getFirstInsertionPt() returns an iterator to the first insertion point in a
basic block. This is after all PHIs and any other instruction which is required
to be at the top of the basic block (like LandingPadInst).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137744 91177308-0d34-0410-b5e6-96231b3b80d8