[AVX-512] Improve lowering of inserting a single element into lowest element of a 512-bit vector of zeroes by using vmovq/vmovd/vmovss/vmovsd.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277965 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed