Commit af954e44 authored by Teresa Johnson's avatar Teresa Johnson
Browse files

[WPD] Emit vcall_visibility metadata for MicrosoftCXXABI 

Summary:
The MicrosoftCXXABI uses a separate mechanism for emitting vtable
type metadata, and thus didn't pick up the change from D71907
to emit the vcall_visibility metadata under -fwhole-program-vtables.

I believe this is the cause of a Windows bot failure when I committed
follow on change D71913 that required a revert. The failure occurred
in a CFI test that was expecting to not abort because it expected a
devirtualization to occur, and without the necessary vcall_visibility
metadata we would not get devirtualization.

Note in the equivalent code in CodeGenModule::EmitVTableTypeMetadata
(used by the ItaniumCXXABI), we also emit the vcall_visibility metadata
when Virtual Function Elimination is enabled. Since I am not as familiar
with the details of that optimization, I have marked that as a TODO and
am only inserting under -fwhole-program-vtables.

Reviewers: evgeny777

Subscribers: Prazek, ostannard, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73418
parent 2a160ba5

clang/lib/CodeGen/MicrosoftCXXABI.cpp

+9 −0
Original line number Diff line number Diff line
@@ -1621,6 +1621,15 @@ void MicrosoftCXXABI::emitVTableTypeMetadata(const VPtrInfo &Info, 
  if (!CGM.getCodeGenOpts().LTOUnit)

    return;



  // TODO: Should VirtualFunctionElimination also be supported here?

  // See similar handling in CodeGenModule::EmitVTableTypeMetadata.

  if (CGM.getCodeGenOpts().WholeProgramVTables) {

    llvm::GlobalObject::VCallVisibility TypeVis =

        CGM.GetVCallVisibilityLevel(RD);

    if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic)

      VTable->setVCallVisibilityMetadata(TypeVis);

  }



  // The location of the first virtual function pointer in the virtual table,

  // aka the "address point" on Itanium. This is at offset 0 if RTTI is

  // disabled, or sizeof(void*) if RTTI is enabled.

clang/test/CodeGenCXX/vcall-visibility-metadata.cpp

+13 −0
Original line number Diff line number Diff line 
// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -emit-llvm -fvirtual-function-elimination -fwhole-program-vtables -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-VFE

// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -emit-llvm -fwhole-program-vtables -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOVFE

// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-pc-windows-msvc -emit-llvm -fwhole-program-vtables -o - %s | FileCheck %s --check-prefix=CHECK-MS --check-prefix=CHECK-NOVFE



// Check that in ThinLTO we also get vcall_visibility summary entries in the bitcode

// RUN: %clang_cc1 -flto=thin -flto-unit -triple x86_64-unknown-linux -emit-llvm-bc -fwhole-program-vtables -o - %s | llvm-dis -o - | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOVFE --check-prefix=CHECK-SUMMARY
@@ -8,6 +9,7 @@ 
// Anonymous namespace.

namespace {

// CHECK: @_ZTVN12_GLOBAL__N_11AE = {{.*}} !vcall_visibility [[VIS_TU:![0-9]+]]

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.(anonymous namespace)::A{{.*}} !vcall_visibility [[VIS_TU:![0-9]+]]

struct A {

  A() {}

  virtual int f() { return 1; }
@@ -20,6 +22,7 @@ void *construct_A() { 


// Hidden visibility.

// CHECK: @_ZTV1B = {{.*}} !vcall_visibility [[VIS_DSO:![0-9]+]]

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.B{{.*}} !vcall_visibility [[VIS_DSO:![0-9]+]]

struct __attribute__((visibility("hidden"))) B {

  B() {}

  virtual int f() { return 1; }
@@ -31,6 +34,8 @@ B *construct_B() { 


// Default visibility.

// CHECK-NOT: @_ZTV1C = {{.*}} !vcall_visibility

// On MS default is hidden

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.C{{.*}} !vcall_visibility [[VIS_DSO]]

struct __attribute__((visibility("default"))) C {

  C() {}

  virtual int f() { return 1; }
@@ -42,6 +47,7 @@ C *construct_C() { 


// Hidden visibility, public LTO visibility.

// CHECK-NOT: @_ZTV1D = {{.*}} !vcall_visibility

// CHECK-MS-NOT: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.D{{.*}} !vcall_visibility

struct __attribute__((visibility("hidden"))) [[clang::lto_visibility_public]] D {

  D() {}

  virtual int f() { return 1; }
@@ -53,6 +59,8 @@ D *construct_D() { 


// Hidden visibility, but inherits from class with default visibility.

// CHECK-NOT: @_ZTV1E = {{.*}} !vcall_visibility

// On MS default is hidden

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.E{{.*}} !vcall_visibility [[VIS_DSO]]

struct __attribute__((visibility("hidden"))) E : C {

  E() {}

  virtual int f() { return 1; }
@@ -64,6 +72,8 @@ E *construct_E() { 


// Anonymous namespace, but inherits from class with default visibility.

// CHECK-NOT: @_ZTVN12_GLOBAL__N_11FE = {{.*}} !vcall_visibility

// On MS default is hidden

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.(anonymous namespace)::F{{.*}} !vcall_visibility [[VIS_DSO]]

namespace {

struct __attribute__((visibility("hidden"))) F : C {

  F() {}
@@ -77,6 +87,7 @@ void *construct_F() { 


// Anonymous namespace, but inherits from class with hidden visibility.

// CHECK: @_ZTVN12_GLOBAL__N_11GE = {{.*}} !vcall_visibility [[VIS_DSO:![0-9]+]]

// CHECK-MS: @anon.{{.*}} = private unnamed_addr constant {{.*}}struct.(anonymous namespace)::G{{.*}} !vcall_visibility [[VIS_DSO]]

namespace {

struct __attribute__((visibility("hidden"))) G : B {

  G() {}
@@ -87,6 +98,8 @@ void *construct_G() { 
  return new G();

}



// CHECK-MS-DAG: [[VIS_DSO]] = !{i64 1}

// CHECK-MS-DAG: [[VIS_TU]] = !{i64 2}

// CHECK-DAG: [[VIS_DSO]] = !{i64 1}

// CHECK-DAG: [[VIS_TU]] = !{i64 2}

// CHECK-VFE-DAG: !{i32 1, !"Virtual Function Elim", i32 1}