[LLDB][NativePDB] Resolve declaration for tag types (#152579)

Tag types like stucts or enums didn't have a declaration attached to
them. The source locations are present in the IPI stream in
`LF_UDT_MOD_SRC_LINE` records:

```
   0x101F | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1C63]
            udt = 0x1058, mod = 3, file = 1, line = 0
   0x2789 | LF_UDT_MOD_SRC_LINE [size = 18, hash = 0x1E5A]
            udt = 0x1253, mod = 35, file = 93, line = 17069
```

The file is an ID in the string table `/names`:

```
     ID | String
      1 | '\<unknown>'
     12 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\wingdi.h'
     93 | 'D:\a\_work\1\s\src\ExternalAPIs\WindowsSDKInc\c\Include\10.0.22621.0\um\winnt.h'
```

Here, we're not interested in `mod`. This would indicate which module
contributed the UDT.

I was looking at Rustc's PDB and found that it uses `<unknown>` for some
types, so I added a check for that.

This makes two DIA PDB shell tests to work with the native PDB plugin.

---------

Co-authored-by: Michael Buch <michaelbuch12@gmail.com>

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

@@ -644,8 +644,14 @@ SymbolFileNativePDB::CreateClassStructUnion(PdbTypeSymId type_id,
 
   std::string uname = GetUnqualifiedTypeName(record);
 
-  // FIXME: Search IPI stream for LF_UDT_MOD_SRC_LINE.
+  llvm::Expected maybeDecl = ResolveUdtDeclaration(type_id);
   Declaration decl;
+  if (maybeDecl)
+    decl = std::move(*maybeDecl);
+  else
+    LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), maybeDecl.takeError(),
+                   "Failed to resolve declaration for '{1}': {0}", uname);
+
   return MakeType(toOpaqueUid(type_id), ConstString(uname), size, nullptr,
                   LLDB_INVALID_UID, Type::eEncodingIsUID, decl, ct,
                   Type::ResolveState::Forward);
@@ -668,7 +674,14 @@ lldb::TypeSP SymbolFileNativePDB::CreateTagType(PdbTypeSymId type_id,
                                                 CompilerType ct) {
   std::string uname = GetUnqualifiedTypeName(er);
 
+  llvm::Expected maybeDecl = ResolveUdtDeclaration(type_id);
   Declaration decl;
+  if (maybeDecl)
+    decl = std::move(*maybeDecl);
+  else
+    LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), maybeDecl.takeError(),
+                   "Failed to resolve declaration for '{1}': {0}", uname);
+
   TypeSP underlying_type = GetOrCreateType(er.UnderlyingType);
 
   return MakeType(
@@ -2556,3 +2569,70 @@ SymbolFileNativePDB::GetContextForType(TypeIndex ti) {
   }
   return ctx;
 }
+
+void SymbolFileNativePDB::CacheUdtDeclarations() {
+  for (CVType cvt : m_index->ipi().typeArray()) {
+    switch (cvt.kind()) {
+    case LF_UDT_SRC_LINE: {
+      UdtSourceLineRecord udt_src;
+      llvm::cantFail(TypeDeserializer::deserializeAs(cvt, udt_src));
+      m_udt_declarations.try_emplace(
+          udt_src.UDT, UdtDeclaration{/*FileNameIndex=*/udt_src.SourceFile,
+                                      /*IsIpiIndex=*/true,
+                                      /*Line=*/udt_src.LineNumber});
+    } break;
+    case LF_UDT_MOD_SRC_LINE: {
+      UdtModSourceLineRecord udt_mod_src;
+      llvm::cantFail(TypeDeserializer::deserializeAs(cvt, udt_mod_src));
+      // Some types might be contributed by multiple modules. We assume that
+      // they all point to the same file and line because we can only provide
+      // one location.
+      m_udt_declarations.try_emplace(
+          udt_mod_src.UDT,
+          UdtDeclaration{/*FileNameIndex=*/udt_mod_src.SourceFile,
+                         /*IsIpiIndex=*/false,
+                         /*Line=*/udt_mod_src.LineNumber});
+    } break;
+    default:
+      break;
+    }
+  }
+}
+
+llvm::Expected<Declaration>
+SymbolFileNativePDB::ResolveUdtDeclaration(PdbTypeSymId type_id) {
+  std::call_once(m_cached_udt_declarations, [this] { CacheUdtDeclarations(); });
+
+  auto it = m_udt_declarations.find(type_id.index);
+  if (it == m_udt_declarations.end())
+    return llvm::createStringError("No UDT declaration found");
+
+  llvm::StringRef file_name;
+  if (it->second.IsIpiIndex) {
+    CVType cvt = m_index->ipi().getType(it->second.FileNameIndex);
+    if (cvt.kind() != LF_STRING_ID)
+      return llvm::createStringError("File name was not a LF_STRING_ID");
+
+    StringIdRecord sid;
+    llvm::cantFail(TypeDeserializer::deserializeAs(cvt, sid));
+    file_name = sid.String;
+  } else {
+    // The file name index is an index into the string table
+    auto string_table = m_index->pdb().getStringTable();
+    if (!string_table)
+      return string_table.takeError();
+
+    llvm::Expected<llvm::StringRef> string =
+        string_table->getStringTable().getString(
+            it->second.FileNameIndex.getIndex());
+    if (!string)
+      return string.takeError();
+    file_name = *string;
+  }
+
+  // rustc sets the filename to "<unknown>" for some files
+  if (file_name == "\\<unknown>")
+    return Declaration();
+
+  return Declaration(FileSpec(file_name), it->second.Line);
+}

