https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80700
--- Comment #6 from Segher Boessenkool <segher at gcc dot gnu.org> --- LR and CTR together are a register class -- they both can be used as jump target, in the same way. Converting LR to be a fixed register is not going to be trivial, either. But, where does it come from here: (define_insn "*mov_si<mode>_e500_subreg4_2_be" [(set (match_operand:SI 0 "rs6000_nonimmediate_operand" "=r,m") (subreg:SI (match_operand:SPE64TF 1 "register_operand" "r,r") 4))] where rs6000_nonimmediate_operand is essentially nonimmediate_operand, so int nonimmediate_operand (rtx op, machine_mode mode) { return (general_operand (op, mode) && ! CONSTANT_P (op)); } Things would work better if silly things were refused in the predicate already, instead of trying to reload and letting the constraint deal with it.