On Mon, 2002-03-18 at 04:32, David Megginson wrote:
> Andy Ross writes:
>
> > It's probably not a quirk. Inlining actually helps very little except
> > for VERY small functions. It used to be that a function call was slow
> > -- you had to spill a bunch of registers and a return value onto the
> > stack, and then clean them up later. But modern processors can, for
> > the most part, stick all that mess into into a few extra pipeline
> > stages.
>
> Yes, that was my guess, too. When the method was just a straight
> getter, like
>
> inline double get_foo () const { return _foo; }
>
> inlining didn't seem to hurt much (and in a couple of cases it made a
> very tiny speed improvement),
Ahh, this is why I didn't see a big difference. Most of our inlines
look just like this.
>but once the inlined code had a couple
> of lines, either in itself or indirectly by invoking other inlined
> code from the standard library headers, inline caused a significant
> slowdown (sometimes >25% in a tight loop). That happened even in the
> inlined code wasn't invoked, i.e.
>
> inline void foo ()
> {
> SG_LOG(SG_GENERAL, SG_ERROR, "An error");
> }
>
> then
>
> bool flag = false;
> if (flag)
> foo();
> // some other stuff
>
> I was surprised by how much faster things like this ran when I
> un-inlined foo().
>
> The build-time problem that Andy mentions has two causes: one is the
> code inlining, and the other is the simple fact that so many modules
> still include headers from so many other modules. Curts FGGlobals and
> my property stuff is an attempt to get rid of (a lot of) that, but the
> cleanup has only started. It might be some consolation to Andy that
> things used to be much worse.
>
>
> All the best,
>
>
> David
>
> --
> David Megginson
> [EMAIL PROTECTED]
>
>
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--
Tony Peden
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We all know Linux is great ... it does infinite loops in 5 seconds.
-- attributed to Linus Torvalds
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