[Bug tree-optimization/93771] SLP produces VEC_PERM when should have used vector generation

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93771

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #2)
> Confirmed.  I'm not sure if we should try to "fix" SLP here or rather
> appropriately optimize
> 
>   v2df tem1 = *(v2df *)&t[0];
>   v2df tem2 = *(v2df *)&t[2];
>   __builtin_shuffle (tem1, tem2 (v2di) { 0, 3 });
> 
> which the user could write itself.  forwprop does some related transforms
> splitting loads in "Rewrite loads used only in BIT_FIELD_REF extractions to
> component-wise loads."

I was thinking about originally filing the bug that way but I decided against
it; though I don't remember my reasoning besides I saw SLP not doing it for
unrelated loads.