[U-Boot] [PATCH] crc32: Correct endianness of crc32 result

Albert ARIBAUD
2013-04-17T19:23:26Z

Hi Simon -- and sorry for the dupe.

On Wed, 17 Apr 2013 11:28:07 -0700, Simon Glass <sjg@chromium.org>
wrote:

> I tried using:
>
> #ifdef USE_HOSTCC
> crc = htobe32(crc);
> #else
> crc = cpu_to_be32(crc);
> #endif
> memcpy(output, &crc, sizeof(crc));
>
>
> This is one instruction (4 bytes, 16%) smaller, but I suspect quite a
> lot slower due to the overhead of a very small memcpy().
>
> 43e2c1d8: e28d1008 add r1, sp, #8
> 43e2c1dc: e3a02004 mov r2, #4
> 43e2c1e0: e6bf0f30 rev r0, r0
> 43e2c1e4: e5210004 str r0, [r1, #-4]!
> 43e2c1e8: e1a00004 mov r0, r4
> 43e2c1ec: eb001af7 bl 43e32dd0 <memcpy>

How about replacing the memcpy with an explicit put_unaligned(),
similar to what was done in

http://www.mail-archive.com/u-boot at lists.denx.de/msg109555.html

with get_unaligned()? The code will be longer than above, but shorter
than the above plus the memcpy(), and faster too -- actually, I'm
surprised that the compiler does not unroll the memcpy() on its own,
considering the size argument is a constant.

> Regards,
> Simon

Amicalement,
--
Albert.