[X86] Change vXi1 extract_vector_elt lowering to be legal if the index is 0. Add DAG combine to turn scalar_to_vector+extract_vector_elt into extract_subvector.
We were lowering the last step extract_vector_elt to a bitcast+truncate. Change it to use an extract_vector_elt of index 0 instead. Add isel patterns to do the equivalent of what the bitcast would have done. Plus an isel pattern for an any_extend+extract to prevent some regressions.
Finally add a DAG combine to turn v1i1 scalar_to_vector+extract_vector_elt of 0 into an extract_subvector.
This fixes some of the regressions from D350800.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350918 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed