Y86 Disassembler

This is one of the first projects that we had to do at University, it certainly gave me a better perspective on how computers operate underneath the high-level code we write.

What is Y86?

The Y86 instruction set architecture (ISA) is a simplified version of the x86 architecture, commonly used in computer architecture courses to illustrate key concepts. It features a smaller set of instructions, registers, and addressing modes than x86, making it easier to learn and understand. For more information on Y86, please refer to the textbook “Computer Systems: A Programmer’s Perspective” by Randal E. Bryant and David R. O’Hallaron, which is the original source for the Y86 ISA.

Usage

To disassemble a Y86 machine code file, use the following command:

./y86-disassembler <input_file>

Replace <input_file> with the path to your Y86 machine code file.

Building

To compile the Y86 disassembler, you will need a C compiler such as gcc. Navigate to the directory containing the source code file y86disassembler.c and run the following command:

gcc -o y86-disassembler y86disassembler.c

This will create an executable file named y86-disassembler in the current directory.

Features

The Y86 Disassembler supports a wide range of Y86 instructions, including:

• Data Transfer: rrmovl, irmovl, rmmovl, mrmovl, pushl, popl
• Conditional Moves: cmovle, cmovl, cmove, cmovne, cmovge, cmovg
• Arithmetic/Logical Operations: addl, subl, andl, xorl
• Control Flow: jmp, jle, jl, je, jne, jge, jg, call, ret
• Miscellaneous: halt, nop

The disassembler correctly decodes register operands and immediate values, including displacements for memory operations.

Example

Here’s an example of Y86 machine code and its corresponding disassembled output:

Input (e.g., in a file named example.yo):

30F234120000
2001
00

Command:

./y86-disassembler example.yo

Output:

irmovl $4660, %edx
rrmovl %eax, %ecx
halt

(Note: The immediate value $4660 is the decimal representation of 0x1234.)