diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -263,6 +263,12 @@
   return adl_begin(RangeOrContainer) == adl_end(RangeOrContainer);
 }
 
+/// Returns true of the given range only contains a single element.
+template <typename ContainerTy> bool hasSingleElement(ContainerTy &&c) {
+  auto it = std::begin(c), e = std::end(c);
+  return it != e && std::next(it) == e;
+}
+
 /// Return a range covering \p RangeOrContainer with the first N elements
 /// excluded.
 template <typename T> auto drop_begin(T &&RangeOrContainer, size_t N) {
@@ -1017,6 +1023,213 @@
       std::forward<RangeTs>(Ranges)...);
 }
 
+/// A utility class used to implement an iterator that contains some base object
+/// and an index. The iterator moves the index but keeps the base constant.
+template <typename DerivedT, typename BaseT, typename T,
+          typename PointerT = T *, typename ReferenceT = T &>
+class indexed_accessor_iterator
+    : public llvm::iterator_facade_base<DerivedT,
+                                        std::random_access_iterator_tag, T,
+                                        std::ptrdiff_t, PointerT, ReferenceT> {
+public:
+  ptrdiff_t operator-(const indexed_accessor_iterator &rhs) const {
+    assert(base == rhs.base && "incompatible iterators");
+    return index - rhs.index;
+  }
+  bool operator==(const indexed_accessor_iterator &rhs) const {
+    return base == rhs.base && index == rhs.index;
+  }
+  bool operator<(const indexed_accessor_iterator &rhs) const {
+    assert(base == rhs.base && "incompatible iterators");
+    return index < rhs.index;
+  }
+
+  DerivedT &operator+=(ptrdiff_t offset) {
+    this->index += offset;
+    return static_cast<DerivedT &>(*this);
+  }
+  DerivedT &operator-=(ptrdiff_t offset) {
+    this->index -= offset;
+    return static_cast<DerivedT &>(*this);
+  }
+
+  /// Returns the current index of the iterator.
+  ptrdiff_t getIndex() const { return index; }
+
+  /// Returns the current base of the iterator.
+  const BaseT &getBase() const { return base; }
+
+protected:
+  indexed_accessor_iterator(BaseT base, ptrdiff_t index)
+      : base(base), index(index) {}
+  BaseT base;
+  ptrdiff_t index;
+};
+
+namespace detail {
+/// The class represents the base of a range of indexed_accessor_iterators. It
+/// provides support for many different range functionalities, e.g.
+/// drop_front/slice/etc.. Derived range classes must implement the following
+/// static methods:
+///   * ReferenceT dereference_iterator(const BaseT &base, ptrdiff_t index)
+///     - Dereference an iterator pointing to the base object at the given
+///       index.
+///   * BaseT offset_base(const BaseT &base, ptrdiff_t index)
+///     - Return a new base that is offset from the provide base by 'index'
+///       elements.
+template <typename DerivedT, typename BaseT, typename T,
+          typename PointerT = T *, typename ReferenceT = T &>
+class indexed_accessor_range_base {
+public:
+  using RangeBaseT =
+      indexed_accessor_range_base<DerivedT, BaseT, T, PointerT, ReferenceT>;
+
+  /// An iterator element of this range.
+  class iterator : public indexed_accessor_iterator<iterator, BaseT, T,
+                                                    PointerT, ReferenceT> {
+  public:
+    // Index into this iterator, invoking a static method on the derived type.
+    ReferenceT operator*() const {
+      return DerivedT::dereference_iterator(this->getBase(), this->getIndex());
+    }
+
+  private:
+    iterator(BaseT owner, ptrdiff_t curIndex)
+        : indexed_accessor_iterator<iterator, BaseT, T, PointerT, ReferenceT>(
+              owner, curIndex) {}
+
+    /// Allow access to the constructor.
+    friend indexed_accessor_range_base<DerivedT, BaseT, T, PointerT,
+                                       ReferenceT>;
+  };
+
+  indexed_accessor_range_base(iterator begin, iterator end)
+      : base(DerivedT::offset_base(begin.getBase(), begin.getIndex())),
+        count(end.getIndex() - begin.getIndex()) {}
+  indexed_accessor_range_base(const iterator_range<iterator> &range)
+      : indexed_accessor_range_base(range.begin(), range.end()) {}
+  indexed_accessor_range_base(BaseT base, ptrdiff_t count)
+      : base(base), count(count) {}
+
+  iterator begin() const { return iterator(base, 0); }
+  iterator end() const { return iterator(base, count); }
+  ReferenceT operator[](unsigned index) const {
+    assert(index < size() && "invalid index for value range");
+    return DerivedT::dereference_iterator(base, index);
+  }
+
+  /// Compare this range with another.
+  template <typename OtherT> bool operator==(const OtherT &other) {
+    return size() == std::distance(other.begin(), other.end()) &&
+           std::equal(begin(), end(), other.begin());
+  }
+
+  /// Return the size of this range.
+  size_t size() const { return count; }
+
+  /// Return if the range is empty.
+  bool empty() const { return size() == 0; }
+
+  /// Drop the first N elements, and keep M elements.
+  DerivedT slice(size_t n, size_t m) const {
+    assert(n + m <= size() && "invalid size specifiers");
+    return DerivedT(DerivedT::offset_base(base, n), m);
