[CostModel][AArch64] Add cost tests for ALTERNATE/SELECT style shuffle masks

Precursor to fixing a regression with SLP vectorizer for supporting SELECT shuffles (vs the current ALTERNATE)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334714 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed