ARM: properly handle alignment for struct byval.

Factor out the expansion code into a function.
This change is to be enabled in clang.

rdar://9877866

llvm-svn: 157830
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.h b/llvm/lib/Target/ARM/ARMISelLowering.h
index d11171e..a113878 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.h
+++ b/llvm/lib/Target/ARM/ARMISelLowering.h
@@ -530,6 +530,9 @@
                                              MachineBasicBlock *MBB) const;
 
     bool RemapAddSubWithFlags(MachineInstr *MI, MachineBasicBlock *BB) const;
+
+    MachineBasicBlock *EmitStructByval(MachineInstr *MI,
+                                       MachineBasicBlock *MBB) const;
   };
 
   enum NEONModImmType {