[Bug target/120245] RISC-V: Avoid FRM read/writes in non FRM related code paths

[vineetg at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120245

--- Comment #1 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
Or maybe instead of tracking the backup reg, track the FRM itself.
It seems to be a hard reg so live tracking is easier.