linux-kernel - Re: [kbuild-all] mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'

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Date:	Thu, 21 Apr 2016 12:51:29 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Ralf Baechle <ralf@...ux-mips.org>
Cc:	kbuild-all@...org, Paul Burton <paul.burton@...tec.com>,
	linux-kernel@...r.kernel.org, Philip Li <philip.li@...el.com>
Subject: Re: [kbuild-all] mipsel-linux-gnu-gcc: error: unrecognized command
 line option '-mcompact-branches=optimal'

Hi Ralf,

On Wed, Apr 20, 2016 at 03:30:21PM +0200, Ralf Baechle wrote:
> 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.

We are running Debian's mips cross compiler.

% mips-linux-gnu-gcc --version
mips-linux-gnu-gcc (Debian 5.2.1-16) 5.2.1 20150903
Copyright (C) 2015 Free Software Foundation, Inc.

How about temporarily disable that error, until we upgrade to a new
gcc version which supports the -mcompact-branches option?

Thanks,
Fengguang