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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/111151] [12/13/14 Regression] Wrong code at -O0 on x86_64-pc-linux-gnu
Date: Mon, 25 Mar 2024 11:01:14 +0000 [thread overview]
Message-ID: <bug-111151-4-nwpFDwyw4D@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-111151-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111151
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #12)
> The following testcase at least reproduces the unsigned multiplication
> issue, but doesn't reproduce the signed multiplication nor division by -1.
> int
> main ()
> {
> unsigned a = (1U + __INT_MAX__) / 2U;
> unsigned b = 1U;
> unsigned c = (a * 2U > b * 2U ? a * 2U : b * 2U) * 2U;
> if (c != 0U)
> __builtin_abort ();
> int d = (-__INT_MAX__ - 1) / 2;
> int e = 10;
> int f = (d * 2 > e * 2 ? d * 2 : e * 2) * 6;
> if (f != 120)
> __builtin_abort ();
> int g = (-__INT_MAX__ - 1) / 2;
> int h = 0;
> int i = (g * 2 > h * 2 ? g * 2 : h * 2) / -1;
> if (i != 0)
> __builtin_abort ();
> }
Ah, the reason it doesn't fail for the f and i cases is that for the signed
type cases, we actually don't create a MIN_EXPR or MAX_EXPR but COND_EXPR which
just compares the vars and performs multiplication only in the COND_EXPR
second/third arguments.
So it is kind of hard trying to make it trigger for the problematic cases where
the recursive calls would extract something.
Will see in full bootstrap/regtest with logging how often does the patch
trigger.
next prev parent reply other threads:[~2024-03-25 11:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-25 6:39 [Bug middle-end/111151] New: " jwzeng at nuaa dot edu.cn
2023-08-25 7:16 ` [Bug middle-end/111151] " rguenth at gcc dot gnu.org
2023-08-25 7:16 ` rguenth at gcc dot gnu.org
2023-08-25 11:51 ` mikpelinux at gmail dot com
2023-08-25 12:27 ` rguenth at gcc dot gnu.org
2023-08-25 12:28 ` rguenth at gcc dot gnu.org
2023-08-25 12:35 ` rguenth at gcc dot gnu.org
2023-08-26 3:27 ` pinskia at gcc dot gnu.org
2024-03-22 13:40 ` law at gcc dot gnu.org
2024-03-22 17:29 ` jakub at gcc dot gnu.org
2024-03-22 17:37 ` jakub at gcc dot gnu.org
2024-03-22 17:41 ` jakub at gcc dot gnu.org
2024-03-22 17:57 ` jakub at gcc dot gnu.org
2024-03-22 18:48 ` jakub at gcc dot gnu.org
2024-03-22 19:15 ` jakub at gcc dot gnu.org
2024-03-25 7:23 ` rguenth at gcc dot gnu.org
2024-03-25 11:01 ` jakub at gcc dot gnu.org [this message]
2024-03-25 12:45 ` rguenth at gcc dot gnu.org
2024-03-26 10:22 ` cvs-commit at gcc dot gnu.org
2024-03-26 10:32 ` [Bug middle-end/111151] [12/13 " jakub at gcc dot gnu.org
2024-03-26 15:43 ` cvs-commit at gcc dot gnu.org
2024-03-30 3:55 ` cvs-commit at gcc dot gnu.org
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