1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  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   // See comment above about using jlong atomics on 32-bit platforms
  68   // The type T must be either a pointer type convertible to or equal
  69   // to D, an integral/enum type equal to D, or a type equal to D that
  70   // is primitive convertible using PrimitiveConversions.
  71   template<typename T, typename D>
  72   inline static void store(T store_value, volatile D* dest);
  73 
  74   inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest) {
  75     Atomic::store(store_value, dest);
  76   }
  77 
  78   inline static void store_ptr(void*    store_value, volatile void*     dest) {
  79     Atomic::store(store_value, reinterpret_cast<void* volatile*>(dest));
  80   }
  81 
  82   // Atomically load from a location
  83   // See comment above about using jlong atomics on 32-bit platforms
  84   // The type T must be either a pointer type, an integral/enum type,
  85   // or a type that is primitive convertible using PrimitiveConversions.
  86   template<typename T>
  87   inline static T load(const volatile T* dest);
  88 
  89   // Atomically add to a location. Returns updated value. add*() provide:
  90   // <fence> add-value-to-dest <membar StoreLoad|StoreStore>
  91 
  92   template<typename I, typename D>
  93   inline static D add(I add_value, D volatile* dest);
  94 
  95   inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest) {
  96     return add(add_value, dest);
  97   }
  98 
  99   inline static void* add_ptr(intptr_t add_value, volatile void* dest) {
 100     return add(add_value, reinterpret_cast<char* volatile*>(dest));
 101   }
 102 
 103   // Atomically increment location. inc() provide:
 104   // <fence> increment-dest <membar StoreLoad|StoreStore>
 105   // The type D may be either a pointer type, or an integral
 106   // type. If it is a pointer type, then the increment is
 107   // scaled to the size of the type pointed to by the pointer.
 108   template<typename D>
 109   inline static void inc(D volatile* dest);
 110 
 111   // Atomically decrement a location. dec() provide:
 112   // <fence> decrement-dest <membar StoreLoad|StoreStore>
 113   // The type D may be either a pointer type, or an integral
 114   // type. If it is a pointer type, then the decrement is
 115   // scaled to the size of the type pointed to by the pointer.
 116   template<typename D>
 117   inline static void dec(D volatile* dest);
 118 
 119   // Performs atomic exchange of *dest with exchange_value. Returns old
 120   // prior value of *dest. xchg*() provide:
 121   // <fence> exchange-value-with-dest <membar StoreLoad|StoreStore>
 122   // The type T must be either a pointer type convertible to or equal
 123   // to D, an integral/enum type equal to D, or a type equal to D that
 124   // is primitive convertible using PrimitiveConversions.
 125   template<typename T, typename D>
 126   inline static D xchg(T exchange_value, volatile D* dest);
 127 
 128   inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest) {
 129     return xchg(exchange_value, dest);
 130   }
 131 
 132   inline static void*    xchg_ptr(void*    exchange_value, volatile void*     dest) {
 133     return xchg(exchange_value, reinterpret_cast<void* volatile*>(dest));
 134   }
 135 
 136   // Performs atomic compare of *dest and compare_value, and exchanges
 137   // *dest with exchange_value if the comparison succeeded. Returns prior
 138   // value of *dest. cmpxchg*() provide:
 139   // <fence> compare-and-exchange <membar StoreLoad|StoreStore>
 140 
 141   template<typename T, typename D, typename U>
 142   inline static D cmpxchg(T exchange_value,
 143                           D volatile* dest,
 144                           U compare_value,
 145                           cmpxchg_memory_order order = memory_order_conservative);
 146 
 147   // Performs atomic compare of *dest and NULL, and replaces *dest
 148   // with exchange_value if the comparison succeeded.  Returns true if
 149   // the comparison succeeded and the exchange occurred.  This is
 150   // often used as part of lazy initialization, as a lock-free
 151   // alternative to the Double-Checked Locking Pattern.