+  }
+
+  /// Drop the first n elements.
+  DerivedT drop_front(size_t n = 1) const {
+    assert(size() >= n && "Dropping more elements than exist");
+    return slice(n, size() - n);
+  }
+  /// Drop the last n elements.
+  DerivedT drop_back(size_t n = 1) const {
+    assert(size() >= n && "Dropping more elements than exist");
+    return DerivedT(base, size() - n);
+  }
+
+  /// Take the first n elements.
+  DerivedT take_front(size_t n = 1) const {
+    return n < size() ? drop_back(size() - n)
+                      : static_cast<const DerivedT &>(*this);
+  }
+
+  /// Take the last n elements.
+  DerivedT take_back(size_t n = 1) const {
+    return n < size() ? drop_front(size() - n)
+                      : static_cast<const DerivedT &>(*this);
+  }
+
+  /// Allow conversion to any type accepting an iterator_range.
+  template <typename RangeT, typename = std::enable_if_t<std::is_constructible<
+                                 RangeT, iterator_range<iterator>>::value>>
+  operator RangeT() const {
+    return RangeT(iterator_range<iterator>(*this));
+  }
+
+protected:
+  indexed_accessor_range_base(const indexed_accessor_range_base &) = default;
+  indexed_accessor_range_base(indexed_accessor_range_base &&) = default;
+  indexed_accessor_range_base &
+  operator=(const indexed_accessor_range_base &) = default;
+
+  /// The base that owns the provided range of values.
+  BaseT base;
+  /// The size from the owning range.
+  ptrdiff_t count;
+};
+} // end namespace detail
+
+/// This class provides an implementation of a range of
+/// indexed_accessor_iterators where the base is not indexable. Ranges with
+/// bases that are offsetable should derive from indexed_accessor_range_base
+/// instead. Derived range classes are expected to implement the following
+/// static method:
+///   * ReferenceT dereference(const BaseT &base, ptrdiff_t index)
+///     - Dereference an iterator pointing to a parent base at the given index.
+template <typename DerivedT, typename BaseT, typename T,
+          typename PointerT = T *, typename ReferenceT = T &>
+class indexed_accessor_range
+    : public detail::indexed_accessor_range_base<
+          DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT, ReferenceT> {
+public:
+  indexed_accessor_range(BaseT base, ptrdiff_t startIndex, ptrdiff_t count)
+      : detail::indexed_accessor_range_base<
+            DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT, ReferenceT>(
+            std::make_pair(base, startIndex), count) {}
+  using detail::indexed_accessor_range_base<
+      DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT,
+      ReferenceT>::indexed_accessor_range_base;
+
+  /// Returns the current base of the range.
+  const BaseT &getBase() const { return this->base.first; }
+
+  /// Returns the current start index of the range.
+  ptrdiff_t getStartIndex() const { return this->base.second; }
+
+  /// See `detail::indexed_accessor_range_base` for details.
+  static std::pair<BaseT, ptrdiff_t>
+  offset_base(const std::pair<BaseT, ptrdiff_t> &base, ptrdiff_t index) {
+    // We encode the internal base as a pair of the derived base and a start
+    // index into the derived base.
+    return std::make_pair(base.first, base.second + index);
+  }
+  /// See `detail::indexed_accessor_range_base` for details.
+  static ReferenceT
+  dereference_iterator(const std::pair<BaseT, ptrdiff_t> &base,
+                       ptrdiff_t index) {
+    return DerivedT::dereference(base.first, base.second + index);
+  }
+};
+
+/// Given a container of pairs, return a range over the second elements.
+template <typename ContainerTy> auto make_second_range(ContainerTy &&c) {
+  return llvm::map_range(
+      std::forward<ContainerTy>(c),
+      [](decltype((*std::begin(c))) elt) -> decltype((elt.second)) {
+        return elt.second;
+      });
+}
+
 //===----------------------------------------------------------------------===//
 //     Extra additions to <utility>
 //===----------------------------------------------------------------------===//
diff --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -40,6 +40,7 @@
   FormatVariadicTest.cpp
   GlobPatternTest.cpp
   Host.cpp
+  IndexedAccessorTest.cpp
   ItaniumManglingCanonicalizerTest.cpp
   JSONTest.cpp
   KnownBitsTest.cpp
diff --git a/mlir/unittests/Support/IndexedAccessorTest.cpp b/llvm/unittests/Support/IndexedAccessorTest.cpp
rename from mlir/unittests/Support/IndexedAccessorTest.cpp
rename to llvm/unittests/Support/IndexedAccessorTest.cpp
--- a/mlir/unittests/Support/IndexedAccessorTest.cpp
+++ b/llvm/unittests/Support/IndexedAccessorTest.cpp
@@ -6,12 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "mlir/Support/STLExtras.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "gmock/gmock.h"
 
-using namespace mlir;
-using namespace mlir::detail;
+using namespace llvm;
+using namespace llvm::detail;
 
 namespace {
 /// Simple indexed accessor range that wraps an array.
@@ -24,7 +24,7 @@
   using indexed_accessor_range<ArrayIndexedAccessorRange<T>, T *,
                                T>::indexed_accessor_range;
 
-  /// See `indexed_accessor_range` for details.
+  /// See `llvm::indexed_accessor_range` for details.
   static T &dereference(T *data, ptrdiff_t index) { return data[index]; }
 };
 } // end anonymous namespace
diff --git a/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h b/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h
--- a/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h
+++ b/mlir/include/mlir/Dialect/SPIRV/SPIRVTypes.h
@@ -290,16 +290,16 @@
 
   /// Range class for element types.
   class ElementTypeRange
-      : public ::mlir::detail::indexed_accessor_range_base<
+      : public ::llvm::detail::indexed_accessor_range_base<
             ElementTypeRange, const Type *, Type, Type, Type> {
   private:
     using RangeBaseT::RangeBaseT;
 
-    /// See `mlir::detail::indexed_accessor_range_base` for details.
+    /// See `llvm::detail::indexed_accessor_range_base` for details.
     static const Type *offset_base(const Type *object, ptrdiff_t index) {
       return object + index;
     }
-    /// See `mlir::detail::indexed_accessor_range_base` for details.
+    /// See `llvm::detail::indexed_accessor_range_base` for details.
     static Type dereference_iterator(const Type *object, ptrdiff_t index) {
       return object[index];
     }
diff --git a/mlir/include/mlir/IR/Attributes.h b/mlir/include/mlir/IR/Attributes.h
--- a/mlir/include/mlir/IR/Attributes.h
+++ b/mlir/include/mlir/IR/Attributes.h
@@ -648,13 +648,14 @@
 template <typename ConcreteT, typename T, typename PointerT = T *,
           typename ReferenceT = T &>
 class DenseElementIndexedIteratorImpl
-    : public indexed_accessor_iterator<ConcreteT, DenseIterPtrAndSplat, T,
-                                       PointerT, ReferenceT> {
+    : public llvm::indexed_accessor_iterator<ConcreteT, DenseIterPtrAndSplat, T,
+                                             PointerT, ReferenceT> {
 protected:
   DenseElementIndexedIteratorImpl(const char *data, bool isSplat,
                                   size_t dataIndex)
-      : indexed_accessor_iterator<ConcreteT, DenseIterPtrAndSplat, T, PointerT,
-                                  ReferenceT>({data, isSplat}, dataIndex) {}
+      : llvm::indexed_accessor_iterator<ConcreteT, DenseIterPtrAndSplat, T,
+                                        PointerT, ReferenceT>({data, isSplat},
+                                                              dataIndex) {}
 
   /// Return the current index for this iterator, adjusted for the case of a
   /// splat.
@@ -746,8 +747,9 @@
   /// A utility iterator that allows walking over the internal Attribute values
   /// of a DenseElementsAttr.
   class AttributeElementIterator
-      : public indexed_accessor_iterator<AttributeElementIterator, const void *,
-                                         Attribute, Attribute, Attribute> {
+      : public llvm::indexed_accessor_iterator<AttributeElementIterator,
+                                               const void *, Attribute,
+                                               Attribute, Attribute> {
   public:
     /// Accesses the Attribute value at this iterator position.
     Attribute operator*() const;
diff --git a/mlir/include/mlir/IR/BlockSupport.h b/mlir/include/mlir/IR/BlockSupport.h
--- a/mlir/include/mlir/IR/BlockSupport.h
+++ b/mlir/include/mlir/IR/BlockSupport.h
@@ -54,19 +54,19 @@
 
 /// This class implements the successor iterators for Block.
 class SuccessorRange final
-    : public detail::indexed_accessor_range_base<SuccessorRange, BlockOperand *,
-                                                 Block *, Block *, Block *> {
+    : public llvm::detail::indexed_accessor_range_base<
+          SuccessorRange, BlockOperand *, Block *, Block *, Block *> {
 public:
   using RangeBaseT::RangeBaseT;
   SuccessorRange(Block *block);
   SuccessorRange(Operation *term);
 
 private:
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static BlockOperand *offset_base(BlockOperand *object, ptrdiff_t index) {
     return object + index;
   }
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static Block *dereference_iterator(BlockOperand *object, ptrdiff_t index) {
     return object[index].get();
   }
diff --git a/mlir/include/mlir/IR/OpImplementation.h b/mlir/include/mlir/IR/OpImplementation.h
--- a/mlir/include/mlir/IR/OpImplementation.h
+++ b/mlir/include/mlir/IR/OpImplementation.h
@@ -113,7 +113,7 @@
   void printArrowTypeList(TypeRange &&types) {
     auto &os = getStream() << " -> ";
 
-    bool wrapped = !has_single_element(types) ||
+    bool wrapped = !llvm::hasSingleElement(types) ||
                    (*types.begin()).template isa<FunctionType>();
     if (wrapped)
       os << '(';
diff --git a/mlir/include/mlir/IR/OperationSupport.h b/mlir/include/mlir/IR/OperationSupport.h
--- a/mlir/include/mlir/IR/OperationSupport.h
+++ b/mlir/include/mlir/IR/OperationSupport.h
@@ -558,7 +558,7 @@
 /// suitable for a more derived type (e.g. ArrayRef) or a template range
 /// parameter.
 class TypeRange
-    : public detail::indexed_accessor_range_base<
+    : public llvm::detail::indexed_accessor_range_base<
           TypeRange,
           llvm::PointerUnion<const Value *, const Type *, OpOperand *>, Type,
           Type, Type> {
@@ -589,9 +589,9 @@
   /// * A pointer to the first element of an array of operands.
   using OwnerT = llvm::PointerUnion<const Value *, const Type *, OpOperand *>;
 
