1 files changed, 79 insertions, 0 deletions
diff --git a/util/atomicops.h b/util/atomicops.h
new file mode 100644
index 0000000..11c1196
--- /dev/null
+++ b/util/atomicops.h
@@ -0,0 +1,79 @@
+// 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__
+
+#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");
+}
+
+#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, must one
+// use read barriers for the readers too.
+#if defined(__alpha__)
+
+static inline void MaybeReadMemoryBarrier() {
+  __asm__ __volatile__("mb" : : : "memory");
+}
+
+#else
+
+static inline void MaybeReadMemoryBarrier() {}
+
+#endif // __alpha__
+
+#endif  // RE2_UTIL_ATOMICOPS_H__