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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 4D7DD3853567 for ; Mon, 20 Feb 2023 15:17:40 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 4D7DD3853567 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676906259; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VHdXOo3lUQA3GzYXaKbdXgOvidHIEJc3hJxwS7i88BU=; b=cVk1Ay11zC9PvdS6rHImLdIw35Vjf+dfoT3xX50epyN/q0kNq05GMv8I9tW9KNmfQRn2Yp trApoB2Zj7apfi8Pz9qV32uXkA+g3KS4MjOCxCGfw06YEK0yNAHZhJNg7/TpAy84f5xLkQ oZYo50Ebj4wN5rNBWcnpkoOiDcE+nKY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-625-pUfUvGkxNYab8OZCl0W4MQ-1; Mon, 20 Feb 2023 10:17:38 -0500 X-MC-Unique: pUfUvGkxNYab8OZCl0W4MQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 943D985CCE4; Mon, 20 Feb 2023 15:17:37 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 598821121314; Mon, 20 Feb 2023 15:17:37 +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 31KFHXJ01814920 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 20 Feb 2023 16:17:33 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 31KFHRD41814919; Mon, 20 Feb 2023 16:17:27 +0100 Date: Mon, 20 Feb 2023 16:17:26 +0100 From: Jakub Jelinek To: Qing Zhao Cc: "rguenther@suse.de" , "gcc-patches@gcc.gnu.org" Subject: Re: [PATCH] Fixing PR107411 Message-ID: Reply-To: Jakub Jelinek References: <20230217222603.2485714-1-qing.zhao@oracle.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_NUMSUBJECT,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=no 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 Mon, Feb 20, 2023 at 03:04:51PM +0000, Qing Zhao via Gcc-patches wrote: > > > > On Feb 17, 2023, at 5:35 PM, Jakub Jelinek wrote: > > > > On Fri, Feb 17, 2023 at 10:26:03PM +0000, Qing Zhao via Gcc-patches wrote: > >> + else if (!DECL_NAME (lhs_var)) > >> + { > >> + char *lhs_var_name_str > >> + = xasprintf ("D.%u", DECL_UID (lhs_var)); > > > > Why xasprintf? > > Just emulated the code in “gimple_add_init_for_auto_var” without thinking too much. -:) > > D.%u can be sprintfed into a fixed size automatic buffer, > > say 3 + (HOST_BITS_PER_INT + 2) / 3 would be a good upper bound for the size > > of the buffer. Then you don't need to free it... > > xasprintf is "like a sprintf but provided a pointer to malloc’d storage (without fail)”. If free the pointer properly, then it should be okay, right? > In addition to “no need to free”, what other benefit to use sprintf other than xasprintf? xasprintf+free being significantly slower, exactly because it needs to malloc and free later, where both are fairly expensive functions. The glibc asprintf for short strings like the above uses a ~ 200 byte static buffer, stores in there, later mallocs the needed amount of memory and copies it there (so again, another waste because the string needs to be copied around), while for longer it can do perhaps many allocations and realloc at the end to the right size. The libiberty function actually performs the printing twice, once without writing result anywhere to compute size, then malloc, then again into the malloced buffer. Jakub