[U-Boot] [PATCH] initcall: Move to inline function

[Simon Glass]

Hi Alex,

On Fri, 8 Feb 2019 at 01:58, Alexander Graf <agraf at suse.de> wrote:
>
>
>
> > Am 08.02.2019 um 05:11 schrieb Simon Glass <sjg at chromium.org>:
> >
> > Hi Alex,
> >
> >> On Sat, 2 Feb 2019 at 09:07, Alexander Graf <agraf at suse.de> wrote:
> >>
> >>
> >>
> >>> Am 02.02.2019 um 15:13 schrieb Simon Glass <sjg at chromium.org>:
> >>>
> >>> Hi Alex,
> >>>
> >>>> On Thu, 31 Jan 2019 at 08:06, Alexander Graf <agraf at suse.de> wrote:
> >>>>
> >>>> The board_r init function was complaining that we are looping through
> >>>> an array, calling all our tiny init stubs sequentially via indirect
> >>>> function calls (which can't be speculated, so they are slow).
> >>>
> >>> Is this a compiler warning? Could you let me know what this is?
> >>
> >> It's the code comment I'm removing with this patch :).
> >>
> >>>
> >>>>
> >>>> The solution to that is pretty easy though. All we need to do is inline
> >>>> the function that loops through the functions and the compiler will
> >>>> automatically convert almost all indirect calls into direct inlined code.
> >>>
> >>> You mean it calls the functions one after the other without a
> >>> function-table array?
> >>
> >> Exactly. Magical, eh? It even inlines them!
> >
> > Yes it is surprising. I am also surprised that it reduces code size,
> > but I suppose that is why it does it. Presumably the inlining is what
> > does that.
>
> Yes, of course. With separate object files, the compiler can not inline anything at all, because it does not know how the function pointers get used.
>
> The alternative to this *might* be LTO, which we could think about as well. It should help reduce indirection and code size overall. But I don't know how well gold works with the linker scripts we have.

Hmm don't we have that? We should.

>
> > But what happens if we #define DEBUG?
>
> Define it where? ;)

Yes exactly. At present you can turn this on globally by putting it at
the top of initcall.c. I think it is worth a comment on how to enable
debugging.

Does the code size blow out horribly if debugging is enabled?

(and hello from Munich!)

Regards,
Simon