cvs commit: src/sys/sys cdefs.h

David Schultz das at FreeBSD.ORG
Tue Sep 30 23:16:45 PDT 2003

On Tue, Sep 30, 2003, Maxime Henrion wrote:
> mux         2003/09/30 13:45:14 PDT
>   FreeBSD src repository
>   Modified files:
>     sys/sys              cdefs.h 
>   Log:
>   Introduce new __predict_false(exp) and __predict_true(exp) keywords.
>   Their purpose is to give explicit hints to the compiler to judge
>   the likelyhood of a test to succeed or fail.  Not all architectures
>   have support for such optimizations, but for those who do, it can
>   give a nice performance improvement in hot loops.
>   Obviously, this should be used very rarely in very specific code.
>   Reviewed by:    peter
>   Obtained from:  OpenBSD

Cool, I'm glad we finally have these.  (FWIW, I believe the macros
originated with NetBSD.)  Hopefully they will be used with reservation.

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