 152   template<typename T, typename D>
 153   inline static bool replace_if_null(T* value, D* volatile* dest,
 154                                      cmpxchg_memory_order order = memory_order_conservative);
 155 
 156   inline static intptr_t cmpxchg_ptr(intptr_t exchange_value,
 157                                      volatile intptr_t* dest,
 158                                      intptr_t compare_value,
 159                                      cmpxchg_memory_order order = memory_order_conservative) {
 160     return cmpxchg(exchange_value, dest, compare_value, order);
 161   }
 162 
 163   inline static void* cmpxchg_ptr(void* exchange_value,
 164                                   volatile void* dest,
 165                                   void* compare_value,
 166                                   cmpxchg_memory_order order = memory_order_conservative) {
 167     return cmpxchg(exchange_value,
 168                    reinterpret_cast<void* volatile*>(dest),
 169                    compare_value,
 170                    order);
 171   }
 172 
 173 private:
 174   // Test whether From is implicitly convertible to To.
 175   // From and To must be pointer types.
 176   // Note: Provides the limited subset of C++11 std::is_convertible
 177   // that is needed here.
 178   template<typename From, typename To> struct IsPointerConvertible;
 179 
 180   // Dispatch handler for store.  Provides type-based validity
 181   // checking and limited conversions around calls to the platform-
 182   // specific implementation layer provided by PlatformOp.
 183   template<typename T, typename D, typename PlatformOp, typename Enable = void>
 184   struct StoreImpl;
 185 
 186   // Platform-specific implementation of store.  Support for sizes
 187   // of 1, 2, 4, and (if different) pointer size bytes are required.
 188   // The class is a function object that must be default constructable,
 189   // with these requirements:
 190   //
 191   // either:
 192   // - dest is of type D*, an integral, enum or pointer type.
 193   // - new_value are of type T, an integral, enum or pointer type D or
 194   //   pointer type convertible to D.
 195   // or:
 196   // - T and D are the same and are primitive convertible using PrimitiveConversions
 197   // and either way:
 198   // - platform_store is an object of type PlatformStore<sizeof(T)>.
 199   //
 200   // Then
 201   //   platform_store(new_value, dest)
 202   // must be a valid expression.
 203   //
 204   // The default implementation is a volatile store. If a platform
 205   // requires more for e.g. 64 bit stores, a specialization is required
 206   template<size_t byte_size> struct PlatformStore;
 207 
 208   // Dispatch handler for load.  Provides type-based validity
 209   // checking and limited conversions around calls to the platform-
 210   // specific implementation layer provided by PlatformOp.
 211   template<typename T, typename PlatformOp, typename Enable = void>
 212   struct LoadImpl;
 213 
 214   // Platform-specific implementation of load. Support for sizes of
 215   // 1, 2, 4 bytes and (if different) pointer size bytes are required.
 216   // The class is a function object that must be default
 217   // constructable, with these requirements:
 218   //
 219   // - dest is of type T*, an integral, enum or pointer type, or
 220   //   T is convertible to a primitive type using PrimitiveConversions
 221   // - platform_load is an object of type PlatformLoad<sizeof(T)>.
 222   //
 223   // Then
 224   //   platform_load(src)
 225   // must be a valid expression, returning a result convertible to T.
 226   //
 227   // The default implementation is a volatile load. If a platform
 228   // requires more for e.g. 64 bit loads, a specialization is required
 229   template<size_t byte_size> struct PlatformLoad;
 230 
 231   // Dispatch handler for add.  Provides type-based validity checking
 232   // and limited conversions around calls to the platform-specific
 233   // implementation layer provided by PlatformAdd.
 234   template<typename I, typename D, typename Enable = void>
 235   struct AddImpl;
 236 
 237   // Platform-specific implementation of add.  Support for sizes of 4
 238   // bytes and (if different) pointer size bytes are required.  The
 239   // class is a function object that must be default constructable,
 240   // with these requirements:
 241   //
 242   // - dest is of type D*, an integral or pointer type.
 243   // - add_value is of type I, an integral type.
 244   // - sizeof(I) == sizeof(D).
 245   // - if D is an integral type, I == D.
 246   // - platform_add is an object of type PlatformAdd<sizeof(D)>.
 247   //
 248   // Then
 249   //   platform_add(add_value, dest)
 250   // must be a valid expression, returning a result convertible to D.
 251   //
 252   // No definition is provided; all platforms must explicitly define
 253   // this class and any needed specializations.
 254   template<size_t byte_size> struct PlatformAdd;
 255 
 256   // Helper base classes for defining PlatformAdd.  To use, define
 257   // PlatformAdd or a specialization that derives from one of these,
 258   // and include in the PlatformAdd definition the support function
 259   // (described below) required by the base class.
