MAXU - RISC-V instruction reference

maxuMaximum (unsigned) 
Sets t1 to the larger of t2 and t3, comparing as unsigned.
RISC-V manual: maxu 
Forms  maxu , ,   
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, 18
li t1, 5
# t0=18, t1=5; maxu writes 18 to t2.
maxu t2, t0, t1