Index: include/llvm/CodeGen/GlobalISel/CallLowering.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/CallLowering.h
+++ include/llvm/CodeGen/GlobalISel/CallLowering.h
@@ -102,7 +102,8 @@
     virtual bool assignArg(unsigned ValNo, MVT ValVT, MVT LocVT,
                            CCValAssign::LocInfo LocInfo, const ArgInfo &Info,
                            CCState &State) {
-      return AssignFn(ValNo, ValVT, LocVT, LocInfo, Info.Flags, State);
+      return AssignFn ?
+          AssignFn(ValNo, ValVT, LocVT, LocInfo, Info.Flags, State) : false;
     }
 
     MachineIRBuilder &MIRBuilder;
@@ -126,13 +127,6 @@
   void setArgFlags(ArgInfo &Arg, unsigned OpNum, const DataLayout &DL,
                    const FuncInfoTy &FuncInfo) const;
 
-  /// Invoke Handler::assignArg on each of the given \p Args and then use
-  /// \p Callback to move them to the assigned locations.
-  ///
-  /// \return True if everything has succeeded, false otherwise.
-  bool handleAssignments(MachineIRBuilder &MIRBuilder, ArrayRef<ArgInfo> Args,
-                         ValueHandler &Callback) const;
-
 public:
   CallLowering(const TargetLowering *TLI) : TLI(TLI) {}
   virtual ~CallLowering() = default;
@@ -188,6 +182,14 @@
     return false;
   }
 
+  /// Invoke Handler::assignArg on each of the given \p Args and then use
+  /// \p Callback to move them to the assigned locations.
+  ///
+  /// \return True if everything has succeeded, false otherwise.
+  virtual bool handleAssignments(MachineIRBuilder &MIRBuilder,
+                                 ArrayRef<ArgInfo> Args,
+                                 ValueHandler &Handler) const;
+
   /// Lower the given call instruction, including argument and return value
   /// marshalling.
   ///