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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
#ifndef SHARE_RUNTIME_ATOMIC_HPP
#define SHARE_RUNTIME_ATOMIC_HPP
#include "memory/allocation.hpp"
#include "metaprogramming/conditional.hpp"
#include "metaprogramming/enableIf.hpp"
#include "metaprogramming/isIntegral.hpp"
#include "metaprogramming/isPointer.hpp"
#include "metaprogramming/isSame.hpp"
#include "metaprogramming/primitiveConversions.hpp"
#include "metaprogramming/removeCV.hpp"
#include "metaprogramming/removePointer.hpp"
#include "runtime/orderAccess.hpp"
#include "utilities/align.hpp"
#include "utilities/bytes.hpp"
#include "utilities/macros.hpp"
#include <type_traits>
enum atomic_memory_order {
// The modes that align with C++11 are intended to
// follow the same semantics.
memory_order_relaxed = 0,
memory_order_acquire = 2,
memory_order_release = 3,
memory_order_acq_rel = 4,
memory_order_seq_cst = 5,
// Strong two-way memory barrier.
memory_order_conservative = 8
};
enum ScopedFenceType {
X_ACQUIRE
, RELEASE_X
, RELEASE_X_FENCE
};
class Atomic : AllStatic {
public:
// Atomic operations on int64 types are not available on all 32-bit
// platforms. If atomic ops on int64 are defined here they must only
// be used from code that verifies they are available at runtime and
// can provide an alternative action if not - see supports_cx8() for
// a means to test availability.
// The memory operations that are mentioned with each of the atomic
// function families come from src/share/vm/runtime/orderAccess.hpp,
// e.g., <fence> is described in that file and is implemented by the
// OrderAccess::fence() function. See that file for the gory details
// on the Memory Access Ordering Model.
// All of the atomic operations that imply a read-modify-write action
// guarantee a two-way memory barrier across that operation. Historically
// 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
// 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 D, typename T>
inline static void store(volatile D* dest, T store_value);
template <typename D, typename T>
inline static void release_store(volatile D* dest, T store_value);
template <typename D, typename T>
inline static void release_store_fence(volatile D* dest, T store_value);
// Atomically load from a location
// 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);
template <typename T>
inline static T load_acquire(const volatile T* dest);
// Atomically add to a location. *add*() provide:
// <fence> add-value-to-dest <membar StoreLoad|StoreStore>
// Returns updated value.
template<typename D, typename I>
inline static D add(D volatile* dest, I add_value,
atomic_memory_order order = memory_order_conservative);
// Returns previous value.
template<typename D, typename I>
inline static D fetch_and_add(D volatile* dest, I add_value,
atomic_memory_order order = memory_order_conservative);
template<typename D, typename I>
inline static D sub(D volatile* dest, I sub_value,
atomic_memory_order order = memory_order_conservative);
// Atomically increment location. inc() provide:
// <fence> increment-dest <membar StoreLoad|StoreStore>
// The type D may be either a pointer type, or an integral
// type. If it is a pointer type, then the increment is
// scaled to the size of the type pointed to by the pointer.
template<typename D>
inline static void inc(D volatile* dest,
atomic_memory_order order = memory_order_conservative);
// Atomically decrement a location. dec() provide:
// <fence> decrement-dest <membar StoreLoad|StoreStore>
// The type D may be either a pointer type, or an integral
// type. If it is a pointer type, then the decrement is
// scaled to the size of the type pointed to by the pointer.
