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

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Message-ID: <481AA10C.9080705@zytor.com>
Date:	Thu, 01 May 2008 22:05:16 -0700
From:	"H. Peter Anvin" <hpa@...or.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:
> Hello everybody,
> The swapping method (in function void u32_swap() line no.. 14 to 16) in lib/sort.c can be improved by using the following code
> *(u32 *)b ^= *(u32 *)a ^= *(u32 *)b ^= *(u32 *)a instead of the code given. This code
> is not using third variable thus not consuming another memory. And I dont see any significance in
> using *int size* argument. so the function should be
> static void u32_swap(void *a, void *b)
> {
>     *(u32 *)b ^= *(u32 *)a ^= *(u32 *)b ^= *(u32 *)a;
> }
> 

Not only is this invalid C, but it produces massively worse code.

	-hpa
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