Teach the constant expr evaluator about derived-to-base casts when no virtual bases are involved. Fixes PR5974.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@117868 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 61f5b13..d23eac2 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -568,6 +568,42 @@
case CK_AnyPointerToBlockPointerCast:
return Visit(SubExpr);
+ case CK_DerivedToBase:
+ case CK_UncheckedDerivedToBase: {
+ LValue BaseLV;
+ if (!EvaluatePointer(E->getSubExpr(), BaseLV, Info))
+ return false;
+
+ // Now figure out the necessary offset to add to the baseLV to get from
+ // the derived class to the base class.
+ uint64_t Offset = 0;
+
+ QualType Ty = E->getSubExpr()->getType();
+ const CXXRecordDecl *DerivedDecl =
+ Ty->getAs<PointerType>()->getPointeeType()->getAsCXXRecordDecl();
+
+ for (CastExpr::path_const_iterator PathI = E->path_begin(),
+ PathE = E->path_end(); PathI != PathE; ++PathI) {
+ const CXXBaseSpecifier *Base = *PathI;
+
+ // FIXME: If the base is virtual, we'd need to determine the type of the
+ // most derived class and we don't support that right now.
+ if (Base->isVirtual())
+ return false;
+
+ const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
+ const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
+
+ Offset += Layout.getBaseClassOffset(BaseDecl);
+ DerivedDecl = BaseDecl;
+ }
+
+ Result.Base = BaseLV.getLValueBase();
+ Result.Offset = BaseLV.getLValueOffset() +
+ CharUnits::fromQuantity(Offset / Info.Ctx.getCharWidth());
+ return true;
+ }
+
case CK_IntegralToPointer: {
APValue Value;
if (!EvaluateIntegerOrLValue(SubExpr, Value, Info))