FSRM: RISC-V instruction reference

fsrmSwap FP rounding mode Pseudo-instruction
Swaps the second register into the FP rounding mode, storing the old mode in the first, or, when given one register, only writes that register.
RISC-V manual: csrrw 
Forms  fsrm ,   
 fsrm   
Write FP rounding mode
Operands t1 Any integer register, x0 to x31, or its named alias, such as zero, t0 or t6. 
t2 An integer register. It may be the same register as t1. 
 # Initialize frm, then use fsrm to read its old value or update it.
.text
li t3, 0
csrw t3, frm
li t0, 1
fsrm t1, t0
# t1=0 is the old value; frm becomes 1.