Mini-Java to LLVM IR compiler, a semester project for the compilers course at the University of Athens

make

java Main <inputFile1> <inputFile3> <inputFile3> ...

Then the LLVM IR files are generated like <inputFile3>.ll

To run the LLVM clang needs to be installed

sudo apt update && sudo apt install clang-4.0

Then compile the .ll file with

clang-4.0 -o <executable> <inputFile3>.ll

or run the experiments with ./run.sh

All the classes, variables, and methods are stored on the SumbolTable. The SymbolTable class inherits from the TreeMap data structure in java and it stores objects of the Symbol type. Symbol class is an abstract class that all the classes, variables, and methods inherit from. It shares the common information about these fields such as name, type, and offset. In SymbolCLass class are stored all the classes. There are fields for the methods and the variables of the classes. These fields are stored in a SymbolTable too. In SumbolMethods are stored all the methods of the class. This object also stores the variables and the arguments of the method. Finally SymbolVariable stores the variables. Both SYmbolClass and SymbolMethod implement setters and getters according to their needs.

The VirtulaTable is a TreeMap data structure that holds all of a class's methods. It recursively records the parent classes' methods, and if a child class overrides one of them, the information is given to the table.

As for the visitors, there are 4 of them that implement different processes of semantic checking and for the LLVM IR generation. Firstly the parse tree is visited by the ClassDeclarationVisitor is responsible for adding to the SymbolTable all the class declarations. Then the parse tree is visited by the FillVisitor that fills all the classes with their variables and methods and also fills the arguments and the variables of the methods too. Then, the parse tree is visited by the CheckTypeVisitor which performs type checking of the expressions and the statements of the methods. Finally, the LLVM visitor parses the tree and creates LLVM IR based on the data in the Symbol and Virtual tables.