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Support GCC and clang versions that lack <stdatomic.h>.

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Add a code path to use the GCC builtins for atomics, which are supported
in older compiler versions, rather than the new <stdatomic.h>.
This commit is contained in:
Dan Gohman
2019-05-26 15:14:41 -07:00
committed by Jakub Konka
parent 60807c5e54
commit 176538b860
1 changed files with 18 additions and 0 deletions
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18
wasmtime-wasi/sandboxed-system-primitives/src/refcount.h
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@@ -13,14 +13,20 @@
#define REFCOUNT_H #define REFCOUNT_H
#include <assert.h> #include <assert.h>
#if !defined(__GNUC__)
#include <stdatomic.h> #include <stdatomic.h>
#endif
#include <stdbool.h> #include <stdbool.h>
#include "locking.h" #include "locking.h"
// Simple reference counter. // Simple reference counter.
struct LOCKABLE refcount { struct LOCKABLE refcount {
#if defined(__GNUC__)
unsigned count;
#else
atomic_uint count; atomic_uint count;
#endif
}; };
#define PRODUCES(...) LOCKS_SHARED(__VA_ARGS__) NO_LOCK_ANALYSIS #define PRODUCES(...) LOCKS_SHARED(__VA_ARGS__) NO_LOCK_ANALYSIS
@@ -28,18 +34,30 @@ struct LOCKABLE refcount {
// Initialize the reference counter. // Initialize the reference counter.
static void refcount_init(struct refcount *r, unsigned int count) PRODUCES(*r) { static void refcount_init(struct refcount *r, unsigned int count) PRODUCES(*r) {
#if defined(__GNUC__)
__atomic_store_n(&r->count, count, __ATOMIC_SEQ_CST);
#else
atomic_init(&r->count, count); atomic_init(&r->count, count);
#endif
} }
// Increment the reference counter. // Increment the reference counter.
static inline void refcount_acquire(struct refcount *r) PRODUCES(*r) { static inline void refcount_acquire(struct refcount *r) PRODUCES(*r) {
#if defined(__GNUC__)
__atomic_fetch_add(&r->count, 1, __ATOMIC_ACQUIRE);
#else
atomic_fetch_add_explicit(&r->count, 1, memory_order_acquire); atomic_fetch_add_explicit(&r->count, 1, memory_order_acquire);
#endif
} }
// Decrement the reference counter, returning whether the reference // Decrement the reference counter, returning whether the reference
// dropped to zero. // dropped to zero.
static inline bool refcount_release(struct refcount *r) CONSUMES(*r) { static inline bool refcount_release(struct refcount *r) CONSUMES(*r) {
#if defined(__GNUC__)
int old = __atomic_fetch_sub(&r->count, 1, __ATOMIC_RELEASE);
#else
int old = atomic_fetch_sub_explicit(&r->count, 1, memory_order_release); int old = atomic_fetch_sub_explicit(&r->count, 1, memory_order_release);
#endif
assert(old != 0 && "Reference count becoming negative"); assert(old != 0 && "Reference count becoming negative");
return old == 1; return old == 1;
} }