linux-kernel - Re: [PATCH] arc: Remove sometimes misleading toolchain check

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Date:   Wed, 7 Jun 2017 16:35:50 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arc: Remove sometimes misleading toolchain check

Hi Vineet,

On Wed, 2017-06-07 at 09:33 -0700, Vineet Gupta wrote:
> On 05/25/2017 10:24 AM, Alexey Brodkin wrote:
> > 
> > Thinking of a toolchains for ARCompact and ARCv2 ISAs we implicitly
> > think about libgcc.a build for one of those ISAs which we're linking
> > with. And given there's no multiarch uClibc toolchain for ARC
> > (as probably for any other architecture) the assumption is the only way
> > to get libgcc.a for desired ISA is from a toolchain built right for that
> > same ISA.
> > 
> > So what we do we check what's GCC's default architecture ARC700 or not.
> > But generally speaking default arch makes not a lot of sense if explicit
> > command line option exist like "-mcpu=archs". In other words exactly the
> > same GCC might build executables for both ARC700 and ARC HS38.
> > 
> > But in real life libgcc could be easily built on a separate step
> > independently of the compiler and friends. And that really happens.
> > 
> > For example OpenEmbedded prefers to reuse the same toolchain for both
> > arches having libgcc built separately.
> 
> So this is a goodness of OE. But unfortunately those of living with simpler build 
> systems: Synopsys toolchain scripts or even Buildroot don't have this - right ?
> 
> So how will it help other developers avoid errors in the work flow when doing 
> kernel builds for ARCompact and ARCv2.
> 
> The right solution is to kill off the libgcc dependency altogether form kernel. 
> Just import math emulation code that we think is needed and build it in kernel !

Right and that's on my todo list as I'm suffering the most from this issue now :)

-Alexey