This reminds me of HipHop for PHP. HipHop lowers PHP to C++, with a direct mapping for control flow (control structures, exceptions) and a runtime library for everything else. Apparently it works very well.
Interestingly, Facebook sponsored a project to build a prototype PHP interpreter using the PyPy[0] toolchain for JIT compilation, which turned out to be even faster than HipHop[1]. I have to wonder whether statically compiled Ruby would actually be any faster than a JIT interpreter like Rubinius, cold start JIT penalty aside.
Edit: looks like JRuby can/does do JIT compilation, but it is also capable of doing AOT compilation[2]. If JRuby can do AOT, then what is the point of FastRuby?
JRuby does have an AOT compiler, but the resulting code must be shackled to the rather large JRuby runtime. Is also does a slower dynamic call that fastruby (except on invokedynamic).
My goal with fastruby is more to have a still dynamically-typed Ruby-like language without requiring anything more than virtual invocation and a modest runtime library (that can be statically optimized to only what's needed by e.g. Android toolchain).
Could this be mixed with Mirah to have it dynamically typed, but with types added where needed for performance? Sort of like Dart's optional typing, but for the JVM.
I've had thoughts about doing a Rubinius bytecode interpreter in PyPy, but I can't find a decent reference to Rubinius' bytecode format other than the source. That'll take more time to wade through than I've got right now.
