CS444 Joos Compiler

CS444 Course Project -- DO NOT PLAGIARIZE

Authors

• Xia Liu
• Ryan O'Leary
• Ahmed Al-Sudani

AST Summary

The AST generation code lives in src/lib/haskell/JoosCompiler/Ast/. The AST we currently have should be sufficient for all of A2.

An example of AST usage is in src/ast/Main.hs.

We have chosen to keep the structure of the parse tree even after AST generation. This allows us to gradually convert parts of the tree and gives us access to the parse tree where it's needed.

How the AST is converted

There is a function cstToAst in Core.hs. This function recursively calls the correct "transformer" on each node of the tree.

A transformer is a function with signature [AstNode] -> TaggedParseTree -> AstWrapper. The reason for that weird signature is that it accepts those two arguments:

• transformedChildren, a list of the node's children after they had been transformed with cstToAst
• rootNode, the node that we are going to transform now

The reason behind this signature is that we want to have access to the ASTs for the children nodes by the time we get to the root node. This makes our work much easier since it's easier to work with the AST than the CST, and the children are ASTs.

For example, we don't have to traverse the tree to find out the type of a variable. We can simply look for its AstType node.

There is a bunch of transformers that we have defined in src/lib/haskell/JoosCompiler/Ast/Transformers. The correct transformer is picked by getTransformer in Core.hs, which decides based on the tokenName (which can be Identifier, Modifier, int, etc.). The complete list is in def/joos.cfg2, of course, which defines our grammar.

AST Types

The types for our AST are messy and a little convoluted. The reasons are:

1. Haskell does not allow some type operations that would have made our types simpler
2. We are trying to take advantage of type checking as much as we can, even if our types become somewhat cumbersome

The types are essentially:

• a, where a stands for some node type defined in src/lib/JoosCompiler/Ast/NodeTypes.hs. This can be something like Type, ClassDeclaration, Block, etc.

• AstWrapper, which wraps the node types in NodeTypes.hs. It can also wrap a TaggedToken, which is how we keep the parse tree

• AstNode :: Tree AstWrapper

Working with the AST

Importing JoosCompiler.Ast should be sufficient, but if you find that you are missing some types, they might be in JoosCompiler.Ast.NodeTypes or JoosCompiler.Ast.Transformers.Types.

There are also types you might need in JoosCompiler.Treeify (ones relevant to the parse tree).

JoosCompiler.TreeUtils will certainly come in handy too. It has functions of various signatures for finding nodes in trees.

If you are searching for an AST node of a specific type (e.g. a block or a method declaration), you will probably want to use one of the functions in TreeUtils and the AstWrapper -> Bool functions in JoosCompiler.Ast.Transformers.Types. Feel free to add more if you need to.

Debugging

If you need to debug your code or use a REPL, you can run make ghci.

This snippet worked for me when I was testing things

:l src/compiler/Main.hs

:set +m
:set prompt "> "

import Data.Tree
import JoosCompiler.Ast.Utils
import JoosCompiler.TokenTypeConstants

let filenames = [ "test/marmoset/a3/negative/Je_6_NonStaticAccessToStatic_Method.java"
                , "test/stdlib/5.0/java/lang/Boolean.java"
                , "test/stdlib/5.0/java/lang/Byte.java"
                , "test/stdlib/5.0/java/lang/Character.java"
                , "test/stdlib/5.0/java/lang/Class.java"
                , "test/stdlib/5.0/java/lang/Cloneable.java"
                , "test/stdlib/5.0/java/lang/Integer.java"
                , "test/stdlib/5.0/java/lang/Number.java"
                , "test/stdlib/5.0/java/lang/Object.java"
                , "test/stdlib/5.0/java/lang/Short.java"
                , "test/stdlib/5.0/java/lang/String.java"
                , "test/stdlib/5.0/java/lang/System.java"
                , "test/stdlib/5.0/java/io/OutputStream.java"
                , "test/stdlib/5.0/java/io/PrintStream.java"
                , "test/stdlib/5.0/java/io/Serializable.java"
                , "test/stdlib/5.0/java/util/Arrays.java"
                ]

taggedTrees <- mapM taggedTreeFromFile filenames

let ast = cstsToAst taggedTrees

let program = astWholeProgram $ rootLabel ast

putStr $ drawTree $ fmap show ast

Changing the test set

make TESTSET=test/marmoset/a2 test.positive

Using GDB

gdb --tui output/main
(gdb) b _start
(gdb) r
(gdb) n
(gdb) layout regs

Downloading Profiling Libraries

stack build --prof