https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107919
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Status|NEW |ASSIGNED
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, implementing the existing simplification properly fixes this, but only at
-O1. At -O2 we have
((_277 == 2) AND (_79 == 0))
OR ((NOT (_277 == 0)) AND (NOT (_277 > 2)) AND (NOT (_277 == 2)) AND
(_79 == 0))
OR ((NOT (pretmp_300 == 255)) AND (_277 == 0) AND (NOT (_277 > 2)) AND
(NOT (_277 == 2)) AND (_79 == 0))
and
((_79 == 0))
and more upthread (the CFG is much more complicated). In the above predicate
one can at least see
(_277 == 0) AND (NOT (_277 > 2)) -> (_277 == 0)
(NOT (_277 > 2)) AND (NOT (_277 == 2)) -> (_277 < 2)
(NOT (_277 > 2)) -> (_277 <= 2) (might make !A vs. A more difficult)
kind of simplification opportunities. The above doesn't seem to be the
predicate to simplify in the end though.
Implementing some of these simplifies this to
((_79 == 0) AND (_277 == 2))
OR ((_79 == 0) AND (_277 <= 1) AND (NOT (_277 == 0)))
OR ((_79 == 0) AND (_277 == 0) AND (NOT (pretmp_300 == 255)))
there's
_84 = MEM[(const struct variant
*)this_69].D.41415.D.40957.D.40877.D.40745.D.40631.D.40535._M_index;
_115 = (signed char) _84;
_277 = (long unsigned int) _115;
and
pretmp_300 = MEM[(const struct _Variant_storage *)this_69]._M_index;
with pretmp_300 being unsigned char and _84 the same, so pretmp_300
and _277 are related and (_277 == 0) && !(pretmp_300 == 255) should
simplify to (_277 == 0) which really should make the last two
predicates to collapse(?) and then the rest to a single
((_79 == 0) AND (_277 <= 2)
?
