[llvm] a6d3987 - [ADT] Add new type traits for type pack indexes
Scott Linder via llvm-commits
llvm-commits at lists.llvm.org
Mon May 17 15:29:14 PDT 2021
Author: Scott Linder
Date: 2021-05-17T22:28:55Z
New Revision: a6d3987b8ef3b7616f0835b89515c4264f2a7a64
URL: https://github.com/llvm/llvm-project/commit/a6d3987b8ef3b7616f0835b89515c4264f2a7a64
DIFF: https://github.com/llvm/llvm-project/commit/a6d3987b8ef3b7616f0835b89515c4264f2a7a64.diff
LOG: [ADT] Add new type traits for type pack indexes
Similar versions of these already exist, this effectively just just
factors them out into STLExtras. I plan to use these in future patches.
Differential Revision: https://reviews.llvm.org/D100672
Added:
Modified:
llvm/include/llvm/ADT/PointerUnion.h
llvm/include/llvm/ADT/STLExtras.h
llvm/unittests/ADT/STLExtrasTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/ADT/PointerUnion.h b/llvm/include/llvm/ADT/PointerUnion.h
index c39691061b72..5c3ef01f1b05 100644
--- a/llvm/include/llvm/ADT/PointerUnion.h
+++ b/llvm/include/llvm/ADT/PointerUnion.h
@@ -64,21 +64,6 @@ namespace pointer_union_detail {
return std::min<int>({PointerLikeTypeTraits<Ts>::NumLowBitsAvailable...});
}
- /// Find the index of a type in a list of types. TypeIndex<T, Us...>::Index
- /// is the index of T in Us, or sizeof...(Us) if T does not appear in the
- /// list.
- template <typename T, typename ...Us> struct TypeIndex;
- template <typename T, typename ...Us> struct TypeIndex<T, T, Us...> {
- static constexpr int Index = 0;
- };
- template <typename T, typename U, typename... Us>
- struct TypeIndex<T, U, Us...> {
- static constexpr int Index = 1 + TypeIndex<T, Us...>::Index;
- };
- template <typename T> struct TypeIndex<T> {
- static constexpr int Index = 0;
- };
-
/// Find the first type in a list of types.
template <typename T, typename...> struct GetFirstType {
using type = T;
@@ -145,6 +130,7 @@ namespace pointer_union_detail {
/// P = (float*)0;
/// Y = P.get<float*>(); // ok.
/// X = P.get<int*>(); // runtime assertion failure.
+/// PointerUnion<int*, int*> Q; // compile time failure.
template <typename... PTs>
class PointerUnion
: public pointer_union_detail::PointerUnionMembers<
@@ -153,12 +139,14 @@ class PointerUnion
void *, pointer_union_detail::bitsRequired(sizeof...(PTs)), int,
pointer_union_detail::PointerUnionUIntTraits<PTs...>>,
0, PTs...> {
+ static_assert(TypesAreDistinct<PTs...>(),
+ "PointerUnion alternative types cannot be repeated");
// The first type is special because we want to directly cast a pointer to a
// default-initialized union to a pointer to the first type. But we don't
// want PointerUnion to be a 'template <typename First, typename ...Rest>'
// because it's much more convenient to have a name for the whole pack. So
// split off the first type here.
- using First = typename pointer_union_detail::GetFirstType<PTs...>::type;
+ using First = TypeAtIndex<0, PTs...>;
using Base = typename PointerUnion::PointerUnionMembers;
public:
@@ -175,10 +163,7 @@ class PointerUnion
/// Test if the Union currently holds the type matching T.
template <typename T> bool is() const {
- constexpr int Index = pointer_union_detail::TypeIndex<T, PTs...>::Index;
- static_assert(Index < sizeof...(PTs),
- "PointerUnion::is<T> given type not in the union");
- return this->Val.getInt() == Index;
+ return this->Val.getInt() == FirstIndexOfType<T, PTs...>{};
}
/// Returns the value of the specified pointer type.
