Your example has nothing to do with the actual code in the kernel. In the original code, the counters are passed by reference to a function. That means they need to be in memory anyway, right? The compiler can't pass the address of a register.
> That means they need to be in memory anyway, right?
Actually no, GCC can optimize out pointer indirection like that if it ends up inlining the function (which it could in the kernel example, since it's static, relatively short, and has only three callers).
Another contrived example:
static int inlineme(int *lol, int lolol)
{
*lol += lolol;
return *lol * 5;
}
int test(int x)
{
int tmp = 5;
tmp += inlineme(&tmp, x);
return tmp;
}
Note that "tmp" doesn't have to be a constant for that to happen.
As far as the actual kernel function, GCC ends up emitting:
(The only uncompressed kernel binary I had laying around was for my beaglebone black, sorry)
... so in this case it does actually pass by reference.
That doesn't change my argument: an array is the more confusing way to do this, and in similar situations could prevent the compiler from making the optimization it did in my example.
