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

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