http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60116
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
And the place where we first change insn 39 is when simplifying the comparison
that feeds it, in simplify_set:
/* If we are setting CC0 or if the source is a COMPARE, look for the use of
the comparison result and try to simplify it unless we already have used
undobuf.other_insn. */
...
6292 rtx pat = PATTERN (other_insn);
6293 undobuf.other_insn = other_insn;
6294 SUBST (*cc_use, tmp);
So, is it a bug that we've kept REG_DEAD flags there in this case, or just
distribute_notes shouldn't perform:
/* If the register is being set at TEM, see if that is all
TEM is doing. If so, delete TEM. Otherwise, make this
into a REG_UNUSED note instead. Don't delete sets to
global register vars. */
if ((REGNO (XEXP (note, 0)) >= FIRST_PSEUDO_REGISTER
|| !global_regs[REGNO (XEXP (note, 0))])
&& reg_set_p (XEXP (note, 0), PATTERN (tem)))
...
SET_INSN_DELETED (tem);
Dunno how that could ever be safe if from_insn is the former i2 and i3 is a
different insn and tem has bigger luid than from_insn. This code seems to be
in there even in 3.2. Anyway, can somebody more familiar with this have a
look?
