[c++20] Fix some ambiguities in our mangling of lambdas with explicit

template parameters.

This finishes the implementation of the proposal described in
https://github.com/itanium-cxx-abi/cxx-abi/issues/31. (We already
implemented the <lambda-sig> extensions, but didn't take them into
account when computing mangling numbers, and didn't deal properly with
expanded parameter packs, and didn't disambiguate between different
levels of template parameters in manglings.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@371004 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Mangle.h

@@ -170,6 +170,8 @@ public:
   virtual void mangleCXXDtorComdat(const CXXDestructorDecl *D,
                                    raw_ostream &) = 0;
 
+  virtual void mangleLambdaSig(const CXXRecordDecl *Lambda, raw_ostream &) = 0;
+
   static bool classof(const MangleContext *C) {
     return C->getKind() == MK_Itanium;
   }

lib/AST/DeclBase.cpp

@@ -12,6 +12,7 @@
 
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTLambda.h"
 #include "clang/AST/ASTMutationListener.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/AttrIterator.h"
@@ -1043,6 +1044,12 @@ DeclContext *DeclContext::getLookupParent() {
         getLexicalParent()->getRedeclContext()->isRecord())
       return getLexicalParent();
 
+  // A lookup within the call operator of a lambda never looks in the lambda
+  // class; instead, skip to the context in which that closure type is
+  // declared.
+  if (isLambdaCallOperator(this))
+    return getParent()->getParent();
+
   return getParent();
 }
 

lib/AST/ItaniumCXXABI.cpp

@@ -19,10 +19,12 @@
 #include "CXXABI.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclCXX.h"
+#include "clang/AST/Mangle.h"
 #include "clang/AST/MangleNumberingContext.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/Type.h"
 #include "clang/Basic/TargetInfo.h"
+#include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/iterator.h"
 
 using namespace clang;
@@ -73,10 +75,33 @@ struct DecompositionDeclName {
 }
 
 namespace llvm {
+template<typename T> bool isDenseMapKeyEmpty(T V) {
+  return llvm::DenseMapInfo<T>::isEqual(
+      V, llvm::DenseMapInfo<T>::getEmptyKey());
+}
+template<typename T> bool isDenseMapKeyTombstone(T V) {
+  return llvm::DenseMapInfo<T>::isEqual(
+      V, llvm::DenseMapInfo<T>::getTombstoneKey());
+}
+
+template<typename T>
+Optional<bool> areDenseMapKeysEqualSpecialValues(T LHS, T RHS) {
+  bool LHSEmpty = isDenseMapKeyEmpty(LHS);
+  bool RHSEmpty = isDenseMapKeyEmpty(RHS);
+  if (LHSEmpty || RHSEmpty)
+    return LHSEmpty && RHSEmpty;
+
+  bool LHSTombstone = isDenseMapKeyTombstone(LHS);
+  bool RHSTombstone = isDenseMapKeyTombstone(RHS);
+  if (LHSTombstone || RHSTombstone)
+    return LHSTombstone && RHSTombstone;
+
+  return None;
+}
+
 template<>
 struct DenseMapInfo<DecompositionDeclName> {
   using ArrayInfo = llvm::DenseMapInfo<ArrayRef<const BindingDecl*>>;
-  using IdentInfo = llvm::DenseMapInfo<const IdentifierInfo*>;
   static DecompositionDeclName getEmptyKey() {
     return {ArrayInfo::getEmptyKey()};
   }
@@ -88,10 +113,10 @@ struct DenseMapInfo<DecompositionDeclName> {
     return llvm::hash_combine_range(Key.begin(), Key.end());
   }
   static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS) {
-    if (ArrayInfo::isEqual(LHS.Bindings, ArrayInfo::getEmptyKey()))
-      return ArrayInfo::isEqual(RHS.Bindings, ArrayInfo::getEmptyKey());
-    if (ArrayInfo::isEqual(LHS.Bindings, ArrayInfo::getTombstoneKey()))
-      return ArrayInfo::isEqual(RHS.Bindings, ArrayInfo::getTombstoneKey());
+    if (Optional<bool> Result = areDenseMapKeysEqualSpecialValues(
+            LHS.Bindings, RHS.Bindings))
+      return *Result;
+
     return LHS.Bindings.size() == RHS.Bindings.size() &&
            std::equal(LHS.begin(), LHS.end(), RHS.begin());
   }
@@ -103,29 +128,32 @@ namespace {
 /// Keeps track of the mangled names of lambda expressions and block
 /// literals within a particular context.
 class ItaniumNumberingContext : public MangleNumberingContext {
-  llvm::DenseMap<const Type *, unsigned> ManglingNumbers;
+  ItaniumMangleContext *Mangler;
+  llvm::StringMap<unsigned> LambdaManglingNumbers;
+  unsigned BlockManglingNumber = 0;
   llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;
   llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;
   llvm::DenseMap<DecompositionDeclName, unsigned>
       DecompsitionDeclManglingNumbers;
 
