Question
Mips Division with bitwise shifts is found nowhere other than algorithm, and your textbook answers are not yet filled in. Could you please set an example in Computer Organization & Design(4th): 3.7.3: "Write a MIPS assembly language program to calculate A divided by B, using the approach of Figure 3.11 using an iterator, steps, quotient, divisor and remainder."...... or any generic step bitwise divide code. We are lost here.
Explanation / Answer
.data GETA: .asciiz "Enter A " GETB: .asciiz "Enter B " QMSG: .asciiz "Q = " RMSG: .asciiz "R = " NL: .asciiz " " ERR: .asciiz "Divide by zero error " left: .word 1 right: .word 1 .text .globl main main: # Prompt for an integer A: divisor li $v0, 4 la $a0, GETA syscall # Read A from user li $v0, 5 syscall move $t0, $v0 # Prompt for an integer B: dividend li $v0, 4 la $a0, GETB syscall # Read B from user li $v0, 5 syscall move $a1, $v0 # Initialize quotient register to zero # Initialize left half of Divisor regisiter with divisor # Initialize remainder register with the dividend (right aligned) # 1. Remainder = Remainder - Divisor # Remainder >= 0 goto Step 2a. # Remainder < 0 goto Step 2b. # 2a. Shift quotient register to the left, setting rightmost bit to 1 # 2b. Restore the original value bu Remainder = Remainder + Divisor # Shift quotient register to the left setting new LSB to zero # 3. Shift divisor register to the right 1 bit # < 33 repitions, goto step 1 # >= 33 repititions, print result # # Register usage: # $a0 = divisor # $a1 = dividend # $a2 = quotient # $a3 = remainder # $t4 = counter of 33 repetitions # $t0 = divisor (temp) initialize: li $a2, 0 # $a2 = quotient = 0 swl $t0, left lwl $a0, left # $a0 = left half of divisor swr $a1, right lwr $a3, right # $a3 = remainder = $a2 li $t4, 33 # $t4 = counter = 33 step_one: sub $a3, $a3, $a0 bge $a3, $zero, step_two_a blt $a3, $zero, step_two_b step_two_a: #slt $a2, $zero, $a2 sll $a2, $a2, 1 ori $a2, $a2, 1 j step_three step_two_b: add $a3, $a3, $a0 sll $a2, $a2, 1 step_three: sra $a0, $a0, 1 step_four: addi $t4, $t4, -1 bge $t4, $zero, step_one beq $t4, $zero, print_result print_result: li $v0, 4 la $a0, QMSG syscall move $a0, $a2 li $v0, 1 syscall li $v0, 4 la $a0, NL syscall li $v0, 4 la $a0, RMSG syscall move $a0, $a3 li $v0, 1 syscall li $v0, 4 la $a0, NL syscall j exit_program exit_program: li $v0, 10 syscall