[InstCombine] add more tests for shuffle-binop folds; NFC

The mul+shl tests add coverage for the fold enabled with D48678.
The and+or tests are not handled yet; that's D48662.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335984 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed