Date: Wed, 14 Jan 2004 06:51:43 +0200 From: Alex Lyashkov <shadow@psoft.net> To: Stefan Farfeleder <stefan@fafoe.narf.at> Cc: cvs-src@FreeBSD.org Subject: Re: cvs commit: src/sys/libkern ffs.c ffsl.c fls.c flsl.c Message-ID: <200401140651.45971.shadow@psoft.net> In-Reply-To: <20040113193300.GB626@wombat.fafoe.narf.at> References: <200401131602.i0DG2Khx064321@repoman.freebsd.org> <20040113193300.GB626@wombat.fafoe.narf.at>
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On Tuesday 13 January 2004 21:33, Stefan Farfeleder wrote:
> On Tue, Jan 13, 2004 at 08:02:20AM -0800, Dag-Erling Smorgrav wrote:
> > des 2004/01/13 08:02:20 PST
> >
> > FreeBSD src repository
> >
> > Modified files:
> > sys/libkern ffs.c ffsl.c fls.c flsl.c
> > Log:
> > Cast to unsigned to avoid sign-extension problems.
> >
> > Revision Changes Path
> > 1.9 +1 -1 src/sys/libkern/ffs.c
> > 1.2 +1 -1 src/sys/libkern/ffsl.c
> > 1.2 +1 -1 src/sys/libkern/fls.c
> > 1.2 +1 -1 src/sys/libkern/flsl.c
>
> @@ -47,6 +47,6 @@ ffs(int mask)
> if (mask == 0)
> return (0);
> for (bit = 1; !(mask & 1); bit++)
> - mask >>= 1;
> + (unsigned int)mask >>= 1;
> return (bit);
> }
>
> This is an ugly GCC extension. Might I suggest using the portable
>
> mask = (unsigned int)mask >> 1;
>
> instead?
>
can be use asm inline instred this circle ?
/**
* find_next_bit - find the first set bit in a memory region
* @addr: The address to base the search on
* @offset: The bitnumber to start searching at
* @size: The maximum size to search
*/
static __inline__ int find_next_bit (void * addr, int size, int offset)
{
unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
int set = 0, bit = offset & 31, res;
if (bit) {
/*
* Look for nonzero in the first 32 bits:
*/
__asm__("bsfl %1,%0\n\t"
"jne 1f\n\t"
"movl $32, %0\n"
"1:"
: "=r" (set)
: "r" (*p >> bit));
if (set < (32 - bit))
return set + offset;
set = 32 - bit;
p++;
}
/*
* No set bit yet, search remaining full words for a bit
*/
res = find_first_bit (p, size - 32 * (p - (unsigned long *) addr));
return (offset + set + res);
}
--
With best regards,
Alex
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