в расте Send/Sync, поэтому кейворд не нужен и всей связанной с этим магии нет, а для функций задокументированно поведение, например:
read_volatile
Performs a volatile read of the value from src without moving it. This leaves the memory in src unchanged.
Volatile operations are intended to act on I/O memory, and are guaranteed to not be elided or reordered by the compiler across other volatile operations.