Awib is a brainfuck compiler entirely written in brainfuck.

• Awib implements several optimization strategies and its compiled
  output outperforms that of many other brainfuck compilers


• Awib is itself a 4-language polyglot and can be run/compiled
  as brainfuck, Tcl, C and bash


• Awib has 6 separate backends and is capable of
  compiling brainfuck source code to Linux executables (i386) and
  five programming languages: C, Tcl, Go, Ruby and Java

Usage

Feed awib brainfuck source code as input and the compiled program
will be written as output.

Awib is a cross-compiler. The supported target platforms are
listed below. By default, the target "lang_c" is chosen.

To specify a target platform, insert a line on the form "@TARGET"
(without the quotation marks and with "TARGET" suitably replaced)
at the very beginning of the source code you wish to compile.
Awib will then produce output accordingly.

386_linux - Linux executables for i386
lang_c - C code
lang_ruby - Ruby code
lang_go - Go code
lang_tcl - Tcl code
lang_java - Java code

For instance, the following input would produce an executable hello
world-program for Linux:

@386_linux
++++++[->++++++++++++<]>.----[--<+++>]<-.+++++++..+++.[--->+<]>-----.--
-[-<+++>]<.---[--->++++<]>-.+++.------.--------.-[---<+>]<.[--->+<]>-.

The following would produce a hello world-program in Ruby:

@lang_ruby
++++++[->++++++++++++<]>.----[--<+++>]<-.+++++++..+++.[--->+<]>-----.--
-[-<+++>]<.---[--->++++<]>-.+++.------.--------.-[---<+>]<.[--->+<]>-.

And this file would give you the hello world-program in C:

@lang_c
++++++[->++++++++++++<]>.----[--<+++>]<-.+++++++..+++.[--->+<]>-----.--
-[-<+++>]<.---[--->++++<]>-.+++.------.--------.-[---<+>]<.[--->+<]>-.

Optimizations

Awib is an optimizing compiler:

• Sequences of '-','>','<' and '+' are contracted into single
  instructions. E.g. "----" is replaced with a single SUB(4).


• Mutually cancelling instructions are reduced. E.g. "+++-->><"
  is equivalent to "+>" and is compiled accordingly.


• Some common constructs are identified and replaced with single
  instructions. E.g. "[-]" is compiled into a single SET(0).


• Loops known to never be entered are removed. This is the case
  for loops opened at the very beginning of a program (when all
  cells are 0) and loops opened immediately after the closing
  of another loop.


• Copy and multiplication loops are replaced with constant time
  operations. E.g. "[->>+++<+<]" is compiled into two RMUL(2, 3),
  RMUL(1,1)), SET(0)..

Requirements

Awib will run smoothly in any brainfuck environment where:

• Cells are 8-bit or larger


• The read instruction ',' (comma) issued after end of
  input results in 0 being written OR -1 being written
  OR no change being made to the cell at all.

The vast majority of brainfuck environments meet these criteria.

Since awib is polyglot, it is also possible to compile and/or run awib
directly as C, tcl or bash. For instance, using gcc, the following
will build an executable file called awib from awib-0.2.b.

$ cp awib-0.2.b awib-0.2.c
$ gcc awib-0.2.c -o awib.tmp
$ ./awib.tmp < awib-0.2.b > awib-0.2.c
$ gcc -O2 awib-0.2.c -o awib

Using bash works fine, but is very very very slow:

$ (echo "@386_linux"; cat awib.b) | bash awib.b > awib
$ chmod +x awib

And tcl:

$ (echo "@386_linux"; cat awib.b) | tclsh awib.b > awib
$ chmod +x awib

Environment

Code compiled with awib will execute in an environment where:

• Cells are 8-bit wrapping integers.


• Issuing the read instruction ',' (comma) after
  end of input results in the current cell being
  left as is (no-change on EOF).


• At least 2^16-1 = 65535 cells are available.


• Operating beyond the available memory, in either
  direction, results in undefined behaviour.

License

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.

Mats Linander, 2014-09-14