ClickHouse/contrib/libre2/util/atomicops.h

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// Copyright 2006-2008 The RE2 Authors. All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef RE2_UTIL_ATOMICOPS_H__
#define RE2_UTIL_ATOMICOPS_H__
// The memory ordering constraints resemble the ones in C11.
// RELAXED - no memory ordering, just an atomic operation.
// CONSUME - data-dependent ordering.
// ACQUIRE - prevents memory accesses from hoisting above the operation.
// RELEASE - prevents memory accesses from sinking below the operation.
#if (__clang_major__ * 100 + __clang_minor__ >= 303) || \
(__GNUC__ * 1000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ >= 40801)
#define ATOMIC_LOAD_RELAXED(x, p) do { (x) = __atomic_load_n((p), __ATOMIC_RELAXED); } while (0)
#define ATOMIC_LOAD_CONSUME(x, p) do { (x) = __atomic_load_n((p), __ATOMIC_CONSUME); } while (0)
#define ATOMIC_LOAD_ACQUIRE(x, p) do { (x) = __atomic_load_n((p), __ATOMIC_ACQUIRE); } while (0)
#define ATOMIC_STORE_RELAXED(p, v) __atomic_store_n((p), (v), __ATOMIC_RELAXED)
#define ATOMIC_STORE_RELEASE(p, v) __atomic_store_n((p), (v), __ATOMIC_RELEASE)
#else // old compiler
#define ATOMIC_LOAD_RELAXED(x, p) do { (x) = *(p); } while (0)
#define ATOMIC_LOAD_CONSUME(x, p) do { (x) = *(p); MaybeReadMemoryBarrier(); } while (0)
#define ATOMIC_LOAD_ACQUIRE(x, p) do { (x) = *(p); ReadMemoryBarrier(); } while (0)
#define ATOMIC_STORE_RELAXED(p, v) do { *(p) = (v); } while (0)
#define ATOMIC_STORE_RELEASE(p, v) do { WriteMemoryBarrier(); *(p) = (v); } while (0)
// WriteMemoryBarrier(), ReadMemoryBarrier() and MaybeReadMemoryBarrier()
// are an implementation detail and must not be used in the rest of the code.
#if defined(__i386__)
static inline void WriteMemoryBarrier() {
int x;
__asm__ __volatile__("xchgl (%0),%0" // The lock prefix is implicit for xchg.
:: "r" (&x));
}
#elif defined(__x86_64__)
// 64-bit implementations of memory barrier can be simpler, because
// "sfence" is guaranteed to exist.
static inline void WriteMemoryBarrier() {
__asm__ __volatile__("sfence" : : : "memory");
}
#elif defined(__ppc__)
static inline void WriteMemoryBarrier() {
__asm__ __volatile__("eieio" : : : "memory");
}
#elif defined(__alpha__)
static inline void WriteMemoryBarrier() {
__asm__ __volatile__("wmb" : : : "memory");
}
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#elif defined(__aarch64__)
static inline void WriteMemoryBarrier() {
__asm__ __volatile__("dmb st" : : : "memory");
}
#else
#include "util/mutex.h"
static inline void WriteMemoryBarrier() {
// Slight overkill, but good enough:
// any mutex implementation must have
// a read barrier after the lock operation and
// a write barrier before the unlock operation.
//
// It may be worthwhile to write architecture-specific
// barriers for the common platforms, as above, but
// this is a correct fallback.
re2::Mutex mu;
re2::MutexLock l(&mu);
}
/*
#error Need WriteMemoryBarrier for architecture.
// Windows
inline void WriteMemoryBarrier() {
LONG x;
::InterlockedExchange(&x, 0);
}
*/
#endif
// Alpha has very weak memory ordering. If relying on WriteBarriers, one must
// use read barriers for the readers too.
#if defined(__alpha__)
static inline void MaybeReadMemoryBarrier() {
__asm__ __volatile__("mb" : : : "memory");
}
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#else
static inline void MaybeReadMemoryBarrier() {}
#endif // __alpha__
// Read barrier for various targets.
#if defined(__aarch64__)
static inline void ReadMemoryBarrier() {
__asm__ __volatile__("dmb ld" : : : "memory");
}
#elif defined(__alpha__)
static inline void ReadMemoryBarrier() {
__asm__ __volatile__("mb" : : : "memory");
}
#else
static inline void ReadMemoryBarrier() {}
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#endif
#endif // old compiler
#ifndef NO_THREAD_SAFETY_ANALYSIS
#define NO_THREAD_SAFETY_ANALYSIS
#endif
#endif // RE2_UTIL_ATOMICOPS_H__