1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 // 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 // Test whether From is implicitly convertible to To.
135 // From and To must be pointer types.
136 // Note: Provides the limited subset of C++11 std::is_convertible
137 // that is needed here.
138 template<typename From, typename To> struct IsPointerConvertible;
139
140 protected:
141 // Dispatch handler for store. Provides type-based validity
142 // checking and limited conversions around calls to the platform-
143 // specific implementation layer provided by PlatformOp.
144 template<typename T, typename D, typename PlatformOp, typename Enable = void>
145 struct StoreImpl;
146
147 // Platform-specific implementation of store. Support for sizes
148 // of 1, 2, 4, and (if different) pointer size bytes are required.
149 // The class is a function object that must be default constructable,
150 // with these requirements:
151 //
152 // either:
153 // - dest is of type D*, an integral, enum or pointer type.
154 // - new_value are of type T, an integral, enum or pointer type D or
155 // pointer type convertible to D.
156 // or:
157 // - T and D are the same and are primitive convertible using PrimitiveConversions
158 // and either way:
159 // - platform_store is an object of type PlatformStore<sizeof(T)>.
160 //
161 // Then
162 // platform_store(new_value, dest)
163 // must be a valid expression.
164 //
165 // The default implementation is a volatile store. If a platform
166 // requires more for e.g. 64 bit stores, a specialization is required
167 template<size_t byte_size> struct PlatformStore;
168
169 // Dispatch handler for load. Provides type-based validity
170 // checking and limited conversions around calls to the platform-
171 // specific implementation layer provided by PlatformOp.
172 template<typename T, typename PlatformOp, typename Enable = void>
173 struct LoadImpl;
174
175 // Platform-specific implementation of load. Support for sizes of
176 // 1, 2, 4 bytes and (if different) pointer size bytes are required.
177 // The class is a function object that must be default
178 // constructable, with these requirements:
179 //
180 // - dest is of type T*, an integral, enum or pointer type, or
181 // T is convertible to a primitive type using PrimitiveConversions
182 // - platform_load is an object of type PlatformLoad<sizeof(T)>.
183 //
184 // Then
185 // platform_load(src)
186 // must be a valid expression, returning a result convertible to T.
187 //
188 // The default implementation is a volatile load. If a platform
189 // requires more for e.g. 64 bit loads, a specialization is required
190 template<size_t byte_size> struct PlatformLoad;
191
192 private:
193 // Dispatch handler for add. Provides type-based validity checking
194 // and limited conversions around calls to the platform-specific
195 // implementation layer provided by PlatformAdd.
196 template<typename I, typename D, typename Enable = void>
197 struct AddImpl;
198
199 // Platform-specific implementation of add. Support for sizes of 4
200 // bytes and (if different) pointer size bytes are required. The
201 // class is a function object that must be default constructable,
202 // with these requirements:
203 //
204 // - dest is of type D*, an integral or pointer type.
205 // - add_value is of type I, an integral type.
206 // - sizeof(I) == sizeof(D).
207 // - if D is an integral type, I == D.
208 // - platform_add is an object of type PlatformAdd<sizeof(D)>.
209 //
210 // Then
211 // platform_add(add_value, dest)
212 // must be a valid expression, returning a result convertible to D.
213 //
214 // No definition is provided; all platforms must explicitly define
215 // this class and any needed specializations.
216 template<size_t byte_size> struct PlatformAdd;
217
218 // Helper base classes for defining PlatformAdd. To use, define
219 // PlatformAdd or a specialization that derives from one of these,
220 // and include in the PlatformAdd definition the support function
221 // (described below) required by the base class.
222 //
223 // These classes implement the required function object protocol for
224 // PlatformAdd, using a support function template provided by the
225 // derived class. Let add_value (of type I) and dest (of type D) be
226 // the arguments the object is called with. If D is a pointer type
227 // P*, then let addend (of type I) be add_value * sizeof(P);
228 // otherwise, addend is add_value.
229 //
230 // FetchAndAdd requires the derived class to provide
231 // fetch_and_add(addend, dest)
232 // atomically adding addend to the value of dest, and returning the
233 // old value.
234 //
235 // AddAndFetch requires the derived class to provide
236 // add_and_fetch(addend, dest)
237 // atomically adding addend to the value of dest, and returning the
238 // new value.
239 //
240 // When D is a pointer type P*, both fetch_and_add and add_and_fetch
241 // treat it as if it were a uintptr_t; they do not perform any
242 // scaling of the addend, as that has already been done by the
243 // caller.
244 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
245 template<typename Derived> struct FetchAndAdd;
246 template<typename Derived> struct AddAndFetch;
247 private:
248
249 // Support for platforms that implement some variants of add using a
250 // (typically out of line) non-template helper function. The
251 // generic arguments passed to PlatformAdd need to be translated to
252 // the appropriate type for the helper function, the helper function
253 // invoked on the translated arguments, and the result translated
254 // back. Type is the parameter / return type of the helper
255 // function. No scaling of add_value is performed when D is a pointer
256 // type, so this function can be used to implement the support function
257 // required by AddAndFetch.
258 template<typename Type, typename Fn, typename I, typename D>
259 static D add_using_helper(Fn fn, I add_value, D volatile* dest);
260
261 // Dispatch handler for cmpxchg. Provides type-based validity
262 // checking and limited conversions around calls to the
263 // platform-specific implementation layer provided by
264 // PlatformCmpxchg.
265 template<typename T, typename D, typename U, typename Enable = void>
266 struct CmpxchgImpl;
267
268 // Platform-specific implementation of cmpxchg. Support for sizes
269 // of 1, 4, and 8 are required. The class is a function object that
270 // must be default constructable, with these requirements:
271 //
272 // - dest is of type T*.
273 // - exchange_value and compare_value are of type T.
274 // - order is of type cmpxchg_memory_order.
275 // - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>.
276 //
277 // Then
278 // platform_cmpxchg(exchange_value, dest, compare_value, order)
279 // must be a valid expression, returning a result convertible to T.
280 //
281 // A default definition is provided, which declares a function template
282 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const
283 //
284 // For each required size, a platform must either provide an
285 // appropriate definition of that function, or must entirely
286 // specialize the class template for that size.
287 template<size_t byte_size> struct PlatformCmpxchg;
288
289 // Support for platforms that implement some variants of cmpxchg
290 // using a (typically out of line) non-template helper function.
291 // The generic arguments passed to PlatformCmpxchg need to be
292 // translated to the appropriate type for the helper function, the
293 // helper invoked on the translated arguments, and the result
294 // translated back. Type is the parameter / return type of the
295 // helper function.
296 template<typename Type, typename Fn, typename T>
297 static T cmpxchg_using_helper(Fn fn,
298 T exchange_value,
299 T volatile* dest,
300 T compare_value);
301
302 // Support platforms that do not provide Read-Modify-Write
303 // byte-level atomic access. To use, derive PlatformCmpxchg<1> from
304 // this class.
305 public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
306 struct CmpxchgByteUsingInt;
307 private:
308
309 // Dispatch handler for xchg. Provides type-based validity
310 // checking and limited conversions around calls to the
311 // platform-specific implementation layer provided by
312 // PlatformXchg.
313 template<typename T, typename D, typename Enable = void>
314 struct XchgImpl;
315
316 // Platform-specific implementation of xchg. Support for sizes
317 // of 4, and sizeof(intptr_t) are required. The class is a function
318 // object that must be default constructable, with these requirements:
319 //
320 // - dest is of type T*.
321 // - exchange_value is of type T.
322 // - platform_xchg is an object of type PlatformXchg<sizeof(T)>.
323 //
324 // Then
325 // platform_xchg(exchange_value, dest)
326 // must be a valid expression, returning a result convertible to T.
327 //
328 // A default definition is provided, which declares a function template
329 // T operator()(T, T volatile*, T, cmpxchg_memory_order) const
330 //
331 // For each required size, a platform must either provide an
332 // appropriate definition of that function, or must entirely
333 // specialize the class template for that size.
334 template<size_t byte_size> struct PlatformXchg;
335
336 // Support for platforms that implement some variants of xchg
337 // using a (typically out of line) non-template helper function.