 public:
+  ItaniumNumberingContext(ItaniumMangleContext *Mangler) : Mangler(Mangler) {}
+
   unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
-    const FunctionProtoType *Proto =
-        CallOperator->getType()->getAs<FunctionProtoType>();
-    ASTContext &Context = CallOperator->getASTContext();
+    const CXXRecordDecl *Lambda = CallOperator->getParent();
+    assert(Lambda->isLambda());
+
+    // Computation of the <lambda-sig> is non-trivial and subtle. Rather than
+    // duplicating it here, just mangle the <lambda-sig> directly.
+    llvm::SmallString<128> LambdaSig;
+    llvm::raw_svector_ostream Out(LambdaSig);
+    Mangler->mangleLambdaSig(Lambda, Out);
 
-    FunctionProtoType::ExtProtoInfo EPI;
-    EPI.Variadic = Proto->isVariadic();
-    QualType Key =
-        Context.getFunctionType(Context.VoidTy, Proto->getParamTypes(), EPI);
-    Key = Context.getCanonicalType(Key);
-    return ++ManglingNumbers[Key->castAs<FunctionProtoType>()];
+    return ++LambdaManglingNumbers[LambdaSig];
   }
 
   unsigned getManglingNumber(const BlockDecl *BD) override {
-    const Type *Ty = nullptr;
-    return ++ManglingNumbers[Ty];
+    return ++BlockManglingNumber;
   }
 
   unsigned getStaticLocalNumber(const VarDecl *VD) override {
@@ -154,10 +182,13 @@ public:
 };
 
 class ItaniumCXXABI : public CXXABI {
+private:
+  std::unique_ptr<MangleContext> Mangler;
 protected:
   ASTContext &Context;
 public:
-  ItaniumCXXABI(ASTContext &Ctx) : Context(Ctx) { }
+  ItaniumCXXABI(ASTContext &Ctx)
+      : Mangler(Ctx.createMangleContext()), Context(Ctx) {}
 
   MemberPointerInfo
   getMemberPointerInfo(const MemberPointerType *MPT) const override {
@@ -218,7 +249,8 @@ public:
 
   std::unique_ptr<MangleNumberingContext>
   createMangleNumberingContext() const override {
-    return std::make_unique<ItaniumNumberingContext>();
+    return std::make_unique<ItaniumNumberingContext>(
+        cast<ItaniumMangleContext>(Mangler.get()));
   }
 };
 }

lib/AST/ItaniumMangle.cpp

@@ -170,6 +170,8 @@ public:
 
   void mangleStringLiteral(const StringLiteral *, raw_ostream &) override;
 
+  void mangleLambdaSig(const CXXRecordDecl *Lambda, raw_ostream &) override;
+
   bool getNextDiscriminator(const NamedDecl *ND, unsigned &disc) {
     // Lambda closure types are already numbered.
     if (isLambda(ND))
@@ -424,6 +426,7 @@ public:
   void mangleName(const NamedDecl *ND);
   void mangleType(QualType T);
   void mangleNameOrStandardSubstitution(const NamedDecl *ND);
+  void mangleLambdaSig(const CXXRecordDecl *Lambda);
 
 private:
 
@@ -550,7 +553,7 @@ private:
   void mangleTemplateArgs(const TemplateArgumentList &AL);
   void mangleTemplateArg(TemplateArgument A);
 
-  void mangleTemplateParameter(unsigned Index);
+  void mangleTemplateParameter(unsigned Depth, unsigned Index);
 
   void mangleFunctionParam(const ParmVarDecl *parm);
 
@@ -965,7 +968,7 @@ void CXXNameMangler::mangleUnscopedTemplateName(
   if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
     assert(!AdditionalAbiTags &&
            "template template param cannot have abi tags");
-    mangleTemplateParameter(TTP->getIndex());
+    mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
   } else if (isa<BuiltinTemplateDecl>(ND)) {
     mangleUnscopedName(ND, AdditionalAbiTags);
   } else {
@@ -1686,16 +1689,42 @@ void CXXNameMangler::mangleUnqualifiedBlock(const BlockDecl *Block) {
 //   ::= Tn <type>                       # template non-type parameter
 //   ::= Tt <template-param-decl>* E     # template template parameter
 void CXXNameMangler::mangleTemplateParamDecl(const NamedDecl *Decl) {
-  if (isa<TemplateTypeParmDecl>(Decl)) {
+  if (auto *Ty = dyn_cast<TemplateTypeParmDecl>(Decl)) {
+    if (Ty->isParameterPack())
+      Out << "Tp";
     Out << "Ty";
   } else if (auto *Tn = dyn_cast<NonTypeTemplateParmDecl>(Decl)) {
-    Out << "Tn";
-    mangleType(Tn->getType());
+    if (Tn->isExpandedParameterPack()) {
+      for (unsigned I = 0, N = Tn->getNumExpansionTypes(); I != N; ++I) {
+        Out << "Tn";
+        mangleType(Tn->getExpansionType(I));
+      }
+    } else {
+      QualType T = Tn->getType();
+      if (Tn->isParameterPack()) {
+        Out << "Tp";
+        T = T->castAs<PackExpansionType>()->getPattern();
+      }
+      Out << "Tn";
+      mangleType(T);
+    }
   } else if (auto *Tt = dyn_cast<TemplateTemplateParmDecl>(Decl)) {
-    Out << "Tt";
-    for (auto *Param : *Tt->getTemplateParameters())
-      mangleTemplateParamDecl(Param);
-    Out << "E";
+    if (Tt->isExpandedParameterPack()) {
+      for (unsigned I = 0, N = Tt->getNumExpansionTemplateParameters(); I != N;
+           ++I) {
+        Out << "Tt";
+        for (auto *Param : *Tt->getExpansionTemplateParameters(I))
+          mangleTemplateParamDecl(Param);
+        Out << "E";
+      }
+    } else {
+      if (Tt->isParameterPack())
+        Out << "Tp";
+      Out << "Tt";
+      for (auto *Param : *Tt->getTemplateParameters())
+        mangleTemplateParamDecl(Param);
+      Out << "E";
+    }
   }
 }
 
@@ -1726,12 +1755,7 @@ void CXXNameMangler::mangleLambda(const CXXRecordDecl *Lambda) {
   }
 
   Out << "Ul";
-  for (auto *D : Lambda->getLambdaExplicitTemplateParameters())
-    mangleTemplateParamDecl(D);
-  const FunctionProtoType *Proto = Lambda->getLambdaTypeInfo()->getType()->
-                                   getAs<FunctionProtoType>();
-  mangleBareFunctionType(Proto, /*MangleReturnType=*/false,
-                         Lambda->getLambdaStaticInvoker());
+  mangleLambdaSig(Lambda);
   Out << "E";
 
   // The number is omitted for the first closure type with a given
@@ -1746,6 +1770,15 @@ void CXXNameMangler::mangleLambda(const CXXRecordDecl *Lambda) {
   Out << '_';
 }
 
+void CXXNameMangler::mangleLambdaSig(const CXXRecordDecl *Lambda) {
+  for (auto *D : Lambda->getLambdaExplicitTemplateParameters())
+    mangleTemplateParamDecl(D);
+  const FunctionProtoType *Proto = Lambda->getLambdaTypeInfo()->getType()->
+                                   getAs<FunctionProtoType>();
+  mangleBareFunctionType(Proto, /*MangleReturnType=*/false,
+                         Lambda->getLambdaStaticInvoker());
+}
+
 void CXXNameMangler::manglePrefix(NestedNameSpecifier *qualifier) {
   switch (qualifier->getKind()) {
   case NestedNameSpecifier::Global:
@@ -1852,7 +1885,7 @@ void CXXNameMangler::mangleTemplatePrefix(const TemplateDecl *ND,
 
   // <template-template-param> ::= <template-param>
   if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
-    mangleTemplateParameter(TTP->getIndex());
+    mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
   } else {
     manglePrefix(getEffectiveDeclContext(ND), NoFunction);
     if (isa<BuiltinTemplateDecl>(ND))
@@ -1885,8 +1918,8 @@ void CXXNameMangler::mangleType(TemplateName TN) {
     goto HaveDecl;
 
   HaveDecl:
-    if (isa<TemplateTemplateParmDecl>(TD))
-      mangleTemplateParameter(cast<TemplateTemplateParmDecl>(TD)->getIndex());
+    if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TD))
+      mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
     else
       mangleName(TD);
     break;
@@ -2964,7 +2997,7 @@ void CXXNameMangler::mangleType(const MemberPointerType *T) {
 
