> Date: Thu, 10 May 2018 07:23:05 -0500
> From: Segher Boessenkool <[email protected]>
> On Thu, May 10, 2018 at 10:33:39AM +0200, Marc Glisse wrote:
> > int x, y;
> > void f(int n){
> > int c = 3 << 20;
> > x = n / c;
> > y = x / c;
> > }
> Without the replacement we have two dependent divisions; with the
> replacement we have two independent divisions, and that is much faster
> on some (many?) systems (that can do two fixed-point divisions in parallel),
> even if things do not simplify further.
Sometimes the case is that way, sometimes yet another: your case
can also increase register pressure, which is bad for some
(many?) systems.
brgds, H-P
