[WebAssembly] Add functions for EHScopes

Summary:
There are functions using the term 'funclet' to refer to both
1. an EH scopes, the structure of BBs that starts with
catchpad/cleanuppad and ends with catchret/cleanupret, and
2. a small function that gets outlined in AsmPrinter, which is the
original meaning of 'funclet'.

So far the two have been the same thing; EH scopes are always outlined
in AsmPrinter as funclets at the end of the compilation pipeline. But
now wasm also uses scope-based EH but does not outline those, so we now
need to correctly distinguish those two use cases in functions.

This patch splits `MachineBasicBlock::isFuncletEntry` into
`isFuncletEntry` and `isEHScopeEntry`, and
`MachineFunction::hasFunclets` into `hasFunclets` and `hasEHScopes`, in
order to distinguish the two different use cases. And this also changes
some uses of the term 'funclet' to 'scope' in `getFuncletMembership` and
change the function name to `getEHScopeMembership` because this function
is not about outlined funclets but about EH scope memberships.

This change is in the same vein as D45559.

Reviewers: majnemer, dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D47005

llvm-svn: 333045

llvm/include/llvm/CodeGen/Analysis.h

@@ -124,7 +124,7 @@ bool returnTypeIsEligibleForTailCall(const Function *F, const Instruction *I,
                                      const TargetLoweringBase &TLI);
 
 DenseMap<const MachineBasicBlock *, int>
-getFuncletMembership(const MachineFunction &MF);
+getEHScopeMembership(const MachineFunction &MF);
 
 } // End llvm namespace
 

llvm/include/llvm/CodeGen/MachineBasicBlock.h

@@ -115,6 +115,11 @@ class MachineBasicBlock
   /// branch.
   bool AddressTaken = false;
 
+  /// Indicate that this basic block is the entry block of an EH scope, i.e.,
+  /// the block that used to have a catchpad or cleanuppad instruction in the
+  /// LLVM IR.
+  bool IsEHScopeEntry = false;
+
   /// Indicate that this basic block is the entry block of an EH funclet.
   bool IsEHFuncletEntry = false;
 
@@ -375,6 +380,14 @@ class MachineBasicBlock
 
   bool hasEHPadSuccessor() const;
 
+  /// Returns true if this is the entry block of an EH scope, i.e., the block
+  /// that used to have a catchpad or cleanuppad instruction in the LLVM IR.
+  bool isEHScopeEntry() const { return IsEHScopeEntry; }
+
+  /// Indicates if this is the entry block of an EH scope, i.e., the block that
+  /// that used to have a catchpad or cleanuppad instruction in the LLVM IR.
+  void setIsEHScopeEntry(bool V = true) { IsEHScopeEntry = V; }
+
   /// Returns true if this is the entry block of an EH funclet.
   bool isEHFuncletEntry() const { return IsEHFuncletEntry; }
 

llvm/include/llvm/CodeGen/MachineFunction.h

@@ -319,6 +319,7 @@ class MachineFunction {
 
   bool CallsEHReturn = false;
   bool CallsUnwindInit = false;
+  bool HasEHScopes = false;
   bool HasEHFunclets = false;
 
   /// List of C++ TypeInfo used.
@@ -760,6 +761,9 @@ class MachineFunction {
   bool callsUnwindInit() const { return CallsUnwindInit; }
   void setCallsUnwindInit(bool b) { CallsUnwindInit = b; }
 
+  bool hasEHScopes() const { return HasEHScopes; }
+  void setHasEHScopes(bool V) { HasEHScopes = V; }
+
   bool hasEHFunclets() const { return HasEHFunclets; }
   void setHasEHFunclets(bool V) { HasEHFunclets = V; }
 

llvm/lib/CodeGen/Analysis.cpp

@@ -629,26 +629,26 @@ bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
   return true;
 }
 
-static void collectFuncletMembers(
-    DenseMap<const MachineBasicBlock *, int> &FuncletMembership, int Funclet,
-    const MachineBasicBlock *MBB) {
+static void
+collectEHScopeMembers(DenseMap<const MachineBasicBlock *, int> &ScopeMembership,
+                      int Scope, const MachineBasicBlock *MBB) {
   SmallVector<const MachineBasicBlock *, 16> Worklist = {MBB};
   while (!Worklist.empty()) {
     const MachineBasicBlock *Visiting = Worklist.pop_back_val();
-    // Don't follow blocks which start new funclets.
+    // Don't follow blocks which start new scopes.
     if (Visiting->isEHPad() && Visiting != MBB)
       continue;
 
-    // Add this MBB to our funclet.
-    auto P = FuncletMembership.insert(std::make_pair(Visiting, Funclet));
+    // Add this MBB to our scope.
+    auto P = ScopeMembership.insert(std::make_pair(Visiting, Scope));
 
