Re: mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'

[Ralf Baechle]

On Wed, Apr 20, 2016 at 01:44:28PM +0800, kbuild test robot wrote:

> FYI, the error/warning still remains.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   12566cc35d0e68308bde7aad615743d560cb097b
> commit: c1a0e9bc885d46e519fd87d35af6a7937abfb986 MIPS: Allow compact branch policy to be changed
> date:   6 months ago
> config: mips-malta_qemu_32r6_defconfig (attached as .config)
> reproduce:
>         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout c1a0e9bc885d46e519fd87d35af6a7937abfb986
>         # save the attached .config to linux build tree
>         make.cross ARCH=mips 
> 
> All errors (new ones prefixed by >>):
> 
> >> mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'
> >> mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'

-mcompact-branches=optimal is an option for the latest version of the MIPS
architecture which is enabled by mips-malta_qemu_32r6_defconfig but your
compiler is too old, doesn't support R6.  Unfortunately there's no simple
way to run a test on the build environment from kconfig or even before
kconfig runs so we've just ignord this particular build issue.  Plus
there being the additional issue that we only know the toolchain to be
used after certain options have been picked.

  Ralf