Re: Linux 2.4.10-pre11 -- __builtin_expect

James Antill
2001-09-26T23:55:36Z

Andi Kleen <ak@suse.de> writes:

> Good point. I somehow assumed that __builtin_expect would just signify
> a boolean, but if I read gcc source correctly this was wrong.

Yeh, it's a long so you'll get no cast warnings too.

> Here is an updated patch.

[snip ... ]

> --- include/linux/kernel.h-LIKELY Tue Sep 18 11:12:20 2001
> +++ include/linux/kernel.h Tue Sep 18 14:35:17 2001
> @@ -171,4 +171,14 @@
> char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
> };
>
> +
> +/* This loses on a few early 2.96 snapshots, but hopefully nobody uses them anymore. */
> +#if __GNUC__ > 2 || (__GNUC__ == 2 && _GNUC_MINOR__ == 96)
> +#define likely(x) __builtin_expect(!!(x), 1)
> +#define unlikely(x) __builtin_expect((x), 0)

unlikely() also needs to be...

#define unlikely(x) __builtin_expect(!(x), 1)

...or...

#define unlikely(x) __builtin_expect(!!(x), 0)

> +#else
> +#define likely(x) (x)
> +#define unlikely(x) (x)
> +#endif
> +
> #endif

--
# James Antill -- james@and.org
:0:
* ^From: .*james@and\.org
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