Deal with a horrible C++11 special case. If a non-literal type has a constexpr

constructor, and that constructor is used to initialize an object of static
storage duration such that all members and bases are initialized by constant
expressions, constant initialization is performed. In this case, the object
can still have a non-trivial destructor, and if it does, we must emit a dynamic
initializer which performs no initialization and instead simply registers that
destructor.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150419 91177308-0d34-0410-b5e6-96231b3b80d8

11 files changed, 92 insertions, 43 deletions

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 520e3cbbaf..c0fff5e478 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -855,7 +855,8 @@ static bool Evaluate(CCValue &Result, EvalInfo &Info, const Expr *E);
 static bool EvaluateConstantExpression(APValue &Result, EvalInfo &Info,
                                        const LValue &This, const Expr *E,
                                        CheckConstantExpressionKind CCEK
-                                        = CCEK_Constant);
+                                        = CCEK_Constant,
+                                       bool AllowNonLiteralTypes = false);
 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info);
 static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info);
 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
@@ -5829,8 +5830,9 @@ static bool Evaluate(CCValue &Result, EvalInfo &Info, const Expr *E) {
 /// which were initialized earlier.
 static bool EvaluateConstantExpression(APValue &Result, EvalInfo &Info,
                                        const LValue &This, const Expr *E,
-                                       CheckConstantExpressionKind CCEK) {
-  if (!CheckLiteralType(Info, E))
+                                       CheckConstantExpressionKind CCEK,
+                                       bool AllowNonLiteralTypes) {
+  if (!AllowNonLiteralTypes && !CheckLiteralType(Info, E))
     return false;
 
   if (E->isRValue()) {
@@ -5941,9 +5943,6 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
   EvalInfo InitInfo(Ctx, EStatus);
   InitInfo.setEvaluatingDecl(VD, Value);
 
-  if (!CheckLiteralType(InitInfo, this))
-    return false;
-
   LValue LVal;
   LVal.set(VD);
 
@@ -5954,11 +5953,13 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
   if (Ctx.getLangOptions().CPlusPlus && !VD->hasLocalStorage() &&
       !VD->getType()->isReferenceType()) {
     ImplicitValueInitExpr VIE(VD->getType());
-    if (!EvaluateConstantExpression(Value, InitInfo, LVal, &VIE))
+    if (!EvaluateConstantExpression(Value, InitInfo, LVal, &VIE, CCEK_Constant,
+                                    /*AllowNonLiteralTypes=*/true))
       return false;
   }
 
-  return EvaluateConstantExpression(Value, InitInfo, LVal, this) &&
+  return EvaluateConstantExpression(Value, InitInfo, LVal, this, CCEK_Constant,
+                                    /*AllowNonLiteralTypes=*/true) &&
          !EStatus.HasSideEffects;
 }
 
diff --git a/lib/CodeGen/CGCXXABI.cpp b/lib/CodeGen/CGCXXABI.cpp
index c1b20af799..e5d3f2da6b 100644
--- a/lib/CodeGen/CGCXXABI.cpp
+++ b/lib/CodeGen/CGCXXABI.cpp
@@ -168,6 +168,7 @@ void CGCXXABI::ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
 
 void CGCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
                                const VarDecl &D,
-                               llvm::GlobalVariable *GV) {
+                               llvm::GlobalVariable *GV,
+                               bool PerformInit) {
   ErrorUnsupportedABI(CGF, "static local variable initialization");
 }
diff --git a/lib/CodeGen/CGCXXABI.h b/lib/CodeGen/CGCXXABI.h
index 5e21bb0c9f..4bacd01403 100644
--- a/lib/CodeGen/CGCXXABI.h
+++ b/lib/CodeGen/CGCXXABI.h
@@ -226,12 +226,14 @@ public:
 
   /// Emits the guarded initializer and destructor setup for the given
   /// variable, given that it couldn't be emitted as a constant.
+  /// If \p PerformInit is false, the initialization has been folded to a
+  /// constant and should not be performed.
   ///
   /// The variable may be:
   ///   - a static local variable
   ///   - a static data member of a class template instantiation
   virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
-                               llvm::GlobalVariable *DeclPtr);
+                               llvm::GlobalVariable *DeclPtr, bool PerformInit);
 
 };
 
diff --git a/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp
index 3d32091a4b..2de19840e5 100644
--- a/lib/CodeGen/CGDecl.cpp
+++ b/lib/CodeGen/CGDecl.cpp
@@ -196,6 +196,14 @@ CodeGenFunction::CreateStaticVarDecl(const VarDecl &D,
   return GV;
 }
 
+/// hasNontrivialDestruction - Determine whether a type's destruction is
+/// non-trivial. If so, and the variable uses static initialization, we must
+/// register its destructor to run on exit.
+static bool hasNontrivialDestruction(QualType T) {
+  CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
+  return RD && !RD->hasTrivialDestructor();
+}
+
 /// AddInitializerToStaticVarDecl - Add the initializer for 'D' to the
 /// global variable that has already been created for it.  If the initializer
 /// has a different type than GV does, this may free GV and return a different
@@ -215,7 +223,7 @@ CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D,
       // be constant.
       GV->setConstant(false);
 
-      EmitCXXGuardedInit(D, GV);
+      EmitCXXGuardedInit(D, GV, /*PerformInit*/true);
     }
     return GV;
   }
@@ -248,6 +256,16 @@ CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D,
   }
 
   GV->setInitializer(Init);
+
+  if (hasNontrivialDestruction(D.getType())) {
+    // We have a constant initializer, but a nontrivial destructor. We still
+    // need to perform a guarded "initialization" in order to register the
+    // destructor. Since we're running a destructor on this variable, it can't
+    // be a constant even if it's const.
+    GV->setConstant(false);
+    EmitCXXGuardedInit(D, GV, /*PerformInit*/false);
+  }
+
   return GV;
 }
 
diff --git a/lib/CodeGen/CGDeclCXX.cpp b/lib/CodeGen/CGDeclCXX.cpp
index 8406002e5a..44acf62aa6 100644
--- a/lib/CodeGen/CGDeclCXX.cpp
+++ b/lib/CodeGen/CGDeclCXX.cpp
@@ -102,17 +102,21 @@ static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
 }
 
 void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
-                                               llvm::Constant *DeclPtr) {
+                                               llvm::Constant *DeclPtr,
+                                               bool PerformInit) {
 
   const Expr *Init = D.getInit();
   QualType T = D.getType();
 
   if (!T->isReferenceType()) {
-    EmitDeclInit(*this, D, DeclPtr);
+    if (PerformInit)
+      EmitDeclInit(*this, D, DeclPtr);
     EmitDeclDestroy(*this, D, DeclPtr);
     return;
   }
 
+  assert(PerformInit && "cannot have constant initializer which needs "
+         "destruction for reference");
   unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
   RValue RV = EmitReferenceBindingToExpr(Init, &D);
   EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
@@ -152,7 +156,8 @@ CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
 }
 
 void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
-                                         llvm::GlobalVariable *DeclPtr) {
+                                         llvm::GlobalVariable *DeclPtr,
+                                         bool PerformInit) {
   // If we've been asked to forbid guard variables, emit an error now.
   // This diagnostic is hard-coded for Darwin's use case;  we can find
   // better phrasing if someone else needs it.
@@ -161,7 +166,7 @@ void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
               "this initialization requires a guard variable, which "
               "the kernel does not support");
 
-  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr);
+  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
 }
 
 static llvm::Function *
@@ -186,14 +191,16 @@ CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
 
 void
 CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
-                                            llvm::GlobalVariable *Addr) {
+                                            llvm::GlobalVariable *Addr,
+                                            bool PerformInit) {
   llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
 
   // Create a variable initialization function.
   llvm::Function *Fn =
     CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
 