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index 182451c25e32..fad62a5f7c9b 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -144,6 +144,60 @@ template <typename ReturnType, typename... Args>
struct function_traits<ReturnType (&)(Args...), false>
: public function_traits<ReturnType (*)(Args...)> {};
+namespace detail {
+template <typename T, typename... Ts>
+constexpr size_t getFirstIndexOfTypeImpl() {
+ constexpr bool Matches[] = {false, std::is_same<T, Ts>{}...};
+ // TODO: use llvm::find once it's constexpr (std::find is constexpr in C++20)
+ for (size_t I = 1; I <= sizeof...(Ts); ++I)
+ if (Matches[I])
+ return I - 1;
+ return sizeof...(Ts);
+}
+template <typename T, typename... Ts> constexpr size_t getFirstIndexOfType() {
+ constexpr size_t Index = getFirstIndexOfTypeImpl<T, Ts...>();
+ static_assert(Index != sizeof...(Ts),
+ "type T is not present in type pack Ts");
+ return Index;
+}
+template <typename... Ts> static constexpr bool areTypesDistinct() {
+ constexpr size_t IndexOf[] = {0, getFirstIndexOfType<Ts, Ts...>()...};
+ // TODO: use llvm::find once it's constexpr (std::find is constexpr in C++20)
+ for (size_t I = 1; I <= sizeof...(Ts); ++I)
+ if (I - 1 != IndexOf[I])
+ return false;
+ return true;
+}
+} // namespace detail
+
+/// Determine if all types in Ts are distinct.
+///
+/// Useful to statically assert when Ts is intended to describe a non-multi set
+/// of types.
+template <typename... Ts>
+using TypesAreDistinct =
+ std::integral_constant<bool, detail::areTypesDistinct<Ts...>()>;
+
+/// Find the first index where a type appears in a list of types.
+///
+/// FirstIndexOfType<T, Ts...>::value is the first index of T in Ts.
+///
+/// Typically only meaningful when it is otherwise statically known that the
+/// type pack has no duplicate types. This should be guaranteed explicitly with
+/// static_assert(TypesAreDistinct<Ts...>{}).
+///
+/// It is a compile-time error to instantiate when T is not present in Ts, i.e.
+/// if is_one_of<T, Ts...>::value is false.
+template <typename T, typename... Ts>
+using FirstIndexOfType =
+ std::integral_constant<size_t, detail::getFirstIndexOfType<T, Ts...>()>;
+
+/// Find the type at a given index in a list of types.
+///
+/// TypeAtIndex<I, Ts...> is the type at index I in Ts.
+template <size_t I, typename... Ts>
+using TypeAtIndex = std::tuple_element_t<I, std::tuple<Ts...>>;
+
//===----------------------------------------------------------------------===//
// Extra additions to <functional>
//===----------------------------------------------------------------------===//
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
index 862653055417..a80c6ce77306 100644
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -711,4 +711,40 @@ TEST(STLExtras, MoveRange) {
EXPECT_EQ(V4.size(), 4U);
EXPECT_TRUE(llvm::all_of(V4, HasVal));
}
+
+TEST(STLExtrasTest, TypesAreDistinct) {
+ EXPECT_TRUE((llvm::TypesAreDistinct<>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int>::value));
+ EXPECT_FALSE((llvm::TypesAreDistinct<int, int>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, float>::value));
+ EXPECT_FALSE((llvm::TypesAreDistinct<int, float, int>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, float, double>::value));
+ EXPECT_FALSE((llvm::TypesAreDistinct<int, float, double, float>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, int *>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, int &>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, int &&>::value));
+ EXPECT_TRUE((llvm::TypesAreDistinct<int, const int>::value));
+}
+
+TEST(STLExtrasTest, FirstIndexOfType) {
+ EXPECT_EQ((llvm::FirstIndexOfType<int, int>::value), 0u);
+ EXPECT_EQ((llvm::FirstIndexOfType<int, int, int>::value), 0u);
+ EXPECT_EQ((llvm::FirstIndexOfType<int, float, int>::value), 1u);
+ EXPECT_EQ((llvm::FirstIndexOfType<int const *, float, int, int const *,
+ const int>::value),
+ 2u);
+}
+
+TEST(STLExtrasTest, TypeAtIndex) {
+ EXPECT_TRUE((std::is_same<int, llvm::TypeAtIndex<0, int>>::value));
+ EXPECT_TRUE((std::is_same<int, llvm::TypeAtIndex<0, int, float>>::value));
+ EXPECT_TRUE((std::is_same<float, llvm::TypeAtIndex<1, int, float>>::value));
+ EXPECT_TRUE(
+ (std::is_same<float, llvm::TypeAtIndex<1, int, float, double>>::value));
+ EXPECT_TRUE(
+ (std::is_same<float, llvm::TypeAtIndex<1, int, float, double>>::value));
+ EXPECT_TRUE(
+ (std::is_same<double, llvm::TypeAtIndex<2, int, float, double>>::value));
+}
+
} // namespace
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