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

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Message-ID: <20131108165437.GM16735@n2100.arm.linux.org.uk>
Date:	Fri, 8 Nov 2013 16:54:37 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Rob Herring <robherring2@...il.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: Use udiv/sdiv for __aeabi_{u}idiv library
	functions

On Fri, Nov 08, 2013 at 12:50:04PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 19:34 Thu 07 Nov     , Rob Herring wrote:
> > On Thu, Nov 7, 2013 at 1:20 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> > > If we're running on a v7 ARM CPU, detect if the CPU supports the
> > > sdiv/udiv instructions and replace the signed and unsigned
> > > division library functions with an sdiv/udiv instruction.
> > 
> > [snip]
> > 
> > > diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
> > > index bd454b0..6ed6496 100644
> > > --- a/arch/arm/lib/Makefile
> > > +++ b/arch/arm/lib/Makefile
> > > @@ -15,6 +15,9 @@ lib-y         := backtrace.o changebit.o csumipv6.o csumpartial.o   \
> > >                    io-readsb.o io-writesb.o io-readsl.o io-writesl.o  \
> > >                    call_with_stack.o
> > >
> > > +lib-$(CONFIG_CPU_V7) += div-v7.o
> > > +CFLAGS_div-v7.o := -march=armv7-a
> > 
> > Won't this fail to build if the compiler doesn't have armv7-a support.
> > Perhaps we don't care about compilers that old.
> 
> use the propoer compiler to compile a armv7 kernel

It's probably about time to get rid of the conditionals for this in
the main arch/arm/Makefile actually - some of those date back some
10 or so years.  That's something for the v3.14 merge window.
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