gdb/dwarf2: split .gdb_index reading code to own file

Move everything related to reading .gdb_index from read.c to
read-gdb-index.c.  The only entry point exposed by read-gdb-index.{c,h}
is dwarf2_read_gdb_index.

Change-Id: I1e32c8f0720086538de8d2f612f27545377099bc
Approved-By: Tom Tromey <tom@tromey.com>

4 files changed, 925 insertions, 845 deletions

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index dac5a66..5a0b3c8 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -1082,6 +1082,7 @@ COMMON_SFILES = \
 	dwarf2/loc.c \
 	dwarf2/macro.c \
 	dwarf2/read.c \
+	dwarf2/read-gdb-index.c \
 	dwarf2/section.c \
 	dwarf2/stringify.c \
 	eval.c \
@@ -1325,6 +1326,7 @@ HFILES_NO_SRCDIR = \
 	dwarf2/index-common.h \
 	dwarf2/loc.h \
 	dwarf2/read.h \
+	dwarf2/read-gdb-index.h \
 	event-top.h \
 	exceptions.h \
 	exec.h \
diff --git a/gdb/dwarf2/read-gdb-index.c b/gdb/dwarf2/read-gdb-index.c
new file mode 100644
index 0000000..1006386
--- /dev/null
+++ b/gdb/dwarf2/read-gdb-index.c
@@ -0,0 +1,874 @@
+/* Reading code for .gdb_index
+
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "read-gdb-index.h"
+
+#include "cli/cli-cmds.h"
+#include "complaints.h"
+#include "dwz.h"
+#include "gdb/gdb-index.h"
+#include "gdbsupport/gdb-checked-static-cast.h"
+#include "mapped-index.h"
+#include "read.h"
+
+/* When true, do not reject deprecated .gdb_index sections.  */
+static bool use_deprecated_index_sections = false;
+
+/* This is a view into the index that converts from bytes to an
+   offset_type, and allows indexing.  Unaligned bytes are specifically
+   allowed here, and handled via unpacking.  */
+
+class offset_view
+{
+public:
+  offset_view () = default;
+
+  explicit offset_view (gdb::array_view<const gdb_byte> bytes)
+    : m_bytes (bytes)
+  {
+  }
+
+  /* Extract the INDEXth offset_type from the array.  */
+  offset_type operator[] (size_t index) const
+  {
+    const gdb_byte *bytes = &m_bytes[index * sizeof (offset_type)];
+    return (offset_type) extract_unsigned_integer (bytes,
+						   sizeof (offset_type),
+						   BFD_ENDIAN_LITTLE);
+  }
+
+  /* Return the number of offset_types in this array.  */
+  size_t size () const
+  {
+    return m_bytes.size () / sizeof (offset_type);
+  }
+
+  /* Return true if this view is empty.  */
+  bool empty () const
+  {
+    return m_bytes.empty ();
+  }
+
+private:
+  /* The underlying bytes.  */
+  gdb::array_view<const gdb_byte> m_bytes;
+};
+
+/* A description of .gdb_index index.  The file format is described in
+   a comment by the code that writes the index.  */
+
+struct mapped_gdb_index final : public mapped_index_base
+{
+  /* Index data format version.  */
+  int version = 0;
+
+  /* The address table data.  */
+  gdb::array_view<const gdb_byte> address_table;
+
+  /* The symbol table, implemented as a hash table.  */
+  offset_view symbol_table;
+
+  /* A pointer to the constant pool.  */
+  gdb::array_view<const gdb_byte> constant_pool;
+
+  /* Return the index into the constant pool of the name of the IDXth
+     symbol in the symbol table.  */
+  offset_type symbol_name_index (offset_type idx) const
+  {
+    return symbol_table[2 * idx];
+  }
+
+  /* Return the index into the constant pool of the CU vector of the
+     IDXth symbol in the symbol table.  */
+  offset_type symbol_vec_index (offset_type idx) const
+  {
+    return symbol_table[2 * idx + 1];
+  }
+
+  bool symbol_name_slot_invalid (offset_type idx) const override
+  {
+    return (symbol_name_index (idx) == 0
+	    && symbol_vec_index (idx) == 0);
+  }
+
+  /* Convenience method to get at the name of the symbol at IDX in the
+     symbol table.  */
+  const char *symbol_name_at
+    (offset_type idx, dwarf2_per_objfile *per_objfile) const override
+  {
+    return (const char *) (this->constant_pool.data ()
+			   + symbol_name_index (idx));
+  }
+
+  size_t symbol_name_count () const override
+  { return this->symbol_table.size () / 2; }
+
+  quick_symbol_functions_up make_quick_functions () const override;
+
+  bool version_check () const override
+  {
+    return version >= 8;
+  }
+};
+
+struct dwarf2_gdb_index : public dwarf2_base_index_functions
+{
+  /* This dumps minimal information about the index.
+     It is called via "mt print objfiles".
+     One use is to verify .gdb_index has been loaded by the
+     gdb.dwarf2/gdb-index.exp testcase.  */
+  void dump (struct objfile *objfile) override;
+
+  void expand_matching_symbols
+    (struct objfile *,
+     const lookup_name_info &lookup_name,
+     domain_enum domain,
+     int global,
+     symbol_compare_ftype *ordered_compare) override;
+
+  bool expand_symtabs_matching
+    (struct objfile *objfile,
+     gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
+     const lookup_name_info *lookup_name,
+     gdb::function_view<expand_symtabs_symbol_matcher_ftype> symbol_matcher,
+     gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
+     block_search_flags search_flags,
+     domain_enum domain,
+     enum search_domain kind) override;
+};
+
+/* This dumps minimal information about the index.
+   It is called via "mt print objfiles".
+   One use is to verify .gdb_index has been loaded by the
+   gdb.dwarf2/gdb-index.exp testcase.  */
+
+void
+dwarf2_gdb_index::dump (struct objfile *objfile)
+{
+  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+
+  mapped_gdb_index *index = (gdb::checked_static_cast<mapped_gdb_index *>
+			     (per_objfile->per_bfd->index_table.get ()));
+  gdb_printf (".gdb_index: version %d\n", index->version);
+  gdb_printf ("\n");
+}
+
+/* Struct used to manage iterating over all CUs looking for a symbol.  */
+
+struct dw2_symtab_iterator
+{
+  /* The dwarf2_per_objfile owning the CUs we are iterating on.  */
+  dwarf2_per_objfile *per_objfile;
+  /* If set, only look for symbols that match that block.  Valid values are
+     GLOBAL_BLOCK and STATIC_BLOCK.  */
+  gdb::optional<block_enum> block_index;
+  /* The kind of symbol we're looking for.  */
+  domain_enum domain;
+  /* The list of CUs from the index entry of the symbol,
+     or NULL if not found.  */
+  offset_view vec;
+  /* The next element in VEC to look at.  */
+  int next;
+  /* The number of elements in VEC, or zero if there is no match.  */
+  int length;
+  /* Have we seen a global version of the symbol?
+     If so we can ignore all further global instances.
+     This is to work around gold/15646, inefficient gold-generated
+     indices.  */
+  int global_seen;
+};
+
+/* Initialize the index symtab iterator ITER, offset_type NAMEI variant.  */
+
+static void
+dw2_symtab_iter_init (struct dw2_symtab_iterator *iter,
+		      dwarf2_per_objfile *per_objfile,
+		      gdb::optional<block_enum> block_index,
+		      domain_enum domain, offset_type namei,
+		      mapped_gdb_index &index)
+{
+  iter->per_objfile = per_objfile;
+  iter->block_index = block_index;
+  iter->domain = domain;
+  iter->next = 0;
+  iter->global_seen = 0;
+  iter->vec = {};
+  iter->length = 0;
+
+  gdb_assert (!index.symbol_name_slot_invalid (namei));
+  offset_type vec_idx = index.symbol_vec_index (namei);
+
+  iter->vec = offset_view (index.constant_pool.slice (vec_idx));
+  iter->length = iter->vec[0];
