diff --git a/llvm/include/llvm/ADT/Bitfields.h b/llvm/include/llvm/ADT/Bitfields.h
new file mode 100644
--- /dev/null
+++ b/llvm/include/llvm/ADT/Bitfields.h
@@ -0,0 +1,273 @@
+//===-- llvm/ADT/Bitfield.h - Get and Set bits in an integer ---*- 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 implements methods to test, set and extract typed bits from packed
+/// unsigned integers.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_BITFIELDS_H
+#define LLVM_ADT_BITFIELDS_H
+
+#include <cassert>
+#include <climits> // CHAR_BIT
+#include <cstddef> // size_t
+#include <cstdint> // uintXX_t
+#include <limits>  // numeric_limits
+#include <type_traits>
+
+/// Helpers to pack / unpack typed bitfields into an unsigned integer.
+/// e.g.
+///
+///  uint8_t Storage = 0;
+///
+///  // Store and retrieve a single bit as bool.
+///  using Bool = Bitfield<bool, 0, 1>;
+///  bitfield<Bool>(Storage) = true;
+///  EXPECT_EQ(Storage, 0b00000001);
+///  //                          ^
+///  EXPECT_EQ(bitfield<Bool>(Storage), true);
+///
+///  // Store and retrieve a 2 bit typed enum.
+///  // Note: enum underlying type must be unsigned.
+///  enum class SuitEnum : uint8_t { CLUBS, DIAMONDS, HEARTS, SPADES };
+///  // Note: enum maximum value needs to be passed in.
+///  using Suit = Bitfield<SuitEnum, 1, 2, SuitEnum::SPADES>;
+///  bitfield<Suit>(Storage) = SuitEnum::HEARTS;
+///  EXPECT_EQ(Storage, 0b00000101);
+///  //                        ^^
+///  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::HEARTS);
+///
+///  // Store and retrieve a 5 bit value as unsigned.
+///  using Value = Bitfield<unsigned, 3, 5>;
+///  bitfield<Value>(Storage) = 10;
+///  EXPECT_EQ(Storage, 0b01010101);
+///  //                   ^^^^^
+///  EXPECT_EQ(bitfield<Value>(Storage), 10U);
+///
+///  // Interpret the same 5 bit value as signed.
+///  using SignedValue = Bitfield<int, 3, 5>;
+///  bitfield<SignedValue>(Storage) = -2;
+///  EXPECT_EQ(Storage, 0b11110101);
+///  //                   ^^^^^
+///  EXPECT_EQ(bitfield<SignedValue>(Storage), -2);
+///
+///  // Ability to efficiently test if a field is non zero.
+///  EXPECT_TRUE(bitfield<Value>(Storage).isSet());
+///
+///  // Alter Storage changes value.
+///  Storage = 0;
+///  EXPECT_EQ(bitfield<Bool>(Storage), false);
+///  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::CLUBS);
+///  EXPECT_EQ(bitfield<Value>(Storage), 0U);
+///  EXPECT_EQ(bitfield<SignedValue>(Storage), 0);
+///
+///  Storage = 255;
+///  EXPECT_EQ(bitfield<Bool>(Storage), true);
+///  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::SPADES);
+///  EXPECT_EQ(bitfield<Value>(Storage), 31U);
+///  EXPECT_EQ(bitfield<SignedValue>(Storage), -1);
+
+namespace llvm {
+
+namespace details {
+
+/// A struct defining useful bit patterns for n-bits integer types.
+template <typename T, unsigned Bits> struct BitPatterns {
+  // Bit patterns are forged using the equivalent `Unsigned` type because of
+  // undefined operations over signed types (e.g. Bitwise shift operators).
+  // Moreover same size casting from unsigned to signed is well defined but not
+  // the other way around.
+  using Unsigned = typename std::make_unsigned<T>::type;
+  static_assert(sizeof(Unsigned) == sizeof(T), "Types must have same size");
+
+  static constexpr unsigned TypeBits = sizeof(Unsigned) * CHAR_BIT;
+  static_assert(TypeBits >= Bits, "n-bit must fit in T");
+
+  // e.g. with TypeBits == 8 and Bits == 6.
