icd: add likely()/unlikely()
They will be expanded to __builtin_expect(...) on gcc.
diff --git a/icd/common/icd-utils.h b/icd/common/icd-utils.h
index c8eedea..5304d15 100644
--- a/icd/common/icd-utils.h
+++ b/icd/common/icd-utils.h
@@ -40,6 +40,14 @@
#define U_ASSERT_ONLY
#endif
+#if defined(__GNUC__)
+#define likely(x) __builtin_expect(!!(x), 1)
+#define unlikely(x) __builtin_expect(!!(x), 0)
+#else
+#define likely(x) (x)
+#define unlikely(x) (x)
+#endif
+
#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
#define u_popcount(u) __builtin_popcount(u)