Aurelien Buhrig <aurelien.buhrig.gcc@xxxxxxxxx> writes: > My main problem is when defining a *movhi insn whose > constraints/predicates only support r registers, GCC may reload some r > register into A subreg:HI register, and complains because the insn > *movhi does not satisfy its constraints (r). How to prevent this ? I assume that the register can in principle hold the value, so changing HARD_REGNO_MODE_OK would not be appropriate. What you want here is REGISTER_MOVE_COST. However, gcc will try to use all available registers in some cases, so if you can't move values between the register classes easily you will need to define TARGET_SECONDARY_RELOAD. > BTW, to handle movhi from subreg:HI A to subreg:HI A, which is not > supported by the target: should I define a define_expand movhi whose > predicates supports such an operation, and then, provide a > define_split to froce passing through a r reg ? Is there a more > efficient way to do this ? This is what TARGET_SECONDARY_RELOAD is for. Ian
