Reamit

Readable assembly code generator

Whether for learning or for optimized code, often we want to write readable assembly that's close to the user-defined behavior. That's where Reamit comes it. It's a programming language based on a subset of Python that maps almost directly to assembly. Right now, only MIPS is supported.

Installation

Install via PyPI:

pip3 install --user reamit

Usage

Use via the reamit command:

reamit -o output.s input.rm

Note: .rm is a new extension for the Reamit language which closely resembles Python.

Examples

simple.py:

def sum_to_n(n: int) -> int:
    num = 0
    total = 0
    while num <= n:
        total += num
    return total

simple.s:

sum_to_n:
	li	$t0, 0	# num = 0
	li	$v0, 0	# total = 0

sum_to_n_while:
	sub	$t1, $t0, $a0	# num <= n:
	bgtz	$t1, sum_to_n_while_end	# num <= n:
	add	$v0, $v0, $t0	# total += num

sum_to_n_while_end:

sum_to_n_end:
	jr	$ra

factorial.rm:

def factorial(n: int) -> int:
    if n == 0:
        return 1
    return n * factorial(n - 1)`

factorial.s:

factorial:
	sub	$sp, 8	# Allocate stack
	sw	$ra, 0($sp)
	sw	$s0, 4($sp)

	# === Arguments ===
	move	$s0, $a0	# n

	bne	$s0, 0, factorial_skip_if	# n == 0:
	li	$v0, 1	# return 1
	j	factorial_end	# return 1

factorial_skip_if:
	sub	$a0, $s0, 1	# n - 1
	jal	factorial	# factorial(n - 1)
	move	$t0, $v0	# factorial(n - 1)
	mul	$v0, $s0, $t0	# n * factorial(n - 1)

factorial_end:
	lw	$s0, 4($sp)
	lw	$ra, 0($sp)
	add	$sp, 8	# Deallocate stack
	jr	$rap

Language

The language works as follows:

• A file consists only of a series of functions
• A function contains arguments and a single return value
• Any external functions that you want to use can be declared at the top of the file like some_func = ...
• Pointers to arrays can be declared as the type ints or bytes (half words not supported)

Example Code

# Define external function to be called
external_func = ...
print_char = ...

# Optionally, define symbols that aren't default in normal Python
ints = ...
bytes = ...

def process_data(data: ints, length):
    i = 0
    total = 0
    while i < length:
        val = external_func(data[i])
        total += val
        data[i] = val
        i += 1
    print_char('d')
    print_char('o')
    print_char('n')
    print_char('e')
    print_char('\n')
    return total