linux-kernel - Re: [PATCH] MPILIB: Provide count_leading/trailing

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Date:	Fri, 20 Jul 2012 22:02:28 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	David Howells <dhowells@...hat.com>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>
Subject: Re: [PATCH] MPILIB: Provide count_leading/trailing_zeros() based on arch functions

On Friday 20 July 2012, David Howells wrote:
> 
> Arnd Bergmann <arnd@...db.de> 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().

	Arnd
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