Import likely/unlikely from PostgreSQL.

These macros are not only useful to enhance performance (if correctly
used) but make porting codes from PostgreSQL to pgpool easier since
the macros occasionally used in the code.

Discussion: [pgpool-hackers: 4599] Porting likely/unlikely
https://www.pgpool.net/pipermail/pgpool-hackers/2025-May/004600.html

diff --git a/src/include/pool_type.h b/src/include/pool_type.h
index 43f29a595abff8f7883b7c6e0087a518fa7e30ff..d7cdf936a16b92682f5533c91314cb9c3a8b61ff 100644 (file)
--- 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 */