[AVX-512] Remove patterns that select vmovdqu8/16 for unmasked loads. Prefer...

[AVX-512] Remove patterns that select vmovdqu8/16 for unmasked loads. Prefer vmovdqa64/vmovdqu64 instead.

These were taking priority over the aligned load instructions since there is no vmovda8/16. I don't think there is really a difference between aligned and unaligned on newer cpus so I don't think it matters which instructions we use.

But with this change we reduce the size of the isel table a little and we allow the aligned information to pass through to the evex->vec pass and produce the same output has avx/avx2 in some cases.

I also generally dislike patterns rooted in a bitcast which these were.

Differential Revision: https://reviews.llvm.org/D35977

llvm-svn: 309589