Index: lib/CodeGen/CGExpr.cpp =================================================================== --- lib/CodeGen/CGExpr.cpp +++ lib/CodeGen/CGExpr.cpp @@ -3513,6 +3513,22 @@ return CGF.Builder.CreateStructGEP(base, idx, offset, field->getName()); } +static bool hasAnyVptr(const CXXRecordDecl *RD, const ASTContext &Context) { + if (RD->isDynamicClass()) + return true; + + for (const FieldDecl *Field : RD->fields()) { + QualType FieldType = Context.getBaseElementType(Field->getType()); + const RecordType* RT = FieldType->getAs(); + if (!RT) + continue; + auto *FieldClassDecl = cast(RT->getDecl()); + if (hasAnyVptr(FieldClassDecl, Context)) + return true; + } + return false; +} + LValue CodeGenFunction::EmitLValueForField(LValue base, const FieldDecl *field) { AlignmentSource fieldAlignSource = @@ -3552,6 +3568,15 @@ assert(!type->isReferenceType() && "union has reference member"); // TODO: handle path-aware TBAA for union. TBAAPath = false; + + const auto *RD = field->getType().getTypePtr()->getAsCXXRecordDecl(); + if (CGM.getCodeGenOpts().StrictVTablePointers && + CGM.getCodeGenOpts().OptimizationLevel > 0 && + RD && hasAnyVptr(RD, 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); Index: test/CodeGenCXX/strict-vtable-pointers.cpp =================================================================== --- test/CodeGenCXX/strict-vtable-pointers.cpp +++ test/CodeGenCXX/strict-vtable-pointers.cpp @@ -1,4 +1,4 @@ -// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -fstrict-vtable-pointers -disable-llvm-passes -O2 -emit-llvm -o %t.ll +// RUN: %clang_cc1 %s -I%S -triple=x86_64-apple-darwin10 -fstrict-vtable-pointers -std=c++11 -disable-llvm-passes -O2 -emit-llvm -o %t.ll // RUN: FileCheck --check-prefix=CHECK-CTORS %s < %t.ll // RUN: FileCheck --check-prefix=CHECK-NEW %s < %t.ll // RUN: FileCheck --check-prefix=CHECK-DTORS %s < %t.ll @@ -180,6 +180,80 @@ // CHECK-CTORS-NOT: @llvm.invariant.group.barrier( // CHECK-CTORS-LABEL: {{^}}} +struct A { + virtual void foo(); +}; +struct B : A { + virtual void foo(); +}; + +union U { + A a; + B b; +}; + +void changeToB(U *u); +void changeToA(U *u); + +void g2(A *a) { + a->foo(); +} +// We have to guard access to union fields with invariant.group, because +// it is very easy to skip the barrier with unions. In this example the inlined +// g2 will produce loads with the same !invariant.group metadata, and +// u->a and u->b would use the same pointer. +// CHECK-NEW-LABEL: define void @_Z14UnionsBarriersP1U +void UnionsBarriers(U *u) { + // CHECK-NEW: call void @_Z9changeToBP1U( + changeToB(u); + // CHECK-NEW: call i8* @llvm.invariant.group.barrier(i8* + // CHECK-NEW: call void @_Z2g2P1A(%struct.A* + g2(&u->b); + // CHECK-NEW: call void @_Z9changeToAP1U(%union.U* %6) + changeToA(u); + // CHECK-NEW: call i8* @llvm.invariant.group.barrier(i8* + // call void @_Z2g2P1A(%struct.A* %a) + g2(&u->a); + // CHECK-NEW-NOT: call i8* @llvm.invariant.group.barrier(i8* +} + +struct HoldingVirtuals { + A a; +}; + +struct Empty {}; +struct AnotherEmpty { Empty e; }; +union NoVptrs { + int a; + AnotherEmpty empty; +}; +void take(AnotherEmpty &); + +// CHECK-NEW-LABEL: noBarriers +void noBarriers(NoVptrs &noVptrs) { + // CHECK-NEW-NOT: call i8* @llvm.invariant.group.barrier(i8* + // CHECK-NEW: 42 + noVptrs.a += 42; + // CHECK-NEW-NOT: call i8* @llvm.invariant.group.barrier(i8* + // CHECK-NEW: call void @_Z4takeR12AnotherEmpty( + take(noVptrs.empty); +} + +union U2 { + HoldingVirtuals h; + int z; +}; +void take(HoldingVirtuals &); + +// CHECK-NEW-LABEL: define void @_Z15UnionsBarriers2R2U2 +void UnionsBarriers2(U2 &u) { + // CHECK-NEW-NOT: call i8* @llvm.invariant.group.barrier(i8* + // CHECK-NEW: 42 + u.z += 42; + // CHECK-NEW: call i8* @llvm.invariant.group.barrier(i8* + // CHECK-NEW: call void @_Z4takeR15HoldingVirtuals( + take(u.h); +} /** DTORS **/ // CHECK-DTORS-LABEL: define linkonce_odr void @_ZN10StaticBaseD2Ev(