Merge from 'master' to 'sycl-web' (intel#22)

  CONFLICT (content): Merge conflict in clang/lib/Driver/ToolChains/Clang.cpp

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)

clang/include/clang/Driver/Options.td

@@ -1935,6 +1935,13 @@ 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]>,

clang/lib/CodeGen/CGClass.cpp

@@ -2786,11 +2786,16 @@ 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);
@@ -2813,8 +2818,13 @@ 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),

clang/lib/CodeGen/CGExpr.cpp

@@ -2831,7 +2831,6 @@ llvm::Constant *CodeGenFunction::EmitCheckTypeDescriptor(QualType T) {
       CGM.getModule(), Descriptor->getType(),
       /*isConstant=*/true, llvm::GlobalVariable::PrivateLinkage, Descriptor);
   GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
-  CGM.setPragmaSectionAttributes(CurFuncDecl, GV);
   CGM.getSanitizerMetadata()->disableSanitizerForGlobal(GV);
 
   // Remember the descriptor for this type.
@@ -2911,7 +2910,6 @@ llvm::Constant *CodeGenFunction::EmitCheckSourceLocation(SourceLocation Loc) {
     }
 
     auto FilenameGV = CGM.GetAddrOfConstantCString(FilenameString, ".src");
-    CGM.setPragmaSectionAttributes(CurFuncDecl, cast<llvm::GlobalVariable>(FilenameGV.getPointer()));
     CGM.getSanitizerMetadata()->disableSanitizerForGlobal(
                           cast<llvm::GlobalVariable>(FilenameGV.getPointer()));
     Filename = FilenameGV.getPointer();
@@ -3085,7 +3083,6 @@ void CodeGenFunction::EmitCheck(
           new llvm::GlobalVariable(CGM.getModule(), Info->getType(), false,
                                    llvm::GlobalVariable::PrivateLinkage, Info);
       InfoPtr->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
-      CGM.setPragmaSectionAttributes(CurFuncDecl, InfoPtr);
       CGM.getSanitizerMetadata()->disableSanitizerForGlobal(InfoPtr);
       Args.push_back(Builder.CreateBitCast(InfoPtr, Int8PtrTy));
       ArgTypes.push_back(Int8PtrTy);

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);
+  }
 }

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1732,8 +1732,11 @@ bool CodeGenModule::GetCPUAndFeaturesAttributes(GlobalDecl GD,
   return AddedAttr;
 }
 
-void CodeGenModule::setPragmaSectionAttributes(const Decl *D,
-					       llvm::GlobalObject *GO) {
+void CodeGenModule::setNonAliasAttributes(GlobalDecl GD,
+                                          llvm::GlobalObject *GO) {
+  const Decl *D = GD.getDecl();
+  SetCommonAttributes(GD, GO);
+
   if (D) {
     if (auto *GV = dyn_cast<llvm::GlobalVariable>(GO)) {
       if (auto *SA = D->getAttr<PragmaClangBSSSectionAttr>())
@@ -1751,26 +1754,6 @@ void CodeGenModule::setPragmaSectionAttributes(const Decl *D,
         if (!D->getAttr<SectionAttr>())
           F->addFnAttr("implicit-section-name", SA->getName());
 
-      if (auto *SA = D->getAttr<PragmaClangBSSSectionAttr>())
-        F->addFnAttr("bss-section", SA->getName());
-      if (auto *SA = D->getAttr<PragmaClangDataSectionAttr>())
-        F->addFnAttr("data-section", SA->getName());
-      if (auto *SA = D->getAttr<PragmaClangRodataSectionAttr>())
-        F->addFnAttr("rodata-section", SA->getName());
-      if (auto *SA = D->getAttr<PragmaClangRelroSectionAttr>())
-        F->addFnAttr("relro-section", SA->getName());
-    }
-  }
-}
-
-void CodeGenModule::setNonAliasAttributes(GlobalDecl GD,
-                                          llvm::GlobalObject *GO) {
-  const Decl *D = GD.getDecl();
-  SetCommonAttributes(GD, GO);
-  setPragmaSectionAttributes(D, GO);
-
-  if (D) {
-    if (auto *F = dyn_cast<llvm::Function>(GO)) {
       llvm::AttrBuilder Attrs;
       if (GetCPUAndFeaturesAttributes(GD, Attrs)) {
         // We know that GetCPUAndFeaturesAttributes will always have the

clang/lib/CodeGen/CodeGenModule.h

@@ -1293,8 +1293,16 @@ class CodeGenModule : public CodeGenTypeCache {
   /// 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.
@@ -1360,11 +1368,6 @@ class CodeGenModule : public CodeGenTypeCache {
   /// \param QT is the clang QualType of the null pointer.
   llvm::Constant *getNullPointer(llvm::PointerType *T, QualType QT);
 
-  /// Set section attributes requested by "#pragma clang section"
-  ///  \param D is the declaration to read semantic attributes from.
-  ///  \param GO is the global object to set section attributes.
-  void setPragmaSectionAttributes(const Decl *D, llvm::GlobalObject *GO);
-
 private:
   llvm::Constant *GetOrCreateLLVMFunction(
       StringRef MangledName, llvm::Type *Ty, GlobalDecl D, bool ForVTable,

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -644,53 +644,88 @@ 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.
   llvm::Constant *CheckSourceLocation;
   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(

clang/lib/Driver/ToolChains/Clang.cpp

@@ -5505,9 +5505,30 @@ 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)

clang/lib/Frontend/CompilerInvocation.cpp

@@ -759,6 +759,8 @@ 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);