Re-land [mangle] Fix mangling where an extra mangle context is required.

This reverts r374268 (git commit c34385d07c)

I think I reverted this by mistake, so I'm relanding it. While my bisect
found this revision, I think the crashes I'm seeing locally must be
environmental. Maybe the version of clang I'm using miscompiles tot
clang.

llvm-svn: 374269

clang/include/clang/AST/ASTContext.h

@@ -514,6 +514,8 @@ private:
   /// need to be consistently numbered for the mangler).
   llvm::DenseMap<const DeclContext *, std::unique_ptr<MangleNumberingContext>>
       MangleNumberingContexts;
+  llvm::DenseMap<const Decl *, std::unique_ptr<MangleNumberingContext>>
+      ExtraMangleNumberingContexts;
 
   /// Side-table of mangling numbers for declarations which rarely
   /// need them (like static local vars).
@@ -2812,6 +2814,9 @@ public:
   /// Retrieve the context for computing mangling numbers in the given
   /// DeclContext.
   MangleNumberingContext &getManglingNumberContext(const DeclContext *DC);
+  enum NeedExtraManglingDecl_t { NeedExtraManglingDecl };
+  MangleNumberingContext &getManglingNumberContext(NeedExtraManglingDecl_t,
+                                                   const Decl *D);
 
   std::unique_ptr<MangleNumberingContext> createMangleNumberingContext() const;
 

clang/include/clang/Sema/Sema.h

@@ -1045,13 +1045,6 @@ public:
     /// suffice, e.g., in a default function argument.
     Decl *ManglingContextDecl;
 
-    /// The context information used to mangle lambda expressions
-    /// and block literals within this context.
-    ///
-    /// This mangling information is allocated lazily, since most contexts
-    /// do not have lambda expressions or block literals.
-    std::unique_ptr<MangleNumberingContext> MangleNumbering;
-
     /// If we are processing a decltype type, a set of call expressions
     /// for which we have deferred checking the completeness of the return type.
     SmallVector<CallExpr *, 8> DelayedDecltypeCalls;
@@ -1080,12 +1073,7 @@ public:
                                       ExpressionKind ExprContext)
         : Context(Context), ParentCleanup(ParentCleanup),
           NumCleanupObjects(NumCleanupObjects), NumTypos(0),
-          ManglingContextDecl(ManglingContextDecl), MangleNumbering(),
-          ExprContext(ExprContext) {}
-
-    /// Retrieve the mangling numbering context, used to consistently
-    /// number constructs like lambdas for mangling.
-    MangleNumberingContext &getMangleNumberingContext(ASTContext &Ctx);
+          ManglingContextDecl(ManglingContextDecl), ExprContext(ExprContext) {}
 
     bool isUnevaluated() const {
       return Context == ExpressionEvaluationContext::Unevaluated ||

clang/lib/AST/ASTContext.cpp

@@ -10261,6 +10261,16 @@ ASTContext::getManglingNumberContext(const DeclContext *DC) {
   return *MCtx;
 }
 
+MangleNumberingContext &
+ASTContext::getManglingNumberContext(NeedExtraManglingDecl_t, const Decl *D) {
+  assert(LangOpts.CPlusPlus); // We don't need mangling numbers for plain C.
+  std::unique_ptr<MangleNumberingContext> &MCtx =
+      ExtraMangleNumberingContexts[D];
+  if (!MCtx)
+    MCtx = createMangleNumberingContext();
+  return *MCtx;
+}
+
 std::unique_ptr<MangleNumberingContext>
 ASTContext::createMangleNumberingContext() const {
   return ABI->createMangleNumberingContext();

clang/lib/Sema/SemaLambda.cpp

@@ -352,21 +352,13 @@ Sema::getCurrentMangleNumberContext(const DeclContext *DC,
     //  -- the initializers of inline variables
   case VariableTemplate:
     //  -- the initializers of templated variables
-    return &ExprEvalContexts.back().getMangleNumberingContext(Context);
+    return &Context.getManglingNumberContext(ASTContext::NeedExtraManglingDecl,
+                                             ManglingContextDecl);
   }
 
   llvm_unreachable("unexpected context");
 }
 
-MangleNumberingContext &
-Sema::ExpressionEvaluationContextRecord::getMangleNumberingContext(
-    ASTContext &Ctx) {
-  assert(ManglingContextDecl && "Need to have a context declaration");
-  if (!MangleNumbering)
-    MangleNumbering = Ctx.createMangleNumberingContext();
-  return *MangleNumbering;
-}
-
 CXXMethodDecl *Sema::startLambdaDefinition(
     CXXRecordDecl *Class, SourceRange IntroducerRange,
     TypeSourceInfo *MethodTypeInfo, SourceLocation EndLoc,

clang/test/CodeGenCXX/mangle-lambdas.cpp

@@ -178,18 +178,24 @@ void use_func_template() {
 }
 
 namespace std {
-  struct type_info;
+  struct type_info {
+    bool before(const type_info &) const noexcept;
+  };
 }
 namespace PR12123 {
   struct A { virtual ~A(); } g;
+  struct C { virtual ~C(); } k;
   struct B {
     void f(const std::type_info& x = typeid([]()->A& { return g; }()));
     void h();
+    void j(bool cond = typeid([]() -> A & { return g; }()).before(typeid([]() -> C & { return k; }())));
   };
-  void B::h() { f(); }
+  void B::h() { f(); j(); }
 }
 
 // CHECK-LABEL: define linkonce_odr dereferenceable({{[0-9]+}}) %"struct.PR12123::A"* @_ZZN7PR121231B1fERKSt9type_infoEd_NKUlvE_clEv
+// CHECK-LABEL: define linkonce_odr dereferenceable({{[0-9]+}}) %"struct.PR12123::A"* @_ZZN7PR121231B1jEbEd_NKUlvE_clEv
+// CHECK-LABEL: define linkonce_odr dereferenceable({{[0-9]+}}) %"struct.PR12123::C"* @_ZZN7PR121231B1jEbEd_NKUlvE0_clEv
 
 // CHECK-LABEL: define {{.*}} @_Z{{[0-9]*}}testVarargsLambdaNumberingv(
 inline int testVarargsLambdaNumbering() {