 260   //
 261   // These classes implement the required function object protocol for
 262   // PlatformAdd, using a support function template provided by the
 263   // derived class.  Let add_value (of type I) and dest (of type D) be
 264   // the arguments the object is called with.  If D is a pointer type
 265   // P*, then let addend (of type I) be add_value * sizeof(P);
 266   // otherwise, addend is add_value.
 267   //
 268   // FetchAndAdd requires the derived class to provide
 269   //   fetch_and_add(addend, dest)
 270   // atomically adding addend to the value of dest, and returning the
 271   // old value.
 272   //
 273   // AddAndFetch requires the derived class to provide
 274   //   add_and_fetch(addend, dest)
 275   // atomically adding addend to the value of dest, and returning the
 276   // new value.
 277   //
 278   // When D is a pointer type P*, both fetch_and_add and add_and_fetch
 279   // treat it as if it were a uintptr_t; they do not perform any
 280   // scaling of the addend, as that has already been done by the
 281   // caller.
 282 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
 283   template<typename Derived> struct FetchAndAdd;
 284   template<typename Derived> struct AddAndFetch;
 285 private:
 286 
 287   // Support for platforms that implement some variants of add using a
 288   // (typically out of line) non-template helper function.  The
 289   // generic arguments passed to PlatformAdd need to be translated to
 290   // the appropriate type for the helper function, the helper function
 291   // invoked on the translated arguments, and the result translated
 292   // back.  Type is the parameter / return type of the helper
 293   // function.  No scaling of add_value is performed when D is a pointer
 294   // type, so this function can be used to implement the support function
 295   // required by AddAndFetch.
 296   template<typename Type, typename Fn, typename I, typename D>
 297   static D add_using_helper(Fn fn, I add_value, D volatile* dest);
 298 
 299   // Dispatch handler for cmpxchg.  Provides type-based validity
 300   // checking and limited conversions around calls to the
 301   // platform-specific implementation layer provided by
 302   // PlatformCmpxchg.
 303   template<typename T, typename D, typename U, typename Enable = void>
 304   struct CmpxchgImpl;
 305 
 306   // Platform-specific implementation of cmpxchg.  Support for sizes
 307   // of 1, 4, and 8 are required.  The class is a function object that
 308   // must be default constructable, with these requirements:
 309   //
 310   // - dest is of type T*.
 311   // - exchange_value and compare_value are of type T.
 312   // - order is of type cmpxchg_memory_order.
 313   // - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>.
 314   //
 315   // Then
 316   //   platform_cmpxchg(exchange_value, dest, compare_value, order)
 317   // must be a valid expression, returning a result convertible to T.
 318   //
 319   // A default definition is provided, which declares a function template
 320   //   T operator()(T, T volatile*, T, cmpxchg_memory_order) const
 321   //
 322   // For each required size, a platform must either provide an
 323   // appropriate definition of that function, or must entirely
 324   // specialize the class template for that size.
 325   template<size_t byte_size> struct PlatformCmpxchg;
 326 
 327   // Support for platforms that implement some variants of cmpxchg
 328   // using a (typically out of line) non-template helper function.
 329   // The generic arguments passed to PlatformCmpxchg need to be
 330   // translated to the appropriate type for the helper function, the
 331   // helper invoked on the translated arguments, and the result
 332   // translated back.  Type is the parameter / return type of the
 333   // helper function.
 334   template<typename Type, typename Fn, typename T>
 335   static T cmpxchg_using_helper(Fn fn,
 336                                 T exchange_value,
 337                                 T volatile* dest,
 338                                 T compare_value);
 339 
 340   // Support platforms that do not provide Read-Modify-Write
 341   // byte-level atomic access. To use, derive PlatformCmpxchg<1> from
 342   // this class.
 343 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
 344   struct CmpxchgByteUsingInt;
 345 private:
 346 
 347   // Dispatch handler for xchg.  Provides type-based validity
 348   // checking and limited conversions around calls to the
 349   // platform-specific implementation layer provided by
 350   // PlatformXchg.
 351   template<typename T, typename D, typename Enable = void>
 352   struct XchgImpl;
 353 
 354   // Platform-specific implementation of xchg.  Support for sizes
 355   // of 4, and sizeof(intptr_t) are required.  The class is a function
 356   // object that must be default constructable, with these requirements:
 357   //
 358   // - dest is of type T*.
 359   // - exchange_value is of type T.
 360   // - platform_xchg is an object of type PlatformXchg<sizeof(T)>.
