linux-kernel - Re: [PATCH] ubi: kill homegrown endian macros

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Message-ID: <20070517212641.GU4095@ftp.linux.org.uk>
Date:	Thu, 17 May 2007 22:26:41 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	dedekind@...radead.org, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] ubi: kill homegrown endian macros

On Thu, May 17, 2007 at 09:42:34PM +0100, Al Viro wrote:
> Ahem...  So what does
> 	x |= y;
> turns into with that approach?

Another case is

#define FLAG1 cpu_to_be32(2)
#define FLAG2 cpu_to_be32(0x400)

	if (packet_header->field & (FLAG1 | FLAG2))
		....

which is a bloody common idiom in net/* and it happens on some pretty hot
paths.  Approaches that would require converting it to something like
	if (be32_to_cpu(packet_header->field) & (FLAG1 | FLAG2))
would be not just obnoxious, they would actually generate worse code.
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