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-rw-r--r--clang/include/clang/Basic/CodeGenOptions.def4
-rw-r--r--clang/include/clang/Driver/Options.td7
-rw-r--r--clang/lib/CodeGen/CGClass.cpp18
-rw-r--r--clang/lib/CodeGen/CGVTables.cpp35
-rw-r--r--clang/lib/CodeGen/CodeGenModule.h10
-rw-r--r--clang/lib/CodeGen/ItaniumCXXABI.cpp105
-rw-r--r--clang/lib/Driver/ToolChains/Clang.cpp27
-rw-r--r--clang/lib/Frontend/CompilerInvocation.cpp2
-rw-r--r--clang/test/CodeGenCXX/vcall-visibility-metadata.cpp88
-rw-r--r--clang/test/CodeGenCXX/virtual-function-elimination.cpp75
-rw-r--r--clang/test/Driver/virtual-function-elimination.cpp11
11 files changed, 337 insertions, 45 deletions
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 736f201a12b..d2266cc2d61 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -278,6 +278,10 @@ CODEGENOPT(EmitLLVMUseLists, 1, 0) ///< Control whether to serialize use-lists.
CODEGENOPT(WholeProgramVTables, 1, 0) ///< Whether to apply whole-program
/// vtable optimization.
+CODEGENOPT(VirtualFunctionElimination, 1, 0) ///< Whether to apply the dead
+ /// virtual function elimination
+ /// optimization.
+
/// Whether to use public LTO visibility for entities in std and stdext
/// namespaces. This is enabled by clang-cl's /MT and /MTd flags.
CODEGENOPT(LTOVisibilityPublicStd, 1, 0)
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index aaa79d2b123..3ce6fcf29f9 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1885,6 +1885,13 @@ def fforce_emit_vtables : Flag<["-"], "fforce-emit-vtables">, Group<f_Group>,
HelpText<"Emits more virtual tables to improve devirtualization">;
def fno_force_emit_vtables : Flag<["-"], "fno-force-emit-vtables">, Group<f_Group>,
Flags<[CoreOption]>;
+
+def fvirtual_function_elimination : Flag<["-"], "fvirtual-function-elimination">, Group<f_Group>,
+ Flags<[CoreOption, CC1Option]>,
+ HelpText<"Enables dead virtual function elimination optimization. Requires -flto=full">;
+def fno_virtual_function_elimination : Flag<["-"], "fno-virtual-function_elimination">, Group<f_Group>,
+ Flags<[CoreOption]>;
+
def fwrapv : Flag<["-"], "fwrapv">, Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Treat signed integer overflow as two's complement">;
def fwritable_strings : Flag<["-"], "fwritable-strings">, Group<f_Group>, Flags<[CC1Option]>,
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index ab8588303d2..7cff6210c29 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -2784,11 +2784,16 @@ void CodeGenFunction::EmitVTablePtrCheck(const CXXRecordDecl *RD,
bool CodeGenFunction::ShouldEmitVTableTypeCheckedLoad(const CXXRecordDecl *RD) {
if (!CGM.getCodeGenOpts().WholeProgramVTables ||
- !SanOpts.has(SanitizerKind::CFIVCall) ||
- !CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIVCall) ||
!CGM.HasHiddenLTOVisibility(RD))
return false;
+ if (CGM.getCodeGenOpts().VirtualFunctionElimination)
+ return true;
+
+ if (!SanOpts.has(SanitizerKind::CFIVCall) ||
+ !CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIVCall))
+ return false;
+
std::string TypeName = RD->getQualifiedNameAsString();
return !getContext().getSanitizerBlacklist().isBlacklistedType(
SanitizerKind::CFIVCall, TypeName);
@@ -2811,8 +2816,13 @@ llvm::Value *CodeGenFunction::EmitVTableTypeCheckedLoad(
TypeId});
llvm::Value *CheckResult = Builder.CreateExtractValue(CheckedLoad, 1);
- EmitCheck(std::make_pair(CheckResult, SanitizerKind::CFIVCall),
- SanitizerHandler::CFICheckFail, nullptr, nullptr);
+ std::string TypeName = RD->getQualifiedNameAsString();
+ if (SanOpts.has(SanitizerKind::CFIVCall) &&
+ !getContext().getSanitizerBlacklist().isBlacklistedType(
+ SanitizerKind::CFIVCall, TypeName)) {
+ EmitCheck(std::make_pair(CheckResult, SanitizerKind::CFIVCall),
