[Bug target/126550] RISC-V: auto-vectorization miscompiles duplicated deinterleave store via vcompress/vrgather (rv64gcv_zvl256b)

[rdapp at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126550

--- Comment #3 from Robin Dapp <rdapp at gcc dot gnu.org> ---
Possibly two issues.  We expand the const permute index through a VLA route.  I
don't think that's useful for 99% of the cases, in particular if we load from
the literal pool anyway... (and could have loaded the constant directly).  But
that's just a missed optimization.

The second issue is that the VLA route for this constant is bogus.