ArchitectureAssembler/12_StackSubroutines

Ñòåê è ïîäïðîãðàììû

1. Ñòåê:
   • Ñòåê
   • Ñòåê MIPS
     • 0x7FFF FFFF
     • ðàñòåò âíèç
   • Ðåãèñòð óêàçàòåëÿ ñòåêà

     •    1 # Evaluate the expression ab - 12a + 18b - 7
          2 #
          3 # Settings: Load delays OFF; Branch delays OFF,
          4 #           Trap file    ON; Pseudoinstructions ON
          5 
          6         .globl  main
          7 
          8 main:
          9         lw      $t0,a          # get a
         10         lw      $t1,bb         # get b
         11         mul     $t0,$t0,$t1    # a*b
         12         subu    $sp,$sp,4      # push a*b onto stack
         13         sw      $t0,($sp)
         14 
         15         lw      $t0,a          # get a
         16         li      $t1,-12        #
         17         mul     $t0,$t0,$t1    # -12a
         18         subu    $sp,$sp,4      # push -12a onto stack
         19         sw      $t0,($sp)
         20 
         21         lw      $t0,bb         # get b
         22         li      $t1,18         #
         23         mul     $t0,$t0,$t1    # 18b
         24         subu    $sp,$sp,4      # push 18b onto stack
         25         sw      $t0,($sp)
         26 
         27         li      $t1,-7         # init sum to -7
         28         lw      $t0,($sp)      # pop 18b
         29         addu    $sp,$sp,4
         30         addu    $t1,$t1,$t0    # 18b -7
         31 
         32         lw      $t0,($sp)      # pop -12a
         33         addu    $sp,$sp,4
         34         addu    $t1,$t1,$t0    # -12a + 18b -7
         35 
         36         lw      $t0,($sp)      # pop ab
         37         addu    $sp,$sp,4
         38         addu    $t1,$t1,$t0    # ab - 12a + 18b -7
         39 
         40 done:   li      $v0,1          # print sum
         41         move    $a0,$t1
         42         syscall
         43         li      $v0,10         # exit
         44         syscall
         45 
         46         .data
         47 a:      .word  0
         48 bb:     .word  10
       

   • Àïïàðàòíûé ñòåê
2. Ïîäïðîãðàììû:
   • ïîâòîðíîå èñïîëüçîâàíèå
   • ìîäóëüíîñòü
   • ïðîáëåìà âîçâðàòà
   • àïïàðàòíàÿ ïîääåðæêà:
     • èíñòðóêöèè - "jal" è "jr"("jalr")
     • îñîáàÿ ðîëü ðåãèñòðà $31($ra)
3. Êîíâåíöèè î âûçîâå:
   • âûçûâàþùèé è è âûçûâàåìûé
   • ïðàâèëà ñîõðàíåíèÿ è èñïîëüçîâàíèÿ ðåãèñòðîâ
4. Ïðîñòàÿ êîíå÷íàÿ ïîäïðîãðàììà:
   • Ïðîñòàÿ êîíâåíöèÿ î âûçîâå:
     1. Ïîäïðîãðàììà âûçûâàåòñÿ ñ ïîìîùüþ èíñòðóêöèè "jal"(êîòîðàÿ ñîõðàíèò îáðàòíûé àäðåñ â ðåãèñòðå $ra).
     2. Ïîäïðîãðàììà íå áóäåò âûçûâàòü äðóãóþ ïîäïðîãðàììó(êîíå÷íàÿ).
     3. Ïîäïðîãðàììà âîçâðàùàåò óïðàâëåíèå âûçûâàþùåé ïðîãðàììå ñ ïîìîùüþ èíñòðóêöèè "jr $rà".
     4. Ðåãèñòðû èñïîëüçóþòñÿ ñëåäóþùèì îáðàçîì:
        • $t0 - $t9 - ïîäïðîãðàììà ìîæåò èçìåíèòü ýòè ðåãèñòðû.
        • $s0 - $s7 - ïîäïðîãðàììà íå äîëæíû èçìåíÿòü ýòè ðåãèñòðû.
        • $à0 - $a3 - ýòè ðåãèñòðû ñîäåðæàò àðãóìåíòû äëÿ ïîäïðîãðàììû. Ïîäïðîãðàììà ìîæåò èçìåíèòü èõ.
        • $v0 - $v1 - ýòè ðåãèñòðû ñîäåðæàò çíà÷åíèÿ, âîçâðàùàåìûå èç ïîäïðîãðàììû.
     5. Îñíîâíàÿ ïðîãðàììà âîçâðàùàåò óïðàâëåíèå ñ ïîìîùüþ ñèñòåìíîãî âûçîâà(syscall) 10.

      1 # addthree.asm --- read in three integers and print their sum
      2 #
      3 # This program uses simple linkage.
      4 #
      5 # Settings: Load delays  ON;  Branch delays ON
      6 #           Trap file    ON;  Pseudoinstructions ON
      7 #
      8 
      9          .text
     10          .globl  main
     11 main:
     12          jal     pread            # read first integer
     13          nop                      #
     14          move    $s0,$v0          # save it in $s0
     15 
     16          jal     pread            # read second integer
     17          nop                      #
     18          move    $s1,$v0          # save it in $s1
     19 
     20          jal     pread            # read third integer
     21          nop                      #
     22          move    $s2,$v0          # save it in $s2
     23 
     24          addu    $s0,$s0,$s1      # compute the sum
     25          addu    $a0,$s0,$s2
     26 
     27          li      $v0,1            # print the sum
     28          syscall
     29 
     30          li      $v0,10           # exit
     31          syscall
     32 
     33 
     34 # pread -- prompt for and read an integer
     35 #
     36 # on entry:
     37 #    $ra -- return address
     38 #
     39 # on exit:
     40 #    $v0 -- the integer
     41 
     42          .text
     43          .globl  pread
     44 pread:
     45          la    $a0,prompt        # print string
     46          li    $v0,4             # service 4
     47          syscall
     48 
     49          li    $v0,5             # read int into $v0
     50          syscall                 # service 5
     51 
     52          jr    $ra               # return
     53          nop                     #
     54 
     55          .data
     56 prompt:
     57          .asciiz "Enter an integer: "