+  static constexpr Unsigned AllZeros = Unsigned(0);                  // 00000000
+  static constexpr Unsigned AllOnes = ~Unsigned(0);                  // 11111111
+  static constexpr Unsigned Umin = AllZeros;                         // 00000000
+  static constexpr Unsigned Umax = AllOnes >> (TypeBits - Bits);     // 00111111
+  static constexpr Unsigned SignBitMask = Unsigned(1) << (Bits - 1); // 00100000
+  static constexpr Unsigned Smax = Umax >> 1U;                       // 00011111
+  static constexpr Unsigned Smin = ~Smax;                            // 11100000
+  static constexpr Unsigned SignExtend = Smin << 1U;                 // 11000000
+};
+
+/// `Compressor` is used to manipulate the bits of a (possibly signed) integer
+/// type so it can be packed and unpacked into a `bits` sized integer,
+/// `Compressor` is specialized on signed-ness so no runtime cost is incurred.
+/// The `pack` method also checks that the passed in `UserValue` is valid.
+template <typename T, unsigned Bits, bool = std::is_unsigned<T>::value>
+struct Compressor {
+  static_assert(std::is_unsigned<T>::value, "T is unsigned");
+  using BP = BitPatterns<T, Bits>;
+
+  static T pack(T UserValue, T UserMaxValue) {
+    assert(UserValue <= UserMaxValue && "value is too big");
+    assert(UserValue <= BP::Umax && "value is too big");
+    return UserValue;
+  }
+
+  static T unpack(T StorageValue) { return StorageValue; }
+};
+
+template <typename T, unsigned Bits> struct Compressor<T, Bits, false> {
+  static_assert(std::is_signed<T>::value, "T is signed");
+  using BP = BitPatterns<T, Bits>;
+
+  static T pack(T UserValue, T UserMaxValue) {
+    assert(UserValue <= UserMaxValue && "value is too big");
+    assert(UserValue <= T(BP::Smax) && "value is too big");
+    assert(UserValue >= T(BP::Smin) && "value is too small");
+    if (UserValue < 0)
+      UserValue &= ~BP::SignExtend;
+    return UserValue;
+  }
+
+  static T unpack(T StorageValue) {
+    if (StorageValue >= T(BP::SignBitMask))
+      StorageValue |= BP::SignExtend;
+    return StorageValue;
+  }
+};
+
+/// `BitfieldProperties` stores important properties about the Bitfield.
+/// It only deals with proper integer types. The conversion from/to enum/bool
+/// are done in the public API outside of this template.
+template <typename UserType, typename T, unsigned Offset, unsigned Bits,
+          T MaxValue = std::numeric_limits<T>::max(),
+          T MinValue = std::numeric_limits<T>::min()>
+struct BitfieldProperties {
+  using IntegerType = T;
+  static_assert(std::is_integral<T>::value &&
+                    std::numeric_limits<T>::is_integer,
+                "T must be an integer type");
+
+  static constexpr size_t TypeBits = sizeof(IntegerType) * CHAR_BIT;
+  static constexpr unsigned FirstBit = Offset;
+  static constexpr unsigned LastBit = Offset + Bits;
+
+  static_assert(Bits > 0, "Bits must be non zero");
+  static_assert(Bits <= TypeBits, "Bits may not be greater than T size");
+
+  /// Impl is where Bifield description and storage are put together to interact
+  /// with values.
+  template <typename StorageType> struct Impl {
+  private:
+    static_assert(std::is_unsigned<StorageType>::value,
+                  "Storage must be unsigned");
+    using C = Compressor<IntegerType, Bits>;
+    using BP = BitPatterns<StorageType, Bits>;
+
+    static constexpr size_t StorageBits = sizeof(StorageType) * CHAR_BIT;
+    static_assert(FirstBit <= StorageBits, "Data must fit in mask");
+    static_assert(LastBit <= StorageBits, "Data must fit in mask");
+    static constexpr StorageType Mask = BP::Umax << Offset;
+
+    /// Checks `UserValue` is within bounds and packs it between `FirstBit`
+    /// and `LastBit` of `Packed` leaving the rest unchanged.
