From 972586b5a1ff0ee1f38884972cefebe111d5495d Mon Sep 17 00:00:00 2001 From: Justin Lebar Date: Wed, 13 Jul 2016 18:23:16 +0000 Subject: [PATCH] [ADT] Add LLVM_MARK_AS_BITMASK_ENUM, used to enable bitwise operations on enums without static_cast. Summary: Normally when you do a bitwise operation on an enum value, you get back an instance of the underlying type (e.g. int). But using this macro, bitwise ops on your enum will return you back instances of the enum. This is particularly useful for enums which represent a combination of flags. Suppose you have a function which takes an int and a set of flags. One way to do this would be to take two numeric params: enum SomeFlags { F1 = 1, F2 = 2, F3 = 4, ... }; void Fn(int Num, int Flags); void foo() { Fn(42, F2 | F3); } But now if you get the order of arguments wrong, you won't get an error. You might try to fix this by changing the signature of Fn so it accepts a SomeFlags arg: enum SomeFlags { F1 = 1, F2 = 2, F3 = 4, ... }; void Fn(int Num, SomeFlags Flags); void foo() { Fn(42, static_cast(F2 | F3)); } But now we need a static cast after doing "F2 | F3" because the result of that computation is the enum's underlying type. This patch adds a mechanism which gives us the safety of the second approach with the brevity of the first. enum SomeFlags { F1 = 1, F2 = 2, F3 = 4, ..., F_MAX = 128, LLVM_MARK_AS_BITMASK_ENUM(F_MAX) }; void Fn(int Num, SomeFlags Flags); void foo() { Fn(42, F2 | F3); // No static_cast. } The LLVM_MARK_AS_BITMASK_ENUM macro enables overloads for bitwise operators on SomeFlags. Critically, these operators return the enum type, not its underlying type, so you don't need any static_casts. An advantage of this solution over the previously-proposed BitMask class [0, 1] is that we don't need any wrapper classes -- we can operate directly on the enum itself. The approach here is somewhat similar to OpenOffice's typed_flags_set [2]. But we skirt the need for a wrapper class (and a good deal of complexity) by judicious use of enable_if. We SFINAE on the presence of a particular enumerator (added by the LLVM_MARK_AS_BITMASK_ENUM macro) instead of using a traits class so that it's impossible to use the enum before the overloads are present. The solution here also seamlessly works across multiple namespaces. [0] http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150622/283369.html [1] http://lists.llvm.org/pipermail/llvm-commits/attachments/20150623/073434b6/attachment.obj [2] https://cgit.freedesktop.org/libreoffice/core/tree/include/o3tl/typed_flags_set.hxx Reviewers: chandlerc, rsmith Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D22279 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275292 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/ADT/BitmaskEnum.h | 152 ++++++++++++++++++++++++++++++ unittests/ADT/BitmaskEnumTest.cpp | 134 ++++++++++++++++++++++++++ unittests/ADT/CMakeLists.txt | 1 + 3 files changed, 287 insertions(+) create mode 100644 include/llvm/ADT/BitmaskEnum.h create mode 100644 unittests/ADT/BitmaskEnumTest.cpp diff --git a/include/llvm/ADT/BitmaskEnum.h b/include/llvm/ADT/BitmaskEnum.h new file mode 100644 index 00000000000..d97354d7af3 --- /dev/null +++ b/include/llvm/ADT/BitmaskEnum.h @@ -0,0 +1,152 @@ +//===-- llvm/ADT/BitmaskEnum.h ----------------------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_ADT_BITMASKENUM_H +#define LLVM_ADT_BITMASKENUM_H + +#include +#include +#include + +#include "llvm/Support/MathExtras.h" + +/// LLVM_MARK_AS_BITMASK_ENUM