[X86][AVX] EltsFromConsecutiveLoads - Add BROADCAST lowering support

This patch adds scalar/subvector BROADCAST handling to EltsFromConsecutiveLoads.

It mainly shows codegen changes to 32-bit code which failed to handle i64 loads, although 64-bit code is also using this new path to more efficiently combine to a broadcast load.

Differential Revision: https://reviews.llvm.org/D58053

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354340 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed