[DebugInfo] Update DebugInfoFinder to take retainedNodes into account

llvm/include/llvm/IR/DebugInfo.h

@@ -110,7 +110,7 @@ class DebugInfoFinder {
   void processInstruction(const Module &M, const Instruction &I);
 
   /// Process a DILocalVariable.
-  void processVariable(const Module &M, const DILocalVariable *DVI);
+  void processVariable(DILocalVariable *DVI);
   /// Process debug info location.
   void processLocation(const Module &M, const DILocation *Loc);
   /// Process a DbgRecord (e.g, treat a DbgVariableRecord like a
@@ -127,6 +127,7 @@ class DebugInfoFinder {
   void processCompileUnit(DICompileUnit *CU);
   void processScope(DIScope *Scope);
   void processType(DIType *DT);
+  void processImportedEntity(DIImportedEntity *Import);
   bool addCompileUnit(DICompileUnit *CU);
   bool addGlobalVariable(DIGlobalVariableExpression *DIG);
   bool addScope(DIScope *Scope);

llvm/lib/IR/DebugInfo.cpp

@@ -241,23 +241,14 @@ void DebugInfoFinder::processCompileUnit(DICompileUnit *CU) {
       processType(T);
     else
       processSubprogram(cast<DISubprogram>(RT));
-  for (auto *Import : CU->getImportedEntities()) {
-    auto *Entity = Import->getEntity();
-    if (auto *T = dyn_cast<DIType>(Entity))
-      processType(T);
-    else if (auto *SP = dyn_cast<DISubprogram>(Entity))
-      processSubprogram(SP);
-    else if (auto *NS = dyn_cast<DINamespace>(Entity))
-      processScope(NS->getScope());
-    else if (auto *M = dyn_cast<DIModule>(Entity))
-      processScope(M->getScope());
-  }
+  for (auto *Import : CU->getImportedEntities())
+    processImportedEntity(Import);
 }
 
 void DebugInfoFinder::processInstruction(const Module &M,
                                          const Instruction &I) {
   if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(&I))
-    processVariable(M, DVI->getVariable());
+    processVariable(DVI->getVariable());
 
   if (auto DbgLoc = I.getDebugLoc())
     processLocation(M, DbgLoc.get());
@@ -275,7 +266,7 @@ void DebugInfoFinder::processLocation(const Module &M, const DILocation *Loc) {
 
 void DebugInfoFinder::processDbgRecord(const Module &M, const DbgRecord &DR) {
   if (const DbgVariableRecord *DVR = dyn_cast<const DbgVariableRecord>(&DR))
-    processVariable(M, DVR->getVariable());
+    processVariable(DVR->getVariable());
   processLocation(M, DR.getDebugLoc().get());
 }
 
@@ -303,6 +294,18 @@ void DebugInfoFinder::processType(DIType *DT) {
   }
 }
 
+void DebugInfoFinder::processImportedEntity(DIImportedEntity *Import) {
+  auto *Entity = Import->getEntity();
+  if (auto *T = dyn_cast<DIType>(Entity))
+    processType(T);
+  else if (auto *SP = dyn_cast<DISubprogram>(Entity))
+    processSubprogram(SP);
+  else if (auto *NS = dyn_cast<DINamespace>(Entity))
+    processScope(NS->getScope());
+  else if (auto *M = dyn_cast<DIModule>(Entity))
+    processScope(M->getScope());
+}
+
 void DebugInfoFinder::processScope(DIScope *Scope) {
   if (!Scope)
     return;
@@ -350,10 +353,16 @@ void DebugInfoFinder::processSubprogram(DISubprogram *SP) {
       processType(TVal->getType());
     }
   }
+
+  for (auto *N : SP->getRetainedNodes()) {
+    if (auto *Var = dyn_cast_or_null<DILocalVariable>(N))
+      processVariable(Var);
+    else if (auto *Import = dyn_cast_or_null<DIImportedEntity>(N))
+      processImportedEntity(Import);
+  }
 }
 
-void DebugInfoFinder::processVariable(const Module &M,
-                                      const DILocalVariable *DV) {
+void DebugInfoFinder::processVariable(DILocalVariable *DV) {
   if (!NodesSeen.insert(DV).second)
     return;
   processScope(DV->getScope());

llvm/test/DebugInfo/Generic/debuginfofinder-retained-nodes.ll

@@ -0,0 +1,42 @@
+; RUN: opt -passes='print<module-debuginfo>' -disable-output 2>&1 < %s \
+; RUN:   | FileCheck %s
+
+; This is to track DebugInfoFinder's ability to find the debug info metadata,
+; in particular, properly visit DISubprogram's retainedNodes.
+
+; CHECK: Compile unit: DW_LANG_C_plus_plus from /somewhere/source.cpp
+; CHECK: Subprogram: foo from /somewhere/source.cpp:1 ('_Z3foov')
+; CHECK: Subprogram: bar from /somewhere/source.cpp:5
+; CHECK: Subprogram: imported from /somewhere/source.cpp:3
+; CHECK: Type: T from /somewhere/source.cpp:2 DW_TAG_structure_type
+
+%struct.T = type { i32 }
+
+; Function Attrs: mustprogress noinline nounwind optnone ssp uwtable(sync)
+define noundef i32 @_Z3foov() !dbg !7 {
+entry:
+  ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 21.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "source.cpp", directory: "/somewhere")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!6 = !{!"clang version 21.0.0git"}
+!7 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 1, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !8)
+!8 = !{!9, !15}
+!9 = !DILocalVariable(name: "v", scope: !7, file: !1, line: 8, type: !10)
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "T", scope: !7, file: !1, line: 2, size: 32, flags: DIFlagTypePassByValue, elements: !11)
+!11 = !{!12, !14}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !10, file: !1, line: 3, baseType: !13, size: 32)
+!13 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!14 = !DISubprogram(name: "bar", scope: !10, file: !1, line: 5, scopeLine: 5, flags: DIFlagPrototyped | DIFlagStaticMember, spFlags: DISPFlagLocalToUnit)
+!15 = !DIImportedEntity(tag: DW_TAG_imported_declaration, scope: !7, entity: !16, file: !1, line: 7)
+!16 = distinct !DISubprogram(name: "imported", scope: !17, file: !1, line: 3, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0)
+!17 = !DINamespace(name: "ns", scope: null)