Use __builtin_bit_cast when available

include/boost/core/bit.hpp

@@ -43,6 +43,16 @@
 # define BOOST_CORE_HAS_BUILTIN_ISCONSTEVAL
 #endif
 
+#if defined(__has_builtin)
+# if __has_builtin(__builtin_bit_cast)
+#  define BOOST_CORE_HAS_BUILTIN_BIT_CAST
+# endif
+#endif
+
+#if defined(BOOST_MSVC) && BOOST_MSVC >= 1926
+#  define BOOST_CORE_HAS_BUILTIN_BIT_CAST
+#endif
+
 namespace boost
 {
 namespace core
@@ -50,6 +60,16 @@ namespace core
 
 // bit_cast
 
+#if defined(BOOST_CORE_HAS_BUILTIN_BIT_CAST)
+
+template<class To, class From>
+BOOST_CONSTEXPR To bit_cast( From const & from ) BOOST_NOEXCEPT
+{
+    return __builtin_bit_cast( To, from );
+}
+
+#else
+
 template<class To, class From>
 To bit_cast( From const & from ) BOOST_NOEXCEPT
 {
@@ -60,6 +80,8 @@ To bit_cast( From const & from ) BOOST_NOEXCEPT
     return to;
 }
 
+#endif
+
 // countl
 
 #if defined(__GNUC__) || defined(__clang__)