[DWARF5] Added support for deleted C++ special member functions.

[SouraVX]

Summary

This patch adds support for deleted C++ special member functions in clang and llvm. Also added Defaulted member encodings for future support for defaulted member functions.

[SouraVX]

llvm/test/DebugInfo/X86/DW_AT_deleted.ll

69

Removed all stringified attributes that aren't strictly necessary -- as mentioned by @aprantl in noreturn patch review.

[SouraVX]

Corrected typo in test case.

[aprantl]

clang/lib/CodeGen/CGDebugInfo.cpp

1610

We spell this a DWARF v5 throughout the sources, makes it easier to grep for.

Then again, we probably shouldn't be mentioning DWARF here at all.

1612

We usually don't commit TODO notes into the source code.

1621

this should be else if, or, perhaps slightly better switch(Method.getKind()).

llvm/include/llvm/IR/DebugInfoFlags.def

92

?

[aprantl]

Can you add the new flag to either SourceLevelDebugging.rst or LangRef.rst (wherever it fits better)?

[SouraVX]

Addressed comments.

[SouraVX]

Thanks Adrian for reviewing this! I've addressed your comments. Please have a look.
Working on the adding documentation part.

clang/lib/CodeGen/CGDebugInfo.cpp

1624

Hi Adrian, is this fine under switch case, or shall I move it outside ??

llvm/include/llvm/IR/DebugInfoFlags.def

92

Wanted to add a note, for future support of Defaulted member functions, they can utilize{or overload} this bit.
As this Defaulted or Deleted are mutually exclusive.
Is this fine ??

[SouraVX]

Updated the documentation for this new flag.

[SouraVX]

Hi @aprantl, could you please review these changes, while I rework on the other one. Thanks!

[aprantl]

llvm/docs/SourceLevelDebugging.rst

998

let's not say "new" here; this document will live for a long time. How about: DWARF v5 introduce attributes defined to ...

[SouraVX]

Updated doc.

[SouraVX]

Hi Adrian, Thanks for taking out time for reviewing this. I've again updated doc.
Currently we're in process of getting commit access, discussion with Tom in progress

So, could you please commit these changes.
Thank you so much!

clang/lib/CodeGen/CGDebugInfo.cpp

if (CGM.getTarget().getCXXABI().isItaniumFamily()) {
       // it knows the dynamic type of an object.
       ThisAdjustment = CGM.getCXXABI()
                            .getVirtualFunctionPrologueThisAdjustment(GD)
                            .getQuantity();
     }
     ContainingType = RecordTy;
   }
 
+  // We're checking for deleted C++ special member functions
+  // [Ctors,Dtors, Copy/Move]
+  auto checkAttrDeleted = [&SPFlags](const auto *Method) {
+    if (Method->getCanonicalDecl()->isDeleted())
+      SPFlags |= llvm::DISubprogram::SPFlagDeleted;
+  };
+
+  switch (Method->getKind()) {
+
+  case Decl::CXXConstructor:
+  case Decl::CXXDestructor:
+    checkAttrDeleted(Method);
+    break;
+  case Decl::CXXMethod:
+    if (Method->isCopyAssignmentOperator() ||
+        Method->isMoveAssignmentOperator())
+      checkAttrDeleted(Method);
+    break;
+  default:
+    break;
+  }
+
   if (Method->isNoReturn())
     Flags |= llvm::DINode::FlagNoReturn;
+
   if (Method->isStatic())
     Flags |= llvm::DINode::FlagStaticMember;
   if (Method->isImplicit())
     Flags |= llvm::DINode::FlagArtificial;
   Flags |= getAccessFlag(Method->getAccess(), Method->getParent());
   if (const auto *CXXC = dyn_cast<CXXConstructorDecl>(Method)) {
     if (CXXC->isExplicit())
       Flags |= llvm::DINode::FlagExplicit;

clang/test/CodeGenCXX/debug-info-deleted.cpp

+// Test for debug info for C++11 deleted member functions
+
+//Supported: -O0, standalone DI
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-linux-gnu %s -o - \
+// RUN:   -O0 -disable-llvm-passes \
+// RUN:   -debug-info-kind=standalone \
+// RUN: | FileCheck %s -check-prefix=ATTR
+
+// ATTR: DISubprogram(name: "deleted", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped,
+// ATTR: DISubprogram(name: "deleted", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted
+// ATTR: DISubprogram(name: "operator=", linkageName: "_ZN7deletedaSERKS_", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted
+// ATTR: DISubprogram(name: "deleted", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted
+// ATTR: DISubprogram(name: "operator=", linkageName: "_ZN7deletedaSEOS_", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted
+// ATTR: DISubprogram(name: "~deleted", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped,
+class deleted {
+public:
+  // Defaulted on purpose, so as to facilitate object creation
+  deleted() = default;
+
+  deleted(const deleted &) = delete;
+  deleted &operator=(const deleted &) = delete;
+
+  deleted(deleted &&) = delete;
+  deleted &operator=(deleted &&) = delete;
+
+  ~deleted() = default;
+};
+
+void foo() {
+  deleted obj1;
+}

llvm/docs/SourceLevelDebugging.rst

.. code-block:: text
 
   ;;
   ;; Define the subprogram itself.
   ;;
   define i32 @main(i32 %argc, i8** %argv) !dbg !4 {
   ...
   }
 
