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)
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]>,
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);
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),
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;
}
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;
VTable->addTypeMetadata((PointerWidth * I).getQuantity(), MD);
}
}
+
+ if (getCodeGenOpts().VirtualFunctionElimination) {
+ llvm::GlobalObject::VCallVisibility TypeVis = GetVCallVisibilityLevel(RD);
+ if (TypeVis != llvm::GlobalObject::VCallVisibilityPublic)
+ VTable->addVCallVisibilityMetadata(TypeVis);
+ }
}
/// 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.
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.
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
EmitFundamentalRTTIDescriptors(RD);
if (!VTable->isDeclarationForLinker())
- CGM.EmitVTableTypeMetadata(VTable, VTLayout);
+ CGM.EmitVTableTypeMetadata(RD, VTable, VTLayout);
}
bool ItaniumCXXABI::isVirtualOffsetNeededForVTableField(
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)
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);
--- /dev/null
+// 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}
--- /dev/null
+// 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)();
+}
--- /dev/null
+// 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'
!0 = !{i32 1, !"short_wchar", i32 1}
!1 = !{i32 1, !"short_enum", i32 0}
+LTO Post-Link Module Flags Metadata
+-----------------------------------
+
+Some optimisations are only when the entire LTO unit is present in the current
+module. This is represented by the ``LTOPostLink`` module flags metadata, which
+will be created with a value of ``1`` when LTO linking occurs.
+
Automatic Linker Flags Named Metadata
=====================================
The ``llvm.type.test`` intrinsic tests whether the given pointer is associated
with the given type identifier.
+.. _type.checked.load:
+
'``llvm.type.checked.load``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
}
.. _GlobalLayoutBuilder: https://github.com/llvm/llvm-project/blob/master/llvm/include/llvm/Transforms/IPO/LowerTypeTests.h
+
+``!vcall_visibility`` Metadata
+==============================
+
+In order to allow removing unused function pointers from vtables, we need to
+know whether every virtual call which could use it is known to the compiler, or
+whether another translation unit could introduce more calls through the vtable.
+This is not the same as the linkage of the vtable, because call sites could be
+using a pointer of a more widely-visible base class. For example, consider this
+code:
+
+.. code-block:: c++
+
+ __attribute__((visibility("default")))
+ struct A {
+ virtual void f();
+ };
+
+ __attribute__((visibility("hidden")))
+ struct B : A {
+ virtual void f();
+ };
+
+With LTO, we know that all code which can see the declaration of ``B`` is
+visible to us. However, a pointer to a ``B`` could be cast to ``A*`` and passed
+to another linkage unit, which could then call ``f`` on it. This call would
+load from the vtable for ``B`` (using the object pointer), and then call
+``B::f``. This means we can't remove the function pointer from ``B``'s vtable,
+or the implementation of ``B::f``. However, if we can see all code which knows
+about any dynamic base class (which would be the case if ``B`` only inherited
+from classes with hidden visibility), then this optimisation would be valid.
+
+This concept is represented in IR by the ``!vcall_visibility`` metadata
+attached to vtable objects, with the following values:
+
+.. list-table::
+ :header-rows: 1
+ :widths: 10 90
+
+ * - Value
+ - Behavior
+
+ * - 0 (or omitted)
+ - **Public**
+ Virtual function calls using this vtable could be made from external
+ code.
+
+ * - 1
+ - **Linkage Unit**
+ All virtual function calls which might use this vtable are in the
+ current LTO unit, meaning they will be in the current module once
+ LTO linking has been performed.
+
+ * - 2
+ - **Translation Unit**
+ All virtual function calls which might use this vtable are in the
+ current module.
+
+In addition, all function pointer loads from a vtable marked with the
+``!vcall_visibility`` metadata (with a non-zero value) must be done using the
+:ref:`llvm.type.checked.load <type.checked.load>` intrinsic, so that virtual
+calls sites can be correlated with the vtables which they might load from.
+Other parts of the vtable (RTTI, offset-to-top, ...) can still be accessed with
+normal loads.
SmallVectorImpl<Instruction *> &LoadedPtrs,
SmallVectorImpl<Instruction *> &Preds, bool &HasNonCallUses,
const CallInst *CI, DominatorTree &DT);
+
+Constant *getPointerAtOffset(Constant *I, uint64_t Offset, Module &M);
}
#endif
LLVM_FIXED_MD_KIND(MD_callback, "callback", 26)
LLVM_FIXED_MD_KIND(MD_preserve_access_index, "llvm.preserve.access.index", 27)
LLVM_FIXED_MD_KIND(MD_misexpect, "misexpect", 28)
+LLVM_FIXED_MD_KIND(MD_vcall_visibility, "vcall_visibility", 29)
class Metadata;
class GlobalObject : public GlobalValue {
+public:
+ // VCallVisibility - values for visibility metadata attached to vtables. This
+ // describes the scope in which a virtual call could end up being dispatched
+ // through this vtable.
+ enum VCallVisibility {
+ // Type is potentially visible to external code.
+ VCallVisibilityPublic = 0,
+ // Type is only visible to code which will be in the current Module after
+ // LTO internalization.
+ VCallVisibilityLinkageUnit = 1,
+ // Type is only visible to code in the current Module.
+ VCallVisibilityTranslationUnit = 2,
+ };
+
protected:
GlobalObject(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
LinkageTypes Linkage, const Twine &Name,
void copyMetadata(const GlobalObject *Src, unsigned Offset);
void addTypeMetadata(unsigned Offset, Metadata *TypeID);
+ void addVCallVisibilityMetadata(VCallVisibility Visibility);
+ VCallVisibility getVCallVisibility() const;
protected:
void copyAttributesFrom(const GlobalObject *Src);
/// Comdat -> Globals in that Comdat section.
std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
+ /// !type metadata -> set of (vtable, offset) pairs
+ DenseMap<Metadata *, SmallSet<std::pair<GlobalVariable *, uint64_t>, 4>>
+ TypeIdMap;
+
+ // Global variables which are vtables, and which we have enough information
+ // about to safely do dead virtual function elimination.
+ SmallPtrSet<GlobalValue *, 32> VFESafeVTables;
+
void UpdateGVDependencies(GlobalValue &GV);
void MarkLive(GlobalValue &GV,
SmallVectorImpl<GlobalValue *> *Updates = nullptr);
bool RemoveUnusedGlobalValue(GlobalValue &GV);
+ // Dead virtual function elimination.
+ void AddVirtualFunctionDependencies(Module &M);
+ void ScanVTables(Module &M);
+ void ScanTypeCheckedLoadIntrinsics(Module &M);
+ void ScanVTableLoad(Function *Caller, Metadata *TypeId, uint64_t CallOffset);
+
void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);
};
findCallsAtConstantOffset(DevirtCalls, &HasNonCallUses, LoadedPtr,
Offset->getZExtValue(), CI, DT);
}
+
+Constant *llvm::getPointerAtOffset(Constant *I, uint64_t Offset, Module &M) {
+ if (I->getType()->isPointerTy()) {
+ if (Offset == 0)
+ return I;
+ return nullptr;
+ }
+
+ const DataLayout &DL = M.getDataLayout();
+
+ if (auto *C = dyn_cast<ConstantStruct>(I)) {
+ const StructLayout *SL = DL.getStructLayout(C->getType());
+ if (Offset >= SL->getSizeInBytes())
+ return nullptr;
+
+ unsigned Op = SL->getElementContainingOffset(Offset);
+ return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
+ Offset - SL->getElementOffset(Op), M);
+ }
+ if (auto *C = dyn_cast<ConstantArray>(I)) {
+ ArrayType *VTableTy = C->getType();
+ uint64_t ElemSize = DL.getTypeAllocSize(VTableTy->getElementType());
+
+ unsigned Op = Offset / ElemSize;
+ if (Op >= C->getNumOperands())
+ return nullptr;
+
+ return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
+ Offset % ElemSize, M);
+ }
+ return nullptr;
+}
TypeID}));
}
+void GlobalObject::addVCallVisibilityMetadata(VCallVisibility Visibility) {
+ addMetadata(LLVMContext::MD_vcall_visibility,
+ *MDNode::get(getContext(),
+ {ConstantAsMetadata::get(ConstantInt::get(
+ Type::getInt64Ty(getContext()), Visibility))}));
+}
+
+GlobalObject::VCallVisibility GlobalObject::getVCallVisibility() const {
+ if (MDNode *MD = getMetadata(LLVMContext::MD_vcall_visibility)) {
+ uint64_t Val = cast<ConstantInt>(
+ cast<ConstantAsMetadata>(MD->getOperand(0))->getValue())
+ ->getZExtValue();
+ assert(Val <= 2 && "unknown vcall visibility!");
+ return (VCallVisibility)Val;
+ }
+ return VCallVisibility::VCallVisibilityPublic;
+}
+
void Function::setSubprogram(DISubprogram *SP) {
setMetadata(LLVMContext::MD_dbg, SP);
}
GV->setLinkage(GlobalValue::InternalLinkage);
}
+ RegularLTO.CombinedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
+
if (Conf.PostInternalizeModuleHook &&
!Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))
return Error::success();
internalizeModule(*MergedModule, mustPreserveGV);
+ MergedModule->addModuleFlag(Module::Error, "LTOPostLink", 1);
+
ScopeRestrictionsDone = true;
}
#include "llvm/Transforms/IPO/GlobalDCE.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Utils/CtorUtils.h"
#define DEBUG_TYPE "globaldce"
+static cl::opt<bool>
+ ClEnableVFE("enable-vfe", cl::Hidden, cl::init(true), cl::ZeroOrMore,
+ cl::desc("Enable virtual function elimination"));
+
STATISTIC(NumAliases , "Number of global aliases removed");
STATISTIC(NumFunctions, "Number of functions removed");
STATISTIC(NumIFuncs, "Number of indirect functions removed");
STATISTIC(NumVariables, "Number of global variables removed");
+STATISTIC(NumVFuncs, "Number of virtual functions removed");
namespace {
class GlobalDCELegacyPass : public ModulePass {
ComputeDependencies(User, Deps);
Deps.erase(&GV); // Remove self-reference.
for (GlobalValue *GVU : Deps) {
+ // If this is a dep from a vtable to a virtual function, and we have
+ // complete information about all virtual call sites which could call
+ // though this vtable, then skip it, because the call site information will
+ // be more precise.
+ if (VFESafeVTables.count(GVU) && isa<Function>(&GV)) {
+ LLVM_DEBUG(dbgs() << "Ignoring dep " << GVU->getName() << " -> "
+ << GV.getName() << "\n");
+ continue;
+ }
GVDependencies[GVU].insert(&GV);
}
}
if (Updates)
Updates->push_back(&GV);
if (Comdat *C = GV.getComdat()) {
- for (auto &&CM : make_range(ComdatMembers.equal_range(C)))
+ for (auto &&CM : make_range(ComdatMembers.equal_range(C))) {
MarkLive(*CM.second, Updates); // Recursion depth is only two because only
// globals in the same comdat are visited.
+ }
+ }
+}
+
+void GlobalDCEPass::ScanVTables(Module &M) {
+ SmallVector<MDNode *, 2> Types;
+ LLVM_DEBUG(dbgs() << "Building type info -> vtable map\n");
+
+ auto *LTOPostLinkMD =
+ cast_or_null<ConstantAsMetadata>(M.getModuleFlag("LTOPostLink"));
+ bool LTOPostLink =
+ LTOPostLinkMD &&
+ (cast<ConstantInt>(LTOPostLinkMD->getValue())->getZExtValue() != 0);
+
+ for (GlobalVariable &GV : M.globals()) {
+ Types.clear();
+ GV.getMetadata(LLVMContext::MD_type, Types);
+ if (GV.isDeclaration() || Types.empty())
+ continue;
+
+ // Use the typeid metadata on the vtable to build a mapping from typeids to
+ // the list of (GV, offset) pairs which are the possible vtables for that
+ // typeid.
+ for (MDNode *Type : Types) {
+ Metadata *TypeID = Type->getOperand(1).get();
+
+ uint64_t Offset =
+ cast<ConstantInt>(
+ cast<ConstantAsMetadata>(Type->getOperand(0))->getValue())
+ ->getZExtValue();
+
+ TypeIdMap[TypeID].insert(std::make_pair(&GV, Offset));
+ }
+
+ // If the type corresponding to the vtable is private to this translation
+ // unit, we know that we can see all virtual functions which might use it,
+ // so VFE is safe.
+ if (auto GO = dyn_cast<GlobalObject>(&GV)) {
+ GlobalObject::VCallVisibility TypeVis = GO->getVCallVisibility();
+ if (TypeVis == GlobalObject::VCallVisibilityTranslationUnit ||
+ (LTOPostLink &&
+ TypeVis == GlobalObject::VCallVisibilityLinkageUnit)) {
+ LLVM_DEBUG(dbgs() << GV.getName() << " is safe for VFE\n");
+ VFESafeVTables.insert(&GV);
+ }
+ }
+ }
+}
+
+void GlobalDCEPass::ScanVTableLoad(Function *Caller, Metadata *TypeId,
+ uint64_t CallOffset) {
+ for (auto &VTableInfo : TypeIdMap[TypeId]) {
+ GlobalVariable *VTable = VTableInfo.first;
+ uint64_t VTableOffset = VTableInfo.second;
+
+ Constant *Ptr =
+ getPointerAtOffset(VTable->getInitializer(), VTableOffset + CallOffset,
+ *Caller->getParent());
+ if (!Ptr) {
+ LLVM_DEBUG(dbgs() << "can't find pointer in vtable!\n");
+ VFESafeVTables.erase(VTable);
+ return;
+ }
+
+ auto Callee = dyn_cast<Function>(Ptr->stripPointerCasts());
+ if (!Callee) {
+ LLVM_DEBUG(dbgs() << "vtable entry is not function pointer!\n");
+ VFESafeVTables.erase(VTable);
+ return;
+ }
+
+ LLVM_DEBUG(dbgs() << "vfunc dep " << Caller->getName() << " -> "
+ << Callee->getName() << "\n");
+ GVDependencies[Caller].insert(Callee);
}
}
+void GlobalDCEPass::ScanTypeCheckedLoadIntrinsics(Module &M) {
+ LLVM_DEBUG(dbgs() << "Scanning type.checked.load intrinsics\n");
+ Function *TypeCheckedLoadFunc =
+ M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load));
+
+ if (!TypeCheckedLoadFunc)
+ return;
+
+ for (auto U : TypeCheckedLoadFunc->users()) {
+ auto CI = dyn_cast<CallInst>(U);
+ if (!CI)
+ continue;
+
+ auto *Offset = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+ Value *TypeIdValue = CI->getArgOperand(2);
+ auto *TypeId = cast<MetadataAsValue>(TypeIdValue)->getMetadata();
+
+ if (Offset) {
+ ScanVTableLoad(CI->getFunction(), TypeId, Offset->getZExtValue());
+ } else {
+ // type.checked.load with a non-constant offset, so assume every entry in
+ // every matching vtable is used.
+ for (auto &VTableInfo : TypeIdMap[TypeId]) {
+ VFESafeVTables.erase(VTableInfo.first);
+ }
+ }
+ }
+}
+
+void GlobalDCEPass::AddVirtualFunctionDependencies(Module &M) {
+ if (!ClEnableVFE)
+ return;
+
+ ScanVTables(M);
+
+ if (VFESafeVTables.empty())
+ return;
+
+ ScanTypeCheckedLoadIntrinsics(M);
+
+ LLVM_DEBUG(
+ dbgs() << "VFE safe vtables:\n";
+ for (auto *VTable : VFESafeVTables)
+ dbgs() << " " << VTable->getName() << "\n";
+ );
+}
+
PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
bool Changed = false;
if (Comdat *C = GA.getComdat())
ComdatMembers.insert(std::make_pair(C, &GA));
+ // Add dependencies between virtual call sites and the virtual functions they
+ // might call, if we have that information.
+ AddVirtualFunctionDependencies(M);
+
// Loop over the module, adding globals which are obviously necessary.
for (GlobalObject &GO : M.global_objects()) {
Changed |= RemoveUnusedGlobalValue(GO);
};
NumFunctions += DeadFunctions.size();
- for (Function *F : DeadFunctions)
+ for (Function *F : DeadFunctions) {
+ if (!F->use_empty()) {
+ // Virtual functions might still be referenced by one or more vtables,
+ // but if we've proven them to be unused then it's safe to replace the
+ // virtual function pointers with null, allowing us to remove the
+ // function itself.
