[DebugInfo][DWARF] Emit DW_AT_abstract_origin for concrete/inlined DW_TAG_lexical_blocks (llvm#136205)

dzhidzhoev · web-flow · commit 1143a04f349c · 2025-04-24T19:44:18.000+02:00
During the discussion under llvm#119001, it was noticed that concrete DW_TAG_lexical_blocks should refer to corresponding abstract DW_TAG_lexical_blocks by having DW_AT_abstract_origin, to avoid ambiguity. This behavior is implemented in GCC (https://godbolt.org/z/Khrzdq1Wx), but not in LLVM. Fixes llvm#49297.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -782,6 +782,8 @@ DIE *DwarfCompileUnit::constructLexicalScopeDIE(LexicalScope *Scope) {
     assert(!LexicalBlockDIEs.count(DS) &&
            "Concrete out-of-line DIE for this scope exists!");
     LexicalBlockDIEs[DS] = ScopeDIE;
+  } else {
+    InlinedLocalScopeDIEs[DS].push_back(ScopeDIE);
   }
 
   attachRangesOrLowHighPC(*ScopeDIE, Scope->getRanges());
@@ -1491,6 +1493,19 @@ void DwarfCompileUnit::finishEntityDefinition(const DbgEntity *Entity) {
     getDwarfDebug().addAccelName(*this, CUNode->getNameTableKind(), Name, *Die);
 }
 
+void DwarfCompileUnit::attachLexicalScopesAbstractOrigins() {
+  auto AttachAO = [&](const DILocalScope *LS, DIE *ScopeDIE) {
+    if (auto *AbsLSDie = getAbstractScopeDIEs().lookup(LS))
+      addDIEEntry(*ScopeDIE, dwarf::DW_AT_abstract_origin, *AbsLSDie);
+  };
+
+  for (auto [LScope, ScopeDIE] : LexicalBlockDIEs)
+    AttachAO(LScope, ScopeDIE);
+  for (auto &[LScope, ScopeDIEs] : InlinedLocalScopeDIEs)
+    for (auto *ScopeDIE : ScopeDIEs)
+      AttachAO(LScope, ScopeDIE);
+}
+
 DbgEntity *DwarfCompileUnit::getExistingAbstractEntity(const DINode *Node) {
   auto &AbstractEntities = getAbstractEntities();
   auto I = AbstractEntities.find(Node);
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -82,6 +82,10 @@ class DwarfCompileUnit final : public DwarfUnit {
   // List of abstract local scopes (either DISubprogram or DILexicalBlock).
   DenseMap<const DILocalScope *, DIE *> AbstractLocalScopeDIEs;
 
+  // List of inlined lexical block scopes that belong to subprograms within this
+  // CU.
+  DenseMap<const DILocalScope *, SmallVector<DIE *, 2>> InlinedLocalScopeDIEs;
+
   DenseMap<const DINode *, std::unique_ptr<DbgEntity>> AbstractEntities;
 
   /// DWO ID for correlating skeleton and split units.
@@ -299,6 +303,7 @@ class DwarfCompileUnit final : public DwarfUnit {
 
   void finishSubprogramDefinition(const DISubprogram *SP);
   void finishEntityDefinition(const DbgEntity *Entity);
+  void attachLexicalScopesAbstractOrigins();
 
   /// Find abstract variable associated with Var.
   using InlinedEntity = DbgValueHistoryMap::InlinedEntity;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1262,6 +1262,7 @@ void DwarfDebug::finalizeModuleInfo() {
     auto &TheCU = *P.second;
     if (TheCU.getCUNode()->isDebugDirectivesOnly())
       continue;
+    TheCU.attachLexicalScopesAbstractOrigins();
     // Emit DW_AT_containing_type attribute to connect types with their
     // vtable holding type.
     TheCU.constructContainingTypeDIEs();
diff --git a/llvm/test/DebugInfo/Generic/inline-scopes.ll b/llvm/test/DebugInfo/Generic/inline-scopes.ll
@@ -20,16 +20,29 @@
 ; }
 