+C++ specific debug information
+==============================
+
+C++ special member functions information
+----------------------------------------
+
+DWARF v5 introduces attributes defined to enhance debugging information of C++ programs. LLVM can generate (or omit) these appropriate DWARF attributes. In C++ a special member function Ctors, Dtors, Copy/Move Ctors, assignment operators can be declared with C++11 keyword deleted. This is represented in LLVM using spFlags value DISPFlagDeleted.
+
+Given a class declaration with copy constructor declared as deleted:
+
+.. code-block:: c
+
+  class foo {
+   public:
+     foo(const foo&) = deleted;
+  };
+
+A C++ frontend would generate follwing:
+
+.. code-block:: text
+
+  !17 = !DISubprogram(name: "foo", scope: !11, file: !1, line: 5, type: !18, scopeLine: 5, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted)
+
+and this will produce an additional DWARF attibute as:
+
+.. code-block:: text
+
+  DW_TAG_subprogram [7] *
+    DW_AT_name [DW_FORM_strx1]    (indexed (00000006) string = "foo")
+    DW_AT_decl_line [DW_FORM_data1]       (5)
+    ...
+    DW_AT_deleted [DW_FORM_flag_present]  (true)
+
 Fortran specific debug information
 ==================================
 
 Fortran function information
 ----------------------------
 
 There are a few DWARF attributes defined to support client debugging of Fortran programs.  LLVM can generate (or omit) the appropriate DWARF attributes for the prefix-specs of ELEMENTAL, PURE, IMPURE, RECURSIVE, and NON_RECURSIVE.  This is done by using the spFlags values: DISPFlagElemental, DISPFlagPure, and DISPFlagRecursive.
 

llvm/include/llvm/BinaryFormat/Dwarf.h

 StringRef ChildrenString(unsigned Children);
 StringRef AttributeString(unsigned Attribute);
 StringRef FormEncodingString(unsigned Encoding);
 StringRef OperationEncodingString(unsigned Encoding);
 StringRef AttributeEncodingString(unsigned Encoding);
 StringRef DecimalSignString(unsigned Sign);
 StringRef EndianityString(unsigned Endian);
 StringRef AccessibilityString(unsigned Access);
+StringRef DefaultedMemberString(unsigned DefaultedEncodings);
 StringRef VisibilityString(unsigned Visibility);
 StringRef VirtualityString(unsigned Virtuality);
 StringRef LanguageString(unsigned Language);
 StringRef CaseString(unsigned Case);
 StringRef ConventionString(unsigned Convention);
 StringRef InlineCodeString(unsigned Code);
 StringRef ArrayOrderString(unsigned Order);
 StringRef LNStandardString(unsigned Standard);

llvm/include/llvm/IR/DebugInfoFlags.def

 HANDLE_DISP_FLAG(2u, PureVirtual)
 HANDLE_DISP_FLAG((1u << 2), LocalToUnit)
 HANDLE_DISP_FLAG((1u << 3), Definition)
 HANDLE_DISP_FLAG((1u << 4), Optimized)
 HANDLE_DISP_FLAG((1u << 5), Pure)
 HANDLE_DISP_FLAG((1u << 6), Elemental)
 HANDLE_DISP_FLAG((1u << 7), Recursive)
 HANDLE_DISP_FLAG((1u << 8), MainSubprogram)
+// May also utilize this Flag in future, when adding support
+// for defaulted functions
+HANDLE_DISP_FLAG((1u << 9), Deleted)
 
 #ifdef DISP_FLAG_LARGEST_NEEDED
 // Intended to be used with ADT/BitmaskEnum.h.
 // NOTE: Always must be equal to largest flag, check this when adding new flags.
-HANDLE_DISP_FLAG((1 << 8), Largest)
+HANDLE_DISP_FLAG((1 << 9), Largest)
 #undef DISP_FLAG_LARGEST_NEEDED
 #endif
 
 #undef HANDLE_DI_FLAG
 #undef HANDLE_DISP_FLAG

llvm/include/llvm/IR/DebugInfoMetadata.h

public:
   bool isPrototyped() const { return getFlags() & FlagPrototyped; }
   bool areAllCallsDescribed() const {
     return getFlags() & FlagAllCallsDescribed;
   }
   bool isPure() const { return getSPFlags() & SPFlagPure; }
   bool isElemental() const { return getSPFlags() & SPFlagElemental; }
   bool isRecursive() const { return getSPFlags() & SPFlagRecursive; }
 
+  /// Check if this is deleted member function.
+  ///
+  /// Return true if this subprogram is a C++11 special
+  /// member function declared deleted.
+  bool isDeleted() const { return getSPFlags() & SPFlagDeleted; }
+
   /// Check if this is reference-qualified.
   ///
   /// Return true if this subprogram is a C++11 reference-qualified non-static
   /// member function (void foo() &).
   bool isLValueReference() const { return getFlags() & FlagLValueReference; }
 
   /// Check if this is rvalue-reference-qualified.
   ///

llvm/lib/BinaryFormat/Dwarf.cpp

StringRef llvm::dwarf::AccessibilityString(unsigned Access) {
   case DW_ACCESS_protected:
     return "DW_ACCESS_protected";
   case DW_ACCESS_private:
     return "DW_ACCESS_private";
   }
   return StringRef();
 }
 
+StringRef llvm::dwarf::DefaultedMemberString(unsigned DefaultedEncodings) {
+  switch (DefaultedEncodings) {
+  // Defaulted Member Encodings codes
+  case DW_DEFAULTED_no:
+    return "DW_DEFAULTED_no";
+  case DW_DEFAULTED_in_class:
+    return "DW_DEFAULTED_in_class";
+  case DW_DEFAULTED_out_of_class:
+    return "DW_DEFAULTED_out_of_class";
+  }
+  return StringRef();
+}
+
 StringRef llvm::dwarf::VisibilityString(unsigned Visibility) {
   switch (Visibility) {
   case DW_VIS_local:
     return "DW_VIS_local";
   case DW_VIS_exported:
     return "DW_VIS_exported";
   case DW_VIS_qualified:
     return "DW_VIS_qualified";
StringRef llvm::dwarf::AttributeValueString(uint16_t Attr, unsigned Val) {
   case DW_AT_calling_convention:
     return ConventionString(Val);
   case DW_AT_inline:
     return InlineCodeString(Val);
   case DW_AT_ordering:
     return ArrayOrderString(Val);
   case DW_AT_APPLE_runtime_class:
     return LanguageString(Val);
+  case DW_AT_defaulted:
+    return DefaultedMemberString(Val);
   }
 
   return StringRef();
 }
 
 StringRef llvm::dwarf::AtomValueString(uint16_t Atom, unsigned Val) {
   switch (Atom) {
   case DW_ATOM_null:

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,
   if (SP->isMainSubprogram())
     addFlag(SPDie, dwarf::DW_AT_main_subprogram);
   if (SP->isPure())
     addFlag(SPDie, dwarf::DW_AT_pure);
   if (SP->isElemental())
     addFlag(SPDie, dwarf::DW_AT_elemental);
   if (SP->isRecursive())
     addFlag(SPDie, dwarf::DW_AT_recursive);
+
+  if (DD->getDwarfVersion() >= 5 && SP->isDeleted())
+    addFlag(SPDie, dwarf::DW_AT_deleted);
 }
 
 void DwarfUnit::constructSubrangeDIE(DIE &Buffer, const DISubrange *SR,
                                      DIE *IndexTy) {
   DIE &DW_Subrange = createAndAddDIE(dwarf::DW_TAG_subrange_type, Buffer);
   addDIEEntry(DW_Subrange, dwarf::DW_AT_type, *IndexTy);
 
