how to map CLabel to Label for procedure entry point?

I'm struggling to figure out how to get from a CLabel found in a CmmProc to a Label used to key the blocks in the control-flow graph (CmmGraph) for the CmmProc. The code generator needs such a function, so it must be around somewhere, but I have not yet found it. I've poked around the respective modules for CLabel and for Label, and also modules like CmmToAsm. Can anyone help me out? Norman