On Sun, 2020-03-01 at 00:55 +0900, Oleg Endo wrote: > On Sat, 2020-02-29 at 08:47 -0700, Jeff Law wrote: > > It's almost certainly the case that the recent IRA changes are going to > > stress > > R0 more. If I'm reading what Vlad did correctly, one of the tie-breakers > > its > > using now is to choose the lowest numbered register when all else is > > equal. So > > R0 on SH is likely going to be more problematical. > > > > I wonder if just reordering the regs on the SH (and adjusting the debug > > output > > to keep that working) would be enough to mitigate some of the R0 problems. > > It could open a can of worms. Off the top of my head, R0 is used to > hold the function return value, and R0:R1 to return structs with sizeof > > 4 bytes. So if DImode is allocated to R0, it implicitly uses R0:R1, > AFAIR, doesn't it? Would that kind of thing cause troubles? It might. We might have to move a pair or even a quad if you have modes that cover r0-r3. It may not be feasible in practice. I was just thinking off the top of my head.
jeff
