Hi! On Thu, Aug 25, 2022 at 08:11:31PM +0800, Jiufu Guo wrote: > Segher Boessenkool <seg...@kernel.crashing.org> writes: > > You usually can split fine if you cannot create new pseudos, by reusing > > existing registers. > > > > FAIL will cause an ICE: the RTL instruction does match, but will fail > > when trying to generate machine code for it. > > > Previous patch is using "gen_reg_rtx (DImode)" to generate a pseudo for > the rotated result to prevent orignal one being changed accidently. > So, an 'assert (can_create_pseudo_p ())' would catch it in after RA.
It sounds like you want a define_split, not a define_insn_and_split. That is much more stomachable anyway. Anything that creates conditional branches together with compars insns belongs before RA, before sched1 even. > To enable this splitter works after RA, we may need to reserve one > register (clobber would be ok). Such as below: > > [(set (pc) > (if_then_else (eqne (match_operand:DI 1 "gpc_reg_operand" "r") > (match_operand:DI 2 "const_int_operand" "n")) > (label_ref (match_operand 0 "")) > (pc))) > (clobber (match_scratch:DI 3 "=r")) > (clobber (match_scratch:CCUNS 4 "=y"))] Yes, that is one way to do it. Another way is to reuse operand 1. A clobber is probably better in this case though :-) If this is only so combine can match things, you certainly want just a define_split, and the compare+branch in one pattern is not as bad then. Segher
