MIPS Assembler

students were asked to design a MIPS assembler as part of CSE 332 Fall 2016. Here is the documentation of one work and the code is attached below. Detail description of the project and some other notable works can be found here.

Introduction:

Our task was to design an assembler which will convert the assembly code(MIPS) to machine language.

Objective:

Our main goal was to generate a machine code from a file containing assembly language. The assembler reads a program written in an assembly language, then translate it into binary code and generates output file containing machine code.

How to use:

In the input file the user has to give some instructions to convert into machine codes. The system will convert valid MIPS instructions into machine language and generate those codes into output file.

Input File

The input file is located in a folder named “File”. User will write down the MIPS code in this file.

List of Tables

Register List

We have selected registers from $zero, $t0-$t7 and $s0-$s7 and assigned 5 bits for each of the register as we know in the instruction field in MIPS containing the register rs, rt and rd contains 5 bits.

R-Type Op-Code List

We have selected following op codes and assigned functionality values (6 bits) for each of the op codes as we know in the instruction field in MIPS, the functionality contains 6 bits.

I-Type List

We have selected following op codes and assigned functionality values (6 bits) for each of the op codes as we know in the instruction field in MIPS, the functionality contains 6 bits.

J-TYPE List

We have selected following op codes and assigned functionality values (6 bits) for each of the op codes as we know in the instruction field in MIPS, the functionality contains 6 bits.

Instruction Description

add: It adds two registers and stores the result in destination register.

· Operation: $d = $s + $t

· Syntax: add $d, $s, $t

sub: It subtracts two registers and stores the result in destination register.

· Operation: $d = $s - $t

· Syntax: sub $d, $s, $t

addi: It adds a value from register with an integer value and stores the result in destination register.

· Operation: $d = $s + offset

· Syntax: addi $d, $s, offset

lw: It loads required value from the memory and write it back into the register.

· Operation: $d = MEM[$s + offset]

· Syntax: lw $d, offset($s)

sw: It stores specific value from register to memory.

· Operation: MEM[$d + offset] = $s

· Syntax: sw $s, offset($d)

and: It AND’s two register values and stores the result in destination register. Basically, it sets some bits to 0.

· Operation: $d = $s && $t

· Syntax: and $d, $s, $t

or: It OR’s two register values and stores the result in destination register. Basically, it sets some bits to 1.

· Operation: $d=$s || $t

· Syntax: or $d, $s, $t

nor: It NOR’s two register values and stores the result in destination register. Sometimes we use nor to get NOT of register value.

· Operation: $d=$s nor $t

· Syntax: nor $d, $s, $t

andi: Bitwise AND’s a register and an immediate value and stores the result in a register.

· Operation: $d = $s AND offset

· Syntax: andi $d, $s, offset

ori: Bitwise ors a register and an immediate value and stores the result in a register.

· Operation: $d = $s OR offset

· Syntax: ori $d, $s, offset

sll: It shifts bits to the left and fill the empty bits with zeros. The shift amount is depended on the offset value.

· Operation: $d= $s << offset

· Syntax: sll $d, $s, offset

srl: It shifts bits to the right and fill the empty bits with zeros. The shift amount is depended on the offset value.

· Operation: $d= $s >> offset

· Syntax: srl $d, $s, offset

beq: It checks whether the values of two register s are same or not. If it’s same it performs the operation located in the address at offset value.

· Operation: if ($s==$t) jump to offset

else goto next line

· Syntax: beq $s, $t, offset

bne: It checks whether the values of two register s are same or not. If it’s not same it performs the operation located in the address at offset value.

· Operation: if ($s!=$t) jump to offset

else goto next line

· Syntax: bne $s, $t, offset

Slt: If $s is less than $t, $d is set to one. It gets zero otherwise.

· Operation: if $s < $t $d = 1

else $d = 0

· Syntax: slt $d, $s, $t

J: Jumps to the calculated address.

· Operation: PC = nPC

· Syntax: j target

jr: Jump to the address contained in register $s

· Operation: PC = nPC;

nPC = $s;

· Syntax: jr $s

Jal: Jumps to the calculated address and stores the return address in $31

· Operation: $31 = PC + 8 (or nPC + 4);

PC = nPC;

· Syntax: jal target

Limitation

The user has to give spaces between instruction words in the input file. If user don’t follow this format the system will show a valid code as invalid.

Troubleshooting

Please consider that our design uses both file and console I/O. To enable file I/O in code-blocks stdC++11 box in compiler setting should be checked.

Compiler setting can be found here: Settings > Compiler settings.