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

[Robert Fraser]

Jarrett Billingsley wrote:
> "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. 

How about a struct of size 1?: