matematikaadit / rec-jit

A Basic JIT-Compiler for a simple math recurrence relation based on https://nullprogram.com/blog/2015/03/19/

Rec-JIT

A Basic Just-In-Time Compiler for a simple math recurrence relation based on https://nullprogram.com/blog/2015/03/19/. Currently only works on x86_64 Linux System.

Building

To use this program, you need Rust to compile it.

$ git clone https://github.com/matematikaadit/rec-jit.git
$ cd rec-jit
$ cargo build

Explanation and Usage

From the console run

$ cargo run

Then supply a three lines. The first line is the recurrence expression. The second line is the initial value. And the third line is the number of iteration.

For example typing in the stdin:

+2 *3
0
10

Or using sample input.txt:

$ cargo run < input.txt

Is the same as calculating the recurrence U[n] = (U[n-1] + 2) * 3, with the initial value 0, and the number of iteration 10. Thus the program will give output:

Term 0: 0
Term 1: 1
Term 2: 4
Term 3: 13
Term 4: 40
Term 5: 121
Term 6: 364
Term 7: 1093
Term 8: 3280
Term 9: 9841
Term 10: 29524

Playground Demo (might be outdated). For full explanation, see the reddit thread.

How it works

Basically, the program will parse the expression in the first line and translate each operation into corresponding x86_64 instruction. All this instruction is saved in a memmapped buffer which will be transmuted into a fn(i64) -> i64 function after the execute bit is set on its page.

To find the corresponding instruction for each operator, file peek.s is provided. It's used as follow:

$ nasm peek.s
$ ndisasm -b64 peek

The output then used to implement the corresponding operator and instruction.

Reference

• A Basic Just-In-Time Compiler
• /r/dailyprogrammer challenge thread
• mmap crate for inspiration

Future Ideas and Possible Improvement

• Bot for executing this program
• Make it works on Windows
• RPN calculator
• use LLVM

License

Unlicense, see UNLICENSE for more explanation.