Java-x86 Compiler

This repository contains our implementation of JAVA prototype compiler. This was implemented as project in the course CS335A : Compiler Design in the academic session 2022-23-II at IIT Kanpur.

Features Supported

The following features are supported by our implementation of the compiler:

• Primitive Data types such as int, byte, long, short
• Multidimensional Arrays (upto 3 dimensions)
• Basic operators such as
• Arithmetic Operators : +,-,*,/,%
• Pre-Post Increment/Decrement
• Relational Operators : >,<,>=,<=,==,!=
• Bitwise Operators : &, |, ^, ~, <<, >>, >>>
• Logical Operators : &&, ||, !
• Assignment Operators (including shorthand notation)
• Ternary Operator
• Control-flow via if-else statements, for loops, while loops
• Method Declarations and Invocations
• Recursion
• Printing functions such as System.out.println() for integers
• Classes and Objects

Test Cases

We have include multiple test cases in the tests/ folder to test different features. These test cases include:

• test1.java : simple test case for function calls and object creation
• test2.java : while loops, and if-else
• test3.java : use of this pointer
• test4.java : complex arithmetic operations
• test5.java : test for arrays
• test6.java : test for short-circuiting
• test7.java : if-else and while example
• test8.java : test for recursion
• test9.java : object creation from a separate call
• test10.java : test for printing numbers using System.out.println()

Compilation

cd milestone4/src
make

Execution

Generating the Intermediates

There are four possible options flags:

• --input : To specify the path of the input file (Required)
• --output : To specify the path of the output text file containing the 3AC (Required)
• --verbose : If used, the user can see the exact rules that are being used during the parsing (Optional)
• --help : can be used to see the available flags and their usage

For example:

./parser --input=../tests/test_1.java --output=3ac.txt --verbose

The resulting output will be the IR (in a 3AC format) stored in the 3ac.txt file in the folder named temporary

Final Assembly code generation

g++ asmgen.cpp
./a.out --input=<input_file> --output=<output_file>
gcc <output_file> -o <executable_file>
./executable_file

Here, the input should be the 3AC file generated above, and the output should be the name of the x86 assembly file to be generated (in .s format)

For example:

g++ asmgen.cpp
./a.out --input=3ac.txt --output=test.s
gcc test.s -o test
./test

Here, test.s contains the assembly code for the IR contained in the 3ac.txt file. We compile the test.s file to create the executable test and then simply run the executable and observe the output

Assembly Conventions and Assumptions

• All the arrays and objects are allocated on heap as done by the real JAVA compiler
• 6 registers are used to transfer arguments to a function, and if there are more arguments, we push them onto the stack.
• First register is reserved for the this pointer
• We have assumed that the maximum dimension for the arrays is 3 and the word size is 8 to maintain the alignment property