[Issue 6176] [TDPL] Cannot use string variables in case expressions

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6176



--- Comment #6 from Stewart Gordon <smjg at iname.com> 2011-06-20 15:11:09 PDT ---
(In reply to comment #5)
> (In reply to comment #4)
> 
>> If the case values are all constant, create this tree.  
>> Otherwise, just compare the switched value with the cases 
>> individually.
> 
> This is possible, of course, it just requires a bit more 
> complex compiler.

But the extra complexity is nothing compared to implementing the tree
optimisation in the first place.

Moreover, ISTM for switches with only a few values, comparing the cases
individually might be actually more efficient.  So this extra complexity might
actually be needed in order not to pessimise these simpler cases.

> A problem: if one of your strings are not compile-time const, because of a
> mistake of the programmer, there is a silent and invisible loss of performance.

Which is to be expected.  After all, compiler optimisation is a privilege, not
a right.

Though adopting the aforementioned mixture of the two approaches would mean
that any loss of performance would be small.

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