[Bug target/124448] RISC-V: Extract from tuple vector with lmul<1 may cause bad code generation

[rdapp at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124448

--- Comment #3 from Robin Dapp <rdapp at gcc dot gnu.org> ---
So one issue is that we consider tuple/segment modes (like RVVMF2x4HI) tieable
with e.g. RVVM2DI because they have the same size.  That's not ideal and causes
most of the bad codegen you're seeing.

Do you want to send a patch?  You'd need to adjust riscv_modes_tieable_p.
If not, I can go ahead.