[Bug target/110748] RISC-V: optimize store of DF 0.0

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110748

--- Comment #18 from Jeffrey A. Law <law at gcc dot gnu.org> ---
I suspect this is (or can be trivially be) handled by Philipp's recently posted
patch which synthesizes subsets of FP constants into integer registers, then
moves them into the final destination with fmv.[sd].x.