1 files changed, 34 insertions, 0 deletions
diff --git a/libcxx/include/__bit/bit_floor.h b/libcxx/include/__bit/bit_floor.h
new file mode 100644
index 000000000000..b2e38092f2d7
--- /dev/null
+++ b/libcxx/include/__bit/bit_floor.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_BIT_FLOOR_H
+#define _LIBCPP___BIT_BIT_FLOOR_H
+
+#include <__bit/bit_log2.h>
+#include <__concepts/arithmetic.h>
+#include <__config>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+template <__libcpp_unsigned_integer _Tp>
+_LIBCPP_HIDE_FROM_ABI constexpr _Tp bit_floor(_Tp __t) noexcept {
+  return __t == 0 ? 0 : _Tp{1} << std::__bit_log2(__t);
+}
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___BIT_BIT_FLOOR_H