"H.J. Lu" <hjl.to...@gmail.com> writes:
> 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.
Sorry, didn't see this before the OK.
> 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.
I think the point was that we should transform:
(subreg (vec_merge X
(vector)
(const_int ((1 << N) | M)))
(N * sizeof (X)))
into:
simplify_gen_subreg (outermode, X, innermode, byte)
which should further simplify when X is a vec_duplicate.
Thanks,
Richard