+}
+
+/* Return the next matching CU or NULL if there are no more.  */
+
+static struct dwarf2_per_cu_data *
+dw2_symtab_iter_next (struct dw2_symtab_iterator *iter,
+		      mapped_gdb_index &index)
+{
+  dwarf2_per_objfile *per_objfile = iter->per_objfile;
+
+  for ( ; iter->next < iter->length; ++iter->next)
+    {
+      offset_type cu_index_and_attrs = iter->vec[iter->next + 1];
+      offset_type cu_index = GDB_INDEX_CU_VALUE (cu_index_and_attrs);
+      gdb_index_symbol_kind symbol_kind =
+	GDB_INDEX_SYMBOL_KIND_VALUE (cu_index_and_attrs);
+      /* Only check the symbol attributes if they're present.
+	 Indices prior to version 7 don't record them,
+	 and indices >= 7 may elide them for certain symbols
+	 (gold does this).  */
+      int attrs_valid = (index.version >= 7
+			 && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);
+
+      /* Don't crash on bad data.  */
+      if (cu_index >= per_objfile->per_bfd->all_units.size ())
+	{
+	  complaint (_(".gdb_index entry has bad CU index"
+		       " [in module %s]"), objfile_name (per_objfile->objfile));
+	  continue;
+	}
+
+      dwarf2_per_cu_data *per_cu = per_objfile->per_bfd->get_cu (cu_index);
+
+      /* Skip if already read in.  */
+      if (per_objfile->symtab_set_p (per_cu))
+	continue;
+
+      /* Check static vs global.  */
+      if (attrs_valid)
+	{
+	  bool is_static = GDB_INDEX_SYMBOL_STATIC_VALUE (cu_index_and_attrs);
+
+	  if (iter->block_index.has_value ())
+	    {
+	      bool want_static = *iter->block_index == STATIC_BLOCK;
+
+	      if (is_static != want_static)
+		continue;
+	    }
+
+	  /* Work around gold/15646.  */
+	  if (!is_static
+	      && symbol_kind == GDB_INDEX_SYMBOL_KIND_TYPE)
+	    {
+	      if (iter->global_seen)
+		continue;
+
+	      iter->global_seen = 1;
+	    }
+	}
+
+      /* Only check the symbol's kind if it has one.  */
+      if (attrs_valid)
+	{
+	  switch (iter->domain)
+	    {
+	    case VAR_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_VARIABLE
+		  && symbol_kind != GDB_INDEX_SYMBOL_KIND_FUNCTION
+		  /* Some types are also in VAR_DOMAIN.  */
+		  && symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
+		continue;
+	      break;
+	    case STRUCT_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
+		continue;
+	      break;
+	    case LABEL_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
+		continue;
+	      break;
+	    case MODULE_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
+		continue;
+	      break;
+	    default:
+	      break;
+	    }
+	}
+
+      ++iter->next;
+      return per_cu;
+    }
+
+  return NULL;
+}
+
+void
+dwarf2_gdb_index::expand_matching_symbols
+  (struct objfile *objfile,
+   const lookup_name_info &name, domain_enum domain,
+   int global,
+   symbol_compare_ftype *ordered_compare)
+{
+  /* Used for Ada.  */
+  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+
+  const block_enum block_kind = global ? GLOBAL_BLOCK : STATIC_BLOCK;
+
+  mapped_gdb_index &index
+    = *(gdb::checked_static_cast<mapped_gdb_index *>
+	(per_objfile->per_bfd->index_table.get ()));
+
+  const char *match_name = name.ada ().lookup_name ().c_str ();
+  auto matcher = [&] (const char *symname)
+  {
+    if (ordered_compare == nullptr)
+      return true;
+    return ordered_compare (symname, match_name) == 0;
+  };
+
+  dw2_expand_symtabs_matching_symbol (index, name, matcher,
+				      [&] (offset_type namei)
+    {
+      struct dw2_symtab_iterator iter;
+      struct dwarf2_per_cu_data *per_cu;
+
+      dw2_symtab_iter_init (&iter, per_objfile, block_kind, domain, namei,
+			    index);
+      while ((per_cu = dw2_symtab_iter_next (&iter, index)) != NULL)
+	dw2_expand_symtabs_matching_one (per_cu, per_objfile, nullptr,
+					 nullptr);
+      return true;
+    }, per_objfile);
+}
+
+/* Helper for dw2_expand_matching symtabs.  Called on each symbol
+   matched, to expand corresponding CUs that were marked.  IDX is the
+   index of the symbol name that matched.  */
+
+static bool
+dw2_expand_marked_cus
+  (dwarf2_per_objfile *per_objfile, offset_type idx,
+   gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
+   gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
+   block_search_flags search_flags,
+   search_domain kind)
+{
+  offset_type vec_len, vec_idx;
+  bool global_seen = false;
+  mapped_gdb_index &index
+    = *(gdb::checked_static_cast<mapped_gdb_index *>
+	(per_objfile->per_bfd->index_table.get ()));
+
+  offset_view vec (index.constant_pool.slice (index.symbol_vec_index (idx)));
+  vec_len = vec[0];
+  for (vec_idx = 0; vec_idx < vec_len; ++vec_idx)
+    {
+      offset_type cu_index_and_attrs = vec[vec_idx + 1];
+      /* This value is only valid for index versions >= 7.  */
+      int is_static = GDB_INDEX_SYMBOL_STATIC_VALUE (cu_index_and_attrs);
+      gdb_index_symbol_kind symbol_kind =
+	GDB_INDEX_SYMBOL_KIND_VALUE (cu_index_and_attrs);
+      int cu_index = GDB_INDEX_CU_VALUE (cu_index_and_attrs);
+      /* Only check the symbol attributes if they're present.
+	 Indices prior to version 7 don't record them,
+	 and indices >= 7 may elide them for certain symbols
+	 (gold does this).  */
+      int attrs_valid =
+	(index.version >= 7
+	 && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);
+
+      /* Work around gold/15646.  */
+      if (attrs_valid
+	  && !is_static
+	  && symbol_kind == GDB_INDEX_SYMBOL_KIND_TYPE)
+	{
+	  if (global_seen)
+	    continue;
+
+	  global_seen = true;
+	}
+
+      /* Only check the symbol's kind if it has one.  */
+      if (attrs_valid)
+	{
+	  if (is_static)
+	    {
+	      if ((search_flags & SEARCH_STATIC_BLOCK) == 0)
+		continue;
+	    }
+	  else
+	    {
+	      if ((search_flags & SEARCH_GLOBAL_BLOCK) == 0)
+		continue;
+	    }
+
+	  switch (kind)
+	    {
+	    case VARIABLES_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_VARIABLE)
+		continue;
+	      break;
+	    case FUNCTIONS_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_FUNCTION)
+		continue;
+	      break;
+	    case TYPES_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
+		continue;
+	      break;
+	    case MODULES_DOMAIN:
+	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
+		continue;
+	      break;
+	    default:
+	      break;
+	    }
+	}
+
+      /* Don't crash on bad data.  */
+      if (cu_index >= per_objfile->per_bfd->all_units.size ())
+	{
+	  complaint (_(".gdb_index entry has bad CU index"
+		       " [in module %s]"), objfile_name (per_objfile->objfile));
+	  continue;
+	}
+
+      dwarf2_per_cu_data *per_cu = per_objfile->per_bfd->get_cu (cu_index);
+      if (!dw2_expand_symtabs_matching_one (per_cu, per_objfile, file_matcher,
+					    expansion_notify))
+	return false;
+    }
+
+  return true;
+}
+
+bool
+dwarf2_gdb_index::expand_symtabs_matching
+    (struct objfile *objfile,
+     gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
+     const lookup_name_info *lookup_name,
+     gdb::function_view<expand_symtabs_symbol_matcher_ftype> symbol_matcher,
+     gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
+     block_search_flags search_flags,
+     domain_enum domain,
+     enum search_domain kind)
+{
+  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+
+  dw_expand_symtabs_matching_file_matcher (per_objfile, file_matcher);
+
+  /* This invariant is documented in quick-functions.h.  */
+  gdb_assert (lookup_name != nullptr || symbol_matcher == nullptr);
+  if (lookup_name == nullptr)
+    {
+      for (dwarf2_per_cu_data *per_cu
+	     : all_units_range (per_objfile->per_bfd))
+	{
+	  QUIT;
+
+	  if (!dw2_expand_symtabs_matching_one (per_cu, per_objfile,
+						file_matcher,
+						expansion_notify))
+	    return false;
+	}
+      return true;
+    }
+
+  mapped_gdb_index &index
+    = *(gdb::checked_static_cast<mapped_gdb_index *>
+	(per_objfile->per_bfd->index_table.get ()));
+
+  bool result
+    = dw2_expand_symtabs_matching_symbol (index, *lookup_name,
+					  symbol_matcher,
+					  [&] (offset_type idx)
+    {
+      if (!dw2_expand_marked_cus (per_objfile, idx, file_matcher,
+				  expansion_notify, search_flags, kind))
+	return false;
+      return true;
+    }, per_objfile);
+
+  return result;
+}
+
+quick_symbol_functions_up
+mapped_gdb_index::make_quick_functions () const
+{
+  return quick_symbol_functions_up (new dwarf2_gdb_index);
+}
+
+/* A helper function that reads the .gdb_index from BUFFER and fills
+   in MAP.  FILENAME is the name of the file containing the data;
+   it is used for error reporting.  DEPRECATED_OK is true if it is
+   ok to use deprecated sections.
+
+   CU_LIST, CU_LIST_ELEMENTS, TYPES_LIST, and TYPES_LIST_ELEMENTS are
+   out parameters that are filled in with information about the CU and
+   TU lists in the section.
+
+   Returns true if all went well, false otherwise.  */
+
+static bool
+read_gdb_index_from_buffer (const char *filename,
+			    bool deprecated_ok,
+			    gdb::array_view<const gdb_byte> buffer,
+			    mapped_gdb_index *map,
+			    const gdb_byte **cu_list,
+			    offset_type *cu_list_elements,
+			    const gdb_byte **types_list,
+			    offset_type *types_list_elements)
+{
+  const gdb_byte *addr = &buffer[0];
+  offset_view metadata (buffer);
+
+  /* Version check.  */
+  offset_type version = metadata[0];
+  /* Versions earlier than 3 emitted every copy of a psymbol.  This
+     causes the index to behave very poorly for certain requests.  Version 3
+     contained incomplete addrmap.  So, it seems better to just ignore such
+     indices.  */
+  if (version < 4)
+    {
+      static int warning_printed = 0;
+      if (!warning_printed)
+	{
+	  warning (_("Skipping obsolete .gdb_index section in %s."),
+		   filename);
+	  warning_printed = 1;
+	}
+      return 0;
+    }
+  /* Index version 4 uses a different hash function than index version
+     5 and later.
+
+     Versions earlier than 6 did not emit psymbols for inlined
+     functions.  Using these files will cause GDB not to be able to
+     set breakpoints on inlined functions by name, so we ignore these
+     indices unless the user has done
+     "set use-deprecated-index-sections on".  */
+  if (version < 6 && !deprecated_ok)
+    {
+      static int warning_printed = 0;
+      if (!warning_printed)
+	{
+	  warning (_("\
+Skipping deprecated .gdb_index section in %s.\n\
+Do \"set use-deprecated-index-sections on\" before the file is read\n\
+to use the section anyway."),
+		   filename);
+	  warning_printed = 1;
+	}
+      return 0;
+    }
+  /* Version 7 indices generated by gold refer to the CU for a symbol instead
+     of the TU (for symbols coming from TUs),
+     http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
+     Plus gold-generated indices can have duplicate entries for global symbols,
+     http://sourceware.org/bugzilla/show_bug.cgi?id=15646.
+     These are just performance bugs, and we can't distinguish gdb-generated
+     indices from gold-generated ones, so issue no warning here.  */
+
+  /* Indexes with higher version than the one supported by GDB may be no
+     longer backward compatible.  */
+  if (version > 8)
+    return 0;
+
+  map->version = version;
+
+  int i = 1;
+  *cu_list = addr + metadata[i];
+  *cu_list_elements = (metadata[i + 1] - metadata[i]) / 8;
+  ++i;
+
+  *types_list = addr + metadata[i];
+  *types_list_elements = (metadata[i + 1] - metadata[i]) / 8;
+  ++i;
+
+  const gdb_byte *address_table = addr + metadata[i];
+  const gdb_byte *address_table_end = addr + metadata[i + 1];
+  map->address_table
+    = gdb::array_view<const gdb_byte> (address_table, address_table_end);
+  ++i;
+
+  const gdb_byte *symbol_table = addr + metadata[i];
+  const gdb_byte *symbol_table_end = addr + metadata[i + 1];
+  map->symbol_table
+    = offset_view (gdb::array_view<const gdb_byte> (symbol_table,
+						    symbol_table_end));
+
+  ++i;
+  map->constant_pool = buffer.slice (metadata[i]);
+
+  if (map->constant_pool.empty () && !map->symbol_table.empty ())
+    {
+      /* An empty constant pool implies that all symbol table entries are
+	 empty.  Make map->symbol_table.empty () == true.  */
+      map->symbol_table
+	= offset_view (gdb::array_view<const gdb_byte> (symbol_table,
+							symbol_table));
+    }
+
+  return 1;
+}
+
+/* A helper for create_cus_from_gdb_index that handles a given list of
+   CUs.  */
+
+static void
+create_cus_from_gdb_index_list (dwarf2_per_bfd *per_bfd,
+				const gdb_byte *cu_list, offset_type n_elements,
+				struct dwarf2_section_info *section,
+				int is_dwz)
+{
+  for (offset_type i = 0; i < n_elements; i += 2)
+    {
+      gdb_static_assert (sizeof (ULONGEST) >= 8);
+
+      sect_offset sect_off
+	= (sect_offset) extract_unsigned_integer (cu_list, 8, BFD_ENDIAN_LITTLE);
+      ULONGEST length = extract_unsigned_integer (cu_list + 8, 8, BFD_ENDIAN_LITTLE);
+      cu_list += 2 * 8;
+
+      dwarf2_per_cu_data_up per_cu
+	= create_cu_from_index_list (per_bfd, section, is_dwz, sect_off,
+				     length);
+      per_bfd->all_units.push_back (std::move (per_cu));
+    }
+}
+
+/* Read the CU list from the mapped index, and use it to create all
+   the CU objects for PER_BFD.  */
+
+static void
+create_cus_from_gdb_index (dwarf2_per_bfd *per_bfd,
+			   const gdb_byte *cu_list, offset_type cu_list_elements,
+			   const gdb_byte *dwz_list, offset_type dwz_elements)
+{
+  gdb_assert (per_bfd->all_units.empty ());
+  per_bfd->all_units.reserve ((cu_list_elements + dwz_elements) / 2);
+
+  create_cus_from_gdb_index_list (per_bfd, cu_list, cu_list_elements,
+				  &per_bfd->info, 0);
+
+  if (dwz_elements == 0)
+    return;
+
+  dwz_file *dwz = dwarf2_get_dwz_file (per_bfd);
+  create_cus_from_gdb_index_list (per_bfd, dwz_list, dwz_elements,
+				  &dwz->info, 1);
+}
+
+/* Create the signatured type hash table from the index.  */
+
+static void
+create_signatured_type_table_from_gdb_index
+  (dwarf2_per_bfd *per_bfd, struct dwarf2_section_info *section,
+   const gdb_byte *bytes, offset_type elements)
+{
+  htab_up sig_types_hash = allocate_signatured_type_table ();
+
+  for (offset_type i = 0; i < elements; i += 3)
+    {
+      signatured_type_up sig_type;
+      ULONGEST signature;
+      void **slot;
+      cu_offset type_offset_in_tu;
+
+      gdb_static_assert (sizeof (ULONGEST) >= 8);
+      sect_offset sect_off
+	= (sect_offset) extract_unsigned_integer (bytes, 8, BFD_ENDIAN_LITTLE);
