还能计算pi，计算的主要汇编程序，程序很快就跑完，速度很快
```
; ============================================================================
; compute_pi - compute pi in fixed point, scale 10^8, into r3
; pi*10^8 = 16*arctan(1/5) - 4*arctan(1/239) (Machin's formula)
; result: r3 = 314159264 (=> 3.1415926)
; uses: r1,r5,r8,r9,r13,r14 (stack: r10, r15)
; ============================================================================
compute_pi:
LDL r1, 5
LDL r13, 25
call pi_arctan ; r9 = A5 (10^8 * arctan(1/5))
MOV r8, r9 ; keep A5 in r8
LDL r1, 239
LDL r13, 57121
call pi_arctan ; r9 = A239 (10^8 * arctan(1/239))
MOV r13, r9
; pi*10^8 = 16*A5 - 4*A239 -> r3
LDL r1, 16
MUL r8, r1 ; r4 = 16*A5
MOV r14, r4
LDL r1, 4
MUL r13, r1 ; r4 = 4*A239
MOV r1, r4
SUB r14, r1 ; r4 = 16*A5 - 4*A239
MOV r3, r4
ret
```