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

llvm-svn: 241888
diff --git a/llvm/lib/Transforms/Scalar/BDCE.cpp b/llvm/lib/Transforms/Scalar/BDCE.cpp
index 09c605e..e484069 100644
--- a/llvm/lib/Transforms/Scalar/BDCE.cpp
+++ b/llvm/lib/Transforms/Scalar/BDCE.cpp
@@ -77,8 +77,8 @@
                     false, false)
 
 static bool isAlwaysLive(Instruction *I) {
-  return isa<TerminatorInst>(I) || isa<DbgInfoIntrinsic>(I) ||
-         isa<LandingPadInst>(I) || I->mayHaveSideEffects();
+  return isa<TerminatorInst>(I) || isa<DbgInfoIntrinsic>(I) || I->isEHBlock() ||
+         I->mayHaveSideEffects();
 }
 
 void BDCE::determineLiveOperandBits(const Instruction *UserI,