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//===- DenseMapInfoVariant.h - Type traits for DenseMap<variant> *- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines DenseMapInfo traits for DenseMap<std::variant<Ts...>>.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_DENSEMAPINFOVARIANT_H
#define LLVM_ADT_DENSEMAPINFOVARIANT_H
#include "llvm/ADT/DenseMapInfo.h"
#include <utility>
#include <variant>
namespace llvm {
// Provide DenseMapInfo for variants whose all alternatives have DenseMapInfo.
template <typename... Ts> struct DenseMapInfo<std::variant<Ts...>> {
using Variant = std::variant<Ts...>;
using FirstT = std::variant_alternative_t<0, Variant>;
static inline Variant getEmptyKey() {
return Variant(std::in_place_index<0>, DenseMapInfo<FirstT>::getEmptyKey());
}
static inline Variant getTombstoneKey() {
return Variant(std::in_place_index<0>,
DenseMapInfo<FirstT>::getTombstoneKey());
}
static unsigned getHashValue(const Variant &Val) {
return std::visit(
[&Val](auto &&Alternative) {
using T = std::decay_t<decltype(Alternative)>;
// Include index in hash to make sure same value as different
// alternatives don't collide.
return DenseMapInfo<std::pair<size_t, T>>::getHashValuePiecewise(
Val.index(), Alternative);
},
Val);
}
static bool isEqual(const Variant &LHS, const Variant &RHS) {
if (LHS.index() != RHS.index())
return false;
if (LHS.valueless_by_exception())
return true;
// We want to dispatch to DenseMapInfo<T>::isEqual(LHS.get(I), RHS.get(I))
// We know the types are the same, but std::visit(V, LHS, RHS) doesn't.
// We erase the type held in LHS to void*, and dispatch over RHS.
const void *ErasedLHS =
std::visit([](const auto &LHS) -> const void * { return &LHS; }, LHS);
return std::visit(
[&](const auto &RHS) -> bool {
using T = std::remove_cv_t<std::remove_reference_t<decltype(RHS)>>;
return DenseMapInfo<T>::isEqual(*static_cast<const T *>(ErasedLHS),
RHS);
},
RHS);
}
};
} // end namespace llvm
#endif // LLVM_ADT_DENSEMAPINFOVARIANT_H
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