On 9/27/2021 6:07 AM, Richard Biener via Gcc-patches wrote:
On Mon, Sep 27, 2021 at 11:42 AM Hongtao Liu <crazy...@gmail.com> wrote:
On Fri, Sep 24, 2021 at 9:08 PM Segher Boessenkool
<seg...@kernel.crashing.org> wrote:
On Mon, Sep 13, 2021 at 04:24:13PM +0200, Richard Biener wrote:
On Mon, Sep 13, 2021 at 4:10 PM Jeff Law via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
I'm not convinced that we need the inner mode to match anything. As
long as the vec_concat's mode is twice the size of the vec_select modes
and the vec_select mode is <= the mode of its operands ISTM this is
fine. We might want the modes of the vec_select to match, but I don't
think that's strictly necessary either, they just need to be the same
size. ie, we could have somethig like
(vec_concat:V2DF (vec_select:DF (reg:V4DF)) (vec_select:DI (reg:V4DI)))
I'm not sure if that level of generality is useful though. If we want
the modes of the vec_selects to match I think we could still support
(vec_concat:V2DF (vec_select:DF (reg:V4DF)) (vec_select:DF (reg:V8DF)))
Thoughts?
I think the component or scalar modes of the elements to concat need to match
the component mode of the result. I don't think you example involving
a cat of DF and DI is too useful - but you could use a subreg around the DI
value ;)
I agree.
If you want to concatenate components of different modes, you should
change mode first, using subregs for example.
I don't really understand.
for
(vec_concat:V2DF (vec_select:DF (reg:V4DF)) (vec_select:DF (reg:V8DF)))
Thoughts?
how can it be simplified when reg:V4DF is different from (reg:V8DF)
to
(vec_select: (vec_concat:(subreg V8DF (reg:V4DF) 0) (reg:V8DF))
(paralle[...])
?, which doesn't look like a simpication.
Similar for
(vec_concat:V2DF (vec_select:DF (reg:V4DF)) (vec_select:DI (reg:V4DI)))
here we require rtx_equal_p (XEXP (trueop0, 0), XEXP (trueop1, 0)) so
vec_concat (vec_select vec_select) can be simplified to just
vec_select.
Yes, I think your patch is reasonable, I don't understand how we can
intermediately convert here either or how that would help.
Agreed. It was never my intention to hold things up. I was just
curious about whether or not we wanted to relax things even further.
Jeff
