complete. 487 488 template<typename Derived> 489 struct Atomic::FetchAndAdd { 490 template<typename I, typename D> 491 D operator()(I add_value, D volatile* dest) const; 492 }; 493 494 template<typename Derived> 495 struct Atomic::AddAndFetch { 496 template<typename I, typename D> 497 D operator()(I add_value, D volatile* dest) const; 498 }; 499 500 template<typename D> 501 inline void Atomic::inc(D volatile* dest) { 502 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value); 503 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I; 504 Atomic::add(I(1), dest); 505 } 506 507 template<typename D> 508 inline void Atomic::dec(D volatile* dest) { 509 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value); 510 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I; 511 // Assumes two's complement integer representation. 512 #pragma warning(suppress: 4146) 513 Atomic::add(I(-1), dest); 514 } 515 516 template<typename I, typename D> 517 inline D Atomic::sub(I sub_value, D volatile* dest) { 518 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value); 519 STATIC_ASSERT(IsIntegral<I>::value); 520 // If D is a pointer type, use [u]intptr_t as the addend type, 521 // matching signedness of I. Otherwise, use D as the addend type. 522 typedef typename Conditional<IsSigned<I>::value, intptr_t, uintptr_t>::type PI; 523 typedef typename Conditional<IsPointer<D>::value, PI, D>::type AddendType; 524 // Only allow conversions that can't change the value. 525 STATIC_ASSERT(IsSigned<I>::value == IsSigned<AddendType>::value); 526 STATIC_ASSERT(sizeof(I) <= sizeof(AddendType)); 527 AddendType addend = sub_value; 528 // Assumes two's complement integer representation. 529 #pragma warning(suppress: 4146) // In case AddendType is not signed. 530 return Atomic::add(-addend, dest); 531 } 532 533 // Define the class before including platform file, which may specialize 534 // the operator definition. No generic definition of specializations 535 // of the operator template are provided, nor are there any generic 536 // specializations of the class. The platform file is responsible for 537 // providing those. 538 template<size_t byte_size> 539 struct Atomic::PlatformCmpxchg { 540 template<typename T> 541 T operator()(T exchange_value, 542 T volatile* dest, 543 T compare_value, 544 cmpxchg_memory_order order) const; 545 }; 546 547 // Define the class before including platform file, which may use this 548 // as a base class, requiring it be complete. The definition is later 549 // in this file, near the other definitions related to cmpxchg. 550 struct Atomic::CmpxchgByteUsingInt { 551 template<typename T> 552 T operator()(T exchange_value, 553 T volatile* dest, 554 T compare_value, 555 cmpxchg_memory_order order) const; 556 }; 557 558 // Define the class before including platform file, which may specialize 559 // the operator definition. No generic definition of specializations 560 // of the operator template are provided, nor are there any generic 561 // specializations of the class. The platform file is responsible for 562 // providing those. 563 template<size_t byte_size> 564 struct Atomic::PlatformXchg { 565 template<typename T> 566 T operator()(T exchange_value, 567 T volatile* dest) const; 568 }; 569 570 // platform specific in-line definitions - must come before shared definitions 571 572 #include OS_CPU_HEADER(atomic) 573 574 // shared in-line definitions 575 576 // size_t casts... 577 #if (SIZE_MAX != UINTPTR_MAX) 578 #error size_t is not WORD_SIZE, interesting platform, but missing implementation here 579 #endif 580 581 template<typename T> 582 inline T Atomic::load(const volatile T* dest) { 583 return LoadImpl<T, PlatformLoad<sizeof(T)> >()(dest); 584 } 585 586 template<typename T, typename D> 587 inline void Atomic::store(T store_value, volatile D* dest) { 588 StoreImpl<T, D, PlatformStore<sizeof(D)> >()(store_value, dest); 589 } 590 591 template<typename I, typename D> 592 inline D Atomic::add(I add_value, D volatile* dest) { 593 return AddImpl<I, D>()(add_value, dest); 594 } 595 596 template<typename I, typename D> 597 struct Atomic::AddImpl< 598 I, D, 599 typename EnableIf<IsIntegral<I>::value && 600 IsIntegral<D>::value && 601 (sizeof(I) <= sizeof(D)) && 602 (IsSigned<I>::value == IsSigned<D>::value)>::type> 603 { 604 D operator()(I add_value, D volatile* dest) const { 605 D addend = add_value; 606 return PlatformAdd<sizeof(D)>()(addend, dest); 607 } 608 }; 609 610 template<typename I, typename P> 611 struct Atomic::AddImpl< 612 I, P*, 613 typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type> 614 { 615 P* operator()(I add_value, P* volatile* dest) const { 616 STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*)); 617 STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*)); 618 typedef typename Conditional<IsSigned<I>::value, 619 intptr_t, 620 uintptr_t>::type CI; 621 CI addend = add_value; 622 return PlatformAdd<sizeof(P*)>()(addend, dest); 623 } 624 }; 625 626 // Most platforms do not support atomic add on a 2-byte value. However, 627 // if the value occupies the most significant 16 bits of an aligned 32-bit 628 // word, then we can do this with an atomic add of (add_value << 16) 629 // to the 32-bit word. 630 // 631 // The least significant parts of this 32-bit word will never be affected, even 632 // in case of overflow/underflow. 