class templates and static if

[Jonathan M Davis]

On Monday, February 27, 2012 10:55:12 Ali Çehreli wrote:
> On 02/27/2012 08:29 AM, Tyler Jameson Little wrote:
> > I didn't want to do subclassing, because my parser is a state-machine
> 
> style
> 
> > parser, so it's in a big switch. Pretty gross, but I would like it to
> 
> be as
> 
> > fast as possible. That's why I thought this model would be so cool,
> 
> because
> 
> > I could remove conditions from the generated code, and get rid of a
> 
> lot of
> 
> > the conditionals.
> 
> I am pretty sure switch statements boil down to a sequence conditionals
> consisting of equality comparisons.
> 
> I know that some compilers use optimizations where the comparisons are
> converted to a single lookup, but last I checked, dmd does not apply
> that optimization. Perhaps because it's not implemented yet, or because
> using a table lookup might be slower because of reaching outside of the
> cpu cache. (Or another reason that I am not aware of. :))

Yeah. In theory, switch statements can be optimized better than if-else 
chains, and eventually I'd fully expect that dmd would do that, but right now, 
I don't think that they really are. You'd have to look at the generated 
assembly though to be sure though.

- Jonathan M Davis