linux-kernel - Re: [PATCH v2 2/3] word-at-a-time.h: support zero

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Date:	Wed, 7 Oct 2015 07:53:20 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Michael Cree <mcree@...on.net.nz>,
	Matt Turner <mattst88@...il.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	linux-alpha@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] word-at-a-time.h: support zero_bytemask() on
 alpha and tile


* Chris Metcalf <cmetcalf@...hip.com> wrote:

> Both alpha and tile needed implementations of zero_bytemask.
> 
> The alpha version is untested.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>
> ---
>  arch/alpha/include/asm/word-at-a-time.h | 2 ++
>  arch/tile/include/asm/word-at-a-time.h  | 8 +++++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/alpha/include/asm/word-at-a-time.h b/arch/alpha/include/asm/word-at-a-time.h
> index 6b340d0f1521..902e6ab00a06 100644
> --- a/arch/alpha/include/asm/word-at-a-time.h
> +++ b/arch/alpha/include/asm/word-at-a-time.h
> @@ -52,4 +52,6 @@ static inline unsigned long find_zero(unsigned long bits)
>  #endif
>  }
>  
> +#define zero_bytemask(mask) ((2ul << (find_zero(mask) * 8)) - 1)

Small nit: please use a proper C inline function instead of CPP, as for example 
the PowerPC zero_bytemask() function is.

> -/* Generate 0x01 byte values for non-zero bytes using a SIMD instruction. */
> +/* Generate 0x01 byte values for zero bytes using a SIMD instruction. */
>  static inline unsigned long has_zero(unsigned long val, unsigned long *data,
>  				     const struct word_at_a_time *c)
>  {
> @@ -33,4 +33,10 @@ static inline long find_zero(unsigned long mask)
>  #endif
>  }
>  
> +#ifdef __BIG_ENDIAN
> +#define zero_bytemask(mask) (~1ul << (63 - __builtin_clzl(mask)))
> +#else
> +#define zero_bytemask(mask) ((2ul << __builtin_ctzl(mask)) - 1)
> +#endif

Ditto.

Other than that, for the whole series:

  Reviewed-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo
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