 361   //
 362   // Then
 363   //   platform_xchg(exchange_value, dest)
 364   // must be a valid expression, returning a result convertible to T.
 365   //
 366   // A default definition is provided, which declares a function template
 367   //   T operator()(T, T volatile*, T, cmpxchg_memory_order) const
 368   //
 369   // For each required size, a platform must either provide an
 370   // appropriate definition of that function, or must entirely
 371   // specialize the class template for that size.
 372   template<size_t byte_size> struct PlatformXchg;
 373 
 374   // Support for platforms that implement some variants of xchg
 375   // using a (typically out of line) non-template helper function.
 376   // The generic arguments passed to PlatformXchg need to be
 377   // translated to the appropriate type for the helper function, the
 378   // helper invoked on the translated arguments, and the result
 379   // translated back.  Type is the parameter / return type of the
 380   // helper function.
 381   template<typename Type, typename Fn, typename T>
 382   static T xchg_using_helper(Fn fn,
 383                              T exchange_value,
 384                              T volatile* dest);
 385 };
 386 
 387 template<typename From, typename To>
 388 struct Atomic::IsPointerConvertible<From*, To*> : AllStatic {
 389   // Determine whether From* is implicitly convertible to To*, using
 390   // the "sizeof trick".
 391   typedef char yes;
 392   typedef char (&no)[2];
 393 
 394   static yes test(To*);
 395   static no test(...);
 396   static From* test_value;
 397 
 398   static const bool value = (sizeof(yes) == sizeof(test(test_value)));
 399 };
 400 
 401 // Handle load for pointer, integral and enum types.
 402 template<typename T, typename PlatformOp>
 403 struct Atomic::LoadImpl<
 404   T,
 405   PlatformOp,
 406   typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value || IsPointer<T>::value>::type>
 407   VALUE_OBJ_CLASS_SPEC
 408 {
 409   T operator()(T const volatile* dest) const {
 410     // Forward to the platform handler for the size of T.
 411     return PlatformOp()(dest);
 412   }
 413 };
 414 
 415 // Handle load for types that have a translator.
 416 //
 417 // All the involved types must be identical.
 418 //
 419 // This translates the original call into a call on the decayed
 420 // arguments, and returns the recovered result of that translated
 421 // call.
 422 template<typename T, typename PlatformOp>
 423 struct Atomic::LoadImpl<
 424   T,
 425   PlatformOp,
 426   typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
 427   VALUE_OBJ_CLASS_SPEC
 428 {
 429   T operator()(T const volatile* dest) const {
 430     typedef PrimitiveConversions::Translate<T> Translator;
 431     typedef typename Translator::Decayed Decayed;
 432     STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
 433     Decayed result = PlatformOp()(reinterpret_cast<Decayed const volatile*>(dest));
 434     return Translator::recover(result);
 435   }
 436 };
 437 
 438 // Default implementation of atomic load if a specific platform
 439 // does not provide a specialization for a certain size class.
 440 // For increased safety, the default implementation only allows
 441 // load types that are pointer sized or smaller. If a platform still
 442 // supports wide atomics, then it has to use specialization
 443 // of Atomic::PlatformLoad for that wider size class.
 444 template<size_t byte_size>
 445 struct Atomic::PlatformLoad VALUE_OBJ_CLASS_SPEC {
 446   template<typename T>
 447   T operator()(T const volatile* dest) const {
 448     STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
 449     return *dest;
 450   }
 451 };
 452 
 453 // Handle store for integral and enum types.
 454 //
 455 // All the involved types must be identical.
 456 template<typename T, typename PlatformOp>
 457 struct Atomic::StoreImpl<
 458   T, T,
 459   PlatformOp,
 460   typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
 461   VALUE_OBJ_CLASS_SPEC
 462 {
 463   void operator()(T new_value, T volatile* dest) const {
 464     // Forward to the platform handler for the size of T.
 465     PlatformOp()(new_value, dest);
 466   }
 467 };
 468 
 469 // Handle store for pointer types.
 470 //
 471 // The new_value must be implicitly convertible to the
 472 // destination's type; it must be type-correct to store the
 473 // new_value in the destination.
 474 template<typename T, typename D, typename PlatformOp>
 475 struct Atomic::StoreImpl<
 476   T*, D*,
 477   PlatformOp,
 478   typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
 479   VALUE_OBJ_CLASS_SPEC
 480 {
 481   void operator()(T* new_value, D* volatile* dest) const {
 482     // Allow derived to base conversion, and adding cv-qualifiers.
