Re: [PATCH] MPILIB: Provide count_leading/trailing_zeros() based on arch functions

From: Arnd Bergmann
Date: Sat Jul 21 2012 - 04:49:45 EST

On Friday 20 July 2012, David Howells wrote:
> Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > I don't generally like to put stuff into asm-generic when it's unlikely
> > to be overridden by architectures. It would really belong into
> > include/linux, but then again we have all the other bitops in asm-generic
> > as well, so whatever...
> Some arches (such as Sparc, I think) have count-leading-zero instructions.

But I guess they would still use the same definition of

+static inline int count_leading_zeros(unsigned long x)
+ if (sizeof(x) == 4)
+ return BITS_PER_LONG - fls(x);
+ else
+ return BITS_PER_LONG - fls64(x);

and just provide their own fls().

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