New EH representation for MSVC compatibility

Summary:
This introduces new instructions neccessary to implement MSVC-compatible
exception handling support.  Most of the middle-end and none of the
back-end haven't been audited or updated to take them into account.

Reviewers: rnk, JosephTremoulet, reames, nlewycky, rjmccall

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11041

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241888 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/BasicBlock.cpp

@@ -197,7 +197,7 @@ BasicBlock::iterator BasicBlock::getFirstInsertionPt() {
     return end();
 
   iterator InsertPt = FirstNonPHI;
-  if (isa<LandingPadInst>(InsertPt)) ++InsertPt;
+  if (InsertPt->isEHBlock()) ++InsertPt;
   return InsertPt;
 }