diff --git a/llvm/include/llvm/ADT/BitVector.h b/llvm/include/llvm/ADT/BitVector.h
--- a/llvm/include/llvm/ADT/BitVector.h
+++ b/llvm/include/llvm/ADT/BitVector.h
@@ -28,6 +28,45 @@
 
 namespace llvm {
 
+/// ForwardIterator for all bits.
+/// Iterators get invalidated when resize / reserve is called.
+template <typename BitVectorT> class const_all_bits_iterator_impl {
+  using size_type = typename BitVectorT::size_type;
+
+  const BitVectorT &Parent;
+  size_type Current;
+
+public:
+  const_all_bits_iterator_impl(const BitVectorT &Parent, size_type Current)
+      : Parent(Parent), Current(Current) {}
+  const_all_bits_iterator_impl(const const_all_bits_iterator_impl &) = default;
+
+  const_all_bits_iterator_impl operator++(int) {
+    auto Prev = *this;
+    ++Current;
+    return Prev;
+  }
+
+  const_all_bits_iterator_impl &operator++() {
+    ++Current;
+    return *this;
+  }
+
+  bool operator*() { return Parent[Current]; }
+
+  bool operator==(const const_all_bits_iterator_impl &Other) const {
+    assert(&Parent == &Other.Parent &&
+           "Comparing iterators from different BitVectors");
+    return Current == Other.Current;
+  }
+
+  bool operator!=(const const_all_bits_iterator_impl &Other) const {
+    assert(&Parent == &Other.Parent &&
+           "Comparing iterators from different BitVectors");
+    return Current != Other.Current;
+  }
+};
+
 /// ForwardIterator for the bits that are set.
 /// Iterators get invalidated when resize / reserve is called.
 template <typename BitVectorT> class const_set_bits_iterator_impl {
@@ -121,6 +160,11 @@
     }
   };
 
+  using const_all_bits_iterator = const_all_bits_iterator_impl<BitVector>;
+
+  const_all_bits_iterator begin() const { return {*this, 0}; }
+  const_all_bits_iterator end() const { return {*this, size()}; }
+
   typedef const_set_bits_iterator_impl<BitVector> const_set_bits_iterator;
   typedef const_set_bits_iterator set_iterator;
 
diff --git a/llvm/include/llvm/ADT/SmallBitVector.h b/llvm/include/llvm/ADT/SmallBitVector.h
--- a/llvm/include/llvm/ADT/SmallBitVector.h
+++ b/llvm/include/llvm/ADT/SmallBitVector.h
@@ -177,6 +177,11 @@
       delete getPointer();
   }
 
+  using const_all_bits_iterator = const_all_bits_iterator_impl<SmallBitVector>;
+
+  const_all_bits_iterator begin() const { return {*this, 0}; }
+  const_all_bits_iterator end() const { return {*this, size()}; }
+
   using const_set_bits_iterator = const_set_bits_iterator_impl<SmallBitVector>;
   using set_iterator = const_set_bits_iterator;
 
diff --git a/llvm/unittests/ADT/BitVectorTest.cpp b/llvm/unittests/ADT/BitVectorTest.cpp
--- a/llvm/unittests/ADT/BitVectorTest.cpp
+++ b/llvm/unittests/ADT/BitVectorTest.cpp
@@ -1143,7 +1143,31 @@
   testEmpty(E);
 }
 
-TYPED_TEST(BitVectorTest, Iterators) {
+TYPED_TEST(BitVectorTest, AllBitsIterators) {
+  TypeParam Empty;
+  EXPECT_EQ(Empty.begin(), Empty.end());
+  unsigned BitCount = 0;
+  for (bool Bit : Empty) {
+    (void)Bit;
+    BitCount++;
+  }
+  ASSERT_EQ(BitCount, 0U);
+
+  TypeParam ToFill(100, false);
+  const unsigned List[] = {1, 10, 25, 99};
+  for (unsigned Idx : List)
+    ToFill.set(Idx);
+
+  unsigned Idx = 0;
+  for (bool Bit : ToFill) {
+    ASSERT_TRUE(Bit ? llvm::is_contained(List, Idx)
+                    : !llvm::is_contained(List, Idx));
+    ++Idx;
+  }
+  ASSERT_EQ(Idx, 100U);
+}
+
+TYPED_TEST(BitVectorTest, SetBitsIterators) {
   TypeParam Filled(10, true);
   EXPECT_NE(Filled.set_bits_begin(), Filled.set_bits_end());
   unsigned Counter = 0;