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

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Message-ID: <20151122194704.GJ8644@n2100.arm.linux.org.uk>
Date:	Sun, 22 Nov 2015 19:47:05 +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 08:25:27PM +0100, Arnd Bergmann wrote:
> The question is really about Marvell Dove, MMP and Armada 370,
> which are all based on PJ4 or PJ4B (CPU part : 0x581), so ARMv7-A
> and report idivt support but idiva.

Well, it's pretty hard to test when binutils blocks your ability to
write assembly using the instructions.

root@...ox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='cortex-a9+idiv' -marm
/tmp/cc8WPQiB.s: Assembler messages:
/tmp/cc8WPQiB.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-a9+idiv' -mthumb
/tmp/ccRzgAlM.s: Assembler messages:
/tmp/ccRzgAlM.s:36: Error: selected processor does not support Thumb mode `udiv r6,r5,r4'
root@...ox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='marvell-pj4+idiv' -mthumb
/tmp/cc1JYyFD.s: Assembler messages:
/tmp/cc1JYyFD.s:36: Error: selected processor does not support Thumb mode `udiv r6,r5,r4'
root@...ox:~# gcc -O2 -o idiv idiv.c -Wa,-mcpu='marvell-pj4+idiv' -marm
/tmp/ccEQbQpp.s: Assembler messages:
/tmp/ccEQbQpp.s:32: Error: selected processor does not support ARM mode `udiv ip,r5,r4'

That's binutils 2.24 and gcc 4.8.4 as found on Ubuntu 14.04.  I'm
sorry, but I don't have spare time to work out what the opcodes
would be.

-- 
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according to speedtest.net.
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