338 // The generic arguments passed to PlatformXchg need to be
339 // translated to the appropriate type for the helper function, the
340 // helper invoked on the translated arguments, and the result
341 // translated back. Type is the parameter / return type of the
342 // helper function.
343 template<typename Type, typename Fn, typename T>
344 static T xchg_using_helper(Fn fn,
345 T exchange_value,
346 T volatile* dest);
347 };
348
349 template<typename From, typename To>
350 struct Atomic::IsPointerConvertible<From*, To*> : AllStatic {
351 // Determine whether From* is implicitly convertible to To*, using
352 // the "sizeof trick".
353 typedef char yes;
354 typedef char (&no)[2];
355
356 static yes test(To*);
357 static no test(...);
358 static From* test_value;
359
360 static const bool value = (sizeof(yes) == sizeof(test(test_value)));
361 };
362
363 // Handle load for pointer, integral and enum types.
364 template<typename T, typename PlatformOp>
365 struct Atomic::LoadImpl<
366 T,
367 PlatformOp,
368 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value || IsPointer<T>::value>::type>
369 VALUE_OBJ_CLASS_SPEC
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 VALUE_OBJ_CLASS_SPEC
390 {
391 T operator()(T const volatile* dest) const {
392 typedef PrimitiveConversions::Translate<T> Translator;
393 typedef typename Translator::Decayed Decayed;
394 STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
395 Decayed result = PlatformOp()(reinterpret_cast<Decayed const volatile*>(dest));
396 return Translator::recover(result);
397 }
398 };
399
400 // Default implementation of atomic load if a specific platform
401 // does not provide a specialization for a certain size class.
402 // For increased safety, the default implementation only allows
403 // load types that are pointer sized or smaller. If a platform still
404 // supports wide atomics, then it has to use specialization
405 // of Atomic::PlatformLoad for that wider size class.
406 template<size_t byte_size>
407 struct Atomic::PlatformLoad VALUE_OBJ_CLASS_SPEC {
408 template<typename T>
409 T operator()(T const volatile* dest) const {
410 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
411 return *dest;
412 }
413 };
414
415 // Handle store for integral and enum types.
416 //
417 // All the involved types must be identical.
418 template<typename T, typename PlatformOp>
419 struct Atomic::StoreImpl<
420 T, T,
421 PlatformOp,
422 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
423 VALUE_OBJ_CLASS_SPEC
424 {
425 void operator()(T new_value, T volatile* dest) const {
426 // Forward to the platform handler for the size of T.
427 PlatformOp()(new_value, dest);
428 }
429 };
430
431 // Handle store for pointer types.
432 //
433 // The new_value must be implicitly convertible to the
434 // destination's type; it must be type-correct to store the
435 // new_value in the destination.
436 template<typename T, typename D, typename PlatformOp>
437 struct Atomic::StoreImpl<
438 T*, D*,
439 PlatformOp,
440 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
441 VALUE_OBJ_CLASS_SPEC
442 {
443 void operator()(T* new_value, D* volatile* dest) const {
444 // Allow derived to base conversion, and adding cv-qualifiers.
445 D* value = new_value;
446 PlatformOp()(value, dest);
447 }
448 };
449
450 // Handle store for types that have a translator.
451 //
452 // All the involved types must be identical.
453 //
454 // This translates the original call into a call on the decayed
455 // arguments.
456 template<typename T, typename PlatformOp>
457 struct Atomic::StoreImpl<
458 T, T,
459 PlatformOp,
460 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
461 VALUE_OBJ_CLASS_SPEC
462 {
463 void operator()(T new_value, T volatile* dest) const {
464 typedef PrimitiveConversions::Translate<T> Translator;
465 typedef typename Translator::Decayed Decayed;
466 STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
467 PlatformOp()(Translator::decay(new_value),
468 reinterpret_cast<Decayed volatile*>(dest));
469 }
470 };
471
472 // Default implementation of atomic store if a specific platform
473 // does not provide a specialization for a certain size class.
474 // For increased safety, the default implementation only allows
475 // storing types that are pointer sized or smaller. If a platform still
476 // supports wide atomics, then it has to use specialization
477 // of Atomic::PlatformStore for that wider size class.
478 template<size_t byte_size>
479 struct Atomic::PlatformStore VALUE_OBJ_CLASS_SPEC {
480 template<typename T>
481 void operator()(T new_value,
482 T volatile* dest) const {
483 STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
484 (void)const_cast<T&>(*dest = new_value);
485 }
486 };
487
488 // Define FetchAndAdd and AddAndFetch helper classes before including
489 // platform file, which may use these as base classes, requiring they
490 // be complete.
491
492 template<typename Derived>
493 struct Atomic::FetchAndAdd VALUE_OBJ_CLASS_SPEC {
494 template<typename I, typename D>
495 D operator()(I add_value, D volatile* dest) const;
496 };
497
498 template<typename Derived>
499 struct Atomic::AddAndFetch VALUE_OBJ_CLASS_SPEC {
500 template<typename I, typename D>
501 D operator()(I add_value, D volatile* dest) const;
502 };
503
504 template<typename D>
505 inline void Atomic::inc(D volatile* dest) {
506 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
507 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
508 Atomic::add(I(1), dest);
509 }
510
511 template<typename D>
512 inline void Atomic::dec(D volatile* dest) {
513 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
514 typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
515 // Assumes two's complement integer representation.
516 #pragma warning(suppress: 4146)
517 Atomic::add(I(-1), dest);
518 }
519
520 template<typename I, typename D>
521 inline D Atomic::sub(I sub_value, D volatile* dest) {
522 STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
523 // Assumes two's complement integer representation.
524 #pragma warning(suppress: 4146)
525 return Atomic::add(-sub_value, dest);
526 }
527
528 // Define the class before including platform file, which may specialize
529 // the operator definition. No generic definition of specializations
530 // of the operator template are provided, nor are there any generic
531 // specializations of the class. The platform file is responsible for
532 // providing those.
533 template<size_t byte_size>
534 struct Atomic::PlatformCmpxchg VALUE_OBJ_CLASS_SPEC {
535 template<typename T>
536 T operator()(T exchange_value,
537 T volatile* dest,
538 T compare_value,
539 cmpxchg_memory_order order) const;
540 };
541
542 // Define the class before including platform file, which may use this
543 // as a base class, requiring it be complete. The definition is later
544 // in this file, near the other definitions related to cmpxchg.
545 struct Atomic::CmpxchgByteUsingInt VALUE_OBJ_CLASS_SPEC {
546 template<typename T>
547 T operator()(T exchange_value,
548 T volatile* dest,
549 T compare_value,
550 cmpxchg_memory_order order) const;
551 };
552
553 // Define the class before including platform file, which may specialize
554 // the operator definition. No generic definition of specializations
555 // of the operator template are provided, nor are there any generic
556 // specializations of the class. The platform file is responsible for
557 // providing those.
558 template<size_t byte_size>
559 struct Atomic::PlatformXchg VALUE_OBJ_CLASS_SPEC {
560 template<typename T>
561 T operator()(T exchange_value,
562 T volatile* dest) const;
563 };
564
565 // platform specific in-line definitions - must come before shared definitions
566
567 #include OS_CPU_HEADER(atomic)
568
569 // shared in-line definitions
570
571 // size_t casts...
572 #if (SIZE_MAX != UINTPTR_MAX)
573 #error size_t is not WORD_SIZE, interesting platform, but missing implementation here
574 #endif
575
576 template<typename T>
577 inline T Atomic::load(const volatile T* dest) {
578 return LoadImpl<T, PlatformLoad<sizeof(T)> >()(dest);
579 }
580
581 template<typename T, typename D>
582 inline void Atomic::store(T store_value, volatile D* dest) {
583 StoreImpl<T, D, PlatformStore<sizeof(D)> >()(store_value, dest);
584 }
585
586 template<typename I, typename D>
587 inline D Atomic::add(I add_value, D volatile* dest) {
588 return AddImpl<I, D>()(add_value, dest);
589 }
590
591 template<typename I, typename D>
592 struct Atomic::AddImpl<
593 I, D,
594 typename EnableIf<IsIntegral<I>::value &&
595 IsIntegral<D>::value &&
596 (sizeof(I) <= sizeof(D)) &&
597 (IsSigned<I>::value == IsSigned<D>::value)>::type>
598 VALUE_OBJ_CLASS_SPEC
599 {
600 D operator()(I add_value, D volatile* dest) const {
601 D addend = add_value;
602 return PlatformAdd<sizeof(D)>()(addend, dest);
603 }
604 };
605
606 template<typename I, typename P>
607 struct Atomic::AddImpl<
608 I, P*,
609 typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type>
610 VALUE_OBJ_CLASS_SPEC
611 {
612 P* operator()(I add_value, P* volatile* dest) const {
613 STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*));
614 STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*));
615 typedef typename Conditional<IsSigned<I>::value,
616 intptr_t,
617 uintptr_t>::type CI;
618 CI addend = add_value;
619 return PlatformAdd<sizeof(P*)>()(addend, dest);
620 }
621 };
622
623 // Most platforms do not support atomic add on a 2-byte value. However,
624 // if the value occupies the most significant 16 bits of an aligned 32-bit
625 // word, then we can do this with an atomic add of (add_value << 16)
626 // to the 32-bit word.
