linux-kernel - Re: [PATCH v2] ARM: Use udiv/sdiv for __aeabi

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Date:	Sat, 09 Nov 2013 18:20:38 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Matt Sealey <neko@...uhatsu.net>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Christopher Covington <cov@...eaurora.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Måns Rullgård 
	<mans@...sr.com>, Rob Herring <robherring2@...il.com>
Subject: Re: [PATCH v2] ARM: Use udiv/sdiv for __aeabi_{u}idiv library functions

Matt Sealey <neko@...uhatsu.net> writes:

> BTW has there been any evaluation of the penalty for the extra
> branching, or the performance hit for the ARMv7-without-division
> cases?

The branches themselves probably have minimal overhead.  There will
however be code to preserve call-clobbered registers (and move the
values to/from r0/r1) that would not be needed if the div instructions
were done inline (obviously such a kernel could only run on hardware
with division support).

-- 
Måns Rullgård
mans@...sr.com
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