On Fri, Sep 21, 2018 at 12:50:40PM +0200, Ulrich Weigand wrote:
> Ilya Leoshkevich wrote:
>
> > 2018-09-19 Ilya Leoshkevich <i...@linux.ibm.com>
> >
> > PR target/80080
> > * config/s390/s390.md: Do not use PARALLEL RETURN+USE when
> > returning via %r14.
>
> This makes sense to me. I'm just wondering if it wouldn't be
> simpler to do the check for r14 right in s390_emit_epilogue
> and then just call gen_return instead of gen_return_use
> directly there?
I had the same thought :-)
> > +++ b/gcc/config/s390/s390.md
> > @@ -10831,6 +10831,13 @@
> > (use (match_operand 0 "register_operand" "a"))])]
> > ""
> > {
> > + if (REGNO (operands[0]) == RETURN_REGNUM && s390_can_use_return_insn ())
>
> This probably cannot happen in practice in this specific case,
> but in general a register_operand may also be e.g. a SUBREG,
> so you shouldn't use REGNO without first verifying that this
> is a REG. (If you move the check to s390_emit_epilogue as above,
> this point is moot; you don't even need to generate a REG RTX
> if it's for r14 then.)
There is reg_or_subregno exactly for this.
Segher
