During codegen of a virtual call we would extract any casts in the expression

to see if we had an underlying final class or method, but we would then
use the cast type to do the call, resulting in a direct call to the wrong
method.

llvm-svn: 159212

clang/include/clang/AST/DeclCXX.h

@@ -1630,7 +1630,20 @@ public:
   /// supplied by IR generation to either forward to the function call operator
   /// or clone the function call operator.
   bool isLambdaStaticInvoker() const;
-  
+
+  /// \brief Find the method in RD that corresponds to this one.
+  ///
+  /// Find if RD or one of the classes it inherits from override this method.
+  /// If so, return it. RD is assumed to be a base class of the class defining
+  /// this method (or be the class itself).
+  CXXMethodDecl *
+  getCorrespondingMethodInClass(const CXXRecordDecl *RD);
+
+  const CXXMethodDecl *
+  getCorrespondingMethodInClass(const CXXRecordDecl *RD) const {
+    return const_cast<CXXMethodDecl*>(this)->getCorrespondingMethodInClass(RD);
+  }
+
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classof(const CXXMethodDecl *D) { return true; }

clang/include/clang/AST/Expr.h

@@ -665,6 +665,13 @@ public:
 
   static bool hasAnyTypeDependentArguments(llvm::ArrayRef<Expr *> Exprs);
 
+  /// \brief If we have class type (or pointer to class type), return the
+  /// class decl. Return NULL otherwise.
+  ///
+  /// If this expression is a cast, this method looks through it to find the
+  /// most derived decl that can be infered from the expression.
+  const CXXRecordDecl *getMostDerivedClassDeclForType() const;
+
   static bool classof(const Stmt *T) {
     return T->getStmtClass() >= firstExprConstant &&
            T->getStmtClass() <= lastExprConstant;

clang/lib/AST/DeclCXX.cpp

@@ -1269,6 +1269,55 @@ bool CXXRecordDecl::mayBeAbstract() const {
 
 void CXXMethodDecl::anchor() { }
 
+static bool recursivelyOverrides(const CXXMethodDecl *DerivedMD,
+                                 const CXXMethodDecl *BaseMD) {
+  for (CXXMethodDecl::method_iterator I = DerivedMD->begin_overridden_methods(),
+         E = DerivedMD->end_overridden_methods(); I != E; ++I) {
+    const CXXMethodDecl *MD = *I;
+    if (MD->getCanonicalDecl() == BaseMD->getCanonicalDecl())
+      return true;
+    if (recursivelyOverrides(MD, BaseMD))
+      return true;
+  }
+  return false;
+}
+
+CXXMethodDecl *
+CXXMethodDecl::getCorrespondingMethodInClass(const CXXRecordDecl *RD) {
+  if (this->getParent()->getCanonicalDecl() == RD->getCanonicalDecl())
+    return this;
+
+  // Lookup doesn't work for destructors, so handle them separately.
+  if (isa<CXXDestructorDecl>(this)) {
+    CXXMethodDecl *MD = RD->getDestructor();
+    if (recursivelyOverrides(MD, this))
+      return MD;
+    return NULL;
+  }
+
+  lookup_const_result Candidates = RD->lookup(getDeclName());
+  for (NamedDecl * const * I = Candidates.first; I != Candidates.second; ++I) {
+    CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(*I);
+    if (!MD)
+      continue;
+    if (recursivelyOverrides(MD, this))
+      return MD;
+  }
+
+  for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+         E = RD->bases_end(); I != E; ++I) {
+    const RecordType *RT = I->getType()->getAs<RecordType>();
+    if (!RT)
+      continue;
+    const CXXRecordDecl *Base = cast<CXXRecordDecl>(RT->getDecl());
+    CXXMethodDecl *T = this->getCorrespondingMethodInClass(Base);
+    if (T)
+      return T;
+  }
+
+  return NULL;
+}
+
 CXXMethodDecl *
 CXXMethodDecl::Create(ASTContext &C, CXXRecordDecl *RD,
                       SourceLocation StartLoc,

clang/lib/AST/Expr.cpp

@@ -33,6 +33,37 @@
 #include <cstring>
 using namespace clang;
 