+      type_offset_in_tu
+	= (cu_offset) extract_unsigned_integer (bytes + 8, 8,
+						BFD_ENDIAN_LITTLE);
+      signature = extract_unsigned_integer (bytes + 16, 8, BFD_ENDIAN_LITTLE);
+      bytes += 3 * 8;
+
+      sig_type = per_bfd->allocate_signatured_type (signature);
+      sig_type->type_offset_in_tu = type_offset_in_tu;
+      sig_type->section = section;
+      sig_type->sect_off = sect_off;
+
+      slot = htab_find_slot (sig_types_hash.get (), sig_type.get (), INSERT);
+      *slot = sig_type.get ();
+
+      per_bfd->all_units.emplace_back (sig_type.release ());
+    }
+
+  per_bfd->signatured_types = std::move (sig_types_hash);
+}
+
+/* Read the address map data from the mapped GDB index, and use it to
+   populate the index_addrmap.  */
+
+static void
+create_addrmap_from_gdb_index (dwarf2_per_objfile *per_objfile,
+			       mapped_gdb_index *index)
+{
+  struct objfile *objfile = per_objfile->objfile;
+  dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
+  struct gdbarch *gdbarch = objfile->arch ();
+  const gdb_byte *iter, *end;
+  CORE_ADDR baseaddr;
+
+  addrmap_mutable mutable_map;
+
+  iter = index->address_table.data ();
+  end = iter + index->address_table.size ();
+
+  baseaddr = objfile->text_section_offset ();
+
+  while (iter < end)
+    {
+      ULONGEST hi, lo, cu_index;
+      lo = extract_unsigned_integer (iter, 8, BFD_ENDIAN_LITTLE);
+      iter += 8;
+      hi = extract_unsigned_integer (iter, 8, BFD_ENDIAN_LITTLE);
+      iter += 8;
+      cu_index = extract_unsigned_integer (iter, 4, BFD_ENDIAN_LITTLE);
+      iter += 4;
+
+      if (lo > hi)
+	{
+	  complaint (_(".gdb_index address table has invalid range (%s - %s)"),
+		     hex_string (lo), hex_string (hi));
+	  continue;
+	}
+
+      if (cu_index >= per_bfd->all_units.size ())
+	{
+	  complaint (_(".gdb_index address table has invalid CU number %u"),
+		     (unsigned) cu_index);
+	  continue;
+	}
+
+      lo = gdbarch_adjust_dwarf2_addr (gdbarch, lo + baseaddr) - baseaddr;
+      hi = gdbarch_adjust_dwarf2_addr (gdbarch, hi + baseaddr) - baseaddr;
+      mutable_map.set_empty (lo, hi - 1, per_bfd->get_cu (cu_index));
+    }
+
+  per_bfd->index_addrmap
+    = new (&per_bfd->obstack) addrmap_fixed (&per_bfd->obstack, &mutable_map);
+}
+
+/* See read-gdb-index.h.  */
+
+int
+dwarf2_read_gdb_index
+  (dwarf2_per_objfile *per_objfile,
+   get_gdb_index_contents_ftype get_gdb_index_contents,
+   get_gdb_index_contents_dwz_ftype get_gdb_index_contents_dwz)
+{
+  const gdb_byte *cu_list, *types_list, *dwz_list = NULL;
+  offset_type cu_list_elements, types_list_elements, dwz_list_elements = 0;
+  struct dwz_file *dwz;
+  struct objfile *objfile = per_objfile->objfile;
+  dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
+
+  gdb::array_view<const gdb_byte> main_index_contents
+    = get_gdb_index_contents (objfile, per_bfd);
+
+  if (main_index_contents.empty ())
+    return 0;
+
+  std::unique_ptr<mapped_gdb_index> map (new mapped_gdb_index);
+  if (!read_gdb_index_from_buffer (objfile_name (objfile),
+				   use_deprecated_index_sections,
+				   main_index_contents, map.get (), &cu_list,
+				   &cu_list_elements, &types_list,
+				   &types_list_elements))
+    return 0;
+
+  /* Don't use the index if it's empty.  */
+  if (map->symbol_table.empty ())
+    return 0;
+
+  /* If there is a .dwz file, read it so we can get its CU list as
+     well.  */
+  dwz = dwarf2_get_dwz_file (per_bfd);
+  if (dwz != NULL)
+    {
+      mapped_gdb_index dwz_map;
+      const gdb_byte *dwz_types_ignore;
+      offset_type dwz_types_elements_ignore;
+
+      gdb::array_view<const gdb_byte> dwz_index_content
+	= get_gdb_index_contents_dwz (objfile, dwz);
+
+      if (dwz_index_content.empty ())
+	return 0;
+
+      if (!read_gdb_index_from_buffer (bfd_get_filename (dwz->dwz_bfd.get ()),
+				       1, dwz_index_content, &dwz_map,
+				       &dwz_list, &dwz_list_elements,
+				       &dwz_types_ignore,
+				       &dwz_types_elements_ignore))
+	{
+	  warning (_("could not read '.gdb_index' section from %s; skipping"),
+		   bfd_get_filename (dwz->dwz_bfd.get ()));
+	  return 0;
+	}
+    }
+
+  create_cus_from_gdb_index (per_bfd, cu_list, cu_list_elements, dwz_list,
+			     dwz_list_elements);
+
+  if (types_list_elements)
+    {
+      /* We can only handle a single .debug_types when we have an
+	 index.  */
+      if (per_bfd->types.size () > 1)
+	{
+	  per_bfd->all_units.clear ();
+	  return 0;
+	}
+
+      dwarf2_section_info *section
+	= (per_bfd->types.size () == 1
+	   ? &per_bfd->types[0]
+	   : &per_bfd->info);
+
+      create_signatured_type_table_from_gdb_index (per_bfd, section, types_list,
+						   types_list_elements);
+    }
+
+  finalize_all_units (per_bfd);
+
+  create_addrmap_from_gdb_index (per_objfile, map.get ());
+
+  per_bfd->index_table = std::move (map);
+  per_bfd->quick_file_names_table =
+    create_quick_file_names_table (per_bfd->all_units.size ());
+
+  return 1;
+}
+
+void _initialize_read_gdb_index ();
+
+void
+_initialize_read_gdb_index ()
+{
+  add_setshow_boolean_cmd ("use-deprecated-index-sections",
+			   no_class, &use_deprecated_index_sections, _("\
+Set whether to use deprecated gdb_index sections."), _("\
+Show whether to use deprecated gdb_index sections."), _("\
+When enabled, deprecated .gdb_index sections are used anyway.\n\
+Normally they are ignored either because of a missing feature or\n\
+performance issue.\n\
+Warning: This option must be enabled before gdb reads the file."),
+			   NULL,
+			   NULL,
+			   &setlist, &showlist);
+}
diff --git a/gdb/dwarf2/read-gdb-index.h b/gdb/dwarf2/read-gdb-index.h
new file mode 100644
index 0000000..b69de4a
--- /dev/null
+++ b/gdb/dwarf2/read-gdb-index.h
@@ -0,0 +1,47 @@
+/* Reading code for .gdb_index
+
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef DWARF2_READ_GDB_INDEX_H
+#define DWARF2_READ_GDB_INDEX_H
+
+#include "gdbsupport/function-view.h"
+
+struct dwarf2_per_bfd;
+struct dwarf2_per_objfile;
+struct dwz_file;
+struct objfile;
+
+/* Callback types for dwarf2_read_gdb_index.  */
+
+typedef gdb::function_view
+    <gdb::array_view<const gdb_byte>(objfile *, dwarf2_per_bfd *)>
+    get_gdb_index_contents_ftype;
+typedef gdb::function_view
+    <gdb::array_view<const gdb_byte>(objfile *, dwz_file *)>
+    get_gdb_index_contents_dwz_ftype;
+
+/* Read .gdb_index.  If everything went ok, initialize the "quick"
+   elements of all the CUs and return 1.  Otherwise, return 0.  */
+
+int dwarf2_read_gdb_index
+  (dwarf2_per_objfile *per_objfile,
+   get_gdb_index_contents_ftype get_gdb_index_contents,
+   get_gdb_index_contents_dwz_ftype get_gdb_index_contents_dwz);
+
+#endif /* DWARF2_READ_GDB_INDEX_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 96e907b..77ebd95 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -41,6 +41,7 @@
 #include "dwarf2/dwz.h"
 #include "dwarf2/macro.h"
 #include "dwarf2/die.h"
+#include "dwarf2/read-gdb-index.h"
 #include "dwarf2/sect-names.h"
 #include "dwarf2/stringify.h"
 #include "dwarf2/public.h"
@@ -120,9 +121,6 @@ unsigned int dwarf_line_debug = 0;
 /* When true, cross-check physname against demangler.  */
 static bool check_physname = false;
 
