method, fixing a crash on PR4146. While the store will
ultimately overwrite the "padded size" number of bits in memory,
the stored value may be a subset of this size. This function
only wants to handle the case where all bits are stored.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71224 91177308-0d34-0410-b5e6-96231b3b80d8
