Index: cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp =================================================================== --- cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp +++ cfe/trunk/lib/CodeGen/ItaniumCXXABI.cpp @@ -1623,7 +1623,22 @@ llvm::Value *VFuncPtr = CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn"); - VFunc = CGF.Builder.CreateAlignedLoad(VFuncPtr, CGF.getPointerAlign()); + auto *VFuncLoad = + CGF.Builder.CreateAlignedLoad(VFuncPtr, CGF.getPointerAlign()); + + // Add !invariant.load md to virtual function load to indicate that + // function didn't change inside vtable. + // It's safe to add it without -fstrict-vtable-pointers, but it would not + // help in devirtualization because it will only matter if we will have 2 + // the same virtual function loads from the same vtable load, which won't + // happen without enabled devirtualization with -fstrict-vtable-pointers. + if (CGM.getCodeGenOpts().OptimizationLevel > 0 && + CGM.getCodeGenOpts().StrictVTablePointers) + VFuncLoad->setMetadata( + llvm::LLVMContext::MD_invariant_load, + llvm::MDNode::get(CGM.getLLVMContext(), + llvm::ArrayRef())); + VFunc = VFuncLoad; } CGCallee Callee(MethodDecl, VFunc); Index: cfe/trunk/test/CodeGenCXX/virtual-function-calls.cpp =================================================================== --- cfe/trunk/test/CodeGenCXX/virtual-function-calls.cpp +++ cfe/trunk/test/CodeGenCXX/virtual-function-calls.cpp @@ -1,4 +1,5 @@ // RUN: %clang_cc1 %s -triple %itanium_abi_triple -std=c++11 -emit-llvm -o - | FileCheck %s +// RUN: %clang_cc1 %s -triple %itanium_abi_triple -std=c++11 -emit-llvm -o - -fstrict-vtable-pointers -O1 | FileCheck --check-prefix=CHECK-INVARIANT %s // PR5021 namespace PR5021 { @@ -42,10 +43,14 @@ [[noreturn]] virtual void f(); }; - // CHECK: @_ZN15VirtualNoreturn1f + // CHECK-LABEL: @_ZN15VirtualNoreturn1f + // CHECK-INVARIANT-LABEL: define void @_ZN15VirtualNoreturn1f void f(A *p) { p->f(); // CHECK: call {{.*}}void %{{[^#]*$}} // CHECK-NOT: unreachable + // CHECK-INVARIANT: load {{.*}} !invariant.load ![[EMPTY_NODE:[0-9]+]] } } + +// CHECK-INVARIANT: ![[EMPTY_NODE]] = !{}