On Tue, Jul 14, 2015 at 07:04:13PM +0800, pins...@gmail.com wrote: > Combine knows how to use define_split without being an insn.
Combine uses define_split in very different circumstances than it uses define_insn. In this case, define_split will only do anything if the "nabs" is combined from three insns, while a define_insn handles it being combined from two as well. A define_split will be split during combine (and combine can then work on its factors); a define_insn is only split _after_ combine. Segher