+ SanitizerHandler::CFICheckFail, {}, {});
+ }
return Builder.CreateBitCast(
Builder.CreateExtractValue(CheckedLoad, 0),
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index a74905fd70f..f9f25e7e57a 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -808,7 +808,7 @@ CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
assert(!VTable->isDeclaration() && "Shouldn't set properties on declaration");
CGM.setGVProperties(VTable, RD);
- CGM.EmitVTableTypeMetadata(VTable, *VTLayout.get());
+ CGM.EmitVTableTypeMetadata(RD, VTable, *VTLayout.get());
return VTable;
}
@@ -1039,7 +1039,32 @@ bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) {
return true;
}
-void CodeGenModule::EmitVTableTypeMetadata(llvm::GlobalVariable *VTable,
+llvm::GlobalObject::VCallVisibility
+CodeGenModule::GetVCallVisibilityLevel(const CXXRecordDecl *RD) {
+ LinkageInfo LV = RD->getLinkageAndVisibility();
+ llvm::GlobalObject::VCallVisibility TypeVis;
+ if (!isExternallyVisible(LV.getLinkage()))
+ TypeVis = llvm::GlobalObject::VCallVisibilityTranslationUnit;
+ else if (HasHiddenLTOVisibility(RD))
+ TypeVis = llvm::GlobalObject::VCallVisibilityLinkageUnit;
+ else
+ TypeVis = llvm::GlobalObject::VCallVisibilityPublic;
+
+ for (auto B : RD->bases())
+ if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
+ TypeVis = std::min(TypeVis,
+ GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl()));
+
+ for (auto B : RD->vbases())
+ if (B.getType()->getAsCXXRecordDecl()->isDynamicClass())
+ TypeVis = std::min(TypeVis,
+ GetVCallVisibilityLevel(B.getType()->getAsCXXRecordDecl()));
+
+ return TypeVis;
+}
+
+void CodeGenModule::EmitVTableTypeMetadata(const CXXRecordDecl *RD,
+ llvm::GlobalVariable *VTable,
const VTableLayout &VTLayout) {
if (!getCodeGenOpts().LTOUnit)
return;
@@ -1099,4 +1124,10 @@ void CodeGenModule::EmitVTableTypeMetadata(llvm::GlobalVariable *VTable,
VTable->addTypeMetadata((PointerWidth * I).getQuantity(), MD);
}
}
+
+ if (getCodeGenOpts().VirtualFunctionElimination) {
+ llvm::GlobalObject::VCallVisibility TypeVis = GetVCallVisibilityLevel(RD);
+ if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic)
+ VTable->addVCallVisibilityMetadata(TypeVis);
+ }
}
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 597b8d712ca..73f81adae35 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1280,8 +1280,16 @@ public:
/// optimization.
bool HasHiddenLTOVisibility(const CXXRecordDecl *RD);
+ /// Returns the vcall visibility of the given type. This is the scope in which
+ /// a virtual function call could be made which ends up being dispatched to a
+ /// member function of this class. This scope can be wider than the visibility
+ /// of the class itself when the class has a more-visible dynamic base class.
+ llvm::GlobalObject::VCallVisibility
+ GetVCallVisibilityLevel(const CXXRecordDecl *RD);
+
/// Emit type metadata for the given vtable using the given layout.
- void EmitVTableTypeMetadata(llvm::GlobalVariable *VTable,
+ void EmitVTableTypeMetadata(const CXXRecordDecl *RD,
+ llvm::GlobalVariable *VTable,
const VTableLayout &VTLayout);
/// Generate a cross-DSO type identifier for MD.
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index 2945dec0bd7..8f9b16470b6 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -644,8 +644,6 @@ CGCallee ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(
VTableOffset = Builder.CreateTrunc(VTableOffset, CGF.Int32Ty);
VTableOffset = Builder.CreateZExt(VTableOffset, CGM.PtrDiffTy);
}
- // Compute the address of the virtual function pointer.
- llvm::Value *VFPAddr = Builder.CreateGEP(VTable, VTableOffset);
// Check the address of the function pointer if CFI on member function
// pointers is enabled.