+ ++NumVFuncs;
+ F->replaceNonMetadataUsesWith(ConstantPointerNull::get(F->getType()));
+ }
EraseUnusedGlobalValue(F);
+ }
NumVariables += DeadGlobalVars.size();
for (GlobalVariable *GV : DeadGlobalVars)
ConstantDependenciesCache.clear();
GVDependencies.clear();
ComdatMembers.clear();
+ TypeIdMap.clear();
+ VFESafeVTables.clear();
if (Changed)
return PreservedAnalyses::none();
void buildTypeIdentifierMap(
std::vector<VTableBits> &Bits,
DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap);
- Constant *getPointerAtOffset(Constant *I, uint64_t Offset);
bool
tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot,
const std::set<TypeMemberInfo> &TypeMemberInfos,
}
}
-Constant *DevirtModule::getPointerAtOffset(Constant *I, uint64_t Offset) {
- if (I->getType()->isPointerTy()) {
- if (Offset == 0)
- return I;
- return nullptr;
- }
-
- const DataLayout &DL = M.getDataLayout();
-
- if (auto *C = dyn_cast<ConstantStruct>(I)) {
- const StructLayout *SL = DL.getStructLayout(C->getType());
- if (Offset >= SL->getSizeInBytes())
- return nullptr;
-
- unsigned Op = SL->getElementContainingOffset(Offset);
- return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
- Offset - SL->getElementOffset(Op));
- }
- if (auto *C = dyn_cast<ConstantArray>(I)) {
- ArrayType *VTableTy = C->getType();
- uint64_t ElemSize = DL.getTypeAllocSize(VTableTy->getElementType());
-
- unsigned Op = Offset / ElemSize;
- if (Op >= C->getNumOperands())
- return nullptr;
-
- return getPointerAtOffset(cast<Constant>(I->getOperand(Op)),
- Offset % ElemSize);
- }
- return nullptr;
-}
-
bool DevirtModule::tryFindVirtualCallTargets(
std::vector<VirtualCallTarget> &TargetsForSlot,
const std::set<TypeMemberInfo> &TypeMemberInfos, uint64_t ByteOffset) {
return false;
Constant *Ptr = getPointerAtOffset(TM.Bits->GV->getInitializer(),
- TM.Offset + ByteOffset);
+ TM.Offset + ByteOffset, M);
if (!Ptr)
return false;
for (VTableBits &B : Bits)
rebuildGlobal(B);
+ // We have lowered or deleted the type checked load intrinsics, so we no
+ // longer have enough information to reason about the liveness of virtual
+ // function pointers in GlobalDCE.
+ for (GlobalVariable &GV : M.globals())
+ GV.eraseMetadata(LLVMContext::MD_vcall_visibility);
+
return true;
}
--- /dev/null
+; RUN: opt %s -o %t1.bc
+
+; RUN: llvm-lto %t1.bc -o %t1.save.opt -save-merged-module -O1 --exported-symbol=foo
+; RUN: llvm-dis < %t1.save.opt.merged.bc | FileCheck %s
+
+; RUN: llvm-lto2 run %t1.bc -o %t.out.o -save-temps \
+; RUN: -r=%t1.bc,foo,pxl
+; RUN: llvm-dis < %t.out.o.0.2.internalize.bc | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7a-unknown-linux"
+
+define void @foo() {
+entry:
+ ret void
+}
+
+; CHECK: !llvm.module.flags = !{[[MD_NUM:![0-9]+]]}
+; CHECK: [[MD_NUM]] = !{i32 1, !"LTOPostLink", i32 1}
; RUN: llvm-lto -thinlto-action=import %t2.bc -thinlto-index=%t3.bc \
; RUN: -o /dev/null -stats \
; RUN: 2>&1 | FileCheck %s -check-prefix=LAZY
-; LAZY: 63 bitcode-reader - Number of Metadata records loaded
+; LAZY: 65 bitcode-reader - Number of Metadata records loaded
; LAZY: 2 bitcode-reader - Number of MDStrings loaded
; RUN: llvm-lto -thinlto-action=import %t2.bc -thinlto-index=%t3.bc \
; RUN: -o /dev/null -disable-ondemand-mds-loading -stats \
; RUN: 2>&1 | FileCheck %s -check-prefix=NOTLAZY
-; NOTLAZY: 72 bitcode-reader - Number of Metadata records loaded
+; NOTLAZY: 74 bitcode-reader - Number of Metadata records loaded
; NOTLAZY: 7 bitcode-reader - Number of MDStrings loaded
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; struct A {
+; A();
+; virtual int foo();
+; };
+;
+; struct B : A {
+; B();
+; virtual int foo();
+; };
+;
+; A::A() {}
+; B::B() {}
+; int A::foo() { return 42; }
+; int B::foo() { return 1337; }
+;
+; extern "C" int test(A *p) { return p->foo(); }
+
+; The virtual call in test could be dispatched to either A::foo or B::foo, so
+; both must be retained.
+
+%struct.A = type { i32 (...)** }
+%struct.B = type { %struct.A }
+
+; CHECK: @_ZTV1A = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*)] }
+@_ZTV1A = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !2
+
+; CHECK: @_ZTV1B = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*)* @_ZN1B3fooEv to i8*)] }
+@_ZTV1B = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*)* @_ZN1B3fooEv to i8*)] }, align 8, !type !0, !type !1, !type !3, !type !4, !vcall_visibility !2
+
+; CHECK: define internal i32 @_ZN1A3fooEv(
+define internal i32 @_ZN1A3fooEv(%struct.A* nocapture readnone %this) {
+entry:
+ ret i32 42
+}
+
+; CHECK: define internal i32 @_ZN1B3fooEv(
+define internal i32 @_ZN1B3fooEv(%struct.B* nocapture readnone %this) {
+entry:
+ ret i32 1337
+}
+
+define hidden void @_ZN1AC2Ev(%struct.A* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden void @_ZN1BC2Ev(%struct.B* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden i32 @test(%struct.A* %p) {
+entry:
+ %0 = bitcast %struct.A* %p to i8**
+ %vtable1 = load i8*, i8** %0, align 8
+ %1 = tail call { i8*, i1 } @llvm.type.checked.load(i8* %vtable1, i32 0, metadata !"_ZTS1A"), !nosanitize !10
+ %2 = extractvalue { i8*, i1 } %1, 0, !nosanitize !10
+ %3 = bitcast i8* %2 to i32 (%struct.A*)*, !nosanitize !10
+ %call = tail call i32 %3(%struct.A* %p)
+ ret i32 %call
+}
+
+declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata) #2
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFivE.virtual"}
+!2 = !{i64 2}
+!3 = !{i64 16, !"_ZTS1B"}
+!4 = !{i64 16, !"_ZTSM1BFivE.virtual"}
+!10 = !{}
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; struct A {
+; A();
+; virtual int foo(int);
+; virtual int bar(float);
+; };
+;
+; struct B : A {
+; B();
+; virtual int foo(int);
+; virtual int bar(float);
+; };
+;
+; A::A() {}
+; B::B() {}
+; int A::foo(int) { return 1; }
+; int A::bar(float) { return 2; }
+; int B::foo(int) { return 3; }
+; int B::bar(float) { return 4; }
+;
+; extern "C" int test(A *p, int (A::*q)(int)) { return (p->*q)(42); }
+
+; Member function pointers are tracked by the combination of their object type
+; and function type, which must both be compatible. Here, the call is through a
+; pointer of type "int (A::*q)(int)", so the call could be dispatched to A::foo
+; or B::foo. It can't be dispatched to A::bar or B::bar as the function pointer
+; does not match, so those can be removed.
