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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/111151] [12/13 Regression] Wrong code at -O0 on x86_64-pc-linux-gnu Date: Sat, 30 Mar 2024 03:55:40 +0000 [thread overview] Message-ID: <bug-111151-4-rL7PmLLij5@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 #18 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-13 branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:71a1ccc0378f18dfecb54bfa453c0334fbb76675 commit r13-8523-g71a1ccc0378f18dfecb54bfa453c0334fbb76675 Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Mar 26 11:21:38 2024 +0100 fold-const: Punt on MULT_EXPR in extract_muldiv MIN/MAX_EXPR case [PR111151] As I've tried to explain in the comments, the extract_muldiv_1 MIN/MAX_EXPR optimization is wrong for code == MULT_EXPR. If the multiplication is done in unsigned type or in signed type with -fwrapv, it is fairly obvious that max (a, b) * c in many cases isn't equivalent to max (a * c, b * c) (or min if c is negative) due to overflows, but even for signed with undefined overflow, the optimization could turn something without UB in it (where say a * c invokes UB, but max (or min) picks the other operand where b * c doesn't). As for division/modulo, I think it is in most cases safe, except if the problematic INT_MIN / -1 case could be triggered, but we can just punt for MAX_EXPR because for MIN_EXPR if one operand is INT_MIN, we'd pick that operand already. It is just for completeness, match.pd already has an optimization which turns x / -1 into -x, so the division by zero is mostly theoretical. That is also why in the testcase the i case isn't actually miscompiled without the patch, while the c and f cases are. 2024-03-26 Jakub Jelinek <jakub@redhat.com> PR middle-end/111151 * fold-const.cc (extract_muldiv_1) <case MAX_EXPR>: Punt for MULT_EXPR altogether, or for MAX_EXPR if c is -1. * gcc.c-torture/execute/pr111151.c: New test. (cherry picked from commit c4f2c84e8fa369856aee76679590eb613724bfb0)
prev parent reply other threads:[~2024-03-30 3:55 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-08-25 6:39 [Bug middle-end/111151] New: [12/13/14 " 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 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 [this message]
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