From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 5A1D43858412; Fri, 22 Mar 2024 18:48:43 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5A1D43858412 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1711133323; bh=D0JE2Hsz+UMVIgpphKgrFsMhnCg7JJREGZ4lfKIUUqA=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Zp/NAIzLr1EKdTLpwE4DFmKFNxZwdNTopv5C8b1dyJ2XOpzbpiYWyhNIzuXbfnwVF CIkCTDd2KPqyDHNdvMJ9stPcR4I66PxBraM6V48RviVitAorwmpFVdJPujbt/rllDU EAKhAK9Fq7m2Iy3KHD0hLssGQXq9VfNOd0YBeL4k= From: "jakub at gcc dot 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: Fri, 22 Mar 2024 18:48:42 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 14.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 12.4 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111151 --- Comment #11 from Jakub Jelinek --- Perhaps --- fold-const.cc.jj8 2024-03-11 22:37:29.000000000 +0100 +++ fold-const.cc 2024-03-22 19:31:44.189686120 +0100 @@ -7104,6 +7104,27 @@ extract_muldiv_1 (tree t, tree c, enum t if (TYPE_UNSIGNED (ctype) !=3D TYPE_UNSIGNED (type)) break; + /* Punt for multiplication altogether. + MAX (1U + INT_MAX, 1U) * 2U is not equivalent to + MAX ((1U + INT_MAX) * 2U, 1U * 2U), the former is + 0U, the latter is 2U. + MAX (INT_MIN / 2, 0) * -2 is not equivalent to + MIN (INT_MIN / 2 * -2, 0 * -2), the former is + well defined 0, the latter invokes UB. + MAX (INT_MIN / 2, 5) * 5 is not equivalent to + MAX (INT_MIN / 2 * 5, 5 * 5), the former is + well defined 25, the latter invokes UB. */ + if (code =3D=3D MULT_EXPR) + break; + /* For division/modulo, punt on c being -1 for MAX, as + MAX (INT_MIN, 0) / -1 is not equivalent to + MIN (INT_MIN / -1, 0 / -1), the former is well defined + 0, the latter invokes UB (or for -fwrapv is INT_MIN). + MIN (INT_MIN, 0) / -1 already invokes UB, so the + transformation won't make it worse. */ + else if (tcode =3D=3D MAX_EXPR && integer_minus_onep (c)) + break; + /* MIN (a, b) / 5 -> MIN (a / 5, b / 5) */ sub_strict_overflow_p =3D false; if ((t1 =3D extract_muldiv (op0, c, code, wide_type, ? Though int main () { unsigned a =3D 1U + __INT_MAX__; unsigned b =3D 1U; unsigned c =3D (a > b ? a : b) * 2U; if (c !=3D 0U) __builtin_abort (); int d =3D (-__INT_MAX__ - 1) / 2; int e =3D 5; int f =3D (d > e ? d : e) * 5; if (f !=3D 25) __builtin_abort (); int g =3D -__INT_MAX__ - 1; int h =3D 0; int i =3D (g > h ? g : h) / -1; if (i !=3D 0) __builtin_abort (); } doesn't seem to be miscompiled, we just don't do that transformation at all even without the patch. Need to tweak such that the min/max arguments are = both something on which extract_muldiv returns non-NULL.=