Add CRYPTOPP_LIKELY and CRYPTOPP_UNLIKELY macros

misc.h

@@ -114,6 +114,18 @@ NAMESPACE_BEGIN(CryptoPP)
 // Forward declaration for IntToString specialization
 class Integer;
 
+// ************** branch prediction ***************
+
+// Micro-optimization, use juditiously. Be sure you find a hotspot
+// using 'make coverage', and its in a tight loop. Otherwise, DFW.
+#if defined(__GNUC__)
+# define CRYPTOPP_LIKELY(x)    __builtin_expect(!!(x), 1)
+# define CRYPTOPP_UNLIKELY(x)  __builtin_expect(!!(x), 0)
+#else
+# define CRYPTOPP_LIKELY(x)    (x)
+# define CRYPTOPP_UNLIKELY(x)  (x)
+#endif
+
 // ************** compile-time assertion ***************
 
 #if CRYPTOPP_DOXYGEN_PROCESSING