[PATCH,rs6000] Add -maltivec={le,be} options

[David Edelsohn]

On Tue, Jan 7, 2014 at 6:59 PM, Bill Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> On Tue, 2014-01-07 at 22:18 +0000, Joseph S. Myers wrote:
>> On Tue, 7 Jan 2014, Bill Schmidt wrote:
>>
>> > Yes, sorry for not being more clear.  This is indeed for interpretation
>> > of element numbers in Altivec intrinsics such as vec_splat, vec_extract,
>> > vec_insert, and so forth.  By default these will match array element
>> > order for the target endianness.  But with -maltivec=be for a little
>> > endian target, we will force use of big-endian element order (matching
>> > the behavior of the underlying hardware instructions).
>>
>> Thanks for the explanation.  I think you should make the .texi
>> documentation say something more like this.
>>
>
> Sure, I can wordsmith something along those lines.  Thanks for the
> feedback!

This patch is okay with the documentation clarification requested by Joseph.

I also would suggest removing "but may be enabled in the future" from
the "le" option and limit the comment to ignored on big-endian
targets.

Also, please add a comment to -maltivec that it defaults to the native
endian order.  And for -maltivec=be, please state that this is the
default for big-endian; for -maltivec=le, please state that this is
the default for little-endian. It's important to be clear and
redundant in this type of documentation.

Thanks, David