Dust Assembler

Dust is an assembler for the Pixi VM.

Usage

Assembler script is /dust/dust.py. Usage: dust.py <input> <output> where input is an assembly file and output is the desired compiled output.

Syntax

A line can be either blank, a comment, a label, an instruction, or data.

A comment lines start with #:

# This is a comment

A label consists of any number of upper case letters and must end with ::

LABEL:

An instruction consists of an op code and two operands. An op code is any of the op codes supported by Pixie (lower case): mov, add, sub, mul, div, rem, not, and, or, xor, eq, le, leq, jnz, in, out. An operand can be either a register or a number. Registers (lower case) are r0, r1, r2, r3, sb, sp, pc. Numbers can be written in decimal, hexadecimal, or binary notation, eg: 42, 0x2A, 0b101010. An operand can be optionally prefixed by * to mark it as a dereference:

mov *r0 0xBEEF
jnz r1 :LABEL

Data can be any sequence of numbers. These are simply inlined in the resulting program. Data can be used to store constant values:

1 2 3 4 5

See BNF Grammar for formal language definition.

Examples

Following is an example program which counts down from 10, outputs numbers, then terminates:

# Countdown from 10
    mov r0 10
REPEAT:
    out r0 0
    sub r0 1
    jnz r0 :REPEAT
# Pixie terminates when PC is at 0xFFFF
    jnz 1 0xFFFF
    

For a more complex example, check out the Brainfuck interpreter here.