[Bug c++/80652] Union conversion between __m128d and double array does not work under 5.0 through 6.2

[paboyle at ph dot ed.ac.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80652

--- Comment #3 from Peter Boyle <paboyle at ph dot ed.ac.uk> ---
Can confirm (5.4) that -O2 also fails, 
                       -O1 passes.