Hi! On Thu, Dec 31, 2020 at 09:54:01AM +0100, Uros Bizjak wrote: > On Thu, Dec 31, 2020 at 9:40 AM Segher Boessenkool > <seg...@kernel.crashing.org> wrote: > > Nice. Just one thing: in principle the splitters can be used outside of > > combine, too? This can lead to insns that do not recog() then? Is > > there anything that prevents that from happening? > > No, combine splitters can't be used outside combine pass. These > splitters only split non-recognizable (non-existing) instructions, and > this is how they are told apart from general split insns.
There is only a define_split, not also a define_insn that matches the pattern (or a define_insn_and_split), but that is *not* unique to splitters that are meant for combine. It isn't likely that any other pass would try to create this pattern, but this isn't guaranteed, and such other passes do not necessarily do the add-the-clobber (that is specific to combine, even!) Maybe fwprop could create this insn, or something like Richard's new combine-like pass. > Also, most > of these combine splitters were added recently, but for those I added, > I was not aware of the clobber adding detail (which simplifies some > patterns quite nicely). Indeed it does :-) I just think it is a bit dangerous. Segher
