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 > >