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

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Message-ID: <20151122200326.GK8644@n2100.arm.linux.org.uk>
Date:	Sun, 22 Nov 2015 20:03:26 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Peter Maydell <peter.maydell@...aro.org>,
	Måns Rullgård <mans@...sr.com>,
	Nicolas Pitre <nico@...xnic.net>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	arm-mail-list <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi_{u}idiv library
 functions

On Sun, Nov 22, 2015 at 08:58:08PM +0100, Arnd Bergmann wrote:
> does it work with -mcpu=cortex-a15?  I've tried crosstool as versions
> 2.23.52.20130913, 2.24.0.20141017 and 2.25.51.20150518, and they
> all seem to behave as expected, failing with -mcpu=cortex-a9 and
> marvell-pj4 but succeeding with -mcpu=cortex-a15 or marvell-pj4+idiv.

Appears not:

root@...ox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='cortex-a15+idiv' -marm
/tmp/ccSovg32.s: Assembler messages:
/tmp/ccSovg32.s:32: Error: selected processor does not support ARM mode `udiv ip,r5,r4'
root@...ox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='cortex-a15+idiv' -mthumb
/tmp/cchbT3EE.s: Assembler messages:
/tmp/cchbT3EE.s:36: Error: selected processor does not support Thumb mode `udiv r6,r5,r4'

Same without the +idiv.

> I've also found some /proc/cpuinfo output to cross-reference SoCs
> to their core names.
> 
> 		variant	part	revision	name		features
> mmp2:		0	0x581	5		PJ4		idivt
> dove:		0	0x581	5		PJ4		idivt

Yes, that agrees with my dove.

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