linux-kernel - Re: [RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi

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Message-ID: <20151124104225.GA8644@n2100.arm.linux.org.uk>
Date:	Tue, 24 Nov 2015 10:42:26 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Stephen Boyd <sboyd@...eaurora.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Peter Maydell <peter.maydell@...aro.org>,
	Måns Rullgård <mans@...sr.com>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Christopher Covington <cov@...eaurora.org>
Subject: Re: [RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi_{u}idiv library
 functions

On Tue, Nov 24, 2015 at 11:38:53AM +0100, Arnd Bergmann wrote:
> I suggested using -mcpu=cortex-a15 because there are old gcc versions
> that don't know about -march=armv7ve or -march=armv7-a+idiv yet, but
> that do understand -mcpu=cortex-a15.

That's not all.  The bigger problem is that there are toolchains out
there which accept these options, but do _not_ support IDIV in either
ARM or Thumb mode.  I'm afraid that makes it impossible to add this
feature to the mainline kernel in this form: we need to run a test
build to check that -march=armv7ve or what-not really does work
through both GCC and GAS.

Given that Ubuntu 14.04 LTS suffers with this, it's something that
must be resolved.

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