[DebugInfo] Update DebugInfoFinder to take retainedNodes into account (llvm#140285)

Since https://reviews.llvm.org/D144004, DISubprogram's retainedNodes
field is used to track DIImportedEntities, in addition to local
variables and labels.

However, the corresponding update for DebugInfoFinder, to make it visit
DISubprogram's retainedNodes, was missing.
This is the fix for it.

This change is separated from
llvm#119001 to simplify it.

Author: dzhidzhoev

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)