[WinEHPrepare] Add rudimentary support for the new EH instructions

This adds somewhat basic preparation functionality including:
- Formation of funclets via coloring basic blocks.
- Cloning of polychromatic blocks to ensure that funclets have unique
  program counters.
- Demotion of values used between different funclets.
- Some amount of cleanup once we have removed predecessors from basic
  blocks.
- Verification that we are left with a CFG that makes some amount of
  sense.

N.B. Arguments and numbering still need to be done.

Differential Revision: http://reviews.llvm.org/D11750

llvm-svn: 244558

llvm/lib/Transforms/Utils/DemoteRegToStack.cpp

@@ -135,7 +135,7 @@ AllocaInst *llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) {
   // Insert a load in place of the PHI and replace all uses.
   BasicBlock::iterator InsertPt = P;
 
-  for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt)
+  for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
     /* empty */;   // Don't insert before PHI nodes or landingpad instrs.
 
   Value *V = new LoadInst(Slot, P->getName()+".reload", InsertPt);