template<typename D>
inline static void dec(D volatile* dest,
atomic_memory_order order = memory_order_conservative);
// Performs atomic exchange of *dest with exchange_value. Returns old
// prior value of *dest. xchg*() provide:
// <fence> exchange-value-with-dest <membar StoreLoad|StoreStore>
// 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 D, typename T>
inline static D xchg(volatile D* dest, T exchange_value,
atomic_memory_order order = memory_order_conservative);
// Performs atomic compare of *dest and compare_value, and exchanges
// *dest with exchange_value if the comparison succeeded. Returns prior
// value of *dest. cmpxchg*() provide:
// <fence> compare-and-exchange <membar StoreLoad|StoreStore>
template<typename D, typename U, typename T>
inline static D cmpxchg(D volatile* dest,
U compare_value,
T exchange_value,
atomic_memory_order order = memory_order_conservative);
// Performs atomic compare of *dest and NULL, and replaces *dest
// with exchange_value if the comparison succeeded. Returns true if
// the comparison succeeded and the exchange occurred. This is
// often used as part of lazy initialization, as a lock-free
// alternative to the Double-Checked Locking Pattern.
template<typename D, typename T>
inline static bool replace_if_null(D* volatile* dest, T* value,
atomic_memory_order order = memory_order_conservative);
private:
// Test whether From is implicitly convertible to To.
// 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;
protected:
// 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 D, typename T, 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;
// Give platforms a variation point to specialize.
template<size_t byte_size, ScopedFenceType type> struct PlatformOrderedStore;
template<size_t byte_size, ScopedFenceType type> struct PlatformOrderedLoad;
private:
// 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 D, typename I, typename Enable = void>
struct AddImpl;
// Platform-specific implementation of add. Support for sizes of 4
// bytes and (if different) pointer size bytes are required. The
// class must be default constructable, with these requirements:
//
// - dest is of type D*, where D is an integral or pointer type.
// - add_value is of type I, an integral type.
// - sizeof(I) == sizeof(D).
// - if D is an integral type, I == D.
// - if D is a pointer type P*, sizeof(P) == 1.
// - order is of type atomic_memory_order.
// - platform_add is an object of type PlatformAdd<sizeof(D)>.
//
// Then both
// platform_add.add_and_fetch(dest, add_value, order)
// platform_add.fetch_and_add(dest, add_value, order)
// must be valid expressions returning a result convertible to D.
//
// add_and_fetch atomically adds add_value to the value of dest,
// returning the new value.
//
// fetch_and_add atomically adds add_value to the value of dest,
// returning the old value.
//
// When the destination type D of the Atomic operation is a pointer type P*,
// the addition must scale the add_value by sizeof(P) to add that many bytes
// to the destination value. Rather than requiring each platform deal with
// this, the shared part of the implementation performs some adjustments
// before and after calling the platform operation. It ensures the pointee
// type of the destination value passed to the platform operation has size
// 1, casting if needed. It also scales add_value by sizeof(P). The result
// of the platform operation is cast back to P*. This means the platform
// operation does not need to account for the scaling. It also makes it
// easy for the platform to implement one of add_and_fetch or fetch_and_add
// in terms of the other (which is a common approach).
//
// No definition is provided; all platforms must explicitly define
// this class and any needed specializations.
template<size_t byte_size> struct PlatformAdd;
// Support for platforms that implement some variants of add using a
// (typically out of line) non-template helper function. The
// generic arguments passed to PlatformAdd need to be translated to
// the appropriate type for the helper function, the helper function
// invoked on the translated arguments, and the result translated
// back. Type is the parameter / return type of the helper
// function. No scaling of add_value is performed when D is a pointer
// type, so this function can be used to implement the support function
// required by AddAndFetch.
template<typename Type, typename Fn, typename D, typename I>
static D add_using_helper(Fn fn, D volatile* dest, I add_value);
// Dispatch handler for cmpxchg. Provides type-based validity
// checking and limited conversions around calls to the
// platform-specific implementation layer provided by
// PlatformCmpxchg.
template<typename D, typename U, typename T, typename Enable = void>
struct CmpxchgImpl;
// Platform-specific implementation of cmpxchg. Support for sizes
// of 1, 4, and 8 are required. The class is a function object that
// must be default constructable, with these requirements:
//
// - dest is of type T*.
// - exchange_value and compare_value are of type T.
// - order is of type atomic_memory_order.
// - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>.
//
// Then
// platform_cmpxchg(dest, compare_value, exchange_value, order)
// must be a valid expression, returning a result convertible to T.
