CTFE and Static If Question

[jmh530]

On Thursday, 7 May 2020 at 15:34:21 UTC, ag0aep6g wrote:
> [snip]
>
> The `static if` is guaranteed to be evaluated during 
> compilation. That means, `foo!y0` effectively becomes this:
>
>     auto foo(int rt) { return rt + 1; }
>
> There is no such guarantee for `foo(rt, y0)`. It doesn't matter 
> that y0 is an enum.
>
> But a half-decent optimizer will have no problem replacing all 
> your calls with their results. Compared with LDC and GDC, DMD 
> has a poor optimizer, but even DMD turns this:
>
>     int main() {
>         int rt = 3;
>         bool x0 = true;
>         bool x1 = false;
>         enum y0 = true;
>         enum y1 = false;
>         return
>             foo(rt, x0) +
>             foo(rt, x1) +
>             foo!y0(rt) +
>             foo!y1(rt) +
>             foo(rt, y0) +
>             foo(rt, y1);
>     }
>
> into this:
>
>     int main() { return 21; }

Thanks for the reply.

The particular use case I'm thinking of is more like below where 
some function bar (that returns a T) is called before the return. 
Not sure if that matters or not for inlining the results.

T foo(T[] x, bool y) {
     if (y)
         return bar(x) / x.length;
     else
         return bar(x) / (x.length - 1);
}