Index: include/llvm/ADT/STLExtras.h
===================================================================
--- include/llvm/ADT/STLExtras.h
+++ include/llvm/ADT/STLExtras.h
@@ -26,6 +26,7 @@
 #include <memory>
 #include <utility> // for std::pair
 
+#include "llvm/ADT/iterator.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Compiler.h"
 
@@ -235,6 +236,78 @@
                     llvm::make_reverse_iterator(std::begin(C)));
 }
 
+/// \brief An iterator adaptor that filters the elements of given inner
+/// iterators.
+///
+/// Predicate should take a parameter such that predicate(*iter) returns a bool,
+/// where iter is a WrappedIteratorT object. If the predicate returns true, the
+/// element is kept.
+///
+/// Currently it only supports operator++ but not operator--, so it's an input
+/// iterator if the underlying type is input iterator; otherwise it's a forward
+/// iterator.
+///
+/// \code
+///   const auto IsOdd = [](int a) { return a % 2 == 1; };
+///   filter_iterator<int *, decltype(IsOdd)> Begin(..., IsOdd);
+/// \endcode
+template <typename WrappedIteratorT, typename Predicate>
+class filter_iterator
+    : public iterator_adaptor_base<
+          filter_iterator<WrappedIteratorT, Predicate>, WrappedIteratorT,
+          typename std::conditional<
+              std::is_same<std::input_iterator_tag,
+                           typename std::iterator_traits<
+                               WrappedIteratorT>::iterator_category>::value,
+              std::input_iterator_tag, std::forward_iterator_tag>::type,
+          typename std::iterator_traits<WrappedIteratorT>::value_type,
+          typename std::iterator_traits<WrappedIteratorT>::difference_type,
+          typename std::iterator_traits<WrappedIteratorT>::pointer,
+          typename std::iterator_traits<WrappedIteratorT>::reference> {
+  using BaseT = iterator_adaptor_base<
+      filter_iterator<WrappedIteratorT, Predicate>, WrappedIteratorT,
+      typename std::conditional<
+          std::is_same<std::input_iterator_tag,
+                       typename std::iterator_traits<
+                           WrappedIteratorT>::iterator_category>::value,
+          std::input_iterator_tag, std::forward_iterator_tag>::type,
+      typename std::iterator_traits<WrappedIteratorT>::value_type,
+      typename std::iterator_traits<WrappedIteratorT>::difference_type,
+      typename std::iterator_traits<WrappedIteratorT>::pointer,
+      typename std::iterator_traits<WrappedIteratorT>::reference>;
+
+  WrappedIteratorT End;
+  Predicate Pred;
+
+  void findNextValid() {
+    while (this->I != End && !Pred(*this->I))
+      BaseT::operator++();
+  }
+
+public:
+  filter_iterator(WrappedIteratorT Begin, WrappedIteratorT End, Predicate Pred)
+      : BaseT(Begin), End(End), Pred(Pred) {
+    findNextValid();
+  }
+
+  using BaseT::operator++;
+
+  filter_iterator &operator++() {
+    BaseT::operator++();
+    findNextValid();
+    return *this;
+  }
+};
+
+template <typename WrappedIteratorT, typename Predicate>
+iterator_range<filter_iterator<WrappedIteratorT, Predicate>>
+make_filter_range(iterator_range<WrappedIteratorT> Range,
+                  const Predicate &Pred) {
+  using IterT = filter_iterator<WrappedIteratorT, Predicate>;
+  return make_range(IterT(Range.begin(), Range.end(), Pred),
+                    IterT(Range.end(), Range.end(), Pred));
+}
+
 //===----------------------------------------------------------------------===//
 //     Extra additions to <utility>
 //===----------------------------------------------------------------------===//
Index: unittests/Support/IteratorTest.cpp
===================================================================
--- unittests/Support/IteratorTest.cpp
+++ unittests/Support/IteratorTest.cpp
@@ -98,4 +98,13 @@
   EXPECT_EQ(End, I);
 }
 
+TEST(FilterIteratorTest, Basic) {
+  auto IsOdd = [](int a) { return a % 2 == 1; };
+  int a[] = {0, 1, 2, 3, 4, 5, 6};
+  const auto Range = make_filter_range(make_range(a, a + 7), IsOdd);
+  ASSERT_EQ(3, std::distance(Range.begin(), Range.end()));
+  SmallVector<int, 3> Actual(Range.begin(), Range.end());
+  EXPECT_EQ((SmallVector<int, 3>{1, 3, 5}), Actual);
+}
+
 } // anonymous namespace