[clang][DebugInfo] Emit DW_AT_deleted on any deleted member function

[Michael137]

Summary

Currently we emit DW_AT_deleted for deleted special-member
functions (i.e., ctors/dtors). However, in C++ one can mark any
member function as deleted. This patch expands the set of member
functions for which we emit DW_AT_deleted.

The DWARFv5 spec section 5.7.8 says:

<non-normative>
In C++, a member function may be declared as deleted. This prevents the compiler from
generating a default implementation of a special member function such as a constructor
or destructor, and can affect overload resolution when used on other member functions.
</non-normative>

If the member function entry has been declared as deleted, then that entry has a
DW_AT_deleted attribute.

Thus this change is conforming.

[Michael137]

• fix test comment

[aprantl]

Since a boolean flag is effectively free in DWARF as it can be stored in the abbreviations, this looks like a good change to me.

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 = [&](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;

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: "func", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped | DIFlagRValueReference, spFlags: DISPFlagDeleted
+// ATTR: DISubprogram(name: "bar", {{.*}}, flags: DIFlagPublic | DIFlagPrototyped | DIFlagStaticMember, 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;
 
+  void func() && = delete;
+  static int bar() = delete;
+
   ~deleted() = default;
 };
 
 void foo() {
   deleted obj1;
 }

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;
-; 
+;
+;   void func() && = delete;
+;   static void bar() = delete;
+; 
 ;   ~deleted() = default;
 ; };
 ; 
 ; void foo() {
 ;   deleted obj1;
 ; }
 ; $ clang++ -O0 -g -gdwarf-5 debug-info-deleted.cpp -c
 

 ; 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)
 
+; CHECK: DW_TAG_subprogram [10]
+; CHECK-NEXT: DW_AT_linkage_name [DW_FORM_strx1]    (indexed (0000000b) string = "_ZNO7deleted4funcEv")
+; CHECK-NEXT: DW_AT_name [DW_FORM_strx1]    (indexed (0000000c) string = "func")
+; CHECK:  DW_AT_deleted [DW_FORM_flag_present]  (true)
+
+; CHECK: DW_TAG_subprogram [11]
+; CHECK-NEXT: DW_AT_linkage_name [DW_FORM_strx1]    (indexed (0000000d) string = "_ZN7deleted3barEv")
+; CHECK-NEXT: DW_AT_name [DW_FORM_strx1]    (indexed (0000000e) string = "bar")
+; 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 ptr %1, metadata !10, metadata !DIExpression()), !dbg !34
-  ret void, !dbg !35
+  call void @llvm.dbg.declare(metadata ptr %1, metadata !10, metadata !DIExpression()), !dbg !39
+  ret void, !dbg !40
 }
 
 ; 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}
+!12 = !{!13, !17, !22, !26, !30, !33, !34, !36}
 !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)
+!34 = !DISubprogram(name: "func", linkageName: "_ZNO7deleted4funcEv", scope: !11, file: !1, line: 13, type: !35, scopeLine: 13, flags: DIFlagPublic | DIFlagPrototyped | DIFlagRValueReference, spFlags: DISPFlagDeleted)                                                                                                                                                                                                           
+!35 = !DISubroutineType(flags: DIFlagRValueReference, types: !15)                                                                                                                                                 
+!36 = !DISubprogram(name: "bar", linkageName: "_ZN7deleted3barEv", scope: !11, file: !1, line: 15, type: !37, scopeLine: 15, flags: DIFlagPublic | DIFlagPrototyped | DIFlagStaticMember, spFlags: DISPFlagDeleted)                                                                                                                                                                                                                 
+!37 = !DISubroutineType(types: !38)
+!38 = !{null}
+!39 = !DILocation(line: 15, column: 13, scope: !7)
+!40 = !DILocation(line: 16, column: 3, scope: !7)