[libcxx-commits] [libcxx] [libc++] Implement `<bit>` parts of P3793R2 Better shifting (PR #219389)

[Jan Schultke via libcxx-commits]

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@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___BIT_SHIFT_H
+#define _LIBCPP___BIT_SHIFT_H
+
+#include <__config>
+#include <__type_traits/integer_traits.h>
+#include <__type_traits/make_unsigned.h>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// Writing two full functions for shl and shr makes it easier for the compiler
+// to optimize the code.
+
+#if _LIBCPP_STD_VER >= 29
+
+template <__signed_or_unsigned_integer _Tp, __signed_or_unsigned_integer _Shift>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp shl(_Tp __t, _Shift __cnt) noexcept {
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eisenwave wrote:

I assume you mean `bit/nodiscard.verify.cpp`. Done.

https://github.com/llvm/llvm-project/pull/219389