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Re: GCCFLAGS for gcc 3.3.x (-march and _MIPS_ISA)

To: linux-mips@linux-mips.org
Subject: Re: GCCFLAGS for gcc 3.3.x (-march and _MIPS_ISA)
From: Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>
Date: Tue, 19 Aug 2003 08:41:18 +0200
In-reply-to: <20030819035756.GC6223@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20030812.152654.74756131.nemoto@toshiba-tops.co.jp> <20030812065118.GD23104@rembrandt.csv.ica.uni-stuttgart.de> <20030819035756.GC6223@linux-mips.org>
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Ralf Baechle wrote:
> On Tue, Aug 12, 2003 at 08:51:18AM +0200, Thiemo Seufer wrote:
> 
> > >   GCCFLAGS += -mabi=32 -march=mips2 -mtune=r4600 -Wa,--trap
> > > (or       GCCFLAGS += $(call check_gcc, -mcpu=r4600 -mips2, -mabi=32 
> > > -march=mips2 -mtune=r4600) -Wa,--trap)
> > > 
> > > Isn't it?
> > 
> > -march=mips2 is an alias for -march=r6000, I don't think that's a
> > good choice.
> 
> Why? MIPSII / MIPS32 are the highest ISAs supported for building 32-bit
> kernels so that makes sense.

Because you get only MIPS II instructions then. This doesn't matter
much for R4600, but the improvements of later ISAs won't be used.

-mabi=32 -march=r4600 works for 32bit kernels with newer toolchains,
there's no need to use -mtune separately.


Thiemo

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