-/* When true, do not reject deprecated .gdb_index sections.  */
-static bool use_deprecated_index_sections = false;
-
 /* This is used to store the data that is always per objfile.  */
 static const registry<objfile>::key<dwarf2_per_objfile>
      dwarf2_objfile_data_key;
@@ -158,103 +156,6 @@ static int dwarf2_loclist_block_index;
 /* Size of .debug_rnglists section header for 64-bit DWARF format.  */
 #define RNGLIST_HEADER_SIZE64 20
 
-/* This is a view into the index that converts from bytes to an
-   offset_type, and allows indexing.  Unaligned bytes are specifically
-   allowed here, and handled via unpacking.  */
-
-class offset_view
-{
-public:
-  offset_view () = default;
-
-  explicit offset_view (gdb::array_view<const gdb_byte> bytes)
-    : m_bytes (bytes)
-  {
-  }
-
-  /* Extract the INDEXth offset_type from the array.  */
-  offset_type operator[] (size_t index) const
-  {
-    const gdb_byte *bytes = &m_bytes[index * sizeof (offset_type)];
-    return (offset_type) extract_unsigned_integer (bytes,
-						   sizeof (offset_type),
-						   BFD_ENDIAN_LITTLE);
-  }
-
-  /* Return the number of offset_types in this array.  */
-  size_t size () const
-  {
-    return m_bytes.size () / sizeof (offset_type);
-  }
-
-  /* Return true if this view is empty.  */
-  bool empty () const
-  {
-    return m_bytes.empty ();
-  }
-
-private:
-  /* The underlying bytes.  */
-  gdb::array_view<const gdb_byte> m_bytes;
-};
-
-/* A description of .gdb_index index.  The file format is described in
-   a comment by the code that writes the index.  */
-
-struct mapped_gdb_index final : public mapped_index_base
-{
-  /* Index data format version.  */
-  int version = 0;
-
-  /* The address table data.  */
-  gdb::array_view<const gdb_byte> address_table;
-
-  /* The symbol table, implemented as a hash table.  */
-  offset_view symbol_table;
-
-  /* A pointer to the constant pool.  */
-  gdb::array_view<const gdb_byte> constant_pool;
-
-  /* Return the index into the constant pool of the name of the IDXth
-     symbol in the symbol table.  */
-  offset_type symbol_name_index (offset_type idx) const
-  {
-    return symbol_table[2 * idx];
-  }
-
-  /* Return the index into the constant pool of the CU vector of the
-     IDXth symbol in the symbol table.  */
-  offset_type symbol_vec_index (offset_type idx) const
-  {
-    return symbol_table[2 * idx + 1];
-  }
-
-  bool symbol_name_slot_invalid (offset_type idx) const override
-  {
-    return (symbol_name_index (idx) == 0
-	    && symbol_vec_index (idx) == 0);
-  }
-
-  /* Convenience method to get at the name of the symbol at IDX in the
-     symbol table.  */
-  const char *symbol_name_at
-    (offset_type idx, dwarf2_per_objfile *per_objfile) const override
-  {
-    return (const char *) (this->constant_pool.data ()
-			   + symbol_name_index (idx));
-  }
-
-  size_t symbol_name_count () const override
-  { return this->symbol_table.size () / 2; }
-
-  quick_symbol_functions_up make_quick_functions () const override;
-
-  bool version_check () const override
-  {
-    return version >= 8;
-  }
-};
-
 /* A description of the mapped .debug_names.
    Uninitialized map has CU_COUNT 0.  */
 struct mapped_debug_names final : public mapped_index_base
@@ -1763,28 +1664,6 @@ struct readnow_functions : public dwarf2_base_index_functions
   }
 };
 
-struct dwarf2_gdb_index : public dwarf2_base_index_functions
-{
-  void dump (struct objfile *objfile) override;
-
-  void expand_matching_symbols
-    (struct objfile *,
-     const lookup_name_info &lookup_name,
-     domain_enum domain,
-     int global,
-     symbol_compare_ftype *ordered_compare) override;
-
-  bool expand_symtabs_matching
-    (struct objfile *objfile,
-     gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
-     const lookup_name_info *lookup_name,
-     gdb::function_view<expand_symtabs_symbol_matcher_ftype> symbol_matcher,
-     gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
-     block_search_flags search_flags,
-     domain_enum domain,
-     enum search_domain kind) override;
-};
-
 struct dwarf2_debug_names_index : public dwarf2_base_index_functions
 {
   void dump (struct objfile *objfile) override;
@@ -1808,12 +1687,6 @@ struct dwarf2_debug_names_index : public dwarf2_base_index_functions
 };
 
 quick_symbol_functions_up
-mapped_gdb_index::make_quick_functions () const
-{
-  return quick_symbol_functions_up (new dwarf2_gdb_index);
-}
-
-quick_symbol_functions_up
 mapped_debug_names::make_quick_functions () const
 {
   return quick_symbol_functions_up (new dwarf2_debug_names_index);
@@ -1985,8 +1858,7 @@ dwarf2_per_bfd::allocate_signatured_type (ULONGEST signature)
   return result;
 }
 
-/* Return a new dwarf2_per_cu_data allocated on the per-bfd
-   obstack, and constructed with the specified field values.  */
+/* See read.h.  */
 
 dwarf2_per_cu_data_up
 create_cu_from_index_list (dwarf2_per_bfd *per_bfd,
@@ -2002,92 +1874,6 @@ create_cu_from_index_list (dwarf2_per_bfd *per_bfd,
   return the_cu;
 }
 
-/* A helper for create_cus_from_index that handles a given list of
-   CUs.  */
-
-static void
-create_cus_from_gdb_index_list (dwarf2_per_bfd *per_bfd,
-				const gdb_byte *cu_list, offset_type n_elements,
-				struct dwarf2_section_info *section,
-				int is_dwz)
-{
-  for (offset_type i = 0; i < n_elements; i += 2)
-    {
-      gdb_static_assert (sizeof (ULONGEST) >= 8);
-
-      sect_offset sect_off
-	= (sect_offset) extract_unsigned_integer (cu_list, 8, BFD_ENDIAN_LITTLE);
-      ULONGEST length = extract_unsigned_integer (cu_list + 8, 8, BFD_ENDIAN_LITTLE);
-      cu_list += 2 * 8;
-
-      dwarf2_per_cu_data_up per_cu
-	= create_cu_from_index_list (per_bfd, section, is_dwz, sect_off,
-				     length);
-      per_bfd->all_units.push_back (std::move (per_cu));
-    }
-}
-
-/* Read the CU list from the mapped index, and use it to create all
-   the CU objects for PER_BFD.  */
-
-static void
-create_cus_from_gdb_index (dwarf2_per_bfd *per_bfd,
-		       const gdb_byte *cu_list, offset_type cu_list_elements,
-		       const gdb_byte *dwz_list, offset_type dwz_elements)
-{
-  gdb_assert (per_bfd->all_units.empty ());
-  per_bfd->all_units.reserve ((cu_list_elements + dwz_elements) / 2);
-
-  create_cus_from_gdb_index_list (per_bfd, cu_list, cu_list_elements,
-				  &per_bfd->info, 0);
-
-  if (dwz_elements == 0)
-    return;
-
-  dwz_file *dwz = dwarf2_get_dwz_file (per_bfd);
-  create_cus_from_gdb_index_list (per_bfd, dwz_list, dwz_elements,
-				  &dwz->info, 1);
-}
-
-/* Create the signatured type hash table from the index.  */
-
-static void
-create_signatured_type_table_from_gdb_index
-  (dwarf2_per_bfd *per_bfd, struct dwarf2_section_info *section,
-   const gdb_byte *bytes, offset_type elements)
-{
-  htab_up sig_types_hash = allocate_signatured_type_table ();
-
-  for (offset_type i = 0; i < elements; i += 3)
-    {
-      signatured_type_up sig_type;
-      ULONGEST signature;
-      void **slot;
-      cu_offset type_offset_in_tu;
-
-      gdb_static_assert (sizeof (ULONGEST) >= 8);
-      sect_offset sect_off
-	= (sect_offset) extract_unsigned_integer (bytes, 8, BFD_ENDIAN_LITTLE);
-      type_offset_in_tu
-	= (cu_offset) extract_unsigned_integer (bytes + 8, 8,
-						BFD_ENDIAN_LITTLE);
-      signature = extract_unsigned_integer (bytes + 16, 8, BFD_ENDIAN_LITTLE);
-      bytes += 3 * 8;
-
-      sig_type = per_bfd->allocate_signatured_type (signature);
-      sig_type->type_offset_in_tu = type_offset_in_tu;
-      sig_type->section = section;
-      sig_type->sect_off = sect_off;
-
-      slot = htab_find_slot (sig_types_hash.get (), sig_type.get (), INSERT);
-      *slot = sig_type.get ();
-
-      per_bfd->all_units.emplace_back (sig_type.release ());
-    }
-
-  per_bfd->signatured_types = std::move (sig_types_hash);
-}
-
 /* Create the signatured type hash table from .debug_names.  */
 
 static void
@@ -2136,59 +1922,6 @@ create_signatured_type_table_from_debug_names
   per_objfile->per_bfd->signatured_types = std::move (sig_types_hash);
 }
 