 // <type>           ::= <template-param>
 void CXXNameMangler::mangleType(const TemplateTypeParmType *T) {
-  mangleTemplateParameter(T->getIndex());
+  mangleTemplateParameter(T->getDepth(), T->getIndex());
 }
 
 // <type>           ::= <template-param>
@@ -3535,7 +3568,7 @@ void CXXNameMangler::mangleDeclRefExpr(const NamedDecl *D) {
 
   case Decl::NonTypeTemplateParm:
     const NonTypeTemplateParmDecl *PD = cast<NonTypeTemplateParmDecl>(D);
-    mangleTemplateParameter(PD->getIndex());
+    mangleTemplateParameter(PD->getDepth(), PD->getIndex());
     break;
   }
 }
@@ -4264,13 +4297,13 @@ recurse:
     Out << "sZ";
     const NamedDecl *Pack = SPE->getPack();
     if (const TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(Pack))
-      mangleTemplateParameter(TTP->getIndex());
+      mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
     else if (const NonTypeTemplateParmDecl *NTTP
                 = dyn_cast<NonTypeTemplateParmDecl>(Pack))
-      mangleTemplateParameter(NTTP->getIndex());
+      mangleTemplateParameter(NTTP->getDepth(), NTTP->getIndex());
     else if (const TemplateTemplateParmDecl *TempTP
                                     = dyn_cast<TemplateTemplateParmDecl>(Pack))
-      mangleTemplateParameter(TempTP->getIndex());
+      mangleTemplateParameter(TempTP->getDepth(), TempTP->getIndex());
     else
       mangleFunctionParam(cast<ParmVarDecl>(Pack));
     break;
@@ -4557,13 +4590,21 @@ void CXXNameMangler::mangleTemplateArg(TemplateArgument A) {
   }
 }
 
-void CXXNameMangler::mangleTemplateParameter(unsigned Index) {
+void CXXNameMangler::mangleTemplateParameter(unsigned Depth, unsigned Index) {
   // <template-param> ::= T_    # first template parameter
   //                  ::= T <parameter-2 non-negative number> _
-  if (Index == 0)
-    Out << "T_";
-  else
-    Out << 'T' << (Index - 1) << '_';
+  //                  ::= TL <L-1 non-negative number> __
+  //                  ::= TL <L-1 non-negative number> _
+  //                         <parameter-2 non-negative number> _
+  //
+  // The latter two manglings are from a proposal here:
+  // https://github.com/itanium-cxx-abi/cxx-abi/issues/31#issuecomment-528122117
+  Out << 'T';
+  if (Depth != 0)
+    Out << 'L' << (Depth - 1) << '_';
+  if (Index != 0)
+    Out << (Index - 1);
+  Out << '_';
 }
 
 void CXXNameMangler::mangleSeqID(unsigned SeqID) {
@@ -5080,6 +5121,12 @@ void ItaniumMangleContextImpl::mangleStringLiteral(const StringLiteral *, raw_os
   llvm_unreachable("Can't mangle string literals");
 }
 
+void ItaniumMangleContextImpl::mangleLambdaSig(const CXXRecordDecl *Lambda,
+                                               raw_ostream &Out) {
+  CXXNameMangler Mangler(*this, Out);
+  Mangler.mangleLambdaSig(Lambda);
+}
+
 ItaniumMangleContext *
 ItaniumMangleContext::create(ASTContext &Context, DiagnosticsEngine &Diags) {
   return new ItaniumMangleContextImpl(Context, Diags);

lib/Sema/SemaLambda.cpp

@@ -407,6 +407,8 @@ CXXMethodDecl *Sema::startLambdaDefinition(
       MethodType, MethodTypeInfo, SC_None,
       /*isInline=*/true, ConstexprKind, EndLoc);
   Method->setAccess(AS_public);
+  if (!TemplateParams)
+    Class->addDecl(Method);
 
   // Temporarily set the lexical declaration context to the current
   // context, so that the Scope stack matches the lexical nesting.
@@ -418,9 +420,10 @@ CXXMethodDecl *Sema::startLambdaDefinition(
                                          TemplateParams,
                                          Method) : nullptr;
   if (TemplateMethod) {
-    TemplateMethod->setLexicalDeclContext(CurContext);
     TemplateMethod->setAccess(AS_public);
     Method->setDescribedFunctionTemplate(TemplateMethod);
+    Class->addDecl(TemplateMethod);
+    TemplateMethod->setLexicalDeclContext(CurContext);
   }
 
