Index: include/llvm/Support/StringPool.h
===================================================================
--- include/llvm/Support/StringPool.h
+++ include/llvm/Support/StringPool.h
@@ -130,8 +130,12 @@
     inline const char *operator*() const { return begin(); }
     inline operator bool() const { return S != nullptr; }
 
-    inline bool operator==(const PooledStringPtr &That) { return S == That.S; }
-    inline bool operator!=(const PooledStringPtr &That) { return S != That.S; }
+    inline bool operator==(const PooledStringPtr &That) const {
+      return S == That.S;
+    }
+    inline bool operator!=(const PooledStringPtr &That) const {
+      return S != That.S;
+    }
   };
 
 } // End llvm namespace