+
+%struct.A = type { i32 (...)** }
+%struct.B = type { %struct.A }
+
+; CHECK: @_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A3fooEi to i8*), i8* null] }
+@_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A3fooEi to i8*), i8* bitcast (i32 (%struct.A*, float)* @_ZN1A3barEf to i8*)] }, align 8, !type !0, !type !1, !type !2, !vcall_visibility !3
+; CHECK: @_ZTV1B = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B3fooEi to i8*), i8* null] }
+@_ZTV1B = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B3fooEi to i8*), i8* bitcast (i32 (%struct.B*, float)* @_ZN1B3barEf to i8*)] }, align 8, !type !0, !type !1, !type !2, !type !4, !type !5, !type !6, !vcall_visibility !3
+
+
+; CHECK: define internal i32 @_ZN1A3fooEi(
+define internal i32 @_ZN1A3fooEi(%struct.A* nocapture readnone %this, i32) unnamed_addr #1 align 2 {
+entry:
+ ret i32 1
+}
+
+; CHECK-NOT: define internal i32 @_ZN1A3barEf(
+define internal i32 @_ZN1A3barEf(%struct.A* nocapture readnone %this, float) unnamed_addr #1 align 2 {
+entry:
+ ret i32 2
+}
+
+; CHECK: define internal i32 @_ZN1B3fooEi(
+define internal i32 @_ZN1B3fooEi(%struct.B* nocapture readnone %this, i32) unnamed_addr #1 align 2 {
+entry:
+ ret i32 3
+}
+
+; CHECK-NOT: define internal i32 @_ZN1B3barEf(
+define internal i32 @_ZN1B3barEf(%struct.B* nocapture readnone %this, float) unnamed_addr #1 align 2 {
+entry:
+ ret i32 4
+}
+
+
+define hidden void @_ZN1AC2Ev(%struct.A* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden void @_ZN1BC2Ev(%struct.B* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden i32 @test(%struct.A* %p, i64 %q.coerce0, i64 %q.coerce1) {
+entry:
+ %0 = bitcast %struct.A* %p to i8*
+ %1 = getelementptr inbounds i8, i8* %0, i64 %q.coerce1
+ %this.adjusted = bitcast i8* %1 to %struct.A*
+ %2 = and i64 %q.coerce0, 1
+ %memptr.isvirtual = icmp eq i64 %2, 0
+ br i1 %memptr.isvirtual, label %memptr.nonvirtual, label %memptr.virtual
+
+memptr.virtual: ; preds = %entry
+ %3 = bitcast i8* %1 to i8**
+ %vtable = load i8*, i8** %3, align 8
+ %4 = add i64 %q.coerce0, -1
+ %5 = getelementptr i8, i8* %vtable, i64 %4, !nosanitize !12
+ %6 = tail call { i8*, i1 } @llvm.type.checked.load(i8* %5, i32 0, metadata !"_ZTSM1AFiiE.virtual"), !nosanitize !12
+ %7 = extractvalue { i8*, i1 } %6, 0, !nosanitize !12
+ %memptr.virtualfn = bitcast i8* %7 to i32 (%struct.A*, i32)*, !nosanitize !12
+ br label %memptr.end
+
+memptr.nonvirtual: ; preds = %entry
+ %memptr.nonvirtualfn = inttoptr i64 %q.coerce0 to i32 (%struct.A*, i32)*
+ br label %memptr.end
+
+memptr.end: ; preds = %memptr.nonvirtual, %memptr.virtual
+ %8 = phi i32 (%struct.A*, i32)* [ %memptr.virtualfn, %memptr.virtual ], [ %memptr.nonvirtualfn, %memptr.nonvirtual ]
+ %call = tail call i32 %8(%struct.A* %this.adjusted, i32 42)
+ ret i32 %call
+}
+
+declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata)
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFiiE.virtual"}
+!2 = !{i64 24, !"_ZTSM1AFifE.virtual"}
+!3 = !{i64 2}
+!4 = !{i64 16, !"_ZTS1B"}
+!5 = !{i64 16, !"_ZTSM1BFiiE.virtual"}
+!6 = !{i64 24, !"_ZTSM1BFifE.virtual"}
+!12 = !{}
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; struct A {
+; A();
+; virtual int foo();
+; };
+;
+; struct B : A {
+; B();
+; virtual int foo();
+; };
+;
+; A::A() {}
+; B::B() {}
+; int A::foo() { return 42; }
+; int B::foo() { return 1337; }
+;
+; extern "C" int test(B *p) { return p->foo(); }
+
+; The virtual call in test can only be dispatched to B::foo (or a more-derived
+; class, if there was one), so A::foo can be removed.
