diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
index f299f5fd6517..a7442666d678 100644
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -159,12 +159,14 @@ namespace llvm {
 
     /// startswith - Check if this string starts with the given \arg Prefix.
     bool startswith(StringRef Prefix) const {
-      return substr(0, Prefix.Length).equals(Prefix);
+      return Length >= Prefix.Length &&
+             memcmp(Data, Prefix.Data, Prefix.Length) == 0;
     }
 
     /// endswith - Check if this string ends with the given \arg Suffix.
     bool endswith(StringRef Suffix) const {
-      return slice(size() - Suffix.Length, size()).equals(Suffix);
+      return Length >= Suffix.Length &&
+             memcmp(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
     }
 
     /// @}
diff --git a/llvm/unittests/ADT/StringRefTest.cpp b/llvm/unittests/ADT/StringRefTest.cpp
index dfa208abefdc..19665df88d54 100644
--- a/llvm/unittests/ADT/StringRefTest.cpp
+++ b/llvm/unittests/ADT/StringRefTest.cpp
@@ -198,6 +198,14 @@ TEST(StringRefTest, StartsWith) {
   EXPECT_FALSE(Str.startswith("hi"));
 }
 
+TEST(StringRefTest, EndsWith) {
+  StringRef Str("hello");
+  EXPECT_TRUE(Str.endswith("lo"));
+  EXPECT_FALSE(Str.endswith("helloworld"));
+  EXPECT_FALSE(Str.endswith("worldhello"));
+  EXPECT_FALSE(Str.endswith("so"));
+}
+
 TEST(StringRefTest, Find) {
   StringRef Str("hello");
   EXPECT_EQ(2U, Str.find('l'));