> But I can see that there could be a problem with an earlier value > that used to be valid in a multi-hard-register sub register to be > considered to be still valid. > Setting the mode of every constituent register but the first one > (which has the new value recorded) to VOIDmode at the same time > as updating reg_set_luid should be sufficent to address this issue.
Agreed. > The pass was originally written with word_mode == Pmode targets like > the SH in mind, where multi-hard-register values are uninteresting. > > But for targets like the avr, most or all of the interesting values > will be in multi-hard-register registers. The patch is OK on principle, but can you factor out the common code? The endings of move2add_use_add2_insn and move2add_use_add3_insn are identical so it would be nice to have e.g. a record_reg_value helper function and call it from there. Similarly, the 3 new checks look strictly identical. -- Eric Botcazou
