[Bug lto/65536] LTO line number information garbled

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65536

--- Comment #33 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jan Hubicka from comment #26)
> Created attachment 35130 [details]
> linemap
> 
> this is a proof of concept patch that makes streamer in to collect locations
> into a "cache" and apply them in sorted order (looking up correct max_column
> hints) at the end of handling of a given section.  It also has facility to
> throw away locations of trees that are freed.
> while sorting at stream in time is not cool, it does not show top in the
> profiles
> and memory use of the cache is actually dominated by other stuff we read,
> so this seems to work quite well in practice. Main problem would be if
> someone
> copied/used the locator before cache is applied.
> 
> This helps to get all lines and most of carrets right on firefox. I killed my
> Chromium tree so can't test it there (Martin, perhaps you could try?)
> 
> I did not have much time today to test the patch.  It also saves quite a lot
> of
> memory, about 400MB on firefox I guess.

Looks sensible to me (apart from sorting at WPA time and missing TLC like
adding function/code comments and removing no-op hunks).

Richard.

> Honza