lets you opt in an individual enum type so you can +/// perform bitwise operations on it without putting static_cast everywhere. +/// +/// \code +/// enum MyEnum { +/// E1 = 1, E2 = 2, E3 = 4, E4 = 8, +/// LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ E4) +/// }; +/// +/// void Foo() { +/// MyEnum A = (E1 | E2) & E3 ^ ~E4; // Look, ma: No static_cast! +/// } +/// \endcode +/// +/// Normally when you do a bitwise operation on an enum value, you get back an +/// instance of the underlying type (e.g. int). But using this macro, bitwise +/// ops on your enum will return you back instances of the enum. This is +/// particularly useful for enums which represent a combination of flags. +/// +/// The parameter to LLVM_MARK_AS_BITMASK_ENUM should be the largest individual +/// value in your enum. +/// +/// All of the enum's values must be non-negative. +#define LLVM_MARK_AS_BITMASK_ENUM(LargestValue) \ + LLVM_BITMASK_LARGEST_ENUMERATOR = LargestValue + +/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() pulls the operator overloads used +/// by LLVM_MARK_AS_BITMASK_ENUM into the current namespace. +/// +/// Suppose you have an enum foo::bar::MyEnum. Before using +/// LLVM_MARK_AS_BITMASK_ENUM on MyEnum, you must put +/// LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() somewhere inside namespace foo or +/// namespace foo::bar. This allows the relevant operator overloads to be found +/// by ADL. +/// +/// You don't need to use this macro in namespace llvm; it's done at the bottom +/// of this file. +#define LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE() \ + using ::llvm::BitmaskEnumDetail::operator~; \ + using ::llvm::BitmaskEnumDetail::operator|; \ + using ::llvm::BitmaskEnumDetail::operator&; \ + using ::llvm::BitmaskEnumDetail::operator^; \ + using ::llvm::BitmaskEnumDetail::operator|=; \ + using ::llvm::BitmaskEnumDetail::operator&=; \ + using ::llvm::BitmaskEnumDetail::operator^=; + +namespace llvm { + +/// Traits class to determine whether an enum has a +/// LLVM_BITMASK_LARGEST_ENUMERATOR enumerator. +template +struct is_bitmask_enum : std::false_type {}; + +template +struct is_bitmask_enum< + E, typename std::enable_if= + 0>::type> : std::true_type {}; +namespace BitmaskEnumDetail { + +/// Get a bitmask with 1s in all places up to the high-order bit of E's largest +/// value. +template typename std::underlying_type::type Mask() { + // On overflow, NextPowerOf2 returns zero with the type uint64_t, so + // subtracting 1 gives us the mask with all bits set, like we want. + return NextPowerOf2(static_cast::type>( + E::LLVM_BITMASK_LARGEST_ENUMERATOR)) - + 1; +} + +/// Check that Val is in range for E, and return Val cast to E's underlying +/// type. +template typename std::underlying_type::type Underlying(E Val) { + auto U = static_cast::type>(Val); + assert(U >= 0 && "Negative enum values are not allowed."); + assert(U <= Mask() && "Enum value too large (or largest val too small?)"); + return U; +} + +template ::value>::type> +E operator~(E Val) { + return static_cast(~Underlying(Val) & Mask()); +} + +template ::value>::type> +E operator|(E LHS, E RHS) { + return static_cast(Underlying(LHS) | Underlying(RHS)); +} + +template ::value>::type> +E operator&(E LHS, E RHS) { + return static_cast(Underlying(LHS) & Underlying(RHS)); +} + +template ::value>::type> +E operator^(E LHS, E RHS) { + return static_cast(Underlying(LHS) ^ Underlying(RHS)); +} + +// |=, &=, and ^= return a reference