"H.J. Lu" <hjl.to...@gmail.com> writes:
> On 10/18/18, Richard Sandiford <richard.sandif...@arm.com> wrote:
>> "H.J. Lu" <hjl.to...@gmail.com> writes:
>>> On 10/18/18, Richard Sandiford <richard.sandif...@arm.com> wrote:
>>>> "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.
>>>
>>> But sizeof (X) is the size of scalar of vec_dup. How do we
>>> check the mask of vec_merge?
>>
>> Yeah, should be sizeof (outermode) (which was the same thing
>> in the original pattern, but not here).
>>
>> Richard
>>
>
> Like this
>
> diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
> index b0cf3bbb2a9..e12b5c0e165 100644
> --- a/gcc/simplify-rtx.c
> +++ b/gcc/simplify-rtx.c
> @@ -6601,20 +6601,21 @@ simplify_subreg (machine_mode outermode, rtx op,
> return NULL_RTX;
> }
>
> - /* Return X for
> - (subreg (vec_merge (vec_duplicate X)
> + /* Simplify
> + (subreg (vec_merge (X)
> (vector)
> (const_int ((1 << N) | M)))
> - (N * sizeof (X)))
> + (N * sizeof (outermode)))
> + to
> + (subreg ((X) (N * sizeof (outermode)))
Stray "(": (subreg (X) (N * sizeof (outermode)))
OK with that change if it passes testing.
Thanks,
Richard
> */
> unsigned int idx;
> if (constant_multiple_p (byte, GET_MODE_SIZE (outermode), &idx)
> && GET_CODE (op) == VEC_MERGE
> - && GET_CODE (XEXP (op, 0)) == VEC_DUPLICATE
> - && GET_MODE (XEXP (XEXP (op, 0), 0)) == outermode
> + && GET_MODE_INNER (innermode) == outermode
> && CONST_INT_P (XEXP (op, 2))
> && (UINTVAL (XEXP (op, 2)) & (HOST_WIDE_INT_1U << idx)) != 0)
> - return XEXP (XEXP (op, 0), 0);
> + return simplify_gen_subreg (outermode, XEXP (op, 0), innermode, byte);
>
> /* A SUBREG resulting from a zero extension may fold to zero if
> it extracts higher bits that the ZERO_EXTEND's source bits. */
