Oh on arm you will definitely will want to check out luajit precisely for the number performance - see this comment for details : http://news.ycombinator.com/item?id=2617835 - luajit will use integers where it can.
I did not experiment with this myself though, but hopefully it might ease your woes with no FPU - http://luajit.org/performance_arm.html shows 85x speedup for md5, which I suppose would be integer algorithm.
Out of curiosity, what is the platform, if not a secret ?
I'm developing for an arm processor with no floating point support. so it's best to avoid the software fallback at all costs.
I'm aware of luajit but "plain" lua is still fast enough for my uses. FFI is definitely a killer and beats SWIG hands down.
need to upgrade to 5.2 asap...