+
+%struct.A = type { i32 (...)** }
+%struct.B = type { %struct.A }
+
+; CHECK: @_ZTV1A = internal unnamed_addr constant { [3 x i8*] } zeroinitializer
+@_ZTV1A = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !2
+
+; CHECK: @_ZTV1B = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*)* @_ZN1B3fooEv to i8*)] }
+@_ZTV1B = internal unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*)* @_ZN1B3fooEv to i8*)] }, align 8, !type !0, !type !1, !type !3, !type !4, !vcall_visibility !2
+
+; CHECK-NOT: define internal i32 @_ZN1A3fooEv(
+define internal i32 @_ZN1A3fooEv(%struct.A* nocapture readnone %this) {
+entry:
+ ret i32 42
+}
+
+; CHECK: define internal i32 @_ZN1B3fooEv(
+define internal i32 @_ZN1B3fooEv(%struct.B* nocapture readnone %this) {
+entry:
+ ret i32 1337
+}
+
+define hidden void @_ZN1AC2Ev(%struct.A* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden void @_ZN1BC2Ev(%struct.B* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden i32 @test(%struct.B* %p) {
+entry:
+ %0 = bitcast %struct.B* %p to i8**
+ %vtable1 = load i8*, i8** %0, align 8
+ %1 = tail call { i8*, i1 } @llvm.type.checked.load(i8* %vtable1, i32 0, metadata !"_ZTS1B"), !nosanitize !10
+ %2 = extractvalue { i8*, i1 } %1, 0, !nosanitize !10
+ %3 = bitcast i8* %2 to i32 (%struct.B*)*, !nosanitize !10
+ %call = tail call i32 %3(%struct.B* %p)
+ ret i32 %call
+}
+
+declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata) #2
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFivE.virtual"}
+!2 = !{i64 2}
+!3 = !{i64 16, !"_ZTS1B"}
+!4 = !{i64 16, !"_ZTSM1BFivE.virtual"}
+!10 = !{}
--- /dev/null
+
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+; struct A {
+; A();
+; virtual int foo(int);
+; virtual int bar(float);
+; };
+;
+; struct B : A {
+; B();
+; virtual int foo(int);
+; virtual int bar(float);
+; };
+;
+; A::A() {}
+; B::B() {}
+; int A::foo(int) { return 1; }
+; int A::bar(float) { return 2; }
+; int B::foo(int) { return 3; }
+; int B::bar(float) { return 4; }
+;
+; extern "C" int test(B *p, int (B::*q)(int)) { return (p->*q)(42); }
+
+; Member function pointers are tracked by the combination of their object type
+; and function type, which must both be compatible. Here, the call is through a
+; pointer of type "int (B::*q)(int)", so the call could only be dispatched to
+; B::foo. It can't be dispatched to A::bar or B::bar as the function pointer
+; does not match, and it can't be dispatched to A::foo as the object type
+; doesn't match, so those can be removed.
+
+%struct.A = type { i32 (...)** }
+%struct.B = type { %struct.A }
+
+; CHECK: @_ZTV1A = internal unnamed_addr constant { [4 x i8*] } zeroinitializer
+@_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*, i32)* @_ZN1A3fooEi to i8*), i8* bitcast (i32 (%struct.A*, float)* @_ZN1A3barEf to i8*)] }, align 8, !type !0, !type !1, !type !2, !vcall_visibility !3
+; CHECK: @_ZTV1B = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B3fooEi to i8*), i8* null] }
+@_ZTV1B = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.B*, i32)* @_ZN1B3fooEi to i8*), i8* bitcast (i32 (%struct.B*, float)* @_ZN1B3barEf to i8*)] }, align 8, !type !0, !type !1, !type !2, !type !4, !type !5, !type !6, !vcall_visibility !3
+
+
+; CHECK-NOT: define internal i32 @_ZN1A3fooEi(
+define internal i32 @_ZN1A3fooEi(%struct.A* nocapture readnone %this, i32) unnamed_addr #1 align 2 {
+entry:
+ ret i32 1
+}
+
+; CHECK-NOT: define internal i32 @_ZN1A3barEf(
+define internal i32 @_ZN1A3barEf(%struct.A* nocapture readnone %this, float) unnamed_addr #1 align 2 {
+entry:
+ ret i32 2
+}
+
+; CHECK: define internal i32 @_ZN1B3fooEi(
+define internal i32 @_ZN1B3fooEi(%struct.B* nocapture readnone %this, i32) unnamed_addr #1 align 2 {
+entry:
+ ret i32 3
+}
+
+; CHECK-NOT: define internal i32 @_ZN1B3barEf(
+define internal i32 @_ZN1B3barEf(%struct.B* nocapture readnone %this, float) unnamed_addr #1 align 2 {
+entry:
+ ret i32 4
+}
+
+
+define hidden void @_ZN1AC2Ev(%struct.A* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden void @_ZN1BC2Ev(%struct.B* nocapture %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+define hidden i32 @test(%struct.B* %p, i64 %q.coerce0, i64 %q.coerce1) {
+entry:
+ %0 = bitcast %struct.B* %p to i8*
+ %1 = getelementptr inbounds i8, i8* %0, i64 %q.coerce1
+ %this.adjusted = bitcast i8* %1 to %struct.B*
+ %2 = and i64 %q.coerce0, 1
+ %memptr.isvirtual = icmp eq i64 %2, 0
+ br i1 %memptr.isvirtual, label %memptr.nonvirtual, label %memptr.virtual
+
+memptr.virtual: ; preds = %entry
+ %3 = bitcast i8* %1 to i8**
+ %vtable = load i8*, i8** %3, align 8
+ %4 = add i64 %q.coerce0, -1
+ %5 = getelementptr i8, i8* %vtable, i64 %4, !nosanitize !12
+ %6 = tail call { i8*, i1 } @llvm.type.checked.load(i8* %5, i32 0, metadata !"_ZTSM1BFiiE.virtual"), !nosanitize !12
+ %7 = extractvalue { i8*, i1 } %6, 0, !nosanitize !12
+ %memptr.virtualfn = bitcast i8* %7 to i32 (%struct.B*, i32)*, !nosanitize !12
+ br label %memptr.end
+
+memptr.nonvirtual: ; preds = %entry
+ %memptr.nonvirtualfn = inttoptr i64 %q.coerce0 to i32 (%struct.B*, i32)*
+ br label %memptr.end
+
+memptr.end: ; preds = %memptr.nonvirtual, %memptr.virtual
+ %8 = phi i32 (%struct.B*, i32)* [ %memptr.virtualfn, %memptr.virtual ], [ %memptr.nonvirtualfn, %memptr.nonvirtual ]
+ %call = tail call i32 %8(%struct.B* %this.adjusted, i32 42)
+ ret i32 %call
+}
+
+declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata)
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFiiE.virtual"}
+!2 = !{i64 24, !"_ZTSM1AFifE.virtual"}
+!3 = !{i64 2}
+!4 = !{i64 16, !"_ZTS1B"}
+!5 = !{i64 16, !"_ZTSM1BFiiE.virtual"}
+!6 = !{i64 24, !"_ZTSM1BFifE.virtual"}
+!12 = !{}
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+; structs A, B and C have vcall_visibility of public, linkage-unit and
+; translation-unit respectively. This test is run after LTO linking (the
+; LTOPostLink metadata is present), so B and C can be VFE'd.
