[U-Boot] [PATCH v4 2/2] arm: work around assembler bug

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Allen,

On Wed, 18 Jul 2012 16:45:53 -0700, Allen Martin <amartin@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@nvidia.com>
> ---
> changes for v4:
>  -removed warning print
> changes for v3:
>  -split shell line to improve readability
> changes for v2:
>  -changed GAS_BUG_12532 from yes/no to y/n to be consistent
>  -added additional warning about code size increase
> ---
>  arch/arm/config.mk |   18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> index 3f4453a..24b9d7c 100644
> --- a/arch/arm/config.mk
> +++ b/arch/arm/config.mk
> @@ -87,3 +87,21 @@ endif
>  ifndef CONFIG_NAND_SPL
>  LDFLAGS_u-boot += -pie
>  endif
> +
> +#
> +# FIXME: 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 [ $(call binutils-version) -lt 0222 ] ; \
> +	then echo y; else echo n; fi)
> +endif
> +ifeq ($(GAS_BUG_12532),y)
> +PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
> +endif
> +endif

Can previous reviewers ack or test this? I would like to have it in the ARM
master branch in time for 12.07.

Amicalement,
-- 
Albert.