 483     D* value = new_value;
 484     PlatformOp()(value, dest);
 485   }
 486 };
 487 
 488 // Handle store for types that have a translator.
 489 //
 490 // All the involved types must be identical.
 491 //
 492 // This translates the original call into a call on the decayed
 493 // arguments.
 494 template<typename T, typename PlatformOp>
 495 struct Atomic::StoreImpl<
 496   T, T,
 497   PlatformOp,
 498   typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
 499   VALUE_OBJ_CLASS_SPEC
 500 {
 501   void operator()(T new_value, T volatile* dest) const {
 502     typedef PrimitiveConversions::Translate<T> Translator;
 503     typedef typename Translator::Decayed Decayed;
 504     STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
 505     PlatformOp()(Translator::decay(new_value),
 506                  reinterpret_cast<Decayed volatile*>(dest));
 507   }
 508 };
 509 
 510 // Default implementation of atomic store if a specific platform
 511 // does not provide a specialization for a certain size class.
 512 // For increased safety, the default implementation only allows
 513 // storing types that are pointer sized or smaller. If a platform still
 514 // supports wide atomics, then it has to use specialization
 515 // of Atomic::PlatformStore for that wider size class.
 516 template<size_t byte_size>
 517 struct Atomic::PlatformStore VALUE_OBJ_CLASS_SPEC {
 518   template<typename T>
 519   void operator()(T new_value,
 520                   T volatile* dest) const {
 521     STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
 522     (void)const_cast<T&>(*dest = new_value);
 523   }
 524 };
 525 
 526 // Define FetchAndAdd and AddAndFetch helper classes before including
 527 // platform file, which may use these as base classes, requiring they
 528 // be complete.
 529 
 530 template<typename Derived>
 531 struct Atomic::FetchAndAdd VALUE_OBJ_CLASS_SPEC {
 532   template<typename I, typename D>
 533   D operator()(I add_value, D volatile* dest) const;
 534 };
 535 
 536 template<typename Derived>
 537 struct Atomic::AddAndFetch VALUE_OBJ_CLASS_SPEC {
 538   template<typename I, typename D>
 539   D operator()(I add_value, D volatile* dest) const;
 540 };
 541 
 542 template<typename D>
 543 inline void Atomic::inc(D volatile* dest) {
 544   STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
 545   typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
 546   Atomic::add(I(1), dest);
 547 }
 548 
 549 template<typename D>
 550 inline void Atomic::dec(D volatile* dest) {
 551   STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
 552   typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
 553   // Assumes two's complement integer representation.
 554   #pragma warning(suppress: 4146)
 555   Atomic::add(I(-1), dest);
 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::PlatformCmpxchg VALUE_OBJ_CLASS_SPEC {
 565   template<typename T>
 566   T operator()(T exchange_value,
 567                T volatile* dest,
 568                T compare_value,
 569                cmpxchg_memory_order order) const;
 570 };
 571 
 572 // Define the class before including platform file, which may use this
 573 // as a base class, requiring it be complete.  The definition is later
 574 // in this file, near the other definitions related to cmpxchg.
 575 struct Atomic::CmpxchgByteUsingInt VALUE_OBJ_CLASS_SPEC {
 576   template<typename T>
 577   T operator()(T exchange_value,
 578                T volatile* dest,
 579                T compare_value,
 580                cmpxchg_memory_order order) const;
 581 };
 582 
 583 // Define the class before including platform file, which may specialize
 584 // the operator definition.  No generic definition of specializations
 585 // of the operator template are provided, nor are there any generic
 586 // specializations of the class.  The platform file is responsible for
 587 // providing those.
 588 template<size_t byte_size>
 589 struct Atomic::PlatformXchg VALUE_OBJ_CLASS_SPEC {
 590   template<typename T>
 591   T operator()(T exchange_value,
 592                T volatile* dest) const;
 593 };
 594 
 595 // platform specific in-line definitions - must come before shared definitions
 596 
 597 #include OS_CPU_HEADER(atomic)
 598 
 599 // shared in-line definitions
 600 
 601 // size_t casts...
