linux-kernel - Re: [PATCH 1/3] ARC: allow to overide default mcpu compiler flag

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Message-ID: <c1dee77e-f8e3-1213-61a9-390412bfb5ee@synopsys.com>
Date:   Fri, 29 May 2020 20:47:17 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...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>,
        "Alexey Brodkin" <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH 1/3] ARC: allow to overide default mcpu compiler flag

On 5/29/20 4:55 AM, Eugeniy Paltsev wrote:
> By default we set -mcpu=xxx compiler flag depending on the CPU ISA
> version. It's good starting point, however that may be not enough
> as for some platforms we may want to use some specific 'mcpu'
> options for better optimization or to workaround HW issues.
> 
> We are going to use this option for HSDK-4xD board support.
> In addition it also allows to awoid patching 'mcpu' in ARC Makefile
> when we building Linux for some non-standard simulation or FPGA-based
> platforms.
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>

Question: So now if I build in buildroot with -mhs38_linux, it will use hard float
(kernel should not use floating point) but the libgcc linked will be different too
and that should be OK ?

I've rewritten the changelog.

  kernel builds set their own default -mcpu for a given ISA build.
  But that gets in the way of "custom" -mcpu flags from propagating
  into kernel build.

  This will also be used in next patches for HSDK-4xD board support which
  uses a different -mcpu to effect dual issue scheduling.