pycmpy

Learning about compilers and the assembly language with the Raspberry Pi.

Most files are mainly just examples, some may not work.

pycmpy/ folder contains a semi functional compiler written in python. It can add numbers and stuff, just not print them. It can print words, just not do anything else with them. See the directories README for more info.

pycmpy compiler

We can compile super non-trivial programs like this that will totally blow your mind. Say we have source file hello.cmpy whose contents is as follows:

print "hello, world!";

We can use pycmpy to compile this to native machine code by runninging (from within this directory):

$ python pycm.py hello.cmpy -o hello

What this will do is take the file hello.cmpy and create the executable hello. You should see an output like this.

Created file: hello.s
making executable...
------------------------------------------------
as -o hello.o hello.s
as -o io.o lib/io.s
ld -o hello hello.o io.o
Created file: hello.s
------------------------------------------------
successfully created executable:'hello'
to run: $ ./hello

We can now run this crazy program.

$ ./hello
hello, world!

Behind the scenes pycmpy created the file hello.s which in this case looks like this.

.global _start
_start:
	LDR R0, =string_const_0x0000
	MOV R1, #14
	BL io_print

	MOV R0, #0
	MOV R7, #1
	SWI 0

string_const_0x0000: .asciz "hello, world!\n"

.extern io_print

The io_print routines and possibly others are defined in the lib directory. After creating this it hands the rest over to as and ld who finish the job creating the executable.