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atomics: Use __atomic_*_n() variant primitives

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Use the __atomic_*_n() primitives which take the value as argument. It
is not necessary to store the value locally before calling the
primitive, hence saving us a stack store and load.

Backports commit 89943de17c4e276f2c47f05b4604e8816a6a636c from qemu
This commit is contained in:
Pranith Kumar 2018-02-26 02:16:39 -05:00 committed by Lioncash
parent 1a2c30abbf
commit 9e6fec8741
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 30 additions and 29 deletions
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59
qemu/include/qemu/atomic.h
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@ -60,14 +60,13 @@ void _ReadWriteBarrier(void);
*/
#define atomic_read(ptr) \
({ \
typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
_val; \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_load_n(ptr, __ATOMIC_RELAXED); \
})
#define atomic_set(ptr, i) do { \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
} while(0)
/* See above: most compilers currently treat consume and acquire the
@ -82,16 +81,17 @@ void _ReadWriteBarrier(void);
smp_read_barrier_depends();
#endif
#define atomic_rcu_read(ptr) \
({ \
typeof(*ptr) _val; \
atomic_rcu_read__nocheck(ptr, &_val); \
_val; \
#define atomic_rcu_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \
atomic_rcu_read__nocheck(ptr, &_val); \
_val; \
})
#define atomic_rcu_set(ptr, i) do { \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_RELEASE); \
#define atomic_rcu_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store_n(ptr, i, __ATOMIC_RELEASE); \
} while(0)
/* atomic_mb_read/set semantics map Java volatile variables. They are
@ -105,6 +105,7 @@ void _ReadWriteBarrier(void);
#if defined(_ARCH_PPC)
#define atomic_mb_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
smp_rmb(); \
@ -112,41 +113,41 @@ void _ReadWriteBarrier(void);
})
#define atomic_mb_set(ptr, i) do { \
typeof(*ptr) _val = (i); \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
smp_wmb(); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
__atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
smp_mb(); \
} while(0)
#else
#define atomic_mb_read(ptr) \
({ \
typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
_val; \
#define atomic_mb_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
_val; \
})
#define atomic_mb_set(ptr, i) do { \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_SEQ_CST); \
#define atomic_mb_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store_n(ptr, i, __ATOMIC_SEQ_CST); \
} while(0)
#endif
/* All the remaining operations are fully sequentially consistent */
#define atomic_xchg(ptr, i) ({ \
typeof(*ptr) _new = (i), _old; \
__atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \
_old; \
#define atomic_xchg(ptr, i) ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_exchange_n(ptr, i, __ATOMIC_SEQ_CST); \
})
/* Returns the eventual value, failed or not */
#define atomic_cmpxchg(ptr, old, new) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _old = (old), _new = (new); \
__atomic_compare_exchange(ptr, &_old, &_new, false, \
__atomic_compare_exchange_n(ptr, &_old, new, false, \
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
_old; \
})
/* Provide shorter names for GCC atomic builtins, return old value */