addi $9, $zero, 0 addi $12, $zero, 5000 Loop: addi $12, $12, 4 lw $8, 40($12) ad

Question

addi $9, $zero, 0
addi $12, $zero, 5000
Loop: addi $12, $12, 4
lw $8, 40($12)
add $9, $9, $8
addi $11, $11, -1
bne $11, $zero, Loop


For the above MIPS program, determine the instruction format for the lw and bne instructions and the values of each instruction field. You may want to refer to the MIPS reference card available here: http://refcards.com/docs/waetzigj/mips/mipsref.pdf.

Also provide the binary and hex values for the complete instruction.

For example, for the instruction

lw $v1,0($a0),

the instruction format is I;
the instruction fields are op=2316 = 3510, rs=410, rt=310, imm=010;
the binary value of the instruction is therefore

100011 00100 00011 0000000000000000,

and the hex value is

0x8C830000

Explanation / Answer

I-type instruction format for lw:

          Opcode(6)

     rs(5)

rt(5)

      Immediate(16)

lw rt, immediate (rs)

lw $8, 40($12)

I-type instruction format for bne:

     Opcode(6)

         rs(6)

          rt(5)

16-bit address

bne rs, rt, Label      next instruction is at Label if rs !=rt

bne $11, $zero, Loop

          Opcode(6)

     rs(5)

rt(5)

      Immediate(16)

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