Use __has_builtin to check clang support

Older versions of Xcode with clang reporting versions 4.[012] and 5.0
did not include support for __builtin_bswap16. Checking in this manner
avoids using brittle version checks.

Matches a change to libvpx:
https://chromium-review.googlesource.com/305573
to fix:
https://code.google.com/p/webm/issues/detail?id=1082

Change-Id: I23ea466ee1b53b12cd3fb45f65a2186c8dda95a1
This commit is contained in:
Johann 2015-10-14 16:33:42 -07:00
parent 12ec204ec7
commit d26d9def80
2 changed files with 10 additions and 15 deletions

View File

@ -38,14 +38,9 @@ extern "C" {
# 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__
#ifndef __has_builtin
# define __has_builtin(x) 0
#endif
#if defined(_MSC_VER) && _MSC_VER > 1310 && \
(defined(_M_X64) || defined(_M_IX86))

View File

@ -35,15 +35,15 @@
#endif
#if !defined(HAVE_CONFIG_H)
// clang-3.3 and gcc-4.3 have builtin functions for swap32/swap64
#if LOCAL_GCC_PREREQ(4,3) || LOCAL_CLANG_PREREQ(3,3)
#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)
#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
#endif
#if LOCAL_GCC_PREREQ(4,3) || __has_builtin(__builtin_bswap64)
#define HAVE_BUILTIN_BSWAP64
#endif
#endif // !HAVE_CONFIG_H
static WEBP_INLINE uint16_t BSwap16(uint16_t x) {