[perl #124098] [PERF] Passing an argument list to the export trait slows the parse stage down a lot.

[Aleks-Daniel Jakimenko-Aleksejev via RT]

I can reproduce. The difference at 2017.11-36-g78caeb6bc is ≈0.133s vs ≈0.732s
On 2015-03-17 05:58:27, pe...@reproducible.io wrote:
> First reduced test-case (no argument):
>
> constant C1 is export = 1;
> constant C2 is export = 2;
> constant C3 is export = 3;
> constant C4 is export = 4;
> constant C5 is export = 5;
> constant C6 is export = 6;
> constant C7 is export = 7;
> constant C8 is export = 8;
> constant C9 is export = 9;
> constant C10 is export = 10;
> constant C11 is export = 11;
> constant C12 is export = 12;
> constant C13 is export = 13;
> constant C14 is export = 14;
> constant C15 is export = 15;
> constant C16 is export = 16;
> constant C17 is export = 17;
> constant C18 is export = 18;
> constant C19 is export = 19;
> constant C20 is export = 20;
>
> Second reduced test-case (empty argument list):
>
> constant C1 is export() = 1;
> constant C2 is export() = 2;
> constant C3 is export() = 3;
> constant C4 is export() = 4;
> constant C5 is export() = 5;
> constant C6 is export() = 6;
> constant C7 is export() = 7;
> constant C8 is export() = 8;
> constant C9 is export() = 9;
> constant C10 is export() = 10;
> constant C11 is export() = 11;
> constant C12 is export() = 12;
> constant C13 is export() = 13;
> constant C14 is export() = 14;
> constant C15 is export() = 15;
> constant C16 is export() = 16;
> constant C17 is export() = 17;
> constant C18 is export() = 18;
> constant C19 is export() = 19;
> constant C20 is export() = 20;
>
> Using ``perl6 --stagestats`` to compare these reduced test-cases, the
> parse stage is way slower when an argument list is passed to the
> export trait:
>
> ================ =========== ============== ========
> CPU no argument empty argument slowdown
> ================ =========== ============== ========
> Core 2 Duo L9400 0.4s 1.4s x3.5
> Atom CPU D525 1.3s 5.2s x4.0
> ================ =========== ============== ========
>
> Please note that the slowdown is the same when the argument list isn't
> empty, for instance when using ``is export(:tag)``.
>
> PS: almost all export traits in NativeCall.pm have an argument list.