Re: About g++ optimization

[Andre Poenitz]

rmansfield@gmail.com <rmansfield@gmail.com> wrote:
> If your f() returns a constant, your best bet is to do:
> 
> for (int i =0,  j = f(n); i < j; ++i) {
> }

Or if it doen't matter in what order the iteration is performed,
even

 for (int i = f(n); i--; )

might do. (Note the i-- is post-decrement and in the 'test' position)

Saves usually a register and replaces a check against an 'arbitrary'
number with a check for zero (which is faster/smaller on some
architectures).

Of course, this won't work when you can't invert the iteration order.

Andre'