   // Add parameters.
@@ -1641,8 +1644,9 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
         ? CallOperator->getDescribedFunctionTemplate()
         : cast<Decl>(CallOperator);
 
+    // FIXME: Is this really the best choice? Keeping the lexical decl context
+    // set as CurContext seems more faithful to the source.
     TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
-    Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
 
     PopExpressionEvaluationContext();
 

test/CodeGenCXX/mangle-lambda-explicit-template-params.cpp

@@ -33,9 +33,68 @@ void call_inline_func() {
   inline_func();
 }
 
+template<typename T, int> struct X {};
+
+inline auto pack = []<typename ...T, T ...N>(T (&...)[N]) {};
+int arr1[] = {1};
+int arr2[] = {1, 2};
+// CHECK: @_ZNK4packMUlTpTyTpTnT_DpRAT0__S_E_clIJiiEJLi1ELi2EEEEDaS2_(
+void use_pack() { pack(arr1, arr2); }
+
+inline void collision() {
+  auto a = []<typename T, template<typename U, T> typename>{};
+  auto b = []<typename T, template<typename U, U> typename>{};
+  auto c = []<typename T, template<typename U, T> typename>{};
+  a.operator()<int, X>();
+  // CHECK: @_ZZ9collisionvENKUlTyTtTyTnT_EvE_clIi1XEEDav
+  b.operator()<int, X>();
+  // CHECK: @_ZZ9collisionvENKUlTyTtTyTnTL0__EvE_clIi1XEEDav
+  c.operator()<int, X>();
+  // CHECK: @_ZZ9collisionvENKUlTyTtTyTnT_EvE0_clIi1XEEDav
+}
+void use_collision() { collision(); }
+
 template<typename> void f() {
   // CHECK: define linkonce_odr {{.*}} @_ZZ1fIiEvvENKUlT_E_clIiEEDaS0_(
   auto x = [](auto){};
   x(0);
 }
 void use_f() { f<int>(); }
+
+template<typename> struct Y {
+  template<int> struct Z {};
+};
+
+template<typename ...T> void expanded() {
+  auto x = []<T..., template<T> typename...>{};
+  auto y = []<int, template<int> typename>{};
+  auto z = []<int, int, template<int> typename, template<int> typename>{};
+  // FIXME: Should we really require 'template' for y and z?
+  x.template operator()<(T())..., Y<T>::template Z...>();
+  y.template operator()<0, Y<int>::Z>();
+  y.template operator()<1, Y<int>::Z>();
+  z.template operator()<1, 2, Y<int>::Z, Y<float>::Z>();
+}
+void use_expanded() {
+  // CHECK: @_ZZ8expandedIJEEvvENKUlvE_clIJEJEEEDav(
+  // CHECK: @_ZZ8expandedIJEEvvENKUlTniTtTniEvE_clILi0EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJEEvvENKUlTniTtTniEvE_clILi1EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJEEvvENKUlTniTniTtTniETtTniEvE_clILi1ELi2EN1YIiE1ZENS2_IfE1ZEEEDav(
+  expanded<>();
+
+  // FIXME: Should we really be using J...E for arguments corresponding to an
+  // expanded parameter pack?
+  // Note that the <lambda-sig>s of 'x' and 'y' collide here, after pack expansion.
+  // CHECK: @_ZZ8expandedIJiEEvvENKUlTniTtTniEvE_clIJLi0EEJN1YIiE1ZEEEEDav(
+  // CHECK: @_ZZ8expandedIJiEEvvENKUlTniTtTniEvE0_clILi0EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJiEEvvENKUlTniTtTniEvE0_clILi1EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJiEEvvENKUlTniTniTtTniETtTniEvE_clILi1ELi2EN1YIiE1ZENS2_IfE1ZEEEDav(
+  expanded<int>();
+
+  // Note that the <lambda-sig>s of 'x' and 'z' collide here, after pack expansion.
+  // CHECK: @_ZZ8expandedIJiiEEvvENKUlTniTniTtTniETtTniEvE_clIJLi0ELi0EEJN1YIiE1ZES4_EEEDav(
+  // CHECK: @_ZZ8expandedIJiiEEvvENKUlTniTtTniEvE_clILi0EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJiiEEvvENKUlTniTtTniEvE_clILi1EN1YIiE1ZEEEDav(
+  // CHECK: @_ZZ8expandedIJiiEEvvENKUlTniTniTtTniETtTniEvE0_clILi1ELi2EN1YIiE1ZENS2_IfE1ZEEEDav(
+  expanded<int, int>();
+}