Index: boost/atomic/detail/config.hpp
===================================================================
--- boost/atomic/detail/config.hpp	2018-05-09 16:17:05.000000000 -0600
+++ boost/atomic/detail/config.hpp	2018-05-16 16:23:16.000000000 -0600
@@ -36,10 +36,17 @@
 #define BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA
 #endif
 
-#if (defined(__i386__) || defined(__x86_64__)) && (defined(__clang__) || (defined(BOOST_GCC) && (BOOST_GCC+0) < 40500) || defined(__SUNPRO_CC))
 // This macro indicates that the compiler does not support allocating eax:edx or rax:rdx register pairs ("A") in asm blocks
+#if defined(__i386__) || defined(__x86_64__)
+#if defined(__clang__) && defined(__has_feature)
+// Clang introduced this feature after it started supporting rax:rdx register pairs, so can use it to make this determination.
+#if !__has_feature(__attribute_diagnose_if_objc__)
 #define BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS
 #endif
+#elif (defined(BOOST_GCC) && (BOOST_GCC+0) < 40500) || defined(__SUNPRO_CC)
+#define BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS
+#endif
+#endif
 
 #if defined(__i386__) && (defined(__PIC__) || defined(__PIE__)) && !(defined(__clang__) || (defined(BOOST_GCC) && (BOOST_GCC+0) >= 50100))
 // This macro indicates that asm blocks should preserve ebx value unchanged. Some compilers are able to maintain ebx themselves
Index: boost/atomic/detail/ops_gcc_x86_dcas.hpp
==================================================================
--- boost/atomic/detail/ops_gcc_x86_dcas.hpp	2018-05-09 16:17:05.000000000 -0600
+++ boost/atomic/detail/ops_gcc_x86_dcas.hpp	2018-05-16 16:43:51.000000000 -0600
@@ -158,10 +158,11 @@
         }
         else
         {
+#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
 #if defined(__clang__)
-            // Clang cannot allocate eax:edx register pairs but it has sync intrinsics
+            // Older versions of Clang cannot allocate eax:edx register pairs, but they do have sync intrinsics
             value = __sync_val_compare_and_swap(&storage, (storage_type)0, (storage_type)0);
-#elif defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+#else // defined(__clang__)
             uint32_t value_bits[2];
             // We don't care for comparison result here; the previous value will be stored into value anyway.
             // Also we don't care for ebx and ecx values, they just have to be equal to eax and edx before cmpxchg8b.
@@ -175,6 +176,7 @@
                 : BOOST_ATOMIC_DETAIL_ASM_CLOBBER_CC_COMMA "memory"
             );
             BOOST_ATOMIC_DETAIL_MEMCPY(&value, value_bits, sizeof(value));
+#endif // defined(__clang__)
 #else // defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
             // We don't care for comparison result here; the previous value will be stored into value anyway.
             // Also we don't care for ebx and ecx values, they just have to be equal to eax and edx before cmpxchg8b.
@@ -196,9 +198,9 @@
     static BOOST_FORCEINLINE bool compare_exchange_strong(
         storage_type volatile& storage, storage_type& expected, storage_type desired, memory_order, memory_order) BOOST_NOEXCEPT
     {
-#if defined(__clang__)
+#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS) && defined(__clang__)
 
-        // Clang cannot allocate eax:edx register pairs but it has sync intrinsics
+        // Older versions of Clang cannot allocate eax:edx register pairs, but they do have sync intrinsics
         storage_type old_expected = expected;
         expected = __sync_val_compare_and_swap(&storage, old_expected, desired);
         return expected == old_expected;
@@ -401,13 +403,15 @@
 
     static BOOST_FORCEINLINE storage_type load(storage_type const volatile& storage, memory_order) BOOST_NOEXCEPT
     {
+#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+
 #if defined(__clang__)
 
-        // Clang cannot allocate rax:rdx register pairs but it has sync intrinsics
+        // Older versions of Clang cannot allocate rax:rdx register pairs, but they do have sync intrinsics
         storage_type value = storage_type();
         return __sync_val_compare_and_swap(&storage, value, value);
 
-#elif defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+#else // defined(__clang__)
 
         // Some compilers can't allocate rax:rdx register pair either and also don't support 128-bit __sync_val_compare_and_swap
         uint64_t value_bits[2];
@@ -428,6 +432,8 @@
         BOOST_ATOMIC_DETAIL_MEMCPY(&value, value_bits, sizeof(value));
         return value;
 
+#endif // defined(__clang__)
+
 #else // defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
 
         storage_type value;
@@ -452,14 +458,16 @@
     static BOOST_FORCEINLINE bool compare_exchange_strong(
         storage_type volatile& storage, storage_type& expected, storage_type desired, memory_order, memory_order) BOOST_NOEXCEPT
     {
+#if defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+
 #if defined(__clang__)
 
-        // Clang cannot allocate rax:rdx register pairs but it has sync intrinsics
+        // Older versions of Clang cannot allocate rax:rdx register pairs, but they do have sync intrinsics
         storage_type old_expected = expected;
         expected = __sync_val_compare_and_swap(&storage, old_expected, desired);
         return expected == old_expected;
 
-#elif defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
+#else // defined(__clang__)
 
         // Some compilers can't allocate rax:rdx register pair either but also don't support 128-bit __sync_val_compare_and_swap
         bool success;
@@ -474,6 +482,8 @@
 
         return success;
 
+#endif // defined(__clang__)
+
 #else // defined(BOOST_ATOMIC_DETAIL_X86_NO_ASM_AX_DX_PAIRS)
 
         bool success;