$7\mathrm{.}10$ LAB: Nested procedures

Given the following C program and the mapping of registers to variables, complete the RISC$-$V implementation of procedure Sum.

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

return b $-$ a;

$\}$

int Sum$($int m$,$ int n$\}\{$

int p $=$ Dif$($n$+1,$ m$-1)$;

int q $=$ Dif$($m$+1,$ n$-1)$;

return p $+$ q;

$\}$

int main$()\{$

int $\}\backslash$mp@subsup$\{\backslash$textrm$\{$x$\}\}\{,\}\{\}\backslash$textrm$\{$y$\}\backslash$mathrm$\{$ ;

z $=$ x $+$ y $+$ Sum$($x$,$ y$)$;

return $0$;

$\}$

Hints: Use stack memory as needed. Use x $10,$ x$11$ as arguments and x $12$ as return value, according to the convention for procedure calling.

Ex: If the values of x$8$ and x$9$ are initialized in the simulator as:

the result is stored in xx$18$ :

Note: Use the $\text{'}+\text{'}$ button under the Registers display to initialize register values for x$8$ and x$9.$

Given code:

lui x$2,1$

addi x$2,$ x$2,1904//$ Assume Stack memory starts at $6000.$ Do not modify.

$//$ Procedure Main $($Do not modify$)$

Main:

add x$10,$ x$0,$ x$8$

add x$11,$ x$0,$ x$9$

jal x$1,$ Sum

add x$18,$ x$9,$ x$8$

add x$18,$ x$18,$ x$12$

beq x$0,$ x$0,$ End

$//$ Procedure Sum

Sum:

$//$ Type your code here.

$//$ Procedure Dif $($Do not modify$)$

Dif:

sub x$12,$ x$11,$ x$10$

jalr x$0,0($x$1)$

End: