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//===- llvm/ADT/DenseMapInfo.h - Type traits for DenseMap -------*- 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.

///

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_DENSEMAPINFO_H

#define LLVM_ADT_DENSEMAPINFO_H

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <tuple>

#include <type_traits>

#include <utility>

#include <variant>

namespace llvm {

namespace detail {

/// Simplistic combination of 32-bit hash values into 32-bit hash values.

static inline unsigned combineHashValue(unsigned a, unsigned b) {

  uint64_t key = (uint64_t)a << 32 | (uint64_t)b;

  key += ~(key << 32);

  key ^= (key >> 22);

  key += ~(key << 13);

  key ^= (key >> 8);

  key += (key << 3);

  key ^= (key >> 15);

  key += ~(key << 27);

  key ^= (key >> 31);

  return (unsigned)key;

}

} // end namespace detail

/// An information struct used to provide DenseMap with the various necessary

/// components for a given value type `T`. `Enable` is an optional additional

/// parameter that is used to support SFINAE (generally using std::enable_if_t)

/// in derived DenseMapInfo specializations; in non-SFINAE use cases this should

/// just be `void`.

template<typename T, typename Enable = void>

struct DenseMapInfo {

  //static inline T getEmptyKey();

  //static inline T getTombstoneKey();

  //static unsigned getHashValue(const T &Val);

  //static bool isEqual(const T &LHS, const T &RHS);

};

// Provide DenseMapInfo for all pointers. Come up with sentinel pointer values

// that are aligned to alignof(T) bytes, but try to avoid requiring T to be

// complete. This allows clients to instantiate DenseMap<T*, ...> with forward

// declared key types. Assume that no pointer key type requires more than 4096

// bytes of alignment.

template<typename T>

struct DenseMapInfo<T*> {

  // The following should hold, but it would require T to be complete:

  // static_assert(alignof(T) <= (1 << Log2MaxAlign),

  //               "DenseMap does not support pointer keys requiring more than "

  //               "Log2MaxAlign bits of alignment");

  static constexpr uintptr_t Log2MaxAlign = 12;

  static inline T* getEmptyKey() {

    uintptr_t Val = static_cast<uintptr_t>(-1);

    Val <<= Log2MaxAlign;

    return reinterpret_cast<T*>(Val);

  }

  static inline T* getTombstoneKey() {

    uintptr_t Val = static_cast<uintptr_t>(-2);

    Val <<= Log2MaxAlign;

    return reinterpret_cast<T*>(Val);

  }

  static unsigned getHashValue(const T *PtrVal) {

    return (unsigned((uintptr_t)PtrVal) >> 4) ^

           (unsigned((uintptr_t)PtrVal) >> 9);

  }

  static bool isEqual(const T *LHS, const T *RHS) { return LHS == RHS; }

};

// Provide DenseMapInfo for chars.

template<> struct DenseMapInfo<char> {

  static inline char getEmptyKey() { return ~0; }

  static inline char getTombstoneKey() { return ~0 - 1; }

  static unsigned getHashValue(const char& Val) { return Val * 37U; }

  static bool isEqual(const char &LHS, const char &RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for unsigned chars.

template <> struct DenseMapInfo<unsigned char> {

  static inline unsigned char getEmptyKey() { return ~0; }

  static inline unsigned char getTombstoneKey() { return ~0 - 1; }

  static unsigned getHashValue(const unsigned char &Val) { return Val * 37U; }

  static bool isEqual(const unsigned char &LHS, const unsigned char &RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for unsigned shorts.

template <> struct DenseMapInfo<unsigned short> {

  static inline unsigned short getEmptyKey() { return 0xFFFF; }

  static inline unsigned short getTombstoneKey() { return 0xFFFF - 1; }

  static unsigned getHashValue(const unsigned short &Val) { return Val * 37U; }

  static bool isEqual(const unsigned short &LHS, const unsigned short &RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for unsigned ints.

template<> struct DenseMapInfo<unsigned> {

  static inline unsigned getEmptyKey() { return ~0U; }

  static inline unsigned getTombstoneKey() { return ~0U - 1; }

  static unsigned getHashValue(const unsigned& Val) { return Val * 37U; }

  static bool isEqual(const unsigned& LHS, const unsigned& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for unsigned longs.

template<> struct DenseMapInfo<unsigned long> {

  static inline unsigned long getEmptyKey() { return ~0UL; }

  static inline unsigned long getTombstoneKey() { return ~0UL - 1L; }

  static unsigned getHashValue(const unsigned long& Val) {

    return (unsigned)(Val * 37UL);

  }

  static bool isEqual(const unsigned long& LHS, const unsigned long& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for unsigned long longs.

template<> struct DenseMapInfo<unsigned long long> {

  static inline unsigned long long getEmptyKey() { return ~0ULL; }

  static inline unsigned long long getTombstoneKey() { return ~0ULL - 1ULL; }

  static unsigned getHashValue(const unsigned long long& Val) {

    return (unsigned)(Val * 37ULL);

  }

  static bool isEqual(const unsigned long long& LHS,

                      const unsigned long long& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for shorts.

template <> struct DenseMapInfo<short> {

  static inline short getEmptyKey() { return 0x7FFF; }

  static inline short getTombstoneKey() { return -0x7FFF - 1; }

  static unsigned getHashValue(const short &Val) { return Val * 37U; }

  static bool isEqual(const short &LHS, const short &RHS) { return LHS == RHS; }

};

// Provide DenseMapInfo for ints.

template<> struct DenseMapInfo<int> {

  static inline int getEmptyKey() { return 0x7fffffff; }

  static inline int getTombstoneKey() { return -0x7fffffff - 1; }

  static unsigned getHashValue(const int& Val) { return (unsigned)(Val * 37U); }

  static bool isEqual(const int& LHS, const int& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for longs.

template<> struct DenseMapInfo<long> {

  static inline long getEmptyKey() {

    return (1UL << (sizeof(long) * 8 - 1)) - 1UL;

  }

  static inline long getTombstoneKey() { return getEmptyKey() - 1L; }

  static unsigned getHashValue(const long& Val) {

    return (unsigned)(Val * 37UL);

  }

  static bool isEqual(const long& LHS, const long& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for long longs.

template<> struct DenseMapInfo<long long> {

  static inline long long getEmptyKey() { return 0x7fffffffffffffffLL; }

  static inline long long getTombstoneKey() { return -0x7fffffffffffffffLL-1; }

  static unsigned getHashValue(const long long& Val) {

    return (unsigned)(Val * 37ULL);

  }

  static bool isEqual(const long long& LHS,

                      const long long& RHS) {

    return LHS == RHS;

  }

};

// Provide DenseMapInfo for all pairs whose members have info.

template<typename T, typename U>

struct DenseMapInfo<std::pair<T, U>> {

  using Pair = std::pair<T, U>;

  using FirstInfo = DenseMapInfo<T>;

  using SecondInfo = DenseMapInfo<U>;

  static inline Pair getEmptyKey() {

    return std::make_pair(FirstInfo::getEmptyKey(),

                          SecondInfo::getEmptyKey());

  }

  static inline Pair getTombstoneKey() {

    return std::make_pair(FirstInfo::getTombstoneKey(),

                          SecondInfo::getTombstoneKey());

  }

  static unsigned getHashValue(const Pair& PairVal) {

    return detail::combineHashValue(FirstInfo::getHashValue(PairVal.first),

                                    SecondInfo::getHashValue(PairVal.second));

  }

  static bool isEqual(const Pair &LHS, const Pair &RHS) {

    return FirstInfo::isEqual(LHS.first, RHS.first) &&

           SecondInfo::isEqual(LHS.second, RHS.second);

  }

};

// Provide DenseMapInfo for all tuples whose members have info.

template <typename... Ts> struct DenseMapInfo<std::tuple<Ts...>> {

  using Tuple = std::tuple<Ts...>;

  static inline Tuple getEmptyKey() {

    return Tuple(DenseMapInfo<Ts>::getEmptyKey()...);

  }

  static inline Tuple getTombstoneKey() {

    return Tuple(DenseMapInfo<Ts>::getTombstoneKey()...);

  }

  template <unsigned I>

  static unsigned getHashValueImpl(const Tuple &values, std::false_type) {

    using EltType = std::tuple_element_t<I, Tuple>;

    std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;

    return detail::combineHashValue(

        DenseMapInfo<EltType>::getHashValue(std::get<I>(values)),

        getHashValueImpl<I + 1>(values, atEnd));

  }

  template <unsigned I>

  static unsigned getHashValueImpl(const Tuple &, std::true_type) {

    return 0;

  }

  static unsigned getHashValue(const std::tuple<Ts...> &values) {

    std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;

    return getHashValueImpl<0>(values, atEnd);

  }

  template <unsigned I>

  static bool isEqualImpl(const Tuple &lhs, const Tuple &rhs, std::false_type) {

    using EltType = std::tuple_element_t<I, Tuple>;

    std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;

    return DenseMapInfo<EltType>::isEqual(std::get<I>(lhs), std::get<I>(rhs)) &&

           isEqualImpl<I + 1>(lhs, rhs, atEnd);

  }

  template <unsigned I>

  static bool isEqualImpl(const Tuple &, const Tuple &, std::true_type) {

    return true;

  }

  static bool isEqual(const Tuple &lhs, const Tuple &rhs) {

    std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;

    return isEqualImpl<0>(lhs, rhs, atEnd);

  }

};

// 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 detail::combineHashValue(

              DenseMapInfo<size_t>::getHashValue(Val.index()),

              DenseMapInfo<T>::getHashValue(Alternative));

        },

        Val);

  }

  static bool isEqual(const Variant &LHS, const Variant &RHS) {

    return LHS == RHS;

  }

};

} // end namespace llvm

#endif // LLVM_ADT_DENSEMAPINFO_H