On Mon, Nov 12, 2007 at 11:07:55PM +0100, Bernd Schmidt wrote:
> Adrian Bunk wrote:
> > It can be a performance regression, but there are also cases where it
> > can improve performance. If gcc produces lower performance code that
> > would be a bug in gcc that should be reported, but using a division is
> > not generally wrong.
> >
> > A more clearer example might be:
> >
> > <-- snip -->
> >
> > void foo(u64 ns)
> > {
> > if (ns < 10000)
> > return;
> >
> > while(ns >= 3) {
> > ns -= 3;
> > #ifdef DEBUG
> > bar(ns);
> > #endif
> > }
> > }
> >
> > <-- snip -->
> >
> > With DEBUG not defined you can hardly argue gcc should be fixed to not
> > use a division for performance reasons.
>
> Absent any clear information about the possible values of ns,
>...
In this example, there is clear information about the possible values
of ns...
> Bernd
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
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