627 //
628 // The least significant parts of this 32-bit word will never be affected, even
629 // in case of overflow/underflow.
630 //
631 // Use the ATOMIC_SHORT_PAIR macro (see macros.hpp) to get the desired alignment.
632 template<>
633 struct Atomic::AddImpl<jshort, jshort> VALUE_OBJ_CLASS_SPEC {
634 jshort operator()(jshort add_value, jshort volatile* dest) const {
635 #ifdef VM_LITTLE_ENDIAN
636 assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
637 jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest-1));
638 #else
639 assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
640 jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest));
641 #endif
642 return (jshort)(new_value >> 16); // preserves sign
643 }
644 };
645
646 template<typename Derived>
647 template<typename I, typename D>
648 inline D Atomic::FetchAndAdd<Derived>::operator()(I add_value, D volatile* dest) const {
649 I addend = add_value;
650 // If D is a pointer type P*, scale by sizeof(P).
651 if (IsPointer<D>::value) {
652 addend *= sizeof(typename RemovePointer<D>::type);
653 }
654 D old = static_cast<const Derived*>(this)->fetch_and_add(addend, dest);
655 return old + add_value;
656 }
657
658 template<typename Derived>
659 template<typename I, typename D>
660 inline D Atomic::AddAndFetch<Derived>::operator()(I add_value, D volatile* dest) const {
661 // If D is a pointer type P*, scale by sizeof(P).
662 if (IsPointer<D>::value) {
663 add_value *= sizeof(typename RemovePointer<D>::type);
664 }
665 return static_cast<const Derived*>(this)->add_and_fetch(add_value, dest);
666 }
667
668 template<typename Type, typename Fn, typename I, typename D>
669 inline D Atomic::add_using_helper(Fn fn, I add_value, D volatile* dest) {
670 return PrimitiveConversions::cast<D>(
671 fn(PrimitiveConversions::cast<Type>(add_value),
672 reinterpret_cast<Type volatile*>(dest)));
673 }
674
675 template<typename T, typename D, typename U>
676 inline D Atomic::cmpxchg(T exchange_value,
677 D volatile* dest,
678 U compare_value,
679 cmpxchg_memory_order order) {
680 return CmpxchgImpl<T, D, U>()(exchange_value, dest, compare_value, order);
681 }
682
683 template<typename T, typename D>
684 inline bool Atomic::replace_if_null(T* value, D* volatile* dest,
685 cmpxchg_memory_order order) {
686 // Presently using a trivial implementation in terms of cmpxchg.
687 // Consider adding platform support, to permit the use of compiler
688 // intrinsics like gcc's __sync_bool_compare_and_swap.
689 D* expected_null = NULL;
690 return expected_null == cmpxchg(value, dest, expected_null, order);
691 }
692
693 // Handle cmpxchg for integral and enum types.
694 //
695 // All the involved types must be identical.
696 template<typename T>
697 struct Atomic::CmpxchgImpl<
698 T, T, T,
699 typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
700 VALUE_OBJ_CLASS_SPEC
701 {
702 T operator()(T exchange_value, T volatile* dest, T compare_value,
703 cmpxchg_memory_order order) const {
704 // Forward to the platform handler for the size of T.