 602 #if (SIZE_MAX != UINTPTR_MAX)
 603 #error size_t is not WORD_SIZE, interesting platform, but missing implementation here
 604 #endif
 605 
 606 template<typename T>
 607 inline T Atomic::load(const volatile T* dest) {
 608   return LoadImpl<T, PlatformLoad<sizeof(T)> >()(dest);
 609 }
 610 
 611 template<typename T, typename D>
 612 inline void Atomic::store(T store_value, volatile D* dest) {
 613   StoreImpl<T, D, PlatformStore<sizeof(D)> >()(store_value, dest);
 614 }
 615 
 616 template<typename I, typename D>
 617 inline D Atomic::add(I add_value, D volatile* dest) {
 618   return AddImpl<I, D>()(add_value, dest);
 619 }
 620 
 621 template<typename I, typename D>
 622 struct Atomic::AddImpl<
 623   I, D,
 624   typename EnableIf<IsIntegral<I>::value &&
 625                     IsIntegral<D>::value &&
 626                     (sizeof(I) <= sizeof(D)) &&
 627                     (IsSigned<I>::value == IsSigned<D>::value)>::type>
 628   VALUE_OBJ_CLASS_SPEC
 629 {
 630   D operator()(I add_value, D volatile* dest) const {
 631     D addend = add_value;
 632     return PlatformAdd<sizeof(D)>()(addend, dest);
 633   }
 634 };
 635 
 636 template<typename I, typename P>
 637 struct Atomic::AddImpl<
 638   I, P*,
 639   typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type>
 640   VALUE_OBJ_CLASS_SPEC
 641 {
 642   P* operator()(I add_value, P* volatile* dest) const {
 643     STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*));
 644     STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*));
 645     typedef typename Conditional<IsSigned<I>::value,
 646                                  intptr_t,
 647                                  uintptr_t>::type CI;
 648     CI addend = add_value;
 649     return PlatformAdd<sizeof(P*)>()(addend, dest);
 650   }
 651 };
 652 
 653 // Most platforms do not support atomic add on a 2-byte value. However,
 654 // if the value occupies the most significant 16 bits of an aligned 32-bit
 655 // word, then we can do this with an atomic add of (add_value << 16)
 656 // to the 32-bit word.
 657 //
 658 // The least significant parts of this 32-bit word will never be affected, even
 659 // in case of overflow/underflow.
 660 //
 661 // Use the ATOMIC_SHORT_PAIR macro (see macros.hpp) to get the desired alignment.
 662 template<>
 663 struct Atomic::AddImpl<jshort, jshort> VALUE_OBJ_CLASS_SPEC {
 664   jshort operator()(jshort add_value, jshort volatile* dest) const {
 665 #ifdef VM_LITTLE_ENDIAN
 666     assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
 667     jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest-1));
 668 #else
 669     assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
 670     jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest));
 671 #endif
 672     return (jshort)(new_value >> 16); // preserves sign
 673   }
 674 };
 675 
 676 template<typename Derived>
 677 template<typename I, typename D>
 678 inline D Atomic::FetchAndAdd<Derived>::operator()(I add_value, D volatile* dest) const {
 679   I addend = add_value;
 680   // If D is a pointer type P*, scale by sizeof(P).
 681   if (IsPointer<D>::value) {
 682     addend *= sizeof(typename RemovePointer<D>::type);
 683   }
 684   D old = static_cast<const Derived*>(this)->fetch_and_add(addend, dest);
 685   return old + add_value;
 686 }
 687 
 688 template<typename Derived>
 689 template<typename I, typename D>
 690 inline D Atomic::AddAndFetch<Derived>::operator()(I add_value, D volatile* dest) const {
 691   // If D is a pointer type P*, scale by sizeof(P).
 692   if (IsPointer<D>::value) {
 693     add_value *= sizeof(typename RemovePointer<D>::type);
 694   }
 695   return static_cast<const Derived*>(this)->add_and_fetch(add_value, dest);
 696 }
 697 
 698 template<typename Type, typename Fn, typename I, typename D>
 699 inline D Atomic::add_using_helper(Fn fn, I add_value, D volatile* dest) {
 700   return PrimitiveConversions::cast<D>(
 701     fn(PrimitiveConversions::cast<Type>(add_value),
 702        reinterpret_cast<Type volatile*>(dest)));
 703 }
 704 
 705 template<typename T, typename D, typename U>
 706 inline D Atomic::cmpxchg(T exchange_value,
 707                          D volatile* dest,
 708                          U compare_value,
 709                          cmpxchg_memory_order order) {
 710   return CmpxchgImpl<T, D, U>()(exchange_value, dest, compare_value, order);
 711 }
 712 
 713 template<typename T, typename D>
 714 inline bool Atomic::replace_if_null(T* value, D* volatile* dest,
 715                                     cmpxchg_memory_order order) {
 716   // Presently using a trivial implementation in terms of cmpxchg.
