Emit invariant.group.barrier when using union field
Summary:
We need to emit barrier if the union field
is CXXRecordDecl because it might have vptrs. The testcode
was wrongly devirtualized. It also proves that having different
groups for different dynamic types is not sufficient.
Reviewers: rjmccall, rsmith, mehdi_amini
Subscribers: amharc, cfe-commits
Differential Revision: https://reviews.llvm.org/D31830
llvm-svn: 304448
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index b918a66..6808c69 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3530,6 +3530,25 @@
return CGF.Builder.CreateStructGEP(base, idx, offset, field->getName());
}
+static bool hasAnyVptr(const QualType Type, const ASTContext &Context) {
+ const auto *RD = Type.getTypePtr()->getAsCXXRecordDecl();
+ if (!RD)
+ return false;
+
+ if (RD->isDynamicClass())
+ return true;
+
+ for (const auto &Base : RD->bases())
+ if (hasAnyVptr(Base.getType(), Context))
+ return true;
+
+ for (const FieldDecl *Field : RD->fields())
+ if (hasAnyVptr(Field->getType(), Context))
+ return true;
+
+ return false;
+}
+
LValue CodeGenFunction::EmitLValueForField(LValue base,
const FieldDecl *field) {
LValueBaseInfo BaseInfo = base.getBaseInfo();
@@ -3572,6 +3591,14 @@
assert(!type->isReferenceType() && "union has reference member");
// TODO: handle path-aware TBAA for union.
TBAAPath = false;
+
+ const auto FieldType = field->getType();
+ if (CGM.getCodeGenOpts().StrictVTablePointers &&
+ hasAnyVptr(FieldType, getContext()))
+ // Because unions can easily skip invariant.barriers, we need to add
+ // a barrier every time CXXRecord field with vptr is referenced.
+ addr = Address(Builder.CreateInvariantGroupBarrier(addr.getPointer()),
+ addr.getAlignment());
} else {
// For structs, we GEP to the field that the record layout suggests.
addr = emitAddrOfFieldStorage(*this, addr, field);