Merge "configure: check for __builtin_bswapXX()"

configure.ac

@@ -127,6 +127,26 @@ AC_DEFUN([LIBCHECK_EPILOGUE],
           CPPFLAGS=$SAVED_CPPFLAGS
           LIBS=$SAVED_LIBS])
 
+dnl === Check for gcc builtins
+
+dnl === CHECK_FOR_BUILTIN([builtin], [param], [define])
+dnl ===   links a C AC_LANG_PROGRAM, with <builtin>(<param>)
+dnl ===   AC_DEFINE'ing <define> if successful.
+AC_DEFUN([CHECK_FOR_BUILTIN],
+         [AC_LANG_PUSH([C])
+          AC_MSG_CHECKING([for $1])
+          AC_LINK_IFELSE([AC_LANG_PROGRAM([], [$1($2)])],
+                         [AC_MSG_RESULT([yes])
+                          AC_DEFINE([$3], [1],
+                                    [Set to 1 if $1 is available])],
+                         [AC_MSG_RESULT([no])]),
+          AC_LANG_POP])
+
+dnl AC_CHECK_FUNC doesn't work with builtin's.
+CHECK_FOR_BUILTIN([__builtin_bswap16], [1u << 15], [HAVE_BUILTIN_BSWAP16])
+CHECK_FOR_BUILTIN([__builtin_bswap32], [1u << 31], [HAVE_BUILTIN_BSWAP32])
+CHECK_FOR_BUILTIN([__builtin_bswap64], [1ull << 63], [HAVE_BUILTIN_BSWAP64])
+
 dnl === Check for pthread support
 AC_ARG_ENABLE([threading],
               AS_HELP_STRING([--disable-threading],

src/utils/endian_inl.h

@@ -33,24 +33,43 @@
 #define HToLE16(x) (x)
 #endif
 
-// gcc 4.3 has builtin functions for swap32/swap64
+#if !defined(HAVE_CONFIG_H)
-// TODO(jzern): this should have a corresponding autoconf check.
+#ifdef __GNUC__
-#if defined(__GNUC__) && \
+# define LOCAL_GCC_VERSION ((__GNUC__ << 8) | __GNUC_MINOR__)
-           (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
+#else
-#define HAVE_BUILTIN_BSWAP
+# define LOCAL_GCC_VERSION 0
+#endif  // __GNUC__
+
+#ifdef __clang__
+# define LOCAL_CLANG_VERSION ((__clang_major__ << 8) | __clang_minor__)
+#else
+# define LOCAL_CLANG_VERSION 0
+#endif  // __clang__
+
+// clang-3.3 and gcc-4.3 have builtin functions for swap32/swap64
+#if LOCAL_GCC_VERSION >= 0x403 || LOCAL_CLANG_VERSION >= 0x303
+#define HAVE_BUILTIN_BSWAP32
+#define HAVE_BUILTIN_BSWAP64
 #endif
+// clang-3.3 and gcc-4.8 have a builtin function for swap16
+#if LOCAL_GCC_VERSION >= 0x408 || LOCAL_CLANG_VERSION >= 0x303
+#define HAVE_BUILTIN_BSWAP16
+#endif
+#endif  // !HAVE_CONFIG_H
 
 static WEBP_INLINE uint16_t BSwap16(uint16_t x) {
-#if defined(_MSC_VER)
+#if defined(HAVE_BUILTIN_BSWAP16)
+  return __builtin_bswap16(x);
+#elif defined(_MSC_VER)
   return _byteswap_ushort(x);
 #else
   // gcc will recognize a 'rorw $8, ...' here:
   return (x >> 8) | ((x & 0xff) << 8);
-#endif  // _MSC_VER
+#endif  // HAVE_BUILTIN_BSWAP16
 }
 
 static WEBP_INLINE uint32_t BSwap32(uint32_t x) {
-#if defined(HAVE_BUILTIN_BSWAP)
+#if defined(HAVE_BUILTIN_BSWAP32)
   return __builtin_bswap32(x);
 #elif defined(__i386__) || defined(__x86_64__)
   uint32_t swapped_bytes;
@@ -60,11 +79,11 @@ static WEBP_INLINE uint32_t BSwap32(uint32_t x) {
   return (uint32_t)_byteswap_ulong(x);
 #else
   return (x >> 24) | ((x >> 8) & 0xff00) | ((x << 8) & 0xff0000) | (x << 24);
-#endif  // HAVE_BUILTIN_BSWAP
+#endif  // HAVE_BUILTIN_BSWAP32
 }
 
 static WEBP_INLINE uint64_t BSwap64(uint64_t x) {
-#if defined(HAVE_BUILTIN_BSWAP)
+#if defined(HAVE_BUILTIN_BSWAP64)
   return __builtin_bswap64(x);
 #elif defined(__x86_64__)
   uint64_t swapped_bytes;
@@ -77,7 +96,7 @@ static WEBP_INLINE uint64_t BSwap64(uint64_t x) {
   x = ((x & 0xffff0000ffff0000ull) >> 16) | ((x & 0x0000ffff0000ffffull) << 16);
   x = ((x & 0xff00ff00ff00ff00ull) >>  8) | ((x & 0x00ff00ff00ff00ffull) <<  8);
   return x;
-#endif  // HAVE_BUILTIN_BSWAP
+#endif  // HAVE_BUILTIN_BSWAP64
 }
 
 #endif  // WEBP_UTILS_ENDIAN_INL_H_