[Bug bootstrap/86872] [9 Regression] LTO bootstrap failed with profiledbootstrap

["dmalcolm at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86872

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |dmalcolm at gcc dot gnu.org

--- Comment #3 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to H.J. Lu from comment #0)
> On x86-64, r263300 gave

Annotating it with the code in question:

> In function ‘gimple_simplify_32’:
> lto1: internal compiler error: in linemap_check_ordinary, at libcpp/include/line-map.h:587
> 0x5e2991 ???
>         ../../src-trunk/libcpp/include/line-map.h:587

  linemap_assert (MAP_ORDINARY_P (map));

> 0x93aeae ???
>         ../../src-trunk/libcpp/line-map.c:754

In linemap_line_start:
      /* Allocate the new line_map.  However, if the current map only has a
         single line we can sometimes just increase its column_bits instead. */
      if (line_delta < 0
          || last_line != ORDINARY_MAP_STARTING_LINE_NUMBER (map)
          || SOURCE_COLUMN (map, highest) >= (1U << (column_bits - range_bits))
          || range_bits < map->m_range_bits)
        map = linemap_check_ordinary
                (const_cast <line_map *>
                  (linemap_add (set, LC_RENAME,
                                ORDINARY_MAP_IN_SYSTEM_HEADER_P (map),
                                ORDINARY_MAP_FILE_NAME (map),
                                to_line)));

> 0x1d653e2 ???
>         ../../src-trunk/gcc/lto-streamer-in.c:194

in lto_location_cache::apply_location_cache ():
          linemap_line_start (line_table, loc.line, max + 1);

> 0x1d6661f ???
>         ../../src-trunk/gcc/lto-streamer-in.c:304

in stream_input_location_now:

  data_in->location_cache.apply_location_cache ();


> 0xbc5f88 ???
>         ../../src-trunk/gcc/gimple-streamer-in.c:111

in input_gimple_stmt:
  /* Read location information.  Caching here makes no sense until streamer
     cache can handle the following gimple_set_block.  */
  gimple_set_location (stmt, stream_input_location_now (&bp, data_in));


(etc)


linemap_add can return NULL with LC_LEAVE, but we have LC_RENAME.
The return value ("map") comes from:

  linemap_assert (reason != LC_ENTER_MACRO);
  line_map_ordinary *map
    = linemap_check_ordinary (new_linemap (set, start_location));
  map->reason = reason;


linemap_check_ordinary is:
   linemap_assert (MAP_ORDINARY_P (map));

which, in turn is:

inline bool
MAP_ORDINARY_P (const line_map *map)
{
  return map->start_location < LINE_MAP_MAX_LOCATION;
}

map->start_location shouldn't be able to change.

I believe what's happened is that:
  to_line >= LINE_MAP_MAX_LOCATION
within linemap_line_start.

That way, linemap_add would (unexpectedly) create a macro map, rather than an
ordinary map.

Presumably we need some kind of overflow handling here (assuming that the above
correctly characterizes the cause of the crash).

Also, it seems bad to be running out of location_t values.  We probably should
double-check that we're packing things efficiently.