//
// A default definition is provided, which declares a function template
// T operator()(T volatile*, T, T, atomic_memory_order) const
//
// For each required size, a platform must either provide an
// appropriate definition of that function, or must entirely
// specialize the class template for that size.
template<size_t byte_size> struct PlatformCmpxchg;
// Support for platforms that implement some variants of cmpxchg
// using a (typically out of line) non-template helper function.
// The generic arguments passed to PlatformCmpxchg need to be
// translated to the appropriate type for the helper function, the
// helper invoked on the translated arguments, and the result
// translated back. Type is the parameter / return type of the
// helper function.
template<typename Type, typename Fn, typename T>
static T cmpxchg_using_helper(Fn fn,
T volatile* dest,
T compare_value,
T exchange_value);
// Support platforms that do not provide Read-Modify-Write
// byte-level atomic access. To use, derive PlatformCmpxchg<1> from
// this class.
public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
struct CmpxchgByteUsingInt;
private:
// Dispatch handler for xchg. Provides type-based validity
// checking and limited conversions around calls to the
// platform-specific implementation layer provided by
// PlatformXchg.
template<typename D, typename T, typename Enable = void>
struct XchgImpl;
// Platform-specific implementation of xchg. Support for sizes
// of 4, and sizeof(intptr_t) are required. The class is a function
// object that must be default constructable, with these requirements:
//
// - dest is of type T*.
// - exchange_value is of type T.
// - platform_xchg is an object of type PlatformXchg<sizeof(T)>.
//
// Then
// platform_xchg(dest, exchange_value)
// must be a valid expression, returning a result convertible to T.
//
// A default definition is provided, which declares a function template
// T operator()(T volatile*, T, atomic_memory_order) const
//
// For each required size, a platform must either provide an
// appropriate definition of that function, or must entirely
// specialize the class template for that size.
template<size_t byte_size> struct PlatformXchg;
// Support for platforms that implement some variants of xchg
// using a (typically out of line) non-template helper function.
// The generic arguments passed to PlatformXchg need to be
// translated to the appropriate type for the helper function, the
// helper invoked on the translated arguments, and the result
// translated back. Type is the parameter / return type of the
// helper function.
template<typename Type, typename Fn, typename T>
static T xchg_using_helper(Fn fn,
T volatile* dest,
T exchange_value);
};
template<typename From, typename To>
struct Atomic::IsPointerConvertible<From*, To*> : AllStatic {
// Determine whether From* is implicitly convertible to To*, using
// the "sizeof trick".
typedef char yes;
typedef char (&no)[2];
static yes test(To*);
static no test(...);
static From* test_value;
static const bool value = (sizeof(yes) == sizeof(test(test_value)));
};
// Handle load for pointer and integral types.
template<typename T, typename PlatformOp>
struct Atomic::LoadImpl<
T,
PlatformOp,
typename EnableIf<IsIntegral<T>::value || IsPointer<T>::value>::type>
{
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>
{
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 {
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 types.
//
// All the involved types must be identical.
template<typename T, typename PlatformOp>
struct Atomic::StoreImpl<
T, T,
PlatformOp,
typename EnableIf<IsIntegral<T>::value>::type>
{
void operator()(T volatile* dest, T new_value) const {
// Forward to the platform handler for the size of T.
PlatformOp()(dest, new_value);
}
};
// 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 D, typename T, typename PlatformOp>
struct Atomic::StoreImpl<
D*, T*,
PlatformOp,
typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
{
void operator()(D* volatile* dest, T* new_value) const {
// Allow derived to base conversion, and adding cv-qualifiers.
