If I use:
(define_expand addsi
[(set (match_operand:SI 0 general_operand =g)
(plus:SI (match_operand:SI 1 general_operand g)
(match_operand:SI 2 general_operand g)))]
{
emit_insn (gen_addhi3 (custom_subword(operands[0], 0, SImode),
I have a fictitious machine which has a word size of 8-bits but can handle
16-bit adds and 16-bit mov's. I am trying to build the most efficient support
for handling an addsi3 insn. My problem is that if I try to split up the
addsi3 insn into a couple of addhi3 insns (using a define_expand
