Signed-off-by: Ola Liljedahl <[email protected]>
---
(This document/code contribution attached is provided under the terms of
agreement LES-LTM-21309)
odp_atomic_internal.h is updated with operations (e.g. exchange, compare-and-
exchange) on 16-byte atomics (_odp_atomic_u128_t atomic type with corresponding
_uint128_t scalar type).
GCC on x86-64 requires the compiler flag -mcx16 to enable support for 16-byte
atomics.
Some minor changes to the comments.
.../linux-generic/include/odp_atomic_internal.h | 72 ++++++++++++++++++++--
1 file changed, 66 insertions(+), 6 deletions(-)
diff --git a/platform/linux-generic/include/odp_atomic_internal.h
b/platform/linux-generic/include/odp_atomic_internal.h
index 38b0de0..25da2cd 100644
--- a/platform/linux-generic/include/odp_atomic_internal.h
+++ b/platform/linux-generic/include/odp_atomic_internal.h
@@ -320,9 +320,10 @@ static inline uint64_t
_odp_atomic_u64_xchg_mm(odp_atomic_u64_t *ptr,
* @param ptr Pointer to a 64-bit atomic variable
* @param exp_p Pointer to expected value (updated on failure)
* @param val New value to write
- * @param succ Memory model associated with a successful compare-and-swap
+ * @param succ Memory model associated with a successful compare-and-swap
+ * operation
+ * @param fail Memory model associated with a failed compare-and-swap
* operation
- * @param fail Memory model associated with a failed compare-and-swap operation
*
* @return 1 (true) if exchange successful, 0 (false) if not successful (and
* '*exp_p' updated with current value)
@@ -511,9 +512,9 @@ static inline void *_odp_atomic_ptr_xchg(_odp_atomic_ptr_t
*ptr,
* @param ptr Pointer to a pointer atomic variable
* @param exp_p Pointer to expected value (updated on failure)
* @param val New value to write
- * @param succ Memory model associated with a successful compare-and-swap
+ * @param succ Memory model associated with a successful compare-and-swap
* operation
- * @param fail Memory model associated with a failed compare-and-swap
+ * @param fail Memory model associated with a failed compare-and-swap
* operation
*
* @return 1 (true) if exchange successful, 0 (false) if not successful (and
@@ -541,7 +542,7 @@ static inline int
_odp_atomic_ptr_cmp_xchg_strong(_odp_atomic_ptr_t *ptr,
*****************************************************************************/
/**
- * Initialize a flag atomic variable
+ * Initialize an atomic flag variable
*
* @param ptr Pointer to a flag atomic variable
* @param val The initial value (true or false) of the variable
@@ -568,7 +569,8 @@ static inline int _odp_atomic_flag_load(_odp_atomic_flag_t
*ptr)
/**
* Test-and-set of atomic flag variable
* @Note Operation has acquire memory model. It pairs with a later
- * release operation in some thread.
+ * release operation in some thread. It does not provide release or
+ * acquire/release semantics.
*
* @param ptr Pointer to a flag atomic variable
* @return The old value (true or false) of the variable
@@ -591,6 +593,64 @@ static inline void
_odp_atomic_flag_clear(_odp_atomic_flag_t *ptr)
__atomic_clear(ptr, __ATOMIC_RELEASE);
}
+/* Check if target and compiler supports 128-bit scalars and corresponding
+ * exchange and CAS operations */
+/* GCC on x86-64 needs -mcx16 compiler option */
+#if defined __SIZEOF_INT128__ && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16
+
+/** Preprocessor symbol that indicates support for 128-bit atomics */
+#define ODP_ATOMIC_U128
+
+/** An unsigned 128-bit (16-byte) scalar type */
+typedef __int128 _uint128_t;
+
+/** Atomic 128-bit type */
+typedef struct {
+ _uint128_t v; /**< Actual storage for the atomic variable */
+} _odp_atomic_u128_t ODP_ALIGNED(16);
+
+/**
+ * 16-byte atomic exchange operation
+ *
+ * @param ptr Pointer to a 16-byte atomic variable
+ * @param val_p Pointer to new value to write
+ * @param old_p Pointer to location for old value
+ * @param mmodel Memory model associated with the exchange operation
+ */
+static inline void _odp_atomic_u128_xchg_mm(_odp_atomic_u128_t *ptr,
+ _uint128_t *val_p,
+ _uint128_t *old_p,
+ _odp_memmodel_t mm)
+{
+ __atomic_exchange(&ptr->v, val_p, old_p, mm);
+}
+
+/**
+ * Atomic compare and exchange (swap) of 16-byte atomic variable
+ * "Strong" semantics, will not fail spuriously.
+ *
+ * @param ptr Pointer to a 16-byte atomic variable
+ * @param exp_p Pointer to expected value (updated on failure)
+ * @param val_p Pointer to new value to write
+ * @param succ Memory model associated with a successful compare-and-swap
+ * operation
+ * @param fail Memory model associated with a failed compare-and-swap
+ * operation
+ *
+ * @return 1 (true) if exchange successful, 0 (false) if not successful (and
+ * '*exp_p' updated with current value)
+ */
+static inline int _odp_atomic_u128_cmp_xchg_mm(_odp_atomic_u128_t *ptr,
+ _uint128_t *exp_p,
+ _uint128_t *val_p,
+ _odp_memmodel_t succ,
+ _odp_memmodel_t fail)
+{
+ return __atomic_compare_exchange(&ptr->v, exp_p, val_p,
+ false/*strong*/, succ, fail);
+}
+#endif
+
/**
* @}
*/
--
1.9.1
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