Question about constructing vector types in GIMPLE pass

[Hanke Zhang via Gcc]

Hi,
I've been working on strengthening auto-vectorization on intel CPUs
recently. I tried to do it in the GIMPLE pass. And I noticed that some
vector types in the GIMPLE code are confusing to me. The example code
is here:

_1 = MEM[(const __m256i_u * {ref-all})_2];

I wondered how I could construct or get the type `(const __m256i_u *
{ref-all})` in the GIMPLE pass.

If you have any ideas that can help me. I'll be so grateful! :)

Thanks
Hanke Zhang