On Jan 30, 2015, at 9:52 AM, Jakub Jelinek <ja...@redhat.com> wrote: > On Fri, Jan 30, 2015 at 09:45:26AM -0800, Mike Stump wrote: >> I have a port that has: >> >> (insn 47 46 48 18 (parallel [ >> (unspec_volatile:DI [ >> (const_int 128 [0x80]) >> (const_int 6 [0x6]) >> ] UNSPECV_SPECIAL_OP) >> (set (mem/v:BLK (scratch:DI) [0 A8]) >> (unspec:BLK [ >> (mem/v:BLK (scratch:DI) [0 A8]) >> ] UNSPEC_MEMORY_BARRIER)) > > Why don't you just (clobber (mem/v:BLK (scratch:DI))) instead > of the second set in the parallel? The instruction is already > UNSPEC_VOLATILE, and to make the barrier effect clear a clobber should be > sufficient.
So, f087d65d84655bc2d5fdd4bcc6bf0fe337a39893 seems to have introduced the current way that all the ports do this currently. So, I’d leave this to Richard to answer. If (clobber (mem/v:BLK (scratch:DI))) works, certainly that seems simpler than what people do now, but, then I’m left wondering, why didn’t we do that from that start?
