https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68173
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |stevenb.gcc at gmail dot com
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
callgrind points at bitmap_set_bit called via process_bb_lives ->
mark_regno_dead.
Maybe some code in that (the DCE code?) can be keyed on if (optimize).
in mark_regno_dead callgrind points to
bitmap_set_bit (bb_killed_pseudos, regno);
being the expensive one. I suppose the issue here is that the bit access
pattern
to that bitmap is random which exposes our O(n) complexity of
bitmap_find_bit...
Indeed for bitmap_find_bit the linear search for if (head->indx < indx) is
the "hot" part.
I wonder if we should (finally) use a RB tree for bitmap. I even remember
some patches posted to improve this (from Steven?) this or last year?
