[Bug target/123870] [riscv64] ICE on vzext_vf2 and xtheadvector

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123870

--- Comment #6 from Jeffrey A. Law <law at gcc dot gnu.org> ---
Yes, the thead stuff is not in good shape; I don't think we're at the point of
recommending its removal (yet) as it's largely stayed out of the way.  However,
I think both Robin and I are concerned about the maintainability of that code.

As for these specific issues, I do recall fixing on vmvNr issue on
thead-vector, it was some time ago, so definitely possible I fixed in gcc-15,
but never backported to gcc-14.   Though IIRC it was related to
multiply-accumulates which I don't think are in play here.