Fully implement delegating constructors!

As far as I know, this implementation is complete but might be missing a
few optimizations. Exceptions and virtual bases are handled correctly.

Because I'm an optimist, the web page has appropriately been updated. If
I'm wrong, feel free to downgrade its support categories.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@130642 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/DeclCXX.h

@@ -1608,6 +1608,23 @@ public:
   void setCtorInitializers(CXXCtorInitializer ** initializers) {
     CtorInitializers = initializers;
   }
+
+  /// isDelegatingConstructor - Whether this constructor is a
+  /// delegating constructor
+  bool isDelegatingConstructor() const {
+    return (getNumCtorInitializers() == 1) &&
+      CtorInitializers[0]->isDelegatingInitializer();
+  }
+
+  /// getTargetConstructor - When this constructor delegates to
+  /// another, retrieve the target
+  CXXConstructorDecl *getTargetConstructor() const {
+    if (isDelegatingConstructor())
+      return CtorInitializers[0]->getTargetConstructor();
+    else
+      return 0;
+  }
+
   /// isDefaultConstructor - Whether this constructor is a default
   /// constructor (C++ [class.ctor]p5), which can be used to
   /// default-initialize a class of this type.

include/clang/AST/ExprCXX.h

@@ -780,7 +780,8 @@ public:
   enum ConstructionKind {
     CK_Complete,
     CK_NonVirtualBase,
-    CK_VirtualBase
+    CK_VirtualBase,
+    CK_Delegating
   };
     
 private:

include/clang/Basic/DiagnosticSemaKinds.td

@@ -1008,6 +1008,10 @@ def err_delegation_unimplemented : Error<
   "delegating constructors are not fully implemented">;
 def err_delegating_initializer_alone : Error<
   "an initializer for a delegating constructor must appear alone">;
+def err_delegating_ctor_loop : Error<
+  "constructor %0 delegates to itself (possibly indirectly)">;
+def err_delegating_codegen_not_implemented : Error<
+  "code generation for delegating constructors not implemented">;
 
 // C++0x range-based for loop
 def err_for_range_decl_must_be_var : Error<

include/clang/Sema/Initialization.h

@@ -65,7 +65,7 @@ public:
     /// \brief The entity being initialized is a base member subobject.
     EK_Base,
     /// \brief The initialization is being done by a delegating constructor.
-    EK_Delegation,
+    EK_Delegating,
     /// \brief The entity being initialized is an element of a vector.
     /// or vector.
     EK_VectorElement,
@@ -215,7 +215,7 @@ public:
 
   /// \brief Create the initialization entity for a delegated constructor.
   static InitializedEntity InitializeDelegation(QualType Type) {
-    return InitializedEntity(EK_Delegation, SourceLocation(), Type);
+    return InitializedEntity(EK_Delegating, SourceLocation(), Type);
   }
   
   /// \brief Create the initialization entity for a member subobject.

include/clang/Sema/Sema.h

@@ -3072,6 +3072,9 @@ public:
                                            SourceLocation LParenLoc,
                                            CXXRecordDecl *ClassDecl);
 
+  bool SetDelegatingInitializer(CXXConstructorDecl *Constructor,
+                                CXXCtorInitializer *Initializer);
+
   bool SetCtorInitializers(CXXConstructorDecl *Constructor,
                            CXXCtorInitializer **Initializers,
                            unsigned NumInitializers, bool AnyErrors);

lib/CodeGen/CGClass.cpp

@@ -658,6 +658,10 @@ static bool IsConstructorDelegationValid(const CXXConstructorDecl *Ctor) {
   if (Ctor->getType()->getAs<FunctionProtoType>()->isVariadic())
     return false;
 
+  // FIXME: Decide if we can do a delegation of a delegating constructor.
+  if (Ctor->isDelegatingConstructor())
+    return false;
+
   return true;
 }
 
