Very limited shared promotion

[aliak]

On Monday, 24 June 2019 at 02:55:39 UTC, Walter Bright wrote:
> On 6/23/2019 7:42 PM, Timon Gehr wrote:
>> I really don't understand this "before" without memory 
>> barriers. Without memory barriers, there is no "before". How 
>> to formalize this? What is it exactly that "scope" guarantees?
>
> The reference to shared i does not extend past the end of the 
> function call. That doesn't mean the cached value of i is 
> propagated to all other threads.
>
>     int x;
>     void fun(scope ref shared(int) x) {
>         x = 3; // (*)
>     } // end of reference to x is guaranteed
>     assert(x == 3); // all caches not updated, assert is not 
> guaranteed
>
> (*) now replace this with a call to another thread to set x to 
> 3.

You can assign to a shared primitive without a compilation error?

Does the compiler do the necessary synchronization under the hood?

I would've assumed you'd have to use atomicStore or the like?