1//===-- llvm/ADT/BitmaskEnum.h ----------------------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#ifndef LLVM_ADT_BITMASKENUM_H 11#define LLVM_ADT_BITMASKENUM_H 12 13#include <cassert> 14#include <type_traits> 15#include <utility> 16 17#include "llvm/Support/MathExtras.h" 18 19/// LLVM_MARK_AS_BITMASK_ENUM lets you opt in an individual enum type so you can 20/// perform bitwise operations on it without putting static_cast everywhere. 21/// 22/// \code 23/// enum MyEnum { 24/// E1 = 1, E2 = 2, E3 = 4, E4 = 8, 25/// LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ E4) 26/// }; 27/// 28/// void Foo() { 29/// MyEnum A = (E1 | E2) & E3 ^ ~E4; // Look, ma: No static_cast! 30/// } 31/// \endcode 32/// 33/// Normally when you do a bitwise operation on an enum value, you get back an 34/// instance of the underlying type (e.g. int). But using this macro, bitwise 35/// ops on your enum will return you back instances of the enum. This is 36/// particularly useful for enums which represent a combination of flags. 37/// 38/// The parameter to LLVM_MARK_AS_BITMASK_ENUM should be the largest individual 39/// value in your enum. 40/// 41/// All of the enum's values must be non-negative. 42#define LLVM_MARK_AS_BITMASK_ENUM(LargestValue) \ 43 LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue 44 45/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() pulls the operator overloads used 46/// by LLVM_MARK_AS_BITMASK_ENUM into the current namespace. 47/// 48/// Suppose you have an enum foo::bar::MyEnum. Before using 49/// LLVM_MARK_AS_BITMASK_ENUM on MyEnum, you must put 50/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() somewhere inside namespace foo or 51/// namespace foo::bar. This allows the relevant operator overloads to be found 52/// by ADL. 53/// 54/// You don't need to use this macro in namespace llvm; it's done at the bottom 55/// of this file. 56#define LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() \ 57 using ::llvm::BitmaskEnumDetail::operator~; \ 58 using ::llvm::BitmaskEnumDetail::operator|; \ 59 using ::llvm::BitmaskEnumDetail::operator&; \ 60 using ::llvm::BitmaskEnumDetail::operator^; \ 61 using ::llvm::BitmaskEnumDetail::operator|=; \ 62 using ::llvm::BitmaskEnumDetail::operator&=; \ 63 /* Force a semicolon at the end of this macro. */ \ 64 using ::llvm::BitmaskEnumDetail::operator^= 65 66namespace llvm { 67 68/// Traits class to determine whether an enum has a 69/// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator. 70template <typename E, typename Enable = void> 71struct is_bitmask_enum : std::false_type {}; 72 73template <typename E> 74struct is_bitmask_enum< 75 E, typename std::enable_if<sizeof(E::LLVM_BITMASK_LARGEST_ENUMERATOR) >= 76 0>::type> : std::true_type {}; 77namespace BitmaskEnumDetail { 78 79/// Get a bitmask with 1s in all places up to the high-order bit of E's largest 80/// value. 81template <typename E> typename std::underlying_type<E>::type Mask() { 82 // On overflow, NextPowerOf2 returns zero with the type uint64_t, so 83 // subtracting 1 gives us the mask with all bits set, like we want. 84 return NextPowerOf2(static_cast<typename std::underlying_type<E>::type>( 85 E::LLVM_BITMASK_LARGEST_ENUMERATOR)) - 86 1; 87} 88 89/// Check that Val is in range for E, and return Val cast to E's underlying 90/// type. 91template <typename E> typename std::underlying_type<E>::type Underlying(E Val) { 92 auto U = static_cast<typename std::underlying_type<E>::type>(Val); 93 assert(U >= 0 && "Negative enum values are not allowed."); 94 assert(U <= Mask<E>() && "Enum value too large (or largest val too small?)"); 95 return U; 96} 97 98template <typename E, 99 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 100E operator~(E Val) { 101 return static_cast<E>(~Underlying(Val) & Mask<E>()); 102} 103 104template <typename E, 105 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 106E operator|(E LHS, E RHS) { 107 return static_cast<E>(Underlying(LHS) | Underlying(RHS)); 108} 109 110template <typename E, 111 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 112E operator&(E LHS, E RHS) { 113 return static_cast<E>(Underlying(LHS) & Underlying(RHS)); 114} 115 116template <typename E, 117 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 118E operator^(E LHS, E RHS) { 119 return static_cast<E>(Underlying(LHS) ^ Underlying(RHS)); 120} 121 122// |=, &=, and ^= return a reference to LHS, to match the behavior of the 123// operators on builtin types. 124 125template <typename E, 126 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 127E &operator|=(E &LHS, E RHS) { 128 LHS = LHS | RHS; 129 return LHS; 130} 131 132template <typename E, 133 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 134E &operator&=(E &LHS, E RHS) { 135 LHS = LHS & RHS; 136 return LHS; 137} 138 139template <typename E, 140 typename = typename std::enable_if<is_bitmask_enum<E>::value>::type> 141E &operator^=(E &LHS, E RHS) { 142 LHS = LHS ^ RHS; 143 return LHS; 144} 145 146} // namespace BitmaskEnumDetail 147 148// Enable bitmask enums in namespace ::llvm and all nested namespaces. 149LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE(); 150 151} // namespace llvm 152 153#endif 154