1 //===-- llvm/ADT/BitmaskEnum.h ----------------------------------*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #ifndef LLVM_ADT_BITMASKENUM_H
10 #define LLVM_ADT_BITMASKENUM_H
13 #include <type_traits>
16 #include "llvm/Support/MathExtras.h"
18 /// LLVM_MARK_AS_BITMASK_ENUM lets you opt in an individual enum type so you can
19 /// perform bitwise operations on it without putting static_cast everywhere.
23 /// E1 = 1, E2 = 2, E3 = 4, E4 = 8,
24 /// LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ E4)
28 /// MyEnum A = (E1 | E2) & E3 ^ ~E4; // Look, ma: No static_cast!
32 /// Normally when you do a bitwise operation on an enum value, you get back an
33 /// instance of the underlying type (e.g. int). But using this macro, bitwise
34 /// ops on your enum will return you back instances of the enum. This is
35 /// particularly useful for enums which represent a combination of flags.
37 /// The parameter to LLVM_MARK_AS_BITMASK_ENUM should be the largest individual
38 /// value in your enum.
40 /// All of the enum's values must be non-negative.
41 #define LLVM_MARK_AS_BITMASK_ENUM(LargestValue) \
42 LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue
44 /// LLVM_DECLARE_ENUM_AS_BITMASK can be used to declare an enum type as a bit
45 /// set, so that bitwise operation on such enum does not require static_cast.
48 /// enum MyEnum { E1 = 1, E2 = 2, E3 = 4, E4 = 8 };
49 /// LLVM_DECLARE_ENUM_AS_BITMASK(MyEnum, E4);
52 /// MyEnum A = (E1 | E2) & E3 ^ ~E4; // No static_cast
56 /// The second parameter to LLVM_DECLARE_ENUM_AS_BITMASK specifies the largest
57 /// bit value of the enum type.
59 /// LLVM_DECLARE_ENUM_AS_BITMASK should be used in llvm namespace.
61 /// This a non-intrusive alternative for LLVM_MARK_AS_BITMASK_ENUM. It allows
62 /// declaring more than one non-scoped enumerations as bitmask types in the same
63 /// scope. Otherwise it provides the same functionality as
64 /// LLVM_MARK_AS_BITMASK_ENUM.
65 #define LLVM_DECLARE_ENUM_AS_BITMASK(Enum, LargestValue) \
66 template <> struct is_bitmask_enum<Enum> : std::true_type {}; \
67 template <> struct largest_bitmask_enum_bit<Enum> { \
68 static constexpr std::underlying_type_t<Enum> value = LargestValue; \
71 /// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() pulls the operator overloads used
72 /// by LLVM_MARK_AS_BITMASK_ENUM into the current namespace.
74 /// Suppose you have an enum foo::bar::MyEnum. Before using
75 /// LLVM_MARK_AS_BITMASK_ENUM on MyEnum, you must put
76 /// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() somewhere inside namespace foo or
77 /// namespace foo::bar. This allows the relevant operator overloads to be found
80 /// You don't need to use this macro in namespace llvm; it's done at the bottom
82 #define LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() \
83 using ::llvm::BitmaskEnumDetail::operator~; \
84 using ::llvm::BitmaskEnumDetail::operator|; \
85 using ::llvm::BitmaskEnumDetail::operator&; \
86 using ::llvm::BitmaskEnumDetail::operator^; \
87 using ::llvm::BitmaskEnumDetail::operator|=; \
88 using ::llvm::BitmaskEnumDetail::operator&=; \
89 /* Force a semicolon at the end of this macro. */ \
90 using ::llvm::BitmaskEnumDetail::operator^=
94 /// Traits class to determine whether an enum has a
95 /// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator.
96 template <typename E, typename Enable = void>
97 struct is_bitmask_enum : std::false_type {};
100 struct is_bitmask_enum<
101 E, std::enable_if_t<sizeof(E::LLVM_BITMASK_LARGEST_ENUMERATOR) >= 0>>
104 /// Trait class to determine bitmask enumeration largest bit.
105 template <typename E, typename Enable = void> struct largest_bitmask_enum_bit;
107 template <typename E>
108 struct largest_bitmask_enum_bit<
109 E, std::enable_if_t<sizeof(E::LLVM_BITMASK_LARGEST_ENUMERATOR) >= 0>> {
110 using UnderlyingTy = std::underlying_type_t<E>;
111 static constexpr UnderlyingTy value =
112 static_cast<UnderlyingTy>(E::LLVM_BITMASK_LARGEST_ENUMERATOR);
115 namespace BitmaskEnumDetail {
117 /// Get a bitmask with 1s in all places up to the high-order bit of E's largest
119 template <typename E> constexpr std::underlying_type_t<E> Mask() {
120 // On overflow, NextPowerOf2 returns zero with the type uint64_t, so
121 // subtracting 1 gives us the mask with all bits set, like we want.
122 return NextPowerOf2(largest_bitmask_enum_bit<E>::value) - 1;
125 /// Check that Val is in range for E, and return Val cast to E's underlying
127 template <typename E> constexpr std::underlying_type_t<E> Underlying(E Val) {
128 auto U = static_cast<std::underlying_type_t<E>>(Val);
129 assert(U >= 0 && "Negative enum values are not allowed.");
130 assert(U <= Mask<E>() && "Enum value too large (or largest val too small?)");
134 constexpr unsigned bitWidth(uint64_t Value) {
135 return Value ? 1 + bitWidth(Value >> 1) : 0;
138 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
139 constexpr E operator~(E Val) {
140 return static_cast<E>(~Underlying(Val) & Mask<E>());
143 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
144 constexpr E operator|(E LHS, E RHS) {
145 return static_cast<E>(Underlying(LHS) | Underlying(RHS));
148 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
149 constexpr E operator&(E LHS, E RHS) {
150 return static_cast<E>(Underlying(LHS) & Underlying(RHS));
153 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
154 constexpr E operator^(E LHS, E RHS) {
155 return static_cast<E>(Underlying(LHS) ^ Underlying(RHS));
158 // |=, &=, and ^= return a reference to LHS, to match the behavior of the
159 // operators on builtin types.
161 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
162 E &operator|=(E &LHS, E RHS) {
167 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
168 E &operator&=(E &LHS, E RHS) {
173 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
174 E &operator^=(E &LHS, E RHS) {
179 } // namespace BitmaskEnumDetail
181 // Enable bitmask enums in namespace ::llvm and all nested namespaces.
182 LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
183 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
184 constexpr unsigned BitWidth = BitmaskEnumDetail::bitWidth(uint64_t{
185 static_cast<std::underlying_type_t<E>>(
186 E::LLVM_BITMASK_LARGEST_ENUMERATOR)});