diff --git a/lib/Target/Alpha/AlphaISelLowering.cpp b/lib/Target/Alpha/AlphaISelLowering.cpp
index 54433a4c36f..e8aaf353b33 100644
--- a/lib/Target/Alpha/AlphaISelLowering.cpp
+++ b/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);
     }
   }