Hi Richard
I just found that modifying match.pd may be a better way since for
forwprop-19.c, VEC_PERM_EXPR exists in all gimple until 235t.optimize with
current trunk code, that leave us no pass to ‘scan-tree-dump-not’.
Best Regards
Levy
> On 14 Oct 2022, at 2:19 pm, Richard Biener <richard.guent...@gmail.com> wrote:
>
> On Fri, Oct 14, 2022 at 3:49 AM Lulu Cheng <chengl...@loongson.cn> wrote:
>>
>>
>>> 在 2022/10/13 下午7:10, Richard Biener 写道:
>>> On Thu, Oct 13, 2022 at 10:16 AM Lulu Cheng <chengl...@loongson.cn> wrote:
>>>>
>>>> 在 2022/10/13 下午2:44, Xi Ruoyao 写道:
>>>>> On Thu, 2022-10-13 at 14:15 +0800, Levy wrote:
>>>>>> Hi RuoYao
>>>>>>
>>>>>> It’s probably because loongarch64 doesn’t support
>>>>>> can_vec_perm_const_p(result_mode, op_mode, sel2, false)
>>>>>>
>>>>>> I’m not sure whether if loongarch will support it or should I just
>>>>>> limit the test target for pr54346.c?
>>>>> I'm not sure if we can add TARGET_VECTORIZE_VEC_PERM_CONST when we don't
>>>>> actually support vector. (LoongArch has SIMD instructions but the
>>>>> support in GCC won't be added in a very recent future.)
>>>>>
>>>> If what I understand is correct, I think this might be a better solution.
>>>>
>>>> /* { dg-do compile } */
>>>>
>>>> +/* { dg-require-effective-target vect_perm } */
>>>> /* { dg-options "-O -fdump-tree-dse1" } */
>>> Btw, what forwprop does is check whether any of the original permutations
>>> are
>>> not supported and then elide the supportability check for the result.
>>> The reasoning
>>> is that the original permute(s) would be lowered during vectlower so we can
>>> as
>>> well do that for the result. We should just never turn a supported
>>> permutation
>>> sequence into a not supported one.
>>>
>>> Richard.
>>>
>> Hi Richard:
>>
>> I'm very sorry. I don't fully understand what you mean.
>>
>> Could you give me some more details?
>
> The argument is that if Loongarch64 doesn't support the VEC_PERM_EXPR in the
> IL
> before the transform then it doesn't matter if the transform introduces
> another
> VEC_PERM_EXPR that isn't supported. Both are later (in the veclower pass)
> lowered to scalar operations.
>
> So instead of
>
> if (can_vec_perm_const_p (result_mode, op_mode, sel2, false))
> ..
>
> you'd do
>
> if (can_vec_perm_const_p (result_mode, op_mode, sel2, false)
> || !can_vec_perm_const_p ( ... original vec_perm1 ...)
> || !can_vec_perm_const_p ( ... original vec_perm2 ...))
>
> Richard.
>
>>
>> Thanks!
>>
>> Lulu Cheng
>>
