[DebugInfo] Emit linkage name into DWARF for types for Swift (llvm#112802)

Store Swift mangled names in DW_AT_linkage_name. The Swift compiler
emits only the type mangled name in debug information, and LLDB uses
those mangled names as keys to look up size, alignment, fields, etc
from either reflection metadata or Swift modules.

Additionally, emit types linkage names for types into the accelerator
table if they exist and they're different from the display name.

Author: augusto2112

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -645,16 +645,23 @@ void DwarfUnit::updateAcceleratorTables(const DIScope *Context,
 
   // add temporary record for this type to be added later
 
-  bool IsImplementation = false;
+  unsigned Flags = 0;
   if (auto *CT = dyn_cast<DICompositeType>(Ty)) {
     // A runtime language of 0 actually means C/C++ and that any
     // non-negative value is some version of Objective-C/C++.
-    IsImplementation = CT->getRuntimeLang() == 0 || CT->isObjcClassComplete();
+    if (CT->getRuntimeLang() == 0 || CT->isObjcClassComplete())
+      Flags = dwarf::DW_FLAG_type_implementation;
   }
-  unsigned Flags = IsImplementation ? dwarf::DW_FLAG_type_implementation : 0;
+
   DD->addAccelType(*this, CUNode->getNameTableKind(), Ty->getName(), TyDIE,
                    Flags);
 
+  if (auto *CT = dyn_cast<DICompositeType>(Ty))
+    if (Ty->getName() != CT->getIdentifier() &&
+        CT->getRuntimeLang() == dwarf::DW_LANG_Swift)
+      DD->addAccelType(*this, CUNode->getNameTableKind(), CT->getIdentifier(),
+                       TyDIE, Flags);
+
   addGlobalType(Ty, TyDIE, Context);
 }
 
@@ -1042,6 +1049,10 @@ void DwarfUnit::constructTypeDIE(DIE &Buffer, const DICompositeType *CTy) {
   if (!Name.empty())
     addString(Buffer, dwarf::DW_AT_name, Name);
 
+  // For Swift, mangled names are put into DW_AT_linkage_name.
+  if (CTy->getRuntimeLang() == dwarf::DW_LANG_Swift && CTy->getRawIdentifier())
+    addString(Buffer, dwarf::DW_AT_linkage_name, CTy->getIdentifier());
+
   addAnnotation(Buffer, CTy->getAnnotations());
 
   if (Tag == dwarf::DW_TAG_enumeration_type ||

llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp

@@ -1837,10 +1837,8 @@ DIE *DWARFLinker::DIECloner::cloneDIE(const DWARFDie &InputDIE,
     Unit.addNamespaceAccelerator(Die, AttrInfo.Name);
   } else if (Tag == dwarf::DW_TAG_imported_declaration && AttrInfo.Name) {
     Unit.addNamespaceAccelerator(Die, AttrInfo.Name);
-  } else if (isTypeTag(Tag) && !AttrInfo.IsDeclaration &&
-             getDIENames(InputDIE, AttrInfo, DebugStrPool) && AttrInfo.Name &&
-             AttrInfo.Name.getString()[0]) {
-    uint32_t Hash = hashFullyQualifiedName(InputDIE, Unit, File);
+  } else if (isTypeTag(Tag) && !AttrInfo.IsDeclaration) {
+    bool Success = getDIENames(InputDIE, AttrInfo, DebugStrPool);
     uint64_t RuntimeLang =
         dwarf::toUnsigned(InputDIE.find(dwarf::DW_AT_APPLE_runtime_class))
             .value_or(0);
@@ -1849,8 +1847,21 @@ DIE *DWARFLinker::DIECloner::cloneDIE(const DWARFDie &InputDIE,
          RuntimeLang == dwarf::DW_LANG_ObjC_plus_plus) &&
         dwarf::toUnsigned(InputDIE.find(dwarf::DW_AT_APPLE_objc_complete_type))
             .value_or(0);
-    Unit.addTypeAccelerator(Die, AttrInfo.Name, ObjCClassIsImplementation,
-                            Hash);
+    if (Success && AttrInfo.Name && !AttrInfo.Name.getString().empty()) {
+      uint32_t Hash = hashFullyQualifiedName(InputDIE, Unit, File);
+      Unit.addTypeAccelerator(Die, AttrInfo.Name, ObjCClassIsImplementation,
+                              Hash);
+    }
+
+    // For Swift, mangled names are put into DW_AT_linkage_name.
+    if (Success && AttrInfo.MangledName &&
+        RuntimeLang == dwarf::DW_LANG_Swift &&
+        !AttrInfo.MangledName.getString().empty() &&
+        AttrInfo.MangledName != AttrInfo.Name) {
+      auto Hash = djbHash(AttrInfo.MangledName.getString().data());
+      Unit.addTypeAccelerator(Die, AttrInfo.MangledName,
+                              ObjCClassIsImplementation, Hash);
+    }
   }
 
