8187443: Forest Consolidation: Move files to unified layout
Reviewed-by: darcy, ihse
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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#ifndef SHARE_VM_RUNTIME_ATOMIC_HPP
#define SHARE_VM_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 "utilities/align.hpp"
#include "utilities/macros.hpp"
enum cmpxchg_memory_order {
memory_order_relaxed,
// Use value which doesn't interfere with C++2011. We need to be more conservative.
memory_order_conservative = 8
};
class Atomic : AllStatic {
public:
// Atomic operations on jlong types are not available on all 32-bit
// platforms. If atomic ops on jlongs 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
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);
// See comment above about using jlong atomics on 32-bit platforms
inline static jlong load(const volatile jlong* src);
// Atomically add to a location. Returns updated value. add*() provide:
// <fence> add-value-to-dest <membar StoreLoad|StoreStore>
template<typename I, typename D>
inline static D add(I add_value, D volatile* dest);
inline static intptr_t add_ptr(intptr_t add_value, volatile intptr_t* dest) {
return add(add_value, dest);
}
inline static void* add_ptr(intptr_t add_value, volatile void* dest) {
return add(add_value, reinterpret_cast<char* volatile*>(dest));
}
// Atomically increment location. inc*() provide:
// <fence> increment-dest <membar StoreLoad|StoreStore>
inline static void inc (volatile jint* dest);
inline static void inc (volatile jshort* dest);
inline static void inc (volatile size_t* dest);
inline static void inc_ptr(volatile intptr_t* dest);
inline static void inc_ptr(volatile void* dest);
// Atomically decrement a location. dec*() provide:
// <fence> decrement-dest <membar StoreLoad|StoreStore>
inline static void dec (volatile jint* dest);
inline static void dec (volatile jshort* dest);
inline static void dec (volatile size_t* dest);
inline static void dec_ptr(volatile intptr_t* dest);
inline static void dec_ptr(volatile void* dest);
// Performs atomic exchange of *dest with exchange_value. Returns old
// prior value of *dest. xchg*() provide:
// <fence> exchange-value-with-dest <membar StoreLoad|StoreStore>
inline static jint xchg (jint exchange_value, volatile jint* dest);
inline static unsigned int xchg (unsigned int exchange_value, volatile unsigned int* dest);
inline static intptr_t xchg_ptr(intptr_t exchange_value, volatile intptr_t* dest);
inline static void* xchg_ptr(void* exchange_value, volatile void* dest);
// 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 T, typename D, typename U>
inline static D cmpxchg(T exchange_value,
D volatile* dest,
U compare_value,
cmpxchg_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 T, typename D>
inline static bool replace_if_null(T* value, D* volatile* dest,
cmpxchg_memory_order order = memory_order_conservative);
inline static intptr_t cmpxchg_ptr(intptr_t exchange_value,
volatile intptr_t* dest,
intptr_t compare_value,
cmpxchg_memory_order order = memory_order_conservative) {
return cmpxchg(exchange_value, dest, compare_value, order);
}
inline static void* cmpxchg_ptr(void* exchange_value,
volatile void* dest,
void* compare_value,
cmpxchg_memory_order order = memory_order_conservative) {
return cmpxchg(exchange_value,
reinterpret_cast<void* volatile*>(dest),
compare_value,
order);
}
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;
// 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;
// Platform-specific implementation of add. Support for sizes of 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 D*, 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.
// - platform_add is an object of type PlatformAdd<sizeof(D)>.
//
// Then
// platform_add(add_value, dest)
// must be a valid expression, returning a result convertible to D.
//
// No definition is provided; all platforms must explicitly define
// this class and any needed specializations.
template<size_t byte_size> struct PlatformAdd;
// Helper base classes for defining PlatformAdd. To use, define
// PlatformAdd or a specialization that derives from one of these,
// and include in the PlatformAdd definition the support function
// (described below) required by the base class.
//
// These classes implement the required function object protocol for
// PlatformAdd, using a support function template provided by the
// derived class. Let add_value (of type I) and dest (of type D) be
// the arguments the object is called with. If D is a pointer type
// P*, then let addend (of type I) be add_value * sizeof(P);
// otherwise, addend is add_value.
//
// FetchAndAdd requires the derived class to provide
// fetch_and_add(addend, dest)
// atomically adding addend to the value of dest, and returning the
// old value.
//
// AddAndFetch requires the derived class to provide
// add_and_fetch(addend, dest)
// atomically adding addend to the value of dest, and returning the
// new value.
