On 10/17/18, Marc Glisse <marc.gli...@inria.fr> wrote:
> On Wed, 17 Oct 2018, H.J. Lu wrote:
>
>> We may simplify
>>
>> (subreg (vec_merge (vec_duplicate X) (vector) (const_int 1)) 0)
>>
>> to X when mode of X is the same as of mode of subreg.
>
> Hello,
>
> we already have code to simplify vec_select(vec_merge):
>
> /* If we select elements in a vec_merge that all come from the same
> operand, select from that operand directly. */
>
> It would make sense to me to make the subreg transform as similar to it as
> possible, in particular you don't need to special case vec_duplicate, the
> transformation would see that everything comes from the first vector,
> produce (subreg (vec_duplicate X) 0), and let another transformation
> optimize that.
What do you mean by another transformation? If simplify_subreg doesn't
return X for
(subreg (vec_merge (vec_duplicate X)
(vector)
(const_int ((1 << N) | M)))
(N * sizeof (X)))
no further transformation will be done.
--
H.J.
