Need help with DImode hard regs in MD file

[Richard Kenner]

    >   emit_move_insn (operands[0], gen_lowpart (SImode, r));

    Several times you've written email with things like this, 
    whereas the i370 code uses what I beleive to be the equivalent:

    emit_insn (gen_rtx_SET (VOIDmode, operands[0],
                           gen_rtx_SUBREG (SImode, r, 1))); 

    Are these in fact equivalent? Is one somehow better than the other?

They generate the same RTL if and only if R is a REG, and there's no
define_expand in the MD file, but the former is always better than the
latter since it is clearer what is going on and it's also
machine-independent.

I understand that this is in a machine-dependent file, but it's still best
to write things in as machine-independent a way as possible since that will
make it less dependent on other config file changes and also allow easier
reuse of the code for another port.