[U-Boot] [RFC] bug.h: Drop filename from BUG/WARNING logs if building for TPL/SPL

[Andreas Dannenberg]

Yamada-san,

On Fri, Jul 12, 2019 at 02:29:02AM +0900, Masahiro Yamada wrote:
> On Fri, Jul 12, 2019 at 12:34 AM Andreas Dannenberg <dannenberg at ti.com> wrote:
> >
> > On Wed, Jul 10, 2019 at 04:30:44PM -0500, Andreas Dannenberg wrote:
> > > On several platforms space is very tight when building for SPL or TPL.
> > > To claw back a few bytes to be used for code remove the __FILE__ name
> > > from the BUG() and WARN() type macros. Since those macros still print
> > > the function name plus a line number this should not really affect
> > > the ability to backtrace an actual BUG/WARN message to a specific
> > > piece of code.
> > >
> > > Signed-off-by: Andreas Dannenberg <dannenberg at ti.com>
> > > ---
> > >
> > > I was looking for a way to shave off a few bytes from the SPL code size
> > > (TI AM335x) and looking at the hexdump of the SPL I found well why not
> > > further reduce some strings down in size... I was already aware of the
> > > recent compiler optimizations to drop some of the irrelevant path from
> > > the __FILE__ macro but I wanted to go one step beyond this. Dropping
> > > all the path from __FILE__ via preprocessor macro can't be easily done
> > > as others have already found so I decided to drop __FILE__ altogether
> > > (code below) and was excited about the improvements I got...
> >
> > Just some quick examples about the savings...
> >
> > Using buildman "bloat" reporting (-B) I see the SPL .text size for AM335x
> > to be reduced by 12 bytes. And for AM43xx the size goes down by 52
> > bytes. The benefit of the proposed change really depends on a) whether a
> > given platform uses SPL, and b) how many calls to BUG/WARN it has. The
> > USB drivers in AM335x/AM43xx are really the "heavy hitters" here. I'm
> > sure I could find additional examples/platforms to highlight savings if
> > needed.
> >
> > Anyways I'm not proud of the proposed change but merely wanted to see
> > with this RFC if there isn't any way to do further optimizations on the
> > __FILE__ topic that are not overly intrusive specifically as it comes to
> > SPL.
> 
> 
> Commit 1eb2e71edd55e16562e3912881c449db69623352
> was not enough to solve your problem.
> 
> Correct?

Correct. This is a great commit and I saw what all went into it and it
goes a long way in addressing the general concern and doing much needed
cleanup but I wanted to go beyond this.

Consider this example, if I use a WARN_ON() deep in the arch folder of
one of the SoCs, I would get this on the console...

	WARNING at arch/arm/mach-k3/am6_init.c:192/board_init_f()!

...and now, with the proposed change, it would boil down to this...

	WARNING at 192 at board_init_f()!


If we could just keep the base filename itself that would still be a
good size reduction, and keep the output somewhat consistent with the
original behavior, but I spent quite some time researching but without
some extreme "magic" there didn't seem to be an universal solution...


Also some additional background why I am even looking into this. One of
our platforms (AM335x) has a regression building on Travis CI with some
of our pending patches applied. Interestingly, this only happens on
Travis, which still uses GCC 7.3.0 for arm (why?). With newer, more
efficient compilers there is no such issue.

--
Andreas Dannenberg
Texas Instruments Inc