As a first step towards fixing PR9641, add a CK_DynamicToNull cast kind which

represents a dynamic cast where we know that the result is always null.

For example:

struct A {
  virtual ~A();
};
struct B final : A { };
struct C { };

bool f(B* b) {
  return dynamic_cast<C*>(b);
}



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129256 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 9 insertions, 3 deletions

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index a35f81ca20..ad51316a1f 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1867,7 +1867,8 @@ LValue CodeGenFunction::EmitCastLValue(const CastExpr *E) {
     return MakeAddrLValue(V, E->getType());
   }
 
-  case CK_Dynamic: {
+  case CK_Dynamic:
+  case CK_DynamicToNull: {
     LValue LV = EmitLValue(E->getSubExpr());
     llvm::Value *V = LV.getAddress();
     const CXXDynamicCastExpr *DCE = cast<CXXDynamicCastExpr>(E);
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index 75e3a7879d..5e1ac3cbac 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -255,7 +255,10 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
   }
 
   switch (E->getCastKind()) {
-  case CK_Dynamic: {
+  case CK_Dynamic:
+  case CK_DynamicToNull: {
+
+    // FIXME: Actually handle DynamicToNull here.
     assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
     LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
     // FIXME: Do we also need to handle property references here?
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index 822a999b96..578a37f0fc 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -552,6 +552,7 @@ public:
     case CK_GetObjCProperty:
     case CK_ToVoid:
     case CK_Dynamic:
+    case CK_DynamicToNull:
     case CK_ResolveUnknownAnyType:
       return 0;
 
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index 65aa46fff0..322b6e0c49 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1053,7 +1053,8 @@ Value *ScalarExprEmitter::EmitCastExpr(CastExpr *CE) {
                                      CE->path_begin(), CE->path_end(),
                                      ShouldNullCheckClassCastValue(CE));
   }
-  case CK_Dynamic: {
+  case CK_Dynamic:
+  case CK_DynamicToNull: {
     Value *V = Visit(const_cast<Expr*>(E));
     const CXXDynamicCastExpr *DCE = cast<CXXDynamicCastExpr>(CE);
     return CGF.EmitDynamicCast(V, DCE);