There's no guarantee even without optimization. Some optimizations exploit UB, but not all "unexpected" code generation in the presence of UB is due to optimiza

There's no guarantee even without optimization. Some optimizations exploit UB, but not all "unexpected" code generation in the presence of UB is due to optimization. Take signed int overflow on addition. On some platforms ADD wraps, on others it traps. Depending on target CPU you'll get very different behavior even for non-optimizing compilers that just emit an ADD instruction! WASM is just another target, with its own behavior.