Address user feedback.

Author: clayborg

lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp

@@ -70,7 +70,7 @@ DebugNamesDWARFIndex::GetForeignTypeUnit(const DebugNames::Entry &entry) const {
   // file from it and get the type unit by signature from there. If we find
   // the type unit in the .dwo file, we don't need to check that the
   // DW_AT_dwo_name matches because each .dwo file can have its own type unit.
-  std::optional<uint64_t> cu_offset = entry.getForeignTUSkeletonCUOffset();
+  std::optional<uint64_t> cu_offset = entry.getRelatedCUOffset();
   if (!cu_offset)
     return nullptr; // Return NULL, this is a type unit, but couldn't find it.
 

llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h

@@ -72,24 +72,6 @@ class DWARFAcceleratorTable {
       return std::nullopt;
     }
 
-    // Returns the the CU offset for a foreign TU.
-    //
-    // Entries that represent foreign type units can have both a
-    // DW_IDX_compile_unit and a DW_IDX_type_unit. In this case the
-    // DW_IDX_compile_unit represents the skeleton CU offset for the .dwo file
-    // that matches this foreign type unit entry. The type unit will have a
-    // DW_AT_dwo_name attribute that must match the attribute in the skeleton
-    // CU. This function is needed be because the getCUOffset() method will
-    // return the first CU if there is no DW_IDX_compile_unit attribute in this
-    // entry, and it won't return a value CU offset if there is a
-    // DW_IDX_type_unit. But this function will return std::nullopt if there is
-    // no DW_IDX_compile_unit attribute or if this doesn't represent a foreign
-    // type unit.
-    virtual std::optional<uint64_t> getForeignTUSkeletonCUOffset() const {
-      // Default return for accelerator tables that don't support type units.
-      return std::nullopt;
-    }
-
     /// Returns the Tag of the Debug Info Entry associated with this
     /// Accelerator Entry or std::nullopt if the Tag is not recorded in this
     /// Accelerator Entry.
@@ -463,10 +445,13 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
     std::optional<uint64_t> getCUOffset() const override;
     std::optional<uint64_t> getLocalTUOffset() const override;
     std::optional<uint64_t> getForeignTUTypeSignature() const override;
-    std::optional<uint64_t> getForeignTUSkeletonCUOffset() const override;
-
     std::optional<dwarf::Tag> getTag() const override { return tag(); }
 
+    // Special function that will return the related CU offset needed type 
+    // units. This gets used to find the .dwo file that originated the entries
+    // for a given type unit.
+    std::optional<uint64_t> getRelatedCUOffset() const;
+
     /// Returns the Index into the Compilation Unit list of the owning Name
     /// Index or std::nullopt if this Accelerator Entry does not have an
     /// associated Compilation Unit. It is up to the user to verify that the
@@ -478,6 +463,11 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
     /// attribute.
     std::optional<uint64_t> getCUIndex() const;
 
+    /// Similar functionality to getCUIndex() but without the DW_IDX_type_unit
+    /// restriction. This allows us to get the associated a compilation unit
+    /// index for an entry that is a type unit.
+    std::optional<uint64_t> getRelatedCUIndex() const;
+
     /// Returns the Index into the Local Type Unit list of the owning Name
     /// Index or std::nullopt if this Accelerator Entry does not have an
     /// associated Type Unit. It is up to the user to verify that the

llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp

@@ -630,26 +630,40 @@ std::optional<uint64_t> DWARFDebugNames::Entry::getDIEUnitOffset() const {
   return std::nullopt;
 }
 
-std::optional<uint64_t> DWARFDebugNames::Entry::getCUIndex() const {
+std::optional<uint64_t> DWARFDebugNames::Entry::getRelatedCUIndex() const {
+  // Return the DW_IDX_compile_unit attribute value if it is specified.
   if (std::optional<DWARFFormValue> Off = lookup(dwarf::DW_IDX_compile_unit))
     return Off->getAsUnsignedConstant();
   // In a per-CU index, the entries without a DW_IDX_compile_unit attribute
-  // implicitly refer to the single CU, but only if we don't have a
-  // DW_IDX_type_unit.
-  if (lookup(dwarf::DW_IDX_type_unit).has_value())
-    return std::nullopt;
+  // implicitly refer to the single CU. 
   if (NameIdx->getCUCount() == 1)
     return 0;
   return std::nullopt;
 }
 
+std::optional<uint64_t> DWARFDebugNames::Entry::getCUIndex() const {
+  // Return the DW_IDX_compile_unit attribute value but only if we don't have a
+  // DW_IDX_type_unit attribute. Use Entry::getRelatedCUIndex() to get the
+  // associated CU index if this behaviour is not desired.
+  if (lookup(dwarf::DW_IDX_type_unit).has_value())
+    return std::nullopt;
+  return getRelatedCUIndex();
+}
+
 std::optional<uint64_t> DWARFDebugNames::Entry::getCUOffset() const {
   std::optional<uint64_t> Index = getCUIndex();
   if (!Index || *Index >= NameIdx->getCUCount())
     return std::nullopt;
   return NameIdx->getCUOffset(*Index);
 }
 
+std::optional<uint64_t> DWARFDebugNames::Entry::getRelatedCUOffset() const {
+  std::optional<uint64_t> Index = getRelatedCUIndex();
+  if (!Index || *Index >= NameIdx->getCUCount())
+    return std::nullopt;
+  return NameIdx->getCUOffset(*Index);
+}
+
 std::optional<uint64_t> DWARFDebugNames::Entry::getLocalTUOffset() const {
   std::optional<uint64_t> Index = getLocalTUIndex();
   if (!Index || *Index >= NameIdx->getLocalTUCount())
@@ -670,29 +684,6 @@ DWARFDebugNames::Entry::getForeignTUTypeSignature() const {
   return NameIdx->getForeignTUSignature(ForeignTUIndex);
 }
 
-std::optional<uint64_t>
-DWARFDebugNames::Entry::getForeignTUSkeletonCUOffset() const {
-  // Must have a DW_IDX_type_unit and it must be a foreign type unit.
-  if (!getForeignTUTypeSignature())
-    return std::nullopt;
-  // Lookup the DW_IDX_compile_unit and make sure we have one, if we don't
-  // we don't default to returning the first compile unit like getCUOffset().
-  std::optional<uint64_t> CUIndex;
-  std::optional<DWARFFormValue> Off = lookup(dwarf::DW_IDX_compile_unit);
-  if (Off) {
-    CUIndex = Off->getAsUnsignedConstant();
-  } else {
-    // Check if there is only 1 CU and return that. Most .o files generate one
-    // .debug_names table per source file where there is 1 CU and many TUs.
-    if (NameIdx->getCUCount() == 1)
-      CUIndex = 0;
-  }
-  // Extract the CU index and return the right CU offset.
-  if (CUIndex && *CUIndex < NameIdx->getCUCount())
-    return NameIdx->getCUOffset(*CUIndex);
-  return std::nullopt;
-}
-
 std::optional<uint64_t> DWARFDebugNames::Entry::getLocalTUIndex() const {
   if (std::optional<DWARFFormValue> Off = lookup(dwarf::DW_IDX_type_unit))
     return Off->getAsUnsignedConstant();