PATCH: Use __builtin_bswap32/64 for GCC >= 4.2

[Andreas Jaeger]

On 04/06/2012 07:33 PM, H.J. Lu wrote:
> On Thu, Apr 5, 2012 at 11:50 PM, Andreas Jaeger<aj@suse.com>  wrote:
>> On 04/05/2012 10:08 PM, H.J. Lu wrote:
>>>
>>> Hi,
>>>
>>> sysdeps/x86_64/bits/byteswap.h has
>>>
>>> #if defined __GNUC__&&    __GNUC__>= 2
>>>
>>> ..
>>> #else
>>> # define __bswap_32(x) \
>>>       (__extension__
>>> \
>>>        ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
>>> #endif
>>>
>>> It doesn't work for compilers without GCC __extension__
>>> support.
>>>
>>> This patch uses __builtin_bswap32/64 for GCC>= 4.2.
>>> I used inline function instead of __extension__ to avoid
>>> the __builtin_bswap32/64 return type issue:
>>>
>>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37743
>>>
>>> Tested on Linux/ia32 and Linux/x86-64.  OK to install?
>>>
>>> Thanks.
>>>
>>> H.J.
>>> --
>>> 2012-04-05  H.J. Lu<hongjiu.lu@intel.com>
>>>
>>>         * sysdeps/i386/bits/byteswap.h: (__bswap_32): Use
>>>         __builtin_bswap32 for GCC>= 4.2.
>>>         (__bswap_64): Use __builtin_bswap64 for GCC>= 4.2.
>>>         * sysdeps/x86_64/bits/byteswap.h: Likewise.
>>
>>
>> Please check all other byteswap.h functions as well and do a similar change
>> there as well.
>>
>> Btw. I see a lot of duplication in this code. Perhaps we can reduce the
>> number of files somehow.
>>
>
> That is a good idea.  This patch adds bits/byteswap2.h for __bswap_16 and
> put common 32bit and 64bit bswap in bits/byteswap.h.  I created hjl/bswap
> branch with my change.  OK to install?

I really like what you're doing, thanks for taking this up.

I did a quick review and this looks sane - but I'd like somebody else to 
review this as well since it introduces new headers...

Andreas
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