[X86][MMX] Generlize MMX_MOVD64rr combines to accept v4i16/v8i8 build vectors as well as v2i32

Also handle both cases where the lower 32-bits of the MMX is undef or zero extended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325736 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed