6 .type _strlen,@function
8 add #0, r1, r4 ; Save a copy of the string start address and set the condition flags.
9 beq null_string ; Test for a NULL pointer.
10 mov #-1, r3 ; Set a limit on the number of bytes examined.
11 mov #0, r2 ; Stop searching when we find a NUL byte.
12 suntil.b ; Search until *r1 == r2
13 sub #1, r1 ; suntil.b leaves r1 pointing to the byte beyond the match.
15 sub r4, r1 ; Compute the length.