AVX-512: Optimized INSERT_SUBVECTOR for i1 vector types

ISERT_SUBVECTOR for i1 vectors may be done with shifts, when we insert into the lower part, or into the upper part, on into all-zero vector.
CONCAT_VECTORS uses ISERT_SUBVECTOR.

Differential Revision: http://reviews.llvm.org/D14815



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253819 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed