Odph is equivalent to
--
--    -O2                               optimise as much as possible
--    -fmax-simplifier-iterations20     this is necessary sometimes
--    -fsimplifier-phases=3             we use an additional simplifier phase for fusion
--
setDPHOpt :: DynFlags -> DynP DynFlags
setDPHOpt dflags = setOptLevel 2 (dflags { maxSimplIterations  = 20
                                         , simplPhases         = 3
                                         })

se
setDPHOpt :: DynFlags -> DynP DynFlags
setDPHOpt dflags = setOptLevel 2 (dflags { maxSimplIterations  = 20
                                         , simplPhases         = 3
                                         })
setDPHOpt dflags = setOptLevel 2 (dflags { maxSimplIterations  = 20
                                         , simplPhases         = 3
                                         })