 ; Ensure that lexical_blocks within inlined_subroutines are preserved/emitted.
+; CHECK:      DW_TAG_subprogram
+; CHECK-NEXT: DW_AT_linkage_name ("_Z2f1v")
+; CHECK:      [[ADDR1:0x[0-9a-f]+]]: DW_TAG_lexical_block
+; CHECK:      DW_TAG_subprogram
+; CHECK-NEXT: DW_AT_linkage_name ("_Z2f2v")
+; CHECK:      [[ADDR2:0x[0-9a-f]+]]: DW_TAG_lexical_block
 ; CHECK: DW_TAG_inlined_subroutine
 ; CHECK-NOT: DW_TAG
 ; CHECK-NOT: NULL
-; CHECK: DW_TAG_lexical_block
+; CHECK:      DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_abstract_origin ([[ADDR1]]
 ; CHECK-NOT: DW_TAG
 ; CHECK-NOT: NULL
 ; CHECK: DW_TAG_variable
 ; Ensure that file changes don't interfere with creating inlined subroutines.
 ; (see the line directive inside 'f2' in thesource)
 ; CHECK: DW_TAG_inlined_subroutine
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_abstract_origin ([[ADDR2]]
+; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:   DW_TAG_variable
 ; CHECK-NOT: DW_TAG
 ; CHECK:     DW_AT_abstract_origin
diff --git a/llvm/test/DebugInfo/Generic/lexical-block-abstract-origin.ll b/llvm/test/DebugInfo/Generic/lexical-block-abstract-origin.ll
@@ -0,0 +1,56 @@
+; RUN: %llc_dwarf -filetype=obj -O0 %s -o - | llvm-dwarfdump -debug-info - | FileCheck %s
+
+; Check that DW_AT_abstract_origin is generated for concrete lexical block.
+
+; Generated from:
+; inline __attribute__((always_inline)) int foo(int x) {
+;   {
+;     int y = x + 5;
+;     return y - 10;
+;   }
+; }
+;
+; int bar(int x) {
+;   int y = foo(7);
+;   return y + 8;
+; }
+
+; CHECK:      DW_TAG_subprogram
+; CHECK-NEXT:   DW_AT_name  ("foo")
+; CHECK-NOT:    {{DW_TAG|NULL}}
+; CHECK:        [[LB:.*]]: DW_TAG_lexical_block
+
+; CHECK:        DW_TAG_inlined_subroutine
+; CHECK-NEXT:     DW_AT_abstract_origin {{.*}} "foo"
+; CHECK-NOT:      {{DW_TAG|NULL}}
+; CHECK:          DW_TAG_lexical_block
+; CHECK-NOT:        {{DW_TAG|NULL}}
+; CHECK:            DW_AT_abstract_origin {{.*}}[[LB]]
+
+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-macosx15.0.0"
+
+define i32 @bar() !dbg !9 {
+entry:
+  %y.i = alloca i32, align 4
+    #dbg_declare(ptr %y.i, !22, !DIExpression(), !24)
+  store i32 0, ptr %y.i, align 4, !dbg !24
+  %1 = load i32, ptr %y.i, align 4
+  ret i32 %1
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, emissionKind: FullDebug)
+!1 = !DIFile(filename: "test.c", directory: "")
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 8, type: !10, spFlags: DISPFlagDefinition, unit: !0)
+!10 = !DISubroutineType(types: !13)
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !{}
+!19 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !10, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !0)
+!21 = distinct !DILocation(line: 9, column: 11, scope: !9)
+!22 = !DILocalVariable(name: "y", scope: !23, file: !1, line: 3, type: !12)
+!23 = distinct !DILexicalBlock(scope: !19, file: !1, line: 2, column: 3)
+!24 = !DILocation(line: 3, column: 9, scope: !23, inlinedAt: !21)
diff --git a/llvm/test/DebugInfo/X86/lexical-block-file-inline.ll b/llvm/test/DebugInfo/X86/lexical-block-file-inline.ll
@@ -28,9 +28,11 @@
 ; CHECK:    DW_TAG_subprogram
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:      DW_AT_abstract_origin {{.*}} {[[Offset_bar:0x[0-9abcdef]+]]}
-; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK-NOT:  {{DW_TAG|NULL}}
 ; CHECK:      DW_TAG_lexical_block
-; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK-NOT:    {{DW_TAG|NULL}}
+; CHECK:        DW_AT_abstract_origin {{.*}}[[Offset_lb:0x[0-9a-f]+]]
+; CHECK-NOT:    {{DW_TAG|NULL}}
 ; CHECK:        DW_TAG_variable
 
 ;; Abstract "bar" function
@@ -40,7 +42,7 @@
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:      DW_AT_inline
 ; CHECK-NOT: {{DW_TAG|NULL}}
-; CHECK:      DW_TAG_lexical_block
+; CHECK:      [[Offset_lb]]: DW_TAG_lexical_block
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:        DW_TAG_variable
 ; CHECK-NOT: {{DW_TAG|NULL}}
@@ -56,8 +58,10 @@
 ; CHECK-NEXT:   DW_AT_abstract_origin {{.*}} {[[Offset_bar]]}
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:        DW_TAG_lexical_block
-; CHECK-NOT: {{DW_TAG|NULL}}
-; CHECK:          DW_TAG_variable
+; CHECK-NOT:      {{DW_TAG|NULL}}
+; CHECK:          DW_AT_abstract_origin {{.*}}[[Offset_lb]]
+; CHECK-NOT:    {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_variable
 
 ; Function Attrs: alwaysinline nounwind
 define i32 @_Z3barv() #0 !dbg !4 {
diff --git a/llvm/test/DebugInfo/X86/missing-abstract-variable.ll b/llvm/test/DebugInfo/X86/missing-abstract-variable.ll
@@ -37,7 +37,7 @@
 ; CHECK-NOT: DW_TAG
 ; CHECK:     DW_AT_name ("b")
 ; CHECK-NOT: {{DW_TAG|NULL}}
-; CHECK:       DW_TAG_lexical_block
+; CHECK:       [[LB_DECL:.*]]: DW_TAG_lexical_block
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:   DW_TAG_variable
 ; CHECK-NOT: DW_TAG
@@ -82,7 +82,9 @@
 
 ; CHECK-NOT: {{DW_TAG|NULL}}
 ; CHECK:     DW_TAG_lexical_block
-; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK-NOT:   {{DW_TAG|NULL}}
+; CHECK:       DW_AT_abstract_origin {{.*}}[[LB_DECL]]
+; CHECK-NOT:   {{DW_TAG|NULL}}
 ; CHECK:       DW_TAG_variable
 ; CHECK-NOT: DW_TAG
 ; CHECK:         DW_AT_abstract_origin {{.*}} "s"
