Simulating computed goto

[NonNull]

On Wednesday, 25 November 2020 at 19:04:45 UTC, H. S. Teoh wrote:
> FWIW, D's switch statement is flexible enough to directly write 
> Duff's device.
>
>
>> How good is optimization in ldc2, gdc, dmd at compiling 
>> chained jumps into one jump each time?
>
> I'm pretty sure ldc2 and gdc will optimize away any such 
> chained jumps. But if performance is important to you, I 
> recommend *not* bothering with dmd.

Yes this is about efficiency.

>> Is there a good way to simulate computed goto in D?
>
> With a switch statement. ;)

OK, so I took a look at switch documentation and tried out 
something. It looked like switch can have computed goto using 
case labels.

case 5:
   //...
   goto case <expression>; //doesn't compile when <expression> is 
not a constant

So to simulate computed goto have to
1. wrap switch(x) in a loop [ while(0) ]
2. inside each case recompute x (instead of jump to computed y)
3. jump back to execute switch again [ continue ]

It does look as if a nested switch can contain case labels from 
an outer switch which is very good. Did not try this out.

Any more ideas, advice?