633 // 634 // Use the ATOMIC_SHORT_PAIR macro (see macros.hpp) to get the desired alignment. 635 template<> 636 struct Atomic::AddImpl<short, short> { 637 short operator()(short add_value, short volatile* dest) const { 638 #ifdef VM_LITTLE_ENDIAN 639 assert((intx(dest) & 0x03) == 0x02, "wrong alignment"); 640 int new_value = Atomic::add(add_value << 16, (volatile int*)(dest-1)); 641 #else 642 assert((intx(dest) & 0x03) == 0x00, "wrong alignment"); 643 int new_value = Atomic::add(add_value << 16, (volatile int*)(dest)); 644 #endif 645 return (short)(new_value >> 16); // preserves sign 646 } 647 }; 648 649 template<typename Derived> 650 template<typename I, typename D> 651 inline D Atomic::FetchAndAdd<Derived>::operator()(I add_value, D volatile* dest) const { 652 I addend = add_value; 653 // If D is a pointer type P*, scale by sizeof(P). 654 if (IsPointer<D>::value) { 655 addend *= sizeof(typename RemovePointer<D>::type); 656 } 657 D old = static_cast<const Derived*>(this)->fetch_and_add(addend, dest); 658 return old + add_value; 659 } 660 661 template<typename Derived> 662 template<typename I, typename D> 663 inline D Atomic::AddAndFetch<Derived>::operator()(I add_value, D volatile* dest) const { 664 // If D is a pointer type P*, scale by sizeof(P). 665 if (IsPointer<D>::value) { 666 add_value *= sizeof(typename RemovePointer<D>::type); 667 } 668 return static_cast<const Derived*>(this)->add_and_fetch(add_value, dest); 669 } 670 671 template<typename Type, typename Fn, typename I, typename D> 672 inline D Atomic::add_using_helper(Fn fn, I add_value, D volatile* dest) { 673 return PrimitiveConversions::cast<D>( 674 fn(PrimitiveConversions::cast<Type>(add_value), 675 reinterpret_cast<Type volatile*>(dest))); 676 } 677 678 template<typename T, typename D, typename U> 679 inline D Atomic::cmpxchg(T exchange_value, 680 D volatile* dest, 681 U compare_value, 682 cmpxchg_memory_order order) { 683 return CmpxchgImpl<T, D, U>()(exchange_value, dest, compare_value, order); 684 } 685 686 template<typename T, typename D> 687 inline bool Atomic::replace_if_null(T* value, D* volatile* dest, 688 cmpxchg_memory_order order) { 689 // Presently using a trivial implementation in terms of cmpxchg. 690 // Consider adding platform support, to permit the use of compiler 691 // intrinsics like gcc's __sync_bool_compare_and_swap. 692 D* expected_null = NULL; 693 return expected_null == cmpxchg(value, dest, expected_null, order); 694 } 695 696 // Handle cmpxchg for integral and enum types. 697 // 698 // All the involved types must be identical. 699 template<typename T> 700 struct Atomic::CmpxchgImpl< 701 T, T, T, 702 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 703 { 704 T operator()(T exchange_value, T volatile* dest, T compare_value, 705 cmpxchg_memory_order order) const { 706 // Forward to the platform handler for the size of T. 707 return PlatformCmpxchg<sizeof(T)>()(exchange_value, 708 dest, 709 compare_value, 710 order); 711 } 712 }; 713 714 // Handle cmpxchg for pointer types. 715 // 716 // The destination's type and the compare_value type must be the same, 717 // ignoring cv-qualifiers; we don't care about the cv-qualifiers of 718 // the compare_value. 719 // 720 // The exchange_value must be implicitly convertible to the 721 // destination's type; it must be type-correct to store the 722 // exchange_value in the destination. 723 template<typename T, typename D, typename U> 724 struct Atomic::CmpxchgImpl< 725 T*, D*, U*, 726 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value && 727 IsSame<typename RemoveCV<D>::type, 728 typename RemoveCV<U>::type>::value>::type> 729 { 730 D* operator()(T* exchange_value, D* volatile* dest, U* compare_value, 731 cmpxchg_memory_order order) const { 732 // Allow derived to base conversion, and adding cv-qualifiers. 733 D* new_value = exchange_value; 734 // Don't care what the CV qualifiers for compare_value are, 735 // but we need to match D* when calling platform support. 736 D* old_value = const_cast<D*>(compare_value); 737 return PlatformCmpxchg<sizeof(D*)>()(new_value, dest, old_value, order); 738 } 739 }; 740 741 // Handle cmpxchg for types that have a translator. 742 // 743 // All the involved types must be identical. 