Assembler Assembler Ein greres Beispiel Prof. Dr. Peter Trommler - PowerPoint PPT Presentation

Assembler Assembler Ein größeres Beispiel Prof. Dr. Peter Trommler

Prozedur zum Tauschen Prozedur zum Tauschen void swap(int *a, int *b) { int t = *a; *a = *b; *b = t; return; } 2 Prof. Dr. P. Trommler

Bubblesort Bubblesort void sort(int *a, int size) { int swapped, i; do { swapped = 0; for(i=0; i<size; i++) if (a[i] > a[i+1]) { swap(&a[i], &a[i+1]); swapped = 1; } } while (swapped); return; } 3 Prof. Dr. P. Trommler

Do-While-Schleife Do-While-Schleife or $s2,$a0,$zero # save a or $s3,$a1,$zero # save size doloop: or $s0,$zero,$zero # swapped = false ... bne $s0,$zero,doloop# end do while 4 Prof. Dr. P. Trommler

For-Schleife For-Schleife or $s2,$a0,$zero # save a or $s3,$a1,$zero # save size doloop: or $s0,$zero,$zero # swapped = false or $s1,$zero,$zero # i=0 (init for) for: slt $t2,$s1,$s3 # i<size? beq $t2,$zero,endfor # for ends ... addiu $s1,$s1,1 # i++ j for # end of for loop endfor: bne $s0,$zero,doloop # end do while 5 Prof. Dr. P. Trommler

If-Abfrage If-Abfrage or $s2,$a0,$zero # save a or $s3,$a1,$zero # save size doloop: or $s0,$zero,$zero # swapped = false or $s1,$zero,$zero # i=0 (init for) for: slt $t2,$s1,$s3 # i<size? beq $t2,$zero,endfor # for ends addu $a0,$zero,$s1 sll $a0,$a0,2 # offset (i*4) addu $a0,$a0,$s2 # address of a[i] addi $a1,$a0,4 # address of a[i+1] lw $t0,0($a0) # a[i] lw $t1,0($a1) # a[i+1] slt $t2,$t1,$t0 # a[i+1]<a[i]? bne $t2,$zero,endif # on false skip ... endif: addiu $s1,$s1,1 # i++ j for # end of for loop endfor: bne $s0,$zero,doloop # end do while 6 Prof. Dr. P. Trommler

Funktionsaufruf Funktionsaufruf or $s2,$a0,$zero # save a or $s3,$a1,$zero # save size doloop: or $s0,$zero,$zero # swapped = false or $s1,$zero,$zero # i=0 (init for) for: slt $t2,$s1,$s3 # i<size? beq $t2,$zero,endfor # for ends addu $a0,$zero,$s1 sll $a0,$a0,2 # offset (i*4) addu $a0,$a0,$s2 # address of a[i] addi $a1,$a0,4 # address of a[i+1] lw $t0,0($a0) # a[i] lw $t1,0($a1) # a[i+1] slt $t2,$t1,$t0 # a[i+1]<a[i]? bne $t2,$zero,endif # on false skip jal swap # swap elements ori $s0,$zero,1 # swapped = true endif: addiu $s1,$s1,1 # i++ j for # end of for loop bne $s0,$zero,doloop # end do while 7 Prof. Dr. P. Trommler

Stackbehandlung Stackbehandlung addi $sp,$sp,-20 # 5 registers (s0-s3 and ra) sw $s0,0($sp) #save registers on stack sw $s1,4($sp) sw $s2,8($sp) sw $s3,12($sp) sw $ra,16($sp) ... # bubblesort code lw $s0,0($sp) # restore registers lw $s1,4($sp) lw $s2,8($sp) lw $s3,12($sp) lw $ra,16($sp) addi $sp,$sp,20 jr $ra # return 8 Prof. Dr. P. Trommler