https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83699
--- Comment #2 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> --- Created attachment 43047 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43047&action=edit Hacky patch In no-scevccp-outer-10.c, LRA enters a cycle trying to move (subreg:SI (reg:V2SI R) 0) into a GPR. It emits: (set (reg:SI tmp) (subreg:SI (reg:V2SI R) 0)) (set (reg:SI dest) (reg:SI tmp)) and sets the class of "tmp" to ALL_REGS. We then assign a GPR to it, creating the same problem again. The subreg is valid for SPARC because of REGMODE_NATURAL_SIZE. I think the problem is that TMP needs to be restricted to EXTRA_FP_REGS. The attached patch does that in a hacky way. I think a more correct way of achieving the same thing would be to make LRA take simplifiable_subregs into account when picking the register for a subreg reload, just as IRA does. I'm not sure whether this is the problem for all the mentioned tests or not.
