Re: [PATCH] bitops: simplify generic bit finding functions

Linus Torvalds
2008-04-28T16:55:59Z

On Mon, 28 Apr 2008, Thomas Gleixner wrote:

> On Mon, 28 Apr 2008, Linus Torvalds wrote:
> > >
> > > How about making the optimization controlled by a config switch so
> > > arch maintainers can decide whether they want to enable the constant
> > > optimization or unconditionally call the lib function ?
> >
> > No.
> >
> > This is just making that damn header line look worse and worse.
> >
> > Is there a _reason_ to optimize this stupid function this way?
>
> On architectures which have a find bit instruction we can replace the
> call to the library function by a single instruction when the size of
> the bitmap is less/equal bits per long and when the bitnr is a
> constant.

That's not what I asked.

I asked whether there is a *reason* to optimize this and cause all these
stupid problems.

Is there a real hot path anywhere that actually uses this and depends on
it?

Linus