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src/hotspot/share/runtime/atomic.hpp
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rev 47321 : [mq]: Atomic_loadstore
@@ -62,28 +62,31 @@
// these semantics reflect the strength of atomic operations that are
// provided on SPARC/X86. We assume that strength is necessary unless
// we can prove that a weaker form is sufficiently safe.
// Atomically store to a location
- inline static void store (jbyte store_value, jbyte* dest);
- inline static void store (jshort store_value, jshort* dest);
- inline static void store (jint store_value, jint* dest);
// See comment above about using jlong atomics on 32-bit platforms
- inline static void store (jlong store_value, jlong* dest);
- inline static void store_ptr(intptr_t store_value, intptr_t* dest);
- inline static void store_ptr(void* store_value, void* dest);
-
- inline static void store (jbyte store_value, volatile jbyte* dest);
- inline static void store (jshort store_value, volatile jshort* dest);
- inline static void store (jint store_value, volatile jint* dest);
- // See comment above about using jlong atomics on 32-bit platforms
- inline static void store (jlong store_value, volatile jlong* dest);
- inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest);
- inline static void store_ptr(void* store_value, volatile void* dest);
+ // The type T must be either a pointer type convertible to or equal
+ // to D, an integral/enum type equal to D, or a type equal to D that
+ // is primitive convertible using PrimitiveConversions.
+ template<typename T, typename D>
+ inline static void store(T store_value, volatile D* dest);
+
+ inline static void store_ptr(intptr_t store_value, volatile intptr_t* dest) {
+ Atomic::store(store_value, dest);
+ }
+ inline static void store_ptr(void* store_value, volatile void* dest) {
+ Atomic::store(store_value, reinterpret_cast<void* volatile*>(dest));
+ }
+
+ // Atomically load from a location
// See comment above about using jlong atomics on 32-bit platforms
- inline static jlong load(const volatile jlong* src);
+ // The type T must be either a pointer type, an integral/enum type,
+ // or a type that is primitive convertible using PrimitiveConversions.
+ template<typename T>
+ inline static T load(const volatile T* dest);
// Atomically add to a location. Returns updated value. add*() provide:
// <fence> add-value-to-dest <membar StoreLoad|StoreStore>
template<typename I, typename D>
@@ -172,10 +175,61 @@
// From and To must be pointer types.
// Note: Provides the limited subset of C++11 std::is_convertible
// that is needed here.
template<typename From, typename To> struct IsPointerConvertible;
+ // Dispatch handler for store. Provides type-based validity
+ // checking and limited conversions around calls to the platform-
+ // specific implementation layer provided by PlatformOp.
+ template<typename T, typename D, typename PlatformOp, typename Enable = void>
+ struct StoreImpl;
+
+ // Platform-specific implementation of store. Support for sizes
+ // of 1, 2, 4, and (if different) pointer size bytes are required.
+ // The class is a function object that must be default constructable,
+ // with these requirements:
+ //
+ // either:
+ // - dest is of type D*, an integral, enum or pointer type.
+ // - new_value are of type T, an integral, enum or pointer type D or
+ // pointer type convertible to D.
+ // or:
+ // - T and D are the same and are primitive convertible using PrimitiveConversions
+ // and either way:
+ // - platform_store is an object of type PlatformStore<sizeof(T)>.
+ //
+ // Then
+ // platform_store(new_value, dest)
+ // must be a valid expression.
+ //
+ // The default implementation is a volatile store. If a platform
+ // requires more for e.g. 64 bit stores, a specialization is required
+ template<size_t byte_size> struct PlatformStore;
+
+ // Dispatch handler for load. Provides type-based validity
+ // checking and limited conversions around calls to the platform-
+ // specific implementation layer provided by PlatformOp.
+ template<typename T, typename PlatformOp, typename Enable = void>
+ struct LoadImpl;
+
+ // Platform-specific implementation of load. Support for sizes of
+ // 1, 2, 4 bytes and (if different) pointer size bytes are required.
+ // The class is a function object that must be default
+ // constructable, with these requirements:
+ //
+ // - dest is of type T*, an integral, enum or pointer type, or
+ // T is convertible to a primitive type using PrimitiveConversions
+ // - platform_load is an object of type PlatformLoad<sizeof(T)>.
+ //
+ // Then
+ // platform_load(src)
+ // must be a valid expression, returning a result convertible to T.
+ //
+ // The default implementation is a volatile load. If a platform
+ // requires more for e.g. 64 bit loads, a specialization is required
+ template<size_t byte_size> struct PlatformLoad;
+
// Dispatch handler for add. Provides type-based validity checking
// and limited conversions around calls to the platform-specific
// implementation layer provided by PlatformAdd.
template<typename I, typename D, typename Enable = void>
struct AddImpl;
@@ -342,10 +396,135 @@
static From* test_value;
static const bool value = (sizeof(yes) == sizeof(test(test_value)));
};
+// Handle load for pointer, integral and enum types.
