(epilogue insn): Don't provide this if a return insn will suffice.
(m88k_end_epilogue): If the last insn isn't a barrier, print a return.
(compare word insns): New insns and define_split
patterns to take advantage of recent fold_truthop change.
(superoptimizer sequences): New define_split patterns.
(add/sub with carry): New insns.
(add/sub DImode, ffssi2): Clobber the condition code register.