@@ -653,44 +651,81 @@ CGCallee ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(
llvm::Constant *CheckTypeDesc;
bool ShouldEmitCFICheck = CGF.SanOpts.has(SanitizerKind::CFIMFCall) &&
CGM.HasHiddenLTOVisibility(RD);
- if (ShouldEmitCFICheck) {
- CodeGenFunction::SanitizerScope SanScope(&CGF);
-
- CheckSourceLocation = CGF.EmitCheckSourceLocation(E->getBeginLoc());
- CheckTypeDesc = CGF.EmitCheckTypeDescriptor(QualType(MPT, 0));
- llvm::Constant *StaticData[] = {
- llvm::ConstantInt::get(CGF.Int8Ty, CodeGenFunction::CFITCK_VMFCall),
- CheckSourceLocation,
- CheckTypeDesc,
- };
-
- llvm::Metadata *MD =
- CGM.CreateMetadataIdentifierForVirtualMemPtrType(QualType(MPT, 0));
- llvm::Value *TypeId = llvm::MetadataAsValue::get(CGF.getLLVMContext(), MD);
+ bool ShouldEmitVFEInfo = CGM.getCodeGenOpts().VirtualFunctionElimination &&
+ CGM.HasHiddenLTOVisibility(RD);
+ llvm::Value *VirtualFn = nullptr;
- llvm::Value *TypeTest = Builder.CreateCall(
- CGM.getIntrinsic(llvm::Intrinsic::type_test), {VFPAddr, TypeId});
+ {
+ CodeGenFunction::SanitizerScope SanScope(&CGF);
+ llvm::Value *TypeId = nullptr;
+ llvm::Value *CheckResult = nullptr;
+
+ if (ShouldEmitCFICheck || ShouldEmitVFEInfo) {
+ // If doing CFI or VFE, we will need the metadata node to check against.
+ llvm::Metadata *MD =
+ CGM.CreateMetadataIdentifierForVirtualMemPtrType(QualType(MPT, 0));
+ TypeId = llvm::MetadataAsValue::get(CGF.getLLVMContext(), MD);
+ }
- if (CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIMFCall)) {
- CGF.EmitTrapCheck(TypeTest);
+ llvm::Value *VFPAddr = Builder.CreateGEP(VTable, VTableOffset);
+
+ if (ShouldEmitVFEInfo) {
+ // If doing VFE, load from the vtable with a type.checked.load intrinsic
+ // call. Note that we use the GEP to calculate the address to load from
+ // and pass 0 as the offset to the intrinsic. This is because every
+ // vtable slot of the correct type is marked with matching metadata, and
+ // we know that the load must be from one of these slots.
+ llvm::Value *CheckedLoad = Builder.CreateCall(
+ CGM.getIntrinsic(llvm::Intrinsic::type_checked_load),
+ {VFPAddr, llvm::ConstantInt::get(CGM.Int32Ty, 0), TypeId});
+ CheckResult = Builder.CreateExtractValue(CheckedLoad, 1);
+ VirtualFn = Builder.CreateExtractValue(CheckedLoad, 0);
+ VirtualFn = Builder.CreateBitCast(VirtualFn, FTy->getPointerTo(),
+ "memptr.virtualfn");
} else {
- llvm::Value *AllVtables = llvm::MetadataAsValue::get(
- CGM.getLLVMContext(),
- llvm::MDString::get(CGM.getLLVMContext(), "all-vtables"));
- llvm::Value *ValidVtable = Builder.CreateCall(
- CGM.getIntrinsic(llvm::Intrinsic::type_test), {VTable, AllVtables});
- CGF.EmitCheck(std::make_pair(TypeTest, SanitizerKind::CFIMFCall),
- SanitizerHandler::CFICheckFail, StaticData,
- {VTable, ValidVtable});
+ // When not doing VFE, emit a normal load, as it allows more
+ // optimisations than type.checked.load.
+ if (ShouldEmitCFICheck) {
+ CheckResult = Builder.CreateCall(
+ CGM.getIntrinsic(llvm::Intrinsic::type_test),
+ {Builder.CreateBitCast(VFPAddr, CGF.Int8PtrTy), TypeId});
+ }
+ VFPAddr =
+ Builder.CreateBitCast(VFPAddr, FTy->getPointerTo()->getPointerTo());
+ VirtualFn = Builder.CreateAlignedLoad(VFPAddr, CGF.getPointerAlign(),
+ "memptr.virtualfn");
}
+ assert(VirtualFn && "Virtual fuction pointer not created!");
+ assert((!ShouldEmitCFICheck || !ShouldEmitVFEInfo || CheckResult) &&
+ "Check result required but not created!");
+
+ if (ShouldEmitCFICheck) {
+ // If doing CFI, emit the check.
+ CheckSourceLocation = CGF.EmitCheckSourceLocation(E->getBeginLoc());
+ CheckTypeDesc = CGF.EmitCheckTypeDescriptor(QualType(MPT, 0));
+ llvm::Constant *StaticData[] = {
+ llvm::ConstantInt::get(CGF.Int8Ty, CodeGenFunction::CFITCK_VMFCall),
+ CheckSourceLocation,
+ CheckTypeDesc,
+ };
- FnVirtual = Builder.GetInsertBlock();
- }
+ if (CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIMFCall)) {
+ CGF.EmitTrapCheck(CheckResult);
+ } else {
+ llvm::Value *AllVtables = llvm::MetadataAsValue::get(
+ CGM.getLLVMContext(),
+ llvm::MDString::get(CGM.getLLVMContext(), "all-vtables"));
+ llvm::Value *ValidVtable = Builder.CreateCall(
+ CGM.getIntrinsic(llvm::Intrinsic::type_test), {VTable, AllVtables});
+ CGF.EmitCheck(std::make_pair(CheckResult, SanitizerKind::CFIMFCall),
+ SanitizerHandler::CFICheckFail, StaticData,
+ {VTable, ValidVtable});
+ }
+
+ FnVirtual = Builder.GetInsertBlock();
+ }
+ } // End of sanitizer scope
- // Load the virtual function to call.
- VFPAddr = Builder.CreateBitCast(VFPAddr, FTy->getPointerTo()->getPointerTo());
- llvm::Value *VirtualFn = Builder.CreateAlignedLoad(
- VFPAddr, CGF.getPointerAlign(), "memptr.virtualfn");
CGF.EmitBranch(FnEnd);
// In the non-virtual path, the function pointer is actually a
@@ -1634,7 +1669,7 @@ void ItaniumCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
EmitFundamentalRTTIDescriptors(RD);
if (!VTable->isDeclarationForLinker())
- CGM.EmitVTableTypeMetadata(VTable, VTLayout);
+ CGM.EmitVTableTypeMetadata(RD, VTable, VTLayout);
}
bool ItaniumCXXABI::isVirtualOffsetNeededForVTableField(
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index b418ccb0f01..bfccf7a1dbb 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5369,9 +5369,30 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back(Args.MakeArgString(TargetInfo.str()));
}
- bool WholeProgramVTables =
- Args.hasFlag(options::OPT_fwhole_program_vtables,
- options::OPT_fno_whole_program_vtables, false);
+ bool VirtualFunctionElimination =
+ Args.hasFlag(options::OPT_fvirtual_function_elimination,
+ options::OPT_fno_virtual_function_elimination, false);
+ if (VirtualFunctionElimination) {
+ // VFE requires full LTO (currently, this might be relaxed to allow ThinLTO
+ // in the future).
+ if (D.getLTOMode() != LTOK_Full)
+ D.Diag(diag::err_drv_argument_only_allowed_with)
+ << "-fvirtual-function-elimination"
+ << "-flto=full";
+
+ CmdArgs.push_back("-fvirtual-function-elimination");
+ }
+
+ // VFE requires whole-program-vtables, and enables it by default.
+ bool WholeProgramVTables = Args.hasFlag(
+ options::OPT_fwhole_program_vtables,
+ options::OPT_fno_whole_program_vtables, VirtualFunctionElimination);
+ if (VirtualFunctionElimination && !WholeProgramVTables) {
+ D.Diag(diag::err_drv_argument_not_allowed_with)
+ << "-fno-whole-program-vtables"
+ << "-fvirtual-function-elimination";
+ }
+
if (WholeProgramVTables) {
if (!D.isUsingLTO())
D.Diag(diag::err_drv_argument_only_allowed_with)
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index a434002b5b4..0aa44252c6c 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -758,6 +758,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
Opts.CodeViewGHash = Args.hasArg(OPT_gcodeview_ghash);
Opts.MacroDebugInfo = Args.hasArg(OPT_debug_info_macro);
Opts.WholeProgramVTables = Args.hasArg(OPT_fwhole_program_vtables);
+ Opts.VirtualFunctionElimination =
+ Args.hasArg(OPT_fvirtual_function_elimination);
Opts.LTOVisibilityPublicStd = Args.hasArg(OPT_flto_visibility_public_std);
Opts.SplitDwarfFile = Args.getLastArgValue(OPT_split_dwarf_file);
Opts.SplitDwarfOutput = Args.getLastArgValue(OPT_split_dwarf_output);
diff --git a/clang/test/CodeGenCXX/vcall-visibility-metadata.cpp b/clang/test/CodeGenCXX/vcall-visibility-metadata.cpp
new file mode 100644
index 00000000000..7cf48395673
--- /dev/null
+++ b/clang/test/CodeGenCXX/vcall-visibility-metadata.cpp
@@ -0,0 +1,88 @@
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -emit-llvm -fvirtual-function-elimination -fwhole-program-vtables -o - %s | FileCheck %s
+
+
+// Anonymous namespace.
