程序代写代做代考 mips Lab 3

Lab 3

CMPUT 229

University of Alberta

CMPUT 229 (University of Alberta) Lab 3 1 / 15

Outline

1 Lab 3 Assignment
The Assignment
Stack Management
Caller/Callee Conventions
Assignment Tips
Questions

CMPUT 229 (University of Alberta) Lab 3 2 / 15

Lab 3 Assignment The Assignment

The Assignment: CubeStats

Input:

corner in $a0 – the address of the top left corner of an n-dimensional
cube residing in an n-dimensional array.

edge in $a1 – the edge size of the cube.

n in $a2 – the number of dimensions.

size in $a3 – the total edge size of the array.

Output:

In $v0, a signed integer containing the range of the elements in the
specified cube.

In $v1, a signed integer containing the floor of the average of the
elements in the specified cube.

You may assume that the parameters are correct, and the cube is
contained in the base array.

CMPUT 229 (University of Alberta) Lab 3 3 / 15

Lab 3 Assignment The Assignment

A 1-Dimensional Example

A 1-D cube is just an array:

10
9
8
7
6
5
4
3
2
1

0x10001030

0x1000102C

0x10001028

0x10001024

0x10001020

0x1000101C

0x10001018

0x10001014

0x10001010

0x1000100C $a0

8($a0)

If your parameters were:

$a0 = 0x1000 100C

$a1 = 5

$a2 = 1

$a3 = 10

Then you would return:

$v0 = 4

$v1 = 3

CMPUT 229 (University of Alberta) Lab 3 4 / 15

Lab 3 Assignment The Assignment

A 2-Dimensional Example

A 2-D cube (with row-major storage)
looks like:

0x1000102C

0x10001028

0x10001024

0x10001020

0x1000101C

0x10001018

0x10001014

0x10001010

0x1000100C

$a0

1
4
7 8 9

2 3
5 6

9
8
7

6
5

3
2

If your parameters were:

$a0 = 0x1000 1010

$a1 = 2

$a2 = 2

$a3 = 3

Then you would return:

$v0 = 4

$v1 = 4

CMPUT 229 (University of Alberta) Lab 3 5 / 15

Lab 3 Assignment Stack Management

The Stack

To preserve data across subroutine calls, we use the stack.

The extent of the stack is defined by the stack pointer, $sp.

Each executing subroutine gets its own stack frame, which is
delimited by the frame pointer, $fp, and the stack pointer.

To grow the stack, you subtract from $sp.

To access data on the stack, you use $fp, since the offsets from $sp
might change if you grow the stack during your subroutine.

CMPUT 229 (University of Alberta) Lab 3 6 / 15

Lab 3 Assignment Stack Management

Stack Example

We are inside a subroutine, and need to call another subroutine.
Assume we have not used the stack yet.
We have a value we want to keep in $t0.
We also need to keep $ra so that we know how to return.
We must also keep $fp in case the caller was using it.

Before the call:

# Set up our frame
subu $sp , $sp , 4
sw $fp , 0( $sp )
move $fp , $sp
# Grow the s t a c k
subu $sp , $sp , 8
# Sto r e our v a l u e s
sw $ra , −4( $ fp )
sw $t0 , −8( $ fp )
# Now we can s a f e l y j a l
j a l some sub

After the call:

# Res to r e our v a l u e s
lw $ra , −4( $ fp )
lw $t0 , −8( $ fp )
# Unwind
addu $sp , $sp , 12
lw $fp , −4($sp )
j r $ ra

CMPUT 229 (University of Alberta) Lab 3 7 / 15

Lab 3 Assignment Stack Management

Stack Example

Before the call:

After the call:

# Res to r e our v a l u e s
lw $ra , −4( $ fp )
lw $t0 , −8( $ fp )
# Unwind
addu $sp , $sp , 12
lw $fp , −4($sp )
j r $ ra

CMPUT 229 (University of Alberta) Lab 3 7 / 15

Lab 3 Assignment Stack Management

Stack Example – Illustrated

$sp

CMPUT 229 (University of Alberta) Lab 3 8 / 15

Lab 3 Assignment Stack Management

Stack Example – Illustrated

# Set up our frame
subu $sp , $sp , 4
sw $fp , 0( $sp )
move $fp , $sp

$sp$fp $fp

CMPUT 229 (University of Alberta) Lab 3 9 / 15

Lab 3 Assignment Stack Management

Stack Example – Illustrated

# Set up our frame
subu $sp , $sp , 4
sw $fp , 0( $sp )
move $fp , $sp
# Grow the s t a c k
subu $sp , $sp , 8
# Sto r e our v a l u e s
sw $ra , −4( $ fp )
sw $t0 , −8( $ fp )

$sp

$fp $fp
$ra
$t0

CMPUT 229 (University of Alberta) Lab 3 10 / 15

Lab 3 Assignment Stack Management

Stack Example – Illustrated

# Set up our frame
subu $sp , $sp , 4
sw $fp , 0( $sp )
move $fp , $sp
# Grow the s t a c k
subu $sp , $sp , 8
# Sto r e our v a l u e s
sw $ra , −4( $ fp )
sw $t0 , −8( $ fp )
# Now we can s a f e l y j a l
j a l some sub
# Res to r e our v a l u e s
lw $ra , −4( $ fp )
lw $t0 , −8( $ fp )
# Unwind
addu $sp , $sp , 12

$sp

$fp $fp
$ra
$t0

CMPUT 229 (University of Alberta) Lab 3 11 / 15

Lab 3 Assignment Stack Management

Stack Example – Illustrated

$sp

$fp
$ra
$t0

CMPUT 229 (University of Alberta) Lab 3 12 / 15

Lab 3 Assignment Caller/Callee Conventions

Caller/Callee Conventions

In MIPS the following convention for calling subroutines applies:

When calling another routine, the caller or callee is responsible for
saving some registers.

MIPS does not save automatically these registers, it is the coder’s
responsability.

There are two types of registers: callee-saved and caller-saved.

Callee-saved ($s registers) must be restored to the same value they
had when the callee obtained control. This should always be done, as
the caller expects all the $s values untouched.

Caller-saved registers are the temporary registers $t. Programers
should use them freely as the caller is obliged to save them before
calling another routine.

CMPUT 229 (University of Alberta) Lab 3 13 / 15

Lab 3 Assignment Assignment Tips

Assignment Tips

Read specifications very carefully. Pay special attention to what you
have to include – we don’t want a main method.

Read and understand the main-row-first .c and .s files.

You are free to use the “power” subroutine from main-row-first.s

Adhere to the calling convention to avoid losing marks.

Test your assignments on the lab machines before you submit.

Look at the marksheet to get an idea of how the grading will be done.

Style marks are easy marks. Format your code like the example.s file
we provided, and write good comments.

Be sure to submit code that runs and loads. Otherwise you will lose
many marks.

CMPUT 229 (University of Alberta) Lab 3 14 / 15

Lab 3 Assignment Questions

Lab 3 Questions?

CMPUT 229 (University of Alberta) Lab 3 15 / 15

Lab 3 Assignment
The Assignment
Stack Management
Caller/Callee Conventions
Assignment Tips
Questions

Published by admin

Leave a Reply Cancel reply