Function compile_region_to_wasm 

pub fn compile_region_to_wasm(
    ops: &[Op],
    constants: &[Constant],
    num_params: u32,
    num_regs: u32,
) -> Option<Vec<u8>>

Lower an integer region to a WebAssembly module exporting one function f of num_params i64 parameters returning i64. VM registers map 1:1 to WASM locals (0..num_params params, num_params..num_regs declared i64 locals); one extra i32 local at index num_regs is the dispatch “next block” index.

Returns None — the region stays on the bytecode tier — for any op outside the integer fragment (control flow, calls, and all concurrency / channel / networking ops), a non-Int constant, an out-of-range jump target, or a region without a reachable Return.