 717   // Consider adding platform support, to permit the use of compiler
 718   // intrinsics like gcc's __sync_bool_compare_and_swap.
 719   D* expected_null = NULL;
 720   return expected_null == cmpxchg(value, dest, expected_null, order);
 721 }
 722 
 723 // Handle cmpxchg for integral and enum types.
 724 //
 725 // All the involved types must be identical.
 726 template<typename T>
 727 struct Atomic::CmpxchgImpl<
 728   T, T, T,
 729   typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
 730   VALUE_OBJ_CLASS_SPEC
 731 {
 732   T operator()(T exchange_value, T volatile* dest, T compare_value,
 733                cmpxchg_memory_order order) const {
 734     // Forward to the platform handler for the size of T.
 735     return PlatformCmpxchg<sizeof(T)>()(exchange_value,
 736                                         dest,
 737                                         compare_value,
 738                                         order);
 739   }
 740 };
 741 
 742 // Handle cmpxchg for pointer types.
 743 //
 744 // The destination's type and the compare_value type must be the same,
 745 // ignoring cv-qualifiers; we don't care about the cv-qualifiers of
 746 // the compare_value.
 747 //
 748 // The exchange_value must be implicitly convertible to the
 749 // destination's type; it must be type-correct to store the
 750 // exchange_value in the destination.
 751 template<typename T, typename D, typename U>
 752 struct Atomic::CmpxchgImpl<
 753   T*, D*, U*,
 754   typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value &&
 755                     IsSame<typename RemoveCV<D>::type,
 756                            typename RemoveCV<U>::type>::value>::type>
 757   VALUE_OBJ_CLASS_SPEC
 758 {
 759   D* operator()(T* exchange_value, D* volatile* dest, U* compare_value,
 760                cmpxchg_memory_order order) const {
 761     // Allow derived to base conversion, and adding cv-qualifiers.
 762     D* new_value = exchange_value;
 763     // Don't care what the CV qualifiers for compare_value are,
 764     // but we need to match D* when calling platform support.
 765     D* old_value = const_cast<D*>(compare_value);
 766     return PlatformCmpxchg<sizeof(D*)>()(new_value, dest, old_value, order);
 767   }
 768 };
 769 
 770 // Handle cmpxchg for types that have a translator.
 771 //
 772 // All the involved types must be identical.
 773 //
 774 // This translates the original call into a call on the decayed
 775 // arguments, and returns the recovered result of that translated
 776 // call.
 777 template<typename T>
 778 struct Atomic::CmpxchgImpl<
 779   T, T, T,
 780   typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
 781   VALUE_OBJ_CLASS_SPEC
 782 {
 783   T operator()(T exchange_value, T volatile* dest, T compare_value,
 784                cmpxchg_memory_order order) const {
 785     typedef PrimitiveConversions::Translate<T> Translator;
 786     typedef typename Translator::Decayed Decayed;
 787     STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
 788     return Translator::recover(
 789       cmpxchg(Translator::decay(exchange_value),
 790               reinterpret_cast<Decayed volatile*>(dest),
 791               Translator::decay(compare_value),
 792               order));
 793   }
 794 };
 795 
 796 template<typename Type, typename Fn, typename T>
 797 inline T Atomic::cmpxchg_using_helper(Fn fn,
 798                                       T exchange_value,
 799                                       T volatile* dest,
 800                                       T compare_value) {
 801   STATIC_ASSERT(sizeof(Type) == sizeof(T));
 802   return PrimitiveConversions::cast<T>(
 803     fn(PrimitiveConversions::cast<Type>(exchange_value),
 804        reinterpret_cast<Type volatile*>(dest),
 805        PrimitiveConversions::cast<Type>(compare_value)));
 806 }
 807 
 808 template<typename T>
 809 inline T Atomic::CmpxchgByteUsingInt::operator()(T exchange_value,
 810                                                  T volatile* dest,
 811                                                  T compare_value,
 812                                                  cmpxchg_memory_order order) const {
 813   STATIC_ASSERT(sizeof(T) == sizeof(uint8_t));
 814   uint8_t canon_exchange_value = exchange_value;
 815   uint8_t canon_compare_value = compare_value;
 816   volatile uint32_t* aligned_dest
 817     = reinterpret_cast<volatile uint32_t*>(align_down(dest, sizeof(uint32_t)));
 818   size_t offset = pointer_delta(dest, aligned_dest, 1);
 819   uint32_t cur = *aligned_dest;
 820   uint8_t* cur_as_bytes = reinterpret_cast<uint8_t*>(&cur);
 821 
 822   // current value may not be what we are looking for, so force it
 823   // to that value so the initial cmpxchg will fail if it is different
 824   cur_as_bytes[offset] = canon_compare_value;
 825 
 826   // always execute a real cmpxchg so that we get the required memory
 827   // barriers even on initial failure
 828   do {
 829     // value to swap in matches current value ...
