Improve test to actually check for a folded load.

Improve test to actually check for a folded load.

This test was checking for lack of a "movaps" (an aligned load)
rather than a "movups" (an unaligned load). It also included
a store which complicated the checking.

Add specific CPU runs to prevent subtarget feature flag overrides
from inhibiting this optimization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227972 91177308-0d34-0410-b5e6-96231b3b80d8