[SelectionDAG]  Consider endianness in scalarizeVectorStore().

When handling vectors with non byte-sized elements, reverse the order of the
elements in the built integer if the target is Big-Endian.

SystemZ tests updated.

Review: Eli Friedman, Ulrich Weigand.
https://reviews.llvm.org/D42786

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324063 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed