N阶阶乘.doc

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《计算机系统结构》
实验报告
专 业：
年 级：
学 号： 4

;************The statement of factorial**********
;***Prompts that need to show on the screen
Prompt: .asciiz "Please enter an integer value >1 : "
PrintfFormat: .asciiz "The number's Factorial = %g\n\n"
.align 2
PrintfPar: .word PrintfFormat
PrintfValue: .space 8
.text
.global main
main:
;*** Read value from stdin into R1
addi r1,r0,Prompt
jal InputUnsigned

;*** init values
movi2fp f10,r1 ;R1 -> D0 D0..Count register
cvti2d f0,f10
addi r2,r0,1 ;1 -> D2 D2..result
movi2fp f11,r2
cvti2d f2,f11
movd f4,f2 ;1-> D4 D4..Constant 1

;*** Break loop if D0 = 1
Loop: led f0,f4 ;D0<=1 ?
5
bfpt Finish

;*** Multiplication and next loop
multd f2,f2,f0
subd f0,f0,f4
j Loop
Finish: ;*** write result to stdout
sd PrintfValue,f2
addi r14,r0,PrintfPar
trap 5

;*** end
;***The Input Module
InputUnsigned:
;*** save register contents
sw SaveR2,r2
sw SaveR3,r3
sw SaveR4,r4
sw SaveR5,r5
;*** Prompt
sw PrintfPar1,r1
addi r14,r0,PrintfPar1
trap 5
;*** call Trap-3 to read line
addi r14,r0,ReadPar
trap 3
;*** determine value
addi r2,r0,ReadBuffer
addi r1,r0,0
addi