[U-Boot] Missing __udivdi3 for ARM

Wolfgang Denk wd at denx.de
Sun Aug 2 10:27:32 CEST 2009

Dear Dirk Behme,

In message <4A753DB9.6080508 at googlemail.com> you wrote:
> > But libgcc.a fo ARM is obviously not perfect, and causes problems. So
> > Jean-Christophe suggested to use the  alternative  implementation  he
> > wanted to copy from the Linux code - which again is supposed to allow
> > to use the code in question without changes.
> Just to get an idea what has to be done for this:
> Do we talk about
> http://lists.denx.de/pipermail/u-boot/2009-June/054627.html
> without the changes to top level
> Makefile
> arm_config.mk

Right. The patch needs to be updated so that the new runtime library
functions replace the existing ones and get linked into
lib_arm/libgcc.a instead.

> That is, updating that patch and removing the Makefile and 
> arm_config.mk changes would be what we want?

That's what Jean-Christphe proposed - I am not in a position to judge
if this really solves all the problems we have on ARM. Looking at the
code I see things like:

	+ * linux/arch/arm/lib/lib1funcs.S: Optimized ARM division routines
	+ *
	+ * Author: Nicolas Pitre <nico at cam.org>
	+ *   - contributed to gcc-3.4 on Sep 30, 2003
	+ *   - adapted for the Linux kernel on Oct 2, 2003

That reads as if this was 6 years old code, which looks as if it  was
two years older than what we currently have in U-Boot.

I wonder if it would not make more sense to copy the C code from some
recent GCC version instead - it may be a few percent  less  efficient
in  terms  of  size and performance, but looking where such reoutines
are actually used in U-Boot I thinl probably nobody would ever notice
the difference.

So probably someone with a deeper understanding of GCC support for ARM
is required to make a qualified assessment, and in any case thorogh
testing needs to be done.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Hi there! This is just a note from me, to you, to tell you, the  per-
son  reading this note, that I can't think up any more famous quotes,
jokes, nor bizarre stories, so you may as well go home.

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