+namespace {
+// CHECK: @_ZTVN12_GLOBAL__N_11AE = {{.*}} !vcall_visibility [[VIS_TU:![0-9]+]]
+struct A {
+ A() {}
+ virtual int f() { return 1; }
+};
+}
+void *construct_A() {
+ return new A();
+}
+
+
+// Hidden visibility.
+// CHECK: @_ZTV1B = {{.*}} !vcall_visibility [[VIS_DSO:![0-9]+]]
+struct __attribute__((visibility("hidden"))) B {
+ B() {}
+ virtual int f() { return 1; }
+};
+B *construct_B() {
+ return new B();
+}
+
+
+// Default visibility.
+// CHECK-NOT: @_ZTV1C = {{.*}} !vcall_visibility
+struct __attribute__((visibility("default"))) C {
+ C() {}
+ virtual int f() { return 1; }
+};
+C *construct_C() {
+ return new C();
+}
+
+
+// Hidden visibility, public LTO visibility.
+// CHECK-NOT: @_ZTV1D = {{.*}} !vcall_visibility
+struct __attribute__((visibility("hidden"))) [[clang::lto_visibility_public]] D {
+ D() {}
+ virtual int f() { return 1; }
+};
+D *construct_D() {
+ return new D();
+}
+
+
+// Hidden visibility, but inherits from class with default visibility.
+// CHECK-NOT: @_ZTV1E = {{.*}} !vcall_visibility
+struct __attribute__((visibility("hidden"))) E : C {
+ E() {}
+ virtual int f() { return 1; }
+};
+E *construct_E() {
+ return new E();
+}
+
+
+// Anonymous namespace, but inherits from class with default visibility.
+// CHECK-NOT: @_ZTVN12_GLOBAL__N_11FE = {{.*}} !vcall_visibility
+namespace {
+struct __attribute__((visibility("hidden"))) F : C {
+ F() {}
+ virtual int f() { return 1; }
+};
+}
+void *construct_F() {
+ return new F();
+}
+
+
+// Anonymous namespace, but inherits from class with hidden visibility.
+// CHECK: @_ZTVN12_GLOBAL__N_11GE = {{.*}} !vcall_visibility [[VIS_DSO:![0-9]+]]
+namespace {
+struct __attribute__((visibility("hidden"))) G : B {
+ G() {}
+ virtual int f() { return 1; }
+};
+}
+void *construct_G() {
+ return new G();
+}
+
+
+// CHECK-DAG: [[VIS_DSO]] = !{i64 1}
+// CHECK-DAG: [[VIS_TU]] = !{i64 2}
diff --git a/clang/test/CodeGenCXX/virtual-function-elimination.cpp b/clang/test/CodeGenCXX/virtual-function-elimination.cpp
new file mode 100644
index 00000000000..a89e6ebceea
--- /dev/null
+++ b/clang/test/CodeGenCXX/virtual-function-elimination.cpp
@@ -0,0 +1,75 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -flto -flto-unit -fvirtual-function-elimination -fwhole-program-vtables -emit-llvm -o - %s | FileCheck %s
+
+
+struct __attribute__((visibility("default"))) A {
+ virtual void foo();
+};
+
+void test_1(A *p) {
+ // A has default visibility, so no need for type.checked.load.
+// CHECK-LABEL: define void @_Z6test_1P1A
+// CHECK: [[FN_PTR_ADDR:%.+]] = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** {{%.+}}, i64 0
+// CHECK: [[FN_PTR:%.+]] = load void (%struct.A*)*, void (%struct.A*)** [[FN_PTR_ADDR]]
+// CHECK: call void [[FN_PTR]](
+ p->foo();
+}
+
+
+struct __attribute__((visibility("hidden"))) [[clang::lto_visibility_public]] B {
+ virtual void foo();
+};
+
+void test_2(B *p) {
+ // B has public LTO visibility, so no need for type.checked.load.
