mapping = foldr plusUFM emptyUFM mappings
build_mapping top@(CmmData _ _) = (top, emptyUFM)
-build_mapping (CmmProc info lbl params []) $
+build_mapping (CmmProc info lbl params [])
= (CmmProc info lbl params [], emptyUFM)
build_mapping (CmmProc info lbl params (head:blocks))
= (CmmProc info lbl params (head:others), mapping)