[X86] Add gather test with index sign extended from i8 type.

Previously SelectionDAGBuilder would remove this sign extend leading to a failure during isel.

The codegen here isn't very nice as we ended up triggering a split.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318467 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed