LabD1 : Translate Java class into MIPS (1)

#===================== JAVA =====================

public class Fraction

{

private int numerator;

private int denominator;

public Fraction(int numerator, int denominator)

{

this.numerator = numerator;

this.denominator = denominator;

}

public int getNumerator() { return this.numerator }

public int getDenomimator() { return this.denominator }

public void add(Fraction other)

{

this.numerator = this.numerator * other.denominator + this.denominator * other.numerator;

this.denominator = this.denominator * other.denominstor;

}
}

#==================== MIPS ==========================

LabD1.s

# keyword public in Java will be translated as .globl in MIPS

.globl Fraction

.globl getNumerator #  public 

.globl adding

.globl setNumerator

.globl setDenominator

.text

#----------------------------------------------

# -------- the property of the class and the constructor is translated here -------------

Fraction:

# Initialize the property of each class

addi $t0, $0, 0 # private int numerator

addi $t1, $0, 1 # private int numerator

# constructor with 2 params

# allocate 8 bytes in the heap memory and save the address of the first byte in $v0

addi $v0, $0, 9 # $v0 = 9 means allocate memory address and save it in $v0

addi $a0, $0, 8 # $a0 = 8 means # of bytes needed.

syscall

# why? a continious 8 bytes heap memory were allocated, first 4 bytes for int variable numerator,

# second 4 bytes for int variable denomerator

sw $t0, 0($v0)

sw $t1, 4($v0)

# store the attributes somewhere in memory and return a reference to where they are

jr $ra

#--------------getNumerator accessor -----------------------------

# what does this method do??

# it retrive the value saved in the first 4 bytes and return it in $v0

# why $a0???

# a.getNumerator() 

# get the instance addrss and retrive the first 4 bytes.

getNumerator:

lw $v0, 0($a0)  

jr $ra

# -------------- getDenominator access ------------------------------

getDenominator:

lw $v0, 4($a0)

jr $ra

# ---------------   add(Fraction other) -----------------------------

# 2 addresses is needed in this method

# the address of the source instance address, and the address of the param instance

# e.g. a.add(b)

adding:

lw $t0, 0($a0) # the numerator of the source instance

lw $t1, 4($a0) # the denominator of the source instance

lw $t2, 0($a1) # the numerator of the param instance

lw $t3, 4($a1) # the denominator of the param instance

# calculate the numerator

mult $t0, $t3

mflo $t4

mulf $t1, $t2

mflo $t5

add $t6, $t4, $t5

# calculate denominator

multi $t1, $t3

mflo $t7

# update the numerator with the new value

sw $t6, 0($a0)

sw $t7, 4($a0)

jr $ra

# ------------ setNumerator( int numerator )  ---------------

setNumerator:

lw $t0, 0($a0)

add $t0, $t0, $a1

sw $t0, 0($a0)

jr $ra

# ------------- setDenominator (int denominator ) ------------

setDenominator:

lw $t0, 4($a0)

add $t0, $t0, $a1

sw $t0, 4($a0)

jr $ra