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[Bug fortran/79165] 100% compile-time increase for polyhedron aermod by r244581


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79165

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |dmalcolm at gcc dot gnu.org

--- Comment #11 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #7)
[...]
> Tentatively remembering an error like above is of course quite broken (read:
> expensive).
> 
> So somehow with the tree.c hunk of the patch location_get_source_line
> (inclusive callees) gets 90 times more expensive (when using callgrind on
> aermod).

Even if we fixed that, this seems to have uncovered an issue with input.c: if I
add some logging to input.c, there seems to be something going badly wrong with
the caching of reading source lines, for this case at least.

get_next_line is being called many more times that I would have expected given
the pattern of calls to location_get_source_line.  For some reason, the cache
isn't working, and it's re-reading large chunks of the source file each time a
diagnostic_show_locus is called (even on repeated calls to access the same
line).

I'm investigating why the cache in input.c is failing.

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