Re: Importing Flash and NAND subsystem for NetBSD

[Matt Thomas <matt%3am-software.com@localhost>]

On Feb 13, 2011, at 12:10 PM, Joerg Sonnenberger wrote:

> On Sun, Feb 13, 2011 at 10:44:45AM -0800, Matt Thomas wrote:
>> CountBitsInByte should be replaced by __builtin_popcount so that
>> machines with a popcount instruction can use it.
> 
> Which ones? There is no assembler version of popcount at the moment.
> SPARC64 doesn't use it for ffs(), the AMD64 one has to be detected via
> CPUID. The libgcc version is pretty bad. But code can use the popcount
> family...

popcnt != clz 

alpha ev6
i386 has a sse2 popcnt
power5 has a popcntb

sparcv9 has one but none of the UltraSparc implement it.

Also, use a count-leading instruction might be useful with
a faster popcount.