Integer overflow and underflow semantics?

[via Digitalmars-d]

On Saturday, 19 July 2014 at 19:49:24 UTC, Ola Fosheim Grøstad 
wrote:
> On Saturday, 19 July 2014 at 08:34:39 UTC, Kagamin wrote:
>> Can't it simply generate code as is? Seems wasteful to spend 
>> compilation time on this.
>
> Not if you want fast code, consider a template with:
>
> if (a.length+M < b.length+N) {}
>
> then you alias b = a in the template instantiation:
>
> if(a.length+M < a.length+N){}
>
> you want this reduced to:
>
> if (M<N){
> }
>
> which can be resolved at compile time.

Yes, but that is the optimizer's job. The front-end doesn't need 
to spend time on it, if the back-end then anyway does the same 
optimization again.