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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108992] Regression: Branch direction canonicalization leads to pointless tail duplication / CSE/sinking by inverting branch
Date: Thu, 02 Mar 2023 23:39:08 +0000 [thread overview]
Message-ID: <bug-108992-4-1mXH1SR2ti@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108992-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108992
--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #7)
> (In reply to Nikita Kniazev from comment #6)
> > The duplication happens even if I make cond int and compare with any other
> > value
> >
> > void use(int *);
> > void use2(int *);
> >
> > void foo(int * p, int cond)
> > {
> > if (cond == 789) {
> > use(p);
> > }
> > use2(p);
> > }
>
> Yes and no, Yes it does in GCC 7/8 but starting in GCC 9 there is not.
> GCC before GCC 10.x is no longer supported so there is not much we can do
> there.
Well actually I was wrong, the duplication is there but you can see why GCC
does the code duplication really. To also do shrink wrapping.
That is GCC 9+ does not need to setup a stack frame for the != 789 case and
just tail call to use2.
prev parent reply other threads:[~2023-03-02 23:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-02 17:12 [Bug rtl-optimization/108992] New: " nok.raven at gmail dot com
2023-03-02 19:23 ` [Bug rtl-optimization/108992] " pinskia at gcc dot gnu.org
2023-03-02 19:48 ` nok.raven at gmail dot com
2023-03-02 22:37 ` pinskia at gcc dot gnu.org
2023-03-02 22:46 ` [Bug middle-end/108992] " pinskia at gcc dot gnu.org
2023-03-02 22:54 ` pinskia at gcc dot gnu.org
2023-03-02 23:24 ` nok.raven at gmail dot com
2023-03-02 23:35 ` pinskia at gcc dot gnu.org
2023-03-02 23:39 ` pinskia at gcc dot gnu.org [this message]
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