This pass implements a simple algorithm for conversion from CFG to
wasm's structured control flow. It doesn't yet handle multiple-entry
loops; that will be added in a future patch.
It also adds initial support for switch statements.
Differential Revision: http://reviews.llvm.org/D12735
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247818 91177308-0d34-0410-b5e6-96231b3b80d8
