Add a TODO for the Alpha port inline asm constraints.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134089 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Alpha/AlphaISelLowering.cpp

@@ -835,6 +835,8 @@ getRegForInlineAsmConstraint(const std::string &Constraint, EVT VT) const
     case 'r':
       return std::make_pair(0U, Alpha::GPRCRegisterClass);
     case 'f':
+      // TODO: Do we need to add the 64-bit register class here when
+      // it contains the same registers?
       return std::make_pair(0U, Alpha::F4RCRegisterClass);
     }
   }