DataLayout now returns a const ref to its member string representation

There was no particular reason to return by value in the first place.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 240826

llvm/include/llvm/IR/DataLayout.h

@@ -222,7 +222,9 @@ public:
   /// This representation is in the same format accepted by the string
   /// constructor above. This should not be used to compare two DataLayout as
   /// different string can represent the same layout.
-  std::string getStringRepresentation() const { return StringRepresentation; }
+  const std::string &getStringRepresentation() const {
+    return StringRepresentation;
+  }
 
   /// \brief Test if the DataLayout was constructed from an empty string.
   bool isDefault() const { return StringRepresentation.empty(); }

llvm/include/llvm/IR/Module.h

@@ -249,7 +249,7 @@ public:
 
   /// Get the data layout string for the module's target platform. This is
   /// equivalent to getDataLayout()->getStringRepresentation().
-  const std::string getDataLayoutStr() const {
+  const std::string &getDataLayoutStr() const {
     return DL.getStringRepresentation();
   }