FP conversion from larger-sized FP numbers to smaller-sized ones is needed: FP64->FP32, FP64->FP16, FP32->FP16. unit tests also needed, with full (comprehensive) coverage.
last unit test added, all covered: https://git.libre-riscv.org/?p=ieee754fpu.git;a=commitdiff;h=ff5df25d28e88a15edee6d72e29c54fe105672e3