[libcxx-commits] [libcxx] [libc++] Simplify features for detecting atomics' support. (PR #75553)

[Konstantin Varlamov via libcxx-commits]

================
@@ -183,25 +183,26 @@ def _getAndroidDeviceApi(cfg):
         actions=[AddLinkFlag("-latomic")],
     ),
     Feature(
-        name="non-lockfree-atomics",
+        name="has-64-bit-atomics",
         when=lambda cfg: sourceBuilds(
             cfg,
             """
             #include <atomic>
-            struct Large { int storage[100]; };
+            struct Large { char storage[64/8]; };
             std::atomic<Large> x;
-            int main(int, char**) { (void)x.load(); return 0; }
+            int main(int, char**) { (void)x.load(); x.is_lockfree(); return 0; }
           """,
         ),
     ),
     Feature(
-        name="has-64-bit-atomics",
+        name="has-128-bit-atomics",
         when=lambda cfg: sourceBuilds(
             cfg,
             """
             #include <atomic>
-            std::atomic_uint64_t x;
-            int main(int, char**) { (void)x.load(); return 0; }
+            struct Large { char storage[128/8]; };
+            std::atomic<Large> x;
+            int main(int, char**) { (void)x.load(); x.is_lockfree(); return 0; }
----------------
var-const wrote:

In It's possible for `x.load()` to succeed and for `x.is_lockfree()` to fail (with a linker error, from what I've seen).

https://github.com/llvm/llvm-project/pull/75553