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From: "tnfchris at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111950] [14 Regression] ICE in compute_live_loop_exits, at tree-ssa-loop-manip.cc:250 since r14-4786-gd118738e71c
Date: Fri, 27 Oct 2023 16:02:53 +0000 [thread overview]
Message-ID: <bug-111950-4-qqVT3Ln87J@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-111950-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111950
--- Comment #4 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
> turning c_I_lsm.18_38 into a fully invariant reduction def which likely isn't
supported - we had bugs here in the past with not relevant but live stmts.
But if-conversion also performs the (now valid) hoisting, this is maybe
why it was triggered by that rev.
Ah yeah this is something different from what I just fixed.
Indeed, this causes find_guard_arg to no longer find the tie to the original
PHI.
It's trying to match
# c_I_lsm.18_60 = PHI <a.3_23(33), 1(36)>
and
# c_I_lsm.18_79 = PHI <c_I_lsm.18_60(35)>
after it adds the edge. Normally loop invariant values are left in the the
guard block for this. In this case we've left
# c_I_lsm.18_65 = PHI <c_I_lsm.18_38(11)>
Normally instead of
# c_I_lsm.18_60 = PHI <a.3_23(33), 1(36)>
we'd find c_I_lsm.18_65 here. The value is as you mentioned loop invariant.
but since c_I_lsm.18_38 is no longer a PHI node the link was broken.
I don't think we can really recover this in the vectorizer can we?
Would the proper fix perhaps be to have ifconvert fully convert things?
It seems to have missed that
# c_I_lsm.18_60 = PHI <a.3_23(33), 1(36)>
is just
c_I_lsm.18_60 = _58 ? 1 : a.3_23;
that would prevent the PHI node confusion
next prev parent reply other threads:[~2023-10-27 16:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 7:15 [Bug tree-optimization/111950] New: " shaohua.li at inf dot ethz.ch
2023-10-24 7:50 ` [Bug tree-optimization/111950] [14 Regression] " rguenth at gcc dot gnu.org
2023-10-27 14:14 ` rguenth at gcc dot gnu.org
2023-10-27 14:29 ` tnfchris at gcc dot gnu.org
2023-10-27 16:02 ` tnfchris at gcc dot gnu.org [this message]
2023-11-03 12:02 ` rguenth at gcc dot gnu.org
2023-11-03 13:27 ` rguenth at gcc dot gnu.org
2023-11-03 14:14 ` rguenth at gcc dot gnu.org
2023-11-03 14:57 ` rguenth at gcc dot gnu.org
2023-11-03 15:58 ` tnfchris at gcc dot gnu.org
2023-11-06 9:51 ` rguenth at gcc dot gnu.org
2023-11-06 13:16 ` cvs-commit at gcc dot gnu.org
2023-11-06 13:18 ` rguenth at gcc dot gnu.org
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