| Date | Fri, 24 Apr 1998 11:52:25 -0700 | From | "David S. Miller" <> | Subject | Re: patch parport/bitops |
| |
Date: Fri, 24 Apr 1998 19:27:20 +0200 From: Thomas Sailer <sailer@ife.ee.ethz.ch>
hweight32/hweight16/hweight8 these count the number of bits set in an N-bit word. The reason why I believe this should be in an arch specific directory is because most archs (other than i386, sparc pre v9 popc enhanced) have instructions to do this. The reason there are 3 funcs to do this is because the generic implementation is slightly costly and the cost is lower with less bits.
No actual Sparc-V9 implementations, even UltraSparc, implement the popc instruction in hardware, it must be emulated via software trap on the "unimp" exception on all chips. Yes, this ticked me off too because you can do ffz in constant time with that toy ;-)
Later, David S. Miller davem@dm.cobaltmicro.com
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu
|