744 // 745 // This translates the original call into a call on the decayed 746 // arguments, and returns the recovered result of that translated 747 // call. 748 template<typename T> 749 struct Atomic::CmpxchgImpl< 750 T, T, T, 751 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 752 { 753 T operator()(T exchange_value, T volatile* dest, T compare_value, 754 cmpxchg_memory_order order) const { 755 typedef PrimitiveConversions::Translate<T> Translator; 756 typedef typename Translator::Decayed Decayed; 757 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 758 return Translator::recover( 759 cmpxchg(Translator::decay(exchange_value), 760 reinterpret_cast<Decayed volatile*>(dest), 761 Translator::decay(compare_value), 762 order)); 763 } 764 }; 765 766 template<typename Type, typename Fn, typename T> 767 inline T Atomic::cmpxchg_using_helper(Fn fn, 768 T exchange_value, 769 T volatile* dest, 770 T compare_value) { 771 STATIC_ASSERT(sizeof(Type) == sizeof(T)); 772 return PrimitiveConversions::cast<T>( 773 fn(PrimitiveConversions::cast<Type>(exchange_value), 774 reinterpret_cast<Type volatile*>(dest), 775 PrimitiveConversions::cast<Type>(compare_value))); 776 } 777 778 template<typename T> 779 inline T Atomic::CmpxchgByteUsingInt::operator()(T exchange_value, 780 T volatile* dest, 781 T compare_value, 782 cmpxchg_memory_order order) const { 783 STATIC_ASSERT(sizeof(T) == sizeof(uint8_t)); 784 uint8_t canon_exchange_value = exchange_value; 785 uint8_t canon_compare_value = compare_value; 786 volatile uint32_t* aligned_dest 787 = reinterpret_cast<volatile uint32_t*>(align_down(dest, sizeof(uint32_t))); 788 size_t offset = pointer_delta(dest, aligned_dest, 1); 789 uint32_t cur = *aligned_dest; 790 uint8_t* cur_as_bytes = reinterpret_cast<uint8_t*>(&cur); 791 792 // current value may not be what we are looking for, so force it 793 // to that value so the initial cmpxchg will fail if it is different 794 cur_as_bytes[offset] = canon_compare_value; 795 796 // always execute a real cmpxchg so that we get the required memory 797 // barriers even on initial failure 798 do { 799 // value to swap in matches current value ... 800 uint32_t new_value = cur; 801 // ... except for the one byte we want to update 802 reinterpret_cast<uint8_t*>(&new_value)[offset] = canon_exchange_value; 803 804 uint32_t res = cmpxchg(new_value, aligned_dest, cur, order); 805 if (res == cur) break; // success 806 807 // at least one byte in the int changed value, so update 808 // our view of the current int 809 cur = res; 810 // if our byte is still as cur we loop and try again 811 } while (cur_as_bytes[offset] == canon_compare_value); 812 813 return PrimitiveConversions::cast<T>(cur_as_bytes[offset]); 814 } 815 816 // Handle xchg for integral and enum types. 817 // 818 // All the involved types must be identical. 819 template<typename T> 820 struct Atomic::XchgImpl< 821 T, T, 822 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type> 823 { 824 T operator()(T exchange_value, T volatile* dest) const { 825 // Forward to the platform handler for the size of T. 826 return PlatformXchg<sizeof(T)>()(exchange_value, dest); 827 } 828 }; 829 830 // Handle xchg for pointer types. 831 // 832 // The exchange_value must be implicitly convertible to the 833 // destination's type; it must be type-correct to store the 834 // exchange_value in the destination. 835 template<typename T, typename D> 836 struct Atomic::XchgImpl< 837 T*, D*, 838 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type> 839 { 840 D* operator()(T* exchange_value, D* volatile* dest) const { 841 // Allow derived to base conversion, and adding cv-qualifiers. 842 D* new_value = exchange_value; 843 return PlatformXchg<sizeof(D*)>()(new_value, dest); 844 } 845 }; 846 847 // Handle xchg for types that have a translator. 848 // 849 // All the involved types must be identical. 850 // 851 // This translates the original call into a call on the decayed 852 // arguments, and returns the recovered result of that translated 853 // call. 854 template<typename T> 855 struct Atomic::XchgImpl< 856 T, T, 857 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type> 858 { 859 T operator()(T exchange_value, T volatile* dest) const { 860 typedef PrimitiveConversions::Translate<T> Translator; 861 typedef typename Translator::Decayed Decayed; 862 STATIC_ASSERT(sizeof(T) == sizeof(Decayed)); 863 return Translator::recover( 864 xchg(Translator::decay(exchange_value), 865 reinterpret_cast<Decayed volatile*>(dest))); 866 } 867 }; 868 869 template<typename Type, typename Fn, typename T> 870 inline T Atomic::xchg_using_helper(Fn fn, 871 T exchange_value, 872 T volatile* dest) { 873 STATIC_ASSERT(sizeof(Type) == sizeof(T)); 874 return PrimitiveConversions::cast<T>( 875 fn(PrimitiveConversions::cast<Type>(exchange_value), 876 reinterpret_cast<Type volatile*>(dest))); 877 } 878 879 template<typename T, typename D> 880 inline D Atomic::xchg(T exchange_value, volatile D* dest) { 881 return XchgImpl<T, D>()(exchange_value, dest); 882 } 883 884 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP