From patchwork Wed Aug 14 09:53:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pierre-Marie de Rodat X-Patchwork-Id: 1146902 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=gcc.gnu.org (client-ip=209.132.180.131; helo=sourceware.org; envelope-from=gcc-patches-return-506914-incoming=patchwork.ozlabs.org@gcc.gnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=adacore.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=gcc.gnu.org header.i=@gcc.gnu.org header.b="dA+m1j1g"; dkim-atps=neutral Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 467lMp2zYdz9sNC for ; Wed, 14 Aug 2019 19:56:06 +1000 (AEST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:date :from:to:cc:subject:message-id:mime-version:content-type; q=dns; s=default; b=m3ujZ+PYD/3LzWBA0QjPwNKcOgEKBG7HH7Oqv8wkZZj9jJVxUo z1aZ8BkLobdXiZa8367LAbmIno5KYvlIqgLOLS4nV1xZDdXfdDs0UOY+EdrEqpmE yFnooVjlMokhyMFLulAJDnKClJF5bQbbcGUpnUWN59esJfgw962IbwS9g= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:date :from:to:cc:subject:message-id:mime-version:content-type; s= default; bh=a/ZHF0g7kWrURHlRQ7ctKcgkpYg=; b=dA+m1j1gveq+NTSkQw6Z 9WvYjFAOqRIMZ60JcTAkPjPAZfmwrILQYFGwHyAUBpHV+To4bWQ6wKQutepn1NIR SF2dwQgYpN4sske5vEVyOnZPi1kWBZMB0OgPLbEgdFD4aNlkzbT6fMJgQymDTL8U JUNEwdkAGUNblhCrGl/N8K8= Received: (qmail 76064 invoked by alias); 14 Aug 2019 09:53:35 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Delivered-To: mailing list gcc-patches@gcc.gnu.org Received: (qmail 74655 invoked by uid 89); 14 Aug 2019 09:53:24 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-16.1 required=5.0 tests=BAYES_00, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, SPF_NEUTRAL autolearn=ham version=3.3.1 spammy=Manual, rounded, ASIS X-HELO: eggs.gnu.org Received: from eggs.gnu.org (HELO eggs.gnu.org) (209.51.188.92) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 14 Aug 2019 09:53:22 +0000 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hxpy1-0007xC-Er for gcc-patches@gcc.gnu.org; Wed, 14 Aug 2019 05:53:19 -0400 Received: from rock.gnat.com ([205.232.38.15]:55212) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hxpy1-0007wc-7X for gcc-patches@gcc.gnu.org; Wed, 14 Aug 2019 05:53:17 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 2A8A056068; Wed, 14 Aug 2019 05:53:15 -0400 (EDT) Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id CVmACRuQNkc5; Wed, 14 Aug 2019 05:53:15 -0400 (EDT) Received: from tron.gnat.com (tron.gnat.com [IPv6:2620:20:4000:0:46a8:42ff:fe0e:e294]) by rock.gnat.com (Postfix) with ESMTP id EB6EE5610D; Wed, 14 Aug 2019 05:53:13 -0400 (EDT) Received: by tron.gnat.com (Postfix, from userid 4862) id EA3A66CC; Wed, 14 Aug 2019 05:53:13 -0400 (EDT) Date: Wed, 14 Aug 2019 05:53:13 -0400 From: Pierre-Marie de Rodat To: gcc-patches@gcc.gnu.org Cc: Bob Duff Subject: [Ada] Alignment may be specified as zero Message-ID: <20190814095313.GA52437@adacore.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 205.232.38.15 X-IsSubscribed: yes An Alignment clause or an aspect_specification for Alignment may be specified as 0, which is treated the same as 1. Tested on x86_64-pc-linux-gnu, committed on trunk 2019-08-14 Bob Duff gcc/ada/ * sem_ch13.adb (Get_Alignment_Value): Return 1 for Alignment 0, and do not give an error. * doc/gnat_rm/representation_clauses_and_pragmas.rst: Update the corresponding documentation. * gnat_rm.texi: Regenerate. gcc/testsuite/ * gnat.dg/alignment15.adb: New testcase. --- gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst +++ gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst @@ -30,9 +30,11 @@ Alignment Clauses .. index:: Alignment Clause -GNAT requires that all alignment clauses specify a power of 2, and all -default alignments are always a power of 2. The default alignment -values are as follows: +GNAT requires that all alignment clauses specify 0 or a power of 2, and +all default alignments are always a power of 2. Specifying 0 is the +same as specifying 1. + +The default alignment values are as follows: * *Elementary Types*. @@ -610,23 +612,23 @@ alignment of the type (this is true for all types). In some cases the end record; -On a typical 32-bit architecture, the X component will occupy four bytes -and the Y component will occupy one byte, for a total of 5 bytes. As a -result ``R'Value_Size`` will be 40 (bits) since this is the minimum size -required to store a value of this type. For example, it is permissible -to have a component of type R in an array whose component size is -specified to be 40 bits. - -However, ``R'Object_Size`` will be 64 (bits). The difference is due to -the alignment requirement for objects of the record type. The X -component will require four-byte alignment because that is what type -Integer requires, whereas the Y component, a Character, will only -require 1-byte alignment. Since the alignment required for X is the -greatest of all the components' alignments, that is the alignment -required for the enclosing record type, i.e., 4 bytes or 32 bits. As -indicated above, the actual object size must be rounded up so that it is -a multiple of the alignment value. Therefore, 40 bits rounded up to the -next multiple of 32 yields 64 bits. +On a typical 32-bit architecture, the X component will occupy four bytes +and the Y component will occupy one byte, for a total of 5 bytes. As a +result ``R'Value_Size`` will be 40 (bits) since this is the minimum size +required to store a value of this type. For example, it is permissible +to have a component of type R in an array whose component size is +specified to be 40 bits. + +However, ``R'Object_Size`` will be 64 (bits). The difference is due to +the alignment requirement for objects of the record type. The X +component will require four-byte alignment because that is what type +Integer requires, whereas the Y component, a Character, will only +require 1-byte alignment. Since the alignment required for X is the +greatest of all the components' alignments, that is the alignment +required for the enclosing record type, i.e., 4 bytes or 32 bits. As +indicated above, the actual object size must be rounded up so that it is +a multiple of the alignment value. Therefore, 40 bits rounded up to the +next multiple of 32 yields 64 bits. For all other types, the ``Object_Size`` and ``Value_Size`` are the same (and equivalent to the RM attribute ``Size``). --- gcc/ada/gnat_rm.texi +++ gcc/ada/gnat_rm.texi @@ -21,7 +21,7 @@ @copying @quotation -GNAT Reference Manual , Jul 31, 2019 +GNAT Reference Manual , Aug 01, 2019 AdaCore @@ -18369,9 +18369,11 @@ and this section describes the additional capabilities provided. @geindex Alignment Clause -GNAT requires that all alignment clauses specify a power of 2, and all -default alignments are always a power of 2. The default alignment -values are as follows: +GNAT requires that all alignment clauses specify 0 or a power of 2, and +all default alignments are always a power of 2. Specifying 0 is the +same as specifying 1. + +The default alignment values are as follows: @itemize * --- gcc/ada/sem_ch13.adb +++ gcc/ada/sem_ch13.adb @@ -11509,7 +11509,7 @@ package body Sem_Ch13 is if Align = No_Uint then return No_Uint; - elsif Align <= 0 then + elsif Align < 0 then -- This error is suppressed in ASIS mode to allow for different ASIS -- back ends or ASIS-based tools to query the illegal clause. @@ -11520,6 +11520,11 @@ package body Sem_Ch13 is return No_Uint; + -- If Alignment is specified to be 0, we treat it the same as 1 + + elsif Align = 0 then + return Uint_1; + else for J in Int range 0 .. 64 loop declare --- /dev/null new file mode 100644 +++ gcc/testsuite/gnat.dg/alignment15.adb @@ -0,0 +1,17 @@ +-- { dg-compile } + +procedure Alignment15 is + type T0 is record + X : Integer; + end record; + for T0'Alignment use 0; + + type T00 is record + X : Integer; + end record with Alignment => 0; + + Dummy0 : T0; + Dummy00 : T00; +begin + null; +end;