'Expensive' expressions in loop limits (was: Implementation of D3DXSHScale)

[Dan Kegel]

Nozomi wrote:
+    for (i = 0; i < order * order; i++)

I might have written
     int n = order * order;
     for (i=0; i < n; i++)
to avoid repeating the multiplication every time around the loop,
even though multiplication is cheap nowadays, and -O1 will optimize
it out anyway.   Staying in the habit of avoiding 'expensive'
operations in loop limits might still be a good idea, since the
optimizer can't always save you.

Or is that considered ugly these days?

D3DXSHAdd() has the same code, which is where this came from, probably.

[Michael Stefaniuc]

On 06/19/2012 10:47 AM, Dan Kegel wrote:
> Nozomi wrote:
> +    for (i = 0; i < order * order; i++)
>
> I might have written
>      int n = order * order;
>      for (i=0; i < n; i++)
> to avoid repeating the multiplication every time around the loop,
> even though multiplication is cheap nowadays, and -O1 will optimize
> it out anyway.   Staying in the habit of avoiding 'expensive'
> operations in loop limits might still be a good idea, since the
> optimizer can't always save you.
>
> Or is that considered ugly these days?
> Of course as always a definitive "It depends". The safe approach is to
> *first* optimize for the human reader; the compilers this days are
> better at optimizing than the average programmer.

bye
	michael