//===-- llvm/ADT/bit.h - C++20 ----------------------------*- C++ -*-===// // // 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 // //===----------------------------------------------------------------------===// // // This file implements the C++20 header. // //===----------------------------------------------------------------------===// #ifndef LLVM_ADT_BIT_H #define LLVM_ADT_BIT_H #include "llvm/Support/Compiler.h" #include #include namespace llvm { // This implementation of bit_cast is different from the C++17 one in two ways: // - It isn't constexpr because that requires compiler support. // - It requires trivially-constructible To, to avoid UB in the implementation. template ::type #if (__has_feature(is_trivially_constructible) && defined(_LIBCPP_VERSION)) || \ (defined(__GNUC__) && __GNUC__ >= 5) , typename = typename std::is_trivially_constructible::type #elif __has_feature(is_trivially_constructible) , typename = typename std::enable_if<__is_trivially_constructible(To)>::type #else // See comment below. #endif #if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \ (defined(__GNUC__) && __GNUC__ >= 5) , typename = typename std::enable_if::value>::type , typename = typename std::enable_if::value>::type #elif __has_feature(is_trivially_copyable) , typename = typename std::enable_if<__is_trivially_copyable(To)>::type , typename = typename std::enable_if<__is_trivially_copyable(From)>::type #else // This case is GCC 4.x. clang with libc++ or libstdc++ never get here. Unlike // llvm/Support/type_traits.h's is_trivially_copyable we don't want to // provide a good-enough answer here: developers in that configuration will hit // compilation failures on the bots instead of locally. That's acceptable // because it's very few developers, and only until we move past C++11. #endif > inline To bit_cast(const From &from) noexcept { To to; std::memcpy(&to, &from, sizeof(To)); return to; } } // namespace llvm #endif