MIPS Assembly Language

Programming

CDA 3101 Discussion Session 04CDA 3101 Discussion Session 04

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Outline

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MIPS simulator – PCSpim

InstallationTry it with small programs !

PCSpim

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Installation• From the textbook CD• From the internet

http://www.cs.wisc.edu/~larus/spim.html

Writing A Basic Program

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Let’s start by writing a program that sums all the numbers between 1 and 5.

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

Writing A Basic Program

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Summing numbers between 1 and 5.Something… like this:

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

Writing A Basic Program

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

Writing A Basic Program

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum);

printf("\nEnd of Program\n"); }

# Our first test program for MIPS Simulator (pcSpim)

.data.disp1: .asciiz “Test Program #1\n”.disp2: .asciiz “Sum from 1 to 5 = “.disp3: .asciiz “\nEnd of program\n

.text #Tells us this is the code section.

.globl main #Tells compiler that this is a #public location (function)

main: … #The start of the function

Writing A Basic Program

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

…

main: li $t0, 0#int sum = 0;li $v0, 5 #int i = 5;

So we will be using $t0 as sum, and $v0 as i

Writing A Basic Program

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

…

main: li $t0, 0 #int sum = 0;li $v0, 5 #int i = 5;

#doloop: …

bgtz $v0, loop #while(i > 0);

To make a do … while loop, we will need a label to jump to. It’s really the old goto function.

Writing A Basic Program

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

…

main: li $t0, 0 #int sum = 0;li $v0, 5 #int i = 5;

#doloop: add $t0, $t0, $v0 #sum = sum + i;

addi $v0, $v0, -1 #i = i – 1;bgtz $v0, loop #while(i > 0);

Now we can perform the real work.

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How can we translate this into MIPS?

void main() { printf("Test Program #1\n");

int sum = 0; int i = 5; do { sum = sum + i; i = i - 1; } while( i > 0 );

printf("Sum from 1 to 5 = %d",sum); printf("\nEnd of Program\n"); }

main:li $v0,4la $a0,disp1syscallli $t0, 0 #int sum = 0;li $v0, 5 #int i = 5;

loop: add $t0, $t0, $v0 #sum = sum + i;addi $v0, $v0, -1 #i = i – 1;bgtz $v0, loop #while(i > 0);

li $v0,4la $a0,disp2syscall

li $v0,1move $a0,$t0syscall

li $v0,4la $a0,disp3syscall

li $v0,10syscall

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PC SpimPC Spim

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PC SpimPC Spim

• Note the top window – it contains the state of all registers.

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PC SpimPC Spim

• The button on the top right runs the program to its end, after you click “OK” on the dialog box. Note that you won’t see the register changes until the program ends.

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PC SpimPC Spim

• Click this menu item to reinitialize PC Spim – it’s like rebooting your computer. It’s often necessary to click Reload to run your program again.

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PC SpimPC Spim

• Click this menu item to change settings for the emulator.

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PC SpimPC Spim

• Click this menu item to change settings for the emulator.• Sometimes it’s helpful to uncheck “General registers in

hexadecimal” so that you can read values as regular numbers.

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PC SpimPC Spim

• Click the button that looks like a hand to set breakpoints. The program will stop running at positions you indicate, and wait for your authorization to continue upon reaching said point. You will also see the register values updated.