Index: include/llvm/ADT/OptionSet.h
===================================================================
--- /dev/null
+++ include/llvm/ADT/OptionSet.h
@@ -0,0 +1,135 @@
+//===--- OptionSet.h - Sets of boolean options ------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the OptionSet class template.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_OPTIONSET_H
+#define LLVM_ADT_OPTIONSET_H
+
+#include "llvm/ADT/None.h"
+#include "llvm/Support/Compiler.h"
+
+#include <type_traits>
+#include <cstdint>
+
+namespace llvm {
+
+/// The class template \c OptionSet captures a set of options stored as the
+/// bits in an unsigned integral value.
+///
+/// Each option corresponds to a particular flag value in the provided
+/// enumeration type (\c Flags). The option set provides ways to add options,
+/// remove options, intersect sets, etc., providing a thin type-safe layer
+/// over the underlying unsigned value.
+///
+/// \tparam Flags An enumeration type that provides the individual flags
+/// for options. Each enumerator should have a power-of-two value, indicating
+/// which bit it is associated with.
+///
+/// \tparam StorageType The unsigned integral type to use to store the flags
+/// enabled within this option set. This defaults to the unsigned form of the
+/// underlying type of the enumeration.
+template<typename Flags,
+         typename StorageType = typename std::make_unsigned<
+                                  typename std::underlying_type<Flags>::type
+                                 >::type>
+class OptionSet {
+  StorageType Storage;
+
+public:
+  /// Create an empty option set.
+  OptionSet() : Storage() { }
+
+  /// Create an empty option set.
+  OptionSet(llvm::NoneType) : Storage() { }
+
+  /// Create an option set with only the given option set.
+  OptionSet(Flags flag) : Storage(static_cast<StorageType>(flag)) { }
+
+  /// Create an option set from raw storage.
+  explicit OptionSet(StorageType storage) : Storage(storage) { }
+
+  /// Check whether an option set is non-empty.
+  explicit operator bool() const { return Storage != 0; }
+
+  /// Explicitly convert an option set to its underlying storage.
+  explicit operator StorageType() const { return Storage; }
+
+  /// Explicitly convert an option set to intptr_t, for use in
+  /// llvm::PointerIntPair.
+  ///
+  /// This member is not present if the underlying type is bigger than
+  /// a pointer.
+  template <typename T = std::intptr_t>
+  explicit operator typename std::enable_if<sizeof(StorageType) <= sizeof(T),
+      std::intptr_t>::type () const {
+    return static_cast<intptr_t>(Storage);
+  }
+
+  /// Retrieve the "raw" representation of this option set.
+  StorageType toRaw() const { return Storage; }
+  
+  /// Determine whether this option set contains all of the options in the
+  /// given set.
+  bool contains(OptionSet set) const {
+    return !static_cast<bool>(set - *this);
+  }
+
+  /// Produce the union of two option sets.
+  friend OptionSet operator|(OptionSet lhs, OptionSet rhs) {
+    return OptionSet(lhs.Storage | rhs.Storage);
+  }
+
+  /// Produce the union of two option sets.
+  friend OptionSet &operator|=(OptionSet &lhs, OptionSet rhs) {
+    lhs.Storage |= rhs.Storage;
+    return lhs;
+ }
+
+  /// Produce the intersection of two option sets.
+  friend OptionSet operator&(OptionSet lhs, OptionSet rhs) {
+    return OptionSet(lhs.Storage & rhs.Storage);
+  }
+
+  /// Produce the intersection of two option sets.
+  friend OptionSet &operator&=(OptionSet &lhs, OptionSet rhs) {
+    lhs.Storage &= rhs.Storage;
+    return lhs;
+  }
+
+  /// Produce the difference of two option sets.
+  friend OptionSet operator-(OptionSet lhs, OptionSet rhs) {
+    return OptionSet(lhs.Storage & ~rhs.Storage);
+  }
+
+  /// Produce the intersection of two option sets.
+  friend OptionSet &operator-=(OptionSet &lhs, OptionSet rhs) {
+    lhs.Storage &= ~rhs.Storage;
+    return lhs;
+  }
+
+private:
+#if !defined(_MSC_VER) || LLVM_MSC_PREREQ(1900)
+  // MSVC 2013 has an ICE due to the following.
+  template <typename T>
+  static auto _checkResultTypeOperatorOr(T t) -> decltype(t | t) { return T(); }
+
+  static void _checkResultTypeOperatorOr(...) {}
+
+  static_assert(!std::is_same<decltype(_checkResultTypeOperatorOr(Flags())),
+                              Flags>::value,
+                "operator| should produce an OptionSet");
+#endif
+};
+
+}
+
+#endif
Index: unittests/ADT/CMakeLists.txt
===================================================================
--- unittests/ADT/CMakeLists.txt
+++ unittests/ADT/CMakeLists.txt
@@ -24,6 +24,7 @@
   MakeUniqueTest.cpp
   MapVectorTest.cpp
   OptionalTest.cpp
+  OptionSetTest.cpp
   PackedVectorTest.cpp
   PointerEmbeddedIntTest.cpp
   PointerIntPairTest.cpp
Index: unittests/ADT/OptionSetTest.cpp
===================================================================
--- /dev/null
+++ unittests/ADT/OptionSetTest.cpp
@@ -0,0 +1,117 @@
+//===- llvm/unittests/ADT/OptionSetTest.cpp -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/OptionSet.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+TEST(OptionSet, contains) {
+  enum class Flags {
+    A = 1 << 0,
+    B = 1 << 1,
+    C = 1 << 2
+  };
+
+  OptionSet<Flags> emptySet;
+  OptionSet<Flags> aSet = Flags::A;
+  OptionSet<Flags> abSet = aSet | Flags::B;
+  OptionSet<Flags> abcSet = abSet | Flags::C;
+  OptionSet<Flags> bcSet = abcSet - Flags::A;
+  OptionSet<Flags> cSet = bcSet - Flags::B;
+
+  EXPECT_TRUE(emptySet.contains(emptySet));
+  EXPECT_FALSE(emptySet.contains(aSet));
+  EXPECT_FALSE(emptySet.contains(abSet));
+  EXPECT_FALSE(emptySet.contains(abcSet));
+  EXPECT_FALSE(emptySet.contains(bcSet));
+  EXPECT_FALSE(emptySet.contains(cSet));
+
+  EXPECT_TRUE(aSet.contains(emptySet));
+  EXPECT_TRUE(aSet.contains(aSet));
+  EXPECT_FALSE(aSet.contains(abSet));
+  EXPECT_FALSE(aSet.contains(abcSet));
+  EXPECT_FALSE(aSet.contains(bcSet));
+  EXPECT_FALSE(aSet.contains(cSet));
+
+  EXPECT_TRUE(abSet.contains(emptySet));
+  EXPECT_TRUE(abSet.contains(aSet));
+  EXPECT_TRUE(abSet.contains(abSet));
+  EXPECT_FALSE(abSet.contains(abcSet));
+  EXPECT_FALSE(abSet.contains(bcSet));
+  EXPECT_FALSE(abSet.contains(cSet));
+
+  EXPECT_TRUE(abcSet.contains(emptySet));
+  EXPECT_TRUE(abcSet.contains(aSet));
+  EXPECT_TRUE(abcSet.contains(abSet));
+  EXPECT_TRUE(abcSet.contains(abcSet));
+  EXPECT_TRUE(abcSet.contains(bcSet));
+  EXPECT_TRUE(abcSet.contains(cSet));
+}
+
+
+TEST(OptionSet, intptr_t) {
+  enum class Small : int8_t {
+    A = 1 << 0
+  };
+
+  OptionSet<Small> small = Small::A;
+  EXPECT_EQ(static_cast<intptr_t>(Small::A), static_cast<intptr_t>(small));
+
+
+#if !defined(_MSC_VER) || LLVM_MSC_PREREQ(1900)
+  // Fails to compile in MSVC 2013 because it lacks proper constexpr support
+  // for std::numeric_limits.
+  enum class UPtr : uintptr_t {
+    A = std::numeric_limits<uintptr_t>::max()
+  };
+
+  OptionSet<UPtr> uptr = UPtr::A;
+  EXPECT_EQ(static_cast<intptr_t>(UPtr::A), static_cast<intptr_t>(uptr));
+
+
+  enum class Ptr : intptr_t {
+    A = std::numeric_limits<intptr_t>::min()
+  };
+
+  OptionSet<Ptr> ptr = Ptr::A;
+  EXPECT_EQ(static_cast<intptr_t>(Ptr::A), static_cast<intptr_t>(ptr));
+#endif
+}
+
+#if !defined(_MSC_VER) || LLVM_MSC_PREREQ(1900)
+// This fails on MSVC 2013; is_constructible returns true despite
+// sizeof(intptr_t) == 4 and sizeof(long long) == 8.
+TEST(OptionSet, intptr_t_isConstructible) {
+  // First check that std::is_constructible counts explicit conversion
+  // operators.
+  class AlwaysConvertible {
+  public:
+    explicit operator intptr_t () const { return 0; }
+  };
+
+  if (!std::is_constructible<intptr_t, AlwaysConvertible>::value) {
+    // std::is_constructible doesn't test what we want it to. Just exit early.
+    return;
+  }
+
+  enum class LongLong : unsigned long long {
+    A = 1
+  };
+  bool isConvertible =
+      std::is_constructible<intptr_t, OptionSet<LongLong>>::value;
+
+  if (sizeof(intptr_t) < sizeof(long long)) {
+    EXPECT_FALSE(isConvertible);
+  } else {
+    EXPECT_TRUE(isConvertible);
+  }
+}
+#endif
+