+// CHECK-LABEL: define void @_Z6test_2P1B
+// CHECK: [[FN_PTR_ADDR:%.+]] = getelementptr inbounds void (%struct.B*)*, void (%struct.B*)** {{%.+}}, i64 0
+// CHECK: [[FN_PTR:%.+]] = load void (%struct.B*)*, void (%struct.B*)** [[FN_PTR_ADDR]]
+// CHECK: call void [[FN_PTR]](
+ p->foo();
+}
+
+
+struct __attribute__((visibility("hidden"))) C {
+ virtual void foo();
+ virtual void bar();
+};
+
+void test_3(C *p) {
+ // C has hidden visibility, so we generate type.checked.load to allow VFE.
+// CHECK-LABEL: define void @_Z6test_3P1C
+// CHECK: [[LOAD:%.+]] = call { i8*, i1 } @llvm.type.checked.load(i8* {{%.+}}, i32 0, metadata !"_ZTS1C")
+// CHECK: [[FN_PTR_I8:%.+]] = extractvalue { i8*, i1 } [[LOAD]], 0
+// CHECK: [[FN_PTR:%.+]] = bitcast i8* [[FN_PTR_I8]] to void (%struct.C*)*
+// CHECK: call void [[FN_PTR]](
+ p->foo();
+}
+
+void test_4(C *p) {
+ // When using type.checked.load, we pass the vtable offset to the intrinsic,
+ // rather than adding it to the pointer with a GEP.
+// CHECK-LABEL: define void @_Z6test_4P1C
+// CHECK: [[LOAD:%.+]] = call { i8*, i1 } @llvm.type.checked.load(i8* {{%.+}}, i32 8, metadata !"_ZTS1C")
+// CHECK: [[FN_PTR_I8:%.+]] = extractvalue { i8*, i1 } [[LOAD]], 0
+// CHECK: [[FN_PTR:%.+]] = bitcast i8* [[FN_PTR_I8]] to void (%struct.C*)*
+// CHECK: call void [[FN_PTR]](
+ p->bar();
+}
+
+void test_5(C *p, void (C::*q)(void)) {
+ // We also use type.checked.load for the virtual side of member function
+ // pointer calls. We use a GEP to calculate the address to load from and pass
+ // 0 as the offset to the intrinsic, because we know that the load must be
+ // from exactly the point marked by one of the function-type metadatas (in
+ // this case "_ZTSM1CFvvE.virtual"). If we passed the offset from the member
+ // function pointer to the intrinsic, this information would be lost. No
+ // codegen changes on the non-virtual side.
+// CHECK-LABEL: define void @_Z6test_5P1CMS_FvvE(
+// CHECK: [[FN_PTR_ADDR:%.+]] = getelementptr i8, i8* %vtable, i64 {{%.+}}
+// CHECK: [[LOAD:%.+]] = call { i8*, i1 } @llvm.type.checked.load(i8* [[FN_PTR_ADDR]], i32 0, metadata !"_ZTSM1CFvvE.virtual")
+// CHECK: [[FN_PTR_I8:%.+]] = extractvalue { i8*, i1 } [[LOAD]], 0
+// CHECK: [[FN_PTR:%.+]] = bitcast i8* [[FN_PTR_I8]] to void (%struct.C*)*
+
+// CHECK: [[PHI:%.+]] = phi void (%struct.C*)* {{.*}}[ [[FN_PTR]], {{.*}} ]
+// CHECK: call void [[PHI]](
+ (p->*q)();
+}
diff --git a/clang/test/Driver/virtual-function-elimination.cpp b/clang/test/Driver/virtual-function-elimination.cpp
new file mode 100644
index 00000000000..3a026bbb434
--- /dev/null
+++ b/clang/test/Driver/virtual-function-elimination.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -### %s 2>&1 | FileCheck --check-prefix=BAD-LTO %s
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto=thin -### %s 2>&1 | FileCheck --check-prefix=BAD-LTO %s
+// BAD-LTO: invalid argument '-fvirtual-function-elimination' only allowed with '-flto=full'
+
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto -### %s 2>&1 | FileCheck --check-prefix=GOOD %s
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto=full -### %s 2>&1 | FileCheck --check-prefix=GOOD %s
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -flto -fwhole-program-vtables -### %s 2>&1 | FileCheck --check-prefix=GOOD %s
+// GOOD: "-fvirtual-function-elimination" "-fwhole-program-vtables"
+
+// RUN: %clang -target x86_64-unknown-linux -fvirtual-function-elimination -fno-whole-program-vtables -flto -### %s 2>&1 | FileCheck --check-prefix=NO-WHOLE-PROGRAM-VTABLES %s
+// NO-WHOLE-PROGRAM-VTABLES: invalid argument '-fno-whole-program-vtables' not allowed with '-fvirtual-function-elimination'
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