Function optimization_trace_vm 

pub fn optimization_trace_vm(source: &str) -> BackendOptimizationTrace

The optimizations that fired while compiling source to VM bytecode — the third path, after AOT codegen and the run-path optimizer. Surfaces the VM-compile-time opts (constant-divisor magic division, VM i32 narrowing) the other two traces cannot see. Compiles only (no execution), so it is fast and needs no program arguments.