################################################################################
##
## LSU EE 4720 Fall 2005 Homework 3
##
##
## Due Wednesday, 12 October 2005
# Note: This version does not have comments in the pack routine.
# A version with comments will be posted Thursday evening or Friday
# morning, either version can be used for your solution.
.data
name:
.asciiz "" # Put your name between the quotes.
## Instructions:
#
# (0) Read and follow account setup instructions at
# http://www.ece.lsu.edu/ee4720/proc.html
#
# (1) Copy this assignment, local path name
# /home/classes/ee4720/com/s/hw3.s, to a directory ~/hw in your
# class account. (~ is your home directory.) Use this file for your
# solution. The TA-bot will look first for a file named ~/hw/hw3.s.
# If you have multiple versions make sure the one you want graded
# is in ~/hw/hw3.s.
#
# (2) Find the problem in this file and solve it.
#
# A procedure shell has been provided for the each problem. Place
# your solution there.
#
# Assembler code following the problems runs your solutions.
# That code can be modified.
#
# Your entire solution should be in this file.
#
# Do not rename the line labels in this file and be sure to use the
# directory and filename given above. (Line labels may be added.)
#
# (3) Your solution will automatically be copied from your account by
# the TA-bot. Late submissions can be E-mailed.
#
## Additional Resources
#
# MIPS Architecture Manual Volume 2 (Contains a list of instructions.)
# http://www.ece.lsu.edu/ee4720/mips32v2.pdf
# Note: SPIM implements MIPS-I instructions.
#
# SPIM Documentation:
# Appendix A of Patterson and Hennessey.
# http://www.ece.lsu.edu/3755/spim.pdf
#
# Account Setup and Emacs (Text Editor) Instructions
# http://www.ece.lsu.edu/ee4720/proc.html
# To learn Emacs look for and follow instructions for the Emacs tutorial.
#
# Unix Help
# http://www.ece.lsu.edu/v/4ltrwrd/
## Note on SPIM
#
# Clicking the close button (usually the upper-right-hand button on
# the window frame) of any window will immediately exit SPIM.
#
## Troubleshooting
#
# Make sure that the "run" dialog box shows 0x0400000 for the starting
# address. If not, __start was not properly defined, possibly due to
# an error before __start.
#
# Check the messages (bottommost) pane for syntax and other errors. It
# may be necessary to shorten other panes to make the messages pane visible.
# Common syntax errors include using "addi" instead of "add", or vice versa.
# Another common error is mistyping a label in a branch or jump target.
#
# Check the "Text Segments" pane to make sure all of your program is there.
# If not, there may have been an error reading the program.
#
# If your program fails a test or otherwise does not produce the
# expected output modify the test code so that the particular test it
# fails comes first (if it's not already). Then, single-step the code
# (using the "step") button until you find the problem.
#
# If you've hit a wall ask the TA or instructor help. It's better to
# err on the side of too many questions than too few.
################################################################################
## Problem 0
# Do the setup described in the instructions above.
#
# Before making any changes to this file (other than comments) run
# the assembler/simulator SPIM using the following steps:
#
# Load this file into an Emacs buffer using the class-account Emacs.
#
# If setup was done correctly comments should be red, "Problem 0" above
# should be in a black, bold, sans-serif font and the assembler below
# should look something like fruit salad, with pale blue mnemonics,
# italicized pseudo instructions, purple assembler directives, green
# line labels, etc.
#
# Start the SPIM assembler/simulator by pressing [F9].
# -> A window entitled "xspim" should pop up. The top pane should show
# register values, the next pane should have buttons, the third
# should show the program in binary and assembler forms, the fourth
# pane shows the data area, and the bottom pane (which might extend
# past the bottom of the screen) shows messages.
#
# Run the program by clicking the "run" button then clicking "ok" on the
# dialog box that pops up.
# -> A window entitled "SPIM Console" should pop up, the window
# should be asking you to include your name in this file. After
# a name is entered and Spim is re-run it should show four wrong
# conversions (for Problem 1). For Problem 0 that's success!!!
#
# Put your name at the top of the file then run the code in this
# file.
# -> The output window of the simulator (which might be hidden
# behind the main window) should show that the output of the unpack
# routine is "Not yet implemented." and is not the correct output.
################################################################################
## Problem 1 -- Unpack Routine
# The unpack routine below unpacks every string into "Not yet
# implemented", which of course can't be right. Modify the routine so
# that it unpacks correctly. Follow the guidelines below next to the
# check boxes ([ ]).
## Register Usage
#
# $a0: Procedure call argument. Address of packed string.
# $a1: Procedure call argument. Address of memory for unpacked string.
# There are no return values.
# [ ] Make sure that the code at least runs to completion.
# Substantial credit will be deducted for syntax
# and run-time errors.
# [ ] Make sure the code passes the test in the demo routine
# and works for other strings too. The unpack routine may be
# graded using different strings.
#
# [ ] Registers $t0-$t9 and $a0-$a3 can be used.
# [ ] Fill as many delay slots as possible.
# [ ] The only pseudo instructions that can be used are "nop" and "la".
# [ ] The code should be reasonable efficient,
# don't use two instructions where one would do.
.data
NYI:
.asciiz "Not yet implemented."
