SLPVectorizer: Use properlyDominates to satisfy the irreflexivity of a strict weak ordering.

STL debug mode checks this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194015 91177308-0d34-0410-b5e6-96231b3b80d8
Check for both styles of clobbers, those produced by dragonegg and
those produced by clang for the inline asm bswap conversion.

Modified from a patch by Chris Smowton.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194016 91177308-0d34-0410-b5e6-96231b3b80d8
Remove dead code

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194017 91177308-0d34-0410-b5e6-96231b3b80d8