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Atomic: cleanup and add more operations

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Cleanup:
	* Remove volatile keyword, it is of no use at all. [1]
	* Remove the enable_if stuff. It had no use either.
	  The most likely explanation why the enable_if stuff was there is that it
	  was used as something like a STATIC_ASSERT to verify that sizeof(T) is not larger
	  than sizeof(void *). This check however is not just misplaced in a place where we
	  already use a lock, it isn't needed at all, as gcc will just generate a call to
	  to the runtime if it compiles for platforms that don't support atomic instructions.
	  The runtime will then most likely use locks.

Code style fixes:
	* Prefix name of the mutex
	* Line everything up nicely, where it makes things look nice
	* Filling \ continuations with spaces is code style rule

Added operations on the atomic var:
	* Compare and swap
	* Swap

The second point of the cleanup also fixes the Android build of the next commit.

[1]: http://stackoverflow.com/q/2484980
This commit is contained in:
est31 2015-11-03 13:09:23 +01:00
parent 1550ab3c5d
commit abc354a5d0
1 changed files with 54 additions and 35 deletions
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89
src/threading/atomic.h
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@ -29,64 +29,83 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
#define CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
#if GCC_VERSION >= 407 || CLANG_VERSION >= 302
#define ATOMIC_LOAD(T, v) return __atomic_load_n(&(v), __ATOMIC_SEQ_CST)
#define ATOMIC_STORE(T, v, x) __atomic_store (&(v), &(x), __ATOMIC_SEQ_CST); return x
#define ATOMIC_ADD_EQ(T, v, x) return __atomic_add_fetch(&(v), (x), __ATOMIC_SEQ_CST)
#define ATOMIC_SUB_EQ(T, v, x) return __atomic_sub_fetch(&(v), (x), __ATOMIC_SEQ_CST)
#define ATOMIC_POST_INC(T, v) return __atomic_fetch_add(&(v), 1, __ATOMIC_SEQ_CST)
#define ATOMIC_POST_DEC(T, v) return __atomic_fetch_sub(&(v), 1, __ATOMIC_SEQ_CST)
#define ATOMIC_LOAD(T, v) return __atomic_load_n (&(v), __ATOMIC_SEQ_CST)
#define ATOMIC_STORE(T, v, x) __atomic_store (&(v), &(x), __ATOMIC_SEQ_CST); return x
#define ATOMIC_EXCHANGE(T, v, x) return __atomic_exchange_n(&(v), (x), __ATOMIC_SEQ_CST)
#define ATOMIC_ADD_EQ(T, v, x) return __atomic_add_fetch (&(v), (x), __ATOMIC_SEQ_CST)
#define ATOMIC_SUB_EQ(T, v, x) return __atomic_sub_fetch (&(v), (x), __ATOMIC_SEQ_CST)
#define ATOMIC_POST_INC(T, v) return __atomic_fetch_add (&(v), 1, __ATOMIC_SEQ_CST)
#define ATOMIC_POST_DEC(T, v) return __atomic_fetch_sub (&(v), 1, __ATOMIC_SEQ_CST)
#define ATOMIC_CAS(T, v, e, d) return __atomic_compare_exchange_n(&(v), &(e), (d), \
false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
#else
#define ATOMIC_USE_LOCK
#include "threading/mutex.h"
#define ATOMIC_LOCK_OP(T, op) do { \
mutex.lock(); \
T _val = (op); \
mutex.unlock(); \
return _val; \
m_mutex.lock(); \
