Previously we were abandonning the attempt, leading to some combination of
extra work (when selection of a load/store fails completely) and inferior code
(when this leads to a real memcpy call instead of inlining).
rdar://problem/17187463
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210520 91177308-0d34-0410-b5e6-96231b3b80d8