@@ -710,6 +714,9 @@ void CodeGenFunction::EmitConstructorBody(FunctionArgList &Args) {
 void CodeGenFunction::EmitCtorPrologue(const CXXConstructorDecl *CD,
                                        CXXCtorType CtorType,
                                        FunctionArgList &Args) {
+  if (CD->isDelegatingConstructor())
+    return EmitDelegatingCXXConstructorCall(CD, Args);
+
   const CXXRecordDecl *ClassDecl = CD->getParent();
 
   llvm::SmallVector<CXXCtorInitializer *, 8> MemberInitializers;
@@ -721,8 +728,10 @@ void CodeGenFunction::EmitCtorPrologue(const CXXConstructorDecl *CD,
     
     if (Member->isBaseInitializer())
       EmitBaseInitializer(*this, ClassDecl, Member, CtorType);
-    else
+    else if (Member->isAnyMemberInitializer())
       MemberInitializers.push_back(Member);
+    else
+      llvm_unreachable("Delegating initializer on non-delegating constructor");
   }
 
   InitializeVTablePointers(ClassDecl);
@@ -1262,6 +1271,19 @@ CodeGenFunction::EmitDelegateCXXConstructorCall(const CXXConstructorDecl *Ctor,
            ReturnValueSlot(), DelegateArgs, Ctor);
 }
 
+void
+CodeGenFunction::EmitDelegatingCXXConstructorCall(const CXXConstructorDecl *Ctor,
+                                                  const FunctionArgList &Args) {
+  assert(Ctor->isDelegatingConstructor());
+
+  llvm::Value *ThisPtr = LoadCXXThis();
+
+  AggValueSlot AggSlot = AggValueSlot::forAddr(ThisPtr, false, /*Lifetime*/ true);
+
+  EmitAggExpr(Ctor->init_begin()[0]->getInit(), AggSlot);
+}
+
+
 void CodeGenFunction::EmitCXXDestructorCall(const CXXDestructorDecl *DD,
                                             CXXDtorType Type,
                                             bool ForVirtualBase,

lib/CodeGen/CGExprCXX.cpp

@@ -404,9 +404,16 @@ CodeGenFunction::EmitCXXConstructExpr(const CXXConstructExpr *E,
                                E->arg_begin(), E->arg_end());
   }
   else {
-    CXXCtorType Type = 
-      (E->getConstructionKind() == CXXConstructExpr::CK_Complete) 
-      ? Ctor_Complete : Ctor_Base;
+    CXXCtorType Type;
+    CXXConstructExpr::ConstructionKind K = E->getConstructionKind();
+    if (K == CXXConstructExpr::CK_Delegating) {
+      // We should be emitting a constructor; GlobalDecl will assert this
+      Type = CurGD.getCtorType();
+    } else {
+      Type = (E->getConstructionKind() == CXXConstructExpr::CK_Complete)
+             ? Ctor_Complete : Ctor_Base;
+    }
+
     bool ForVirtualBase = 
       E->getConstructionKind() == CXXConstructExpr::CK_VirtualBase;
     

lib/CodeGen/CodeGenFunction.h

@@ -1496,6 +1496,12 @@ public:
   void EmitDelegateCXXConstructorCall(const CXXConstructorDecl *Ctor,
                                       CXXCtorType CtorType,
                                       const FunctionArgList &Args);
+  // It's important not to confuse this and the previous function. Delegating
+  // constructors are the C++0x feature. The constructor delegate optimization
+  // is used to reduce duplication in the base and complete consturctors where
+  // they are substantially the same.
+  void EmitDelegatingCXXConstructorCall(const CXXConstructorDecl *Ctor,
+                                        const FunctionArgList &Args);
   void EmitCXXConstructorCall(const CXXConstructorDecl *D, CXXCtorType Type,
                               bool ForVirtualBase, llvm::Value *This,
                               CallExpr::const_arg_iterator ArgBeg,

