sblasm

A SUBLEQ macro assembler

SUBLEQ

SUBLEQ is a computer architecture that has only one instruction: SUBLEQ. The instruction stands for SUbtract and Branch if Less than or EQual to zero. Because there is only one instruction, only the operands are specified, which consist of 3 memory addresses that are acted on as follows:

SUBLEQ a, b, c
Mem[b] := Mem[b] - Mem[a]
if (Mem[b] ≤ 0) goto c

To find out more, have a look at the article: SUBLEQ - A One Instruction Set Computer (OISC) and its accompanying video.

Usage

The assembler takes an assembly source filename, assembles it and outputs the code as ascii numbers.

Usage: main.tcl [OPTION]... filename
Assemble SUBLEQ assembly from filename

Arguments:
  -l filename      Output a listing to listing to filename
  -h               Display this help and exit
  --               Mark the end of switches

Examples

There are number of example assembler files in examples/.

FizzBuzz

Here is an example of a FizzBuzz program. The file fizzbuzz.asq is in examples/. It shows the following:

• Comments beginning with ;
• Assembler directives. Here: .include, .word, .asciiz, etc.
• The single assembler instruction sble
• Macros being called. In this example: inc, copy, mod, io::printStr, etc.
• Labels ending with :

; Fizz buzz program
;
; Copyright (C) 2020 Lawrence Woodman <lwoodman@vlifesystems.com>
; Licensed under a BSD 0-Clause licence. Please see 0BSD_LICENCE.md for details.


.include    "arch.inc.asq"
.include    "standard.asq"
.include    "io.asq"


;========================================
;           Start
;========================================
            sble  z z main


;========================================
;           Data Storage
;========================================
count:      .word 100                ; The number to count up to
n:          .word 1                  ; The number being counted
nC:         .word 0
fizzbuzzS:  .asciiz "FizzBuzz"
fizzS:      .asciiz "Fizz"
buzzS:      .asciiz "Buzz"
spaceCh:    .ascii " "


;========================================
;           Main
;========================================
main:       inc count
loop:       sble  #1 count done      ; if count <= 0

            copy  n nC
            mod   #15 nC
            sble  z nC fizzbuzz

            copy  n nC
            mod   #3 nC
            sble  z nC fizz

            copy  n nC
            mod   #5 nC
            sble  z nC buzz

            io::printInt16 n
            jump  nextN

fizzbuzz:   io::printStr fizzbuzzS
            jump  nextN
fizz:       io::printStr fizzS
            jump  nextN
buzz:       io::printStr buzzS
            jump  nextN

nextN:      inc   n
            sble  spaceCh OUT
            jump  loop

done:       sble  z z HALT

Requirements

• Tcl 8.6+
• Tcllib

Vendor Requirements

The following requirements are located in the vendor/ directory.

• xproc

Testing

There is a testsuite in tests/. To run it:

$ tclsh tests/all.tcl

Contributing

I would love contributions to improve this project. To do so easily I ask the following:

• Please put your changes in a separate branch to ease integration.
• For new code please add tests to prove that it works.
• Update CHANGELOG.md.
• Make a pull request to the repo on github.

If you find a bug, please report it at the project's issues tracker also on github.

Licence

Copyright (C) 2020 Lawrence Woodman lwoodman@vlifesystems.com

This software is licensed under an MIT Licence. Please see the file, LICENCE.md, for details.