T _val = (op); \
m_mutex.unlock(); \
return _val; \
} while (0)
#define ATOMIC_LOAD(T, v) \
#define ATOMIC_LOCK_CAS(T, v, e, d) do { \
m_mutex.lock(); \
bool _eq = (v == e); \
if (_eq) \
v = d; \
m_mutex.unlock(); \
return _eq; \
} while (0)
#define ATOMIC_LOAD(T, v) \
if (sizeof(T) <= sizeof(void*)) return v; \
else ATOMIC_LOCK_OP(T, v);
#define ATOMIC_STORE(T, v, x) \
#define ATOMIC_STORE(T, v, x) \
if (sizeof(T) <= sizeof(void*)) return v = x; \
else ATOMIC_LOCK_OP(T, v = x);
# if GCC_VERSION >= 401
#define ATOMIC_ADD_EQ(T, v, x) return __sync_add_and_fetch(&(v), (x))
#define ATOMIC_SUB_EQ(T, v, x) return __sync_sub_and_fetch(&(v), (x))
#define ATOMIC_POST_INC(T, v) return __sync_fetch_and_add(&(v), 1)
#define ATOMIC_POST_DEC(T, v) return __sync_fetch_and_sub(&(v), 1)
# else
#define ATOMIC_ADD_EQ(T, v, x) ATOMIC_LOCK_OP(T, v += x)
#define ATOMIC_SUB_EQ(T, v, x) ATOMIC_LOCK_OP(T, v -= x)
#define ATOMIC_POST_INC(T, v) ATOMIC_LOCK_OP(T, v++)
#define ATOMIC_POST_DEC(T, v) ATOMIC_LOCK_OP(T, v--)
# endif
#define ATOMIC_EXCHANGE(T, v, x) do { \
m_mutex.lock(); \
T _val = v; \
v = x; \
m_mutex.unlock(); \
return _val; \
} while (0)
#if GCC_VERSION >= 401
#define ATOMIC_ADD_EQ(T, v, x) return __sync_add_and_fetch(&(v), (x))
#define ATOMIC_SUB_EQ(T, v, x) return __sync_sub_and_fetch(&(v), (x))
#define ATOMIC_POST_INC(T, v) return __sync_fetch_and_add(&(v), 1)
#define ATOMIC_POST_DEC(T, v) return __sync_fetch_and_sub(&(v), 1)
#define ATOMIC_CAS(T, v, e, d) return __sync_bool_compare_and_swap(&(v), &(e), (d))
#else
#define ATOMIC_ADD_EQ(T, v, x) ATOMIC_LOCK_OP(T, v += x)
#define ATOMIC_SUB_EQ(T, v, x) ATOMIC_LOCK_OP(T, v -= x)
#define ATOMIC_POST_INC(T, v) ATOMIC_LOCK_OP(T, v++)
#define ATOMIC_POST_DEC(T, v) ATOMIC_LOCK_OP(T, v--)
#define ATOMIC_CAS(T, v, e, d) ATOMIC_LOCK_CAS(T, v, e, d)
#endif
#endif
template<typename T>
class Atomic
{
// Like C++11 std::enable_if, but defaults to char since C++03 doesn't support SFINAE
template<bool B, typename T_ = void> struct enable_if { typedef char type; };
template<typename T_> struct enable_if<true, T_> { typedef T_ type; };
class Atomic {
public:
Atomic(const T &v=0) : val(v) {}
Atomic(const T &v = 0) : val(v) {}
operator T () { ATOMIC_LOAD(T, val); }
T operator = (T x) { ATOMIC_STORE(T, val, x); }
T exchange(T x) { ATOMIC_EXCHANGE(T, val, x); }
bool compare_exchange_strong(T &expected, T desired) { ATOMIC_CAS(T, val, expected, desired); }
T operator = (T x) { ATOMIC_STORE(T, val, x); }
T operator += (T x) { ATOMIC_ADD_EQ(T, val, x); }
T operator -= (T x) { ATOMIC_SUB_EQ(T, val, x); }
T operator ++ () { return *this += 1; }
T operator -- () { return *this -= 1; }
T operator ++ () { return *this += 1; }
T operator -- () { return *this -= 1; }
T operator ++ (int) { ATOMIC_POST_INC(T, val); }
T operator -- (int) { ATOMIC_POST_DEC(T, val); }
private:
volatile T val;
T val;
#ifdef ATOMIC_USE_LOCK
typename enable_if<sizeof(T) <= sizeof(void*), Mutex>::type mutex;
Mutex m_mutex;
#endif
};