From: Nicolai Hähnle <nicolai.haeh...@amd.com>
The closest to it in the old-style gcc builtins is __sync_lock_test_and_set,
however, that is only guaranteed to work with values 0 and 1 and only
provides an acquire barrier. I also don't know about other OSes, so we
provide a simple & stupid emulation via p_atomic_cmpxchg.
---
src/util/u_atomic.h | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/src/util/u_atomic.h b/src/util/u_atomic.h
index 2a5bbae295b..c6d4bde3439 100644
--- a/src/util/u_atomic.h
+++ b/src/util/u_atomic.h
@@ -5,20 +5,21 @@
* No copyright claimed on this file.
*
*/
#include "no_extern_c.h"
#ifndef U_ATOMIC_H
#define U_ATOMIC_H
#include <stdbool.h>
+#include <stdint.h>
/* Favor OS-provided implementations.
*
* Where no OS-provided implementation is available, fall back to
* locally coded assembly, compiler intrinsic or ultimately a
* mutex-based implementation.
*/
#if defined(__sun)
#define PIPE_ATOMIC_OS_SOLARIS
#elif defined(_MSC_VER)
@@ -40,20 +41,22 @@
/* The builtins with explicit memory model are available since GCC 4.7. */
#define p_atomic_set(_v, _i) __atomic_store_n((_v), (_i), __ATOMIC_RELEASE)
#define p_atomic_read(_v) __atomic_load_n((_v), __ATOMIC_ACQUIRE)
#define p_atomic_dec_zero(v) (__atomic_sub_fetch((v), 1, __ATOMIC_ACQ_REL) ==
0)
#define p_atomic_inc(v) (void) __atomic_add_fetch((v), 1, __ATOMIC_ACQ_REL)
#define p_atomic_dec(v) (void) __atomic_sub_fetch((v), 1, __ATOMIC_ACQ_REL)
#define p_atomic_add(v, i) (void) __atomic_add_fetch((v), (i),
__ATOMIC_ACQ_REL)
#define p_atomic_inc_return(v) __atomic_add_fetch((v), 1, __ATOMIC_ACQ_REL)
#define p_atomic_dec_return(v) __atomic_sub_fetch((v), 1, __ATOMIC_ACQ_REL)
+#define p_atomic_xchg(v, i) __atomic_exchange_n((v), (i), __ATOMIC_ACQ_REL)
+#define PIPE_NATIVE_ATOMIC_XCHG
#else
#define p_atomic_set(_v, _i) (*(_v) = (_i))
#define p_atomic_read(_v) (*(_v))
#define p_atomic_dec_zero(v) (__sync_sub_and_fetch((v), 1) == 0)
#define p_atomic_inc(v) (void) __sync_add_and_fetch((v), 1)
#define p_atomic_dec(v) (void) __sync_sub_and_fetch((v), 1)
#define p_atomic_add(v, i) (void) __sync_add_and_fetch((v), (i))
#define p_atomic_inc_return(v) __sync_add_and_fetch((v), 1)
@@ -213,13 +216,40 @@
sizeof(*v) == sizeof(uint32_t) ? atomic_cas_32((uint32_t *)(v),
(uint32_t)(old), (uint32_t)(_new)) : \
sizeof(*v) == sizeof(uint64_t) ? atomic_cas_64((uint64_t *)(v),
(uint64_t)(old), (uint64_t)(_new)) : \
(assert(!"should not get here"), 0))
#endif
#ifndef PIPE_ATOMIC
#error "No pipe_atomic implementation selected"
#endif
-
+#ifndef PIPE_NATIVE_ATOMIC_XCHG
+static inline uint32_t p_atomic_xchg_32(uint32_t *v, uint32_t i)
+{
+ uint32_t actual = p_atomic_read(v);
+ uint32_t expected;
+ do {
+ expected = actual;
+ actual = p_atomic_cmpxchg(v, expected, i);
+ } while (expected != actual);
+ return actual;
+}
+
+static inline uint64_t p_atomic_xchg_64(uint64_t *v, uint64_t i)
+{
+ uint64_t actual = p_atomic_read(v);
+ uint64_t expected;
+ do {
+ expected = actual;
+ actual = p_atomic_cmpxchg(v, expected, i);
+ } while (expected != actual);
+ return actual;
+}
+
+#define p_atomic_xchg(v, i) ((__typeof(*(v))) \
+ sizeof(*(v)) == sizeof(uint32_t) ? p_atomic_xchg_32((uint32_t *)(v),
(uint32_t)(i)) : \
+ sizeof(*(v)) == sizeof(uint64_t) ? p_atomic_xchg_64((uint64_t *)(v),
(uint64_t)(i)) : \
+ (assert(!"should not get here"), 0))
+#endif
#endif /* U_ATOMIC_H */
--
2.11.0
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