[U-Boot] [PATCH] arm: prevent using movt/movw address loads

[Tom Rini]

On Sat, Aug 24, 2013 at 01:55:38PM +0200, Jeroen Hofstee wrote:

> The movt/movw instruction can be used to hardcode an
> memory location in the instruction itself. The linker
> starts complaining about this if the compiler decides
> to do so: "relocation R_ARM_MOVW_ABS_NC against `a local
> symbol' can not be used" and it is not support by U-boot
> as well. Prevent their use by requiring word relocations.
> This allows u-boot to be build at other optimalization
> levels then -Os.
> 
> Signed-off-by: Jeroen Hofstee <jeroen at myspectrum.nl>
> Cc: TigerLiu at viatech.com.cn
> Cc: Albert ARIBAUD <albert.u.boot at aribaud.net>
> ---
>  arch/arm/config.mk | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Is this also something we need for llvm?  I am hesitant here because as
Wolfgang points out, -O0 is usually the wrong way to debug a problem and
I'll add we're well into the age where debuggers work just fine with
optimized code.  If there's some -O2 enabled gcc flag we want because of
a measurable performance win, we should add it specifically to -Os.

-- 
Tom
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