1343171Sdim//===-- llvm/ADT/bit.h - C++20 <bit> ----------------------------*- C++ -*-===// 2343171Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6343171Sdim// 7343171Sdim//===----------------------------------------------------------------------===// 8343171Sdim// 9343171Sdim// This file implements the C++20 <bit> header. 10343171Sdim// 11343171Sdim//===----------------------------------------------------------------------===// 12343171Sdim 13343171Sdim#ifndef LLVM_ADT_BIT_H 14343171Sdim#define LLVM_ADT_BIT_H 15343171Sdim 16343171Sdim#include "llvm/Support/Compiler.h" 17343171Sdim#include <cstring> 18343171Sdim#include <type_traits> 19343171Sdim 20343171Sdimnamespace llvm { 21343171Sdim 22343171Sdim// This implementation of bit_cast is different from the C++17 one in two ways: 23343171Sdim// - It isn't constexpr because that requires compiler support. 24343171Sdim// - It requires trivially-constructible To, to avoid UB in the implementation. 25343171Sdimtemplate <typename To, typename From 26343171Sdim , typename = typename std::enable_if<sizeof(To) == sizeof(From)>::type 27343171Sdim#if (__has_feature(is_trivially_constructible) && defined(_LIBCPP_VERSION)) || \ 28343171Sdim (defined(__GNUC__) && __GNUC__ >= 5) 29343171Sdim , typename = typename std::is_trivially_constructible<To>::type 30343171Sdim#elif __has_feature(is_trivially_constructible) 31343171Sdim , typename = typename std::enable_if<__is_trivially_constructible(To)>::type 32343171Sdim#else 33343171Sdim // See comment below. 34343171Sdim#endif 35343171Sdim#if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \ 36343171Sdim (defined(__GNUC__) && __GNUC__ >= 5) 37343171Sdim , typename = typename std::enable_if<std::is_trivially_copyable<To>::value>::type 38343171Sdim , typename = typename std::enable_if<std::is_trivially_copyable<From>::value>::type 39343171Sdim#elif __has_feature(is_trivially_copyable) 40343171Sdim , typename = typename std::enable_if<__is_trivially_copyable(To)>::type 41343171Sdim , typename = typename std::enable_if<__is_trivially_copyable(From)>::type 42343171Sdim#else 43353358Sdim// This case is GCC 4.x. clang with libc++ or libstdc++ never get here. Unlike 44353358Sdim// llvm/Support/type_traits.h's is_trivially_copyable we don't want to 45353358Sdim// provide a good-enough answer here: developers in that configuration will hit 46353358Sdim// compilation failures on the bots instead of locally. That's acceptable 47353358Sdim// because it's very few developers, and only until we move past C++11. 48343171Sdim#endif 49343171Sdim> 50343171Sdiminline To bit_cast(const From &from) noexcept { 51343171Sdim To to; 52343171Sdim std::memcpy(&to, &from, sizeof(To)); 53343171Sdim return to; 54343171Sdim} 55343171Sdim 56343171Sdim} // namespace llvm 57343171Sdim 58343171Sdim#endif 59