Revert d91ed80 "[codeview] Reference types in type parent scopes"

This triggered asserts in the Chromium build, see https://crbug.com/1022729 for
details and reproducer.

> Without this change, when a nested tag type of any kind (enum, class,
> struct, union) is used as a variable type, it is emitted without
> emitting the parent type. In CodeView, parent types point to their inner
> types, and inner types do not point back to their parents. We already
> walk over all of the parent scopes to build the fully qualified name.
> This change simply requests their type indices as we go along to enusre
> they are all emitted.
>
> Fixes PR43905
>
> Reviewers: akhuang, amccarth
>
> Differential Revision: https://reviews.llvm.org/D69924

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp

@@ -303,19 +303,12 @@ static StringRef getPrettyScopeName(const DIScope *Scope) {
   return StringRef();
 }
 
-const DISubprogram *CodeViewDebug::collectParentScopeNames(
+static const DISubprogram *getQualifiedNameComponents(
     const DIScope *Scope, SmallVectorImpl<StringRef> &QualifiedNameComponents) {
   const DISubprogram *ClosestSubprogram = nullptr;
   while (Scope != nullptr) {
     if (ClosestSubprogram == nullptr)
       ClosestSubprogram = dyn_cast<DISubprogram>(Scope);
-
-    // If a type appears in a scope chain, make sure it gets emitted. The
-    // frontend will be responsible for deciding if this should be a forward
-    // declaration or a complete type.
-    if (const auto *Ty = dyn_cast<DIType>(Scope))
-      (void)getTypeIndex(Ty);
-
     StringRef ScopeName = getPrettyScopeName(Scope);
     if (!ScopeName.empty())
       QualifiedNameComponents.push_back(ScopeName);
@@ -324,9 +317,8 @@ const DISubprogram *CodeViewDebug::collectParentScopeNames(
   return ClosestSubprogram;
 }
 
-std::string
-CodeViewDebug::formatNestedName(ArrayRef<StringRef> QualifiedNameComponents,
-                                StringRef TypeName) {
+static std::string getQualifiedName(ArrayRef<StringRef> QualifiedNameComponents,
+                                    StringRef TypeName) {
   std::string FullyQualifiedName;
   for (StringRef QualifiedNameComponent :
        llvm::reverse(QualifiedNameComponents)) {
@@ -337,15 +329,10 @@ CodeViewDebug::formatNestedName(ArrayRef<StringRef> QualifiedNameComponents,
   return FullyQualifiedName;
 }
 
-std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Scope, StringRef Name) {
+static std::string getFullyQualifiedName(const DIScope *Scope, StringRef Name) {
   SmallVector<StringRef, 5> QualifiedNameComponents;
-  collectParentScopeNames(Scope, QualifiedNameComponents);
-  return formatNestedName(QualifiedNameComponents, Name);
-}
-
-std::string CodeViewDebug::getFullyQualifiedName(const DIScope *Ty) {
-  const DIScope *Scope = Ty->getScope();
-  return getFullyQualifiedName(Scope, getPrettyScopeName(Ty));
+  getQualifiedNameComponents(Scope, QualifiedNameComponents);
+  return getQualifiedName(QualifiedNameComponents, Name);
 }
 
 struct CodeViewDebug::TypeLoweringScope {
@@ -360,6 +347,11 @@ struct CodeViewDebug::TypeLoweringScope {
   CodeViewDebug &CVD;
 };
 
+static std::string getFullyQualifiedName(const DIScope *Ty) {
+  const DIScope *Scope = Ty->getScope();
+  return getFullyQualifiedName(Scope, getPrettyScopeName(Ty));
+}
+
 TypeIndex CodeViewDebug::getScopeIndex(const DIScope *Scope) {
   // No scope means global scope and that uses the zero index.
   if (!Scope || isa<DIFile>(Scope))
@@ -1476,12 +1468,12 @@ void CodeViewDebug::addToUDTs(const DIType *Ty) {
   if (!shouldEmitUdt(Ty))
     return;
 
-  SmallVector<StringRef, 5> ParentScopeNames;
+  SmallVector<StringRef, 5> QualifiedNameComponents;
   const DISubprogram *ClosestSubprogram =
-      collectParentScopeNames(Ty->getScope(), ParentScopeNames);
+      getQualifiedNameComponents(Ty->getScope(), QualifiedNameComponents);
 
   std::string FullyQualifiedName =
-      formatNestedName(ParentScopeNames, getPrettyScopeName(Ty));
+      getQualifiedName(QualifiedNameComponents, getPrettyScopeName(Ty));
 
   if (ClosestSubprogram == nullptr) {
     GlobalUDTs.emplace_back(std::move(FullyQualifiedName), Ty);

llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h

@@ -443,19 +443,6 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
                                                codeview::TypeIndex TI,
                                                const DIType *ClassTy = nullptr);
 
-  /// Collect the names of parent scopes, innermost to outermost. Return the
-  /// innermost subprogram scope if present. Ensure that parent type scopes are
-  /// inserted into the type table.
-  const DISubprogram *
-  collectParentScopeNames(const DIScope *Scope,
-                          SmallVectorImpl<StringRef> &ParentScopeNames);
-
-  std::string formatNestedName(ArrayRef<StringRef> ParentScopeNames,
-                               StringRef TypeName);
-
-  std::string getFullyQualifiedName(const DIScope *Scope, StringRef Name);
-  std::string getFullyQualifiedName(const DIScope *Scope);
-
   unsigned getPointerSizeInBytes();
 
 protected:

llvm/test/DebugInfo/COFF/global-constants.ll

@@ -36,7 +36,7 @@
 ; ASM-NEXT:   .asciz "S::TestConst2"        # Name
 ; ASM:        .short {{.*-.*}}              # Record length
 ; ASM:        .short 4359                   # Record kind: S_CONSTANT
-; ASM-NEXT:   .long 4113                    # Type
+; ASM-NEXT:   .long 4105                    # Type
 ; ASM-NEXT:   .byte 0x0a, 0x80, 0x40, 0x61  # Value
 ; ASM-NEXT:   .byte 0x07, 0x80, 0xff, 0xff
 ; ASM-NEXT:   .byte 0xff, 0xff
@@ -62,7 +62,7 @@
 ; OBJ-NEXT:       }
 ; OBJ-NEXT:       ConstantSym {
 ; OBJ-NEXT:         Kind: S_CONSTANT (0x1107)
-; OBJ-NEXT:         Type: TestEnum (0x1011)
+; OBJ-NEXT:         Type: TestEnum (0x1009)
 ; OBJ-NEXT:         Value: 18446744071562551616
 ; OBJ-NEXT:         Name: ENUM_B
 ; OBJ-NEXT:       }