+template<typename T, typename PlatformOp>
+struct Atomic::LoadImpl<
+ T,
+ PlatformOp,
+ typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value || IsPointer<T>::value>::type>
+ VALUE_OBJ_CLASS_SPEC
+{
+ T operator()(T const volatile* dest) const {
+ // Forward to the platform handler for the size of T.
+ return PlatformOp()(dest);
+ }
+};
+
+// Handle load for types that have a translator.
+//
+// All the involved types must be identical.
+//
+// This translates the original call into a call on the decayed
+// arguments, and returns the recovered result of that translated
+// call.
+template<typename T, typename PlatformOp>
+struct Atomic::LoadImpl<
+ T,
+ PlatformOp,
+ typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
+ VALUE_OBJ_CLASS_SPEC
+{
+ T operator()(T const volatile* dest) const {
+ typedef PrimitiveConversions::Translate<T> Translator;
+ typedef typename Translator::Decayed Decayed;
+ STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
+ Decayed result = PlatformOp()(reinterpret_cast<Decayed const volatile*>(dest));
+ return Translator::recover(result);
+ }
+};
+
+// Default implementation of atomic load if a specific platform
+// does not provide a specialization for a certain size class.
+// For increased safety, the default implementation only allows
+// load types that are pointer sized or smaller. If a platform still
+// supports wide atomics, then it has to use specialization
+// of Atomic::PlatformLoad for that wider size class.
+template<size_t byte_size>
+struct Atomic::PlatformLoad VALUE_OBJ_CLASS_SPEC {
+ template<typename T>
+ T operator()(T const volatile* dest) const {
+ STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
+ return *dest;
+ }
+};
+
+// Handle store for integral and enum types.
+//
+// All the involved types must be identical.
+template<typename T, typename PlatformOp>
+struct Atomic::StoreImpl<
+ T, T,
+ PlatformOp,
+ typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
+ VALUE_OBJ_CLASS_SPEC
+{
+ void operator()(T new_value, T volatile* dest) const {
+ // Forward to the platform handler for the size of T.
+ PlatformOp()(new_value, dest);
+ }
+};
+
+// Handle store for pointer types.
+//
+// The new_value must be implicitly convertible to the
+// destination's type; it must be type-correct to store the
+// new_value in the destination.
+template<typename T, typename D, typename PlatformOp>
+struct Atomic::StoreImpl<
+ T*, D*,
+ PlatformOp,
+ typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
+ VALUE_OBJ_CLASS_SPEC
+{
+ void operator()(T* new_value, D* volatile* dest) const {
+ // Allow derived to base conversion, and adding cv-qualifiers.
+ D* value = new_value;
+ PlatformOp()(value, dest);
+ }
+};
+
+// Handle store for types that have a translator.
+//
+// All the involved types must be identical.
+//
+// This translates the original call into a call on the decayed
+// arguments.
+template<typename T, typename PlatformOp>
+struct Atomic::StoreImpl<
+ T, T,
+ PlatformOp,
+ typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
+ VALUE_OBJ_CLASS_SPEC
+{
+ void operator()(T new_value, T volatile* dest) const {
+ typedef PrimitiveConversions::Translate<T> Translator;
+ typedef typename Translator::Decayed Decayed;
+ STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
+ PlatformOp()(Translator::decay(new_value),
+ reinterpret_cast<Decayed volatile*>(dest));
+ }
+};
+
+// Default implementation of atomic store if a specific platform
+// does not provide a specialization for a certain size class.
+// For increased safety, the default implementation only allows
+// storing types that are pointer sized or smaller. If a platform still
+// supports wide atomics, then it has to use specialization
+// of Atomic::PlatformStore for that wider size class.
+template<size_t byte_size>
+struct Atomic::PlatformStore VALUE_OBJ_CLASS_SPEC {
+ template<typename T>
+ void operator()(T new_value,
+ T volatile* dest) const {
+ STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
+ (void)const_cast<T&>(*dest = new_value);
+ }
+};
+
// Define FetchAndAdd and AddAndFetch helper classes before including
// platform file, which may use these as base classes, requiring they
// be complete.
template<typename Derived>
@@ -422,10 +601,20 @@
// size_t casts...
#if (SIZE_MAX != UINTPTR_MAX)
#error size_t is not WORD_SIZE, interesting platform, but missing implementation here
#endif
+template<typename T>
+inline T Atomic::load(const volatile T* dest) {
+ return LoadImpl<T, PlatformLoad<sizeof(T)> >()(dest);
+}
+
+template<typename T, typename D>
+inline void Atomic::store(T store_value, volatile D* dest) {
+ StoreImpl<T, D, PlatformStore<sizeof(D)> >()(store_value, dest);
+}
+
template<typename I, typename D>
inline D Atomic::add(I add_value, D volatile* dest) {
return AddImpl<I, D>()(add_value, dest);
}
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