brainfuck-jit

An optimizing JIT Brainfuck interpreter for x86_64, i386, ARM, x86, as well as generic interpreter and C converter.

i386, x86_64, ARM, and aarch64 JIT are supported on both *nix and Windows. Other platforms use a generic interpreter.

A minimal but fast standalone assembly wrapper for the debug output of x86_64 *nix is provided.

void brainfuck(const char *code, size_t len, int optlevel);

Usage:

const char *code = "+[-[<<[+[--->]-[<<<]]]>>>-]>-.---.>..>.<<<<-.<+.>>>>>.>.<<.<-.";
brainfuck(code, strlen(code), 2);

$ make
$ ./brainfuck-jit file.bf

The program will default run an example which prints the alphabet backwards, but you can provide a single filename and it will run that instead. Add -O[n] as the first argument to play with optlevel.

Brainfuck behavior

• All cells are 8-bit unsigned integers.
• 65536 cells, allocated in heap memory.
• Pointer starts at the beginning of the tape.
• Writing out of bounds is UB.
• Mismatched []s are treated as errors during compilation.
• EOF from , is treated as 0xFF.
• optlevel turns on or off optimizations.
• When make DEBUG=1 is used, it outputs opcodes to bf.s, raw machine code to bf.o, and emits a bunch of debugging info.

The compiler will optimize consecutive operations with optlevel >= 1, and optimize clear loops and multiply loops when optlevel >= 2.

Internally, the compiler uses mmap (or VirtualAlloc) to allocate a block of executable memory, and then executes it.

Unlike some JIT implementations which use syscall, this uses function pointers to getchar and putchar. This means that this has access to fully buffered IO instead of laggy syscalls. The assembly wrapper also uses buffered IO in its syscall wrapper.

This is written in C99, but the code is compatible with a C++ compiler if you prefer.