LCOV - code coverage report
Current view: top level - include/llvm/ADT - BitmaskEnum.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 9 9 100.0 %
Date: 2017-09-14 15:23:50 Functions: 0 0 -
Legend: Lines: hit not hit

          Line data    Source code
       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             : 
      66             : namespace llvm {
      67             : 
      68             : /// Traits class to determine whether an enum has a
      69             : /// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator.
      70             : template <typename E, typename Enable = void>
      71             : struct is_bitmask_enum : std::false_type {};
      72             : 
      73             : template <typename E>
      74             : struct is_bitmask_enum<
      75             :     E, typename std::enable_if<sizeof(E::LLVM_BITMASK_LARGEST_ENUMERATOR) >=
      76             :                                0>::type> : std::true_type {};
      77             : namespace BitmaskEnumDetail {
      78             : 
      79             : /// Get a bitmask with 1s in all places up to the high-order bit of E's largest
      80             : /// value.
      81             : template <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        8740 :   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.
      91             : template <typename E> typename std::underlying_type<E>::type Underlying(E Val) {
      92    86094754 :   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             : 
      98             : template <typename E,
      99             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     100             : E operator~(E Val) {
     101       15301 :   return static_cast<E>(~Underlying(Val) & Mask<E>());
     102             : }
     103             : 
     104             : template <typename E,
     105             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     106             : E operator|(E LHS, E RHS) {
     107     4727008 :   return static_cast<E>(Underlying(LHS) | Underlying(RHS));
     108             : }
     109             : 
     110             : template <typename E,
     111             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     112             : E operator&(E LHS, E RHS) {
     113    81358998 :   return static_cast<E>(Underlying(LHS) & Underlying(RHS));
     114             : }
     115             : 
     116             : template <typename E,
     117             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     118             : E operator^(E LHS, E RHS) {
     119           8 :   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             : 
     125             : template <typename E,
     126             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     127             : E &operator|=(E &LHS, E RHS) {
     128     2321373 :   LHS = LHS | RHS;
     129             :   return LHS;
     130             : }
     131             : 
     132             : template <typename E,
     133             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     134             : E &operator&=(E &LHS, E RHS) {
     135       13256 :   LHS = LHS & RHS;
     136             :   return LHS;
     137             : }
     138             : 
     139             : template <typename E,
     140             :           typename = typename std::enable_if<is_bitmask_enum<E>::value>::type>
     141             : E &operator^=(E &LHS, E RHS) {
     142           4 :   LHS = LHS ^ RHS;
     143             :   return LHS;
     144             : }
     145             : 
     146             : } // namespace BitmaskEnumDetail
     147             : 
     148             : // Enable bitmask enums in namespace ::llvm and all nested namespaces.
     149             : LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
     150             : 
     151             : } // namespace llvm
     152             : 
     153             : #endif

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