-  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr);
+  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
+                                                          PerformInit);
 
   if (D->hasAttr<InitPriorityAttr>()) {
     unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
@@ -267,7 +274,8 @@ void CodeGenModule::EmitCXXGlobalDtorFunc() {
 /// Emit the code necessary to initialize the given global variable.
 void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
                                                        const VarDecl *D,
-                                                 llvm::GlobalVariable *Addr) {
+                                                 llvm::GlobalVariable *Addr,
+                                                       bool PerformInit) {
   StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
                 getTypes().getNullaryFunctionInfo(),
                 FunctionArgList(), SourceLocation());
@@ -277,9 +285,9 @@ void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
   // definitions explicitly marked weak.
   if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage ||
       Addr->getLinkage() == llvm::GlobalValue::WeakAnyLinkage) {
-    EmitCXXGuardedInit(*D, Addr);
+    EmitCXXGuardedInit(*D, Addr, PerformInit);
   } else {
-    EmitCXXGlobalVarDeclInit(*D, Addr);
+    EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
   }
 
   FinishFunction();
@@ -357,4 +365,3 @@ CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
   
   return fn;
 }
-
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index ccb4b930e6..0b3ac9cbe5 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -939,6 +939,15 @@ llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D,
   if (const APValue *Value = D.evaluateValue())
     return EmitConstantValue(*Value, D.getType(), CGF);
 
+  // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
+  // reference is a constant expression, and the reference binds to a temporary,
+  // then constant initialization is performed. ConstExprEmitter will
+  // incorrectly emit a prvalue constant in this case, and the calling code
+  // interprets that as the (pointer) value of the reference, rather than the
+  // desired value of the referee.
+  if (D.getType()->isReferenceType())
+    return 0;
+
   const Expr *E = D.getInit();
   assert(E && "No initializer to emit");
 
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 277640b8ce..ca5b88363e 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -2361,7 +2361,8 @@ public:
 
   /// EmitCXXGlobalVarDeclInit - Create the initializer for a C++
   /// variable with global storage.
-  void EmitCXXGlobalVarDeclInit(const VarDecl &D, llvm::Constant *DeclPtr);
+  void EmitCXXGlobalVarDeclInit(const VarDecl &D, llvm::Constant *DeclPtr,
+                                bool PerformInit);
 
   /// EmitCXXGlobalDtorRegistration - Emits a call to register the global ptr
   /// with the C++ runtime so that its destructor will be called at exit.
@@ -2373,7 +2374,8 @@ public:
   /// possible to prove that an initialization will be done exactly
   /// once, e.g. with a static local variable or a static data member
   /// of a class template.
-  void EmitCXXGuardedInit(const VarDecl &D, llvm::GlobalVariable *DeclPtr);
+  void EmitCXXGuardedInit(const VarDecl &D, llvm::GlobalVariable *DeclPtr,
+                          bool PerformInit);
 
   /// GenerateCXXGlobalInitFunc - Generates code for initializing global
   /// variables.
@@ -2389,7 +2391,8 @@ public:
 
   void GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
                                         const VarDecl *D,
-                                        llvm::GlobalVariable *Addr);
+                                        llvm::GlobalVariable *Addr,
+                                        bool PerformInit);
 
   void EmitCXXConstructExpr(const CXXConstructExpr *E, AggValueSlot Dest);
   
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index fde217efec..2ebea59264 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -1359,7 +1359,9 @@ CharUnits CodeGenModule::GetTargetTypeStoreSize(llvm::Type *Ty) const {
 void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   llvm::Constant *Init = 0;
   QualType ASTTy = D->getType();
-  bool NonConstInit = false;
+  CXXRecordDecl *RD = ASTTy->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
+  bool NeedsGlobalCtor = false;
+  bool NeedsGlobalDtor = RD && !RD->hasTrivialDestructor();
 
   const VarDecl *InitDecl;
   const Expr *InitExpr = D->getAnyInitializer(InitDecl);
@@ -1385,15 +1387,16 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
 
       if (getLangOptions().CPlusPlus) {
         Init = EmitNullConstant(T);
-        NonConstInit = true;
+        NeedsGlobalCtor = true;
       } else {
         ErrorUnsupported(D, "static initializer");
         Init = llvm::UndefValue::get(getTypes().ConvertType(T));
       }
     } else {
       // We don't need an initializer, so remove the entry for the delayed
-      // initializer position (just in case this entry was delayed).
-      if (getLangOptions().CPlusPlus)
+      // initializer position (just in case this entry was delayed) if we
+      // also don't need to register a destructor.
+      if (getLangOptions().CPlusPlus && !NeedsGlobalDtor)
         DelayedCXXInitPosition.erase(D);
     }
   }
@@ -1448,7 +1451,8 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
 