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static OwnerT offset_base(OwnerT object, ptrdiff_t index);
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static Type dereference_iterator(OwnerT object, ptrdiff_t index);
 
   /// Allow access to `offset_base` and `dereference_iterator`.
@@ -640,9 +640,8 @@
 // OperandRange
 
 /// This class implements the operand iterators for the Operation class.
-class OperandRange final
-    : public detail::indexed_accessor_range_base<OperandRange, OpOperand *,
-                                                 Value, Value, Value> {
+class OperandRange final : public llvm::detail::indexed_accessor_range_base<
+                               OperandRange, OpOperand *, Value, Value, Value> {
 public:
   using RangeBaseT::RangeBaseT;
   OperandRange(Operation *op);
@@ -658,11 +657,11 @@
   unsigned getBeginOperandIndex() const;
 
 private:
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static OpOperand *offset_base(OpOperand *object, ptrdiff_t index) {
     return object + index;
   }
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static Value dereference_iterator(OpOperand *object, ptrdiff_t index) {
     return object[index].get();
   }
@@ -676,8 +675,8 @@
 
 /// This class implements the result iterators for the Operation class.
 class ResultRange final
-    : public indexed_accessor_range<ResultRange, Operation *, OpResult,
-                                    OpResult, OpResult> {
+    : public llvm::indexed_accessor_range<ResultRange, Operation *, OpResult,
+                                          OpResult, OpResult> {
 public:
   using indexed_accessor_range<ResultRange, Operation *, OpResult, OpResult,
                                OpResult>::indexed_accessor_range;
@@ -690,12 +689,12 @@
   auto getType() const { return getTypes(); }
 
 private:
-  /// See `indexed_accessor_range` for details.
+  /// See `llvm::indexed_accessor_range` for details.
   static OpResult dereference(Operation *op, ptrdiff_t index);
 
   /// Allow access to `dereference_iterator`.
-  friend indexed_accessor_range<ResultRange, Operation *, OpResult, OpResult,
-                                OpResult>;
+  friend llvm::indexed_accessor_range<ResultRange, Operation *, OpResult,
+                                      OpResult, OpResult>;
 };
 
 //===----------------------------------------------------------------------===//
@@ -730,7 +729,7 @@
 /// suitable for a more derived type (e.g. ArrayRef) or a template range
 /// parameter.
 class ValueRange final
-    : public detail::indexed_accessor_range_base<
+    : public llvm::detail::indexed_accessor_range_base<
           ValueRange, detail::ValueRangeOwner, Value, Value, Value> {
 public:
   using RangeBaseT::RangeBaseT;
@@ -762,9 +761,9 @@
 private:
   using OwnerT = detail::ValueRangeOwner;
 
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static OwnerT offset_base(const OwnerT &owner, ptrdiff_t index);
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static Value dereference_iterator(const OwnerT &owner, ptrdiff_t index);
 
   /// Allow access to `offset_base` and `dereference_iterator`.
diff --git a/mlir/include/mlir/IR/Region.h b/mlir/include/mlir/IR/Region.h
--- a/mlir/include/mlir/IR/Region.h
+++ b/mlir/include/mlir/IR/Region.h
@@ -157,7 +157,7 @@
 /// suitable for a more derived type (e.g. ArrayRef) or a template range
 /// parameter.
 class RegionRange
-    : public detail::indexed_accessor_range_base<
+    : public llvm::detail::indexed_accessor_range_base<
           RegionRange, PointerUnion<Region *, const std::unique_ptr<Region> *>,
           Region *, Region *, Region *> {
   /// The type representing the owner of this range. This is either a list of
@@ -178,9 +178,9 @@
   RegionRange(ArrayRef<std::unique_ptr<Region>> regions);
 
 private:
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static OwnerT offset_base(const OwnerT &owner, ptrdiff_t index);
-  /// See `detail::indexed_accessor_range_base` for details.
+  /// See `llvm::detail::indexed_accessor_range_base` for details.
   static Region *dereference_iterator(const OwnerT &owner, ptrdiff_t index);
 
   /// Allow access to `offset_base` and `dereference_iterator`.
diff --git a/mlir/include/mlir/IR/UseDefLists.h b/mlir/include/mlir/IR/UseDefLists.h
--- a/mlir/include/mlir/IR/UseDefLists.h
+++ b/mlir/include/mlir/IR/UseDefLists.h
@@ -148,7 +148,7 @@
     return {use_begin(value), use_end(value)};
   }
   bool hasOneUse(ValueType value) const {
-    return mlir::has_single_element(getUses(value));
+    return llvm::hasSingleElement(getUses(value));
   }
   bool use_empty(ValueType value) const {
     return use_begin(value) == use_end(value);
diff --git a/mlir/include/mlir/Support/STLExtras.h b/mlir/include/mlir/Support/STLExtras.h
--- a/mlir/include/mlir/Support/STLExtras.h
+++ b/mlir/include/mlir/Support/STLExtras.h
@@ -88,243 +88,6 @@
   interleaveComma(c, os, [&](const T &a) { os << a; });
 }
 
-//===----------------------------------------------------------------------===//
-//     Extra additions to <iterator>
-//===----------------------------------------------------------------------===//
-
-/// A utility class used to implement an iterator that contains some base object
-/// and an index. The iterator moves the index but keeps the base constant.
-template <typename DerivedT, typename BaseT, typename T,
-          typename PointerT = T *, typename ReferenceT = T &>
-class indexed_accessor_iterator
-    : public llvm::iterator_facade_base<DerivedT,
-                                        std::random_access_iterator_tag, T,
-                                        std::ptrdiff_t, PointerT, ReferenceT> {
-public:
-  ptrdiff_t operator-(const indexed_accessor_iterator &rhs) const {
-    assert(base == rhs.base && "incompatible iterators");
-    return index - rhs.index;
-  }
-  bool operator==(const indexed_accessor_iterator &rhs) const {
-    return base == rhs.base && index == rhs.index;
-  }
-  bool operator<(const indexed_accessor_iterator &rhs) const {
-    assert(base == rhs.base && "incompatible iterators");
-    return index < rhs.index;
-  }
-
-  DerivedT &operator+=(ptrdiff_t offset) {
-    this->index += offset;
-    return static_cast<DerivedT &>(*this);
-  }
-  DerivedT &operator-=(ptrdiff_t offset) {
-    this->index -= offset;
-    return static_cast<DerivedT &>(*this);
-  }
-
-  /// Returns the current index of the iterator.
-  ptrdiff_t getIndex() const { return index; }
-
-  /// Returns the current base of the iterator.
-  const BaseT &getBase() const { return base; }
-
-protected:
-  indexed_accessor_iterator(BaseT base, ptrdiff_t index)
-      : base(base), index(index) {}
-  BaseT base;
-  ptrdiff_t index;
-};
-
-namespace detail {
-/// The class represents the base of a range of indexed_accessor_iterators. It
-/// provides support for many different range functionalities, e.g.
-/// drop_front/slice/etc.. Derived range classes must implement the following
-/// static methods:
-///   * ReferenceT dereference_iterator(const BaseT &base, ptrdiff_t index)
-///     - Dereference an iterator pointing to the base object at the given
-///       index.
-///   * BaseT offset_base(const BaseT &base, ptrdiff_t index)
-///     - Return a new base that is offset from the provide base by 'index'
-///       elements.
-template <typename DerivedT, typename BaseT, typename T,
-          typename PointerT = T *, typename ReferenceT = T &>
-class indexed_accessor_range_base {
-public:
-  using RangeBaseT =
-      indexed_accessor_range_base<DerivedT, BaseT, T, PointerT, ReferenceT>;
-
-  /// An iterator element of this range.
-  class iterator : public indexed_accessor_iterator<iterator, BaseT, T,
-                                                    PointerT, ReferenceT> {
-  public:
-    // Index into this iterator, invoking a static method on the derived type.
-    ReferenceT operator*() const {
-      return DerivedT::dereference_iterator(this->getBase(), this->getIndex());
-    }
-
-  private:
-    iterator(BaseT owner, ptrdiff_t curIndex)
-        : indexed_accessor_iterator<iterator, BaseT, T, PointerT, ReferenceT>(
-              owner, curIndex) {}
-
-    /// Allow access to the constructor.
-    friend indexed_accessor_range_base<DerivedT, BaseT, T, PointerT,
-                                       ReferenceT>;
-  };
-
-  indexed_accessor_range_base(iterator begin, iterator end)
-      : base(DerivedT::offset_base(begin.getBase(), begin.getIndex())),
-        count(end.getIndex() - begin.getIndex()) {}
-  indexed_accessor_range_base(const iterator_range<iterator> &range)
-      : indexed_accessor_range_base(range.begin(), range.end()) {}
-  indexed_accessor_range_base(BaseT base, ptrdiff_t count)
-      : base(base), count(count) {}
-
-  iterator begin() const { return iterator(base, 0); }
-  iterator end() const { return iterator(base, count); }
-  ReferenceT operator[](unsigned index) const {
-    assert(index < size() && "invalid index for value range");
-    return DerivedT::dereference_iterator(base, index);
-  }
-
-  /// Compare this range with another.
-  template <typename OtherT> bool operator==(const OtherT &other) {
-    return size() == llvm::size(other) &&
-           std::equal(begin(), end(), other.begin());
-  }
-
-  /// Return the size of this range.
-  size_t size() const { return count; }
-
-  /// Return if the range is empty.
-  bool empty() const { return size() == 0; }
-
-  /// Drop the first N elements, and keep M elements.
-  DerivedT slice(size_t n, size_t m) const {
-    assert(n + m <= size() && "invalid size specifiers");
-    return DerivedT(DerivedT::offset_base(base, n), m);
-  }
-
-  /// Drop the first n elements.
-  DerivedT drop_front(size_t n = 1) const {