705 return PlatformCmpxchg<sizeof(T)>()(exchange_value,
706 dest,
707 compare_value,
708 order);
709 }
710 };
711
712 // Handle cmpxchg for pointer types.
713 //
714 // The destination's type and the compare_value type must be the same,
715 // ignoring cv-qualifiers; we don't care about the cv-qualifiers of
716 // the compare_value.
717 //
718 // The exchange_value must be implicitly convertible to the
719 // destination's type; it must be type-correct to store the
720 // exchange_value in the destination.
721 template<typename T, typename D, typename U>
722 struct Atomic::CmpxchgImpl<
723 T*, D*, U*,
724 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value &&
725 IsSame<typename RemoveCV<D>::type,
726 typename RemoveCV<U>::type>::value>::type>
727 VALUE_OBJ_CLASS_SPEC
728 {
729 D* operator()(T* exchange_value, D* volatile* dest, U* compare_value,
730 cmpxchg_memory_order order) const {
731 // Allow derived to base conversion, and adding cv-qualifiers.
732 D* new_value = exchange_value;
733 // Don't care what the CV qualifiers for compare_value are,
734 // but we need to match D* when calling platform support.
735 D* old_value = const_cast<D*>(compare_value);
736 return PlatformCmpxchg<sizeof(D*)>()(new_value, dest, old_value, order);
737 }
738 };
739
740 // Handle cmpxchg for types that have a translator.
741 //
742 // All the involved types must be identical.
743 //
744 // This translates the original call into a call on the decayed
745 // arguments, and returns the recovered result of that translated
746 // call.
747 template<typename T>
748 struct Atomic::CmpxchgImpl<
749 T, T, T,
750 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
751 VALUE_OBJ_CLASS_SPEC
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 jbyte 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 VALUE_OBJ_CLASS_SPEC
824 {
825 T operator()(T exchange_value, T volatile* dest) const {
826 // Forward to the platform handler for the size of T.
827 return PlatformXchg<sizeof(T)>()(exchange_value, dest);
828 }
829 };
830
831 // Handle xchg for pointer types.
832 //
833 // The exchange_value must be implicitly convertible to the
834 // destination's type; it must be type-correct to store the
835 // exchange_value in the destination.
836 template<typename T, typename D>
837 struct Atomic::XchgImpl<
838 T*, D*,
839 typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
840 VALUE_OBJ_CLASS_SPEC
841 {
842 D* operator()(T* exchange_value, D* volatile* dest) const {
843 // Allow derived to base conversion, and adding cv-qualifiers.
844 D* new_value = exchange_value;
845 return PlatformXchg<sizeof(D*)>()(new_value, dest);
846 }
847 };
848
849 // Handle xchg for types that have a translator.
850 //
851 // All the involved types must be identical.
852 //
853 // This translates the original call into a call on the decayed
854 // arguments, and returns the recovered result of that translated
855 // call.
856 template<typename T>
857 struct Atomic::XchgImpl<
858 T, T,
859 typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
860 VALUE_OBJ_CLASS_SPEC
861 {
862 T operator()(T exchange_value, T volatile* dest) const {
863 typedef PrimitiveConversions::Translate<T> Translator;
864 typedef typename Translator::Decayed Decayed;
865 STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
866 return Translator::recover(
867 xchg(Translator::decay(exchange_value),
868 reinterpret_cast<Decayed volatile*>(dest)));
869 }
870 };
871
872 template<typename Type, typename Fn, typename T>
873 inline T Atomic::xchg_using_helper(Fn fn,
874 T exchange_value,
875 T volatile* dest) {
876 STATIC_ASSERT(sizeof(Type) == sizeof(T));
877 return PrimitiveConversions::cast<T>(
878 fn(PrimitiveConversions::cast<Type>(exchange_value),
879 reinterpret_cast<Type volatile*>(dest)));
880 }
881
882 template<typename T, typename D>
883 inline D Atomic::xchg(T exchange_value, volatile D* dest) {
884 return XchgImpl<T, D>()(exchange_value, dest);
885 }
886
887 #endif // SHARE_VM_RUNTIME_ATOMIC_HPP