Vectors were being manually scalarized by the backend. Instead,
let the target-independent code do all of the work. The manual
scalarization was from a time before good target-independent support
for scalarization in LLVM. However, this forces us to specially-handle
vector loads and stores, which we can turn into PTX instructions that
produce/consume multiple operands.
llvm-svn: 174968
be8dc6499a