-/* Read the address map data from the mapped GDB index, and use it to
-   populate the index_addrmap.  */
-
-static void
-create_addrmap_from_gdb_index (dwarf2_per_objfile *per_objfile,
-			       mapped_gdb_index *index)
-{
-  struct objfile *objfile = per_objfile->objfile;
-  dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
-  struct gdbarch *gdbarch = objfile->arch ();
-  const gdb_byte *iter, *end;
-  CORE_ADDR baseaddr;
-
-  addrmap_mutable mutable_map;
-
-  iter = index->address_table.data ();
-  end = iter + index->address_table.size ();
-
-  baseaddr = objfile->text_section_offset ();
-
-  while (iter < end)
-    {
-      ULONGEST hi, lo, cu_index;
-      lo = extract_unsigned_integer (iter, 8, BFD_ENDIAN_LITTLE);
-      iter += 8;
-      hi = extract_unsigned_integer (iter, 8, BFD_ENDIAN_LITTLE);
-      iter += 8;
-      cu_index = extract_unsigned_integer (iter, 4, BFD_ENDIAN_LITTLE);
-      iter += 4;
-
-      if (lo > hi)
-	{
-	  complaint (_(".gdb_index address table has invalid range (%s - %s)"),
-		     hex_string (lo), hex_string (hi));
-	  continue;
-	}
-
-      if (cu_index >= per_bfd->all_units.size ())
-	{
-	  complaint (_(".gdb_index address table has invalid CU number %u"),
-		     (unsigned) cu_index);
-	  continue;
-	}
-
-      lo = gdbarch_adjust_dwarf2_addr (gdbarch, lo + baseaddr) - baseaddr;
-      hi = gdbarch_adjust_dwarf2_addr (gdbarch, hi + baseaddr) - baseaddr;
-      mutable_map.set_empty (lo, hi - 1, per_bfd->get_cu (cu_index));
-    }
-
-  per_bfd->index_addrmap
-    = new (&per_bfd->obstack) addrmap_fixed (&per_bfd->obstack, &mutable_map);
-}
-
 /* Read the address map data from DWARF-5 .debug_aranges, and use it
    to populate given addrmap.  Returns true on success, false on
    failure.  */
@@ -2389,222 +2122,6 @@ create_addrmap_from_aranges (dwarf2_per_objfile *per_objfile,
 					       &mutable_map);
 }
 
-/* A helper function that reads the .gdb_index from BUFFER and fills
-   in MAP.  FILENAME is the name of the file containing the data;
-   it is used for error reporting.  DEPRECATED_OK is true if it is
-   ok to use deprecated sections.
-
-   CU_LIST, CU_LIST_ELEMENTS, TYPES_LIST, and TYPES_LIST_ELEMENTS are
-   out parameters that are filled in with information about the CU and
-   TU lists in the section.
-
-   Returns true if all went well, false otherwise.  */
-
-static bool
-read_gdb_index_from_buffer (const char *filename,
-			    bool deprecated_ok,
-			    gdb::array_view<const gdb_byte> buffer,
-			    mapped_gdb_index *map,
-			    const gdb_byte **cu_list,
-			    offset_type *cu_list_elements,
-			    const gdb_byte **types_list,
-			    offset_type *types_list_elements)
-{
-  const gdb_byte *addr = &buffer[0];
-  offset_view metadata (buffer);
-
-  /* Version check.  */
-  offset_type version = metadata[0];
-  /* Versions earlier than 3 emitted every copy of a psymbol.  This
-     causes the index to behave very poorly for certain requests.  Version 3
-     contained incomplete addrmap.  So, it seems better to just ignore such
-     indices.  */
-  if (version < 4)
-    {
-      static int warning_printed = 0;
-      if (!warning_printed)
-	{
-	  warning (_("Skipping obsolete .gdb_index section in %s."),
-		   filename);
-	  warning_printed = 1;
-	}
-      return 0;
-    }
-  /* Index version 4 uses a different hash function than index version
-     5 and later.
-
-     Versions earlier than 6 did not emit psymbols for inlined
-     functions.  Using these files will cause GDB not to be able to
-     set breakpoints on inlined functions by name, so we ignore these
-     indices unless the user has done
-     "set use-deprecated-index-sections on".  */
-  if (version < 6 && !deprecated_ok)
-    {
-      static int warning_printed = 0;
-      if (!warning_printed)
-	{
-	  warning (_("\
-Skipping deprecated .gdb_index section in %s.\n\
-Do \"set use-deprecated-index-sections on\" before the file is read\n\
-to use the section anyway."),
-		   filename);
-	  warning_printed = 1;
-	}
-      return 0;
-    }
-  /* Version 7 indices generated by gold refer to the CU for a symbol instead
-     of the TU (for symbols coming from TUs),
-     http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
-     Plus gold-generated indices can have duplicate entries for global symbols,
-     http://sourceware.org/bugzilla/show_bug.cgi?id=15646.
-     These are just performance bugs, and we can't distinguish gdb-generated
-     indices from gold-generated ones, so issue no warning here.  */
-
-  /* Indexes with higher version than the one supported by GDB may be no
-     longer backward compatible.  */
-  if (version > 8)
-    return 0;
-
-  map->version = version;
-
-  int i = 1;
-  *cu_list = addr + metadata[i];
-  *cu_list_elements = (metadata[i + 1] - metadata[i]) / 8;
-  ++i;
-
-  *types_list = addr + metadata[i];
-  *types_list_elements = (metadata[i + 1] - metadata[i]) / 8;
-  ++i;
-
-  const gdb_byte *address_table = addr + metadata[i];
-  const gdb_byte *address_table_end = addr + metadata[i + 1];
-  map->address_table
-    = gdb::array_view<const gdb_byte> (address_table, address_table_end);
-  ++i;
-
-  const gdb_byte *symbol_table = addr + metadata[i];
-  const gdb_byte *symbol_table_end = addr + metadata[i + 1];
-  map->symbol_table
-    = offset_view (gdb::array_view<const gdb_byte> (symbol_table,
-						    symbol_table_end));
-
-  ++i;
-  map->constant_pool = buffer.slice (metadata[i]);
-
-  if (map->constant_pool.empty () && !map->symbol_table.empty ())
-    {
-      /* An empty constant pool implies that all symbol table entries are
-	 empty.  Make map->symbol_table.empty () == true.  */
-      map->symbol_table
-	= offset_view (gdb::array_view<const gdb_byte> (symbol_table,
-							symbol_table));
-    }
-
-  return 1;
-}
-
-/* Callback types for dwarf2_read_gdb_index.  */
-
-typedef gdb::function_view
-    <gdb::array_view<const gdb_byte>(objfile *, dwarf2_per_bfd *)>
-    get_gdb_index_contents_ftype;
-typedef gdb::function_view
-    <gdb::array_view<const gdb_byte>(objfile *, dwz_file *)>
-    get_gdb_index_contents_dwz_ftype;
-
-/* Read .gdb_index.  If everything went ok, initialize the "quick"
-   elements of all the CUs and return 1.  Otherwise, return 0.  */
-
-static int
-dwarf2_read_gdb_index
-  (dwarf2_per_objfile *per_objfile,
-   get_gdb_index_contents_ftype get_gdb_index_contents,
-   get_gdb_index_contents_dwz_ftype get_gdb_index_contents_dwz)
-{
-  const gdb_byte *cu_list, *types_list, *dwz_list = NULL;
-  offset_type cu_list_elements, types_list_elements, dwz_list_elements = 0;
-  struct dwz_file *dwz;
-  struct objfile *objfile = per_objfile->objfile;
-  dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
-
-  gdb::array_view<const gdb_byte> main_index_contents
-    = get_gdb_index_contents (objfile, per_bfd);
-
-  if (main_index_contents.empty ())
-    return 0;
-
-  std::unique_ptr<mapped_gdb_index> map (new mapped_gdb_index);
-  if (!read_gdb_index_from_buffer (objfile_name (objfile),
-				   use_deprecated_index_sections,
-				   main_index_contents, map.get (), &cu_list,
-				   &cu_list_elements, &types_list,
-				   &types_list_elements))
-    return 0;
-
-  /* Don't use the index if it's empty.  */
-  if (map->symbol_table.empty ())
-    return 0;
-
-  /* If there is a .dwz file, read it so we can get its CU list as
-     well.  */
-  dwz = dwarf2_get_dwz_file (per_bfd);
-  if (dwz != NULL)
-    {
-      mapped_gdb_index dwz_map;
-      const gdb_byte *dwz_types_ignore;
-      offset_type dwz_types_elements_ignore;
-
-      gdb::array_view<const gdb_byte> dwz_index_content
-	= get_gdb_index_contents_dwz (objfile, dwz);
-
-      if (dwz_index_content.empty ())
-	return 0;
-
-      if (!read_gdb_index_from_buffer (bfd_get_filename (dwz->dwz_bfd.get ()),
-				       1, dwz_index_content, &dwz_map,
-				       &dwz_list, &dwz_list_elements,
-				       &dwz_types_ignore,
-				       &dwz_types_elements_ignore))
-	{
-	  warning (_("could not read '.gdb_index' section from %s; skipping"),
-		   bfd_get_filename (dwz->dwz_bfd.get ()));
-	  return 0;
-	}
-    }
-
-  create_cus_from_gdb_index (per_bfd, cu_list, cu_list_elements, dwz_list,
-			     dwz_list_elements);
-
-  if (types_list_elements)
-    {
-      /* We can only handle a single .debug_types when we have an
-	 index.  */
-      if (per_bfd->types.size () > 1)
-	{
-	  per_bfd->all_units.clear ();
-	  return 0;
-	}
-
-      dwarf2_section_info *section
-	= (per_bfd->types.size () == 1
-	   ? &per_bfd->types[0]
-	   : &per_bfd->info);
-
-      create_signatured_type_table_from_gdb_index (per_bfd, section, types_list,
-						   types_list_elements);
-    }
-
-  finalize_all_units (per_bfd);
-
-  create_addrmap_from_gdb_index (per_objfile, map.get ());
-
-  per_bfd->index_table = std::move (map);
-  per_bfd->quick_file_names_table =
-    create_quick_file_names_table (per_bfd->all_units.size ());
-
-  return 1;
-}
-
 /* die_reader_func for dw2_get_file_names.  */
 
