[PTX] atomics compare exchange

[Nathan Sidwell]

I noticed the atomic compare exchange was using 'and 1' to generate a bool.  We 
now have select, which makes it more obvious.

Sadly  the middle end's expansion of of the builtin fails to make use of the 
condition we just generated directly, instead generating a new one from the bool.

nathan
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ptx-atomic.patch
Type: text/x-patch
Size: 1117 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/gcc-patches/attachments/20150909/b481a6b5/attachment.bin>