     // Don't revisit blocks.
     if (!P.second) {
-      assert(P.first->second == Funclet && "MBB is part of two funclets!");
+      assert(P.first->second == Scope && "MBB is part of two scopes!");
       continue;
     }
 
-    // Returns are boundaries where funclet transfer can occur, don't follow
+    // Returns are boundaries where scope transfer can occur, don't follow
     // successors.
     if (Visiting->isReturnBlock())
       continue;
@@ -659,25 +659,25 @@ static void collectFuncletMembers(
 }
 
 DenseMap<const MachineBasicBlock *, int>
-llvm::getFuncletMembership(const MachineFunction &MF) {
-  DenseMap<const MachineBasicBlock *, int> FuncletMembership;
+llvm::getEHScopeMembership(const MachineFunction &MF) {
+  DenseMap<const MachineBasicBlock *, int> ScopeMembership;
 
   // We don't have anything to do if there aren't any EH pads.
-  if (!MF.hasEHFunclets())
-    return FuncletMembership;
+  if (!MF.hasEHScopes())
+    return ScopeMembership;
 
   int EntryBBNumber = MF.front().getNumber();
   bool IsSEH = isAsynchronousEHPersonality(
       classifyEHPersonality(MF.getFunction().getPersonalityFn()));
 
   const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
-  SmallVector<const MachineBasicBlock *, 16> FuncletBlocks;
+  SmallVector<const MachineBasicBlock *, 16> ScopeBlocks;
   SmallVector<const MachineBasicBlock *, 16> UnreachableBlocks;
   SmallVector<const MachineBasicBlock *, 16> SEHCatchPads;
   SmallVector<std::pair<const MachineBasicBlock *, int>, 16> CatchRetSuccessors;
   for (const MachineBasicBlock &MBB : MF) {
-    if (MBB.isEHFuncletEntry()) {
-      FuncletBlocks.push_back(&MBB);
+    if (MBB.isEHScopeEntry()) {
+      ScopeBlocks.push_back(&MBB);
     } else if (IsSEH && MBB.isEHPad()) {
       SEHCatchPads.push_back(&MBB);
     } else if (MBB.pred_empty()) {
@@ -686,8 +686,8 @@ llvm::getFuncletMembership(const MachineFunction &MF) {
 
     MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator();
 
-    // CatchPads are not funclets for SEH so do not consider CatchRet to
-    // transfer control to another funclet.
+    // CatchPads are not scopes for SEH so do not consider CatchRet to
+    // transfer control to another scope.
     if (MBBI == MBB.end() || MBBI->getOpcode() != TII->getCatchReturnOpcode())
       continue;
 
@@ -700,24 +700,24 @@ llvm::getFuncletMembership(const MachineFunction &MF) {
   }
 
   // We don't have anything to do if there aren't any EH pads.
-  if (FuncletBlocks.empty())
-    return FuncletMembership;
+  if (ScopeBlocks.empty())
+    return ScopeMembership;
 
   // Identify all the basic blocks reachable from the function entry.
-  collectFuncletMembers(FuncletMembership, EntryBBNumber, &MF.front());
-  // All blocks not part of a funclet are in the parent function.
+  collectEHScopeMembers(ScopeMembership, EntryBBNumber, &MF.front());
+  // All blocks not part of a scope are in the parent function.
   for (const MachineBasicBlock *MBB : UnreachableBlocks)
-    collectFuncletMembers(FuncletMembership, EntryBBNumber, MBB);
-  // Next, identify all the blocks inside the funclets.
-  for (const MachineBasicBlock *MBB : FuncletBlocks)
-    collectFuncletMembers(FuncletMembership, MBB->getNumber(), MBB);
-  // SEH CatchPads aren't really funclets, handle them separately.
+    collectEHScopeMembers(ScopeMembership, EntryBBNumber, MBB);
+  // Next, identify all the blocks inside the scopes.
+  for (const MachineBasicBlock *MBB : ScopeBlocks)
+    collectEHScopeMembers(ScopeMembership, MBB->getNumber(), MBB);
+  // SEH CatchPads aren't really scopes, handle them separately.
   for (const MachineBasicBlock *MBB : SEHCatchPads)
-    collectFuncletMembers(FuncletMembership, EntryBBNumber, MBB);
+    collectEHScopeMembers(ScopeMembership, EntryBBNumber, MBB);
   // Finally, identify all the targets of a catchret.
   for (std::pair<const MachineBasicBlock *, int> CatchRetPair :
        CatchRetSuccessors)
-    collectFuncletMembers(FuncletMembership, CatchRetPair.second,
+    collectEHScopeMembers(ScopeMembership, CatchRetPair.second,
                           CatchRetPair.first);
-  return FuncletMembership;
+  return ScopeMembership;
 }

