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atomics: Use __atomic_*_n() variant primitives 

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.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Message-Id: <20160829171701.14025-1-bobby.prani@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Pranith Kumar 2016-08-29 13:17:01 -04:00 committed by Paolo Bonzini
parent 705ac1ca53
commit 89943de17c
1 changed files with 8 additions and 16 deletions
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24
include/qemu/atomic.h
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@ -96,15 +96,12 @@
#define atomic_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof_strip_qual(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
_val; \
__atomic_load_n(ptr, __ATOMIC_RELAXED); \
})
#define atomic_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
__atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
} while(0)
/* See above: most compilers currently treat consume and acquire the
@ -129,8 +126,7 @@
#define atomic_rcu_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_RELEASE); \
__atomic_store_n(ptr, i, __ATOMIC_RELEASE); \
} while(0)
/* atomic_mb_read/set semantics map Java volatile variables. They are
@ -153,9 +149,8 @@
#define atomic_mb_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val = (i); \
smp_wmb(); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \
__atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
smp_mb(); \
} while(0)
#else
@ -169,8 +164,7 @@
#define atomic_mb_set(ptr, i) do { \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val = (i); \
__atomic_store(ptr, &_val, __ATOMIC_SEQ_CST); \
__atomic_store_n(ptr, i, __ATOMIC_SEQ_CST); \
} while(0)
#endif
@ -179,17 +173,15 @@
#define atomic_xchg(ptr, i) ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof_strip_qual(*ptr) _new = (i), _old; \
__atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \
_old; \
__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_strip_qual(*ptr) _old = (old), _new = (new); \
__atomic_compare_exchange(ptr, &_old, &_new, false, \
typeof_strip_qual(*ptr) _old = (old); \
__atomic_compare_exchange_n(ptr, &_old, new, false, \
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
_old; \
})