diff --git a/src/include/pool_type.h b/src/include/pool_type.h
index 43f29a595..d7cdf936a 100644
--- a/src/include/pool_type.h
+++ b/src/include/pool_type.h
@@ -500,4 +500,19 @@ typedef void (*pg_on_exit_callback) (int code, Datum arg);
 	} while (0)
 
 
+/*
+ * Hints to the compiler about the likelihood of a branch. Both likely() and
+ * unlikely() return the boolean value of the contained expression.
+ *
+ * These should only be used sparingly, in very hot code paths. It's very easy
+ * to mis-estimate likelihoods.
+ */
+#if __GNUC__ >= 3
+#define likely(x)	__builtin_expect((x) != 0, 1)
+#define unlikely(x) __builtin_expect((x) != 0, 0)
+#else
+#define likely(x)	((x) != 0)
+#define unlikely(x) ((x) != 0)
+#endif
+
 #endif							/* POOL_TYPE_H */