Re: [RFC, 2.6] a simple FIFO implementation

[Chris Friesen <cfriesen@nortelnetworks.com>]

Peter Chubb wrote:

> This depends on how expensive % is.  On IA64, something like this:
> 
>      add(char c) {
> 	     int i = p->head == p->len ? p->head++ : 0;
> 	     p->buf[i] = c;
>      }
> 
> is cheaper, as % generates a subroutine call to __modsi3.  It also is
> shorter =-- 12 bundles as opposed to 15.

I did a similar test once for ppc that found that an increment followed by a 
test (marked unlikely) was actually quicker in practice than modulo arithmetic. 
  The branch predictor got it right most of the time, so the test was almost free.

Chris