BSET - RISC-V instruction reference

bsetSet bit 
Sets t1 to t2 with the bit whose index is in the low bits of t3 set.
RISC-V manual: bset 
Forms  bset , ,   
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. 
t3 An integer register. It may be the same register as t1. 
 .text
li t0, 9
li t1, 2
# t0=9, t1=2; bset writes 13 to t2.
bset t2, t0, t1