linux-next: x86-latest/powerpc-next merge conflict

Paul Mackerras paulus at samba.org
Mon Apr 21 22:13:06 EST 2008


Alexander van Heukelum writes:

> Powerpc would pick up an optimized version via this chain: generic fls64
> ->
> powerpc __fls --> __ilog2 --> asm (PPC_CNTLZL "%0,%1" : "=r" (lz) : "r"
> (x)).

Why wouldn't powerpc continue to use the fls64 that I have in there
now?

> However, the generic version of fls64 first tests the argument for zero.
> From
> your code I derive that the count-leading-zeroes instruction for
> argument zero
> is defined as cntlzl(0) == BITS_PER_LONG.

That is correct.  If the argument is 0 then all of the zero bits are
leading zeroes. :)

Regards,
Paul.



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