From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 027BA384F4A0; Thu, 15 Feb 2024 15:17:51 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 027BA384F4A0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1708010272; bh=ySovo+0gIH80j4FwYe0n+GKqRrAeeobbomRN9FophZc=; h=From:To:Subject:Date:In-Reply-To:References:From; b=hBrHZEp7vJHeNT/crrh0eAU12q5jMJkZQT0hQjr3YvI2k4w0IPlrYTlJAvFSpmJeq ydAfXn7saq+0BDQiP7kpQFTK9Yc9c08oZX8A22M5yRoXny1TjUBhfuNTmnkkmpAJMK gxs30VltiWu33YVU4Xzu9jngvkz9lk2wTUDilkXM= From: "cvs-commit at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/113921] Output register of an "asm volatile goto" is incorrectly clobbered/discarded Date: Thu, 15 Feb 2024 15:17:51 +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: 11.4.0 X-Bugzilla-Keywords: inline-asm X-Bugzilla-Severity: normal X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: ASSIGNED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: jakub at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- 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=3D113921 --- Comment #13 from GCC Commits --- The releases/gcc-12 branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:ba09da9787e8db8903b2b0f7c647c0d7af68bb74 commit r12-10158-gba09da9787e8db8903b2b0f7c647c0d7af68bb74 Author: Jakub Jelinek Date: Thu Feb 15 15:53:01 2024 +0100 expand: Fix handling of asm goto outputs vs. PHI argument adjustments [PR113921] The Linux kernel and the following testcase distilled from it is miscompiled, because tree-outof-ssa.cc (eliminate_phi) emits some fixups on some of the edges (but doesn't commit edge insertions). Later expand_asm_stmt emits further instructions on the same edge. Now the problem is that expand_asm_stmt uses insert_insn_on_edge to add its own fixups, but that function appends to the existing sequence on the edge if any. And the bug triggers when the fixup sequence emitted by eliminate_phi uses a pseudo which the fixup sequence emitted by expand_asm_stmt later on sets. So, we end up with (set (reg A) (asm_operands ...)) and on one of the edges queued sequence (set (reg C) (reg B)) // added by eliminate_phi (set (reg B) (reg A)) // added by expand_asm_stmt That is wrong, what we emit by expand_asm_stmt needs to be as close to the asm_operands as possible (they aren't known until expand_asm_stmt is called, the PHI fixup code assumes it is reg B which holds the right value) and the PHI adjustments need to be done after it. So, the following patch introduces a prepend_insn_to_edge function and uses it from expand_asm_stmt, so that we queue (set (reg B) (reg A)) // added by expand_asm_stmt (set (reg C) (reg B)) // added by eliminate_phi instead and so the value from the asm_operands output propagates correc= tly to the PHI result. 2024-02-15 Jakub Jelinek PR middle-end/113921 * cfgrtl.h (prepend_insn_to_edge): New declaration. * cfgrtl.cc (insert_insn_on_edge): Clarify behavior in function comment. (prepend_insn_to_edge): New function. * cfgexpand.cc (expand_asm_stmt): Use prepend_insn_to_edge inst= ead of insert_insn_on_edge. * gcc.target/i386/pr113921.c: New test. (cherry picked from commit 2b4efc5db2aedb59196987300e14951d08cd7106)=