https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65536
--- Comment #45 from Manuel López-Ibáñez <manu at gcc dot gnu.org> --- (In reply to Jan Hubicka from comment #42) > Hi, > I read linemap_line_start and I think I noticed few issues with respect > to overflows and lines being added randomly. I honestly think this is too sensitive for stage3. I'm also not very much in favour for optimizing out-of-order creating of line-maps. That is not the typical case outside LTO and I would argue it should not be the typical case in LTO either. Of course, fixing overflow problems is orthogonal and desirable and should be submitted as a separate patch. > 1) line_delta is computed as to_line SOURCE_LINE (map, set->highest_line) > I think the last inserted line is not very releavnt. What we care about > is > the base of the last location and to keep thing dense how much we are > stretching the value range from highest inserted element (inserting into > middle > is cheap). My guess is that the motivation here is that, if there is a large gap, it means that we didn't get asked any source_location since a lot of lines ago. thus it would save a lot of source_locations to simply start a new map now. Of course, this does not work for out-of-order, but why should we pessimize typical usage for something that should be fixed in LTO? > 2) (line_delta > 10 && line_delta * ORDINARY_MAP_NUMBER_OF_COLUMN_BITS (map) > > 1000) > ORDINARY_MAP_NUMBER_OF_COLUMN_BITS (map) is in range 7... 15, so it never > gets high enough to make this conditional trigger. I changed it to: I don't understand this. A line_delta of 67 (1000/15) will already trigger it. > 4) the code deciding whether to do reuse seems worng: > if (line_delta < 0 > || last_line != ORDINARY_MAP_STARTING_LINE_NUMBER (map) > || SOURCE_COLUMN (map, highest) >= (1U << column_bits)) > > line_delta really should be base_line_delta, we do not need to give up > when map's line is 1, SOURCE_LINE (map, set->highest_line) is 5 > and we are requested to switch to line 3. If you insert a line out of order without creating a new map, then linemap_position_for_column will return the wrong value.