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+
+%struct.A = type { i32 (...)** }
+
+@_ZTV1A = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !2
+
+define internal void @_ZN1AC2Ev(%struct.A* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK: define {{.*}} @_ZN1A3fooEv(
+define internal void @_ZN1A3fooEv(%struct.A* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Av() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.A*
+ tail call void @_ZN1AC2Ev(%struct.A* %0)
+ ret i8* %call
+}
+
+
+%struct.B = type { i32 (...)** }
+
+@_ZTV1B = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.B*)* @_ZN1B3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !3
+
+define internal void @_ZN1BC2Ev(%struct.B* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK-NOT: define {{.*}} @_ZN1B3fooEv(
+define internal void @_ZN1B3fooEv(%struct.B* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Bv() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.B*
+ tail call void @_ZN1BC2Ev(%struct.B* %0)
+ ret i8* %call
+}
+
+
+%struct.C = type { i32 (...)** }
+
+@_ZTV1C = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.C*)* @_ZN1C3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !4
+
+define internal void @_ZN1CC2Ev(%struct.C* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.C, %struct.C* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1C, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK-NOT: define {{.*}} @_ZN1C3fooEv(
+define internal void @_ZN1C3fooEv(%struct.C* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Cv() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.C*
+ tail call void @_ZN1CC2Ev(%struct.C* %0)
+ ret i8* %call
+}
+
+declare dso_local noalias nonnull i8* @_Znwm(i64)
+
+!llvm.module.flags = !{!5}
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
+!2 = !{i64 0} ; public vcall visibility
+!3 = !{i64 1} ; linkage-unit vcall visibility
+!4 = !{i64 2} ; translation-unit vcall visibility
+!5 = !{i32 1, !"LTOPostLink", i32 1}
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+; structs A, B and C have vcall_visibility of public, linkage-unit and
+; translation-unit respectively. This test is run before LTO linking occurs
+; (the LTOPostLink metadata is not present), so only C can be VFE'd.
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+
+%struct.A = type { i32 (...)** }
+
+@_ZTV1A = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !2
+
+define internal void @_ZN1AC2Ev(%struct.A* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK: define {{.*}} @_ZN1A3fooEv(
+define internal void @_ZN1A3fooEv(%struct.A* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Av() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.A*
+ tail call void @_ZN1AC2Ev(%struct.A* %0)
+ ret i8* %call
+}
+
+
+%struct.B = type { i32 (...)** }
+
+@_ZTV1B = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.B*)* @_ZN1B3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !3
+
+define internal void @_ZN1BC2Ev(%struct.B* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.B, %struct.B* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1B, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK: define {{.*}} @_ZN1B3fooEv(
+define internal void @_ZN1B3fooEv(%struct.B* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Bv() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.B*
+ tail call void @_ZN1BC2Ev(%struct.B* %0)
+ ret i8* %call
+}
+
+
+%struct.C = type { i32 (...)** }
+
+@_ZTV1C = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.C*)* @_ZN1C3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !4
+
+define internal void @_ZN1CC2Ev(%struct.C* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.C, %struct.C* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1C, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK-NOT: define {{.*}} @_ZN1C3fooEv(
+define internal void @_ZN1C3fooEv(%struct.C* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Cv() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.C*
+ tail call void @_ZN1CC2Ev(%struct.C* %0)
+ ret i8* %call
+}
+
+declare dso_local noalias nonnull i8* @_Znwm(i64)
+
+!llvm.module.flags = !{}
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
+!2 = !{i64 0} ; public vcall visibility
+!3 = !{i64 1} ; linkage-unit vcall visibility
+!4 = !{i64 2} ; translation-unit vcall visibility
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+declare dso_local noalias nonnull i8* @_Znwm(i64)
+declare { i8*, i1 } @llvm.type.checked.load(i8*, i32, metadata)
+
+; %struct.A is a C++ struct with two virtual functions, A::foo and A::bar. The
+; !vcall_visibility metadata is set on the vtable, so we know that all virtual
+; calls through this vtable are visible and use the @llvm.type.checked.load
+; intrinsic. Function test_A makes a call to A::foo, but there is no call to
+; A::bar anywhere, so A::bar can be deleted, and its vtable slot replaced with
+; null.
+
+%struct.A = type { i32 (...)** }
+
+; The pointer to A::bar in the vtable can be removed, because it will never be
+; loaded. We replace it with null to keep the layout the same. Because it is at
+; the end of the vtable we could potentially shrink the vtable, but don't
+; currently do that.
+; CHECK: @_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*), i8* null] }
+@_ZTV1A = internal unnamed_addr constant { [4 x i8*] } { [4 x i8*] [i8* null, i8* null, i8* bitcast (i32 (%struct.A*)* @_ZN1A3fooEv to i8*), i8* bitcast (i32 (%struct.A*)* @_ZN1A3barEv to i8*)] }, align 8, !type !0, !type !1, !type !2, !vcall_visibility !3
+
+; A::foo is called, so must be retained.
+; CHECK: define internal i32 @_ZN1A3fooEv(
+define internal i32 @_ZN1A3fooEv(%struct.A* nocapture readnone %this) {
+entry:
+ ret i32 42
+}
+
+; A::bar is not used, so can be deleted.