-    assert(size() >= n && "Dropping more elements than exist");
-    return slice(n, size() - n);
-  }
-  /// Drop the last n elements.
-  DerivedT drop_back(size_t n = 1) const {
-    assert(size() >= n && "Dropping more elements than exist");
-    return DerivedT(base, size() - n);
-  }
-
-  /// Take the first n elements.
-  DerivedT take_front(size_t n = 1) const {
-    return n < size() ? drop_back(size() - n)
-                      : static_cast<const DerivedT &>(*this);
-  }
-
-  /// Take the last n elements.
-  DerivedT take_back(size_t n = 1) const {
-    return n < size() ? drop_front(size() - n)
-                      : static_cast<const DerivedT &>(*this);
-  }
-
-  /// Allow conversion to SmallVector if necessary.
-  /// TODO(riverriddle) Remove this when SmallVector accepts different range
-  /// types in its constructor.
-  template <typename SVT, unsigned N> operator SmallVector<SVT, N>() const {
-    return {begin(), end()};
-  }
-
-protected:
-  indexed_accessor_range_base(const indexed_accessor_range_base &) = default;
-  indexed_accessor_range_base(indexed_accessor_range_base &&) = default;
-  indexed_accessor_range_base &
-  operator=(const indexed_accessor_range_base &) = default;
-
-  /// The base that owns the provided range of values.
-  BaseT base;
-  /// The size from the owning range.
-  ptrdiff_t count;
-};
-} // end namespace detail
-
-/// This class provides an implementation of a range of
-/// indexed_accessor_iterators where the base is not indexable. Ranges with
-/// bases that are offsetable should derive from indexed_accessor_range_base
-/// instead. Derived range classes are expected to implement the following
-/// static method:
-///   * ReferenceT dereference(const BaseT &base, ptrdiff_t index)
-///     - Dereference an iterator pointing to a parent base at the given index.
-template <typename DerivedT, typename BaseT, typename T,
-          typename PointerT = T *, typename ReferenceT = T &>
-class indexed_accessor_range
-    : public detail::indexed_accessor_range_base<
-          DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT, ReferenceT> {
-public:
-  indexed_accessor_range(BaseT base, ptrdiff_t startIndex, ptrdiff_t count)
-      : detail::indexed_accessor_range_base<
-            DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT, ReferenceT>(
-            std::make_pair(base, startIndex), count) {}
-  using detail::indexed_accessor_range_base<
-      DerivedT, std::pair<BaseT, ptrdiff_t>, T, PointerT,
-      ReferenceT>::indexed_accessor_range_base;
-
-  /// Returns the current base of the range.
-  const BaseT &getBase() const { return this->base.first; }
-
-  /// Returns the current start index of the range.
-  ptrdiff_t getStartIndex() const { return this->base.second; }
-
-  /// See `detail::indexed_accessor_range_base` for details.
-  static std::pair<BaseT, ptrdiff_t>
-  offset_base(const std::pair<BaseT, ptrdiff_t> &base, ptrdiff_t index) {
-    // We encode the internal base as a pair of the derived base and a start
-    // index into the derived base.
-    return std::make_pair(base.first, base.second + index);
-  }
-  /// See `detail::indexed_accessor_range_base` for details.
-  static ReferenceT
-  dereference_iterator(const std::pair<BaseT, ptrdiff_t> &base,
-                       ptrdiff_t index) {
-    return DerivedT::dereference(base.first, base.second + index);
-  }
-};
-
-/// Given a container of pairs, return a range over the second elements.
-template <typename ContainerTy> auto make_second_range(ContainerTy &&c) {
-  return llvm::map_range(
-      std::forward<ContainerTy>(c),
-      [](decltype((*std::begin(c))) elt) -> decltype((elt.second)) {
-        return elt.second;
-      });
-}
-
-/// A range class that repeats a specific value for a set number of times.
-template <typename T>
-class RepeatRange
-    : public detail::indexed_accessor_range_base<RepeatRange<T>, T, const T> {
-public:
-  using detail::indexed_accessor_range_base<
-      RepeatRange<T>, T, const T>::indexed_accessor_range_base;
-
-  /// Given that we are repeating a specific value, we can simply return that
-  /// value when offsetting the base or dereferencing the iterator.
-  static T offset_base(const T &val, ptrdiff_t) { return val; }
-  static const T &dereference_iterator(const T &val, ptrdiff_t) { return val; }
-};
-
-/// Make a range that repeats the given value 'n' times.
-template <typename ValueTy>
-RepeatRange<ValueTy> make_repeated_range(const ValueTy &value, size_t n) {
-  return RepeatRange<ValueTy>(value, n);
-}
-
-/// Returns true of the given range only contains a single element.
-template <typename ContainerTy> bool has_single_element(ContainerTy &&c) {
-  auto it = std::begin(c), e = std::end(c);
-  return it != e && std::next(it) == e;
-}
-
 } // end namespace mlir
 
 #endif // MLIR_SUPPORT_STLEXTRAS_H
diff --git a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
--- a/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
+++ b/mlir/lib/Dialect/Affine/IR/AffineOps.cpp
@@ -1407,7 +1407,7 @@
   LogicalResult matchAndRewrite(AffineForOp forOp,
                                 PatternRewriter &rewriter) const override {
     // Check that the body only contains a terminator.
-    if (!has_single_element(*forOp.getBody()))
+    if (!llvm::hasSingleElement(*forOp.getBody()))
       return failure();
     rewriter.eraseOp(forOp);
     return success();
@@ -1576,7 +1576,8 @@
 
   LogicalResult matchAndRewrite(AffineIfOp ifOp,
                                 PatternRewriter &rewriter) const override {
-    if (ifOp.elseRegion().empty() || !has_single_element(*ifOp.getElseBlock()))
+    if (ifOp.elseRegion().empty() ||
+        !llvm::hasSingleElement(*ifOp.getElseBlock()))
       return failure();
 
     rewriter.startRootUpdate(ifOp);
diff --git a/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp b/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
--- a/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
+++ b/mlir/lib/Dialect/GPU/Transforms/MemoryPromotion.cpp
@@ -138,7 +138,7 @@
   (void)toType;
   assert(fromType.getShape() == toType.getShape());
   assert(fromType.getRank() != 0);
-  assert(has_single_element(region) &&
+  assert(llvm::hasSingleElement(region) &&
          "unstructured control flow not supported");
 
   OpBuilder builder(region.getContext());
diff --git a/mlir/lib/Dialect/Linalg/Utils/Utils.cpp b/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
--- a/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
+++ b/mlir/lib/Dialect/Linalg/Utils/Utils.cpp
@@ -31,7 +31,7 @@
 Optional<RegionMatcher::BinaryOpKind>
 RegionMatcher::matchAsScalarBinaryOp(GenericOp op) {
   auto &region = op.region();
-  if (!has_single_element(region))
+  if (!llvm::hasSingleElement(region))
     return llvm::None;
 
   Block &block = region.front();
@@ -41,7 +41,7 @@
     return llvm::None;
 
   auto &ops = block.getOperations();
-  if (!has_single_element(block.without_terminator()))
+  if (!llvm::hasSingleElement(block.without_terminator()))
     return llvm::None;
 
   using mlir::matchers::m_Val;
diff --git a/mlir/lib/Dialect/SPIRV/SPIRVOps.cpp b/mlir/lib/Dialect/SPIRV/SPIRVOps.cpp
--- a/mlir/lib/Dialect/SPIRV/SPIRVOps.cpp
+++ b/mlir/lib/Dialect/SPIRV/SPIRVOps.cpp
@@ -1956,7 +1956,7 @@
 /// given `dstBlock`.
 static inline bool hasOneBranchOpTo(Block &srcBlock, Block &dstBlock) {
   // Check that there is only one op in the `srcBlock`.
-  if (!has_single_element(srcBlock))
+  if (!llvm::hasSingleElement(srcBlock))
     return false;
 
   auto branchOp = dyn_cast<spirv::BranchOp>(srcBlock.back());
diff --git a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
--- a/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
+++ b/mlir/lib/Dialect/StandardOps/IR/Ops.cpp
@@ -499,7 +499,7 @@
     // Check that the successor block has a single predecessor.
     Block *succ = op.getDest();
     Block *opParent = op.getOperation()->getBlock();
-    if (succ == opParent || !has_single_element(succ->getPredecessors()))
+    if (succ == opParent || !llvm::hasSingleElement(succ->getPredecessors()))
       return failure();
 
     // Merge the successor into the current block and erase the branch.
diff --git a/mlir/lib/IR/Attributes.cpp b/mlir/lib/IR/Attributes.cpp
--- a/mlir/lib/IR/Attributes.cpp
+++ b/mlir/lib/IR/Attributes.cpp
@@ -554,8 +554,8 @@
 /// Constructs a new iterator.
 DenseElementsAttr::AttributeElementIterator::AttributeElementIterator(
     DenseElementsAttr attr, size_t index)
-    : indexed_accessor_iterator<AttributeElementIterator, const void *,
-                                Attribute, Attribute, Attribute>(
+    : llvm::indexed_accessor_iterator<AttributeElementIterator, const void *,
+                                      Attribute, Attribute, Attribute>(
           attr.getAsOpaquePointer(), index) {}
 
 /// Accesses the Attribute value at this iterator position.
diff --git a/mlir/lib/IR/Module.cpp b/mlir/lib/IR/Module.cpp
--- a/mlir/lib/IR/Module.cpp
+++ b/mlir/lib/IR/Module.cpp
@@ -73,7 +73,7 @@
   auto &bodyRegion = getOperation()->getRegion(0);
 
   // The body must contain a single basic block.
-  if (!has_single_element(bodyRegion))
+  if (!llvm::hasSingleElement(bodyRegion))
     return emitOpError("expected body region to have a single block");
 
   // Check that the body has no block arguments.
diff --git a/mlir/lib/IR/OperationSupport.cpp b/mlir/lib/IR/OperationSupport.cpp
--- a/mlir/lib/IR/OperationSupport.cpp
+++ b/mlir/lib/IR/OperationSupport.cpp
@@ -158,7 +158,7 @@
     this->base = owner.ptr.get<const Value *>();
 }
 
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 TypeRange::OwnerT TypeRange::offset_base(OwnerT object, ptrdiff_t index) {
   if (auto *value = object.dyn_cast<const Value *>())
     return {value + index};
@@ -166,7 +166,7 @@
     return {operand + index};
   return {object.dyn_cast<const Type *>() + index};
 }
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 Type TypeRange::dereference_iterator(OwnerT object, ptrdiff_t index) {
   if (auto *value = object.dyn_cast<const Value *>())
     return (value + index)->getType();
@@ -198,7 +198,7 @@
   return getBase()->getResultTypes();
 }
 
