[PATCH, rs6000] Fix PR79044 (ICE in swap optimization)

[Bill Schmidt]

> On Jan 11, 2017, at 5:36 PM, Segher Boessenkool <segher@kernel.crashing.org> wrote:
> 
> On Tue, Jan 10, 2017 at 02:18:38PM -0600, Bill Schmidt wrote:
>> PR79044 reports a situation where swap optimization ICEs in GCC 6 and in trunk.  The
>> problem is that swap optimization doesn't properly recognize that element-reversing
>> loads and stores (e.g., lxvw4x) cannot be treated as "swappable" instructions.  These
>> arise from the __builtin_vec_xl and __builtin_vec_xst interfaces that were added in 
>> GCC 6.  The surrounding code is slightly different, so the fix is slightly different
>> for the two releases.
>> 
>> The fix is obvious, and bootstraps on powerpc64le-unknown-linux-gnu with no regressions.
>> Are these patches ok for trunk and GCC 6, respectively?
> 
> Okay for both.  Is this needed for GCC 5 as well?

No, the potential for this problem was introduced in 6.  Thanks for the review!

Bill

> 
> Thanks,
> 
> 
> Segher
>