misc replication bugfixes including some needed modifications in IO_CACHE

likely() and unlikely() branch prediction compiler hint macros
clean-up of comments

2 files changed, 19 insertions, 2 deletions

diff --git a/include/my_global.h b/include/my_global.h
index 7277bdcd715..40e70c521eb 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -51,6 +51,22 @@
 #endif
 #endif /* _WIN32... */
 
+/* The macros below are borrowed from include/linux/compiler.h in the
+   Linux kernel. Use them to indicate the likelyhood of the truthfulness
+   of a condition. This serves two purposes - newer versions of gcc will be
+   able to optimize for branch predication, which could yield siginficant
+   performance gains in frequently executed sections of the code, and the
+   other reason to use them is for documentation
+*/
+
+#if __GNUC__ == 2 && __GNUC_MINOR__ < 96
+#define __builtin_expect(x, expected_value) (x)
+#endif
+
+#define likely(x)	__builtin_expect((x),1)
+#define unlikely(x)	__builtin_expect((x),0)
+
+
 /* Fix problem with S_ISLNK() on Linux */
 #if defined(HAVE_LINUXTHREADS)
 #undef  _GNU_SOURCE
diff --git a/include/my_sys.h b/include/my_sys.h
index 1d7c0b7ddb1..61f93d665cd 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -436,8 +436,9 @@ typedef int (*qsort2_cmp)(const void *, const void *, const void *);
 
 #define my_b_tell(info) ((info)->pos_in_file + \
 			 (uint) (*(info)->current_pos - (info)->request_pos))
-#define my_b_append_tell(info) ((info)->end_of_file + \
-			 (uint) ((info)->write_pos - (info)->write_buffer))
+
+/* tell write offset in the SEQ_APPEND cache */
+my_off_t my_b_append_tell(IO_CACHE* info);
 
 #define my_b_bytes_in_cache(info) (uint) (*(info)->current_end - \
 					  *(info)->current_pos)