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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/108789] __builtin_(add|mul|sub)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments Date: Tue, 11 Jun 2024 10:39:04 +0000 [thread overview] Message-ID: <bug-108789-4-hnosqu3ehD@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-108789-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108789 --- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:91a371254494934e191e3060ae2a86905eb4b2b2 commit r12-10532-g91a371254494934e191e3060ae2a86905eb4b2b2 Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Jun 4 12:28:01 2024 +0200 builtins: Force SAVE_EXPR for __builtin_{add,sub,mul}_overflow [PR108789] The following testcase is miscompiled, because we use save_expr on the .{ADD,SUB,MUL}_OVERFLOW call we are creating, but if the first two operands are not INTEGER_CSTs (in that case we just fold it right away) but are TREE_READONLY/!TREE_SIDE_EFFECTS, save_expr doesn't actually create a SAVE_EXPR at all and so we lower it to *arg2 = REALPART_EXPR (.ADD_OVERFLOW (arg0, arg1)), \ IMAGPART_EXPR (.ADD_OVERFLOW (arg0, arg1)) which evaluates the ifn twice and just hope it will be CSEd back. As *arg2 aliases *arg0, that is not the case. The builtins are really never const/pure as they store into what the third arguments points to, so after handling the INTEGER_CST+INTEGER_CST case, I think we should just always use SAVE_EXPR. Just building SAVE_EXPR by hand and setting TREE_SIDE_EFFECTS on it doesn't work, because c_fully_fold optimizes it away again, so the following patch marks the ifn calls as TREE_SIDE_EFFECTS (but doesn't do it for the __builtin_{add,sub,mul}_overflow_p case which were designed for use especially in constant expressions and don't really evaluate the realpart side, so we don't really need a SAVE_EXPR in that case). 2024-06-04 Jakub Jelinek <jakub@redhat.com> PR middle-end/108789 * builtins.cc (fold_builtin_arith_overflow): For ovf_only, don't call save_expr and don't build REALPART_EXPR, otherwise set TREE_SIDE_EFFECTS on call before calling save_expr. * gcc.c-torture/execute/pr108789.c: New test. (cherry picked from commit b8e28381cb5c0cddfe5201faf799d8b27f5d7d6c)
next prev parent reply other threads:[~2024-06-11 10:39 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-02-14 17:51 [Bug c/108789] New: __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const dpejesh at yahoo dot com 2023-02-14 17:53 ` [Bug middle-end/108789] " pinskia at gcc dot gnu.org 2023-11-09 6:29 ` [Bug middle-end/108789] __builtin_(add|mul)_overflow methods generate duplicate operations if both operands are const which in turn causes wrong code due to overlapping arguments pinskia at gcc dot gnu.org 2024-06-03 13:56 ` pinskia at gcc dot gnu.org 2024-06-03 13:59 ` [Bug middle-end/108789] __builtin_(add|mul|sub)_overflow " pinskia at gcc dot gnu.org 2024-06-03 15:35 ` jakub at gcc dot gnu.org 2024-06-04 10:28 ` cvs-commit at gcc dot gnu.org 2024-06-04 10:33 ` jakub at gcc dot gnu.org 2024-06-04 14:26 ` cvs-commit at gcc dot gnu.org 2024-06-11 6:17 ` cvs-commit at gcc dot gnu.org 2024-06-11 10:39 ` cvs-commit at gcc dot gnu.org [this message] 2024-06-11 10:56 ` jakub at gcc dot gnu.org 2024-06-20 13:23 ` cvs-commit at gcc dot gnu.org 2024-06-20 13:25 ` jakub at gcc dot gnu.org
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