deliverable: stack limits
The weakest point of the A- implementation is the stupid computation of
stack limits, which are always assumed to equal 25. It would be much
nicer to compute the exact limit.
This improvement can be implemented by
only making changes to the file
emit.c.
Note that "struct CODE" in the file
tree.h
contains a field "int visited;" which may
be useful for this task.
You should create a new branch of your A- compiler:
$ svn cp group-X/joos/scanparse group-X/joos/stacklimits
$ svn ci -m "* Create new A- branch for stack limits deliverable"
Then, make your modifications, ensure that you compute the same stack limits as the A+ compiler for the class benchmarks, and add a README file describing your work and the changes you needed to make. You might also want to write small test programs. Your goal should be to convince us and convince yourselves that your solution is correct. It is fine to leave precise details to comments in the source code. Format your text in 80 column blocks for readability, and stick to the current JOOS programming style.
Make sure that you do not turn on optimization by passing -O to either the A- or A+ compilers. Otherwise, you might find that for some methods the A+ compiler computes a smaller stack limit than your A- compiler. The optimization phase occurs before the emit phase, and since optimization can eliminate some unnecessary stack operations, this can affect the emitted stack limit.
Your TA will use Subversion to look at your changes and run the class benchmarks and your test programs in order to evaluate you. Remember, multiple small test inputs are more useful than one big test input that attempts to cover all features; a combination of both is even better.
This deliverable is due by midnight on Friday of Week 10. It will count for 3.33% of your grade. Marks will be generously deducted for late submissions.