Some fact correcting, first of all while most people refer to "The JVM", most likely impling OpenJDK, Java is a standard and there are many implementations.

Which exactly in this subject varies a lot between implementations, on how well escape analysis is done, if there is a JIT cache between JVM executions, or AOT compilation.

Additionally Valhalla is finally getting added to the language with a new EA made available last week, thus value classes will add yet another way to have stack values.