[LLVM][DWARF] Create debug names entry for non-tu top level DIE (#121856)

When creating a Type Unit (TU), LLVM attempts to do so optimistically.
However, if this fails, it discards the TU state and creates the TU
within the Compilation Unit (CU). In such cases, an entry for the
top-level DIE is not created in the debug names table.
This can cause issues when running llvm-dwarfdump --debug-names
--verify, as the missing entry will result in verification failure.
To address this issue, this patch adds a call to the
updateAcceleratorTables when TU creation fails. This ensures that the
debug names table is updated correctly, even in cases where TU creation
fails.

Author: ayermolo

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -3789,6 +3789,7 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
       // they depend on addresses, throwing them out and rebuilding them.
       setCurrentDWARF5AccelTable(DWARF5AccelTableKind::CU);
       CU.constructTypeDIE(RefDie, cast<DICompositeType>(CTy));
+      CU.updateAcceleratorTables(CTy->getScope(), CTy, RefDie);
       return;
     }
 

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h

@@ -315,6 +315,11 @@ class DwarfUnit : public DIEUnit {
   /// Get context owner's DIE.
   DIE *createTypeDIE(const DICompositeType *Ty);
 
+  /// If this is a named finished type then include it in the list of types for
+  /// the accelerator tables.
+  void updateAcceleratorTables(const DIScope *Context, const DIType *Ty,
+                               const DIE &TyDIE);
+
 protected:
   ~DwarfUnit();
 
@@ -357,11 +362,6 @@ class DwarfUnit : public DIEUnit {
 
   virtual void finishNonUnitTypeDIE(DIE& D, const DICompositeType *CTy) = 0;
 
-  /// If this is a named finished type then include it in the list of types for
-  /// the accelerator tables.
-  void updateAcceleratorTables(const DIScope *Context, const DIType *Ty,
-                               const DIE &TyDIE);
-
   virtual bool isDwoUnit() const = 0;
   const MCSymbol *getCrossSectionRelativeBaseAddress() const override;
 

llvm/test/DebugInfo/X86/dwarf5-debug-names-addr-tu-to-non-tu.ll

@@ -0,0 +1,83 @@
+; RUN: llc -filetype=obj -O0 -generate-type-units -mtriple=x86_64-unknown-linux-gnu < %s \
+; RUN:     | llvm-dwarfdump -debug-info -debug-names - \
+; RUN:     | FileCheck %s
+
+;; Test that an entry in the debug names table gets created for a top level DIE when the creation of TU fails.
+
+;; clang++ -O0 main.cpp -gdwarf-5 -fdebug-types-section -gpubnames -S -emit-llvm -glldb -o main.ll
+;; int foo;
+;; namespace {
+;; struct t1 {};
+;; } // namespace
+;; template <int *> struct t2 {
+;;   t1 v1;
+;; };
+;; struct t3 {
+;;   t2<&foo> v1;
+;; };
+;; t3 v1;
+
+; CHECK: [[OFFSET:0x[0-9a-f]*]]:   DW_TAG_structure_type
+; CHECK: [[OFFSET1:0x[0-9a-f]*]]:   DW_TAG_structure_type
+
+; CHECK:        Bucket 0 [
+; CHECK-NEXT:    Name 1 {
+; CHECK-NEXT:      Hash: {{.+}}
+; CHECK-NEXT:      String: {{.+}} "t3"
+; CHECK-NEXT:      Entry @ {{.+}} {
+; CHECK-NEXT:        Abbrev: 0x1
+; CHECK-NEXT:        Tag: DW_TAG_structure_type
+; CHECK-NEXT:        DW_IDX_die_offset: [[OFFSET]]
+; CHECK-NEXT:        DW_IDX_parent: <parent not indexed>
+
+; CHECK:        Name 5 {
+; CHECK-NEXT:      Hash: {{.+}}
+; CHECK-NEXT:      String: {{.+}} "t2<&foo>"
+; CHECK-NEXT:      Entry @ 0xe1 {
+; CHECK-NEXT:        Abbrev: 0x1
+; CHECK-NEXT:        Tag: DW_TAG_structure_type
+; CHECK-NEXT:        DW_IDX_die_offset: [[OFFSET1]]
+; CHECK-NEXT:        DW_IDX_parent: <parent not indexed>
+
+; ModuleID = 'main.cpp'
+source_filename = "main.cpp"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.t3 = type { i8 }
+
+@foo = dso_local global i32 0, align 4, !dbg !0
+@v1 = dso_local global %struct.t3 zeroinitializer, align 1, !dbg !5
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!20, !21, !22, !23, !24, !25, !26}
+!llvm.ident = !{!27}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 1, type: !19, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 20.0.0git ([email protected]:llvm/llvm-project.git ba373096e8ac83a7136fc44bc4e71a7bc53417a6)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, sysroot: "/")
+!3 = !DIFile(filename: "main.cpp", directory: "/StructuredType", checksumkind: CSK_MD5, checksum: "f91f8d905197b1c0309da9526bc4776e")
+!4 = !{!0, !5}
+!5 = !DIGlobalVariableExpression(var: !6, expr: !DIExpression())
+!6 = distinct !DIGlobalVariable(name: "v1", scope: !2, file: !3, line: 11, type: !7, isLocal: false, isDefinition: true)
+!7 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t3", file: !3, line: 8, size: 8, flags: DIFlagTypePassByValue, elements: !8, identifier: "_ZTS2t3")
+!8 = !{!9}
+!9 = !DIDerivedType(tag: DW_TAG_member, name: "v1", scope: !7, file: !3, line: 9, baseType: !10, size: 8)
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t2<&foo>", file: !3, line: 5, size: 8, flags: DIFlagTypePassByValue, elements: !11, templateParams: !16, identifier: "_ZTS2t2IXadL_Z3fooEEE")
+!11 = !{!12}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "v1", scope: !10, file: !3, line: 6, baseType: !13, size: 8)
+!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t1", scope: !14, file: !3, line: 3, size: 8, flags: DIFlagTypePassByValue, elements: !15)
+!14 = !DINamespace(scope: null)
+!15 = !{}
+!16 = !{!17}
+!17 = !DITemplateValueParameter(type: !18, value: ptr @foo)
+!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !19, size: 64)
+!19 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!20 = !{i32 7, !"Dwarf Version", i32 5}
+!21 = !{i32 2, !"Debug Info Version", i32 3}
+!22 = !{i32 1, !"wchar_size", i32 4}
+!23 = !{i32 8, !"PIC Level", i32 2}
+!24 = !{i32 7, !"PIE Level", i32 2}
+!25 = !{i32 7, !"uwtable", i32 2}
+!26 = !{i32 7, !"frame-pointer", i32 2}
+!27 = !{!"clang version 20.0.0git ([email protected]:llvm/llvm-project.git ba373096e8ac83a7136fc44bc4e71a7bc53417a6)"}