   // The LowerBound value defines the lower bounds which is typically zero for

llvm/test/DebugInfo/X86/DW_AT_deleted.ll

+; RUN: llc < %s -filetype=obj -o %t
+; RUN: llvm-dwarfdump -v %t | FileCheck %s
+
+; C++ source to regenerate:
+; class deleted {
+; public:
+;   // Defaulted on purpose, so as to facilitate object creation
+;    deleted() = default;
+; 
+;   deleted(const deleted &) = delete;
+;   deleted &operator=(const deleted &) = delete;
+; 
+;   deleted(deleted &&) = delete;
+;   deleted &operator=(deleted &&) = delete;
+; 
+;   ~deleted() = default;
+; };
+; 
+; void foo() {
+;   deleted obj1;
+; }
+; $ clang++ -O0 -g -gdwarf-5 debug-info-deleted.cpp -c
+
+
+; CHECK: .debug_abbrev contents:
+
+; CHECK: [7] DW_TAG_subprogram   DW_CHILDREN_yes
+; CHECK: DW_AT_deleted   DW_FORM_flag_present
+; CHECK: [9] DW_TAG_subprogram   DW_CHILDREN_yes
+; CHECK: DW_AT_deleted   DW_FORM_flag_present
+
+; CHECK: .debug_info contents:
+
+; CHECK: DW_TAG_subprogram [7]
+; CHECK-NEXT: DW_AT_name [DW_FORM_strx1]    (indexed (00000006) string = "deleted") 
+; CHECK:  DW_AT_deleted [DW_FORM_flag_present]  (true)
+
+; CHECK: DW_TAG_subprogram [9]
+; CHECK-NEXT: DW_AT_linkage_name [DW_FORM_strx1]    (indexed (00000007) string = "_ZN7deletedaSERKS_") 
+; CHECK:  DW_AT_deleted [DW_FORM_flag_present]  (true)
+
+; CHECK: DW_TAG_subprogram [7]
+; CHECK-NEXT: DW_AT_name [DW_FORM_strx1]    (indexed (00000006) string = "deleted") 
+; CHECK:  DW_AT_deleted [DW_FORM_flag_present]  (true)
+
+; CHECK: DW_TAG_subprogram [9]
+; CHECK-NEXT: DW_AT_linkage_name [DW_FORM_strx1]    (indexed (00000009) string = "_ZN7deletedaSEOS_")
+; CHECK-NEXT: DW_AT_name [DW_FORM_strx1]    (indexed (00000008) string = "operator=")
+; CHECK:  DW_AT_deleted [DW_FORM_flag_present]  (true)
+
+; ModuleID = 'debug-info-deleted.cpp'
+source_filename = "debug-info-deleted.cpp"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%class.deleted = type { i8 }
+
+; Function Attrs: noinline nounwind optnone uwtable
+define dso_local void @_Z3foov() #0 !dbg !7 {
+  %1 = alloca %class.deleted, align 1
+  call void @llvm.dbg.declare(metadata %class.deleted* %1, metadata !10, metadata !DIExpression()), !dbg !34
+  ret void, !dbg !35
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { noinline nounwind optnone uwtable }
+attributes #1 = { nounwind readnone speculatable willreturn }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0 (https://github.com/llvm/llvm-project.git 715c47d5de9aa8860050992a7aaf27dca53f7f4a)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "debug-info-deleted.cpp", directory: "/home/sourabh/work/dwarf/c_c++/c++11", checksumkind: CSK_MD5, checksum: "49dc56907586479c64634558b060292d")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 10.0.0 (https://github.com/llvm/llvm-project.git 715c47d5de9aa8860050992a7aaf27dca53f7f4a)"}
+!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 14, type: !8, scopeLine: 14, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{null}
+!10 = !DILocalVariable(name: "obj1", scope: !7, file: !1, line: 15, type: !11)
+!11 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "deleted", file: !1, line: 1, size: 8, flags: DIFlagTypePassByReference, elements: !12, identifier: "_ZTS7deleted")
+!12 = !{!13, !17, !22, !26, !30, !33}
+!13 = !DISubprogram(name: "deleted", scope: !11, file: !1, line: 3, type: !14, scopeLine: 3, flags: DIFlagPublic | DIFlagPrototyped, spFlags: 0)
+!14 = !DISubroutineType(types: !15)
+!15 = !{null, !16}
+!16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!17 = !DISubprogram(name: "deleted", scope: !11, file: !1, line: 5, type: !18, scopeLine: 5, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted)
+!18 = !DISubroutineType(types: !19)
+!19 = !{null, !16, !20}
+!20 = !DIDerivedType(tag: DW_TAG_reference_type, baseType: !21, size: 64)
+!21 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !11)
+!22 = !DISubprogram(name: "operator=", linkageName: "_ZN7deletedaSERKS_", scope: !11, file: !1, line: 6, type: !23, scopeLine: 6, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted)
+!23 = !DISubroutineType(types: !24)
+!24 = !{!25, !16, !20}
+!25 = !DIDerivedType(tag: DW_TAG_reference_type, baseType: !11, size: 64)
+!26 = !DISubprogram(name: "deleted", scope: !11, file: !1, line: 8, type: !27, scopeLine: 8, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted)
+!27 = !DISubroutineType(types: !28)
+!28 = !{null, !16, !29}
+!29 = !DIDerivedType(tag: DW_TAG_rvalue_reference_type, baseType: !11, size: 64)
+!30 = !DISubprogram(name: "operator=", linkageName: "_ZN7deletedaSEOS_", scope: !11, file: !1, line: 9, type: !31, scopeLine: 9, flags: DIFlagPublic | DIFlagPrototyped, spFlags: DISPFlagDeleted)
+!31 = !DISubroutineType(types: !32)
+!32 = !{!25, !16, !29}
+!33 = !DISubprogram(name: "~deleted", scope: !11, file: !1, line: 11, type: !14, scopeLine: 11, flags: DIFlagPublic | DIFlagPrototyped, spFlags: 0)
+!34 = !DILocation(line: 15, column: 13, scope: !7)
+!35 = !DILocation(line: 16, column: 3, scope: !7)