+const CXXRecordDecl *Expr::getMostDerivedClassDeclForType() const {
+  const Expr *E = this;
+
+  while (true) {
+    E = E->IgnoreParens();
+    if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
+      if (CE->getCastKind() == CK_DerivedToBase ||
+          CE->getCastKind() == CK_UncheckedDerivedToBase ||
+          CE->getCastKind() == CK_NoOp) {
+        E = CE->getSubExpr();
+        continue;
+      }
+    }
+
+    break;
+  }
+
+  QualType DerivedType = E->getType();
+  if (DerivedType->isDependentType())
+    return NULL;
+  if (const PointerType *PTy = DerivedType->getAs<PointerType>())
+    DerivedType = PTy->getPointeeType();
+
+  const RecordType *Ty = DerivedType->castAs<RecordType>();
+  if (!Ty)
+    return NULL;
+
+  Decl *D = Ty->getDecl();
+  return cast<CXXRecordDecl>(D);
+}
+
 /// isKnownToHaveBooleanValue - Return true if this is an integer expression
 /// that is known to return 0 or 1.  This happens for _Bool/bool expressions
 /// but also int expressions which are produced by things like comparisons in

clang/lib/CodeGen/CGExprCXX.cpp

@@ -56,30 +56,6 @@ RValue CodeGenFunction::EmitCXXMemberCall(const CXXMethodDecl *MD,
                   Callee, ReturnValue, Args, MD);
 }
 
-static const CXXRecordDecl *getMostDerivedClassDecl(const Expr *Base) {
-  const Expr *E = Base;
-  
-  while (true) {
-    E = E->IgnoreParens();
-    if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
-      if (CE->getCastKind() == CK_DerivedToBase || 
-          CE->getCastKind() == CK_UncheckedDerivedToBase ||
-          CE->getCastKind() == CK_NoOp) {
-        E = CE->getSubExpr();
-        continue;
-      }
-    }
-
-    break;
-  }
-
-  QualType DerivedType = E->getType();
-  if (const PointerType *PTy = DerivedType->getAs<PointerType>())
-    DerivedType = PTy->getPointeeType();
-
-  return cast<CXXRecordDecl>(DerivedType->castAs<RecordType>()->getDecl());
-}
-
 // FIXME: Ideally Expr::IgnoreParenNoopCasts should do this, but it doesn't do
 // quite what we want.
 static const Expr *skipNoOpCastsAndParens(const Expr *E) {
@@ -126,7 +102,8 @@ static bool canDevirtualizeMemberFunctionCalls(ASTContext &Context,
   //   b->f();
   // }
   //
-  const CXXRecordDecl *MostDerivedClassDecl = getMostDerivedClassDecl(Base);
+  const CXXRecordDecl *MostDerivedClassDecl =
+    Base->getMostDerivedClassDeclForType();
   if (MostDerivedClassDecl->hasAttr<FinalAttr>())
     return true;
 