D* value = new_value;
PlatformOp()(dest, value);
}
};
// 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>
{
void operator()(T volatile* dest, T new_value) const {
typedef PrimitiveConversions::Translate<T> Translator;
typedef typename Translator::Decayed Decayed;
STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
PlatformOp()(reinterpret_cast<Decayed volatile*>(dest),
Translator::decay(new_value));
}
};
// 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 {
template<typename T>
void operator()(T volatile* dest,
T new_value) const {
STATIC_ASSERT(sizeof(T) <= sizeof(void*)); // wide atomics need specialization
(void)const_cast<T&>(*dest = new_value);
}
};
template<typename D>
inline void Atomic::inc(D volatile* dest, atomic_memory_order order) {
STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
Atomic::add(dest, I(1), order);
}
template<typename D>
inline void Atomic::dec(D volatile* dest, atomic_memory_order order) {
STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
typedef typename Conditional<IsPointer<D>::value, ptrdiff_t, D>::type I;
// Assumes two's complement integer representation.
#pragma warning(suppress: 4146)
Atomic::add(dest, I(-1), order);
}
template<typename D, typename I>
inline D Atomic::sub(D volatile* dest, I sub_value, atomic_memory_order order) {
STATIC_ASSERT(IsPointer<D>::value || IsIntegral<D>::value);
STATIC_ASSERT(IsIntegral<I>::value);
// If D is a pointer type, use [u]intptr_t as the addend type,
// matching signedness of I. Otherwise, use D as the addend type.
typedef typename Conditional<IsSigned<I>::value, intptr_t, uintptr_t>::type PI;
typedef typename Conditional<IsPointer<D>::value, PI, D>::type AddendType;
// Only allow conversions that can't change the value.
STATIC_ASSERT(IsSigned<I>::value == IsSigned<AddendType>::value);
STATIC_ASSERT(sizeof(I) <= sizeof(AddendType));
AddendType addend = sub_value;
// Assumes two's complement integer representation.
#pragma warning(suppress: 4146) // In case AddendType is not signed.
return Atomic::add(dest, -addend, order);
}
// Define the class before including platform file, which may specialize
// the operator definition. No generic definition of specializations
// of the operator template are provided, nor are there any generic
// specializations of the class. The platform file is responsible for
// providing those.
template<size_t byte_size>
struct Atomic::PlatformCmpxchg {
template<typename T>
T operator()(T volatile* dest,
T compare_value,
T exchange_value,
atomic_memory_order order) const;
};
// Define the class before including platform file, which may use this
// as a base class, requiring it be complete. The definition is later
// in this file, near the other definitions related to cmpxchg.
struct Atomic::CmpxchgByteUsingInt {
static uint8_t get_byte_in_int(uint32_t n, uint32_t idx);
static uint32_t set_byte_in_int(uint32_t n, uint8_t b, uint32_t idx);
template<typename T>
T operator()(T volatile* dest,
T compare_value,
T exchange_value,
atomic_memory_order order) const;
};
// Define the class before including platform file, which may specialize
// the operator definition. No generic definition of specializations
// of the operator template are provided, nor are there any generic
// specializations of the class. The platform file is responsible for
// providing those.
template<size_t byte_size>
struct Atomic::PlatformXchg {
template<typename T>
T operator()(T volatile* dest,
T exchange_value,
atomic_memory_order order) const;
};
template <ScopedFenceType T>
class ScopedFenceGeneral: public StackObj {
public:
void prefix() {}
void postfix() {}
};
// The following methods can be specialized using simple template specialization
// in the platform specific files for optimization purposes. Otherwise the
// generalized variant is used.
