John outlined two ways to adjust the existing Unsafe.putX contract for values:  

1. Create two new Unsafe operations ���start buffer��� and ���finish buffer��� on values; ���start buffer��� creates a true object instance  (of undefined type) whose layout and contents is exactly the input value instance, and ���finish buffer��� reverses the process.  In between, Unsafe.putInt on the buffer will have predictable effects.  The JIT can easily EA away the buffer, especially since it will be an ���Unsafe party foul��� to do anything with the buffer other than finishing it and walking away with the resulting value. 

2. For every operation like Unsafe.putInt create a corresponding operation Unsafe.withInt which operates on a value instance and returns the new value.  (Remember that putInt returns void.)  This requires not two new Unsafe API points but about 10 (prims + ref + value).  Note that there is no need to worry about relaxed vs. volatile ordering; withInt can only have one ordering because the value instance is always local and unaliased.

John suggested to go with the ���magic buffer��� approach is more robust than the withfield APIs approach.  That is a different approach than the one discussed at valhalla offsite 2018.