From f8b42d640155ee466255ac6942056f858ea2c554 Mon Sep 17 00:00:00 2001
From: Caroline Tice <cmtice@google.com>
Date: Fri, 20 Nov 2020 11:05:19 -0800
Subject: [PATCH 11/14] gold: dwp: further improve DWARF v5 memory efficiency

Apply basic patch by David Blaikie to update gold dwp tool to handle
DWARF v5. This is the third of three patches for DWARF v5.

This patch contains a few more efficiency improvements.

This patch created for Chrome OS by Caroline Tice.
Date: 20-Nov-2020
[Adrian Ratiu: rebased from v2.27 to v2.35.1]
[Adrian Ratiu: regenerated as proper git format-patch.]

Change-Id: If45091e5590f7f71b45d58a861eb83bfeb9c5c26
---
 elfcpp/dwarf.h |  8 ++++----
 gold/dwp.cc    | 25 ++++++++++---------------
 2 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/elfcpp/dwarf.h b/elfcpp/dwarf.h
index 3392be6223b..04a6031bc29 100644
--- a/elfcpp/dwarf.h
+++ b/elfcpp/dwarf.h
@@ -253,16 +253,16 @@ enum DW_LANG
 enum DW_SECT
 {
   DW_SECT_INFO = 1,
-  DW_SECT_TYPES = 2, // removed in v5
+  // DW_SECT_TYPES = 2, // removed in v5
   DW_SECT_ABBREV = 3,
   DW_SECT_LINE = 4,
   DW_SECT_LOCLISTS = 5, // was LOC pre-v5
   DW_SECT_STR_OFFSETS = 6,
   DW_SECT_MACRO = 7, // was MACINFO pre-v5
   DW_SECT_RNGLISTS = 8,  // was MACRO pre-v5
-  LEGACY_DW_SECT_TYPES = 20,
-  LEGACY_DW_SECT_LOC = 21,
-  LEGACY_DW_SECT_MACINFO = 22,
+  LEGACY_DW_SECT_TYPES = 2,
+  LEGACY_DW_SECT_LOC = 9,
+  LEGACY_DW_SECT_MACINFO = 10,
   DW_SECT_MAX = LEGACY_DW_SECT_MACINFO
 };
 
diff --git a/gold/dwp.cc b/gold/dwp.cc
index 2beaa51879f..7acb9b401bc 100644
--- a/gold/dwp.cc
+++ b/gold/dwp.cc
@@ -817,27 +817,15 @@ get_dwarf_section_name(elfcpp::DW_SECT section_id)
   static const char* dwarf_section_names[] = {
     NULL,		      // unused
     ".debug_info.dwo",	      // DW_SECT_INFO = 1
-    NULL,		      // unused
+    ".debug_types.dwo",	      // LEGACY_DW_SECT_TYPES = 2
     ".debug_abbrev.dwo",      // DW_SECT_ABBREV = 3
     ".debug_line.dwo",	      // DW_SECT_LINE = 4
     ".debug_loclists.dwo",    // DW_SECT_LOCLISTS = 5
     ".debug_str_offsets.dwo", // DW_SECT_STR_OFFSETS = 6
     ".debug_macro.dwo",	      // DW_SECT_MACRO = 7
     ".debug_rnglists.dwo",    // DW_SECT_RNGLISTS = 8
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    NULL,		      // unused
-    ".debug_types.dwo",	      // LEGACY_DW_SECT_TYPES = 20
-    ".debug_loc.dwo",	      // LEGACY_DW_SECT_LOC = 21
-    ".debug_macinfo.dwo",     // LEGACY_DW_SECT_MACINFO = 22
+    ".debug_loc.dwo",	      // LEGACY_DW_SECT_LOC = 9
+    ".debug_macinfo.dwo",     // LEGACY_DW_SECT_MACINFO = 10
   };
 
   gold_assert(section_id > 0 && section_id <= elfcpp::DW_SECT_MAX);
@@ -2183,6 +2171,13 @@ Dwp_output_file::write_index(const char* sect_name, const Dwp_index& index)
   const unsigned int nused = index.hash_table_used_slots();
   const unsigned int nrows = index.section_table_rows();
 
+  // If there is no contribution, don't create .debug_cu_index or
+  // .debug_ty_index. We can't assign a meaningful index version.  Assigning an
+  // arbitrary version is not great because an upper-level dwp may have to deal
+  // with mixed index versions.
+  if (nused == 0)
+    return;
+
   int column_mask = index.section_table_cols();
   unsigned int ncols = 0;
   for (unsigned int c = 1; c <= elfcpp::DW_SECT_MAX; ++c)
-- 
2.31.1