linux-ext4 - Re: [PATCH] lib/ext2fs: Use __builtin_popcount when available Signed-off-by: Cristian Rodríguez <crrodriguez@...nsuse.org>

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Message-ID: <20130107015607.GC12838@thunk.org>
Date:	Sun, 6 Jan 2013 20:56:07 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Cristian Rodríguez <crrodriguez@...nsuse.org>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] lib/ext2fs: Use __builtin_popcount when available Signed-off-by: Cristian Rodríguez <crrodriguez@...nsuse.org>

On Sun, Jan 06, 2013 at 10:46:34PM -0300, Cristian Rodríguez wrote:
> 
> with a recent compiler it goes something like this..

Actually, that's less ugly than I feared...  if we wanted to pretty it
up a little, we could simply omit the __get_cpuid() bit, since that's
x86 specific, and just use the __builtin_cpu_supports() if it is
available on gcc 4.8 and newer.  If it is not available, we could just
always use the software version of popcnt, since it's really not that
bad.

What about the people who prefer to use clang instad of gcc; does
clang have support for any of this magic?

Cheers,

					- Ted
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