[codeview] Look through typedefs in getCompleteTypeIndex

[rnk]

Summary

Any time a symbol record, whether it's S_UDT, S_LOCAL, or S_[GL]DATA32,
references a record type, it should use the complete type index, even if
there's a typedef in the way.

Fixes PR39853.

[aganea]

Fixes PR39853.

The issue I was discussing with Zachary occurs when using cl-generated OBJs with LLD (we haven't deployed clang in production yet).
Shouldn't there be something in LLD to completly fix PR39853? Microsoft seems to be doing a post-merge pass to resolve forward-declared UDTs, see here and here.

llvm/test/DebugInfo/COFF/udts-complete.ll

13

== 4?

[rnk]

In D55236#1318552, @aganea wrote:

Fixes PR39853.

The issue I was discussing with Zachary occurs when using cl-generated OBJs with LLD (we haven't deployed clang in production yet).
Shouldn't there be something in LLD to completly fix PR39853? Microsoft seems to be doing a post-merge pass to resolve forward-declared UDTs, see here and here.

I guess it depends how we want to scope the PR. I'll just say this fixes the compiler side of it, i.e. makes clang generate the same debug info as msvc.

llvm/test/DebugInfo/COFF/udts-complete.ll

13

Heh, I think I actually commented that out and compiled with -fstandalone-debug, which you can see below from emissionKind: FullDebug. I'll fix it.

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

 
 TypeIndex CodeViewDebug::getCompleteTypeIndex(DITypeRef TypeRef) {
   const DIType *Ty = TypeRef.resolve();
 
   // The null DIType is the void type. Don't try to hash it.
   if (!Ty)
     return TypeIndex::Void();
 
+  // Look through typedefs when getting the complete type index. Call
+  // getTypeIndex on the typdef to ensure that any UDTs are accumulated and are
+  // emitted only once.
+  if (Ty->getTag() == dwarf::DW_TAG_typedef)
+    (void)getTypeIndex(Ty);
+  while (Ty->getTag() == dwarf::DW_TAG_typedef)
+    Ty = cast<DIDerivedType>(Ty)->getBaseType().resolve();
+
   // If this is a non-record type, the complete type index is the same as the
   // normal type index. Just call getTypeIndex.
   switch (Ty->getTag()) {
   case dwarf::DW_TAG_class_type:
   case dwarf::DW_TAG_structure_type:
   case dwarf::DW_TAG_union_type:
     break;
   default:

llvm/test/DebugInfo/COFF/udts-complete.ll

+; RUN: llc -filetype=obj %s -o %t.obj
+; RUN: llvm-pdbutil dump -symbols -types %t.obj | FileCheck %s
+
+; Make sure that `gv`, `Bar`, and `Baz` all point to the complete type index of
+; Foo (0x1002), and not the forward declaration index (0x1000).
+
+; C++ source:
+; struct Foo {
+;   int x;
+; };
+; typedef Foo Bar;
+; typedef Bar Baz;
+; static_assert(sizeof(Foo) == 8, "");
+; Baz gv;
+
+; CHECK:                       Types (.debug$T)
+; CHECK-NEXT: ============================================================
+; CHECK: 0x1000 | LF_STRUCTURE [size = 36] `Foo`
+; CHECK:          unique name: `.?AUFoo@@`
+; CHECK:          vtable: <no type>, base list: <no type>, field list: <no type>
+; CHECK:          options: forward ref | has unique name, sizeof 0
+; CHECK: 0x1001 | LF_FIELDLIST [size = 16]
+; CHECK:          - LF_MEMBER [name = `x`, Type = 0x0074 (int), offset = 0, attrs = public]
+; CHECK: 0x1002 | LF_STRUCTURE [size = 36] `Foo`
+; CHECK:          unique name: `.?AUFoo@@`
+; CHECK:          vtable: <no type>, base list: <no type>, field list: 0x1001
+; CHECK:          options: has unique name, sizeof 4
+; CHECK: 0x1004 | LF_UDT_SRC_LINE [size = 16]
+; CHECK:          udt = 0x1002, file = 4099, line = 1
+
+; CHECK:                           Symbols
+; CHECK: ============================================================
+; CHECK:   Mod 0000 | `.debug$S`:
+; CHECK:        0 | S_GDATA32 [size = 17] `gv`
+; CHECK:            type = 0x1002 (Foo), addr = 0000:0000
+; CHECK:        0 | S_UDT [size = 12] `Bar`
+; CHECK:            original type = 0x1002
+; CHECK:        0 | S_UDT [size = 12] `Baz`
+; CHECK:            original type = 0x1002
+; CHECK:        0 | S_UDT [size = 12] `Foo`
+; CHECK:            original type = 0x1002
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.14.26433"
+
+%struct.Foo = type { i32 }
+
+@"?gv@@3UFoo@@A" = dso_local global %struct.Foo zeroinitializer, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!12, !13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "gv", linkageName: "?gv@@3UFoo@@A", scope: !2, file: !3, line: 7, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 8.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
+!3 = !DIFile(filename: "t.cpp", directory: "C:\5Csrc\5Cllvm-project\5Cbuild", checksumkind: CSK_MD5, checksum: "e21cd263d43db2ff55050be3e41e789f")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIDerivedType(tag: DW_TAG_typedef, name: "Baz", file: !3, line: 5, baseType: !7)
+!7 = !DIDerivedType(tag: DW_TAG_typedef, name: "Bar", file: !3, line: 4, baseType: !8)
+!8 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Foo", file: !3, line: 1, size: 32, flags: DIFlagTypePassByValue | DIFlagTrivial, elements: !9, identifier: ".?AUFoo@@")
+!9 = !{!10}
+!10 = !DIDerivedType(tag: DW_TAG_member, name: "x", scope: !8, file: !3, line: 2, baseType: !11, size: 32)
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !{i32 2, !"CodeView", i32 1}
+!13 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{i32 1, !"wchar_size", i32 2}
+!15 = !{i32 7, !"PIC Level", i32 2}
+!16 = !{!"clang version 8.0.0 "}