[U-Boot] [PATCH 2/2] arm: work around assembler bug

[Albert ARIBAUD]

Hi Graeme and Allen,

On Tue, 10 Jul 2012 15:13:47 +1000, Graeme Russ <graeme.russ at gmail.com> wrote:
> Hi Martin,
> 
> On Tue, Jul 10, 2012 at 3:08 PM, Allen Martin <amartin at nvidia.com> wrote:
> > Disable sibling call optimization based on binutils version.  This is
> > to work around a bug in the assember in binutils versions < 2.22.
> > Branches to weak symbols can be incorrectly optimized in thumb mode to
> > a short branch (b.n instruction) that won't reach when the symbol gets
> > preempted.
> >
> > http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> >
> > Signed-off-by: Allen Martin <amartin at nvidia.com>
> > ---
> >  arch/arm/config.mk |   20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >
> > diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> > index 3f4453a..1ba9d75 100644
> > --- a/arch/arm/config.mk
> > +++ b/arch/arm/config.mk
> > @@ -87,3 +87,23 @@ endif
> >  ifndef CONFIG_NAND_SPL
> >  LDFLAGS_u-boot += -pie
> >  endif
> > +
> > +#
> > +# binutils versions < 2.22 have a bug in the assembler where branches
> > +# to weak symbols can be incorrectly optimized in thumb mode to a
> > +# short branch (b.n instruction) that won't reach when the symbol
> > +# gets preempted
> > +#
> > +# http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> > +#
> > +ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
> > +ifeq ($(GAS_BUG_12532),)
> > +export GAS_BUG_12532:=$(shell if [ $(call binutils-version) -lt 0222 ] ; then echo yes; else echo no; fi)
> 
> y instead of yes
> 
> > +ifeq ($(GAS_BUG_12532),yes)
> 
> So:
> 
> ifeq ($(GAS_BUG_12532),y)
> 
> is more consistent
> 
> > +$(warning *** disabling sibling call optimzation because binutils version < 2.22)
> 
> Maybe add 'code size will be (slightly) larger'

"could be" rather than "will be" ?

> 
> > +endif
> > +endif
> > +ifeq ($(GAS_BUG_12532),yes)
> > +PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
> > +endif
> > +endif
> > --
> > 1.7.9.5
> >

If a new patch version is out and Tested-by: soon, I am willing to take this in.

> Regards,
> 
> Graeme

Amicalement,
-- 
Albert.