to LHS, to match the behavior of the +// operators on builtin types. + +template ::value>::type> +E &operator|=(E &LHS, E RHS) { + LHS = LHS | RHS; + return LHS; +} + +template ::value>::type> +E &operator&=(E &LHS, E RHS) { + LHS = LHS & RHS; + return LHS; +} + +template ::value>::type> +E &operator^=(E &LHS, E RHS) { + LHS = LHS ^ RHS; + return LHS; +} + +} // namespace BitmaskEnumDetail + +// Enable bitmask enums in namespace ::llvm and all nested namespaces. +LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE(); + +} // namespace llvm + +#endif diff --git a/unittests/ADT/BitmaskEnumTest.cpp b/unittests/ADT/BitmaskEnumTest.cpp new file mode 100644 index 00000000000..77635c638e9 --- /dev/null +++ b/unittests/ADT/BitmaskEnumTest.cpp @@ -0,0 +1,134 @@ +//===- llvm/unittest/ADT/BitmaskEnumTest.cpp - BitmaskEnum unit tests -----===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "llvm/ADT/BitmaskEnum.h" +#include "gtest/gtest.h" + +using namespace llvm; + +namespace { +enum Flags { + F0 = 0, + F1 = 1, + F2 = 2, + F3 = 4, + F4 = 8, + LLVM_MARK_AS_BITMASK_ENUM(F4) +}; + +TEST(BitmaskEnumTest, BitwiseOr) { + Flags f = F1 | F2; + EXPECT_EQ(3, f); + + f = f | F3; + EXPECT_EQ(7, f); +} + +TEST(BitmaskEnumTest, BitwiseOrEquals) { + Flags f = F1; + f |= F3; + EXPECT_EQ(5, f); + + // |= should return a reference to the LHS. + f = F2; + (f |= F3) = F1; + EXPECT_EQ(F1, f); +} + +TEST(BitmaskEnumTest, BitwiseAnd) { + Flags f = static_cast(3) & F2; + EXPECT_EQ(F2, f); + + f = (f | F3) & (F1 | F2 | F3); + EXPECT_EQ(6, f); +} + +TEST(BitmaskEnumTest, BitwiseAndEquals) { + Flags f = F1 | F2 | F3; + f &= F1 | F2; + EXPECT_EQ(3, f); + + // &= should return a reference to the LHS. + (f &= F1) = F3; + EXPECT_EQ(F3, f); +} + +TEST(BitmaskEnumTest, BitwiseXor) { + Flags f = (F1 | F2) ^ (F2 | F3); + EXPECT_EQ(5, f); + + f = f ^ F1; + EXPECT_EQ(4, f); +} + +TEST(BitmaskEnumTest, BitwiseXorEquals) { + Flags f = (F1 | F2); + f ^= (F2 | F4); + EXPECT_EQ(9, f); + + // ^= should return a reference to the LHS. + (f ^= F4) = F3; + EXPECT_EQ(F3, f); +} + +TEST(BitmaskEnumTest, BitwiseNot) { + Flags f = ~F1; + EXPECT_EQ(14, f); // Largest value for f is 15. + EXPECT_EQ(15, ~F0); +} + +enum class FlagsClass { + F0 = 0, + F1 = 1, + F2 = 2, + F3 = 4, + LLVM_MARK_AS_BITMASK_ENUM(F3) +}; + +TEST(BitmaskEnumTest, ScopedEnum) { + FlagsClass f = (FlagsClass::F1 & ~FlagsClass::F0) | FlagsClass::F2; + f |= FlagsClass::F3; + EXPECT_EQ(7, static_cast(f)); +} + +struct Container { + enum Flags { F0 = 0, F1 = 1, F2 = 2, F3 = 4, LLVM_MARK_AS_BITMASK_ENUM(F3) }; + + static Flags getFlags() { + Flags f = F0 | F1; + f |= F2; + return f; + } +}; + +TEST(BitmaskEnumTest, EnumInStruct) { EXPECT_EQ(3, Container::getFlags()); } + +} // namespace + +namespace foo { +namespace bar { +namespace { +enum FlagsInNamespace { + F0 = 0, + F1 = 1, + F2 = 2, + F3 = 4, + LLVM_MARK_AS_BITMASK_ENUM(F3) +}; +} // namespace +} // namespace foo +} // namespace bar + +namespace { +TEST(BitmaskEnumTest, EnumInNamespace) { + foo::bar::FlagsInNamespace f = ~foo::bar::F0 & (foo::bar::F1 | foo::bar::F2); + f |= foo::bar::F3; + EXPECT_EQ(7, f); +} +} // namespace diff --git a/unittests/ADT/CMakeLists.txt b/unittests/ADT/CMakeLists.txt index 422c18ab2b3..ca1644b5346 100644 --- a/unittests/ADT/CMakeLists.txt +++ b/unittests/ADT/CMakeLists.txt @@ -7,6 +7,7 @@ set(ADTSources APIntTest.cpp APSIntTest.cpp ArrayRefTest.cpp + BitmaskEnumTest.cpp BitVectorTest.cpp DAGDeltaAlgorithmTest.cpp DeltaAlgorithmTest.cpp