[SEH] Ensure that empty __except blocks have their own BB

The 32-bit lowering assumed that WinEHPrepare had this invariant.
WinEHPrepare did it for C++, but not SEH. The result was that we would
insert calls to llvm.x86.seh.restoreframe in normal basic blocks, which
corrupted the frame pointer.

llvm-svn: 241699

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86WinEHState.cpp b/llvm/lib/Target/X86/X86WinEHState.cpp
index 0b88d7a..3a8bcaa 100644
--- a/llvm/lib/Target/X86/X86WinEHState.cpp
+++ b/llvm/lib/Target/X86/X86WinEHState.cpp
@@ -520,6 +520,11 @@ void WinEHStatePass::addSEHStateStores(Function &F, MachineModuleInfo &MMI) {
           for (auto &Handler : ActionList) {
             if (auto *CH = dyn_cast<CatchHandler>(Handler.get())) {
               auto *BA = cast<BlockAddress>(CH->getHandlerBlockOrFunc());
+#ifndef NDEBUG
+              for (BasicBlock *Pred : predecessors(BA->getBasicBlock()))
+                assert(Pred->isLandingPad() &&
+                       "WinEHPrepare failed to split block");
+#endif
               ExceptBlocks.insert(BA->getBasicBlock());
             }
           }