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

`non-lockfree-atomics` is very similar to `has-64-bit-atomics`; to
simplify, we can have uniform features for atomic types of
increasing sizes (`has-128-bit-atomics`, `has-256-bit-atomics`, etc.).

`is-lockfree-runtime-function` feature was a workaround for the partial
support for large atomic types on older versions of macOS (see
https://reviews.llvm.org/D91911). While we still support macOS 10.14,
conceptually it's simpler to check for support for all the atomic
functionality inside the `has-*-atomics` features, and the workaround is
no longer worth the maintenance cost.

Author: var-const

libcxx/test/libcxx/atomics/atomics.align/align.pass.cpp

@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 //
 // UNSUPPORTED: c++03
-// REQUIRES: is-lockfree-runtime-function
+// REQUIRES: has-128-bit-atomics
 // ADDITIONAL_COMPILE_FLAGS: -Wno-psabi
 // ... since C++20 std::__atomic_base initializes, so we get a warning about an
 // ABI change for vector variants since the constructor code for that is

libcxx/test/libcxx/atomics/atomics.types.generic/atomics.types.float/lockfree.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //   static constexpr bool is_always_lock_free = implementation-defined;
 //   bool is_lock_free() const volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/assign.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  floating-point-type operator=(floating-point-type) volatile noexcept;
 //  floating-point-type operator=(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/compare_exchange_strong.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // bool compare_exchange_strong(T& expected, T desired,
 //                            memory_order success, memory_order failure) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/compare_exchange_weak.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // bool compare_exchange_weak(T& expected, T desired,
 //                            memory_order success, memory_order failure) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/ctor.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // constexpr atomic() noexcept;
 // constexpr atomic(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/exchange.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  T exchange(T, memory_order = memory_order::seq_cst) volatile noexcept;
 //  T exchange(T, memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_add.pass.cpp

@@ -8,7 +8,6 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: target={{x86_64-.*}} && tsan

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_sub.pass.cpp

@@ -8,7 +8,6 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: target={{x86_64-.*}} && tsan

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/load.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  floating-point-type load(memory_order = memory_order::seq_cst) volatile noexcept;
 //  floating-point-type load(memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/lockfree.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //   static constexpr bool is_always_lock_free = implementation-defined;
 //   bool is_lock_free() const volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/notify_all.pass.cpp

@@ -9,7 +9,6 @@
 // XFAIL: availability-synchronization_library-missing
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  void notify_all() volatile noexcept;
 //  void notify_all() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/notify_one.pass.cpp

@@ -9,7 +9,6 @@
 // XFAIL: availability-synchronization_library-missing
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  void notify_one() volatile noexcept;
 //  void notify_one() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.float.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 //  operator floating-point-type() volatile noexcept;
 //  operator floating-point-type() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.minus_equals.pass.cpp

@@ -8,7 +8,6 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // floating-point-type operator-=(floating-point-type) volatile noexcept;
 // floating-point-type operator-=(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.plus_equals.pass.cpp

@@ -8,7 +8,6 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: LIBCXX-AIX-FIXME
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // floating-point-type operator+=(floating-point-type) volatile noexcept;
 // floating-point-type operator+=(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/store.pass.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // void store(floating-point-type, memory_order = memory_order::seq_cst) volatile noexcept;
 // void store(floating-point-type, memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/wait.pass.cpp

@@ -8,7 +8,6 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // XFAIL: availability-synchronization_library-missing
 // XFAIL: !has-64-bit-atomics
-// UNSUPPORTED: !non-lockfree-atomics
 
 // void wait(T old, memory_order order = memory_order::seq_cst) const volatile noexcept;
 // void wait(T old, memory_order order = memory_order::seq_cst) const noexcept;

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_compare_exchange_strong.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_compare_exchange_strong_explicit.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_compare_exchange_weak.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_compare_exchange_weak_explicit.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_exchange.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_exchange_explicit.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_init.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 // ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
 
 // <atomic>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_is_lock_free.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !is-lockfree-runtime-function
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_load.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_load_explicit.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_store.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_store_explicit.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // <atomic>
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.wait/atomic_notify_all.pass.cpp

@@ -8,7 +8,7 @@
 //
 // UNSUPPORTED: no-threads
 // XFAIL: c++03
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // XFAIL: availability-synchronization_library-missing
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.wait/atomic_notify_one.pass.cpp

@@ -8,7 +8,7 @@
 //
 // UNSUPPORTED: no-threads
 // XFAIL: c++03
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // XFAIL: availability-synchronization_library-missing
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.wait/atomic_wait.pass.cpp

@@ -8,7 +8,7 @@
 //
 // UNSUPPORTED: no-threads
 // XFAIL: c++03
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // XFAIL: availability-synchronization_library-missing
 

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.wait/atomic_wait_explicit.pass.cpp

@@ -8,7 +8,7 @@
 //
 // UNSUPPORTED: no-threads
 // XFAIL: c++03
-// XFAIL: !non-lockfree-atomics
+// XFAIL: !has-128-bit-atomics
 
 // XFAIL: availability-synchronization_library-missing
 

libcxx/test/support/atomic_helpers.h

@@ -119,10 +119,7 @@ struct TestEachAtomicType {
     TestFunctor<UserAtomicType>()();
     /*
             Note: These aren't going to be lock-free,
-            so some libatomic.a is necessary. To handle
-            the case where the support functions are
-            missing, all tests that use this file should add:
-            XFAIL: !non-lockfree-atomics
+            so some libatomic.a is necessary.
         */
     TestFunctor<LargeUserAtomicType>()();
     /*

libcxx/utils/libcxx/test/features.py

@@ -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(); (void)x.is_lock_free(); 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(); (void)x.is_lock_free(); return 0; }
           """,
         ),
     ),
@@ -217,20 +218,6 @@ def _getAndroidDeviceApi(cfg):
           """,
         ),
     ),
-    # TODO: Remove this feature once compiler-rt includes __atomic_is_lockfree()
-    # on all supported platforms.
-    Feature(
-        name="is-lockfree-runtime-function",
-        when=lambda cfg: sourceBuilds(
-            cfg,
-            """
-            #include <atomic>
-            struct Large { int storage[100]; };
-            std::atomic<Large> x;
-            int main(int, char**) { return x.is_lock_free(); }
-          """,
-        ),
-    ),
     # Check for a Windows UCRT bug (fixed in UCRT/Windows 10.0.20348.0):
     # https://developercommunity.visualstudio.com/t/utf-8-locales-break-ctype-functions-for-wchar-type/1653678
     Feature(