.text
unpack:
la $t0, NYI
ULOOP:
lb $t1, 0($t0)
addi $t0, $t0, 1
sb $t1, 0($a1)
bne $t1, $0, ULOOP
addi $a1, $a1, 1
jr $ra
nop
################################################################################
## Demonstration Routine
# This routine calls the pack and unpack routines on a sample
# string below (DEMO_STRING), displays the original and unpacked strings
# side by side, and verifies whether the unpacked string is correct.
# It's okay to change DEMO_STRING if that will help you debug your code,
# but your code should work on the original DEMO_STRING and any other
# string.
.data # Indicate to the assembler that the stuff below is data.
#
# String to demonstrate pack and unpack routines.
#
DEMO_STRING: # Address of stuff immediately following.
# Place string in memory here, end string with NULL (0).
.asciiz ".,!Time flies like an arrow, fruit flies like a banana. azAZ09"
.byte 0, 0, 0 # Put three zeros in memory here.
#
# Memory space for packed and unpacked strings.
#
.align 4 # Make sure the address below is a multiple of 4.
BUFFER_PACK:
.space 256 # Allocate 256 characters for use by the pack routine.
.align 4
BUFFER_UNPACK:
.space 256 # Allocate 256 characters for use by the unpack routine.
#
# Message printed by the demonstration routine.
#
MSG:
.asciiz "Original:\n\"%/a2/s\"\nUnpacked: \n\"%/a1/s\"\n"
MSGSPACES:
.asciiz " "
MSGERROR:
.asciiz "%/s4/s |<---- First error here."
MSGCORRECT:
.asciiz "Unpack appears correct."
#
# Message displayed if name omitted.
#
who_are_you:
.asciiz "Please put your name at the top of the file where indicated."
.text # Indicate to the assembler that the stuff below is code.
.globl __start
__start:
la $s0, name
lb $s0, ($s0)
bne $s0, $0, DOTESTS
la $a0, who_are_you
addi $v0, $0, 11
syscall
addi $v0, $0, 10
syscall
DOTESTS:
# Load address of string and address of memory for packed
# string and call the pack routine.
#
la $a0, DEMO_STRING
la $a1, BUFFER_PACK
jal pack
nop
# Load address of packed string and address of memory for unpacked
# string and call the unpack routine.
#
la $a0, BUFFER_PACK
la $a1, BUFFER_UNPACK
jal unpack
nop
# Call a system (simulator) routine to display results.
#
la $a0, MSG
la $a1, BUFFER_UNPACK
la $a2, DEMO_STRING
addi $v0, $0, 11
syscall
la $s0, DEMO_STRING
la $s1, LUT
la $s2, BUFFER_UNPACK
DVLOOP:
lb $t0, 0($s0)
beq $t0, $0 DVDONEOKAY
add $t1, $s1, $t0
lb $t1, 0($t1)
lb $t2, 0($s2)
bne $t1, $0 DCHAR
addi $s0, $s0, 1
addi $t0, $0, 46 # '.'
DCHAR:
beq $t0, $t2, DVLOOP
addi $s2, $s2, 1
la $s3, DEMO_STRING
sub $s3, $s0, $s3
la $s4, MSGERROR
sub $s4, $s4, $s3
la $a0, MSGERROR
j DVDONE
nop
DVDONEOKAY:
la $a0, MSGCORRECT
DVDONE:
addi $v0, $0, 11
syscall
addi $v0, $0, 10
syscall
nop
################################################################################
## Pack Routine
## Register Usage
#
# $a0: Procedure call argument. Address of string to pack.
# $a1: Procedure call argument. Address of memory for packed string.
# There are no return values.
.data
.align 4
LUT:
.space 256
KEEP:
.asciiz ".,!?;abcdefghijklmnopqrstuvwxyz "
.byte 0 # HINT, needed for solution to last part. <---- HINT!!
.text
pack:
#
## Section
#
la $t0, LUT
addi $t2, $t0, 252
PLOOP1:
sw $0, 0($t0)
bne $t0, $t2, PLOOP1
addi $t0, $t0, 4
#
## Section
#
la $t0, LUT
la $t1, KEEP
addi $t3, $0, 0
PLOOP2:
lbu $t2, 0($t1)
add $t4, $t0, $t2
sb $t3, 0($t4)
addi $t1, $t1, 1
bne $t2, $0 PLOOP2
addi $t3, $t3, 1
addi $t3, $0, -1
sb $t3, 0($t0)
#
## Section
#
PLOOP:
lbu $t4, 0($a0)
add $t1, $t0, $t4
lb $t2, 0($t1)
add $t5, $t2, $0
lbu $t4, 1($a0)
add $t1, $t0, $t4
lb $t3, 0($t1)
or $t5, $t5, $t3
sll $t3, $t3, 5
or $t2, $t2, $t3
lbu $t4, 2($a0)
add $t1, $t0, $t4
lb $t3, 0($t1)
or $t5, $t5, $t3
sll $t3, $t3, 10
or $t2, $t2, $t3
sh $t2, 0($a1)
addi $a1, $a1, 2
bgez $t5 PLOOP
addi $a0, $a0, 3
#
## Section
#
ori $t2, $t2, 0x8000
jr $ra
sh $t2, -2($a1)