[U-Boot] [RFC][PATCH] ARMV7: Patch to fix hard float build issues

[Albert ARIBAUD]

Le 18/02/2011 16:16, Raghuveer Murthy a écrit :
> U-boot built for MeeGo on PandaBoard, with compiler option
> -mfloat-abi=hard, caused a build break. Please refer to the bug id:
>
> http://bugs.meego.com/show_bug.cgi?id=13140

Is this the official U-Boot? Why is it still at 2010.09 ?

> Removing the -msoft-float options in the config.mk files, allowed it
> to be built for both armv7hl and armv7el compilers on MeeGo
>
> Please refer to the below link for more details:
> http://wiki.meego.com/SDK/Toolchains/ToolchainChangeProposal
>
> Signed-off-by: Raghuveer Murthy<raghuveer.murthy at ti.com>

I would like to know which board of mainline U-boot is affected by the 
issue and how I can reproduce it on u-boot[-arm]/master.

However, I can already tell that this 'bug' can only occur upon a mix of 
object files compiled with -msoft-float and -mhard-float; which means 
some files were compiled with -mhard-float; and this should not happen 
at all, since U-Boot should not use any floats at all, so:

- either some files in the case reported were compiled voluntarily with 
hard-float, and this is not a generally supported use case of U-Boot;

- or they were compiled without any float option and the toolchain 
defaulted to hard-float, which may be a meego but is no reason in itself 
for U-Boot to adapt to it.

My feeling at the moment is that U-Boot should keep -msoft-float, to be 
sure that any float code present in the code base, if it has to be, will 
run regardless of hw floating point capabilities, because U-Boot 
binaries should make the least possible assumptions on the hardware they 
are running on.

Now, CPUs/SoCs/boards that know they have a floating point unit may 
justly want to replace -msoft-float with -mhard-float everywhere 
throughout U-Boot; I would welcome a patch that allows U-Boot to default 
to soft float while allowing CPUs/SoCs/boards to override it for hard float.

In no case, however, should -msoft-float be *removed*: that would make 
float support in U-Boot implicit and dependent on the toolchain in use, 
and I think U-Boot float support should always be explicit and not 
depend on the toolchain.

Amicalement,
-- 
Albert.