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Date:      Tue, 09 Apr 2002 01:20:23 +0200
From:      Michael Nottebrock <michaelnottebrock@gmx.net>
To:        Peter Leftwich <Hostmaster@Video2Video.Com>
Cc:        FreeBSD Questions <FreeBSD-Questions@FreeBSD.ORG>, FreeBSD Ports <FreeBSD-Ports@FreeBSD.ORG>
Subject:   Re: gcc -O -mcpu=i686 -howtooverride=486?
Message-ID:  <3CB225B7.4090405@gmx.net>
References:  <20020408140315.J8518-100000@66-75-1-142.san.rr.com>

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Peter Leftwich wrote:
> My question is the following-- It seems like my /etc/make.conf file (which
> I think I either mv'ed or cp'ed from /usr/local/etc/make.conf) is getting
> ignored as far as the "CPUTYPE=i686" flag goes.  How do I remedy this?
> 
> I have been editing the various "Makefile" files, overriding the usual "-O
> -m486" with "-O -mcpu=i686" (what is -march by the way?) but my extended
> question is the following-- Does the -mcpu flag that mean [paraphrase-ically]
> "use i686 instructions for the compile process" or does it mean "compile
> some binaries with i686 smartness built into them?"  Know-whuht-eye-mean?

CPUTYPE= sets -march, not mcpu.

 From the gcc documentation (i386-specific):

----snip

-mcpu=cpu type
     Assume the defaults for the machine type cpu type when scheduling 
instructions. The choices for cpu type are:

     `i386' `i486' `i586' `i686'
     `pentium' `pentiumpro' `k6'

     While picking a specific cpu type will schedule things 
appropriately for that particular chip, the compiler will not generate 
any code that does not run on the i386 without the `-march=cpu type' 
option being used. `i586' is equivalent to `pentium' and `i686' is 
equivalent to `pentiumpro'. `k6' is the AMD chip as opposed to the Intel 
ones.

-march=cpu type
Generate instructions for the machine type cpu type. The choices for cpu 
type are the same as for `-mcpu'. Moreover, specifying `-march=cpu type' 
implies `-mcpu=cpu type'

----snip

-- 
Michael Nottebrock


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