1c06165c9b
`std::align` is heavily used in memory allocators. When we attempted to switch from libstdc++ to libc++, we observed a **50%** performance regression in a database query bench: the issue is that `std::align` in libc++ is not an inline function, which prevents the compiler from performing inlining optimizations. make `std::align` an inline function will run about 2x faster. See [benchmark result](https://quick-bench.com/q/wPTnt9JCGn2S-3bu5gY9YrEf6KU). --------- Co-authored-by: Louis Dionne <ldionne.2@gmail.com>
43 lines
1.2 KiB
C++
43 lines
1.2 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___MEMORY_ALIGN_H
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#define _LIBCPP___MEMORY_ALIGN_H
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#include <__config>
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#include <__cstddef/size_t.h>
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#include <cstdint>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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inline namespace __align_inline {
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_LIBCPP_HIDE_FROM_ABI inline void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space) {
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void* __r = nullptr;
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if (__sz <= __space) {
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char* __p1 = static_cast<char*>(__ptr);
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char* __p2 = reinterpret_cast<char*>(reinterpret_cast<uintptr_t>(__p1 + (__align - 1)) & -__align);
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size_t __d = static_cast<size_t>(__p2 - __p1);
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if (__d <= __space - __sz) {
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__r = __p2;
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__ptr = __r;
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__space -= __d;
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}
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}
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return __r;
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}
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} // namespace __align_inline
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___MEMORY_ALIGN_H
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