-/// See `indexed_accessor_range` for details.
+/// See `llvm::indexed_accessor_range` for details.
 OpResult ResultRange::dereference(Operation *op, ptrdiff_t index) {
   return op->getResult(index);
 }
@@ -215,7 +215,7 @@
           {values.getBase(), static_cast<unsigned>(values.getStartIndex())},
           values.size()) {}
 
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 ValueRange::OwnerT ValueRange::offset_base(const OwnerT &owner,
                                            ptrdiff_t index) {
   if (auto *value = owner.ptr.dyn_cast<const Value *>())
@@ -225,7 +225,7 @@
   Operation *operation = reinterpret_cast<Operation *>(owner.ptr.get<void *>());
   return {operation, owner.startIndex + static_cast<unsigned>(index)};
 }
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 Value ValueRange::dereference_iterator(const OwnerT &owner, ptrdiff_t index) {
   if (auto *value = owner.ptr.dyn_cast<const Value *>())
     return value[index];
diff --git a/mlir/lib/IR/Region.cpp b/mlir/lib/IR/Region.cpp
--- a/mlir/lib/IR/Region.cpp
+++ b/mlir/lib/IR/Region.cpp
@@ -214,14 +214,14 @@
 RegionRange::RegionRange(ArrayRef<std::unique_ptr<Region>> regions)
     : RegionRange(regions.data(), regions.size()) {}
 
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 RegionRange::OwnerT RegionRange::offset_base(const OwnerT &owner,
                                              ptrdiff_t index) {
   if (auto *operand = owner.dyn_cast<const std::unique_ptr<Region> *>())
     return operand + index;
   return &owner.get<Region *>()[index];
 }
-/// See `detail::indexed_accessor_range_base` for details.
+/// See `llvm::detail::indexed_accessor_range_base` for details.
 Region *RegionRange::dereference_iterator(const OwnerT &owner,
                                           ptrdiff_t index) {
   if (auto *operand = owner.dyn_cast<const std::unique_ptr<Region> *>())
diff --git a/mlir/lib/IR/SymbolTable.cpp b/mlir/lib/IR/SymbolTable.cpp
--- a/mlir/lib/IR/SymbolTable.cpp
+++ b/mlir/lib/IR/SymbolTable.cpp
@@ -79,7 +79,7 @@
          "expected operation to have SymbolTable trait");
   assert(symbolTableOp->getNumRegions() == 1 &&
          "expected operation to have a single region");
-  assert(has_single_element(symbolTableOp->getRegion(0)) &&
+  assert(llvm::hasSingleElement(symbolTableOp->getRegion(0)) &&
          "expected operation to have a single block");
 
   for (auto &op : symbolTableOp->getRegion(0).front()) {
@@ -290,7 +290,7 @@
   if (op->getNumRegions() != 1)
     return op->emitOpError()
            << "Operations with a 'SymbolTable' must have exactly one region";
-  if (!has_single_element(op->getRegion(0)))
+  if (!llvm::hasSingleElement(op->getRegion(0)))
     return op->emitOpError()
            << "Operations with a 'SymbolTable' must have exactly one block";
 
diff --git a/mlir/lib/Transforms/Utils/LoopUtils.cpp b/mlir/lib/Transforms/Utils/LoopUtils.cpp
--- a/mlir/lib/Transforms/Utils/LoopUtils.cpp
+++ b/mlir/lib/Transforms/Utils/LoopUtils.cpp
@@ -414,7 +414,7 @@
     return promoteIfSingleIteration(forOp);
 
   // Nothing in the loop body other than the terminator.
-  if (has_single_element(forOp.getBody()->getOperations()))
+  if (llvm::hasSingleElement(forOp.getBody()->getOperations()))
     return success();
 
   // Loops where the lower bound is a max expression isn't supported for
@@ -538,7 +538,7 @@
     return promoteIfSingleIteration(forOp);
 
   // Nothing in the loop body other than the terminator.
-  if (has_single_element(forOp.getBody()->getOperations()))
+  if (llvm::hasSingleElement(forOp.getBody()->getOperations()))
     return success();
 
   // Loops where both lower and upper bounds are multi-result maps won't be
diff --git a/mlir/unittests/CMakeLists.txt b/mlir/unittests/CMakeLists.txt
--- a/mlir/unittests/CMakeLists.txt
+++ b/mlir/unittests/CMakeLists.txt
@@ -10,5 +10,4 @@
 add_subdirectory(IR)
 add_subdirectory(Pass)
 add_subdirectory(SDBM)
-add_subdirectory(Support)
 add_subdirectory(TableGen)
diff --git a/mlir/unittests/Support/CMakeLists.txt b/mlir/unittests/Support/CMakeLists.txt
deleted file mode 100644
--- a/mlir/unittests/Support/CMakeLists.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-add_mlir_unittest(MLIRSupportTests
-  IndexedAccessorTest.cpp
-)
-
-target_link_libraries(MLIRSupportTests
-  PRIVATE MLIRSupport)