[PATCH, committed] Update GAS' -maltivec and -mvsx options to only enable the oldest version of their respective instruction sets

[Alan Modra]

On Wed, Mar 08, 2017 at 08:57:33PM -0600, Peter Bergner wrote:
> Update -maltivec and -mvsx options to only enable their oldest instructions.
> 
> Currently, the -maltivec and -mvsx GAS options enable *all* of the altivec
> and vsx instructions respecitively that have ever been added.  This is in
> constract to GCC's -maltivec and -mvsx options, which only enable the oldest
> (ie, first) set of altivec and vsx instructions.  This patch changes GAS to
> mimic GCC's behaviour with respect to -maltivec and -mvsx and it solves a
> problem with trying to assemble the lxvx instruction which is different
> between POWER8 and POWER9.

I've pushed this to the 2.28 and 2.27 branches as well.  2.27 failed a
couple of tests when using gcc-7, fixed by cherry-picking a
.gnu.attributes patch from 2016-09-26.

-- 
Alan Modra
Australia Development Lab, IBM