LLVM  13.0.0git
BitmaskEnum.h
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1 //===-- llvm/ADT/BitmaskEnum.h ----------------------------------*- C++ -*-===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_ADT_BITMASKENUM_H
10 #define LLVM_ADT_BITMASKENUM_H
11 
12 #include <cassert>
13 #include <type_traits>
14 #include <utility>
15 
17 
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.
20 ///
21 /// \code
22 /// enum MyEnum {
23 /// E1 = 1, E2 = 2, E3 = 4, E4 = 8,
24 /// LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ E4)
25 /// };
26 ///
27 /// void Foo() {
28 /// MyEnum A = (E1 | E2) & E3 ^ ~E4; // Look, ma: No static_cast!
29 /// }
30 /// \endcode
31 ///
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.
36 ///
37 /// The parameter to LLVM_MARK_AS_BITMASK_ENUM should be the largest individual
38 /// value in your enum.
39 ///
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
43 
44 /// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() pulls the operator overloads used
45 /// by LLVM_MARK_AS_BITMASK_ENUM into the current namespace.
46 ///
47 /// Suppose you have an enum foo::bar::MyEnum. Before using
48 /// LLVM_MARK_AS_BITMASK_ENUM on MyEnum, you must put
49 /// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() somewhere inside namespace foo or
50 /// namespace foo::bar. This allows the relevant operator overloads to be found
51 /// by ADL.
52 ///
53 /// You don't need to use this macro in namespace llvm; it's done at the bottom
54 /// of this file.
55 #define LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() \
56  using ::llvm::BitmaskEnumDetail::operator~; \
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  /* Force a semicolon at the end of this macro. */ \
63  using ::llvm::BitmaskEnumDetail::operator^=
64 
65 namespace llvm {
66 
67 /// Traits class to determine whether an enum has a
68 /// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator.
69 template <typename E, typename Enable = void>
70 struct is_bitmask_enum : std::false_type {};
71 
72 template <typename E>
74  E, std::enable_if_t<sizeof(E::LLVM_BITMASK_LARGEST_ENUMERATOR) >= 0>>
75  : std::true_type {};
76 namespace BitmaskEnumDetail {
77 
78 /// Get a bitmask with 1s in all places up to the high-order bit of E's largest
79 /// value.
80 template <typename E> std::underlying_type_t<E> Mask() {
81  // On overflow, NextPowerOf2 returns zero with the type uint64_t, so
82  // subtracting 1 gives us the mask with all bits set, like we want.
83  return NextPowerOf2(static_cast<std::underlying_type_t<E>>(
84  E::LLVM_BITMASK_LARGEST_ENUMERATOR)) -
85  1;
86 }
87 
88 /// Check that Val is in range for E, and return Val cast to E's underlying
89 /// type.
90 template <typename E> std::underlying_type_t<E> Underlying(E Val) {
91  auto U = static_cast<std::underlying_type_t<E>>(Val);
92  assert(U >= 0 && "Negative enum values are not allowed.");
93  assert(U <= Mask<E>() && "Enum value too large (or largest val too small?)");
94  return U;
95 }
96 
97 constexpr unsigned bitWidth(uint64_t Value) {
98  return Value ? 1 + bitWidth(Value >> 1) : 0;
99 }
100 
101 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
102 E operator~(E Val) {
103  return static_cast<E>(~Underlying(Val) & Mask<E>());
104 }
105 
106 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
107 E operator|(E LHS, E RHS) {
108  return static_cast<E>(Underlying(LHS) | Underlying(RHS));
109 }
110 
111 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
112 E operator&(E LHS, E RHS) {
113  return static_cast<E>(Underlying(LHS) & Underlying(RHS));
114 }
115 
116 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
117 E operator^(E LHS, E RHS) {
118  return static_cast<E>(Underlying(LHS) ^ Underlying(RHS));
119 }
120 
121 // |=, &=, and ^= return a reference to LHS, to match the behavior of the
122 // operators on builtin types.
123 
124 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
125 E &operator|=(E &LHS, E RHS) {
126  LHS = LHS | RHS;
127  return LHS;
128 }
129 
130 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
131 E &operator&=(E &LHS, E RHS) {
132  LHS = LHS & RHS;
133  return LHS;
134 }
135 
136 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
137 E &operator^=(E &LHS, E RHS) {
138  LHS = LHS ^ RHS;
139  return LHS;
140 }
141 
142 } // namespace BitmaskEnumDetail
143 
144 // Enable bitmask enums in namespace ::llvm and all nested namespaces.
146 template <typename E, typename = std::enable_if_t<is_bitmask_enum<E>::value>>
147 constexpr unsigned BitWidth = BitmaskEnumDetail::bitWidth(uint64_t{
148  static_cast<std::underlying_type_t<E>>(
149  E::LLVM_BITMASK_LARGEST_ENUMERATOR)});
150 
151 } // namespace llvm
152 
153 #endif
llvm::NextPowerOf2
uint64_t NextPowerOf2(uint64_t A)
Returns the next power of two (in 64-bits) that is strictly greater than A.
Definition: MathExtras.h:684
MathExtras.h
llvm
Definition: AllocatorList.h:23
llvm::BitmaskEnumDetail::operator&
E operator&(E LHS, E RHS)
Definition: BitmaskEnum.h:112
llvm::BitmaskEnumDetail::Underlying
std::underlying_type_t< E > Underlying(E Val)
Check that Val is in range for E, and return Val cast to E's underlying type.
Definition: BitmaskEnum.h:90
llvm::BitmaskEnumDetail::Mask
std::underlying_type_t< E > Mask()
Get a bitmask with 1s in all places up to the high-order bit of E's largest value.
Definition: BitmaskEnum.h:80
E
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
llvm::BitmaskEnumDetail::operator|=
E & operator|=(E &LHS, E RHS)
Definition: BitmaskEnum.h:125
llvm::BitmaskEnumDetail::operator^=
E & operator^=(E &LHS, E RHS)
Definition: BitmaskEnum.h:137
llvm::BitmaskEnumDetail::operator|
E operator|(E LHS, E RHS)
Definition: BitmaskEnum.h:107
llvm::is_bitmask_enum
Traits class to determine whether an enum has a LLVM_BITMASK_LARGEST_ENUMERATOR enumerator.
Definition: BitmaskEnum.h:70
llvm::LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE
LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE()
llvm::BitmaskEnumDetail::operator&=
E & operator&=(E &LHS, E RHS)
Definition: BitmaskEnum.h:131
assert
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
llvm::BitmaskEnumDetail::operator~
E operator~(E Val)
Definition: BitmaskEnum.h:102
std
Definition: BitVector.h:955
llvm::BitmaskEnumDetail::bitWidth
constexpr unsigned bitWidth(uint64_t Value)
Definition: BitmaskEnum.h:97
llvm::BitmaskEnumDetail::operator^
E operator^(E LHS, E RHS)
Definition: BitmaskEnum.h:117
llvm::BitWidth
constexpr unsigned BitWidth
Definition: BitmaskEnum.h:147
llvm::Value
LLVM Value Representation.
Definition: Value.h:75