+    static void update(StorageType &Packed, IntegerType UserValue) {
+      const StorageType StorageValue = C::pack(UserValue, MaxValue);
+      Packed &= ~Mask;
+      Packed |= StorageValue << Offset;
+    }
+
+    /// Interprets bits between `FirstBit` and `LastBit` of `Packed` as an
+    /// `IntegerType`.
+    static IntegerType extract(StorageType Packed) {
+      const StorageType StorageValue = (Packed & Mask) >> Offset;
+      return C::unpack(StorageValue);
+    }
+
+    StorageType *StoragePtr = nullptr;
+
+  public:
+    Impl(StorageType &StorageValue) : StoragePtr(&StorageValue) {}
+
+    Impl(const Impl &) = delete;
+    Impl(Impl &&) = default; // needed to return the value
+    Impl &operator=(const Impl &) = delete;
+    Impl &operator=(Impl &&) = delete;
+
+    StorageType isSet() const { return *StoragePtr & Mask; }
+
+    operator UserType() const {
+      return static_cast<UserType>(extract(*StoragePtr));
+    }
+
+    Impl &operator=(UserType UserValue) {
+      update(*StoragePtr, static_cast<IntegerType>(UserValue));
+      return *this;
+    }
+  };
+};
+
+/// `Bitfield` deals with the following type:
+/// - unsigned enums
+/// - signed and unsigned integer
+/// - `bool`
+/// Internally though we only manipulate integer with well defined and
+/// consistent semantic, this excludes typed enums and `bool` that are
+/// replaced with their unsigned counterparts.
+/// The correct type is restored in the public API.
+template <typename T, bool = std::is_enum<T>::value>
+struct ResolveUnderlyingType {
+  using type = typename std::underlying_type<T>::type;
+};
+template <typename T> struct ResolveUnderlyingType<T, false> {
+  using type = T;
+};
+template <> struct ResolveUnderlyingType<bool, false> {
+  /// In case sizeof(bool) != 1, replace `void` by an additionnal
+  /// std::conditionnal.
+  using type = std::conditional<sizeof(bool) == 1, uint8_t, void>::type;
+};
+
+} // namespace details
+
+/// A struct to hold the bitfield informations.
+/// \param T, the type of the field once in unpacked form,
+/// \param Offset, the position of the first bit,
+/// \param Size, the size of the field,
+/// \param MaxValue, For enums the maximum enum allowed.
+template <typename T, unsigned Offset, unsigned Size,
+          T MaxValue = std::is_enum<T>::value
+                           ? T(0) // coupled with static_assert below
+                           : std::numeric_limits<T>::max()>
+struct Bitfield {
+  using Type = T;
+  using IntegerType = typename details::ResolveUnderlyingType<T>::type;
+  using Properties =
+      typename details::BitfieldProperties<T, IntegerType, Offset, Size,
+                                           static_cast<IntegerType>(MaxValue)>;
+
+  static_assert(!std::is_enum<T>::value || MaxValue != T(0),
+                "Enum Bitfields must provide a MaxValue");
+  static_assert(!std::is_enum<T>::value || std::is_unsigned<IntegerType>::value,
+                "Enum must be unsigned");
+};
+
+template <typename Bitfield, typename StorageType>
+auto bitfield(StorageType &StorageValue) {
+  using Impl = typename Bitfield::Properties::template Impl<StorageType>;
+  return Impl(StorageValue);
+}
+
+/// Returns whether the two bitfields share common bits.
+template <typename A, typename B> static constexpr bool isOverlapping() {
+  using PA = typename A::Properties;
+  using PB = typename B::Properties;
+  return PA::LastBit > PB::FirstBit && PB::LastBit > PA::FirstBit;
+}
+
+} // namespace llvm
+
+#endif // LLVM_ADT_BITFIELDS_H
diff --git a/llvm/unittests/ADT/BitFieldsTest.cpp b/llvm/unittests/ADT/BitFieldsTest.cpp
new file mode 100644
--- /dev/null
+++ b/llvm/unittests/ADT/BitFieldsTest.cpp
@@ -0,0 +1,244 @@
+//===- llvm/unittests/ADT/BitFieldsTest.cpp - BitFields unit tests --------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Bitfields.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(BitfieldsTest, Example) {
+  uint8_t Storage = 0;
+
+  // Store and retrieve a single bit as bool.
+  using Bool = Bitfield<bool, 0, 1>;
+  bitfield<Bool>(Storage) = true;
+  EXPECT_EQ(Storage, 0b00000001);
+  //                          ^
+  EXPECT_EQ(bitfield<Bool>(Storage), true);
+
+  // Store and retrieve a 2 bit typed enum.
+  // Note: enum underlying type must be unsigned.
+  enum class SuitEnum : uint8_t { CLUBS, DIAMONDS, HEARTS, SPADES };
+  // Note: enum maximum value needs to be passed in.
+  using Suit = Bitfield<SuitEnum, 1, 2, SuitEnum::SPADES>;
+  bitfield<Suit>(Storage) = SuitEnum::HEARTS;
+  EXPECT_EQ(Storage, 0b00000101);
+  //                        ^^
+  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::HEARTS);
+
+  // Store and retrieve a 5 bit value as unsigned.
+  using Value = Bitfield<unsigned, 3, 5>;
+  bitfield<Value>(Storage) = 10;
+  EXPECT_EQ(Storage, 0b01010101);
+  //                   ^^^^^
+  EXPECT_EQ(bitfield<Value>(Storage), 10U);
+
+  // Interpret the same 5 bit value as signed.
+  using SignedValue = Bitfield<int, 3, 5>;
+  bitfield<SignedValue>(Storage) = -2;
+  EXPECT_EQ(Storage, 0b11110101);
+  //                   ^^^^^
+  EXPECT_EQ(bitfield<SignedValue>(Storage), -2);
+
+  // Ability to efficiently test if a field is non zero.
+  EXPECT_TRUE(bitfield<Value>(Storage).isSet());
+
+  // Alter Storage changes value.
+  Storage = 0;
+  EXPECT_EQ(bitfield<Bool>(Storage), false);
+  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::CLUBS);
+  EXPECT_EQ(bitfield<Value>(Storage), 0U);
+  EXPECT_EQ(bitfield<SignedValue>(Storage), 0);
+
+  Storage = 255;
+  EXPECT_EQ(bitfield<Bool>(Storage), true);
+  EXPECT_EQ(bitfield<Suit>(Storage), SuitEnum::SPADES);
+  EXPECT_EQ(bitfield<Value>(Storage), 31U);
+  EXPECT_EQ(bitfield<SignedValue>(Storage), -1);
+}
+
+TEST(BitfieldsTest, FirstBit) {
+  uint8_t Storage = 0;
+  using FirstBit = Bitfield<bool, 0, 1>;
+  // Set true
+  bitfield<FirstBit>(Storage) = true;
+  EXPECT_EQ(bitfield<FirstBit>(Storage), true);
+  EXPECT_EQ(Storage, 0x1ULL);
+  // Set false
+  bitfield<FirstBit>(Storage) = false;
+  EXPECT_EQ(bitfield<FirstBit>(Storage), false);
+  EXPECT_EQ(Storage, 0x0ULL);
+}
+
+TEST(BitfieldsTest, SecondBit) {
+  uint8_t Storage = 0;
+  using SecondBit = Bitfield<bool, 1, 1>;
+  // Set true
+  bitfield<SecondBit>(Storage) = true;
+  EXPECT_EQ(bitfield<SecondBit>(Storage), true);
+  EXPECT_EQ(Storage, 0x2ULL);
+  // Set false
+  bitfield<SecondBit>(Storage) = false;
+  EXPECT_EQ(bitfield<SecondBit>(Storage), false);
+  EXPECT_EQ(Storage, 0x0ULL);
+}
+
+TEST(BitfieldsTest, LastBit) {
+  uint8_t Storage = 0;
+  using LastBit = Bitfield<bool, 7, 1>;
+  // Set true
+  bitfield<LastBit>(Storage) = true;
+  EXPECT_EQ(bitfield<LastBit>(Storage), true);
+  EXPECT_EQ(Storage, 0x80ULL);
+  // Set false
+  bitfield<LastBit>(Storage) = false;
+  EXPECT_EQ(bitfield<LastBit>(Storage), false);
+  EXPECT_EQ(Storage, 0x0ULL);
+}
+
+TEST(BitfieldsTest, LastBitUint64) {
+  uint64_t Storage = 0;
+  using LastBit = Bitfield<bool, 63, 1>;
+  // Set true
+  bitfield<LastBit>(Storage) = true;
+  EXPECT_EQ(bitfield<LastBit>(Storage), true);
+  EXPECT_EQ(Storage, 0x8000000000000000ULL);
+  // Set false
+  bitfield<LastBit>(Storage) = false;
+  EXPECT_EQ(bitfield<LastBit>(Storage), false);
+  EXPECT_EQ(Storage, 0x0ULL);
+}
+
+TEST(BitfieldsTest, Enum) {
+  enum Enum : unsigned { Zero = 0, Two = 2, LAST = Two };
+
+  uint8_t Storage = 0;
+  using OrderingField = Bitfield<Enum, 1, 2, LAST>;
+  EXPECT_EQ(bitfield<OrderingField>(Storage), Zero);
+  bitfield<OrderingField>(Storage) = Two;
+  EXPECT_EQ(bitfield<OrderingField>(Storage), Two);
+  EXPECT_EQ(Storage, 0b00000100);
+  // value 2 in             ^^
+}
+
+TEST(BitfieldsTest, EnumClass) {
+  enum class Enum : unsigned { Zero = 0, Two = 2, LAST = Two };
+
+  uint8_t Storage = 0;
+  using OrderingField = Bitfield<Enum, 1, 2, Enum::LAST>;
+  EXPECT_EQ(bitfield<OrderingField>(Storage), Enum::Zero);
+  bitfield<OrderingField>(Storage) = Enum::Two;
+  EXPECT_EQ(bitfield<OrderingField>(Storage), Enum::Two);
+  EXPECT_EQ(Storage, 0b00000100);
+  // value 2 in             ^^
+}
+
+TEST(BitfieldsTest, OneBitSigned) {
+  uint8_t Storage = 0;
+  using SignedField = Bitfield<int, 1, 1>;
+  EXPECT_EQ(bitfield<SignedField>(Storage), 0);
+  EXPECT_EQ(Storage, 0b00000000);
+  // value 0 in              ^
+  bitfield<SignedField>(Storage) = -1;
+  EXPECT_EQ(bitfield<SignedField>(Storage), -1);
+  EXPECT_EQ(Storage, 0b00000010);
+  // value 1 in              ^
+}
+
+TEST(BitfieldsTest, TwoBitSigned) {
+  uint8_t Storage = 0;
+  using SignedField = Bitfield<int, 1, 2>;
+  EXPECT_EQ(bitfield<SignedField>(Storage), 0);
+  EXPECT_EQ(Storage, 0b00000000);
+  // value 0 in             ^^
+  bitfield<SignedField>(Storage) = 1;
+  EXPECT_EQ(bitfield<SignedField>(Storage), 1);
+  EXPECT_EQ(Storage, 0b00000010);
+  // value 1 in             ^^
+  bitfield<SignedField>(Storage) = -1;
+  EXPECT_EQ(bitfield<SignedField>(Storage), -1);
+  EXPECT_EQ(Storage, 0b00000110);
+  // value -1 in            ^^
+  bitfield<SignedField>(Storage) = -2;
+  EXPECT_EQ(bitfield<SignedField>(Storage), -2);
+  EXPECT_EQ(Storage, 0b00000100);
+  // value -2 in            ^^
+}
+
+TEST(BitfieldsTest, isOverlapping) {
+  //    01234567
+  // A: --------
+  // B:    ---
+  // C:  ---
+  // D:     ---
+  using A = Bitfield<unsigned, 0, 8>;
+  using B = Bitfield<unsigned, 3, 3>;
+  using C = Bitfield<unsigned, 1, 3>;
+  using D = Bitfield<unsigned, 4, 3>;
+  EXPECT_TRUE((isOverlapping<A, B>()));
+  EXPECT_TRUE((isOverlapping<A, C>()));
+  EXPECT_TRUE((isOverlapping<A, B>()));
+  EXPECT_TRUE((isOverlapping<A, D>()));
+
+  EXPECT_TRUE((isOverlapping<B, C>()));
+  EXPECT_TRUE((isOverlapping<B, D>()));
+  EXPECT_FALSE((isOverlapping<C, D>()));
+}
+
+TEST(BitfieldsTest, FullUint64) {
+  uint64_t Storage = 0;
+  using Value = Bitfield<uint64_t, 0, 64>;
+  bitfield<Value>(Storage) = -1ULL;
+  EXPECT_EQ(bitfield<Value>(Storage), -1ULL);
+  bitfield<Value>(Storage) = 0ULL;
+  EXPECT_EQ(bitfield<Value>(Storage), 0ULL);
+}
+
+TEST(BitfieldsTest, FullInt64) {
+  uint64_t Storage = 0;
+  using Value = Bitfield<int64_t, 0, 64>;
+  bitfield<Value>(Storage) = -1;
+  EXPECT_EQ(bitfield<Value>(Storage), -1);
+  bitfield<Value>(Storage) = 0;
+  EXPECT_EQ(bitfield<Value>(Storage), 0);
+}
+
+#ifdef EXPECT_DEBUG_DEATH
+
+TEST(BitfieldsTest, ValueTooBigBool) {
+  uint64_t Storage = 0;
+  using A = Bitfield<unsigned, 0, 1>;
+  bitfield<A>(Storage) = true;
+  bitfield<A>(Storage) = false;
+  EXPECT_DEBUG_DEATH(bitfield<A>(Storage) = 2, "value is too big");
+}
+
+TEST(BitfieldsTest, ValueTooBigInt) {
+  uint64_t Storage = 0;
+  using A = Bitfield<unsigned, 0, 2>;
+  bitfield<A>(Storage) = 3;
+  EXPECT_DEBUG_DEATH(bitfield<A>(Storage) = 4, "value is too big");
+  EXPECT_DEBUG_DEATH(bitfield<A>(Storage) = -1, "value is too big");
+}
+
+TEST(BitfieldsTest, ValueTooBigBounded) {
+  uint8_t Storage = 0;
+  using A = Bitfield<int, 1, 2>;
+  bitfield<A>(Storage) = 1;
+  bitfield<A>(Storage) = 0;
+  bitfield<A>(Storage) = -1;
+  bitfield<A>(Storage) = -2;
+  EXPECT_DEBUG_DEATH(bitfield<A>(Storage) = 2, "value is too big");
+  EXPECT_DEBUG_DEATH(bitfield<A>(Storage) = -3, "value is too small");
+}
+
+#endif
+
+} // namespace
diff --git a/llvm/unittests/ADT/CMakeLists.txt b/llvm/unittests/ADT/CMakeLists.txt
--- a/llvm/unittests/ADT/CMakeLists.txt
+++ b/llvm/unittests/ADT/CMakeLists.txt
@@ -8,6 +8,7 @@
   APIntTest.cpp
   APSIntTest.cpp
   ArrayRefTest.cpp
+  BitFieldsTest.cpp
   BitmaskEnumTest.cpp
   BitVectorTest.cpp
   BreadthFirstIteratorTest.cpp