Quoting Michael Meissner <meiss...@linux.vnet.ibm.com>:
Generally you need to tighten the pattern conditions to make sure it doesn't match.
Sometimes the only sane and effective way of tightening the pattern conditions is to have an insn condition of "0". At which point the define_insn_and_split becomes syntactic sugar (plus starch, guar gum, stabilizers and emulsifiers) for just having a splitter pattern.
