Date: Thu, 21 Apr 2016 22:10:51 +0100
From: "Maciej W. Rozycki" <macro@imgtec.com>
To: Ralf Baechle <ralf@linux-mips.org>
CC: Fengguang Wu <fengguang.wu@intel.com>, <kbuild-all@01.org>,
        Paul Burton <paul.burton@imgtec.com>, <linux-kernel@vger.kernel.org>,
        Philip Li <philip.li@intel.com>
Subject: Re: [kbuild-all] mipsel-linux-gnu-gcc: error: unrecognized command
 line option '-mcompact-branches=optimal'
In-Reply-To: <20160421203415.GK24051@linux-mips.org>
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References: <201604201320.YHjfc2dZ%fengguang.wu@intel.com> <20160420133021.GG24051@linux-mips.org> <20160421045129.GB4038@wfg-t540p.sh.intel.com> <alpine.DEB.2.00.1604212043170.21846@tp.orcam.me.uk> <20160421203415.GK24051@linux-mips.org>
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On Thu, 21 Apr 2016, Ralf Baechle wrote:

> >  I don't think it makes sense as the compiler won't support MIPSr6 code 
> > anyway, so first it'll bail out on `-march=mips32r6', and if we go even 
> > further and disable that too, then GAS will probably break somewhere on 
> > inline asm and GCC will produce code which does not make sense otherwise.
> 
> GCC 5.2.0 claims to support mips32r6 and mips64r6.  It's just the option
> -mcompact-branches which seem to have been added later only.

 Ah, I see -- I didn't track the timeline of support for this compiler's 
option and I took it from an earlier response that the compiler does not 
support R6 at all.

 In that case however it looks to me like these `-mcompact-branches=' 
options (all the three we support) need to be wrapped into `$(call 
cc-option,...)'.  They do not affect any functionality and they are an 
optimisation choice only anyway (and therefore I wonder why they've been 
placed in arch/mips/Kconfig.debug rather than arch/mips/Kconfig).

  Maciej