 static void
@@ -2796,150 +2313,6 @@ dwarf2_base_index_functions::forget_cached_source_info
     per_cu->free_cached_file_names ();
 }
 
-/* Struct used to manage iterating over all CUs looking for a symbol.  */
-
-struct dw2_symtab_iterator
-{
-  /* The dwarf2_per_objfile owning the CUs we are iterating on.  */
-  dwarf2_per_objfile *per_objfile;
-  /* If set, only look for symbols that match that block.  Valid values are
-     GLOBAL_BLOCK and STATIC_BLOCK.  */
-  gdb::optional<block_enum> block_index;
-  /* The kind of symbol we're looking for.  */
-  domain_enum domain;
-  /* The list of CUs from the index entry of the symbol,
-     or NULL if not found.  */
-  offset_view vec;
-  /* The next element in VEC to look at.  */
-  int next;
-  /* The number of elements in VEC, or zero if there is no match.  */
-  int length;
-  /* Have we seen a global version of the symbol?
-     If so we can ignore all further global instances.
-     This is to work around gold/15646, inefficient gold-generated
-     indices.  */
-  int global_seen;
-};
-
-/* Initialize the index symtab iterator ITER, offset_type NAMEI variant.  */
-
-static void
-dw2_symtab_iter_init (struct dw2_symtab_iterator *iter,
-		      dwarf2_per_objfile *per_objfile,
-		      gdb::optional<block_enum> block_index,
-		      domain_enum domain, offset_type namei,
-		      mapped_gdb_index &index)
-{
-  iter->per_objfile = per_objfile;
-  iter->block_index = block_index;
-  iter->domain = domain;
-  iter->next = 0;
-  iter->global_seen = 0;
-  iter->vec = {};
-  iter->length = 0;
-
-  gdb_assert (!index.symbol_name_slot_invalid (namei));
-  offset_type vec_idx = index.symbol_vec_index (namei);
-
-  iter->vec = offset_view (index.constant_pool.slice (vec_idx));
-  iter->length = iter->vec[0];
-}
-
-/* Return the next matching CU or NULL if there are no more.  */
-
-static struct dwarf2_per_cu_data *
-dw2_symtab_iter_next (struct dw2_symtab_iterator *iter,
-		      mapped_gdb_index &index)
-{
-  dwarf2_per_objfile *per_objfile = iter->per_objfile;
-
-  for ( ; iter->next < iter->length; ++iter->next)
-    {
-      offset_type cu_index_and_attrs = iter->vec[iter->next + 1];
-      offset_type cu_index = GDB_INDEX_CU_VALUE (cu_index_and_attrs);
-      gdb_index_symbol_kind symbol_kind =
-	GDB_INDEX_SYMBOL_KIND_VALUE (cu_index_and_attrs);
-      /* Only check the symbol attributes if they're present.
-	 Indices prior to version 7 don't record them,
-	 and indices >= 7 may elide them for certain symbols
-	 (gold does this).  */
-      int attrs_valid = (index.version >= 7
-			 && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);
-
-      /* Don't crash on bad data.  */
-      if (cu_index >= per_objfile->per_bfd->all_units.size ())
-	{
-	  complaint (_(".gdb_index entry has bad CU index"
-		       " [in module %s]"), objfile_name (per_objfile->objfile));
-	  continue;
-	}
-
-      dwarf2_per_cu_data *per_cu = per_objfile->per_bfd->get_cu (cu_index);
-
-      /* Skip if already read in.  */
-      if (per_objfile->symtab_set_p (per_cu))
-	continue;
-
-      /* Check static vs global.  */
-      if (attrs_valid)
-	{
-	  bool is_static = GDB_INDEX_SYMBOL_STATIC_VALUE (cu_index_and_attrs);
-
-	  if (iter->block_index.has_value ())
-	    {
-	      bool want_static = *iter->block_index == STATIC_BLOCK;
-
-	      if (is_static != want_static)
-		continue;
-	    }
-
-	  /* Work around gold/15646.  */
-	  if (!is_static
-	      && symbol_kind == GDB_INDEX_SYMBOL_KIND_TYPE)
-	    {
-	      if (iter->global_seen)
-		continue;
-
-	      iter->global_seen = 1;
-	    }
-	}
-
-      /* Only check the symbol's kind if it has one.  */
-      if (attrs_valid)
-	{
-	  switch (iter->domain)
-	    {
-	    case VAR_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_VARIABLE
-		  && symbol_kind != GDB_INDEX_SYMBOL_KIND_FUNCTION
-		  /* Some types are also in VAR_DOMAIN.  */
-		  && symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
-		continue;
-	      break;
-	    case STRUCT_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
-		continue;
-	      break;
-	    case LABEL_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
-		continue;
-	      break;
-	    case MODULE_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
-		continue;
-	      break;
-	    default:
-	      break;
-	    }
-	}
-
-      ++iter->next;
-      return per_cu;
-    }
-
-  return NULL;
-}
-
 void
 dwarf2_base_index_functions::print_stats (struct objfile *objfile,
 					  bool print_bcache)
@@ -2962,22 +2335,6 @@ dwarf2_base_index_functions::print_stats (struct objfile *objfile,
   gdb_printf (_("  Number of unread CUs: %d\n"), count);
 }
 
