Revert r258580 and r258581.

Those commits created an artificial edge from a cleanup to a synthesized
catchswitch in order to get the MSVC personality routine to execute
cleanups which don't cleanupret and are not wrapped by a catchswitch.

This worked well enough but is not a complete solution in situations
where there the cleanup infinite loops.

However, the real deal breaker behind this approach comes about from a
degenerate case where the cleanup is post-dominated by unreachable *and*
throws an exception.  This ends poorly because the catchswitch will
inadvertently catch the exception.

Because of this we should go back to our previous behavior of not
executing certain cleanups (identical behavior with the Itanium ABI
implementation in clang, GCC and ICC).

N.B. I think this could be salvaged by making the catchpad rethrow the
exception and properly transforming throwing calls in the cleanup into
invokes.

llvm-svn: 259338

1 files changed, 0 insertions, 113 deletions

diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index 12733acf3b8..281fe934292 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -81,7 +81,6 @@ private:
   void cloneCommonBlocks(Function &F);
   void removeImplausibleInstructions(Function &F);
   void cleanupPreparedFunclets(Function &F);
-  void fixupNoReturnCleanupPads(Function &F);
   void verifyPreparedFunclets(Function &F);
 
   // All fields are reset by runOnFunction.
@@ -657,7 +656,6 @@ void llvm::calculateClrEHStateNumbers(const Function *Fn,
 
 void WinEHPrepare::colorFunclets(Function &F) {
   BlockColors = colorEHFunclets(F);
-  FuncletBlocks.clear();
 
   // Invert the map from BB to colors to color to BBs.
   for (BasicBlock &BB : F) {
@@ -1003,115 +1001,6 @@ void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
   removeUnreachableBlocks(F);
 }
 
