Data races are undefined behavior¹ so in that case the compiler is still technically preserving semantics but if you use the proper primitives to remove undefined behavior (atomic operations, locks) for any shared state then the compiler will not generate code w/ undefined behavior & all modifications/mutations will be serialized in some order. You can then further refine the code if you want the operations to happen in a certain order. At the end of the day you must assume that the compiler will preserve your intended semantics otherwise we'd still be writing assembly b/c no high level specification would ever mean what it was intended to mean for the low-level executable machine model/target of the compiler.

¹https://cppreference.com/w/cpp/language/multithread.html