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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug debug/108656] [12/13 Regression] '-fcompare-debug' failure (length) w/ -O2 -fno-ipa-pure-const -fno-tree-dce --param early-inlining-insns=0 since r12-5236
Date: Mon, 06 Feb 2023 10:03:55 +0000 [thread overview]
Message-ID: <bug-108656-4-HAHmUs5xPG@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108656-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108656
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #7)
> (In reply to Richard Biener from comment #6)
> > (In reply to Jakub Jelinek from comment #5)
> > > Created attachment 54412 [details]
> > > gcc13-pr108656.patch
> > >
> > > So shall we fix it like this then?
> >
> > But isn't this the wrong "side"? returns_twice means it is the abnormal
> > control _receiver_, it doesn't perform an abnormal goto itself.
> >
> > stmt_starts_bb_p is correct here, so where does it go wrong?
>
> I think it needs both. The thing is, when it returns the second time, it
> does that again by returning from itself, not through returning from some
> unrelated function.
> Say, if we have pure + returns_twice call and no other call in a function,
> the abnormal edge to the pure + returns_twice call would be optimized away,
> even when the call remains, because there would be no edge from some call to
> the .ABNORMAL_DISPATCHER block.
> __attribute__((pure, returns_twice)) int foo (void);
>
> int
> bar (void)
> {
> for (int i = 0; i < 64; ++i)
> {
> int x = foo ();
> if (x == 26)
> return -42;
> }
> return 42;
> }
> doesn't even have because of this any abnormal edges created.
> Or, if there is some other non-pure call somewhere else, we model through
> the abnormal
> edges that that other call can pass control back to the start of the
> returns_twice call to make it return again.
Ah, but then the issue is that we assume that 'foo' doesn't longjmp,
independent on whether it is returns_twice or not? Can a setjmp ()
function perform a longjmp () to its own context? Would it even appear
as returning twice then? Would calling setjmp in a loop like above
and then jumping to another iteration via longjmp even be valid?
That said, for your example I would think not having any abnormal edges
is correct - there's no frame that could transfer control back to the
returns_twice receiver, no?
next prev parent reply other threads:[~2023-02-06 10:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-03 11:00 [Bug debug/108656] New: [12/13 Regression] '-fcompare-debug' failure (length) w/ -O2 -fno-ipa-pure-const -fno-tree-dce --param early-inlining-insns=0 asolokha at gmx dot com
2023-02-03 11:03 ` [Bug debug/108656] " asolokha at gmx dot com
2023-02-03 11:12 ` [Bug debug/108656] [12/13 Regression] '-fcompare-debug' failure (length) w/ -O2 -fno-ipa-pure-const -fno-tree-dce --param early-inlining-insns=0 since r12-5236 jakub at gcc dot gnu.org
2023-02-03 13:13 ` jakub at gcc dot gnu.org
2023-02-06 7:42 ` rguenth at gcc dot gnu.org
2023-02-06 8:49 ` jakub at gcc dot gnu.org
2023-02-06 9:46 ` rguenth at gcc dot gnu.org
2023-02-06 9:56 ` jakub at gcc dot gnu.org
2023-02-06 10:03 ` rguenth at gcc dot gnu.org [this message]
2023-02-06 10:11 ` jakub at gcc dot gnu.org
2023-02-06 10:14 ` jakub at gcc dot gnu.org
2023-02-06 10:22 ` rguenther at suse dot de
2023-02-06 10:37 ` jakub at gcc dot gnu.org
2023-02-07 11:28 ` rguenther at suse dot de
2023-05-08 12:26 ` [Bug debug/108656] [12/13/14 " rguenth at gcc dot gnu.org
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