When performing a truncating store, it is sometimes possible to rearrange the

When performing a truncating store, it is sometimes possible to rearrange the
data in-register prior to saving to memory.  When we reorder the data in memory
we prevent the need to save multiple scalars to memory, making a single regular
store.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137238 91177308-0d34-0410-b5e6-96231b3b80d8