//
// When D is a pointer type P*, both fetch_and_add and add_and_fetch
// treat it as if it were a uintptr_t; they do not perform any
// scaling of the addend, as that has already been done by the
// caller.
public: // Temporary, can't be private: C++03 11.4/2. Fixed by C++11.
template<typename Derived> struct FetchAndAdd;
template<typename Derived> struct AddAndFetch;
private:
// 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 I, typename D>
static D add_using_helper(Fn fn, I add_value, D volatile* dest);
// 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 T, typename D, typename U, 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 cmpxchg_memory_order.
// - platform_cmpxchg is an object of type PlatformCmpxchg<sizeof(T)>.
//
// Then
// platform_cmpxchg(exchange_value, dest, compare_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, T volatile*, T, cmpxchg_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 exchange_value,
T volatile* dest,
T compare_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:
};
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)));
};
// Define FetchAndAdd and AddAndFetch helper classes before including
// platform file, which may use these as base classes, requiring they
// be complete.
template<typename Derived>
struct Atomic::FetchAndAdd VALUE_OBJ_CLASS_SPEC {
template<typename I, typename D>
D operator()(I add_value, D volatile* dest) const;
};
template<typename Derived>
struct Atomic::AddAndFetch VALUE_OBJ_CLASS_SPEC {
template<typename I, typename D>
D operator()(I add_value, D volatile* dest) 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::PlatformCmpxchg VALUE_OBJ_CLASS_SPEC {
template<typename T>
T operator()(T exchange_value,
T volatile* dest,
T compare_value,
cmpxchg_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 VALUE_OBJ_CLASS_SPEC {
template<typename T>
T operator()(T exchange_value,
T volatile* dest,
T compare_value,
cmpxchg_memory_order order) const;
};
// 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 I, typename D>
inline D Atomic::add(I add_value, D volatile* dest) {
return AddImpl<I, D>()(add_value, dest);
}
template<typename I, typename D>
struct Atomic::AddImpl<
I, D,
typename EnableIf<IsIntegral<I>::value &&
IsIntegral<D>::value &&
(sizeof(I) <= sizeof(D)) &&
(IsSigned<I>::value == IsSigned<D>::value)>::type>
VALUE_OBJ_CLASS_SPEC
{
D operator()(I add_value, D volatile* dest) const {
D addend = add_value;
return PlatformAdd<sizeof(D)>()(addend, dest);
}
};
template<typename I, typename P>
struct Atomic::AddImpl<
I, P*,
typename EnableIf<IsIntegral<I>::value && (sizeof(I) <= sizeof(P*))>::type>
VALUE_OBJ_CLASS_SPEC
{
P* operator()(I add_value, P* volatile* dest) const {
STATIC_ASSERT(sizeof(intptr_t) == sizeof(P*));
STATIC_ASSERT(sizeof(uintptr_t) == sizeof(P*));
typedef typename Conditional<IsSigned<I>::value,
intptr_t,
uintptr_t>::type CI;
CI addend = add_value;
return PlatformAdd<sizeof(P*)>()(addend, dest);
}
};
// Most platforms do not support atomic add on a 2-byte value. However,
// if the value occupies the most significant 16 bits of an aligned 32-bit
// word, then we can do this with an atomic add of (add_value << 16)
// to the 32-bit word.
//
// The least significant parts of this 32-bit word will never be affected, even
// in case of overflow/underflow.
//
// Use the ATOMIC_SHORT_PAIR macro (see macros.hpp) to get the desired alignment.
template<>
struct Atomic::AddImpl<jshort, jshort> VALUE_OBJ_CLASS_SPEC {
jshort operator()(jshort add_value, jshort volatile* dest) const {
#ifdef VM_LITTLE_ENDIAN
assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest-1));
#else
assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
jint new_value = Atomic::add(add_value << 16, (volatile jint*)(dest));
#endif
return (jshort)(new_value >> 16); // preserves sign
}
};
template<typename Derived>
template<typename I, typename D>
inline D Atomic::FetchAndAdd<Derived>::operator()(I add_value, D volatile* dest) const {
I addend = add_value;
// If D is a pointer type P*, scale by sizeof(P).
if (IsPointer<D>::value) {
addend *= sizeof(typename RemovePointer<D>::type);
}
D old = static_cast<const Derived*>(this)->fetch_and_add(addend, dest);
return old + add_value;
}
template<typename Derived>
template<typename I, typename D>
inline D Atomic::AddAndFetch<Derived>::operator()(I add_value, D volatile* dest) const {
// If D is a pointer type P*, scale by sizeof(P).
