------- Comment #14 from steven at gcc dot gnu dot org 2010-01-28 16:28 ------- Re. comment #12: I think both: Do not call df_set_bb_dirty in df_insn_rescan rescans a DEBUG_INSN, *and* mark dirty only certain problems. The last part is probably the most tricky bit: which problems to mark. I think the RD and CHAINS problems, at least, still need updating.
Updating a DF problem doesn't have to be a problem if the update doesn't result in any code changes. The fact that we run DCE in an LR update is a Bad Thing that was an unfortunate but necessary hack to fix some PR or another. But in general the DF problems shouldn't do any code modifications. I guess it should be documented somewhere that all DF problems except LR should not even think about modifying any insns... -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42889
