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Re: -mcpu vs. binutils

To: Thiemo Seufer <>
Subject: Re: -mcpu vs. binutils
From: Guido Guenther <>
Date: Wed, 19 Mar 2003 00:24:54 +0100
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Mail-followup-to: Guido Guenther <>, Thiemo Seufer <>,
Original-recipient: rfc822;
References: <20030318154155.GF2613@bogon.ms20.nix> <> <20030318174241.GG2613@bogon.ms20.nix> <>
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Hi Thiemo,
thanks a lot for the explanations!

On Tue, Mar 18, 2003 at 08:08:41PM +0100, Thiemo Seufer wrote:
> This would be nice, but older compilers don't have -march/-mtune.
> IIRC gcc 3.0.X is the first one to employ these. Similiar for -mabi.
I don't care about old compilers at the moment ;)

> -mabi=FOO: 
> Produce, hosted on a multi ABI system, a userland binary with the lowest
> possible ISA for the selected ABI.
> Then there are optimizations for different CPUs.
> -march=BAR:
> Allow opcodes for CPU BAR in addition to the ISA ones.
> -mtune=BAZ:
> Optimize opcode scheduling for CPU BAZ.
So to build kernels for say IP22 R5k I'd change the current
        GCCFLAGS += -mcpu=r5000 -mips2 -Wa,--trap
        GCCFLAGS += -mabi=o32 -march=R5000 -mtune=R5000 -Wa,--trap
where as for R4X00 I use
        GCCFLAGS += -mabi=o32 -march=R4600 -mtune=R4600 -Wa,--trap
 -- Guido

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