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Re: Importing Flash and NAND subsystem for NetBSD
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
popcnt != clz
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.
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