Re: [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h

[Richard Henderson <rth@twiddle.net>]

On Wed, Jan 25, 2006 at 08:02:50PM +0000, Russell King wrote:
> > +   s = 16; if (word << 16 != 0) s = 0; b += s; word >>= s;
> > +   s =  8; if (word << 24 != 0) s = 0; b += s; word >>= s;
> > +   s =  4; if (word << 28 != 0) s = 0; b += s; word >>= s;
...
> Basically, shifts which depend on a variable are more expensive than
> constant-based shifts.

Actually, they're all constant shifts.  Just written stupidly.


r~