[lldb/DWARF] Remove some dead code (#95127)

`GetDeclContextDIEs` and `DIEDeclContextsMatch` are unused (possibly
since we added support for simplified template names, but I haven't
checked). `GetDeclContextDIEs` is also very similar (but subtly
different) from `GetDeclContext` and `GetTypeLookupContext`.

I am keeping `GetParentDeclContextDIE` as that one still has some
callers, but I want to look into the possibility of merging it with at
least one of the functions mentioned above.

Author: labath

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

@@ -367,20 +367,6 @@ lldb_private::Type *DWARFDIE::ResolveTypeUID(const DWARFDIE &die) const {
   return nullptr;
 }
 
-std::vector<DWARFDIE> DWARFDIE::GetDeclContextDIEs() const {
-  if (!IsValid())
-    return {};
-
-  std::vector<DWARFDIE> result;
-  DWARFDIE parent = GetParentDeclContextDIE();
-  while (parent.IsValid() && parent.GetDIE() != GetDIE()) {
-    result.push_back(std::move(parent));
-    parent = parent.GetParentDeclContextDIE();
-  }
-
-  return result;
-}
-
 static void GetDeclContextImpl(DWARFDIE die,
                                llvm::SmallSet<lldb::user_id_t, 4> &seen,
                                std::vector<CompilerContext> &context) {

lldb/source/Plugins/SymbolFile/DWARF/DWARFDIE.h

@@ -69,9 +69,6 @@ class DWARFDIE : public DWARFBaseDIE {
   DWARFDIE
   GetParentDeclContextDIE() const;
 
-  // DeclContext related functions
-  std::vector<DWARFDIE> GetDeclContextDIEs() const;
-
   /// Return this DIE's decl context as it is needed to look up types
   /// in Clang modules. This context will include any modules or functions that
   /// the type is declared in so an exact module match can be efficiently made.

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

@@ -3039,95 +3039,6 @@ TypeSP SymbolFileDWARF::FindCompleteObjCDefinitionTypeForDIE(
   return type_sp;
 }
 
-// This function helps to ensure that the declaration contexts match for two
-// different DIEs. Often times debug information will refer to a forward
-// declaration of a type (the equivalent of "struct my_struct;". There will
-// often be a declaration of that type elsewhere that has the full definition.
-// When we go looking for the full type "my_struct", we will find one or more
-// matches in the accelerator tables and we will then need to make sure the
-// type was in the same declaration context as the original DIE. This function
-// can efficiently compare two DIEs and will return true when the declaration
-// context matches, and false when they don't.
-bool SymbolFileDWARF::DIEDeclContextsMatch(const DWARFDIE &die1,
-                                           const DWARFDIE &die2) {
-  if (die1 == die2)
-    return true;
-
-  std::vector<DWARFDIE> decl_ctx_1;
-  std::vector<DWARFDIE> decl_ctx_2;
-  // The declaration DIE stack is a stack of the declaration context DIEs all
-  // the way back to the compile unit. If a type "T" is declared inside a class
-  // "B", and class "B" is declared inside a class "A" and class "A" is in a
-  // namespace "lldb", and the namespace is in a compile unit, there will be a
-  // stack of DIEs:
-  //
-  //   [0] DW_TAG_class_type for "B"
-  //   [1] DW_TAG_class_type for "A"
-  //   [2] DW_TAG_namespace  for "lldb"
-  //   [3] DW_TAG_compile_unit or DW_TAG_partial_unit for the source file.
-  //
-  // We grab both contexts and make sure that everything matches all the way
-  // back to the compiler unit.
-
-  // First lets grab the decl contexts for both DIEs
-  decl_ctx_1 = die1.GetDeclContextDIEs();
-  decl_ctx_2 = die2.GetDeclContextDIEs();
-  // Make sure the context arrays have the same size, otherwise we are done
-  const size_t count1 = decl_ctx_1.size();
-  const size_t count2 = decl_ctx_2.size();
-  if (count1 != count2)
-    return false;
-
-  // Make sure the DW_TAG values match all the way back up the compile unit. If
-  // they don't, then we are done.
-  DWARFDIE decl_ctx_die1;
-  DWARFDIE decl_ctx_die2;
-  size_t i;
-  for (i = 0; i < count1; i++) {
-    decl_ctx_die1 = decl_ctx_1[i];
-    decl_ctx_die2 = decl_ctx_2[i];
-    if (decl_ctx_die1.Tag() != decl_ctx_die2.Tag())
-      return false;
-  }
-#ifndef NDEBUG
-
-  // Make sure the top item in the decl context die array is always
-  // DW_TAG_compile_unit or DW_TAG_partial_unit. If it isn't then
-  // something went wrong in the DWARFDIE::GetDeclContextDIEs()
-  // function.
-  dw_tag_t cu_tag = decl_ctx_1[count1 - 1].Tag();
-  UNUSED_IF_ASSERT_DISABLED(cu_tag);
-  assert(cu_tag == DW_TAG_compile_unit || cu_tag == DW_TAG_partial_unit);
-
-#endif
-  // Always skip the compile unit when comparing by only iterating up to "count
-  // - 1". Here we compare the names as we go.
-  for (i = 0; i < count1 - 1; i++) {
-    decl_ctx_die1 = decl_ctx_1[i];
-    decl_ctx_die2 = decl_ctx_2[i];
-    const char *name1 = decl_ctx_die1.GetName();
-    const char *name2 = decl_ctx_die2.GetName();
-    // If the string was from a DW_FORM_strp, then the pointer will often be
-    // the same!
-    if (name1 == name2)
-      continue;
-
-    // Name pointers are not equal, so only compare the strings if both are not
-    // NULL.
-    if (name1 && name2) {
-      // If the strings don't compare, we are done...
-      if (strcmp(name1, name2) != 0)
-        return false;
-    } else {
-      // One name was NULL while the other wasn't
-      return false;
-    }
-  }
-  // We made it through all of the checks and the declaration contexts are
-  // equal.
-  return true;
-}
-
 TypeSP
 SymbolFileDWARF::FindDefinitionTypeForDWARFDeclContext(const DWARFDIE &die) {
   TypeSP type_sp;

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

@@ -461,8 +461,6 @@ class SymbolFileDWARF : public SymbolFileCommon {
   FindBlockContainingSpecification(const DWARFDIE &die,
                                    dw_offset_t spec_block_die_offset);
 
-  bool DIEDeclContextsMatch(const DWARFDIE &die1, const DWARFDIE &die2);
-
   bool ClassContainsSelector(const DWARFDIE &class_die, ConstString selector);
 
   /// Parse call site entries (DW_TAG_call_site), including any nested call site