Index: include/llvm/ADT/StringRef.h
===================================================================
--- include/llvm/ADT/StringRef.h
+++ include/llvm/ADT/StringRef.h
@@ -496,6 +496,28 @@
       return drop_front(size() - N);
     }
 
+    template <typename Func>
+    LLVM_ATTRIBUTE_UNUSED_RESULT StringRef take_while(Func F) const {
+      StringRef S(*this);
+      while (!S.empty()) {
+        if (!F(S.front()))
+          break;
+        S = S.drop_front();
+      }
+      return drop_back(S.size());
+    }
+
+    template <typename Func>
+    LLVM_ATTRIBUTE_UNUSED_RESULT StringRef take_until(Func F) const {
+      StringRef S(*this);
+      while (!S.empty()) {
+        if (F(S.front()))
+          break;
+        S = S.drop_front();
+      }
+      return drop_back(S.size());
+    }
+
     /// Return a StringRef equal to 'this' but with the first \p N elements
     /// dropped.
     LLVM_ATTRIBUTE_ALWAYS_INLINE
@@ -514,6 +536,28 @@
       return substr(0, size()-N);
     }
 
+    template <typename Func>
+    LLVM_ATTRIBUTE_UNUSED_RESULT StringRef drop_while(Func F) const {
+      StringRef S(*this);
+      while (!S.empty()) {
+        if (!F(S.front()))
+          break;
+        S = S.drop_front();
+      }
+      return S;
+    }
+
+    template <typename Func>
+    LLVM_ATTRIBUTE_UNUSED_RESULT StringRef drop_until(Func F) const {
+      StringRef S(*this);
+      while (!S.empty()) {
+        if (F(S.front()))
+          break;
+        S = S.drop_front();
+      }
+      return S;
+    }
+
     /// Returns true if this StringRef has the given prefix and removes that
     /// prefix.
     LLVM_ATTRIBUTE_ALWAYS_INLINE
Index: unittests/ADT/StringRefTest.cpp
===================================================================
--- unittests/ADT/StringRefTest.cpp
+++ unittests/ADT/StringRefTest.cpp
@@ -864,4 +864,44 @@
   EXPECT_TRUE(Taken.empty());
 }
 
+TEST(StringRefTest, TakeWhileUntil) {
+  StringRef Test("String With 1 Number");
+
+  StringRef Taken = Test.take_while(::isdigit);
+  EXPECT_EQ("", Taken);
+
+  Taken = Test.take_until(::isdigit);
+  EXPECT_EQ("String With ", Taken);
+
+  Taken = Test.take_while([](char c) { return true; });
+  EXPECT_EQ(Test, Taken);
+
+  Taken = Test.take_until([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+
+  Test = "";
+  Taken = Test.take_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+}
+
+TEST(StringRefTest, DropWhileUntil) {
+  StringRef Test("String With 1 Number");
+
+  StringRef Taken = Test.drop_while(::isdigit);
+  EXPECT_EQ(Test, Taken);
+
+  Taken = Test.drop_until(::isdigit);
+  EXPECT_EQ("1 Number", Taken);
+
+  Taken = Test.drop_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+
+  Taken = Test.drop_until([](char c) { return true; });
+  EXPECT_EQ(Test, Taken);
+
+  Test = "";
+  Taken = Test.drop_while([](char c) { return true; });
+  EXPECT_EQ("", Taken);
+}
+
 } // end anonymous namespace