+; CHECK-NOT: define internal i32 @_ZN1A3barEv(
+define internal i32 @_ZN1A3barEv(%struct.A* nocapture readnone %this) {
+entry:
+ ret i32 1337
+}
+
+define dso_local i32 @test_A() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.A*
+ %1 = bitcast i8* %call to i32 (...)***
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %1, align 8
+ %2 = tail call { i8*, i1 } @llvm.type.checked.load(i8* bitcast (i8** getelementptr inbounds ({ [4 x i8*] }, { [4 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i8*), i32 0, metadata !"_ZTS1A"), !nosanitize !9
+ %3 = extractvalue { i8*, i1 } %2, 0, !nosanitize !9
+ %4 = bitcast i8* %3 to i32 (%struct.A*)*, !nosanitize !9
+ %call1 = tail call i32 %4(%struct.A* nonnull %0)
+ ret i32 %call1
+}
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFivE.virtual"}
+!2 = !{i64 24, !"_ZTSM1AFivE.virtual"}
+!3 = !{i64 2}
+!9 = !{}
--- /dev/null
+; RUN: opt < %s -globaldce -S | FileCheck %s
+
+; We currently only use llvm.type.checked.load for virtual function pointers,
+; not any other part of the vtable, so we can't remove the RTTI pointer even if
+; it's never going to be loaded from.
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+
+%struct.A = type { i32 (...)** }
+
+; CHECK: @_ZTV1A = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI1A to i8*), i8* null] }, align 8, !type !0, !type !1, !vcall_visibility !2
+
+@_ZTV1A = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* bitcast ({ i8*, i8* }* @_ZTI1A to i8*), i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1, !vcall_visibility !2
+@_ZTS1A = hidden constant [3 x i8] c"1A\00", align 1
+@_ZTI1A = hidden constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8*, i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([3 x i8], [3 x i8]* @_ZTS1A, i32 0, i32 0) }, align 8
+
+define internal void @_ZN1AC2Ev(%struct.A* %this) {
+entry:
+ %0 = getelementptr inbounds %struct.A, %struct.A* %this, i64 0, i32 0
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1A, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret void
+}
+
+; CHECK-NOT: define {{.*}} @_ZN1A3fooEv(
+define internal void @_ZN1A3fooEv(%struct.A* nocapture %this) {
+entry:
+ ret void
+}
+
+define dso_local i8* @_Z6make_Av() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8)
+ %0 = bitcast i8* %call to %struct.A*
+ tail call void @_ZN1AC2Ev(%struct.A* %0)
+ ret i8* %call
+}
+
+
+declare dso_local noalias nonnull i8* @_Znwm(i64)
+@_ZTVN10__cxxabiv117__class_type_infoE = external dso_local global i8*
+
+!llvm.module.flags = !{!3}
+
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
+!2 = !{i64 2} ; translation-unit vcall visibility
+!3 = !{i32 1, !"LTOPostLink", i32 1}
--- /dev/null
+; RUN: opt < %s -internalize -S | FileCheck %s
+
+%struct.A = type { i32 (...)** }
+%struct.B = type { i32 (...)** }
+%struct.C = type { i32 (...)** }
+
+; Class A has default visibility, so has no !vcall_visibility metadata before
+; or after LTO.
+; CHECK-NOT: @_ZTV1A = {{.*}}!vcall_visibility
+@_ZTV1A = dso_local unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)] }, align 8, !type !0, !type !1
+
+; Class B has hidden visibility but public LTO visibility, so has no
+; !vcall_visibility metadata before or after LTO.
+; CHECK-NOT: @_ZTV1B = {{.*}}!vcall_visibility
+@_ZTV1B = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.B*)* @_ZN1B3fooEv to i8*)] }, align 8, !type !2, !type !3
+
+; Class C has hidden visibility, so the !vcall_visibility metadata is set to 1
+; (linkage unit) before LTO, and 2 (translation unit) after LTO.
+; CHECK: @_ZTV1C ={{.*}}!vcall_visibility [[MD_TU_VIS:![0-9]+]]
+@_ZTV1C = hidden unnamed_addr constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* null, i8* bitcast (void (%struct.C*)* @_ZN1C3fooEv to i8*)] }, align 8, !type !4, !type !5, !vcall_visibility !6
+
+; Class D has translation unit visibility before LTO, and this is not changed
+; by LTO.
+; CHECK: @_ZTVN12_GLOBAL__N_11DE = {{.*}}!vcall_visibility [[MD_TU_VIS:![0-9]+]]
+@_ZTVN12_GLOBAL__N_11DE = internal unnamed_addr constant { [3 x i8*] } zeroinitializer, align 8, !type !7, !type !9, !vcall_visibility !11
+
+define dso_local void @_ZN1A3fooEv(%struct.A* nocapture %this) {
+entry:
+ ret void
+}
+
+define hidden void @_ZN1B3fooEv(%struct.B* nocapture %this) {
+entry:
+ ret void
+}
+
+define hidden void @_ZN1C3fooEv(%struct.C* nocapture %this) {
+entry:
+ ret void
+}
+
+define hidden noalias nonnull i8* @_Z6make_dv() {
+entry:
+ %call = tail call i8* @_Znwm(i64 8) #3
+ %0 = bitcast i8* %call to i32 (...)***
+ store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTVN12_GLOBAL__N_11DE, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+ ret i8* %call
+}
+
+declare dso_local noalias nonnull i8* @_Znwm(i64)
+
+; CHECK: [[MD_TU_VIS]] = !{i64 2}
+!0 = !{i64 16, !"_ZTS1A"}
+!1 = !{i64 16, !"_ZTSM1AFvvE.virtual"}
+!2 = !{i64 16, !"_ZTS1B"}
+!3 = !{i64 16, !"_ZTSM1BFvvE.virtual"}
+!4 = !{i64 16, !"_ZTS1C"}
+!5 = !{i64 16, !"_ZTSM1CFvvE.virtual"}
+!6 = !{i64 1}
+!7 = !{i64 16, !8}
+!8 = distinct !{}
+!9 = !{i64 16, !10}
+!10 = distinct !{}
+!11 = !{i64 2}
projects / platform / upstream / llvm.git / commitdiff