Fix a bug in the TopoOrderRC comparison function.

The final tie breaker comparison also needs to return +/-1, or 0.
This is not a less() function.

This could cause otherwise identical super-classes to be ordered
unstably, depending on what the system qsort routine does with a bad
compare function.

llvm-svn: 149549

llvm/utils/TableGen/CodeGenRegisters.cpp

@@ -503,7 +503,7 @@ static int TopoOrderRC(const void *PA, const void *PB) {
     return 1;
 
   // Finally order by name as a tie breaker.
-  return A->getName() < B->getName();
+  return StringRef(A->getName()).compare(B->getName());
 }
 
 std::string CodeGenRegisterClass::getQualifiedName() const {