 830     uint32_t new_value = cur;
 831     // ... except for the one jbyte we want to update
 832     reinterpret_cast<uint8_t*>(&new_value)[offset] = canon_exchange_value;
 833 
 834     uint32_t res = cmpxchg(new_value, aligned_dest, cur, order);
 835     if (res == cur) break;      // success
 836 
 837     // at least one byte in the int changed value, so update
 838     // our view of the current int
 839     cur = res;
 840     // if our byte is still as cur we loop and try again
 841   } while (cur_as_bytes[offset] == canon_compare_value);
 842 
 843   return PrimitiveConversions::cast<T>(cur_as_bytes[offset]);
 844 }
 845 
 846 // Handle xchg for integral and enum types.
 847 //
 848 // All the involved types must be identical.
 849 template<typename T>
 850 struct Atomic::XchgImpl<
 851   T, T,
 852   typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
 853   VALUE_OBJ_CLASS_SPEC
 854 {
 855   T operator()(T exchange_value, T volatile* dest) const {
 856     // Forward to the platform handler for the size of T.
 857     return PlatformXchg<sizeof(T)>()(exchange_value, dest);
 858   }
 859 };
 860 
 861 // Handle xchg for pointer types.
 862 //
 863 // The exchange_value must be implicitly convertible to the
 864 // destination's type; it must be type-correct to store the
 865 // exchange_value in the destination.
 866 template<typename T, typename D>
 867 struct Atomic::XchgImpl<
 868   T*, D*,
 869   typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
 870   VALUE_OBJ_CLASS_SPEC
 871 {
 872   D* operator()(T* exchange_value, D* volatile* dest) const {
 873     // Allow derived to base conversion, and adding cv-qualifiers.
 874     D* new_value = exchange_value;
 875     return PlatformXchg<sizeof(D*)>()(new_value, dest);
 876   }
 877 };
 878 
 879 // Handle xchg for types that have a translator.
 880 //
 881 // All the involved types must be identical.
 882 //
 883 // This translates the original call into a call on the decayed
 884 // arguments, and returns the recovered result of that translated
 885 // call.
 886 template<typename T>
 887 struct Atomic::XchgImpl<
 888   T, T,
 889   typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
 890   VALUE_OBJ_CLASS_SPEC
 891 {
 892   T operator()(T exchange_value, T volatile* dest) const {
 893     typedef PrimitiveConversions::Translate<T> Translator;
 894     typedef typename Translator::Decayed Decayed;
 895     STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
 896     return Translator::recover(
 897       xchg(Translator::decay(exchange_value),
 898            reinterpret_cast<Decayed volatile*>(dest)));
 899   }
 900 };
 901 
 902 template<typename Type, typename Fn, typename T>
 903 inline T Atomic::xchg_using_helper(Fn fn,
 904                                    T exchange_value,
 905                                    T volatile* dest) {
 906   STATIC_ASSERT(sizeof(Type) == sizeof(T));
 907   return PrimitiveConversions::cast<T>(
 908     fn(PrimitiveConversions::cast<Type>(exchange_value),
 909        reinterpret_cast<Type volatile*>(dest)));
 910 }
 911 
 912 template<typename T, typename D>
 913 inline D Atomic::xchg(T exchange_value, volatile D* dest) {
 914   return XchgImpl<T, D>()(exchange_value, dest);
 915 }
 916 
 917 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP