UMBC CMSC431, Compiler Design Principles, Fall 2009

Project 4

Due: Monday, October 26, 2009, 12:00pm (noon)

Objective

This project continues to expand the features available in your programming language. You will add conditional statements and control structures to your language.

Assignment

Add the following features to your programming language:

A Boolean type for variables and Boolean constants for true and false.
Boolean operations (and, or, not).
Relational operators (less than, less than or equal to, equals, not equals, greater than or equal to, greater than) for integer and floating point expressions.
If statements.
While loops.

Implementation Notes

For simplicity, just use 4 bytes to hold a Boolean value.
Since we are using signed integers, you want to use the "signed" jump instructions. For example, use JG (jump greater than) instead of JA (jump above).
For simplicity, specify "near jumps" for all of your branching.
For floating point comparisons, look at double5.asm and double5.txt. Explanations for this is in Section 8.3.6 of the IA-32 Intel Architecture Software Developer's Manual.
Generating labels for the assembly language program for if statements and while loops require some care. Your compiler must allow for an arbitrary number of nested if statements and an arbitrary number of nested while loops.
You might find it useful to have mid-rule actions in your yacc file. ( Hint, hint.) This is explained in Section 3.5.5 of the Bison Book and in the "Embedded Actions" sections of the Flex and Bison book (p. 143).
When you invent a new grammar for if statements and while loops, keep in mind that bison cannot parse everything. In the following example from the flex and bison book (p. 50), we have: It is not possible for Bison to generate a parser that can determine whether HORSE should reduce to cart_animal or to work_animal because that depends on whether "phrase" expands to "cart_animal AND CART" or "work_animal AND PLOW". The LALR(1) parser that Bison generates cannot look past AND to see if "phrase" ended with CART or PLOW. (Note: this grammar is not ambiguous.)

Submitting Your Project

We will use a new repository for Project 4. You should first use CVS to check-out Project 4. cvs -d /afs/umbc.edu/users/c/h/chang/pub/cs431f09/Proj4 checkout -d MyProj4 user1 Then, use cvs add and cvs commit to check-in any files that you have copied over from Project 3 (and any other files that you want to submit). Since your programming language is looking more like a real programming language and less like a calculator, this is a good time to rename your expr.l and expr.y files.

Include in your submission some test programs that demonstrate your implementation of Boolean expressions, if statements and while loops. Your test programs should show that your compiler can handle multiply nested if statements and while loops.

Last Modified: 13 Oct 2009 00:17:26 EDT by Richard Chang

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