   // If it is safe to mark the global 'constant', do so now.
   GV->setConstant(false);
-  if (!NonConstInit && DeclIsConstantGlobal(Context, D, true))
+  if (!NeedsGlobalCtor && !NeedsGlobalDtor &&
+      DeclIsConstantGlobal(Context, D, true))
     GV->setConstant(true);
 
   GV->setAlignment(getContext().getDeclAlign(D).getQuantity());
@@ -1464,8 +1468,8 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
   SetCommonAttributes(D, GV);
 
   // Emit the initializer function if necessary.
-  if (NonConstInit)
-    EmitCXXGlobalVarDeclInitFunc(D, GV);
+  if (NeedsGlobalCtor || NeedsGlobalDtor)
+    EmitCXXGlobalVarDeclInitFunc(D, GV, NeedsGlobalCtor);
 
   // Emit global variable debug information.
   if (CGDebugInfo *DI = getModuleDebugInfo())
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index 08e1ed7fb1..6813edd5f1 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -900,8 +900,11 @@ private:
   /// EmitCXXGlobalDtorFunc - Emit the function that destroys C++ globals.
   void EmitCXXGlobalDtorFunc();
 
+  /// EmitCXXGlobalVarDeclInitFunc - Emit the function that initializes the
+  /// specified global (if PerformInit is true) and registers its destructor.
   void EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
-                                    llvm::GlobalVariable *Addr);
+                                    llvm::GlobalVariable *Addr,
+                                    bool PerformInit);
 
   // FIXME: Hardcoding priority here is gross.
   void AddGlobalCtor(llvm::Function *Ctor, int Priority=65535);
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 044b7f0532..8dee17a38c 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -121,7 +121,7 @@ public:
                        llvm::Value *&AllocPtr, CharUnits &CookieSize);
 
   void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
-                       llvm::GlobalVariable *DeclPtr);
+                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
 };
 
 class ARMCXXABI : public ItaniumCXXABI {
@@ -1016,7 +1016,8 @@ namespace {
 /// just special-case it at particular places.
 void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
                                     const VarDecl &D,
-                                    llvm::GlobalVariable *GV) {
+                                    llvm::GlobalVariable *GV,
+                                    bool PerformInit) {
   CGBuilderTy &Builder = CGF.Builder;
 
   // We only need to use thread-safe statics for local variables;
@@ -1129,7 +1130,7 @@ void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
   }
 
   // Emit the initializer and add a global destructor if appropriate.
-  CGF.EmitCXXGlobalVarDeclInit(D, GV);
+  CGF.EmitCXXGlobalVarDeclInit(D, GV, PerformInit);
 
   if (threadsafe) {
     // Pop the guard-abort cleanup if we pushed one.
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 3c73f689e7..de9feccaf3 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -3991,15 +3991,8 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                                            TemplateParamLists.release());
     }
 
-    if (D.getDeclSpec().isConstexprSpecified()) {
+    if (D.getDeclSpec().isConstexprSpecified())
       NewVD->setConstexpr(true);
-      SourceLocation ConstexprLoc = D.getDeclSpec().getConstexprSpecLoc();
-      if (!NewVD->isInvalidDecl() && !R->isDependentType() &&
-          RequireLiteralType(NewVD->getLocation(), R,
-                             PDiag(diag::err_constexpr_var_non_literal)
-                               << SourceRange(ConstexprLoc)))
-        NewVD->setInvalidDecl();
-    }
   }
 
   // Set the lexical context. If the declarator has a C++ scope specifier, the
@@ -4347,6 +4340,13 @@ bool Sema::CheckVariableDeclaration(VarDecl *NewVD,
     return false;
   }
 
+  if (NewVD->isConstexpr() && !T->isDependentType() &&
+      RequireLiteralType(NewVD->getLocation(), T,
+                         PDiag(diag::err_constexpr_var_non_literal))) {
+    NewVD->setInvalidDecl();
+    return false;
+  }
+
   if (!Previous.empty()) {
     MergeVarDecl(NewVD, Previous);
     return true;