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Re: PATCH: Use __builtin_bswap32/64 for GCC >= 4.2


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.

Andreas
--
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