Fix Issues with cmpxchg example

[Duncan P. N. Exon Smith via llvm-commits]

> On 2016-Feb-06, at 16:26, Daniel Robertson <danlrobertson89 at gmail.com> wrote:
> 
>> These things happen :).
> 
> Thanks
> 
>> LGTM.  Do you need someone to commit it for you?
> 
> Yeah, that would be great!

r260018