diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -240,6 +240,10 @@
     unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
                            unsigned MaxEditDistance = 0) const;
 
+    LLVM_NODISCARD unsigned
+    edit_distance_insensitive(StringRef Other, bool AllowReplacements = true,
+                              unsigned MaxEditDistance = 0) const;
+
     /// str - Get the contents as an std::string.
     LLVM_NODISCARD
     std::string str() const {
diff --git a/llvm/lib/Support/StringRef.cpp b/llvm/lib/Support/StringRef.cpp
--- a/llvm/lib/Support/StringRef.cpp
+++ b/llvm/lib/Support/StringRef.cpp
@@ -98,6 +98,52 @@
       AllowReplacements, MaxEditDistance);
 }
 
+unsigned llvm::StringRef::edit_distance_insensitive(
+    StringRef Other, bool AllowReplacements, unsigned MaxEditDistance) const {
+  size_t Size = size();
+  size_t OtherSize = Other.size();
+  constexpr unsigned SmallBufferSize = 64;
+  unsigned SmallBuffer[SmallBufferSize];
+  std::unique_ptr<unsigned[]> Allocated;
+  unsigned *Row = SmallBuffer;
+  if (OtherSize + 1 > SmallBufferSize) {
+    Row = new unsigned[OtherSize + 1];
+    Allocated.reset(Row);
+  }
+
+  for (unsigned i = 1; i <= OtherSize; ++i)
+    Row[i] = i;
+
+  for (size_t y = 1; y <= Size; ++y) {
+    Row[0] = y;
+    unsigned BestThisRow = Row[0];
+
+    unsigned Previous = y - 1;
+    for (size_t x = 1; x <= OtherSize; ++x) {
+      int OldRow = Row[x];
+      if (AllowReplacements) {
+        Row[x] = std::min(
+            Previous +
+                (toLower(data()[y - 1]) == toLower(Other[x - 1]) ? 0u : 1u),
+            std::min(Row[x - 1], Row[x]) + 1);
+      } else {
+        if (toLower(data()[y - 1]) == toLower(Other[x - 1]))
+          Row[x] = Previous;
+        else
+          Row[x] = std::min(Row[x - 1], Row[x]) + 1;
+      }
+      Previous = OldRow;
+      BestThisRow = std::min(BestThisRow, Row[x]);
+    }
+
+    if (MaxEditDistance && BestThisRow > MaxEditDistance)
+      return MaxEditDistance + 1;
+  }
+
+  unsigned Result = Row[OtherSize];
+  return Result;
+}
+
 //===----------------------------------------------------------------------===//
 // String Operations
 //===----------------------------------------------------------------------===//
diff --git a/llvm/unittests/ADT/StringRefTest.cpp b/llvm/unittests/ADT/StringRefTest.cpp
--- a/llvm/unittests/ADT/StringRefTest.cpp
+++ b/llvm/unittests/ADT/StringRefTest.cpp
@@ -584,6 +584,15 @@
                                        "people soiled our green "));
 }
 
+TEST(StringRefTest, EditDistanceInsensitive) {
+  StringRef Hello("HELLO");
+  EXPECT_EQ(2U, Hello.edit_distance_insensitive("hill"));
+  EXPECT_EQ(0U, Hello.edit_distance_insensitive("hello"));
+
+  StringRef Industry("InDuStRy");
+  EXPECT_EQ(6U, Industry.edit_distance_insensitive("iNtErEsT"));
+}
+
 TEST(StringRefTest, Misc) {
   std::string Storage;
   raw_string_ostream OS(Storage);