brainstorm

An optimizing compiler / interpreter for Brainfuck, written in Elixir.

I love compilers and Elixir, but I didn’t want to write a huge parser or tokenizer and die from boredom. Brainfuck is small, simple, and lets me focus entirely on optimizations.

brainstorm is fully capable of interpreting Brainfuck code, as well as producing optimized C programs.

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Quick Example

cat bf_snippets/hello.bf
# >+++++++++[<++++++++>-]<.>+++++++[<++++>-]<+.+++++++..+++.>>>++++++++[<++++>-]<.>>>++++++++++[<+++++++++>-]<---.<<<<.+++.------.--------.>>+.>++++++++++.

Interpret Brainfuck

./bs bf_snippets/hello.bf
# Output: Hello World!

Compile Brainfuck to C

./bs bf_snippets/hello.bf --mode c

Now we have hello.c:

#include <stdio.h>

int main(void) {
  fputs("Hello World!\n", stdout);

  return 0;
}

You can then compile and run the generated C code:

gcc -o hello hello.c
./hello
# Output: Hello World!

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Optimizations

brainstorm supports a wide range of common Brainfuck optimizations, including nearly all of the techniques described in the notable article brainfuck optimization strategies.

• Combine sequential increments/decrements
  +++-- becomes +.

• Combine sequential shifts
  >>>><< becomes >>.

• Remove dead loops at the start of the program
  [+->><.>]++ becomes ++.

• Remove redundant sequential loops
  [>][<] becomes [>].

• Remove dead code at the end
  +++++.>>><- becomes +++++.
  Current limitation: dead loops are not automatically removed.

• Combine increments and shifts into single instructions
  Optimizes patterns like +>+> into fewer operations.

• Detect and replace "multiplication loops"
  Loops that copy or scale values are replaced with direct arithmetic:

  >+++++++++[<++++++++>-].

  becomes

  arr[i + 1] = 9;
  i += 1;
  arr[i - 1] += arr[i] * 8;
  arr[i] = 0;

• Compile-time execution

  brainstorm tries to execute code at compile-time as much as possible. To prevent an infinite time of compilation due to an unexpected infinite loop, brainstorm supports specifying steps limit - how many commands are allowed to be executed at compile-time. It defaults to 8192 and can be changed via --max-steps CLI argument. If you are risky enough, you can specify --max-steps infinity and wait as long as you want.

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Optimization Levels

You can control which optimizations are applied using the opt_level argument:

• 0 - No optimizations (original commands are returned as-is)
• 1 - Basic peephole optimizations
• 2 - Full optimizations (:o1 plus removing trivial loops at start/end, fusing instructions, and unwrapping multiplication loops)

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Examples

# Compile-time "Hello World!"
./bs ./bf_snippets/hello.bf --mode c

# Compile-time calculating squares or numbers from 1 to 1000
./bs ./bf_snippets/squares.bf --mode c --max-steps 1000000

# Run-time "Just another brainfuck hacker,"
./bs ./bf_snippets/jabh.bf

# A ghost game
./bs ./bf_snippets/ghost.bf --mode c

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Installation

git clone https://github.com/samedit66/brainstorm.git
cd brainstorm
mix escript.build
./bs

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Usage

./bs <file.bf> [--opt-level 0|1|2] [--outdir <dir>] [--mode i|c] [--max-steps <number>|infinity]

Options:

• --opt-level (-O, -o) - Set optimization level (0, 1, or 2, default 2)
• --outdir - Directory to write the generated C file (default: current directory)
• --mode - Execution mode (i - interpretation or c - compilation, default i)
• --max-steps - Maximum execution steps (any positive number or infinity, default 8192)