Re: [patch] Speed up find_pc_section

["Ulrich Weigand" <uweigand@de.ibm.com>]

Paul Pluzhnikov wrote:

> 2009-08-08  Paul Pluzhnikov  <ppluzhnikov@google.com>
> 
>         * objfiles.c (qsort_cmp): Remove assert.
>         (preferred_obj_section): New function.
>         (update_section_map): Filter duplicates.

This patch breaks overlay support:

+static struct obj_section *
+preferred_obj_section (struct obj_section *a, struct obj_section *b)
+{
+  gdb_assert (obj_section_addr (a) == obj_section_addr (b));
+  gdb_assert ((a->objfile->separate_debug_objfile == b->objfile)
+	      || (b->objfile->separate_debug_objfile == a->objfile));
+  gdb_assert ((a->objfile->separate_debug_objfile_backlink == b->objfile)
+	      || (b->objfile->separate_debug_objfile_backlink == a->objfile));
+
+  if (a->objfile->separate_debug_objfile != NULL)
+    return a;
+  return b;
+}

+  /* With separate debuginfo files, we may have up to two (almost)
+     identical copies of some obj_sections in the map.
+     Filter out duplicates.  */
+  for (i = 0, j = 0; i < map_size; ++i)
+    {
+      struct obj_section *sect1 = map[i];
+      struct obj_section *sect2 = (i + 1 < map_size) ? map[i + 1] : NULL;
+
+      if (sect2 == NULL
+	  || obj_section_addr (sect1) != obj_section_addr (sect2))
+	map[j++] = sect1;
+      else
+	{
+	  map[j++] = preferred_obj_section (sect1, sect2);
+	  ++i;
+	}
+    }

The patch appears to assume that two sections with the same start
address must be from a separate debuginfo file.  Of course, in the
presence of overlays, you may have multiple regular sections with
the same start address -- that's the point of overlays :-)

These now always run into the assert above.

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com