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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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33
qemu/include/qemu/atomic.h
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@ -60,14 +60,13 @@ void _ReadWriteBarrier(void);
*/ */
#define atomic_read(ptr) \ #define atomic_read(ptr) \
({ \ ({ \
typeof(*ptr) _val; \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ __atomic_load_n(ptr, __ATOMIC_RELAXED); \
_val; \
}) })
#define atomic_set(ptr, i) do { \ #define atomic_set(ptr, i) do { \
typeof(*ptr) _val = (i); \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \ __atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
} while(0) } while(0)
/* See above: most compilers currently treat consume and acquire the /* See above: most compilers currently treat consume and acquire the
@ -84,14 +83,15 @@ void _ReadWriteBarrier(void);
#define atomic_rcu_read(ptr) \ #define atomic_rcu_read(ptr) \
({ \ ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \ typeof(*ptr) _val; \
atomic_rcu_read__nocheck(ptr, &_val); \ atomic_rcu_read__nocheck(ptr, &_val); \
_val; \ _val; \
}) })
#define atomic_rcu_set(ptr, i) do { \ #define atomic_rcu_set(ptr, i) do { \
typeof(*ptr) _val = (i); \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store(ptr, &_val, __ATOMIC_RELEASE); \ __atomic_store_n(ptr, i, __ATOMIC_RELEASE); \
} while(0) } while(0)
/* atomic_mb_read/set semantics map Java volatile variables. They are /* atomic_mb_read/set semantics map Java volatile variables. They are
@ -105,6 +105,7 @@ void _ReadWriteBarrier(void);
#if defined(_ARCH_PPC) #if defined(_ARCH_PPC)
#define atomic_mb_read(ptr) \ #define atomic_mb_read(ptr) \
({ \ ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \ typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \ __atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
smp_rmb(); \ smp_rmb(); \
@ -112,22 +113,23 @@ void _ReadWriteBarrier(void);
}) })
#define atomic_mb_set(ptr, i) do { \ #define atomic_mb_set(ptr, i) do { \
typeof(*ptr) _val = (i); \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
smp_wmb(); \ smp_wmb(); \
__atomic_store(ptr, &_val, __ATOMIC_RELAXED); \ __atomic_store_n(ptr, i, __ATOMIC_RELAXED); \
smp_mb(); \ smp_mb(); \
} while(0) } while(0)
#else #else
#define atomic_mb_read(ptr) \ #define atomic_mb_read(ptr) \
({ \ ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _val; \ typeof(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \ __atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
_val; \ _val; \
}) })
#define atomic_mb_set(ptr, i) do { \ #define atomic_mb_set(ptr, i) do { \
typeof(*ptr) _val = (i); \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_store(ptr, &_val, __ATOMIC_SEQ_CST); \ __atomic_store_n(ptr, i, __ATOMIC_SEQ_CST); \
} while(0) } while(0)
#endif #endif
@ -135,18 +137,17 @@ void _ReadWriteBarrier(void);
/* All the remaining operations are fully sequentially consistent */ /* All the remaining operations are fully sequentially consistent */
#define atomic_xchg(ptr, i) ({ \ #define atomic_xchg(ptr, i) ({ \
typeof(*ptr) _new = (i), _old; \ QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
__atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \ __atomic_exchange_n(ptr, i, __ATOMIC_SEQ_CST); \
_old; \
}) })
/* Returns the eventual value, failed or not */ /* Returns the eventual value, failed or not */
#define atomic_cmpxchg(ptr, old, new) \ #define atomic_cmpxchg(ptr, old, new) \
({ \ ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
typeof(*ptr) _old = (old), _new = (new); \ 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); \ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
_old; \
}) })
/* Provide shorter names for GCC atomic builtins, return old value */ /* Provide shorter names for GCC atomic builtins, return old value */