Not sure why you think this is the case: there are numerous JITs/VMs that optimize starting from bytecode e.g. all JVMs, WebAssembly, V8, JSC,... Can you point

Not sure why you think this is the case: there are numerous JITs/VMs that optimize starting from bytecode e.g. all JVMs, WebAssembly, V8, JSC,... Can you point me to some paper/reference about this? AFAIK it doesn't matter whether you have an AST or bytecode. Optimizations are done on an IR anyways.