diff --git a/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp b/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
--- a/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
@@ -8,9 +8,6 @@
 //
 // UNSUPPORTED: c++03, c++11, c++14
 
-// Fails for 32-bit builds.
-// UNSUPPORTED: LIBCXX-AIX-FIXME
-
 // <atomic>
 
 // static constexpr bool is_always_lock_free;
@@ -29,38 +26,9 @@
     assert(std::atomic<T>().is_lock_free());
 }
 
-// FIXME: This separate test is needed to work around llvm.org/PR31864
-// which causes ATOMIC_LLONG_LOCK_FREE to be defined as '1' in 32-bit builds
-// even though __atomic_always_lock_free returns true for the same type.
-constexpr bool NeedWorkaroundForPR31864 =
-#if defined(__clang__)
-(sizeof(void*) == 4); // Needed on 32 bit builds
-#else
-false;
-#endif
-
-template <bool Disable = NeedWorkaroundForPR31864,
-  std::enable_if_t<!Disable>* = nullptr,
-  class LLong = long long,
-  class ULLong = unsigned long long>
-void checkLongLongTypes() {
-  static_assert(std::atomic<LLong>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
-  static_assert(std::atomic<ULLong>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
-}
-
-// Used to make the calls to __atomic_always_lock_free dependent on a template
-// parameter.
-template <class T> constexpr size_t getSizeOf() { return sizeof(T); }
-
-template <bool Enable = NeedWorkaroundForPR31864,
-  std::enable_if_t<Enable>* = nullptr,
-  class LLong = long long,
-  class ULLong = unsigned long long>
 void checkLongLongTypes() {
-  constexpr bool ExpectLockFree = __atomic_always_lock_free(getSizeOf<LLong>(), 0);
-  static_assert(std::atomic<LLong>::is_always_lock_free == ExpectLockFree, "");
-  static_assert(std::atomic<ULLong>::is_always_lock_free == ExpectLockFree, "");
-  static_assert((0 != ATOMIC_LLONG_LOCK_FREE) == ExpectLockFree, "");
+  static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
+  static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
 }
 
 void run()