linux-kernel - Re: [PATCH] Using Intel CRC32 instruction to accelerate CRC32c algorithm by new crypto API -V3.

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Date:	Thu, 7 Aug 2008 20:38:35 -0700
From:	"Ulrich Drepper" <drepper@...il.com>
To:	"Austin Zhang" <austin_zhang@...ux.intel.com>
Cc:	herbert@...dor.apana.org.au, bunk@...nel.org, dwmw2@...radead.org,
	davem@...emloft.net, randy.dunlap@...cle.com,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] Using Intel CRC32 instruction to accelerate CRC32c algorithm by new crypto API -V3.

On Tue, Aug 5, 2008 at 10:23 PM, Austin Zhang
<austin_zhang@...ux.intel.com> wrote:
> +#ifdef CONFIG_X86_64
> +#define REX_PRE "0x48, "
> +#define SCALE_F 8
> +#else
> +#define REX_PRE
> +#define SCALE_F 4
> +#endif
[...]
> +static u32 __pure crc32c_intel_le_hw(u32 crc, unsigned char const *p, size_t len)
> +{
> +       unsigned int iquotient = len / SCALE_F;
> +       unsigned int iremainder = len % SCALE_F;
> +       unsigned long *ptmp = (unsigned long *)p;
> +
> +       while (iquotient--) {
> +               __asm__ __volatile__(
> +                       ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
> +                       :"=S"(crc)
> +                       :"0"(crc), "c"(*ptmp)
> +               );
> +               ptmp++;

I think you want to use

  #define SCALE_F sizeof(unsigned long)

Since the loop iteration count etc depends on

   ptmp++

which depends on the type being unsigned long.
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