体系结构试验--DLX指令集--myFACT.…

;--------------------------------------------------------------------------

; Program begin at symbol main

; requires module INPUT

; read a number from stdin and calculate the factorial (type:double)

; the result is written to stdout

;--------------------------------------------------------------------------

.data

Prompt: .asciiz "An integer value >1 : "

PrintfFormat: .asciiz "Factorial = %g\n\n"；输出格式，表示求出的阶乘按什么格式输出

.align 2  ;表示下面采用字对齐

PrintfPar: .word PrintfFormat

PrintfValue: .space 8

.text ;第一代码段，默认情况下代码段$CODE会加载到内存0x100地址处.global main ;即该代码段的首地址

main:

addi r1,r0,Prompt ;Read valuefrom stdin into R1

jal InputUnsigned ;跳转到InputUnsigned子程序处读取输入的参数，同时将一条指令的地址存与r31中，即r31<-pc+4

              addd f2,f2,f0

              addd f4,f4,f6

;*** 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 ?

bfpt Finish

;*** Multiplication and next loop

multd f2,f2,f0

subd f0,f0,f4

              subd          f0,f0,f4

j Loop

Finish: ;*** write result to stdout

sd PrintfValue,f2

addi r14,r0,PrintfPar

trap 5

;*** end

trap 0