Cleanup unwind table emission code a bit.

This change removes the `tidyLandingPads` function, which previously
had a few responsibilities:

1. Dealing with the deletion of an invoke, after MachineFunction lowering.
2. Dealing with the deletion of a landing pad BB, after MachineFunction lowering.
3. Cleaning up the type-id list generated by `MachineFunction::addLandingPad`.

Case 3 has been fixed in the generator, and the others are now handled
during table emission.

This change also removes `MachineFunction`'s `addCatchTypeInfo`,
`addFilterTypeInfo`, and `addCleanup` helper fns, as they had a single
caller, and being outlined didn't make it simpler.

Finally, as calling `tidyLandingPads` was effectively the only thing
`DwarfCFIExceptionBase` did, that class has been eliminated.

Author: jyknight

llvm/include/llvm/CodeGen/MachineFunction.h

@@ -1105,10 +1105,6 @@ class LLVM_EXTERNAL_VISIBILITY MachineFunction {
   /// Find or create an LandingPadInfo for the specified MachineBasicBlock.
   LandingPadInfo &getOrCreateLandingPadInfo(MachineBasicBlock *LandingPad);
 
-  /// Remap landing pad labels and remove any deleted landing pads.
-  void tidyLandingPads(DenseMap<MCSymbol *, uintptr_t> *LPMap = nullptr,
-                       bool TidyIfNoBeginLabels = true);
-
   /// Return a reference to the landing pad info for the current function.
   const std::vector<LandingPadInfo> &getLandingPads() const {
     return LandingPads;
@@ -1124,22 +1120,11 @@ class LLVM_EXTERNAL_VISIBILITY MachineFunction {
   /// entry.
   MCSymbol *addLandingPad(MachineBasicBlock *LandingPad);
 
-  /// Provide the catch typeinfo for a landing pad.
-  void addCatchTypeInfo(MachineBasicBlock *LandingPad,
-                        ArrayRef<const GlobalValue *> TyInfo);
-
-  /// Provide the filter typeinfo for a landing pad.
-  void addFilterTypeInfo(MachineBasicBlock *LandingPad,
-                         ArrayRef<const GlobalValue *> TyInfo);
-
-  /// Add a cleanup action for a landing pad.
-  void addCleanup(MachineBasicBlock *LandingPad);
-
   /// Return the type id for the specified typeinfo.  This is function wide.
   unsigned getTypeIDFor(const GlobalValue *TI);
 
   /// Return the id of the filter encoded by TyIds.  This is function wide.
-  int getFilterIDFor(std::vector<unsigned> &TyIds);
+  int getFilterIDFor(ArrayRef<unsigned> TyIds);
 
   /// Map the landing pad's EH symbol to the call site indexes.
   void setCallSiteLandingPad(MCSymbol *Sym, ArrayRef<unsigned> Sites);

llvm/lib/CodeGen/AsmPrinter/AIXException.cpp

@@ -21,16 +21,7 @@
 
 namespace llvm {
 
-AIXException::AIXException(AsmPrinter *A) : DwarfCFIExceptionBase(A) {}
-
-// This overrides 'DwarfCFIExceptionBase::markFunctionEnd', to avoid the call to
-// tidyLandingPads. This is necessary, because the
-// 'PPCAIXAsmPrinter::emitFunctionBodyEnd' function already checked whether we
-// need ehinfo, and emitted a traceback table with the bits set to indicate that
-// we will be emitting it, if so. Thus, if we remove it now -- so late in the
-// process -- we'll end up having emitted a reference to __ehinfo.N symbol, but
-// not emitting a definition for said symbol.
-void AIXException::markFunctionEnd() {}
+AIXException::AIXException(AsmPrinter *A) : EHStreamer(A) {}
 
 void AIXException::emitExceptionInfoTable(const MCSymbol *LSDA,
                                           const MCSymbol *PerSym) {

llvm/lib/CodeGen/AsmPrinter/ARMException.cpp

@@ -19,7 +19,7 @@
 #include "llvm/MC/MCStreamer.h"
 using namespace llvm;
 
-ARMException::ARMException(AsmPrinter *A) : DwarfCFIExceptionBase(A) {}
+ARMException::ARMException(AsmPrinter *A) : EHStreamer(A) {}
 
 ARMException::~ARMException() = default;
 
@@ -51,7 +51,6 @@ void ARMException::beginFunction(const MachineFunction *MF) {
 void ARMException::markFunctionEnd() {
   if (shouldEmitCFI)
     Asm->OutStreamer->emitCFIEndProc();
-  DwarfCFIExceptionBase::markFunctionEnd();
 }
 
 /// endFunction - Gather and emit post-function exception information.

llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

@@ -23,18 +23,7 @@
 #include "llvm/Target/TargetOptions.h"
 using namespace llvm;
 
-DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A) : EHStreamer(A) {}
-
-void DwarfCFIExceptionBase::markFunctionEnd() {
-  // Map all labels and get rid of any dead landing pads.
-  if (!Asm->MF->getLandingPads().empty()) {
-    MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF);
-    NonConstMF->tidyLandingPads();
-  }
-}
-
-DwarfCFIException::DwarfCFIException(AsmPrinter *A)
-    : DwarfCFIExceptionBase(A) {}
+DwarfCFIException::DwarfCFIException(AsmPrinter *A) : EHStreamer(A) {}
 
 DwarfCFIException::~DwarfCFIException() = default;
 

llvm/lib/CodeGen/AsmPrinter/DwarfException.h

@@ -21,19 +21,7 @@ namespace llvm {
 class MachineFunction;
 class ARMTargetStreamer;
 
-class LLVM_LIBRARY_VISIBILITY DwarfCFIExceptionBase : public EHStreamer {
-protected:
-  DwarfCFIExceptionBase(AsmPrinter *A);
-
-  /// Per-function flag to indicate if frame CFI info should be emitted.
-  bool shouldEmitCFI = false;
-  /// Per-module flag to indicate if .cfi_section has beeen emitted.
-  bool hasEmittedCFISections = false;
-
-  void markFunctionEnd() override;
-};
-
-class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public DwarfCFIExceptionBase {
+class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public EHStreamer {
   /// Per-function flag to indicate if .cfi_personality should be emitted.
   bool shouldEmitPersonality = false;
 
@@ -43,6 +31,12 @@ class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public DwarfCFIExceptionBase {
   /// Per-function flag to indicate if .cfi_lsda should be emitted.
   bool shouldEmitLSDA = false;
 
+  /// Per-function flag to indicate if frame CFI info should be emitted.
+  bool shouldEmitCFI = false;
+
+  /// Per-module flag to indicate if .cfi_section has beeen emitted.
+  bool hasEmittedCFISections = false;
+
 public:
   //===--------------------------------------------------------------------===//
   // Main entry points.
@@ -64,7 +58,13 @@ class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public DwarfCFIExceptionBase {
   void endBasicBlockSection(const MachineBasicBlock &MBB) override;
 };
 
-class LLVM_LIBRARY_VISIBILITY ARMException : public DwarfCFIExceptionBase {
+class LLVM_LIBRARY_VISIBILITY ARMException : public EHStreamer {
+  /// Per-function flag to indicate if frame CFI info should be emitted.
+  bool shouldEmitCFI = false;
+
+  /// Per-module flag to indicate if .cfi_section has beeen emitted.
+  bool hasEmittedCFISections = false;
+
   void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) override;
   ARMTargetStreamer &getTargetStreamer();
 
@@ -88,16 +88,14 @@ class LLVM_LIBRARY_VISIBILITY ARMException : public DwarfCFIExceptionBase {
   void markFunctionEnd() override;
 };
 
-class LLVM_LIBRARY_VISIBILITY AIXException : public DwarfCFIExceptionBase {
+class LLVM_LIBRARY_VISIBILITY AIXException : public EHStreamer {
   /// This is AIX's compat unwind section, which unwinder would use
   /// to find the location of LSDA area and personality rountine.
   void emitExceptionInfoTable(const MCSymbol *LSDA, const MCSymbol *PerSym);
 
 public:
   AIXException(AsmPrinter *A);
 
-  void markFunctionEnd() override;
-
   void endModule() override {}
   void beginFunction(const MachineFunction *MF) override {}
   void endFunction(const MachineFunction *MF) override;

llvm/lib/CodeGen/AsmPrinter/EHStreamer.cpp

@@ -195,6 +195,12 @@ void EHStreamer::computePadMap(
     const LandingPadInfo *LandingPad = LandingPads[i];
     for (unsigned j = 0, E = LandingPad->BeginLabels.size(); j != E; ++j) {
       MCSymbol *BeginLabel = LandingPad->BeginLabels[j];
+      MCSymbol *EndLabel = LandingPad->BeginLabels[j];
+      // If we have deleted the code for a given invoke after registering it in
+      // the LandingPad label list, the associated symbols will not have been
+      // emitted. In that case, ignore this callsite entry.
+      if (!BeginLabel->isDefined() || !EndLabel->isDefined())
+        continue;
       assert(!PadMap.count(BeginLabel) && "Duplicate landing pad labels!");
       PadRange P = { i, j };
       PadMap[BeginLabel] = P;
@@ -383,8 +389,14 @@ MCSymbol *EHStreamer::emitExceptionTable() {
   SmallVector<const LandingPadInfo *, 64> LandingPads;
   LandingPads.reserve(PadInfos.size());
 
-  for (const LandingPadInfo &LPI : PadInfos)
+  for (const LandingPadInfo &LPI : PadInfos) {
+    // If a landing-pad has an associated label, but the label wasn't ever
+    // emitted, then skip it.  (This can occur if the landingpad's MBB was
+    // deleted).
+    if (LPI.LandingPadLabel && !LPI.LandingPadLabel->isDefined())
+      continue;
     LandingPads.push_back(&LPI);
+  }
 
   // Order landing pads lexicographically by type id.
   llvm::sort(LandingPads, [](const LandingPadInfo *L, const LandingPadInfo *R) {

llvm/lib/CodeGen/AsmPrinter/WasmException.cpp

@@ -42,16 +42,6 @@ void WasmException::endModule() {
   }
 }
 
-void WasmException::markFunctionEnd() {
-  // Get rid of any dead landing pads.
-  if (!Asm->MF->getLandingPads().empty()) {
-    auto *NonConstMF = const_cast<MachineFunction *>(Asm->MF);
-    // Wasm does not set BeginLabel and EndLabel information for landing pads,
-    // so we should set the second argument false.
-    NonConstMF->tidyLandingPads(nullptr, /* TidyIfNoBeginLabels */ false);
-  }
-}
-
 void WasmException::endFunction(const MachineFunction *MF) {
   bool ShouldEmitExceptionTable = false;
   for (const LandingPadInfo &Info : MF->getLandingPads()) {

llvm/lib/CodeGen/AsmPrinter/WasmException.h

@@ -28,7 +28,6 @@ class LLVM_LIBRARY_VISIBILITY WasmException : public EHStreamer {
 
   void endModule() override;
   void beginFunction(const MachineFunction *MF) override {}
-  void markFunctionEnd() override;
   void endFunction(const MachineFunction *MF) override;
 
 protected:

llvm/lib/CodeGen/AsmPrinter/WinException.cpp

@@ -130,14 +130,6 @@ void WinException::endFunction(const MachineFunction *MF) {
   if (F.hasPersonalityFn())
     Per = classifyEHPersonality(F.getPersonalityFn()->stripPointerCasts());
 
-  // Get rid of any dead landing pads if we're not using funclets. In funclet
-  // schemes, the landing pad is not actually reachable. It only exists so
-  // that we can emit the right table data.
-  if (!isFuncletEHPersonality(Per)) {
-    MachineFunction *NonConstMF = const_cast<MachineFunction*>(MF);
-    NonConstMF->tidyLandingPads();
-  }
-
   endFuncletImpl();
 
   // endFunclet will emit the necessary .xdata tables for table-based SEH.

llvm/lib/CodeGen/MachineFunction.cpp

@@ -763,32 +763,36 @@ MCSymbol *MachineFunction::addLandingPad(MachineBasicBlock *LandingPad) {
             dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts()))
       getMMI().addPersonality(PF);
 
-    if (LPI->isCleanup())
-      addCleanup(LandingPad);
+    // If there's no typeid list specified, then "cleanup" is implicit.
+    // Otherwise, id 0 is reserved for the cleanup action.
+    if (LPI->isCleanup() && LPI->getNumClauses() != 0)
+      LP.TypeIds.push_back(0);
 
     // FIXME: New EH - Add the clauses in reverse order. This isn't 100%
     //        correct, but we need to do it this way because of how the DWARF EH
     //        emitter processes the clauses.
     for (unsigned I = LPI->getNumClauses(); I != 0; --I) {
       Value *Val = LPI->getClause(I - 1);
       if (LPI->isCatch(I - 1)) {
-        addCatchTypeInfo(LandingPad,
-                         dyn_cast<GlobalValue>(Val->stripPointerCasts()));
+        LP.TypeIds.push_back(
+            getTypeIDFor(dyn_cast<GlobalValue>(Val->stripPointerCasts())));
       } else {
         // Add filters in a list.
         auto *CVal = cast<Constant>(Val);
-        SmallVector<const GlobalValue *, 4> FilterList;
+        SmallVector<unsigned, 4> FilterList;
         for (const Use &U : CVal->operands())
-          FilterList.push_back(cast<GlobalValue>(U->stripPointerCasts()));
+          FilterList.push_back(
+              getTypeIDFor(cast<GlobalValue>(U->stripPointerCasts())));
 
-        addFilterTypeInfo(LandingPad, FilterList);
+        LP.TypeIds.push_back(getFilterIDFor(FilterList));
       }
     }
 
