linux-kernel - Re: [PATCH] ARM: add a private asm/unaligned.h

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Message-ID: <20171030171353.GD27404@n2100.armlinux.org.uk>
Date:   Mon, 30 Oct 2017 17:13:53 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Robert Jarzmik <robert.jarzmik@...e.fr>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrea Adami <andrea.adami@...il.com>,
        Gregory CLEMENT <gregory.clement@...e-electrons.com>,
        Romain Izard <romain.izard.pro@...il.com>,
        Sven Schmidt <4sschmid@...ormatik.uni-hamburg.de>,
        Petr Cvek <petrcvekcz@...il.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: add a private asm/unaligned.h

On Mon, Oct 30, 2017 at 06:01:44PM +0100, Arnd Bergmann wrote:
> Right, either fail the build or use the workaround from the gcc bugzilla,
> passing -fno-store-merging to the broken compilers avoids the problem
> reliably at the cost of slightly worse code. For the decompressor, we might
> also get away with passing -march=armv5t (not armv5te), which has
> experimentally been found to avoid the problem and produce better code
> than "-march=armv6 -fno-store-merging" as it avoids the strd instruction
> but not other store merging.

Depends how important the compilers are...

We currently refuse to build using these compilers:

gcc = 3.x where x < 3
gcc = 4.x where x < 3 if unwinding is enabled
gcc = 4.8.x where x < 3

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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