[PATCH] common/board_f.c: use #ifdefs a little more consistently

[Tom Rini <trini@konsulko.com>]

On Fri, Feb 28, 2020 at 05:24:58PM +0000, Rasmus Villemoes wrote:
> On 28/02/2020 16.46, Tom Rini wrote:
> > On Fri, Feb 28, 2020 at 08:42:21AM +0000, Rasmus Villemoes wrote:
> >> On 28/02/2020 00.40, Simon Glass wrote:
> 
> >>> Using if() is preferable to #if if there is no cost.
> >>
> >> Completely agree, and I also prefer to have the linker eliminate unused
> >> functions rather than cluttering the C code with #ifdefs. But that can't
> >> be used in this case.
> >>
> >> Anyway, this wasn't primarily to save 112 bytes or whatnot from the
> >> U-Boot image, just to use one style a little more consistently.
> > 
> > Perhaps we could come up with a little more macro-magic?  In
> > psuedo-code:
> > #define RESERVE_INIT_SEQ_F_ENTRY(fn) \
> > #if CONFIG_IS_ENABLED(toupper(fn))
> > reserve_##fn
> > #endif
> > #endif
> 
> I'm afraid that's rather far from something that can be implemented;
> macros cannot expand to other preprocessor directives, and toupper is
> also pretty hard to do.

Darn.  I would have been willing to move to reserve_FUNCTION if it would
have otherwise worked.

> What we could do if we want to reduce #ifdefs while still eliminating
> the no-op functions is to replace
> 
> #ifdef CONFIG_FOO
> static int foo_init(void) {
>   blabla;
>   return 0;
> }
> #endif
> ...
> init_sequence_f[] = { ...
> #ifdef CONFIG_FOO
>   foo_init,
> #endif
> ...
> }
> 
> by
> 
> static int foo_init(void) { /* always defined */
>   blabla;
>   return 0;
> }
> 
> init_sequence_f[] = { ...
>   IS_ENABLED(CONFIG_FOO) ? foo_init : NULL,
> ...
> }
> 
> and teach the iterator to ignore NULL entries (I don't remember if we
> use a NULL terminator or use ARRAY_SIZE; if the former one should switch
> to the latter). It will still cost sizeof(void*) for the NULL entries,
> but the function bodies (and on powerpc the .fixups) should be
> eliminated, and there's not an #ifdef in sight.

That sounds pretty nice actually.  If you're so inclined I'd like to see
it.

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 659 bytes
Desc: not available
URL: <https://lists.denx.de/pipermail/u-boot/attachments/20200228/144d46cb/attachment.sig>