@@ -247,10 +224,13 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
   //
   // We also don't emit a virtual call if the base expression has a record type
   // because then we know what the type is.
-  bool UseVirtualCall;
-  UseVirtualCall = MD->isVirtual() && !ME->hasQualifier()
-                   && !canDevirtualizeMemberFunctionCalls(getContext(),
-                                                          ME->getBase(), MD);
+  const Expr *Base = ME->getBase();
+  bool UseVirtualCall = MD->isVirtual() && !ME->hasQualifier()
+                        && !canDevirtualizeMemberFunctionCalls(getContext(),
+                                                               Base, MD);
+  const CXXRecordDecl *MostDerivedClassDecl =
+    Base->getMostDerivedClassDeclForType();
+
   llvm::Value *Callee;
   if (const CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(MD)) {
     if (UseVirtualCall) {
@@ -260,8 +240,13 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
           MD->isVirtual() &&
           ME->hasQualifier())
         Callee = BuildAppleKextVirtualCall(MD, ME->getQualifier(), Ty);
-      else
-        Callee = CGM.GetAddrOfFunction(GlobalDecl(Dtor, Dtor_Complete), Ty);
+      else {
+        const CXXMethodDecl *DM =
+          Dtor->getCorrespondingMethodInClass(MostDerivedClassDecl);
+        assert(DM);
+        const CXXDestructorDecl *DDtor = cast<CXXDestructorDecl>(DM);
+        Callee = CGM.GetAddrOfFunction(GlobalDecl(DDtor, Dtor_Complete), Ty);
+      }
     }
   } else if (const CXXConstructorDecl *Ctor =
                dyn_cast<CXXConstructorDecl>(MD)) {
@@ -273,8 +258,12 @@ RValue CodeGenFunction::EmitCXXMemberCallExpr(const CXXMemberCallExpr *CE,
         MD->isVirtual() &&
         ME->hasQualifier())
       Callee = BuildAppleKextVirtualCall(MD, ME->getQualifier(), Ty);
-    else 
-      Callee = CGM.GetAddrOfFunction(MD, Ty);
+    else {
+      const CXXMethodDecl *DerivedMethod =
+        MD->getCorrespondingMethodInClass(MostDerivedClassDecl);
+      assert(DerivedMethod);
+      Callee = CGM.GetAddrOfFunction(DerivedMethod, Ty);
+    }
   }
 
   return EmitCXXMemberCall(MD, Callee, ReturnValue, This, /*VTT=*/0,

clang/lib/Sema/SemaExpr.cpp

@@ -10844,6 +10844,22 @@ static void MarkExprReferenced(Sema &SemaRef, SourceLocation Loc,
   }
 
   SemaRef.MarkAnyDeclReferenced(Loc, D);
+
+  // If this is a call to a method via a cast, also mark the method in the
+  // derived class used in case codegen can devirtualize the call.
+  const MemberExpr *ME = dyn_cast<MemberExpr>(E);
+  if (!ME)
+    return;
+  CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(ME->getMemberDecl());
+  if (!MD)
+    return;
+  const Expr *Base = ME->getBase();
+  const CXXRecordDecl *MostDerivedClassDecl
+    = Base->getMostDerivedClassDeclForType();
+  if (!MostDerivedClassDecl)
+    return;
+  CXXMethodDecl *DM = MD->getCorrespondingMethodInClass(MostDerivedClassDecl);
+  SemaRef.MarkAnyDeclReferenced(Loc, DM);
 } 
 
 /// \brief Perform reference-marking and odr-use handling for a DeclRefExpr.

clang/test/CodeGenCXX/devirtualize-virtual-function-calls-final.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 %s -emit-llvm -o - | FileCheck %s
 
 namespace Test1 {
   struct A {
@@ -49,3 +49,61 @@ namespace Test3 {
     return static_cast<B*>(v)->f();
   }
 }
+
+namespace Test4 {
+  struct A {
+    virtual void f();
+  };
+
+  struct B final : A {
+    virtual void f();
+  };
+
+  // CHECK: define void @_ZN5Test41fEPNS_1BE
+  void f(B* d) {
+    // CHECK: call void @_ZN5Test41B1fEv
+    static_cast<A*>(d)->f();
+  }
+}
+
+namespace Test5 {
+  struct A {
+    virtual void f();
+  };
+
+  struct B : A {
+    virtual void f();
+  };
+
+  struct C final : B {
+  };
+
+  // CHECK: define void @_ZN5Test51fEPNS_1CE
+  void f(C* d) {
+    // CHECK: call void @_ZN5Test51B1fEv
+    static_cast<A*>(d)->f();
+  }
+}
+
+namespace Test6 {
+  struct A {
+    virtual ~A();
+  };
+
+  struct B : public A {
+    virtual ~B();
+  };
+
+  struct C {
+    virtual ~C();
+  };
+
+  struct D final : public C, public B {
+  };
+
+  // CHECK: define void @_ZN5Test61fEPNS_1DE
+  void f(D* d) {
+    // CHECK: call void @_ZN5Test61DD1Ev
+    static_cast<A*>(d)->~A();
+  }
+}