llvm-project/llvm/unittests/ADT/BitmaskEnumTest.cpp

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[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<SomeFlags>(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 llvm-svn: 275292
2016-07-14 02:23:16 +08:00
//===- 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<Flags>(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<int>(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