   } else if (const auto *CPI = dyn_cast<CatchPadInst>(FirstI)) {
     for (unsigned I = CPI->arg_size(); I != 0; --I) {
-      Value *TypeInfo = CPI->getArgOperand(I - 1)->stripPointerCasts();
-      addCatchTypeInfo(LandingPad, dyn_cast<GlobalValue>(TypeInfo));
+      auto *TypeInfo =
+          dyn_cast<GlobalValue>(CPI->getArgOperand(I - 1)->stripPointerCasts());
+      LP.TypeIds.push_back(getTypeIDFor(TypeInfo));
     }
 
   } else {
@@ -798,73 +802,6 @@ MCSymbol *MachineFunction::addLandingPad(MachineBasicBlock *LandingPad) {
   return LandingPadLabel;
 }
 
-void MachineFunction::addCatchTypeInfo(MachineBasicBlock *LandingPad,
-                                       ArrayRef<const GlobalValue *> TyInfo) {
-  LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
-  for (const GlobalValue *GV : llvm::reverse(TyInfo))
-    LP.TypeIds.push_back(getTypeIDFor(GV));
-}
-
-void MachineFunction::addFilterTypeInfo(MachineBasicBlock *LandingPad,
-                                        ArrayRef<const GlobalValue *> TyInfo) {
-  LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
-  std::vector<unsigned> IdsInFilter(TyInfo.size());
-  for (unsigned I = 0, E = TyInfo.size(); I != E; ++I)
-    IdsInFilter[I] = getTypeIDFor(TyInfo[I]);
-  LP.TypeIds.push_back(getFilterIDFor(IdsInFilter));
-}
-
-void MachineFunction::tidyLandingPads(DenseMap<MCSymbol *, uintptr_t> *LPMap,
-                                      bool TidyIfNoBeginLabels) {
-  for (unsigned i = 0; i != LandingPads.size(); ) {
-    LandingPadInfo &LandingPad = LandingPads[i];
-    if (LandingPad.LandingPadLabel &&
-        !LandingPad.LandingPadLabel->isDefined() &&
-        (!LPMap || (*LPMap)[LandingPad.LandingPadLabel] == 0))
-      LandingPad.LandingPadLabel = nullptr;
-
-    // Special case: we *should* emit LPs with null LP MBB. This indicates
-    // "nounwind" case.
-    if (!LandingPad.LandingPadLabel && LandingPad.LandingPadBlock) {
-      LandingPads.erase(LandingPads.begin() + i);
-      continue;
-    }
-
-    if (TidyIfNoBeginLabels) {
-      for (unsigned j = 0, e = LandingPads[i].BeginLabels.size(); j != e; ++j) {
-        MCSymbol *BeginLabel = LandingPad.BeginLabels[j];
-        MCSymbol *EndLabel = LandingPad.EndLabels[j];
-        if ((BeginLabel->isDefined() || (LPMap && (*LPMap)[BeginLabel] != 0)) &&
-            (EndLabel->isDefined() || (LPMap && (*LPMap)[EndLabel] != 0)))
-          continue;
-
-        LandingPad.BeginLabels.erase(LandingPad.BeginLabels.begin() + j);
-        LandingPad.EndLabels.erase(LandingPad.EndLabels.begin() + j);
-        --j;
-        --e;
-      }
-
-      // Remove landing pads with no try-ranges.
-      if (LandingPads[i].BeginLabels.empty()) {
-        LandingPads.erase(LandingPads.begin() + i);
-        continue;
-      }
-    }
-
-    // If there is no landing pad, ensure that the list of typeids is empty.
-    // If the only typeid is a cleanup, this is the same as having no typeids.
-    if (!LandingPad.LandingPadBlock ||
-        (LandingPad.TypeIds.size() == 1 && !LandingPad.TypeIds[0]))
-      LandingPad.TypeIds.clear();
-    ++i;
-  }
-}
-
-void MachineFunction::addCleanup(MachineBasicBlock *LandingPad) {
-  LandingPadInfo &LP = getOrCreateLandingPadInfo(LandingPad);
-  LP.TypeIds.push_back(0);
-}
-
 void MachineFunction::setCallSiteLandingPad(MCSymbol *Sym,
                                             ArrayRef<unsigned> Sites) {
   LPadToCallSiteMap[Sym].append(Sites.begin(), Sites.end());
@@ -878,7 +815,7 @@ unsigned MachineFunction::getTypeIDFor(const GlobalValue *TI) {
   return TypeInfos.size();
 }
 
-int MachineFunction::getFilterIDFor(std::vector<unsigned> &TyIds) {
+int MachineFunction::getFilterIDFor(ArrayRef<unsigned> TyIds) {
   // If the new filter coincides with the tail of an existing filter, then
   // re-use the existing filter.  Folding filters more than this requires
   // re-ordering filters and/or their elements - probably not worth it.