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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/96674] Failure to optimize combination of comparisons to dec+compare
Date: Tue, 12 Jan 2021 23:45:39 +0000 [thread overview]
Message-ID: <bug-96674-4-Cf45PRE6Nq@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-96674-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96674
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
/* x < y || x == XXX_MIN --> x <= y - 1 */
(simplify
(bit_ior (eq @1 min_value) (lt @0 @1))
(if (INTEGRAL_TYPE_P (TREE_TYPE (@1))
&& TYPE_OVERFLOW_WRAPS (TREE_TYPE (@1)))
(le @0 (minus @1 { build_int_cst (TREE_TYPE (@1), 1); }))))
The comment doesn't match what the simplification implements (x == XXX_MIN
should be y == XXX_MIN).
Furthermore, bit_ior is commutative and for the optimization no specific order
is needed, so probably bit_ior:c is needed. Also, the optimization doesn't
seem to be worth if either eq or lt has multiple uses, so both should have :s
suffixes. When x < y || y == min can be simplified into x <= y - 1, can't
its negation, i.e. x >= y && y != min be simplified into x > y - 1 ?
And agree on the noipa attribute, most of the tests you're citing just predate
the noipa attribute. We had noinline for many years, later added noclone and
have been using noinline, noclone and when we started adding further IPA
optimizations, noipa has been added.
next prev parent reply other threads:[~2021-01-12 23:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-18 10:30 [Bug tree-optimization/96674] New: " gabravier at gmail dot com
2020-08-25 10:45 ` [Bug tree-optimization/96674] " rguenth at gcc dot gnu.org
2020-08-31 0:58 ` pinskia at gcc dot gnu.org
2021-01-11 22:53 ` erozen at microsoft dot com
2021-01-12 11:52 ` gabravier at gmail dot com
2021-01-12 23:12 ` erozen at microsoft dot com
2021-01-12 23:34 ` gabravier at gmail dot com
2021-01-12 23:45 ` jakub at gcc dot gnu.org [this message]
2021-01-14 21:06 ` erozen at microsoft dot com
2021-01-14 21:07 ` erozen at microsoft dot com
2021-01-14 21:30 ` ubizjak at gmail dot com
2021-01-15 0:32 ` erozen at microsoft dot com
2021-01-20 15:32 ` cvs-commit at gcc dot gnu.org
2021-06-02 18:59 ` law at gcc dot gnu.org
2021-09-17 6:44 ` pinskia at gcc dot gnu.org
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