On Tue, Dec 13, 2016 at 06:17:17PM -0500, Michael Meissner wrote:
> > > + else if (mode == V8HImode)
> > > + {
> > > + rtx tmp_gpr_si = (GET_CODE (tmp_gpr) == SCRATCH
> > > + ? dest_si
> > > + : gen_rtx_REG (SImode, REGNO (tmp_gpr)));
> >
> > I think you have these the wrong way around?
>
> The rs6000_split_vec_extract_var function is called from several places in
> vsx.md to do a variable vector extract. In looking at each of the cases,
> there
> is a GPR tmp register for each of the calls, so I could modify it to move:
>
> gcc_assert (REG_P (tmp_gpr));
>
> before the support for VEXTU{B,H,W}{L,R}X instructions, and leave the
>
> gcc_assert (REG_P (tmp_altivec));
>
> and remove the test for SCRATCH. In the original version of the code, the
> non-variable case also called rs6000_split_vec_extract_var, and it did not
> have
> a scratch register.
What I am asking is: in your code, if there is a scratch you don't use it,
while if you get a reg you generate a new reg. It looks like you have the
? and : the wrong way around.
> > You didn't address the reload_completed on all the splitters yet; is there
> > a reason for it?
[ ... ]
> Basically, until we know all of the details (i.e. after register allocator),
> we
> can't do the split, because the code is different.
Right.
> There is also the practical case that due to the funky way the scalar parts
> are
> not in the bottom part of the register, that SUBREG's really don't work
> between
> 64-bit and 128-bit items that go in vector registers. After register
> allocation, we can do gen_rtx_REG (<mode>, <regno>) to change the types, but
> that really doesn't work before register allocator.
Hrm. Nastiness.
Thanks for the explanation,
Segher
