fix conversation

Author: poor-circle

libcxx/docs/ReleaseNotes/22.rst

@@ -83,7 +83,7 @@ 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.
+- The performance of ``align`` has been improved about 2x by making it an inline function.
 
 Deprecations and Removals
 -------------------------

libcxx/include/__configuration/abi.h

@@ -97,18 +97,19 @@
 // so disable it.
 #    define _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
 #  endif
-// The PE/COFF format reports a linking error when encountering multiple symbol definitions where at least one is a
-// strong symbol. So we can't inlining a function without ABI breakchange.
-#  if defined(_LIBCPP_OBJECT_FORMAT_COFF)
-#    define _LIBCPP_DISABLE_INLINE_OPTIMIZE_BECAUSE_MULTIPLY_SYMBOLS_ERROR
-#  endif
 // Feature macros for disabling pre ABI v1 features. All of these options
 // are deprecated.
 #  if defined(__FreeBSD__)
 #    define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
 #  endif
 #endif
 
+// The PE/COFF format reports a linking error when encountering multiple symbol definitions where at least one is a
+// strong symbol. So we can't inlining a non-inline function without ABI break change.
+#if defined(_LIBCPP_OBJECT_FORMAT_COFF)
+#  define _LIBCPP_DISABLE_INLINE_OPTIMIZE_BECAUSE_MULTIPLY_SYMBOLS_ERROR
+#endif
+
 // TODO(LLVM 22): Remove this check
 #if defined(_LIBCPP_ABI_NO_ITERATOR_BASES) && !defined(_LIBCPP_ABI_NO_REVERSE_ITERATOR_SECOND_MEMBER)
 #  ifndef _LIBCPP_ONLY_NO_ITERATOR_BASES

libcxx/include/__memory/align.h

@@ -19,8 +19,13 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_ALWAYS_INLINE inline void*
-__align_impl(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
+#if defined(_LIBCPP_DISABLE_INLINE_OPTIMIZE_BECAUSE_MULTIPLY_SYMBOLS_ERROR) && !defined(_LIBCPP_ABI_DO_NOT_EXPORT_ALIGN)
+
+_LIBCPP_EXPORTED_FROM_ABI void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);
+
+#else
+
+_LIBCPP_HIDE_FROM_ABI inline void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
   void* __r = nullptr;
   if (__sz <= __space) {
     char* __p1 = static_cast<char*>(__ptr);
@@ -35,20 +40,7 @@ __align_impl(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
   return __r;
 }
 
-#ifndef _LIBCPP_EXPORT_ALIGN_SYMBOL
-#  ifdef _LIBCPP_DISABLE_INLINE_OPTIMIZE_BECAUSE_MULTIPLY_SYMBOLS_ERROR
-
-_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) {
-  return __align_impl(__align, __sz, __ptr, __space);
-}
-
-#  endif //  _LIBCPP_DISABLE_INLINE_OPTIMIZE_BECAUSE_MULTIPLY_SYMBOLS_ERROR
-
-#endif // _LIBCPP_EXPORT_ALIGN_SYMBOL
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 

libcxx/src/CMakeLists.txt

@@ -31,6 +31,7 @@ set(LIBCXX_SOURCES
   include/to_chars_floating_point.h
   include/from_chars_floating_point.h
   memory.cpp
+  memory_align.cpp
   memory_resource.cpp
   new_handler.cpp
   new_helpers.cpp

libcxx/src/memory.cpp

@@ -10,9 +10,6 @@
 #ifdef _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
 #  define _LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS
 #endif
-#ifndef _LIBCPP_ABI_DO_NOT_EXPORT_ALIGN
-#  define _LIBCPP_EXPORT_ALIGN_SYMBOL
-#endif
 
 #include <__functional/hash.h>
 #include <memory>
@@ -135,12 +132,4 @@ __sp_mut& __get_sp_mut(const void* p) {
 
 #endif // _LIBCPP_HAS_THREADS
 
-#if defined(_LIBCPP_EXPORT_ALIGN_SYMBOL)
-
-_LIBCPP_EXPORTED_FROM_ABI void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
-  return __align_impl(alignment, size, ptr, space);
-}
-
-#endif // _LIBCPP_EXPORT_ALIGN_SYMBOL
-
 _LIBCPP_END_NAMESPACE_STD

libcxx/src/memory_align.cpp

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <__cstddef/size_t.h>
+#include <cstdint>
+
+// Don't include <memory> to avoid mulitple declartion of align()
+
+#if !defined(_LIBCPP_ABI_DO_NOT_EXPORT_ALIGN)
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_EXPORTED_FROM_ABI void* align(size_t alignment, size_t size, void*& ptr, size_t& space) {
+  void* r = nullptr;
+  if (size <= space) {
+    char* p1 = static_cast<char*>(ptr);
+    char* p2 = reinterpret_cast<char*>(reinterpret_cast<uintptr_t>(p1 + (alignment - 1)) & -alignment);
+    size_t d = static_cast<size_t>(p2 - p1);
+    if (d <= space - size) {
+      r   = p2;
+      ptr = r;
+      space -= d;
+    }
+  }
+  return r;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_ABI_DO_NOT_EXPORT_ALIGN

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

@@ -9,17 +9,29 @@
 // UNSUPPORTED: c++03
 
 #include <memory>
+#include <iostream>
 
 #include "benchmark/benchmark.h"
-#include "test_macros.h"
+
+struct Input {
+  std::size_t align;
+  std::size_t size;
+  void* ptr;
+  std::size_t buffer_size;
+};
 
 static void BM_align(benchmark::State& state) {
   char buffer[1024];
-  void* data = buffer + 123;
-  std::size_t sz{sizeof(buffer) - 123};
-
+  Input input{};
+  void* ptr               = buffer + 123;
+  std::size_t buffer_size = sizeof(buffer) - 123;
+  input.align             = state.range();
+  input.size              = state.range();
   for (auto _ : state) {
-    benchmark::DoNotOptimize(std::align(state.range(), state.range(), data, sz));
+    input.ptr         = ptr;
+    input.buffer_size = buffer_size;
+    benchmark::DoNotOptimize(input);
+    benchmark::DoNotOptimize(std::align(input.align, input.size, input.ptr, input.buffer_size));
   }
 }
 BENCHMARK(BM_align)->Range(1, 256);

llvm/utils/gn/secondary/libcxx/src/BUILD.gn

@@ -152,6 +152,7 @@ cxx_sources = [
   "iostream.cpp",
   "locale.cpp",
   "memory.cpp",
+  "memory_align.cpp"
   "memory_resource.cpp",
   "mutex.cpp",
   "mutex_destructor.cpp",