Add generic support for hashing StringRef objects using the new hashing library.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152003 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/StringRef.cpp

@@ -10,6 +10,7 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/edit_distance.h"
 #include <bitset>
 
@@ -447,3 +448,9 @@ bool StringRef::getAsInteger(unsigned Radix, APInt &Result) const {
 
   return false;
 }
+
+
+// Implementation of StringRef hashing.
+hash_code llvm::hash_value(StringRef S) {
+  return hash_combine_range(S.begin(), S.end());
+}