llvm/lib/CodeGen/BranchFolding.cpp

@@ -200,7 +200,7 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
   }
 
   // Recalculate funclet membership.
-  FuncletMembership = getFuncletMembership(MF);
+  FuncletMembership = getEHScopeMembership(MF);
 
   bool MadeChangeThisIteration = true;
   while (MadeChangeThisIteration) {
@@ -1293,7 +1293,7 @@ bool BranchFolder::OptimizeBranches(MachineFunction &MF) {
   // Make sure blocks are numbered in order
   MF.RenumberBlocks();
   // Renumbering blocks alters funclet membership, recalculate it.
-  FuncletMembership = getFuncletMembership(MF);
+  FuncletMembership = getEHScopeMembership(MF);
 
   for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
        I != E; ) {

llvm/lib/CodeGen/FuncletLayout.cpp

@@ -42,7 +42,7 @@ INITIALIZE_PASS(FuncletLayout, DEBUG_TYPE,
 
 bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
   DenseMap<const MachineBasicBlock *, int> FuncletMembership =
-      getFuncletMembership(F);
+      getEHScopeMembership(F);
   if (FuncletMembership.empty())
     return false;
 

llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

@@ -226,9 +226,10 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
       const Instruction *PadInst = BB.getFirstNonPHI();
       // If this is a non-landingpad EH pad, mark this function as using
       // funclets.
-      // FIXME: SEH catchpads do not create funclets, so we could avoid setting
-      // this in such cases in order to improve frame layout.
+      // FIXME: SEH catchpads do not create EH scope/funclets, so we could avoid
+      // setting this in such cases in order to improve frame layout.
       if (!isa<LandingPadInst>(PadInst)) {
+        MF->setHasEHScopes(true);
         MF->setHasEHFunclets(true);
         MF->getFrameInfo().setHasOpaqueSPAdjustment(true);
       }

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1379,7 +1379,10 @@ void SelectionDAGBuilder::visitCatchPad(const CatchPadInst &I) {
   auto Pers = classifyEHPersonality(FuncInfo.Fn->getPersonalityFn());
   bool IsMSVCCXX = Pers == EHPersonality::MSVC_CXX;
   bool IsCoreCLR = Pers == EHPersonality::CoreCLR;
+  bool IsSEH = isAsynchronousEHPersonality(Pers);
   MachineBasicBlock *CatchPadMBB = FuncInfo.MBB;
+  if (!IsSEH)
+    CatchPadMBB->setIsEHScopeEntry();
   // In MSVC C++ and CoreCLR, catchblocks are funclets and need prologues.
   if (IsMSVCCXX || IsCoreCLR)
     CatchPadMBB->setIsEHFuncletEntry();
@@ -1427,7 +1430,8 @@ void SelectionDAGBuilder::visitCatchRet(const CatchReturnInst &I) {
 
 void SelectionDAGBuilder::visitCleanupPad(const CleanupPadInst &CPI) {
   // Don't emit any special code for the cleanuppad instruction. It just marks
-  // the start of a funclet.
+  // the start of an EH scope/funclet.
+  FuncInfo.MBB->setIsEHScopeEntry();
   FuncInfo.MBB->setIsEHFuncletEntry();
   FuncInfo.MBB->setIsCleanupFuncletEntry();
 }
@@ -1449,6 +1453,7 @@ static void findUnwindDestinations(
     classifyEHPersonality(FuncInfo.Fn->getPersonalityFn());
   bool IsMSVCCXX = Personality == EHPersonality::MSVC_CXX;
   bool IsCoreCLR = Personality == EHPersonality::CoreCLR;
+  bool IsSEH = isAsynchronousEHPersonality(Personality);
 
   while (EHPadBB) {
     const Instruction *Pad = EHPadBB->getFirstNonPHI();
@@ -1461,6 +1466,7 @@ static void findUnwindDestinations(
       // Stop on cleanup pads. Cleanups are always funclet entries for all known
       // personalities.
       UnwindDests.emplace_back(FuncInfo.MBBMap[EHPadBB], Prob);
+      UnwindDests.back().first->setIsEHScopeEntry();
       UnwindDests.back().first->setIsEHFuncletEntry();
       break;
     } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Pad)) {
@@ -1470,6 +1476,8 @@ static void findUnwindDestinations(
         // For MSVC++ and the CLR, catchblocks are funclets and need prologues.
         if (IsMSVCCXX || IsCoreCLR)
           UnwindDests.back().first->setIsEHFuncletEntry();
+        if (!IsSEH)
+          UnwindDests.back().first->setIsEHScopeEntry();
       }
       NewEHPadBB = CatchSwitch->getUnwindDest();
     } else {