ECE 3504 Project 1 Fall 2021 Total points: 100 Version: 1 (Any updates will be announced on Canvas.) Deadline: Wednesday October 13th at 11:59 PM Late Policy: Projects have strict deadlines and have to be digitally submitted at 11:59 PM on the day they are due. If submitted before 2 AM the next day, a 5% reduction in grade will apply and the project will still be accepted. If submitted by 11:59 PM on the day after the due date, a 20% reduction in grade will be applied and the project will still be accepted. No project will be accepted after that point without a letter from Dean’s Office. In order for your projects to be accepted, you need to complete the submission process. Uploading files but not making them available to the instructor, submitting the wrong version, and other technical or non-technical issues do not make you eligible for a late submission. Note 1: For this project, we will use Moss, a tool developed by Stanford University to detect similarities in code structure across submissions. Moss cannot be defeated by changes to variable and function names, function ordering, formatting changes, and comments. Any strong similarities flagged by Moss will be carefully examined and possibly submitted to the Office of Undergraduate Academic Integrity. Note 2: For the sake of making it easy for the TA to compile and run your source code, you must provide build instructions with your submission. For this project you are allowed to use standard libraries. Project Description: Build a MIPS core instruction disassembler using a programming language of your choice. A disassembler reads the binary (formatted as hexadecimal) instructions executed by a MIPS processor and converts them to symbolic assembly source code read and written by people. Manual disassembly is very tedious and error prone, so it makes sense to write a disassembler program. The input to the disassembler is a text file named *.obj, where * is the name of a machine code file in the same folder as the disassembler executable. The output of the disassembler is another text file called *.s (same name but different extension). The executable will be named myDisassembler and is called from the console as follows: myDisassembler *.obj 2 This command will have myDisassembler read *.obj and generate *.s. If there is an existing *.s file simply overwrite it. Your grade will be mostly based on the correctness of the code in the output file *.s. You can use the console to print out messages for debugging purposes. The myDisassembler requirements are: • The input of myDisassembler is a text file containing MIPS machine code. Each line contains a 32-bit instruction encoded as 8 hexadecimal digits without a leading “0x”. Since object code is relocatable you don’t really need to know the absolute addresses of the instructions. • The output of myDisassembler is a text file containing one line per instruction. Each line will contain the MIPS assembly language corresponding to the object code, possibly preceded by a label on the previous line if and only if that instruction is the target of a branch instruction. • myDisassembler should be able to disassemble all the instructions in the core instruction set with the exception of j, jal, and jr instructions. The core instructions are summarized in the top left table of the MIPS reference card, also known as the Green Card. • In the case of bne and beq instructions, a label should be generated with a format “Addr_####:” where “####” is the address (rather than the relative offset) of the branch target, expressed in hexadecimal, starting at 0000 and incremented by 0004 after each instruction. The label also needs to be generated for the instruction at that address. The simplest way to do this is by taking two passes over the object code. The first pass looks for branch instructions and records the addresses of all branch targets in a list. The second pass uses this list to generate labels at the beginning of any instruction that is the target of a branch instruction. At most one label should appear on any instruction even if the label is referenced by more than one branch instruction. • myDisassembler should read a line at a time and print an error message to the command line for each line of the machine code file that contains an error. In other words, myDisassembler should report all errors found in an input file with error messages to the command line and then exit without producing an output file. The error checking can be done on the first pass. Examples of errors are: lines that don’t contain 8 hexadecimal digits, or encountering an instruction that cannot be disassembled. The error message should say “Cannot disassemble

at line ”.