SixtyPical

Version 0.21
| See also: Bubble Escape 2K
∘ SITU-SOL

NOTE: Having met the majority of its goals, the SixtyPical project
might not undergo much more development going forward. See
Future directions for SixtyPical for more information.

SixtyPical brings advanced static analysis to the 6502.

SixtyPical is a low-level programming language
supporting some advanced static analysis methods.
Its reference compiler can generate efficient code for
several 6502-based target platforms while catching many
common mistakes at compile-time, reducing the time spent in debugging.

Quick Start

Make sure you have Python (2.7 or 3.5+) installed. Then
clone this repository and put its bin directory on your
executable search path. Then you can run:

sixtypical

If you have the VICE emulator suite installed, you can run

sixtypical --run-on=x64 eg/c64/hearts.60p

and it will compile the hearts.60p source code and
automatically start it in the x64 emulator, and you should see:

You can try sixtypical --run-on on other sources in the eg directory
tree, which contains more extensive examples, including an entire
game(-like program); see eg/README.md for a listing.

Features

SixtyPical aims to fill this niche:

You'd use assembly, but you don't want to spend hours
debugging (say) a memory overrun that happened because of a
ridiculous silly error.
You'd use C or some other "high-level" language, but you don't
want the extra overhead added by the compiler to manage the
stack and registers.

SixtyPical gives the programmer a coding regimen on par with assembly
language in terms of size and hands-on-ness, but also able to catch
many ridiculous silly errors at compile time.

Low level

Many of SixtyPical's primitive instructions resemble those of the
MOS Technology 6502 — it is in fact intended to be compiled to 6502
machine code. However, it also provides some "higher-level" operations
based on common 8-bit machine-language programming idioms, including

copying values from one register to another (via a third register when
there are no underlying instructions that directly support it)
copying, adding, and comparing 16-bit values (done in two steps)
explicit tail calls
indirect subroutine calls

While a programmer will find these constructs convenient, their
inclusion in the language is primarily to make programs easier to analyze.

Static analysis

The SixtyPical language defines an effect system, and the reference
compiler abstractly interprets the input program in the manner of
flow typing to confirm that it does not violate it. This can detect
common mistakes such as

you forgot to clear carry before adding something to the accumulator
a subroutine that you called trashes a register you thought it preserved
you tried to read or write a byte beyond the end of a byte array
you tried to write the address of something that was not a routine, to
a jump vector

Efficient code

Unlike most conventional languages, in SixtyPical the programmer must manage
memory very explicitly, selecting the registers and memory locations to store
each piece of data in. So, unlike a C compiler such as cc65, a SixtyPical
compiler doesn't need to generate code to handle calling conventions or
register allocation. This results in smaller (and thus faster) programs.

The flagship demo, a minigame for the Commodore 64, compiles to
a 930-byte .PRG file.

Target platforms

The reference implementation can analyze and compile SixtyPical programs to
6502 machine code formats which can run on several 6502-based 8-bit architectures:

For example programs for each of these, see eg/README.md.

Specification

SixtyPical is defined by a specification document, a set of test cases,
and a reference implementation written in Python.

There are over 400 test cases, written in Falderal format for readability.
In order to run the tests for compilation, dcc6502 needs to be installed.

catseye/SixtyPical

SixtyPical

Quick Start

Features

Low level

Static analysis

Efficient code

Target platforms

Specification

Documentation

On this page

Languages

Contributors