Re: [Libguestfs] [PATCH libnbd] lib: Use GCC hints to move debug and error handling code out of hot paths.

--- generator/generator | 6 +++--- lib/crypto.c | 2 +- lib/internal.h | 14 +++++++++++++- 3 files changed, 17 insertions(+), 5 deletions(-)

+++ b/lib/internal.h @@ -40,6 +40,18 @@ #include "states.h" #include "unlocked.h" +/* Define unlikely macro, but only for GCC. These are used to move + * debug and error handling code out of hot paths, making the hot path + * into common functions use less instruction cache. + */ +#if defined(__GNUC__) +#define unlikely(x) __builtin_expect (!!(x), 0) +#define if_debug(h) if (unlikely ((h)->debug)) +#else +#define unlikely(x) (x) +#define if_debug(h) if ((h)->debug) +#endif