[WinEH] Avoid creating MBBs for LLVM BBs that cannot contain code

Typically these are catchpads, which hold data used to decide whether to
catch the exception or continue unwinding. We also shouldn't create MBBs
for catchendpads, cleanupendpads, or terminatepads, since no real code
can live in them.

This fixes a problem where MI passes (like the register allocator) would
try to put code into catchpad blocks, which are not executed by the
runtime. In the new world, blocks ending in invokes now have many
possible successors.

llvm-svn: 247102

1 files changed, 18 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 3a51676bc9a..7bbb194ac19 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -212,6 +212,22 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   // also creates the initial PHI MachineInstrs, though none of the input
   // operands are populated.
   for (BB = Fn->begin(); BB != EB; ++BB) {
+    // Don't create MachineBasicBlocks for imaginary EH pad blocks. These blocks
+    // are really data, and no instructions can live here.
+    if (BB->isEHPad()) {
+      const Instruction *I = BB->getFirstNonPHI();
+      if (!isa<LandingPadInst>(I))
+        MMI.setHasEHFunclets(true);
+      if (isa<CatchPadInst>(I) || isa<CatchEndPadInst>(I) ||
+          isa<CleanupEndPadInst>(I)) {
+        assert(&*BB->begin() == I &&
+               "WinEHPrepare failed to remove PHIs from imaginary BBs");
+        continue;
+      } else if (!isa<LandingPadInst>(I)) {
+        llvm_unreachable("unhandled EH pad in MBB graph");
+      }
+    }
+
     MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
     MBBMap[BB] = MBB;
     MF->push_back(MBB);
@@ -252,9 +268,9 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
   // Mark landing pad blocks.
   SmallVector<const LandingPadInst *, 4> LPads;
   for (BB = Fn->begin(); BB != EB; ++BB) {
-    if (BB->isEHPad())
-      MBBMap[BB]->setIsEHPad();
     const Instruction *FNP = BB->getFirstNonPHI();
+    if (BB->isEHPad() && !isa<CatchPadInst>(FNP) && !isa<CatchEndPadInst>(FNP))
+      MBBMap[BB]->setIsEHPad();
     if (const auto *LPI = dyn_cast<LandingPadInst>(FNP))
       LPads.push_back(LPI);
   }