linux-kernel - Re: Improved Swapping Method In sort.c

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Message-ID: <4818BE97.7030307@davidnewall.com>
Date:	Thu, 01 May 2008 04:16:47 +0930
From:	David Newall <davidn@...idnewall.com>
To:	Soumyadip Das Mahapatra <dip_kernel@...oo.co.in>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Improved Swapping Method In sort.c

Soumyadip Das Mahapatra wrote:
> static void u32_swap(void *a, void *b)
> {
>     *(u32 *)b ^= *(u32 *)a ^= *(u32 *)b ^= *(u32 *)a;
> }
>   

That was posted to comp.lang.c 20 years ago or more.  It's not something
that the compiler is likely to be able to optimize (unlike the normal
swap, using a temporary variable.)

Another cute, temp-free swap, from the same era, is: b += a -= b; a = b - a.
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