   // Determine whether there are any children that we want to keep.

llvm/test/DebugInfo/Generic/debug-names-accel-table-types.ll

@@ -0,0 +1,55 @@
+; RUN: %llc_dwarf -debugger-tune=lldb -accel-tables=Dwarf -filetype=obj -o %t < %s
+; RUN: llvm-dwarfdump %t | FileCheck %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=SAME-NAME %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=DIFFERENT-NAME %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=UNIQUE-DIFFERENT-NAME %s
+; RUN: llvm-dwarfdump -debug-names -verify %t | FileCheck --check-prefix=VERIFY %s
+
+
+; CHECK: DW_TAG_structure_type
+; CHECK: DW_AT_name ("SameName")
+; CHECK: DW_AT_linkage_name ("SameName")
+
+; CHECK: DW_TAG_structure_type
+; CHECK: DW_AT_name ("DifferentName")
+; CHECK: DW_AT_linkage_name ("UniqueDifferentName")
+
+; The name count should be 5 (the two variables, the two human readable names, one mangled name).
+; SAME-NAME: Name count: 5
+
+; The accelarator should only have one entry for the three following names.
+; SAME-NAME: "SameName" 
+; SAME-NAME-NOT: "SameName" 
+
+; DIFFERENT-NAME: "DifferentName"
+; DIFFERENT-NAME-NOT: "DifferentName"
+
+; UNIQUE-DIFFERENT-NAME: "UniqueDifferentName"
+; UNIQUE-DIFFERENT-NAME-NOT: "UniqueDifferentName"
+
+; Verification should succeed.
+; VERIFY: No errors.
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+
+@q = common global i8* null, align 8, !dbg !102
+@r = common global i8* null, align 8, !dbg !105
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!6, !7}
+
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, emissionKind: FullDebug, globals: !5)
+!3 = !DIFile(filename: "/tmp/p.c", directory: "/")
+!4 = !{}
+!5 = !{!102, !105}
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+
+; marking the types as Swift is necessary because we only emit the linkage names for Swift types.
+!11 = !DICompositeType(tag: DW_TAG_structure_type, name: "SameName", file: !3, size: 64, runtimeLang: DW_LANG_Swift, identifier: "SameName")
+!12 = !DICompositeType(tag: DW_TAG_structure_type, name: "DifferentName", file: !3, size: 64, runtimeLang: DW_LANG_Swift, identifier: "UniqueDifferentName")
+
+!102 = !DIGlobalVariableExpression(var: !103, expr: !DIExpression())
+!103 = distinct !DIGlobalVariable(name: "q", scope: !2, file: !3, line: 1, type: !11, isLocal: false, isDefinition: true)
+!104 = distinct !DIGlobalVariable(name: "r", scope: !2, file: !3, line: 1, type: !12, isLocal: false, isDefinition: true)
+!105 = !DIGlobalVariableExpression(var: !104, expr: !DIExpression())

llvm/test/tools/dsymutil/ARM/debug-names-accel-table-types.ll

@@ -0,0 +1,70 @@
+; RUN: %llc_dwarf -debugger-tune=lldb -accel-tables=Dwarf -filetype=obj -o %t < %s
+; RUN: dsymutil %t -o %t.dSYM
+; RUN: llvm-dwarfdump %t | FileCheck %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=SAME-NAME %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=DIFFERENT-NAME %s
+; RUN: llvm-dwarfdump -debug-names %t | FileCheck --check-prefix=UNIQUE-DIFFERENT-NAME %s
+; RUN: llvm-dwarfdump -debug-names -verify %t | FileCheck --check-prefix=VERIFY %s
+
+
+; CHECK: DW_TAG_structure_type
+; CHECK: DW_AT_name ("SameName")
+; CHECK: DW_AT_linkage_name ("SameName")
+
+; CHECK: DW_TAG_structure_type
+; CHECK: DW_AT_name ("DifferentName")
+; CHECK: DW_AT_linkage_name ("UniqueDifferentName")
+
+; The name count should be 5 (the two variables, "int", "SameName", "DifferentName", "UniqueDifferentName").
+; SAME-NAME: Name count: 6
+
+; The accelarator should only have one entry for the three following names.
+; SAME-NAME: "SameName" 
+; SAME-NAME-NOT: "SameName" 
+
+; DIFFERENT-NAME: "DifferentName"
+; DIFFERENT-NAME-NOT: "DifferentName"
+
+; UNIQUE-DIFFERENT-NAME: "UniqueDifferentName"
+; UNIQUE-DIFFERENT-NAME-NOT: "UniqueDifferentName"
+
+; Verification should succeed.
+; VERIFY: No errors.
+
+; ModuleID = 't.c'
+source_filename = "t.c"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "arm64-apple-macosx14.5.0"
+
+%struct.SameName = type { i32 }
+%struct.DifferentName = type { i32 }
+
+@q = global %struct.SameName zeroinitializer, align 4, !dbg !0
+@r = global %struct.DifferentName zeroinitializer, align 4, !dbg !5
+
+!llvm.module.flags = !{!14, !15, !16, !17, !18, !19, !20}
+!llvm.dbg.cu = !{!2}
+!llvm.ident = !{!21}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "q", scope: !2, file: !3, line: 9, type: !11, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C11, file: !3, producer: "clang version 1", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: Apple)
+!3 = !DIFile(filename: "t.c", directory: "/")
+!4 = !{!0, !5}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "r", scope: !2, file: !3, line: 10, type: !7, isLocal: false, isDefinition: true)
+!7 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "DifferentName", file: !3, line: 5, size: 32, runtimeLang: DW_LANG_Swift, identifier: "UniqueDifferentName", elements: !8)
+!8 = !{!9}
+!9 = !DIDerivedType(tag: DW_TAG_member, name: "i", scope: !7, file: !3, line: 6, baseType: !10, size: 32)
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "SameName", file: !3, line: 1, size: 32, runtimeLang: DW_LANG_Swift, identifier: "SameName", elements: !12)
+!12 = !{!13}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "i", scope: !11, file: !3, line: 2, baseType: !10, size: 32)
+!14 = !{i32 2, !"SDK Version", [2 x i32] [i32 14, i32 5]}
+!15 = !{i32 7, !"Dwarf Version", i32 4}
+!16 = !{i32 2, !"Debug Info Version", i32 3}
+!17 = !{i32 1, !"wchar_size", i32 4}
+!18 = !{i32 8, !"PIC Level", i32 2}
+!19 = !{i32 7, !"uwtable", i32 1}
+!20 = !{i32 7, !"frame-pointer", i32 1}
+!21 = !{!"clang version 1"}