Vectorize a reduction chain feeding into a 'return' statement.
e.x 
return (a[0]+b[0]) + (a[1]+b[1])

Differential Revision: http://reviews.llvm.org/D6227



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222364 91177308-0d34-0410-b5e6-96231b3b80d8