$59\mathrm{.}9$ LAB: Function calls

Given the following C program and the mapping of registers to variables, complete the MIPSzy implementation of Main. Do not implement return $0$ ; in main$().$

$```$

int Dif$($int a$,$ int b$)\{$

return a $-$ b;

$\}$

int Sum$($int a$,$ int b$)\{$

return a $+$ b;

$\}$

int main$()\{$

int x$,$ y;

w $=$ Sum$($x$,$ y$)$;

z$=$Dif$($y$,$ x$)$;

return $0$; $//$ Do not implement

$\}$

$```$

Hints: Use program stack to pass arguments, return values, and preserve saved registers. Remember to pop the stack after each function returns.

Ex: If the values of $\backslash (\backslash$$ t $0\backslash )$ and $\backslash (\backslash$$ $11\backslash )$ are initialized in the simulator as:

$\backslash$begin$\{$tabular$\}\{|$c$|$c$|\}$

$\backslash$hline Registers & Data $\backslash \backslash$

$\backslash$hline St$0$ & $5\backslash \backslash$

$\backslash$hline $\backslash$$t$1$ & $10\backslash \backslash$

$\backslash$hline

$\backslash$end$\{$tabular$\}$

the results are stored in St $2$ and $\backslash (\backslash$$ $\backslash$mathrm$\{$t$\}3\backslash )$ :

$\backslash$begin$\{$tabular$\}\{|$c$|$c$|\}$

$\backslash$hline Registers & Data $\backslash \backslash$

$\backslash$hline $\backslash$$t$0$ & $5\backslash \backslash$

$\backslash$hline$\backslash (\backslash$$ $\backslash$mathbf$\{$t $1\}\backslash )$ & $10\backslash \backslash$

$\backslash$hline $\backslash (\backslash$mathbf$\{\backslash$$ t $2\}\backslash )$ & $\backslash (\backslash$mathbf$\{15\}\backslash )\backslash \backslash$

$\backslash$hline $\backslash (\backslash$mathbf$\{\backslash$$ t $3\}\backslash )$ & $\backslash (\backslash$mathbf$\{5\}\backslash )\backslash \backslash$

$\backslash$hline

$\backslash$end$\{$tabular$\}$

Note: Use the $\text{'}+\text{'}$ button under the Registers display to initialize register values for $\backslash$$t$0$ and St$1.$

$\backslash$begin$\{$tabular$\}\{|$c$|$c$|$c$|\}$

$\backslash$hline $\backslash$multicolumn$\{3\}\{|$l$|\}\{$Line $1$ pddi $\backslash$$sp$,\backslash$$zero, $8188\backslash$# Assume progri$\}\backslash \backslash$

$\backslash$hline Line $2$ & & $\backslash \backslash$

$\backslash$hline Line $3$ & $\backslash$# Procedure Main & $\backslash \backslash$

$\backslash$hline Line $4$ & Main: & $\backslash \backslash$

$\backslash$hline Line $5$ & $\backslash$# Type your code h & here. $\backslash \backslash$

$\backslash$hline Line $6$ & & $\backslash \backslash$

$\backslash$hline Line $7$ & & $\backslash \backslash$

$\backslash$hline Line $8$ & $\backslash ($ j $\backslash )$ End & $\backslash \backslash$

$\backslash$hline Line $9$ & & $\backslash \backslash$

$\backslash$hline $\backslash$multicolumn$\{3\}\{|$l$|\}\{$Line $10\backslash$# Procedure Sum $($Do not modify$)\}\backslash \backslash$

$\backslash$hline Line $11$ & Sum: & $\backslash \backslash$

$\backslash$hline Line $12$ & Iw $\backslash$$t$0,8(\backslash$$sp$)$ & $\backslash \backslash$

$\backslash$hline Line $13$ & lw $\backslash$$t$1,4(\backslash$$sp$)$ & $\backslash \backslash$

$\backslash$hline Line $14$ & add $\backslash$$t$2.\backslash$$t$0.\backslash$$t$1$ & $\backslash \backslash$

$\backslash$hline

$\backslash$end$\{$tabular$\}$

Line $14$

add $\backslash (\backslash$$ $\backslash$mathrm$\{$t$ $\backslash$mathrm$\{$t$\}\backslash$theta$,\backslash$$ $\backslash$mathrm$\{$tl$\}\backslash )$

Line $15$

sw $\backslash$$t$2,0(\backslash$$sp$)$

Line $16$

jr $\backslash$$ra

Line $17$

Line $18\backslash$# Procedure Dif $($Do not modify$)$

Line $19$ Dif:

Line $20$ Iw $\backslash$$t$0,8(\backslash$$sp$)$

Line $21$ lw $\backslash$$t$1,4(\backslash$$sp$)$

Line $22$ sub $\backslash (\backslash$$ t $2,\backslash$$ t $0,\backslash$$ $\backslash )$ t$1$

Line $23$

Line $24$

sw $\backslash$$t$2,0(\backslash$$sp$)$

Line $25$

jr $\backslash$$ra

Line $26$ End:

Line $27$