Re: [PATCH] PR target/38201: -mfma/-mavx and -msse5/-msse4a don't work together

[Uros Bizjak <ubizjak at gmail dot com>]

H.J. Lu wrote:
> Here is the updated patch for PR target/38201. I don't believe
> we should make arbitrary choices today for tomorrow's processors
> which we don't know anything about.  Disallow combination of
> -mfma/-mavx and -msse5/-msse4a won't prevent anyone from working on
> gcc to support any future processors.  We do have a concern that
> support for a new processor may take a long time to get into the
> released gcc.  To address this issue, we have been backporting new
> processor support to x86 vendor branches, which track released gcc,
> when needed.  I fullly expect those processors will be properly
> supported in gcc before they are launched. But arbitrary choices
> don't really help anyone and don't belong to a production compiler.
>
> OK for trunk?
>   

I think that this is wrong approach.

As can be seen from enhanced testcases, -mavx works well with *all* 
other -msseX flags. If there are problems with Intel and AMD version of 
FMA, we can solve this by -mtune or perhaps PTA flags in i386.c when 
both -msse5 and -mavx are selected..

Uros.