From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.61]) by sourceware.org (Postfix) with ESMTP id D2575386F455 for ; Thu, 27 Aug 2020 08:35:50 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D2575386F455 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-16-PCIraJdTNbaQ3JcJI05x7g-1; Thu, 27 Aug 2020 04:35:47 -0400 X-MC-Unique: PCIraJdTNbaQ3JcJI05x7g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6A5B0100746C; Thu, 27 Aug 2020 08:35:46 +0000 (UTC) Received: from tucnak.zalov.cz (ovpn-113-115.ams2.redhat.com [10.36.113.115]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 03BD77C863; Thu, 27 Aug 2020 08:35:45 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.15.2/8.15.2) with ESMTP id 07R8ZhM4030614; Thu, 27 Aug 2020 10:35:44 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.15.2/8.15.2/Submit) id 07R8Zhn6030612; Thu, 27 Aug 2020 10:35:43 +0200 Date: Thu, 27 Aug 2020 10:35:42 +0200 From: Jakub Jelinek To: Uros Bizjak , hjl.tools@gmail.com, Michael Matz Cc: gcc-patches@gcc.gnu.org Subject: [PATCH] ia32: Fix alignment of _Atomic fields [PR65146] Message-ID: <20200827083542.GH2961@tucnak> Reply-To: Jakub Jelinek MIME-Version: 1.0 User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Aug 2020 08:35:52 -0000 Hi! For _Atomic fields, lowering the alignment of long long or double etc. fields on ia32 is undesirable, because then one really can't perform atomic operations on those using cmpxchg8b. The following patch stops lowering the alignment in fields for _Atomic types (the x86_field_alignment change) and for -mpreferred-stack-boundary=2 also ensures we don't misalign _Atomic long long etc. automatic variables (the ix86_{local,minimum}_alignment changes). Not sure about iamcu_alignment change, I know next to nothing about IA MCU, but unless it doesn't have cmpxchg8b instruction, it would surprise me if we don't want to do it as well. clang apparently doesn't lower the field alignment for _Atomic. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2020-08-27 Jakub Jelinek PR target/65146 * config/i386/i386.c (iamcu_alignment): Don't decrease alignment for TYPE_ATOMIC types. (ix86_local_alignment): Likewise. (ix86_minimum_alignment): Likewise. (x86_field_alignment): Likewise, and emit a -Wpsabi diagnostic for it. * gcc.target/i386/pr65146.c: New test. --- gcc/config/i386/i386.c.jj 2020-08-24 10:00:01.321258451 +0200 +++ gcc/config/i386/i386.c 2020-08-26 19:19:11.834297395 +0200 @@ -16487,7 +16487,11 @@ iamcu_alignment (tree type, int align) /* Intel MCU psABI specifies scalar types > 4 bytes aligned to 4 bytes. */ - mode = TYPE_MODE (strip_array_types (type)); + type = strip_array_types (type); + if (TYPE_ATOMIC (type)) + return align; + + mode = TYPE_MODE (type); switch (GET_MODE_CLASS (mode)) { case MODE_INT: @@ -16644,7 +16648,8 @@ ix86_local_alignment (tree exp, machine_ && align == 64 && ix86_preferred_stack_boundary < 64 && (mode == DImode || (type && TYPE_MODE (type) == DImode)) - && (!type || !TYPE_USER_ALIGN (type)) + && (!type || (!TYPE_USER_ALIGN (type) + && !TYPE_ATOMIC (strip_array_types (type)))) && (!decl || !DECL_USER_ALIGN (decl))) align = 32; @@ -16757,7 +16762,8 @@ ix86_minimum_alignment (tree exp, machin /* Don't do dynamic stack realignment for long long objects with -mpreferred-stack-boundary=2. */ if ((mode == DImode || (type && TYPE_MODE (type) == DImode)) - && (!type || !TYPE_USER_ALIGN (type)) + && (!type || (!TYPE_USER_ALIGN (type) + && !TYPE_ATOMIC (strip_array_types (type)))) && (!decl || !DECL_USER_ALIGN (decl))) { gcc_checking_assert (!TARGET_STV); @@ -20293,11 +20299,30 @@ x86_field_alignment (tree type, int comp return computed; if (TARGET_IAMCU) return iamcu_alignment (type, computed); - mode = TYPE_MODE (strip_array_types (type)); + type = strip_array_types (type); + mode = TYPE_MODE (type); if (mode == DFmode || mode == DCmode || GET_MODE_CLASS (mode) == MODE_INT || GET_MODE_CLASS (mode) == MODE_COMPLEX_INT) - return MIN (32, computed); + { + if (TYPE_ATOMIC (type) && computed > 32) + { + static bool warned; + + if (!warned && warn_psabi) + { + const char *url + = CHANGES_ROOT_URL "gcc-11/changes.html#ia32_atomic"; + + warned = true; + inform (input_location, "the alignment of %<_Atomic %T%> " + "fields changed in %{GCC 11.1%}", + TYPE_MAIN_VARIANT (type), url); + } + } + else + return MIN (32, computed); + } return computed; } --- gcc/testsuite/gcc.target/i386/pr65146.c.jj 2020-08-26 19:25:27.720023020 +0200 +++ gcc/testsuite/gcc.target/i386/pr65146.c 2020-08-26 19:28:24.982535651 +0200 @@ -0,0 +1,12 @@ +/* PR target/65146 */ +/* { dg-do compile } */ +/* { dg-options "-Wno-psabi" } */ + +struct A { char a; _Atomic long long b; }; +struct B { char a; _Atomic double b; }; +struct C { char a; _Atomic long long b[2]; }; +struct D { char a; _Atomic double b[2]; }; +extern int a[__builtin_offsetof (struct A, b) == 8 ? 1 : -1]; +extern int b[__builtin_offsetof (struct B, b) == 8 ? 1 : -1]; +extern int c[__builtin_offsetof (struct C, b) == 8 ? 1 : -1]; +extern int d[__builtin_offsetof (struct D, b) == 8 ? 1 : -1]; Jakub