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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159212 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 118 insertions, 33 deletions

diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 3d76e68ff7..a8aabb68d7 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/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,
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 3de4b5771a..22d15be6a8 100644
--- a/lib/AST/Expr.cpp
+++ b/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
diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index f1d0395714..f35287d540 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/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,
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 07f3c1d6c7..4dd6f0b552 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/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.