template<> inline void ScopedFenceGeneral<X_ACQUIRE>::postfix() { OrderAccess::acquire(); }
template<> inline void ScopedFenceGeneral<RELEASE_X>::prefix() { OrderAccess::release(); }
template<> inline void ScopedFenceGeneral<RELEASE_X_FENCE>::prefix() { OrderAccess::release(); }
template<> inline void ScopedFenceGeneral<RELEASE_X_FENCE>::postfix() { OrderAccess::fence(); }
template <ScopedFenceType T>
class ScopedFence : public ScopedFenceGeneral<T> {
void *const _field;
public:
ScopedFence(void *const field) : _field(field) { prefix(); }
~ScopedFence() { postfix(); }
void prefix() { ScopedFenceGeneral<T>::prefix(); }
void postfix() { ScopedFenceGeneral<T>::postfix(); }
};
// platform specific in-line definitions - must come before shared definitions
#include OS_CPU_HEADER(atomic)
// shared in-line definitions
// 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<size_t byte_size, ScopedFenceType type>
struct Atomic::PlatformOrderedLoad {
template <typename T>
T operator()(const volatile T* p) const {
ScopedFence<type> f((void*)p);
return Atomic::load(p);
}
};
template <typename T>
inline T Atomic::load_acquire(const volatile T* p) {
return LoadImpl<T, PlatformOrderedLoad<sizeof(T), X_ACQUIRE> >()(p);
}
template<typename D, typename T>
inline void Atomic::store(volatile D* dest, T store_value) {
StoreImpl<D, T, PlatformStore<sizeof(D)> >()(dest, store_value);
}
template<size_t byte_size, ScopedFenceType type>
struct Atomic::PlatformOrderedStore {
template <typename T>
void operator()(volatile T* p, T v) const {
ScopedFence<type> f((void*)p);
Atomic::store(p, v);
}
};
template <typename D, typename T>
inline void Atomic::release_store(volatile D* p, T v) {
StoreImpl<D, T, PlatformOrderedStore<sizeof(D), RELEASE_X> >()(p, v);
}
template <typename D, typename T>
inline void Atomic::release_store_fence(volatile D* p, T v) {
StoreImpl<D, T, PlatformOrderedStore<sizeof(D), RELEASE_X_FENCE> >()(p, v);
}
template<typename D, typename I>
inline D Atomic::add(D volatile* dest, I add_value,
atomic_memory_order order) {
return AddImpl<D, I>::add_and_fetch(dest, add_value, order);
}
template<typename D, typename I>
inline D Atomic::fetch_and_add(D volatile* dest, I add_value,
atomic_memory_order order) {
return AddImpl<D, I>::fetch_and_add(dest, add_value, order);
}
template<typename D, typename I>
struct Atomic::AddImpl<
D, I,
typename EnableIf<IsIntegral<I>::value &&
IsIntegral<D>::value &&
(sizeof(I) <= sizeof(D)) &&
(IsSigned<I>::value == IsSigned<D>::value)>::type>
{
static D add_and_fetch(D volatile* dest, I add_value, atomic_memory_order order) {
D addend = add_value;
return PlatformAdd<sizeof(D)>().add_and_fetch(dest, addend, order);
}
static D fetch_and_add(D volatile* dest, I add_value, atomic_memory_order order) {
D addend = add_value;
return PlatformAdd<sizeof(D)>().fetch_and_add(dest, addend, order);
}
};
template<typename P, typename I>
struct Atomic::AddImpl<
P*, I,
typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type>
{
STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*));
STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*));
// Type of the scaled addend. An integral type of the same size as a
// pointer, and the same signedness as I.
using SI = typename Conditional<IsSigned<I>::value, intptr_t, uintptr_t>::type;
// Type of the unscaled destination. A pointer type with pointee size == 1.
using UP = const char*;
// Scale add_value by the size of the pointee.
static SI scale_addend(SI add_value) {
return add_value * SI(sizeof(P));
}
// Casting between P* and UP* here intentionally uses C-style casts,
// because reinterpret_cast can't cast away cv qualifiers. Using copy_cv
// would be an alternative if it existed.
