X[]==Y[] is 7X slower than it should be -- why?

[Jarrett Billingsley]

"Bruce Adams" <tortoise_74 at yeah.who.co.uk> wrote in message 
news:op.udecoog1xikks4 at starquake.cybernetics...
On Fri, 20 Jun 2008 18:40:25 +0100, Jarrett Billingsley
<kb3ctd2 at yahoo.com> wrote:


> extern (C) int _adEq(Array a1, Array a2, TypeInfo ti)
> {
>     if (a1.length != a2.length)
>         return 0;
>
>     auto sz = ti.tsize();
>     auto p1 = a1.ptr;
>     auto p2 = a2.ptr;
>
>     if (sz == 1)
>         // We should really have a ti.isPOD() check for this
>         return (memcmp(p1, p2, a1.length) == 0);
>
>     for (size_t i = 0; i < a1.length; i++)
>     {
>         if (!ti.equals(p1 + i * sz, p2 + i * sz))
>             return 0;
>     }
>
>     return 1;
> }
>

there is no guarantee that memcpy will return the same result as opEquals.

...

Why has no-one screamed about this before?
-----------------

Because that's not how the above function works?  It only calls memcmp if 
the compared array has elements of size 1 -- that is, byte[], ubyte[], and 
char[].  For all other types, it calls ti.equals, which will call the opCmp 
method of classes/structs, if any.