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標 題Re: [問題] 有關MIPS的問題
發信站交大資科_BBS (Sat Oct 7 23:13:24 2006)
轉信站ptt!ctu-reader!ctu-peer!news.nctu!news.cis.nctu!cis_nctu
==> 在 [email protected] (小浩浩) 的文章中提到:
> 不知道這邊有沒有人對這組合語言比較熟悉的
> 我是初學者，在寫程式時遇見一些問題，希望有高手可以替我回答唷 謝謝^^
> 以下附題目跟code 下半部有一行指令一直會出錯
> 希望有人可以幫我看看唷 謝謝大家這麼有耐心^^
> Q：Using SPIM, write and test a program that reads in a positive integer
> using the SPIM system calls. If the integer is not positive, the program should
> terminate with the message “Invalid Entry”; otherwise the program should print
> out the names of the digits of the integers, delimited by exactly one space. For
> example, if the user entered “728,” the output would be “Seven Two Eight.”
> #程式開始
> .data
> msg: .asciiz "Invalid Entry\n"
> prompt: .asciiz "Enter a positive integer..."
> # Fix the length of the elements of the "name" array
> names: .asciiz "Zero "
> .space 1
> .asciiz "One "
> .space 2
> .asciiz "Two "
> .space 2
> .asciiz "Three "
> .asciiz "Four "
> .space 1
> .asciiz "Five "
> .space 1
> .asciiz "Six "
> .space 2
> .asciiz "Seven "
> .asciiz "Eight "
> .asciiz "Nine "
> .space 1
> # .globl main
> # .data
> .align 2
> digits: .space 10
> .globl main
> .text
> # push return address
> main: sw $ra,0($sp)
> addi $sp,$sp,-4
> # DIY1: print a prompt
> la $a0, prompt # load string address into $a0 and I/O code into $v0
> li $v0, 4
> syscall # execute the syscall to perform input/output
> # DIY2: Read an integer
> li $v0, 5 # an I/O sequence to read an integer from
> # the console window
> syscall
> move $t1, $v0 # place the value read into register $t0
> # DIY3: Reject if non-positive
> slt $s0,$t1,$zero
> beq $s0,$zero,cont
> la $a0, msg # load string address into $a0 and I/O code into $v0
> li $v0, 4
> syscall # execute the syscall to perform input/output
> j main
> # Extract digits (right to left, store in digits[0]..)
> cont:
> addi $a0,$zero, 10
> addi $t0,$zero, 0
> again: div $v0,$a0
> mflo $v0 # v0 = v0 div 10
> mfhi $t1 # t1 = v0 mod 10
> sb $t1,digits($t0)
> beq $v0, $zero, abort # leave if v0 became 0
> beq $t0, $a0, abort # or if 10 digits were extracted
> addi $t0, $t0,1
> j again
> abort: # print the digits
> addi $t7, $zero, 7 #t7=7, why? In order to access the data in names.
> lb $t5, digits($t0)
> beq $t5, $zero, skip #skip leading zero
> next:
> mult $t5,$t7
> mflo $t5 # offset
> addi $a0, $t5, names # a0 = the Name's address
//addi 是把t5加一個立即值(names)再存到a0,立即值長度應該只有16bits(signed)
//names 的值若是address應該有32bits長. 組譯時就會有錯誤訊息了.
> ＃就是上面這一行，我code丟進去SPIM編輯時，就會出錯，執行結果當然也不對
> #不知道是不是我觀念不清楚 少寫什麼？
> addi $v0, $zero, 4
> syscall
> skip: sub $t0, $t0,1
> bltz $t0, fini
> lb $t5, digits($t0)
> j next
> # Pop the stack, return to SPIM
> fini: addi $sp, $sp, 4
> lw $ra, 0($sp)
> jr $ra
--
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