+/* Prefetch into L1 cache for read. */
+#define prefetchr(addr) __builtin_prefetch((addr), 0)
+
+/* Prefetch into L1 cache for write. */
+#define prefetchw(addr) __builtin_prefetch((addr), 1)
+
+/* Declare that the members of the annotated struct are tightly packed, and the
+ * struct itself may be misaligned. */
+#define _packed_attribute __attribute__((packed))
+
+/* Declare that the annotated variable, or variables of the annotated type, are
+ * to be aligned on n-byte boundaries. */
+#define _aligned_attribute(n) __attribute__((aligned(n)))
+
+/* Declare that pointers to the annotated type may alias other pointers. */
+#define _may_alias_attribute __attribute__((may_alias))
+
+/* Hint that the annotated function is rarely called. */
+#if GCC_PREREQ(4, 4) || __has_attribute(cold)
+# define _cold_attribute __attribute__((cold))
+#else