[WinEHPrepare] Refactor explicit EH preparation

Split the preparation machinery into several functions, we will want to
selectively enable/disable different parts of it for an alternative
mechanism for dealing with cross-funclet uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247834 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed