Index: include/llvm/Support/CastingIterators.h
===================================================================
--- /dev/null
+++ include/llvm/Support/CastingIterators.h
@@ -0,0 +1,70 @@
+//===- llvm/Support/CastingIterators.h ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CASTING_ITERATORS_H
+#define LLVM_SUPPORT_CASTING_ITERATORS_H
+
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Casting.h"
+#include <utility>
+
+namespace llvm {
+
+namespace detail {
+
+/// Functor used as the predicate in a dyn_cast_iterator.
+template<typename DerivedT>
+struct dyn_predicate {
+  template<typename BaseT>
+  bool operator()(const BaseT *Base) const { return isa<DerivedT>(Base); }
+};
+
+} // end namespace detail
+
+/// Iterator adapter that 'dyn_cast's the elements of the given inner iterators
+/// and filters out the failed casts.
+template<typename WrappedIteratorT, typename DerivedT>
+struct dyn_cast_iterator
+    : filter_iterator<WrappedIteratorT, detail::dyn_predicate<DerivedT>> {
+  using FilterIt =
+      filter_iterator<WrappedIteratorT, detail::dyn_predicate<DerivedT>>;
+
+  dyn_cast_iterator(WrappedIteratorT Begin, WrappedIteratorT End)
+      : FilterIt(std::move(Begin), std::move(End), /* predicate */{}) {}
+
+  auto operator*() const -> decltype(cast<DerivedT>(FilterIt::operator*())) {
+    // Perform the cast on dereference.
+    // The filtering ensures that the dynamic type is correct.
+    return cast<DerivedT>(FilterIt::operator*());
+  }
+};
+
+/// Make a dyn_cast_iterator and infer the wrapped iterator type.
+template<typename DerivedT, typename WrappedIteratorT>
+dyn_cast_iterator<WrappedIteratorT, DerivedT>
+make_dyn_cast_iterator(WrappedIteratorT Begin, WrappedIteratorT End) {
+  return dyn_cast_iterator<WrappedIteratorT, DerivedT>(
+             std::move(Begin), std::move(End));
+}
+
+/// Make a dyn_cast_iterator range from the input range.
+template<typename DerivedT, typename RangeT>
+auto make_dyn_cast_range(const RangeT &Rng)
+    -> iterator_range<dyn_cast_iterator<decltype(std::begin(Rng)), DerivedT>> {
+  using IterT =
+      dyn_cast_iterator<decltype(std::begin(Rng)), DerivedT>;
+
+  return make_range(IterT(std::begin(Rng), std::end(Rng)),
+                    IterT(std::end(Rng), std::end(Rng)));
+}
+
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_CASTING_ITERATORS_H
Index: unittests/Support/CMakeLists.txt
===================================================================
--- unittests/Support/CMakeLists.txt
+++ unittests/Support/CMakeLists.txt
@@ -13,6 +13,7 @@
   CachePruningTest.cpp
   CrashRecoveryTest.cpp
   Casting.cpp
+  CastingIterators.cpp
   CheckedArithmeticTest.cpp
   Chrono.cpp
   CommandLineTest.cpp
Index: unittests/Support/CastingIterators.cpp
===================================================================
--- /dev/null
+++ unittests/Support/CastingIterators.cpp
@@ -0,0 +1,96 @@
+//===- llvm/unittest/Support/CastingIterators.h -----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/CastingIterators.h"
+#include "gtest/gtest.h"
+
+#include <array>
+#include <cassert>
+
+using namespace llvm;
+
+namespace {
+
+struct Number {
+  unsigned getVal() const { return Val; }
+  virtual ~Number() = default;
+protected:
+  Number(unsigned Val) : Val(Val) {}
+private:
+  unsigned Val;
+};
+
+struct EvenNumber : Number {
+  EvenNumber(unsigned Val) : Number(Val) {
+    assert((Val % 2) == 0 && "Not an even number!");
+  }
+  static bool classof(const Number *Num) { return (Num->getVal() % 2) == 0; }
+};
+
+struct OddNumber : Number {
+  OddNumber(unsigned Val) : Number(Val) {
+    assert((Val % 2) != 0 && "Not an odd number!");
+  }
+  static bool classof(const Number *Num) { return (Num->getVal() % 2) != 0; }
+};
+
+
+
+class DynCastIterTest : public testing::Test {
+protected:
+  std::array<Number *, 10> Nums;
+
+  void SetUp() override {
+    for (std::size_t i = 1; i <= Nums.size(); ++i) {
+      Nums[i - 1] = (i % 2 == 0)
+                        ? static_cast<Number *>(new EvenNumber(i))
+                        : static_cast<Number *>(new OddNumber(i));
+    }
+  }
+
+  void TearDown() override {
+    for (auto *N : Nums)
+      delete N;
+  }
+};
+
+TEST_F(DynCastIterTest, Simple) {
+  auto It = make_dyn_cast_iterator<OddNumber>(Nums.begin(), Nums.end());
+  auto End = make_dyn_cast_iterator<OddNumber>(Nums.end(), Nums.end());
+
+  EXPECT_NE(It, End);
+  ASSERT_EQ((*It)->getVal(), 1u);
+
+  ++It;
+  EXPECT_NE(It, End);
+  ASSERT_EQ((*It)->getVal(), 3u);
+
+  ++It;
+  EXPECT_NE(It, End);
+  ASSERT_EQ((*It)->getVal(), 5u);
+
+  ++It;
+  EXPECT_NE(It, End);
+  ASSERT_EQ((*It)->getVal(), 7u);
+
+  ++It;
+  EXPECT_NE(It, End);
+  ASSERT_EQ((*It)->getVal(), 9u);
+
+  ++It;
+  ASSERT_EQ(It, End);
+}
+
+TEST_F(DynCastIterTest, Range) {
+  for (EvenNumber *N : make_dyn_cast_range<EvenNumber>(Nums))
+    (void)N;
+}
+
+} // end anonymous namespace