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Add new macro _LIBCPP_BUILTIN_MEMCMP_ISCONSTEXPR to use in std::char_traits. 

This tells whether or not the builtin function __builtin_memcmp is constexpr.
Only defined for clang 4.0 and later, and not true for any shipping version of Apple's clang.

llvm-svn: 291773
This commit is contained in:
Marshall Clow 2017-01-12 16:25:07 +00:00
parent 8a00aeeed1
commit 3d4cc68b8b
1 changed files with 9 additions and 0 deletions
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9
libcxx/include/__config
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@ -396,6 +396,15 @@ namespace std {
#define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK __attribute__((__no_sanitize__("unsigned-integer-overflow")))
#endif
// A constexpr version of __builtin_memcmp was added in clang 4.0
#if __has_builtin(__builtin_memcmp)
# ifdef __apple_build_version__
// No shipping version of Apple's clang has constexpr __builtin_memcmp
# elif __clang_major__ > 3
# define _LIBCPP_BUILTIN_MEMCMP_ISCONSTEXPR
# endif
#endif
#elif defined(_LIBCPP_COMPILER_GCC)
#define _ALIGNAS(x) __attribute__((__aligned__(x)))