From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id D1A9C385829E for ; Fri, 16 Feb 2024 14:31:19 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org D1A9C385829E Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org D1A9C385829E Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1708093881; cv=none; b=ZtOvEy87vX8V5PKejdf46gmO5W/hDpVjq38UPVl5RdjUSlWAefQjRRTHDwXxJBayfxPWGPrAJ5x3y4M3UfS1tw5fZp+1qjeHYB6+GYYWZrph4YoJTxm31UWJsK3ysIEUZdjeYzFjFOxyp0Dqmjma7S9xnpt8/CcjHrG9lPEjT8M= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1708093881; c=relaxed/simple; bh=grLLATNpn/lL7GeLLpwHt4qOzz+UWpMwkmJJrzTxqVI=; h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version; b=n6m+QP5EVV/n8Xq8odVN7abMOf7HghbDN8/4eTM9S4hgm0tPCTfx1YykvCacw0Fl3xcFOWIb4kcBQiXLW2Z7UltYmefdsvMbuNumtLOlyHNIXsvH1WhujHK9wM3dXWYWx3iO/vgGD9FkZyCdJNeqyAaOlZ2xpR1qt+qkeCjOyZ4= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708093879; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=0TVzDJ8kx9HX21RZOReRTRwyKOU3vm0Yf1HIX1QdDRk=; b=FO0pdQIHFECdpKhV+5P8OmX5FCxoZqH94Pm27YraB6AKV2tQU2Gi1gAY+GzciCLbOOHobe 6kJ/fSAyKd55pPMG4Sfpbq/nlvm3g8IuHYxtWw+SsqPiTKb/2QR5cPEFHNPzmQwxFIh8vU v2WxJIvNfoM/pIc5aTa/sDhNRWJEVZQ= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-416-k2O6eE8uOBm0K1NmCwuZAA-1; Fri, 16 Feb 2024 09:31:13 -0500 X-MC-Unique: k2O6eE8uOBm0K1NmCwuZAA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5A0EB1C0BB4F; Fri, 16 Feb 2024 14:31:13 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.8]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0E1911C060B1; Fri, 16 Feb 2024 14:31:11 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 41GEV8bi165133 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 16 Feb 2024 15:31:09 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 41GEV7b3165132; Fri, 16 Feb 2024 15:31:07 +0100 Date: Fri, 16 Feb 2024 15:31:06 +0100 From: Jakub Jelinek To: "Maciej W. Rozycki" Cc: Segher Boessenkool , Paul Koning , gcc-patches@gcc.gnu.org Subject: Re: [PATCH] Turn on LRA on all targets Message-ID: Reply-To: Jakub Jelinek References: <283c45ca085ced958cbce6e64331252c83a5899f.1682268126.git.segher@kernel.crashing.org> <20230423203328.GL19790@gate.crashing.org> <2A759520-2D62-472E-A97F-35E09B6E50F5@comcast.net> <20240216134748.GF19790@gate.crashing.org> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.8 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_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Fri, Feb 16, 2024 at 02:23:54PM +0000, Maciej W. Rozycki wrote: > On Fri, 16 Feb 2024, Segher Boessenkool wrote: > > > > Conversely no heuristics is required to unwind VAX frames, because they > > > are fixed in layout by hardware, fully self-described, and with the > > > hardware frame pointer always available. > > > > The downside of the VAX situation of course is that the compiler has no > > freedom to optimise the frame and *logue code at all, let alone well. > > This may not matter so much on narrow ucoded in-order machines, there > > are different balances there :-) > > There is no function prologue to optimise in the VAX case, because all > the frame setup has already been made by the CALLS instruction itself in > the caller. The first machine instruction of the callee is technically > already past the "prologue". And then RET serves as the whole function > "epilogue". So, what is the problem with DWARF unwinding? Just make sure to emit appropriate instructions describing the saving of the corresponding registers at specific points based on CFA at the start of the function (so that it appears in CIE instructions) and that should be all that is needed, no? Jakub