-// Cleanuppads which are postdominated by unreachable will not unwind to any
-// catchswitches, making them dead.  This is problematic if the original source
-// had a catch clause which could legitimately catch the exception, causing the
-// cleanup to run.
-//
-// This is only a problem for C++ where down-stream catches cause cleanups to
-// run.
-void WinEHPrepare::fixupNoReturnCleanupPads(Function &F) {
-  // We only need to do this for C++ personality routines,
-  // skip this work for all others.
-  if (Personality != EHPersonality::MSVC_CXX)
-    return;
-
-  // Do a quick sanity check on the color map before we throw it away so as to
-  // avoid hiding latent bugs.
-  DEBUG(verifyPreparedFunclets(F));
-  // Re-color the funclets because cleanupPreparedFunclets might have
-  // invalidated FuncletBlocks.
-  colorFunclets(F);
-
-  // We create a unique catchswitch for each parent it will be nested within.
-  SmallDenseMap<Value *, CatchSwitchInst *> NewCatchSwitches;
-  // Create a new catchswitch+catchpad where the catchpad is post-dominated by
-  // unreachable.
-  auto GetOrCreateCatchSwitch = [&](Value *ParentPad) {
-    auto &CatchSwitch = NewCatchSwitches[ParentPad];
-    if (CatchSwitch)
-      return CatchSwitch;
-
-    auto *ParentBB = isa<ConstantTokenNone>(ParentPad)
-                         ? &F.getEntryBlock()
-                         : cast<Instruction>(ParentPad)->getParent();
-
-    StringRef NameSuffix = ParentBB->getName();
-
-    BasicBlock *CatchSwitchBB = BasicBlock::Create(
-        F.getContext(), Twine("catchswitchbb.for.", NameSuffix));
-    CatchSwitchBB->insertInto(&F, ParentBB->getNextNode());
-    CatchSwitch = CatchSwitchInst::Create(ParentPad, /*UnwindDest=*/nullptr,
-                                          /*NumHandlers=*/1,
-                                          Twine("catchswitch.for.", NameSuffix),
-                                          CatchSwitchBB);
-
-    BasicBlock *CatchPadBB = BasicBlock::Create(
-        F.getContext(), Twine("catchpadbb.for.", NameSuffix));
-    CatchPadBB->insertInto(&F, CatchSwitchBB->getNextNode());
-    Value *CatchPadArgs[] = {
-        Constant::getNullValue(Type::getInt8PtrTy(F.getContext())),
-        ConstantInt::get(Type::getInt32Ty(F.getContext()), 64),
-        Constant::getNullValue(Type::getInt8PtrTy(F.getContext())),
-    };
-    CatchPadInst::Create(CatchSwitch, CatchPadArgs,
-                         Twine("catchpad.for.", NameSuffix), CatchPadBB);
-    new UnreachableInst(F.getContext(), CatchPadBB);
-
-    CatchSwitch->addHandler(CatchPadBB);
-
-    return CatchSwitch;
-  };
-
-  // Look for all basic blocks which are within cleanups which are postdominated
-  // by unreachable.
-  for (auto &Funclets : FuncletBlocks) {
-    BasicBlock *FuncletPadBB = Funclets.first;
-    auto *CleanupPad = dyn_cast<CleanupPadInst>(FuncletPadBB->getFirstNonPHI());
-    // Skip over any non-cleanup funclets.
-    if (!CleanupPad)
-      continue;
-    // Skip over any cleanups have unwind targets, they do not need this.
-    if (any_of(CleanupPad->users(),
-               [](const User *U) { return isa<CleanupReturnInst>(U); }))
-      continue;
-    // Walk the blocks within the cleanup which end in 'unreachable'.
-    // We will replace the unreachable instruction with a cleanupret;
-    // this cleanupret will unwind to a catchswitch with a lone catch-all
-    // catchpad.
-    std::vector<BasicBlock *> &BlocksInFunclet = Funclets.second;
-    for (BasicBlock *BB : BlocksInFunclet) {
-      auto *UI = dyn_cast<UnreachableInst>(BB->getTerminator());
-      if (!UI)
-        continue;
-      // Remove the unreachable instruction.
-      UI->eraseFromParent();
-
-      // Add our new cleanupret.
-      auto *ParentPad = CleanupPad->getParentPad();
-      CatchSwitchInst *CatchSwitch = GetOrCreateCatchSwitch(ParentPad);
-      CleanupReturnInst::Create(CleanupPad, CatchSwitch->getParent(), BB);
-    }
-  }
-
-  // Update BlockColors and FuncletBlocks to maintain WinEHPrepare's
-  // invariants.
-  for (auto CatchSwitchKV : NewCatchSwitches) {
-    CatchSwitchInst *CatchSwitch = CatchSwitchKV.second;
-    BasicBlock *CatchSwitchBB = CatchSwitch->getParent();
-
-    assert(CatchSwitch->getNumSuccessors() == 1);
-    BasicBlock *CatchPadBB = CatchSwitch->getSuccessor(0);
-    assert(isa<CatchPadInst>(CatchPadBB->getFirstNonPHI()));
-
-    BlockColors.insert({CatchSwitchBB, ColorVector(CatchSwitchBB)});
-    FuncletBlocks[CatchSwitchBB] = {CatchSwitchBB};
-
-    BlockColors.insert({CatchPadBB, ColorVector(CatchPadBB)});
-    FuncletBlocks[CatchPadBB] = {CatchPadBB};
-  }
-}
-
 void WinEHPrepare::verifyPreparedFunclets(Function &F) {
   for (BasicBlock &BB : F) {
     size_t NumColors = BlockColors[&BB].size();
@@ -1147,8 +1036,6 @@ bool WinEHPrepare::prepareExplicitEH(Function &F) {
     cleanupPreparedFunclets(F);
   }
 
-  fixupNoReturnCleanupPads(F);
-
   DEBUG(verifyPreparedFunclets(F));
   // Recolor the CFG to verify that all is well.
   DEBUG(colorFunclets(F));