[Bug target/88963] gcc generates terrible code for vectors of 64+ length which are not natively supported

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88963

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
You can try the attached patch, it "fixes" the issue on the GIMPLE side but
appearantly the BIT_FIELD_REF stores go a weird path during RTL expansion
and so we end up spilling again.