Add XIPH_BSWAP32 configure macro to detect __builtin_bswap32() intrinsic.

configure.ac

@@ -66,6 +66,8 @@ AC_SUBST(HAVE_INTTYPES_H)
 AC_CHECK_HEADERS(byteswap.h)
 AC_SUBST(HAVE_BYTESWAP_H)
 
+XIPH_C_BSWAP32
+
 XIPH_C_FIND_ENDIAN
 AC_DEFINE_UNQUOTED(CPU_IS_BIG_ENDIAN, ${ac_cv_c_big_endian},
 					[Target processor is big endian.])

include/share/endswap.h

@@ -31,16 +31,20 @@
 
 /* It is assumed that this header will be included after "config.h". */
 
-#if HAVE_BYTESWAP_H
+#if HAVE_BSWAP32			/* GCC and Clang */
 
-#include <byteswap.h>		/* Linux */
+#define	ENDSWAP_INT(x)		(__builtin_bswap32 (x))
-
-#define	ENDSWAP_INT(x)		((int) bswap_32 (x))
 
 #elif defined _MSC_VER		/* Windows. Apparently in <stdlib.h>. */
 
 #define	ENDSWAP_INT(x)		((int) _byteswap_ulong (x))
 
+#elif HAVE_BYTESWAP_H		/* Linux */
+
+#include <byteswap.h>
+
+#define	ENDSWAP_INT(x)		((int) bswap_32 (x))
+
 #else
 
 #define	ENDSWAP_INT(x)		((((x) >> 24) & 0xFF) + (((x) >> 8) & 0xFF00) + (((x) & 0xFF00) << 8) + (((x) & 0xFF) << 24))

m4/bswap.m4

@@ -0,0 +1,55 @@
+dnl Copyright (C) 2012  Xiph.org Foundation
+dnl
+dnl Redistribution and use in source and binary forms, with or without
+dnl modification, are permitted provided that the following conditions
+dnl are met:
+dnl
+dnl - Redistributions of source code must retain the above copyright
+dnl notice, this list of conditions and the following disclaimer.
+dnl
+dnl - Redistributions in binary form must reproduce the above copyright
+dnl notice, this list of conditions and the following disclaimer in the
+dnl documentation and/or other materials provided with the distribution.
+dnl
+dnl - Neither the name of the Xiph.org Foundation nor the names of its
+dnl contributors may be used to endorse or promote products derived from
+dnl this software without specific prior written permission.
+dnl
+dnl THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+dnl ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+dnl LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+dnl A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
+dnl CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+dnl EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+dnl PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+dnl PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+dnl LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+dnl NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+dnl SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+dnl @synopsis XIPH_C_BSWAP32
+dnl
+dnl @author Erik de Castro Lopo <erikd@mega-nerd.com>
+dnl
+dnl Dtermine whether the compiler has the __builtin_bswap32() intrinsic which
+dnl is likely to be present for most versions of GCC as well as Clang.
+
+AC_DEFUN([XIPH_C_BSWAP32],
+[AC_CACHE_CHECK(has bswap32 instrinsic,
+	ac_cv_c_bswap,
+
+	# Initialize to no
+	ac_cv_c_bswap=no
+	HAVE_BSWAP32=0
+
+	[AC_TRY_LINK([],
+		return __builtin_bswap32 (0) ;,
+			ac_cv_c_bswap=yes
+			HAVE_BSWAP32=1
+			)]
+	AC_DEFINE_UNQUOTED(HAVE_BSWAP32, ${HAVE_BSWAP32},
+					[Compiler has the __builtin_bswap32 intrinsic])
+
+	)]
+)# XIPH_C_BSWAP32