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Date: Mon, 20 Oct 2014 21:41:58 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: Error with gcc-4.9.1 on MacOS 10.9.5

On Mon, Oct 20, 2014 at 05:52:11PM +0200, magnum wrote:
> Did you not get this message from ./configure?
> 
> configure: WARNING: **************************************************
> configure: WARNING: * System's 'as' can't assemble AVX instructions. *
> configure: WARNING: * Fixing this may yield better performance.      *
> configure: WARNING: * See last section of doc/INSTALL                *
> configure: WARNING: **************************************************

I guess you're asking Erik, but:

BMI is not (part of) AVX.  BMI is newer than AVX.  It is possible that
Erik's assembler supports AVX, but not BMI, and in this case there's no
reason to disable use of AVX just because BMI is not supported.

> >We'll keep seeing this problem in various contexts, for various
> >instruction set extensions on various archs, as long as we use the
> >-march=native option to gcc.  There's no good solution.  Maybe we need a
> >documented workaround, though - e.g., "remove -march=native or replace
> >it with a specific option requesting an older architecture revision such
> >as -mavx, or upgrade your assembler".  Maybe we need a configure option
> >disabling use of -march=native, or do we already have that?  magnum?
> 
> We have that too. IIRC --disable-native-macro turns off -march=native 
> and --disable-native-tests turns off all auto-probing so you can specify 
> custom CFLAGS however you want. But that 'as' wrapper script should be 
> the best solution in this case.

Great.

Alexander

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