Reduce O(n2) performance overhead when parsing DWARF unit information.

	PR 28978
	* dwarf2.c (scan_unit_for_symbols): When performing second pass,
	check to see if the function or variable being processed is the
	same as the previous one.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 6ac8b96c57adef812005f0caf3db227794ce6ef5..fcf5abad5a19f1f0361a7b25abf6fc4bc851c4ce 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2022-03-21  Steiner H Gunderson  <steinar+sourceware@gunderson.no>
+
+       PR 28978
+       * dwarf2.c (scan_unit_for_symbols): When performing second pass,
+       check to see if the function or variable being processed is the
+       same as the previous one.
+
 2022-03-18  Viorel Preoteasa  <viorel.preoteasa@gmail.com>
 
        PR 28924

diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index fdf071c36e98082c725675cb0f5dfb360f7de9d5..bb176798f9a21d27d694967820931a28e9946f6c 100644 (file)
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -3293,6 +3293,36 @@ lookup_var_by_offset (bfd_uint64_t offset, struct varinfo * table)
 
 /* DWARF2 Compilation unit functions.  */
 
+static struct funcinfo *
+reverse_funcinfo_list (struct funcinfo *head)
+{
+  struct funcinfo *rhead;
+  struct funcinfo *temp;
+
+  for (rhead = NULL; head; head = temp)
+    {
+      temp = head->prev_func;
+      head->prev_func = rhead;
+      rhead = head;
+    }
+  return rhead;
+}
+
+static struct varinfo *
+reverse_varinfo_list (struct varinfo *head)
+{
+  struct varinfo *rhead;
+  struct varinfo *temp;
+
+  for (rhead = NULL; head; head = temp)
+    {
+      temp = head->prev_var;
+      head->prev_var = rhead;
+      rhead = head;
+    }
+  return rhead;
+}
+
 /* Scan over each die in a comp. unit looking for functions to add
    to the function table and variables to the variable table.  */
 
@@ -3308,7 +3338,9 @@ scan_unit_for_symbols (struct comp_unit *unit)
     struct funcinfo *func;
   } *nested_funcs;
   int nested_funcs_size;
-
+  struct funcinfo *last_func;
+  struct varinfo *last_var;
+  
   /* Maintain a stack of in-scope functions and inlined functions, which we
      can use to set the caller_func field.  */
   nested_funcs_size = 32;
@@ -3442,10 +3474,16 @@ scan_unit_for_symbols (struct comp_unit *unit)
        }
     }
 
+  unit->function_table = reverse_funcinfo_list (unit->function_table);
+  unit->variable_table = reverse_varinfo_list (unit->variable_table);
+
   /* This is the second pass over the abbrevs.  */      
   info_ptr = unit->first_child_die_ptr;
   nesting_level = 0;
   
+  last_func = NULL;
+  last_var = NULL;
+
   while (nesting_level >= 0)
     {
       unsigned int abbrev_number, i;
@@ -3481,16 +3519,32 @@ scan_unit_for_symbols (struct comp_unit *unit)
          || abbrev->tag == DW_TAG_entry_point
          || abbrev->tag == DW_TAG_inlined_subroutine)
        {
-         func = lookup_func_by_offset (current_offset, unit->function_table);
+         if (last_func
+             && last_func->prev_func
+             && last_func->prev_func->unit_offset == current_offset)
+           func = last_func->prev_func;
+         else
+           func = lookup_func_by_offset (current_offset, unit->function_table);
+
          if (func == NULL)
            goto fail;
+
+         last_func = func;
        }
       else if (abbrev->tag == DW_TAG_variable
               || abbrev->tag == DW_TAG_member)
        {
-         var = lookup_var_by_offset (current_offset, unit->variable_table);
+         if (last_var
+             && last_var->prev_var
+             && last_var->prev_var->unit_offset == current_offset)
+           var = last_var->prev_var;
+         else
+           var = lookup_var_by_offset (current_offset, unit->variable_table);
+
          if (var == NULL)
            goto fail;
+
+         last_var = var;
        }
 
       for (i = 0; i < abbrev->num_attrs; ++i)
@@ -3684,6 +3738,9 @@ scan_unit_for_symbols (struct comp_unit *unit)
        }
     }
 
+  unit->function_table = reverse_funcinfo_list (unit->function_table);
+  unit->variable_table = reverse_varinfo_list (unit->variable_table);
+
   free (nested_funcs);
   return true;
 
@@ -4047,36 +4104,6 @@ comp_unit_find_line (struct comp_unit *unit,
                                          linenumber_ptr);
 }
 
-static struct funcinfo *
-reverse_funcinfo_list (struct funcinfo *head)
-{
-  struct funcinfo *rhead;
-  struct funcinfo *temp;
-
-  for (rhead = NULL; head; head = temp)
-    {
-      temp = head->prev_func;
-      head->prev_func = rhead;
-      rhead = head;
-    }
-  return rhead;
-}
-
-static struct varinfo *
-reverse_varinfo_list (struct varinfo *head)
-{
-  struct varinfo *rhead;
-  struct varinfo *temp;
-
-  for (rhead = NULL; head; head = temp)
-    {
-      temp = head->prev_var;
-      head->prev_var = rhead;
-      rhead = head;
-    }
-  return rhead;
-}
-
 /* Extract all interesting funcinfos and varinfos of a compilation
    unit into hash tables for faster lookup.  Returns TRUE if no
    errors were enountered; FALSE otherwise.  */