[PATCH 1/3] Fix Unlikely(x) == y
Roel Kluin
12o3l at tiscali.nl
Tue Feb 19 01:59:48 EST 2008
David Howells wrote:
> Geert Uytterhoeven <Geert.Uytterhoeven at sonycom.com> wrote:
>
>> Hence shouldn't we ask the gcc people what's the purpose of
>> __builtin_expect(), if it doesn't live up to its promise?
>
> __builtin_expect() is useful on FRV where you _have_ to give each branch and
> conditional branch instruction a measure of probability whether the branch
> will be taken.
>
> David
I was wondering whether some of the uses of likely illustrated below are
incorrect or not useful.
x = likely(X) || Y
for ( ... ; likely(...); ... )
while ( likely(X) )
if ( unlikely(X) &&/|| likely(Y) )
if ( X &&/|| unlikely(Y) )
return likely(X);
return likely(X) ? a : b;
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