// Unscale dest to a char* pointee for consistency with scaled addend.
static UP volatile* unscale_dest(P* volatile* dest) {
return (UP volatile*) dest;
}
// Convert the unscaled char* result to a P*.
static P* scale_result(UP result) {
return (P*) result;
}
static P* add_and_fetch(P* volatile* dest, I addend, atomic_memory_order order) {
return scale_result(PlatformAdd<sizeof(P*)>().add_and_fetch(unscale_dest(dest),
scale_addend(addend),
order));
}
static P* fetch_and_add(P* volatile* dest, I addend, atomic_memory_order order) {
return scale_result(PlatformAdd<sizeof(P*)>().fetch_and_add(unscale_dest(dest),
scale_addend(addend),
order));
}
};
template<typename Type, typename Fn, typename D, typename I>
inline D Atomic::add_using_helper(Fn fn, D volatile* dest, I add_value) {
return PrimitiveConversions::cast<D>(
fn(PrimitiveConversions::cast<Type>(add_value),
reinterpret_cast<Type volatile*>(dest)));
}
template<typename D, typename U, typename T>
inline D Atomic::cmpxchg(D volatile* dest,
U compare_value,
T exchange_value,
atomic_memory_order order) {
return CmpxchgImpl<D, U, T>()(dest, compare_value, exchange_value, order);
}
template<typename D, typename T>
inline bool Atomic::replace_if_null(D* volatile* dest, T* value,
atomic_memory_order order) {
// Presently using a trivial implementation in terms of cmpxchg.
// Consider adding platform support, to permit the use of compiler
// intrinsics like gcc's __sync_bool_compare_and_swap.
D* expected_null = NULL;
return expected_null == cmpxchg(dest, expected_null, value, order);
}
// Handle cmpxchg for integral types.
//
// All the involved types must be identical.
template<typename T>
struct Atomic::CmpxchgImpl<
T, T, T,
typename EnableIf<IsIntegral<T>::value>::type>
{
T operator()(T volatile* dest, T compare_value, T exchange_value,
atomic_memory_order order) const {
// Forward to the platform handler for the size of T.
return PlatformCmpxchg<sizeof(T)>()(dest,
compare_value,
exchange_value,
order);
}
};
// Handle cmpxchg for pointer types.
//
// The destination's type and the compare_value type must be the same,
// ignoring cv-qualifiers; we don't care about the cv-qualifiers of
// the compare_value.
//
// The exchange_value must be implicitly convertible to the
// destination's type; it must be type-correct to store the
// exchange_value in the destination.
template<typename D, typename U, typename T>
struct Atomic::CmpxchgImpl<
D*, U*, T*,
typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value &&
IsSame<typename RemoveCV<D>::type,
typename RemoveCV<U>::type>::value>::type>
{
D* operator()(D* volatile* dest, U* compare_value, T* exchange_value,
atomic_memory_order order) const {
// Allow derived to base conversion, and adding cv-qualifiers.
D* new_value = exchange_value;
// Don't care what the CV qualifiers for compare_value are,
// but we need to match D* when calling platform support.
D* old_value = const_cast<D*>(compare_value);
return PlatformCmpxchg<sizeof(D*)>()(dest, old_value, new_value, order);
}
};
// Handle cmpxchg 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>
struct Atomic::CmpxchgImpl<
T, T, T,
typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
{
T operator()(T volatile* dest, T compare_value, T exchange_value,
atomic_memory_order order) const {
typedef PrimitiveConversions::Translate<T> Translator;
typedef typename Translator::Decayed Decayed;
STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
return Translator::recover(
cmpxchg(reinterpret_cast<Decayed volatile*>(dest),
Translator::decay(compare_value),
Translator::decay(exchange_value),
order));
}
};
template<typename Type, typename Fn, typename T>
inline T Atomic::cmpxchg_using_helper(Fn fn,
T volatile* dest,
T compare_value,
T exchange_value) {
STATIC_ASSERT(sizeof(Type) == sizeof(T));
return PrimitiveConversions::cast<T>(
fn(PrimitiveConversions::cast<Type>(exchange_value),
reinterpret_cast<Type volatile*>(dest),
PrimitiveConversions::cast<Type>(compare_value)));
