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Re: [PATCH] byteswap-16.h: USe __builtin_bswap16 in gcc 4.8

From: Carlos O'Donell <carlos at systemhalted dot org>
To: Roland McGrath <roland at hack dot frob dot com>
Cc: Cristian Rodríguez <crrodriguez at opensuse dot org>, libc-alpha at sourceware dot org
Date: Mon, 07 Jan 2013 16:50:19 -0500
Subject: Re: [PATCH] byteswap-16.h: USe __builtin_bswap16 in gcc 4.8
References: <1357593252-17153-1-git-send-email-crrodriguez@opensuse.org> <20130107214644.7E7712C0D6@topped-with-meat.com>

On 01/07/2013 04:46 PM, Roland McGrath wrote:
> We won't include such a change until 4.8 is actually released (or very
> close ot it).  Before that, there is no real guarantee what things are
> or aren't assumable from __GNUC_PREREQ (4, 8).

Consensus seems to be that we don't want to use __GNUC_PREREQ, 
rather we should test for __builtin_bswap16, set a feature macro,
and then enable the optimization based on the feature macro.

This makes it easier to cleanup later when we no longer need feature X,
we just look for uses of the feature macro rather than having to grovel
through all of the __GNUC_PREREQ logic.

Nobody has stepped up to do the first one :-)

Cheers,
Carlos.

References:
- [PATCH] byteswap-16.h: USe __builtin_bswap16 in gcc 4.8
  - From: Cristian RodrÃguez
- Re: [PATCH] byteswap-16.h: USe __builtin_bswap16 in gcc 4.8
  - From: Roland McGrath

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