http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56858
--- Comment #8 from Steven Bosscher <steven at gcc dot gnu.org> 2013-04-08 18:43:25 UTC --- (In reply to comment #7) > (In reply to comment #6) > > Do you recall when that was? Must have been long, long ago... > > I've tried to find where it happened, and the rewrite was done before > > at least r43893 (Tue Jul 10 10:38:10 2001 UTC (11 years, 9 months ago). > > I would have said it was much more recent than that, but I just checked > gcc 4.2 and you're right that we'd already switched away from these notes > somewhere prior to 2009. > > > Does that mean alpha ev4 and ev5 fp exceptions have been broken for > > maybe 12 years? If that's really the case then I'd say the proper way > > forward is to remove support for those alpha variants as they're > > obviously not used and/or tested by anyone... > > It's not as bad as all that. It's only the extremely uncommon case of > throwing a c++ exception in response to an fp exception, with a handler > in the same function. My guess is that no one at all does this, and so > the wrong-code is somewhat theoretical. > > Normal fp code without c++ exceptions is working fine. > > Which is why I would not suggest writing new eh code for this, but > instead moving the existing code to later in the pass list where merely > adding an insn is good enough to have the insn included in the region. I really don't like that idea. As it is, these notes are already de facto alpha specific. The only references to these notes: Emitters: except.c: note = emit_note_before (NOTE_INSN_EH_REGION_BEG, except.c: note = emit_note_after (NOTE_INSN_EH_REGION_END, except.c: note = emit_note_before (NOTE_INSN_EH_REGION_BEG, except.c: note = emit_note_after (NOTE_INSN_EH_REGION_END, except.c: note = emit_note_before (NOTE_INSN_EH_REGION_BEG, iter); except.c: note = emit_note_after (NOTE_INSN_EH_REGION_END, last_action_insn); Printers / doc: print-rtl.c: case NOTE_INSN_EH_REGION_BEG: print-rtl.c: case NOTE_INSN_EH_REGION_END: sched-vis.c: case NOTE_INSN_EH_REGION_BEG: sched-vis.c: case NOTE_INSN_EH_REGION_END: insn-notes.def:INSN_NOTE (EH_REGION_BEG) insn-notes.def:INSN_NOTE (EH_REGION_END) doc/rtl.texi:@findex NOTE_INSN_EH_REGION_BEG doc/rtl.texi:@findex NOTE_INSN_EH_REGION_END doc/rtl.texi:@item NOTE_INSN_EH_REGION_BEG doc/rtl.texi:@itemx NOTE_INSN_EH_REGION_END Actual uses of the notes: final.c: case NOTE_INSN_EH_REGION_BEG: final.c: case NOTE_INSN_EH_REGION_END: config/alpha/alpha.c: case NOTE_INSN_EH_REGION_BEG: config/alpha/alpha.c: case NOTE_INSN_EH_REGION_END: FWIW my r43893 reference is based on inspection of toplev.c around that time. See e.g.: http://gcc.gnu.org/viewcvs/gcc/trunk/gcc/toplev.c?revision=43872&view=markup Just before "integrate" (RTL inlining!) there is a call on line 2801 to "convert_from_eh_region_ranges ()" to come from INSN_NOTE based regions to REG_NOTE based regions. Just before shorten_branches, on line 3742, the INSN_NOTE representation is restored via convert_to_eh_region_ranges. The machine-dependent reorg pass runs before it, see line 3689. Continuing the archaeology a bit with "svn blame -r43872 toplev.c": 40924 rth /* Convert from NOTE_INSN_EH_REGION style notes, and do other 40924 rth sorts of eh initialization. Delay this until after the 40924 rth initial rtl dump so that we can see the original nesting. */ 40924 rth convert_from_eh_region_ranges (); and: 40924 rth 40924 rth convert_to_eh_region_ranges (); The commit log for http://gcc.gnu.org/r40924 (Mar 28 2001) is: "IA-64 ABI Exception Handling." The part of alpha EH that depends on the notes must have been been broken since than, more than 12 years. Without anyone noticing... I really, really wouldn't like to keep this code in alpha alive, and with it these REG_EH_REGION notes, for barely (if at all) used ages-old alpha targets...
