[WinEH] Create a separate MBB for funclet prologues

Our current emission strategy is to emit the funclet prologue in the
CatchPad's normal destination.  This is problematic because
intra-funclet control flow to the normal destination is not erroneous
and results in us reevaluating the prologue if said control flow is
taken.

Instead, use the CatchPad's location for the funclet prologue.  This
correctly models our desire to have unwind edges evaluate the prologue
but edges to the normal destination result in typical control flow.

Differential Revision: http://reviews.llvm.org/D13424

llvm-svn: 249483

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index d718ede35cd..a7f5ba1269e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -216,14 +216,17 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
     // are really data, and no instructions can live here.
     if (BB->isEHPad()) {
       const Instruction *I = BB->getFirstNonPHI();
+      // FIXME: Don't mark SEH functions without __finally blocks as having
+      // funclets.
       if (!isa<LandingPadInst>(I))
         MMI.setHasEHFunclets(true);
-      if (isa<CatchPadInst>(I) || isa<CatchEndPadInst>(I) ||
-          isa<CleanupEndPadInst>(I)) {
+      if (isa<CatchEndPadInst>(I) || isa<CleanupEndPadInst>(I)) {
         assert(&*BB->begin() == I &&
                "WinEHPrepare failed to remove PHIs from imaginary BBs");
         continue;
       }
+      if (isa<CatchPadInst>(I) || isa<CleanupPadInst>(I))
+        assert(&*BB->begin() == I && "WinEHPrepare failed to demote PHIs");
     }
 
     MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);