-/* This dumps minimal information about the index.
-   It is called via "mt print objfiles".
-   One use is to verify .gdb_index has been loaded by the
-   gdb.dwarf2/gdb-index.exp testcase.  */
-
-void
-dwarf2_gdb_index::dump (struct objfile *objfile)
-{
-  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
-
-  mapped_gdb_index *index = (gdb::checked_static_cast<mapped_gdb_index *>
-			     (per_objfile->per_bfd->index_table.get ()));
-  gdb_printf (".gdb_index: version %d\n", index->version);
-  gdb_printf ("\n");
-}
-
 void
 dwarf2_base_index_functions::expand_all_symtabs (struct objfile *objfile)
 {
@@ -2997,44 +2354,6 @@ dwarf2_base_index_functions::expand_all_symtabs (struct objfile *objfile)
     }
 }
 
-void
-dwarf2_gdb_index::expand_matching_symbols
-  (struct objfile *objfile,
-   const lookup_name_info &name, domain_enum domain,
-   int global,
-   symbol_compare_ftype *ordered_compare)
-{
-  /* Used for Ada.  */
-  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
-
-  const block_enum block_kind = global ? GLOBAL_BLOCK : STATIC_BLOCK;
-
-  mapped_gdb_index &index
-    = *(gdb::checked_static_cast<mapped_gdb_index *>
-	(per_objfile->per_bfd->index_table.get ()));
-
-  const char *match_name = name.ada ().lookup_name ().c_str ();
-  auto matcher = [&] (const char *symname)
-  {
-    if (ordered_compare == nullptr)
-      return true;
-    return ordered_compare (symname, match_name) == 0;
-  };
-
-  dw2_expand_symtabs_matching_symbol (index, name, matcher,
-				      [&] (offset_type namei)
-    {
-      struct dw2_symtab_iterator iter;
-      struct dwarf2_per_cu_data *per_cu;
-
-      dw2_symtab_iter_init (&iter, per_objfile, block_kind, domain, namei,
-			    index);
-      while ((per_cu = dw2_symtab_iter_next (&iter, index)) != NULL)
-	dw2_expand_symtabs_matching_one (per_cu, per_objfile, nullptr,
-					 nullptr);
-      return true;
-    }, per_objfile);
-}
 
 /* Starting from a search name, return the string that finds the upper
    bound of all strings that start with SEARCH_NAME in a sorted name
@@ -3837,107 +3156,6 @@ dw2_expand_symtabs_matching_one
   return true;
 }
 
-/* Helper for dw2_expand_matching symtabs.  Called on each symbol
-   matched, to expand corresponding CUs that were marked.  IDX is the
-   index of the symbol name that matched.  */
-
-static bool
-dw2_expand_marked_cus
-  (dwarf2_per_objfile *per_objfile, offset_type idx,
-   gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
-   gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
-   block_search_flags search_flags,
-   search_domain kind)
-{
-  offset_type vec_len, vec_idx;
-  bool global_seen = false;
-  mapped_gdb_index &index
-    = *(gdb::checked_static_cast<mapped_gdb_index *>
-	(per_objfile->per_bfd->index_table.get ()));
-
-  offset_view vec (index.constant_pool.slice (index.symbol_vec_index (idx)));
-  vec_len = vec[0];
-  for (vec_idx = 0; vec_idx < vec_len; ++vec_idx)
-    {
-      offset_type cu_index_and_attrs = vec[vec_idx + 1];
-      /* This value is only valid for index versions >= 7.  */
-      int is_static = GDB_INDEX_SYMBOL_STATIC_VALUE (cu_index_and_attrs);
-      gdb_index_symbol_kind symbol_kind =
-	GDB_INDEX_SYMBOL_KIND_VALUE (cu_index_and_attrs);
-      int cu_index = GDB_INDEX_CU_VALUE (cu_index_and_attrs);
-      /* Only check the symbol attributes if they're present.
-	 Indices prior to version 7 don't record them,
-	 and indices >= 7 may elide them for certain symbols
-	 (gold does this).  */
-      int attrs_valid =
-	(index.version >= 7
-	 && symbol_kind != GDB_INDEX_SYMBOL_KIND_NONE);
-
-      /* Work around gold/15646.  */
-      if (attrs_valid
-	  && !is_static
-	  && symbol_kind == GDB_INDEX_SYMBOL_KIND_TYPE)
-	{
-	  if (global_seen)
-	    continue;
-
-	  global_seen = true;
-	}
-
-      /* Only check the symbol's kind if it has one.  */
-      if (attrs_valid)
-	{
-	  if (is_static)
-	    {
-	      if ((search_flags & SEARCH_STATIC_BLOCK) == 0)
-		continue;
-	    }
-	  else
-	    {
-	      if ((search_flags & SEARCH_GLOBAL_BLOCK) == 0)
-		continue;
-	    }
-
-	  switch (kind)
-	    {
-	    case VARIABLES_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_VARIABLE)
-		continue;
-	      break;
-	    case FUNCTIONS_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_FUNCTION)
-		continue;
-	      break;
-	    case TYPES_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_TYPE)
-		continue;
-	      break;
-	    case MODULES_DOMAIN:
-	      if (symbol_kind != GDB_INDEX_SYMBOL_KIND_OTHER)
-		continue;
-	      break;
-	    default:
-	      break;
-	    }
-	}
-
-      /* Don't crash on bad data.  */
-      if (cu_index >= per_objfile->per_bfd->all_units.size ())
-	{
-	  complaint (_(".gdb_index entry has bad CU index"
-		       " [in module %s]"), objfile_name (per_objfile->objfile));
-	  continue;
-	}
-
-      dwarf2_per_cu_data *per_cu = per_objfile->per_bfd->get_cu (cu_index);
-      if (!dw2_expand_symtabs_matching_one (per_cu, per_objfile, file_matcher,
-					    expansion_notify))
-	return false;
-    }
-
-  return true;
-}
-
 /* See read.h.  */
 
 void
@@ -4037,55 +3255,6 @@ dw_expand_symtabs_matching_file_matcher
     }
 }
 
-bool
-dwarf2_gdb_index::expand_symtabs_matching
-    (struct objfile *objfile,
-     gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher,
-     const lookup_name_info *lookup_name,
-     gdb::function_view<expand_symtabs_symbol_matcher_ftype> symbol_matcher,
-     gdb::function_view<expand_symtabs_exp_notify_ftype> expansion_notify,
-     block_search_flags search_flags,
-     domain_enum domain,
-     enum search_domain kind)
-{
-  dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
-
-  dw_expand_symtabs_matching_file_matcher (per_objfile, file_matcher);
-
-  /* This invariant is documented in quick-functions.h.  */
-  gdb_assert (lookup_name != nullptr || symbol_matcher == nullptr);
-  if (lookup_name == nullptr)
-    {
-      for (dwarf2_per_cu_data *per_cu
-	     : all_units_range (per_objfile->per_bfd))
-	{
-	  QUIT;
-
-	  if (!dw2_expand_symtabs_matching_one (per_cu, per_objfile,
-						file_matcher,
-						expansion_notify))
-	    return false;
-	}
-      return true;
-    }
-
-  mapped_gdb_index &index
-    = *(gdb::checked_static_cast<mapped_gdb_index *>
-	(per_objfile->per_bfd->index_table.get ()));
-
-  bool result
-    = dw2_expand_symtabs_matching_symbol (index, *lookup_name,
-					  symbol_matcher,
-					  [&] (offset_type idx)
-    {
-      if (!dw2_expand_marked_cus (per_objfile, idx, file_matcher,
-				  expansion_notify, search_flags, kind))
-	return false;
-      return true;
-    }, per_objfile);
-
-  return result;
-}
 
 /* A helper for dw2_find_pc_sect_compunit_symtab which finds the most specific
    symtab.  */
@@ -23778,18 +22947,6 @@ the demangler."),
 			   NULL, show_check_physname,
 			   &setdebuglist, &showdebuglist);
 
-  add_setshow_boolean_cmd ("use-deprecated-index-sections",
-			   no_class, &use_deprecated_index_sections, _("\
-Set whether to use deprecated gdb_index sections."), _("\
-Show whether to use deprecated gdb_index sections."), _("\
-When enabled, deprecated .gdb_index sections are used anyway.\n\
-Normally they are ignored either because of a missing feature or\n\
-performance issue.\n\
-Warning: This option must be enabled before gdb reads the file."),
-			   NULL,
-			   NULL,
-			   &setlist, &showlist);
-
   dwarf2_locexpr_index = register_symbol_computed_impl (LOC_COMPUTED,
 							&dwarf2_locexpr_funcs);
   dwarf2_loclist_index = register_symbol_computed_impl (LOC_COMPUTED,