Add ARM64 (aarch64) support to s_lock.h.

Use the same gcc atomic functions as we do on newer ARM chips.
(Basically this is a copy and paste of the __arm__ code block,
but omitting the SWPB option since that definitely won't work.)

Back-patch to 9.2.  The patch would work further back, but we'd also
need to update config.guess/config.sub in older branches to make them
build out-of-the-box, and there hasn't been demand for it.

Mark Salter

src/include/storage/s_lock.h

@@ -336,6 +336,29 @@ tas(volatile slock_t *lock)
 #endif	 /* __arm__ */
 
 
+/*
+ * On ARM64, we use __sync_lock_test_and_set(int *, int) if available.
+ */
+#if defined(__aarch64__) || defined(__aarch64)
+#ifdef HAVE_GCC_INT_ATOMICS
+#define HAS_TEST_AND_SET
+
+#define TAS(lock) tas(lock)
+
+typedef int slock_t;
+
+static __inline__ int
+tas(volatile slock_t *lock)
+{
+	return __sync_lock_test_and_set(lock, 1);
+}
+
+#define S_UNLOCK(lock) __sync_lock_release(lock)
+
+#endif	 /* HAVE_GCC_INT_ATOMICS */
+#endif	 /* __aarch64__ */
+
+
 /* S/390 and S/390x Linux (32- and 64-bit zSeries) */
 #if defined(__s390__) || defined(__s390x__)
 #define HAS_TEST_AND_SET