if (IsPointer<D>::value) {
add_value *= sizeof(typename RemovePointer<D>::type);
}
return static_cast<const Derived*>(this)->add_and_fetch(add_value, dest);
}
template<typename Type, typename Fn, typename I, typename D>
inline D Atomic::add_using_helper(Fn fn, I add_value, D volatile* dest) {
return PrimitiveConversions::cast<D>(
fn(PrimitiveConversions::cast<Type>(add_value),
reinterpret_cast<Type volatile*>(dest)));
}
inline void Atomic::inc(volatile size_t* dest) {
inc_ptr((volatile intptr_t*) dest);
}
inline void Atomic::dec(volatile size_t* dest) {
dec_ptr((volatile intptr_t*) dest);
}
template<typename T, typename D, typename U>
inline D Atomic::cmpxchg(T exchange_value,
D volatile* dest,
U compare_value,
cmpxchg_memory_order order) {
return CmpxchgImpl<T, D, U>()(exchange_value, dest, compare_value, order);
}
template<typename T, typename D>
inline bool Atomic::replace_if_null(T* value, D* volatile* dest,
cmpxchg_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(value, dest, expected_null, order);
}
// Handle cmpxchg for integral and enum types.
//
// All the involved types must be identical.
template<typename T>
struct Atomic::CmpxchgImpl<
T, T, T,
typename EnableIf<IsIntegral<T>::value || IsRegisteredEnum<T>::value>::type>
VALUE_OBJ_CLASS_SPEC
{
T operator()(T exchange_value, T volatile* dest, T compare_value,
cmpxchg_memory_order order) const {
// Forward to the platform handler for the size of T.
return PlatformCmpxchg<sizeof(T)>()(exchange_value,
dest,
compare_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 T, typename D, typename U>
struct Atomic::CmpxchgImpl<
T*, D*, U*,
typename EnableIf<Atomic::IsPointerConvertible<T*, D*>::value &&
IsSame<typename RemoveCV<D>::type,
typename RemoveCV<U>::type>::value>::type>
VALUE_OBJ_CLASS_SPEC
{
D* operator()(T* exchange_value, D* volatile* dest, U* compare_value,
cmpxchg_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*)>()(new_value, dest, old_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>
VALUE_OBJ_CLASS_SPEC
{
T operator()(T exchange_value, T volatile* dest, T compare_value,
cmpxchg_memory_order order) const {
typedef PrimitiveConversions::Translate<T> Translator;
typedef typename Translator::Decayed Decayed;
STATIC_ASSERT(sizeof(T) == sizeof(Decayed));
return Translator::recover(
cmpxchg(Translator::decay(exchange_value),
reinterpret_cast<Decayed volatile*>(dest),
Translator::decay(compare_value),
order));
}
};
template<typename Type, typename Fn, typename T>
inline T Atomic::cmpxchg_using_helper(Fn fn,
T exchange_value,
T volatile* dest,
T compare_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)));
}
template<typename T>
inline T Atomic::CmpxchgByteUsingInt::operator()(T exchange_value,
T volatile* dest,
T compare_value,
cmpxchg_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 cur = *aligned_dest;
uint8_t* cur_as_bytes = reinterpret_cast<uint8_t*>(&cur);
// 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
cur_as_bytes[offset] = canon_compare_value;
// 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 ...
uint32_t new_value = cur;
// ... except for the one jbyte we want to update
reinterpret_cast<uint8_t*>(&new_value)[offset] = canon_exchange_value;
uint32_t res = cmpxchg(new_value, aligned_dest, cur, 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 (cur_as_bytes[offset] == canon_compare_value);
return PrimitiveConversions::cast<T>(cur_as_bytes[offset]);
}
inline unsigned Atomic::xchg(unsigned int exchange_value, volatile unsigned int* dest) {
assert(sizeof(unsigned int) == sizeof(jint), "more work to do");
return (unsigned int)Atomic::xchg((jint)exchange_value, (volatile jint*)dest);
}
inline void Atomic::inc(volatile jshort* dest) {
(void)add(jshort(1), dest);
}
inline void Atomic::dec(volatile jshort* dest) {
(void)add(jshort(-1), dest);
}
#endif // SHARE_VM_RUNTIME_ATOMIC_HPP