}
inline uint32_t Atomic::CmpxchgByteUsingInt::set_byte_in_int(uint32_t n,
uint8_t b,
uint32_t idx) {
uint32_t bitsIdx = BitsPerByte * idx;
return (n & ~(static_cast<uint32_t>(0xff) << bitsIdx))
| (static_cast<uint32_t>(b) << bitsIdx);
}
inline uint8_t Atomic::CmpxchgByteUsingInt::get_byte_in_int(uint32_t n,
uint32_t idx) {
uint32_t bitsIdx = BitsPerByte * idx;
return (uint8_t)(n >> bitsIdx);
}
template<typename T>
inline T Atomic::CmpxchgByteUsingInt::operator()(T volatile* dest,
T compare_value,
T exchange_value,
atomic_memory_order order) const {
STATIC_ASSERT(sizeof(T) == sizeof(uint8_t));
uint8_t canon_exchange_value = exchange_value;
uint8_t canon_compare_value = compare_value;
volatile uint32_t* aligned_dest
= reinterpret_cast<volatile uint32_t*>(align_down(dest, sizeof(uint32_t)));
size_t offset = pointer_delta(dest, aligned_dest, 1);
uint32_t idx = (Endian::NATIVE == Endian::BIG)
? (sizeof(uint32_t) - 1 - offset)
: offset;
// current value may not be what we are looking for, so force it
// to that value so the initial cmpxchg will fail if it is different
uint32_t cur = set_byte_in_int(Atomic::load(aligned_dest), canon_compare_value, idx);
// always execute a real cmpxchg so that we get the required memory
// barriers even on initial failure
do {
// value to swap in matches current value
// except for the one byte we want to update
uint32_t new_value = set_byte_in_int(cur, canon_exchange_value, idx);
uint32_t res = cmpxchg(aligned_dest, cur, new_value, order);
if (res == cur) break; // success
// at least one byte in the int changed value, so update
// our view of the current int
cur = res;
// if our byte is still as cur we loop and try again
} while (get_byte_in_int(cur, idx) == canon_compare_value);
return PrimitiveConversions::cast<T>(get_byte_in_int(cur, idx));
}
// Handle xchg for integral types.
//
// All the involved types must be identical.
template<typename T>
struct Atomic::XchgImpl<
T, T,
typename EnableIf<IsIntegral<T>::value>::type>
{
T operator()(T volatile* dest, T exchange_value, atomic_memory_order order) const {
// Forward to the platform handler for the size of T.
return PlatformXchg<sizeof(T)>()(dest, exchange_value, order);
}
};
// Handle xchg for pointer types.
//
// The exchange_value must be implicitly convertible to the
// destination's type; it must be type-correct to store the
// exchange_value in the destination.
template<typename D, typename T>
struct Atomic::XchgImpl<
D*, T*,
typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value>::type>
{
D* operator()(D* volatile* dest, T* exchange_value, atomic_memory_order order) const {
// Allow derived to base conversion, and adding cv-qualifiers.
D* new_value = exchange_value;
return PlatformXchg<sizeof(D*)>()(dest, new_value, order);
}
};
// Handle xchg 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>
struct Atomic::XchgImpl<
T, T,
typename EnableIf<PrimitiveConversions::Translate<T>::value>::type>
{
T operator()(T volatile* dest, T exchange_value, atomic_memory_order order) const {
typedef PrimitiveConversions::Translate<T> Translator;
typedef typename Translator::Decayed Decayed;
STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
return Translator::recover(
xchg(reinterpret_cast<Decayed volatile*>(dest),
Translator::decay(exchange_value),
order));
}
};
template<typename Type, typename Fn, typename T>
inline T Atomic::xchg_using_helper(Fn fn,
T volatile* dest,
T exchange_value) {
STATIC_ASSERT(sizeof(Type) == sizeof(T));
// Notice the swapped order of arguments. Change when/if stubs are rewritten.
return PrimitiveConversions::cast<T>(
fn(PrimitiveConversions::cast<Type>(exchange_value),
reinterpret_cast<Type volatile*>(dest)));
}
template<typename D, typename T>
inline D Atomic::xchg(volatile D* dest, T exchange_value, atomic_memory_order order) {
return XchgImpl<D, T>()(dest, exchange_value, order);
}
#endif // SHARE_RUNTIME_ATOMIC_HPP
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