Weekly Note 6, DM18, Spring 2007

Lecture February 20

• Intel Pentium assembler programming.

Exercises March 1

• With the GAS examples as a starting point, implement your favorite O(n²) sorting algorithm (bubble sort, insertion sort or selection sort). From the examples, you can see how to handle start and finish, interfacing the operating system, and how to allocate space for a number of integers.

  Place data directly into the code and print the result (using repetitive calls to printf) after the sorting.

• With the factorial example as the starting point, implement the computation of the n'th Fibonacci number. Be careful with the stack discipline.

• Make a debug function (in assembler) which prints the contents of the registers. It is most convenient, when this debugging feature is used, that as little as possible must be written in the interesting part of the code (to be debuggged), so in this case, you may violate the call conventions.

• In Appel Chapter 6, there is an illustration of a stack frame. Here, the static link and local variables (which were omitted at the lecture) are placed between the arguments and the return address. One or both of these could in our architecture may be more naturally be placed after the return address instead of before.

  With Appel Chapter 6 as a starting point, discuss the following points:

  • Where should the static link point when calling a local function in ones own scope and a function further out, respectively. Remember recursive functions in this connection.
  • When using a variable defined in a scope further out, which code must the compiler generate in order to find this variable and where does the compiler find the necessary information to find out which code to generate?
  • What code must the compiler generate when a function is called such that static link will be set up correctly for the called function and how does the compiler find the necessary information to do this?

Announcements

• The second part of the exam project has been posed with a deadline of March 14 at 12:00. Note that the tiny expressions example gives you the basic structure of the various files which are involved. However, be sure to understand and rethink all parts of this little example. Not everything in this little example is appropriate for a real compiler as the one you will be making. In particular, you should structure your AST using about 5-10 typedefs.
• You can check the status of your project via the course home page. For instance, when you turn in a project part, you can verify that it has been received (allow for a little time for me to register this). You can also verify when your project has been registered as approved. You will need to use the e-mail address registered on the list of participants.