shithub: libvpx

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Check for bswap* builtins before using

Canonical builtin checks for clang are to use
__has_builtin. Much less fragile than version checks.

https://code.google.com/p/webm/issues/detail?id=1082

Change-Id: I8151fb75899acdf1a935c23aad9441da99a9abcd

--- a/vpx_util/endian_inl.h

+++ b/vpx_util/endian_inl.h

@@ -25,14 +25,10 @@

 # define LOCAL_GCC_PREREQ(maj, min) 0

 #endif

-#ifdef __clang__

-# define LOCAL_CLANG_VERSION ((__clang_major__ << 8) | __clang_minor__)

-# define LOCAL_CLANG_PREREQ(maj, min) \

-    (LOCAL_CLANG_VERSION >= (((maj) << 8) | (min)))

-#else

-# define LOCAL_CLANG_VERSION 0

-# define LOCAL_CLANG_PREREQ(maj, min) 0

-#endif  // __clang__

+// handle clang compatibility

+#ifndef __has_builtin

+# define __has_builtin(x) 0

+#endif

 // some endian fix (e.g.: mips-gcc doesn't define __BIG_ENDIAN__)

 #if !defined(WORDS_BIGENDIAN) && \

@@ -53,14 +49,16 @@

 #define HToBE32(X) BSwap32(X)

 #endif

-// clang-3.3 and gcc-4.3 have builtin functions for swap32/swap64

-#if LOCAL_GCC_PREREQ(4, 3) || LOCAL_CLANG_PREREQ(3, 3)

+#if LOCAL_GCC_PREREQ(4, 8) || __has_builtin(__builtin_bswap16)

+#define HAVE_BUILTIN_BSWAP16

+#endif

+

+#if LOCAL_GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap32)

 #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_PREREQ(4, 8) || LOCAL_CLANG_PREREQ(3, 3)

-#define HAVE_BUILTIN_BSWAP16

+

+#if LOCAL_GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap64)

+#define HAVE_BUILTIN_BSWAP64

 #endif

 #if HAVE_MIPS32 && defined(__mips__) && !defined(__mips64) && \