Passing array as const slows down code?

[Joseph Rushton Wakeling]

On 04/05/12 18:07, Joseph Rushton Wakeling wrote:
> On 03/05/12 16:59, Artur Skawina wrote:
>> There *was* a GDC bug some time ago, where a 'const' or 'in' function argument
>> prevented inlining. Iain fixed it, so unless an old GDC version is used, it's
>> probably not related.
>
> I'm running GDC 4.6.3; I don't know if this fix made it into that release. It
> would make sense if faulty inlining was responsible, though.

Let me clarify that last statement.  The core function in the struct is one that 
does something like this (pseudocode):

     auto myMainFunc(Rating[] x)
     {
         do {
             myFunc1(x);
             myFunc2(x);
             myFunc3(x);
             /* calculate exit-condition value*/
         } while (/* conditions not met */)

         return results;
     }

So, if I'm putting in const (or const ref) qualifiers, they're being applied to 
the inputs of myMainFunc, myFunc1, myFunc2 and myFunc3.  These 3 are obvious 
candidates for compiler inlining, so anything which affects the possibility of 
this happening could be expected to hit performance.

(... in the real code, myMainFunc() is called reputation(); the 3 interior 
functions are respectively userDivergence(), userReputation() and 
objectReputation().)