lib/Lex/PPMacroExpansion.cpp

@@ -561,6 +561,7 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
            .Case("cxx_auto_type", LangOpts.CPlusPlus0x)
            .Case("cxx_decltype", LangOpts.CPlusPlus0x)
            .Case("cxx_default_function_template_args", LangOpts.CPlusPlus0x)
+           .Case("cxx_delegating_constructors", LangOpts.CPlusPlus0x)
            .Case("cxx_deleted_functions", LangOpts.CPlusPlus0x)
            .Case("cxx_inline_namespaces", LangOpts.CPlusPlus0x)
          //.Case("cxx_lambdas", false)

lib/Sema/SemaDeclCXX.cpp

@@ -2068,6 +2068,30 @@ static bool CollectFieldInitializer(BaseAndFieldInfo &Info,
 
   return false;
 }
+
+bool
+Sema::SetDelegatingInitializer(CXXConstructorDecl *Constructor,
+                               CXXCtorInitializer *Initializer) {
+  Constructor->setNumCtorInitializers(1);
+  CXXCtorInitializer **initializer =
+    new (Context) CXXCtorInitializer*[1];
+  memcpy(initializer, &Initializer, sizeof (CXXCtorInitializer*));
+  Constructor->setCtorInitializers(initializer);
+
+  // FIXME: This doesn't catch indirect loops yet
+  CXXConstructorDecl *Target = Initializer->getTargetConstructor();
+  while (Target) {
+    if (Target == Constructor) {
+      Diag(Initializer->getSourceLocation(), diag::err_delegating_ctor_loop)
+        << Constructor;
+      return true;
+    }
+    Target = Target->getTargetConstructor();
+  }
+
+  return false;
+}
+
                                
 bool
 Sema::SetCtorInitializers(CXXConstructorDecl *Constructor,
@@ -2442,7 +2466,11 @@ void Sema::ActOnMemInitializers(Decl *ConstructorDecl,
              diag::err_delegating_initializer_alone)
           << MemInits[0]->getSourceRange();
         HadError = true;
+        // We will treat this as being the only initializer.
       }
+      SetDelegatingInitializer(Constructor, *MemInits);
+      // Return immediately as the initializer is set.
+      return;
     }
   }
 

lib/Sema/SemaInit.cpp

@@ -2045,7 +2045,7 @@ DeclarationName InitializedEntity::getName() const {
   case EK_New:
   case EK_Temporary:
   case EK_Base:
-  case EK_Delegation:
+  case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
   case EK_BlockElement:
@@ -2068,7 +2068,7 @@ DeclaratorDecl *InitializedEntity::getDecl() const {
   case EK_New:
   case EK_Temporary:
   case EK_Base:
-  case EK_Delegation:
+  case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
   case EK_BlockElement:
@@ -2091,7 +2091,7 @@ bool InitializedEntity::allowsNRVO() const {
   case EK_New:
   case EK_Temporary:
   case EK_Base:
-  case EK_Delegation:
+  case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
   case EK_BlockElement:
@@ -3346,7 +3346,7 @@ getAssignmentAction(const InitializedEntity &Entity) {
   case InitializedEntity::EK_New:
   case InitializedEntity::EK_Exception:
   case InitializedEntity::EK_Base:
-  case InitializedEntity::EK_Delegation:
+  case InitializedEntity::EK_Delegating:
     return Sema::AA_Initializing;
 
   case InitializedEntity::EK_Parameter:
@@ -3383,7 +3383,7 @@ static bool shouldBindAsTemporary(const InitializedEntity &Entity) {
   case InitializedEntity::EK_New:
   case InitializedEntity::EK_Variable:
   case InitializedEntity::EK_Base:
-  case InitializedEntity::EK_Delegation:
+  case InitializedEntity::EK_Delegating:
   case InitializedEntity::EK_VectorElement:
   case InitializedEntity::EK_Exception:
   case InitializedEntity::EK_BlockElement:
@@ -3405,7 +3405,7 @@ static bool shouldDestroyTemporary(const InitializedEntity &Entity) {
     case InitializedEntity::EK_Result:
     case InitializedEntity::EK_New:
     case InitializedEntity::EK_Base:
-    case InitializedEntity::EK_Delegation:
+    case InitializedEntity::EK_Delegating:
     case InitializedEntity::EK_VectorElement:
     case InitializedEntity::EK_BlockElement:
       return false;
@@ -3490,7 +3490,7 @@ static ExprResult CopyObject(Sema &S,
   case InitializedEntity::EK_Temporary:
   case InitializedEntity::EK_New:
   case InitializedEntity::EK_Base:
-  case InitializedEntity::EK_Delegation:
+  case InitializedEntity::EK_Delegating:
   case InitializedEntity::EK_VectorElement:
   case InitializedEntity::EK_BlockElement:
     Loc = CurInitExpr->getLocStart();
@@ -4061,6 +4061,9 @@ InitializationSequence::Perform(Sema &S,
             CXXConstructExpr::CK_VirtualBase :
             CXXConstructExpr::CK_NonVirtualBase;
         }
+        if (Entity.getKind() == InitializedEntity::EK_Delegating) {
+          ConstructKind = CXXConstructExpr::CK_Delegating;
+        }
 
         // Only get the parenthesis range if it is a direct construction.
         SourceRange parenRange =

test/CodeGenCXX/cxx0x-delegating-ctors.cpp

@@ -0,0 +1,48 @@
+// RUN: %clang_cc1 -emit-llvm -fexceptions -fcxx-exceptions -std=c++0x -o - %s | FileCheck %s
+
+struct non_trivial {
+  non_trivial();
+  ~non_trivial();
+};
+non_trivial::non_trivial() {}
+non_trivial::~non_trivial() {}
+
+// We use a virtual base to ensure that the constructor
+// delegation optimization (complete->base) can't be
+// performed.
+struct delegator {
+  non_trivial n; 
+  delegator();
+  delegator(int);
+  delegator(char);
+  delegator(bool);
+};
+
+delegator::delegator() {
+  throw 0;
+}
+
+// CHECK: define void @_ZN9delegatorC1Ei
+// CHECK: call void @_ZN9delegatorC1Ev
+// CHECK-NOT: lpad
+// CHECK: ret
+// CHECK-NOT: lpad
+// CHECK: define void @_ZN9delegatorC2Ei
+// CHECK: call void @_ZN9delegatorC2Ev
+// CHECK-NOT: lpad
+// CHECK: ret
+// CHECK-NOT: lpad
+delegator::delegator(int)
+  : delegator()
+{}
+
+delegator::delegator(bool)
+{}
+
+// CHECK: define void @_ZN9delegatorC2Ec
+// CHECK: call void @_ZN9delegatorC2Eb
+// CHECK: call void @__cxa_throw
+delegator::delegator(char)
+  : delegator(true) {
+  throw 0;
+}

test/SemaCXX/cxx0x-delegating-ctors.cpp

@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++0x -verify %s
+
+struct foo {
+  int i;
+  foo();
+  foo(int);
+  foo(int, int);
+  foo(bool);
+  foo(char);
+  foo(float*);
+  foo(float&);
+};
+
+// Good
+foo::foo (int i) : i(i) {
+}
+// Good
+foo::foo () : foo(-1) {
+}
+// Good
+foo::foo (int, int) : foo() {
+}
+
+foo::foo (bool) : foo(true) { // expected-error{{delegates to itself}}
+}
+
+// Good
+foo::foo (float* f) : foo(*f) {
+}
+
+// FIXME: This should error
+foo::foo (float &f) : foo(&f) {
+}
+
+foo::foo (char) : i(3), foo(3) { // expected-error{{must appear alone}}
+}

www/cxx_status.html

@@ -348,10 +348,10 @@ welcome!</p>
 <tr><td colspan="7" class="category">Class Modifications</td></tr>
 <tr>
   <td>delegating constructors</td>
-  <td></td>
-  <td></td>
-  <td></td>
-  <td></td>
+  <td class="complete"></td>
+  <td class="complete"></td>
+  <td class="complete"></td>
+  <td class="complete"></td>
   <td>12.6.2</td>
   <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2006/n1986">N1986</a></td>
 </tr>