Revert "[ms-cxxabi] Add a new calling convention that swaps 'this' and 'sret'"

This reverts commit r200561.

This calling convention was an attempt to match the MSVC C++ ABI for
methods that return structures by value.  This solution didn't scale,
because it would have required splitting every CC available on Windows
into two: one for methods and one for free functions.

Now that we can put sret on the second arg (r208453), and Clang does
that (r208458), revert this hack.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208459 91177308-0d34-0410-b5e6-96231b3b80d8
SLPVectorizer: When sorting by domination for CSE don't assert on unreachable code.

There is no total ordering if the CFG is disconnected. We don't care if we
catch all CSE opportunities in dead code either so just exclude ignore them in
the assert.

PR19646

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208461 91177308-0d34-0410-b5e6-96231b3b80d8