# CSCI 2500 Homework 2 Performance Calculations and Compiling into MIPS

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## Homework Specifications

In this second homework assignment, you will work on a mixture of textbook problems and C code.
First, start with some “warm-up” exercises, which you will not submit as part of this assignment.

In other words, do these “warm-up” exercises as practice and to prepare to work on the actual
problems you will submit for credit.

## Warm-Up Exercises (for Practice)

1. Textbook Problem 1.3
2. Textbook Problem 1.5
3. Textbook Problem 1.7
4. Textbook Problem 1.13 (all sub-parts)

## Homework Problems (to Submit for Credit)

Use whatever software you like to write your answers to the textbook problems below. You must
produce a PDF to submit for this assignment. Please name your PDF hw2.pdf. These will be

1. Textbook Problem 1.6
2. Textbook Problem 1.9 (all sub-parts)
3. Textbook Problem 1.12 (1.12.1 and 1.12.2 only)
4. Textbook Problem 1.14 (all sub-parts)

## Coding Problem (to Submit for Credit)

Write a C program to take as input (via stdin) a valid assignment statement in C and generate
MIPS assembly code to perform the given calculation(s). You can assume that each C variable
name is one lowercase letter (e.g., a, b, c, etc.) and of type int. Further, positive int constants
are also allowed as part of the given expression. For this assignment, you only need to support the
addition (+) and subtraction (-) operators.

Note that you should use isspace(), islower(), isdigit(), scanf(), etc. to parse the input.
The MIPS code you generate must make use of registers \$s0,\$s1,…,\$s7 to correspond to C variables and registers \$t0,\$t1,…\$t9 to correspond to any temporary variables you need. Variables
in MIPS should match those in C from left to right, meaning that the final result of the assignment
statement must end up in register \$s0.

You can assume that you will not need more than the specific MIPS registers listed here.
Make sure to use the proper I-format instruction when the operand is a constant. If the constant
happens to be the first operand of the very first addition or subtraction, use addition with a zero
register and this constant, as shown in one of the examples.

Below are a few example runs of your program. In the first example, register \$s0 corresponds to
C variable f, \$s1 corresponds to g, and \$s2 corresponds to h.
bash\$ ./a.out
Please enter a valid C assignment statement:
f = g + h – 42;
The MIPS pseudocode is:
bash\$ ./a.out
Please enter a valid C assignment statement:
x = q – 12 + j;
The MIPS pseudocode is:
bash\$ ./a.out
Please enter a valid C assignment statement:
t = 9 + s – 1;
The MIPS pseudocode is:
2
bash\$ ./a.out
Please enter a valid C assignment statement:
a = x – y + 13 + x – a;
The MIPS pseudocode is:
sub \$t0,\$s1,\$s2
sub \$s0,\$t2,\$s0
bash\$ ./a.out
Please enter a valid C assignment statement:
Woooo woooo woooo;
The MIPS pseudocode is:
Parsing error…

Be sure to match the above output formatting and ordering of operands exactly as shown (to ensure
full credit on Submitty).
Note that if an invalid input occurs, output fprintf( stderr, “Parsing error…\n” ) and
return with EXIT_FAILURE.

#### Submission Instructions

For this assignment, you will submit both your code and your PDF (i.e., hw2.pdf) with your
answers to the textbook problems to submit.

Before you submit your code, be sure that you have clearly commented your code (this should not
be an after-thought). Further, your code should have a clear and logical organization. In general,
each function should easily fit on a single screen and have a clear (and clearly documented) purpose.

Variable names and function names should be intuitive and meaningful. And use a consistent logical
method for indentation.