Homework Assignment 2
                               CS 350c

                         Unique Number: 52140
                             Spring, 2017

                       Given:  January 24, 2017
                        Due:  February 2, 2017

This homework concerns the differences in the output of the compiler
when used on different optimization settings.

As for homework #1, the code below defines the original
tak function taken from the Wikipedia page (just
referenced):  https://en.wikipedia.org/wiki/Tak_(function)

    unsigned long int tarai( unsigned long int x,
                             unsigned long int y,
                             unsigned long int z )
    {
      if (y < x)
        return tarai( tarai( x-1, y, z ),
                      tarai( y-1, z, x ),
                      tarai( z-1, x, y ));
      else return y;
    }

You are to compile a C version of the algorithm (given just above)
using the "gcc" compiler available on the UTCS Departmental computers
with the following commands:

    gcc -O2 -c -S tarai.c
    mv tarai.s tarai-O2.s

    gcc -O3 -c -S tarai.c
    mv tarai.s tarai-O3.s


When "gcc" is called with the "-O3" optimization level, the number of
x86 instructions produced is more than 10 times as many as with the
"-O2" optimization level.

Below are the questions that you are asked to answer as a part of this
assignment:

1. What has the "gcc" compiler done to the optimization level "-O3"
   code as compared to the optimization level "-O2" code?  Please
   explain what you believe the compiler is doing.

2. Given these two levels of optimization, what is the difference in
   execution performance?

3. Can you justify the generation of so much code when the "-O3"
   setting is selected?

4. Extra Credit: If you have access to an up-to-date (meaning the,
   software) Apple Macintosh or a FreeBSD system or any system using
   the Clang/LLVM compiler toolsuite for compiling C-language
   programs, perform the commands above and compare the size of the
   code to the size of the code produced on a UTCS computer.