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

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Message-ID: <5239BA2A-BCD9-4A8C-BC34-F48603137E08@mansr.com>
Date:	Sat, 21 Nov 2015 20:45:38 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Arnd Bergmann <arnd@...db.de>, Stephen Boyd <sboyd@...eaurora.org>
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, Nicolas Pitre <nico@...xnic.net>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi_{u}idiv library functions

On 21 November 2015 20:39:58 GMT+00:00, Arnd Bergmann <arnd@...db.de> wrote:
>On Friday 20 November 2015 17:23:14 Stephen Boyd wrote:
>> This is a respin of a patch series from about a year ago[1]. I
>realized
>> that we already had most of the code in recordmcount to figure out
>> where we make calls to particular functions, so recording where
>> we make calls to the integer division functions should be easy enough
>> to add support for in the same codepaths. Looking back on the thread
>> it seems like Mans was thinking along the same lines, although it
>wasn't
>> obvious to me back then or even over the last few days when I wrote
>this.
>
>Shouldn't we start by allowing to build the kernel for -march=armv7ve
>on platforms that allow it? That would seem like a simpler change
>and likely generate better code for most people, except when you
>actually
>care about running the same binary kernel on older platforms.
>
>I tried to get a complete list of CPU cores with idiv, lpae and
>virtualization support at some point, but I don't remember the
>details for all Qualcomm and Marvell cores any more, to create the
>complete configuration matrix. IIRC, all CPUs that support
>virtualization also do lpae (they have to) and all CPUs that
>do lpae also do idiv, but the opposite is not true.
>
>	Arnd

The ARM ARM says anything with virt has idiv, lpae doesn't matter. ARMv7-R also has idiv. I've no idea if anyone runs Linux on those though.
-- 
Måns Rullgård
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