generalize helper function of MergeConsecutiveStores to handle vector types (NFCI)

This was part of D7208 (r227242), but that commit was reverted because it exposed
a bug in AArch64 lowering. I should have that fixed and the rest of the commit
reinstated soon.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246493 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed