c compiler in python

This is a toy compiler attempting to compile a subset of c in less than 1000 lines of code. Not much is supported as a result. I wrote this over a *weekend as a challenge, or more realistically procrastinating from what I should be doing.

As a result this can only handle basic integer operations! Although the parser has support for a while with break and continue, an if and function calls. I've not built these out as I ran out of time. (when I next procrastinate I might add them :D).

I use sys to be able to access the command line arguments, cast to hack around pythons type system and NoReturn for my implementation of panic. Other than that there are no python libraries used.

Usage

./cc.py <file>

Output:

This shows all of the stages used to generate the x86 code.

C ======
int main() {
    int x = 4 + 5;
    int y = x + 9;
    return y;
}

LEX =====
'int' 'main' '(' ')' '{' 'int' 'x' '=' '4' '+' '5' ';' 'int' 'y' '=' 'x' '+' '9' ';' 'return' 'y' ';' '}' 

AST =====
here
<fun> int main
<params>()
<compound>
	<decl> int 
		<lvar> x = <binop>
		(4 + 5)
	<decl> int 
		<lvar> y = <binop>
		(<lvar> x + 9)
	<return> <lvar> y
TAC =====
main::
	R0 = ADD @i64::4, @i64::5
	R1 = R0
	R2 = ADD R1, @i64::9
	R3 = R2
	RET R3

x86 =====
_main::
	PUSH	RBP
	MOVQ	RBP, RSP
	SUB	RSP,16
	MOVQ	RAX, 4
	MOVQ	RCX, 5
	ADD	RAX, RCX
	MOVQ	-8[RBP], RAX
	MOVQ	RCX, 9
	MOVQ	RAX, -8[RBP]
	ADD	RAX, RCX
	MOVQ	-8[RBP], RAX
	MOVQ	-16[RBP], RAX
	ADD	RSP, 16
	MOVQ	RAX, -16[RBP]
	LEAVE
	RET

Components

Lexer

This is classical lexer splitting the code into a list of tokens without using pythons re library.

Parser

Essentially an LL recursive decent parser, precidence is essentially operator climbing.

IR - TAC

A three Address Code intermediate representation is used to flatten out the ast into something that is easier to convert to assembly

x86_64

A semi-realistic intel style assembly, I'm not too worried that the x86_64 may not run, it's out side of the scope of this project.

Inspirations & Resources

Twitch

I semi-frequently stream on twitch at: https://twitch.tv/Jamesbarford mostly c and mostly compiler related.

*Taking a weekend - I'm building a more real compiler in c for my masters. There's months of learning crammed into these rather shoddy ~900 of code.

Jamesbarford/python-c-compiler