We do this mostly to be able to test the insert_vector_elt isel patterns. As long as we don't, most single element insertions show up as `BUILD_VECTOR` in the backend. Reviewed By: kaz7 Differential Revision: https://reviews.llvm.org/D93759
Isel and tests for extract_vector_elt and insert_vector_elt. Reviewed By: kaz7 Differential Revision: https://reviews.llvm.org/D93687