[Project 3 is due on Monday, 12/16]
Problem: Using the SSA form generated in Project 2, implement one of the following SSA-based optimizations, and compare the performance of the generated optimized code with the unoptimized one (either using the tests provided or your own pattern-directed tests).
- Constant Propagation and Folding
- Copy Propagation
- Dead Code Elimination
The performance of the generated code can be evaluated using the MARS MIPS simulator. Submit a short report highlighting your findings.
Note: To keep things simple, we would not have any function exceeding 4 arguments.
Source code: The starting source code is located here. To compile the code, use the following command:
Running our compiler: For compiling a test (say test1.cmm), use the following command:
Tests: The new tests are located here.
Running the generated code: Invoke “spim” and use the following commands to run the generated code (say, test1.s):
(spim) load "test1.s"
In order to run another program (say, test2.s) in the same spim session, use the following command:
(spim) load "test2.s"
Measuring performance: In order to evaluate the performance of the generated code, we will use dynamic instruction count as a metric. Here are some guidelines for using MARS for that purpose:
- Copy Mars4_4.jar from this folder.
- Run the following command to invoke the tool: java -jar Mars4_4.jar
- Open a generated assembly code (e.g. test4.s) by pressing Ctrl+o.
- Press F3 to load the program.
- Invoke Instruction Counter from the Tools menu and press Connect to MIPS.
- Press F5 to run the program. You can enter any required inputs through the Run I/O box.
- The dynamic instruction count can be noted down from the Instruction Counter window.
Here is a snapshot of the tool in action:
Debugging clues: You will find a number of auxiliary files generated along with the final assembly code (*.s). For example in the factorial example (test2.cmm), here are some of the files generated to better understand the compilation of the factorial function:
- fact.dot: For visualization of the fact() CFG
- UseDef_fact.txt: Def and use sites for every variable in the fact() symbol table.
- test2.ir: Dump of the intermediate representation for the whole program.
- IG_fact_colored.dot: Colored interference graph for fact()
- register_mapping_fact.txt: Variable to register mapping for fact()
- test2.s: Final generated code.
The call frame layout used in our CCMM compiler is as follows (please refer to CallStackFrame.h):
Submitting to provide:
provide comp181 project3 <file1> [<file2> [<file3> ...]]