[Buildroot] [PATCH] toolchain-wrapper: use -ffp-contract=off on MIPS Xburst for gcc >= 4.6

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello,

On Sat, 31 Mar 2018 19:54:20 +0200, Thomas Petazzoni wrote:
> From: Waldemar Brodkorb <wbx@openadk.org>
> 
> Since gcc 4.6, GCC deprecated -mfused-madd, -ffp-contract=off should
> be used for the Xburst workaround.
> 
> Tested with the MIPS Sourcery 2011.03 toolchain (based on gcc 4.5),
> the toolchain wrapper uses -mno-fused-madd, as expected:
> 
> $ BR2_DEBUG_WRAPPER=2 ./output/host/bin/mips-linux-gnu-gcc -o toto toto.c
> Toolchain wrapper executing:
>     '/home/thomas/toolchains/mips-2011.03/bin/mips-linux-gnu-gcc'
>     '--sysroot'
>     '/home/thomas/projets/buildroot/output/host/mipsel-buildroot-linux-gnu/sysroot'
>     '-mabi=32'
>     '-msoft-float'
>     '-mno-fused-madd'
>     '-EL'
>     '-march=mips32r2'
>     '-o'
>     'toto'
>     'toto.c'
> 
> And with the MIPS Sourcery 2012.09 toolchain (based on gcc 4.7), the
> toolchain wrapper uses -ffp-contract=off, as expected:
> 
> $ BR2_DEBUG_WRAPPER=2 ./output/host/bin/mips-linux-gnu-gcc -o toto toto.c
> Toolchain wrapper executing:
>     '/home/thomas/toolchains/mips-2012.09/bin/mips-linux-gnu-gcc'
>     '--sysroot'
>     '/home/thomas/projets/buildroot/output/host/mipsel-buildroot-linux-gnu/sysroot'
>     '-mabi=32'
>     '-msoft-float'
>     '-ffp-contract=off'
>     '-EL'
>     '-march=mips32r2'
>     '-o'
>     'toto'
>     'toto.c'
> 
> Fixes the ci20_defconfig build:
> 
>   https://gitlab.com/buildroot.org/buildroot/-/jobs/60303132
> 
> Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
> [Thomas: rework to continue supporting pre-gcc-4.6 toolchains, extend
> the commit log after doing more testing.]
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> ---
>  toolchain/toolchain-wrapper.c  | 3 +++
>  toolchain/toolchain-wrapper.mk | 6 ++++++
>  2 files changed, 9 insertions(+)

Applied to master, thanks.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com