also make align an inline function in v1 abi

Author: poor-circle

libcxx/docs/ReleaseNotes/22.rst

@@ -82,6 +82,8 @@ Improvements and New Features
   iterators, resulting in a performance improvement for ``std::deque<short>`` and
   ``std::join_view<vector<vector<short>>>`` iterators.
 
+- The performance of ``align`` has been improved about 3x by making it an inline function.
+
 Deprecations and Removals
 -------------------------
 
@@ -98,6 +100,8 @@ Potentially breaking changes
   ``_LIBCPP_ABI_NO_ITERATOR_BASES``. If you are using this flag and care about ABI stability, you should set
   ``_LIBCPP_ABI_NO_REVERSE_ITERATOR_SECOND_MEMBER`` as well.
 
+- ``align`` has been removed from libc++ dynamic library in ABI v2. You could use the ABI flag ``_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS`` to reserve it.
+
 Announcements About Future Releases
 -----------------------------------
 
@@ -113,5 +117,7 @@ ABI Affecting Changes
   potentially inheriting from the types they wrap. At this point in time we are not aware of any ABI changes caused by
   this.
 
+- ``align`` has been removed from libc++ dynamic library in ABI v2. You could use the ABI flag ``_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS`` to reserve it.
+
 Build System Changes
 --------------------

libcxx/include/__memory/align.h

@@ -19,8 +19,12 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-// From >=v2 ABI, std::align is an inline function.
-#if _LIBCPP_ABI_VERSION >= 2
+#ifdef _LIBCPP_ALIGN_DEFINE_LEGACY_INLINE_FUNCTIONS
+
+_LIBCPP_EXPORTED_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);
+
+#else
+
 inline _LIBCPP_HIDE_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
   void* __r = nullptr;
   if (__sz <= __space) {
@@ -35,9 +39,8 @@ inline _LIBCPP_HIDE_FROM_ABI void* align(size_t __align, size_t __sz, void*& __p
   }
   return __r;
 }
-#else
-_LIBCPP_EXPORTED_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);
-#endif
+
+#endif // _LIBCPP_ALIGN_DEFINE_LEGACY_INLINE_FUNCTIONS
 
 _LIBCPP_END_NAMESPACE_STD
 

libcxx/src/memory.cpp

@@ -8,6 +8,7 @@
 
 #include <__config>
 #ifdef _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
+#  define _LIBCPP_ALIGN_DEFINE_LEGACY_INLINE_FUNCTIONS
 #  define _LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS
 #endif
 
@@ -132,8 +133,8 @@ __sp_mut& __get_sp_mut(const void* p) {
 
 #endif // _LIBCPP_HAS_THREADS
 
-// Remove std::align from >=v2 dylib ABI, make it an inline function.
-#if _LIBCPP_ABI_VERSION == 1
+#if defined(_LIBCPP_ALIGN_DEFINE_LEGACY_INLINE_FUNCTIONS)
+
 void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
   void* r = nullptr;
   if (size <= space) {
@@ -148,6 +149,6 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
   }
   return r;
 }
-#endif
+#endif // _LIBCPP_ALIGN_DEFINE_LEGACY_INLINE_FUNCTIONS
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/test/benchmarks/memory/align.bench.cpp

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+#include <memory>
+
+#include "benchmark/benchmark.h"
+#include "test_macros.h"
+
+static void BM_align(benchmark::State& state) {
+  char buffer[1024];
+  char* data = buffer + 123;
+  std::size_t sz{1024 - 123};
+  void* p;
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(std::align(state.range(), state.range(), p, sz))
+  }
+}
+BENCHMARK(BM_align)->Range(1, 256);
+
+BENCHMARK_MAIN();