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h

@@ -262,6 +262,9 @@ private:
 
   void CacheFunctionNames();
 
+  void CacheUdtDeclarations();
+  llvm::Expected<Declaration> ResolveUdtDeclaration(PdbTypeSymId type_id);
+
   llvm::BumpPtrAllocator m_allocator;
 
   lldb::addr_t m_obj_load_address = 0;
@@ -283,6 +286,18 @@ private:
   llvm::DenseMap<llvm::codeview::TypeIndex, llvm::codeview::TypeIndex>
       m_parent_types;
 
+  struct UdtDeclaration {
+    /// This could either be an index into the `/names` section (string table,
+    /// LF_UDT_MOD_SRC_LINE) or, this could be an index into the IPI stream to a
+    /// LF_STRING_ID record (LF_UDT_SRC_LINE).
+    llvm::codeview::TypeIndex FileNameIndex;
+    bool IsIpiIndex;
+
+    uint32_t Line;
+  };
+  llvm::DenseMap<llvm::codeview::TypeIndex, UdtDeclaration> m_udt_declarations;
+  std::once_flag m_cached_udt_declarations;
+
   lldb_private::UniqueCStringMap<uint32_t> m_type_base_names;
 
   /// mangled name/full function name -> Global ID(s)

lldb/test/Shell/SymbolFile/NativePDB/unknown-udt-decl.ll

@@ -0,0 +1,56 @@
+; Test that the declaration for UDTs won't be "<unknown>" or "\<unknown>".
+; Rustc sets the location of some builtin types to this string.
+
+; REQUIRES: system-windows
+; RUN: %build --compiler=clang-cl --nodefaultlib -o %t.exe -- %s
+; RUN: lldb-test symbols %t.exe | FileCheck %s
+
+; there shouldn't be a declaration (would be between size and compiler_type)
+; CHECK: Type{{.*}} , name = "Foo", size = 1, compiler_type = {{.*}} struct Foo {
+
+; This is edited output from clang  simulates rustc behavior (see !17)
+; Source:
+; struct Foo {};
+;
+; int main() { Foo f; }
+
+
+; ModuleID = 'main.cpp'
+source_filename = "main.cpp"
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.44.35207"
+
+%struct.Foo = type { i8 }
+
+; Function Attrs: mustprogress noinline norecurse nounwind optnone uwtable
+define dso_local noundef i32 @main() #0 !dbg !9 {
+  %1 = alloca %struct.Foo, align 1
+    #dbg_declare(ptr %1, !14, !DIExpression(), !16)
+  ret i32 0, !dbg !16
+}
+
+attributes #0 = { mustprogress noinline norecurse nounwind optnone uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5, !6, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 20.1.6", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "main.cpp", directory: "F:\\Dev\\rust-dbg-test", checksumkind: CSK_MD5, checksum: "b8942260dadf9ec35328889f05afb954")
+!2 = !{i32 2, !"CodeView", i32 1}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 2}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!6 = !{i32 7, !"uwtable", i32 2}
+!7 = !{i32 1, !"MaxTLSAlign", i32 65536}
+!8 = !{!"clang version 20.1.6"}
+!9 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 3, type: !10, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !13)
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !{}
+!14 = !DILocalVariable(name: "f", scope: !9, file: !1, line: 3, type: !15)
+!15 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Foo", file: !17, line: 1, size: 8, flags: DIFlagTypePassByValue, elements: !13, identifier: ".?AUFoo@@")
+!16 = !DILocation(line: 3, scope: !9)
+; This is how rustc emits some types
+!17 = !DIFile(filename: "<unknown>", directory: "")

lldb/test/Shell/SymbolFile/PDB/class-layout.test

@@ -12,9 +12,19 @@ RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=BASE %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=FRIEND %s
 RUN: lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=CLASS %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=UNION %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=STRUCT %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=COMPLEX %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=LIST %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=UNNAMED-STRUCT %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=BASE %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=FRIEND %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/ClassLayoutTest.cpp.exe | FileCheck --check-prefix=CLASS %s
 
 CHECK: Module [[MOD:.*]]
-CHECK: SymbolFile pdb ([[MOD]])
+CHECK: SymbolFile {{(native-)?}}pdb ([[MOD]])
 CHECK: {{^[0-9A-F]+}}:   CompileUnit{{[{]0x[0-9a-f]+[}]}}, language = "c++", file = '{{.*}}\ClassLayoutTest.cpp'
 
 ENUM:  name = "Enum", size = 4,  decl = ClassLayoutTest.cpp:5

lldb/test/Shell/SymbolFile/PDB/enums-layout.test

@@ -7,6 +7,12 @@ RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=UCHAR-ENUM %s
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CLASS-ENUM %s
 RUN: lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=STRUCT-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CONST-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=EMPTY-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=UCHAR-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=CLASS-ENUM %s
+RUN: env LLDB_USE_NATIVE_PDB_READER=1 lldb-test symbols %t.dir/SimpleTypesTest.cpp.enums.exe | FileCheck --check-prefix=STRUCT-ENUM %s
 
 ; FIXME: PDB does not have information about scoped enumeration (Enum class) so the  
 ; compiler type used is the same as the one for unscoped enumeration.