From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by sourceware.org (Postfix) with ESMTPS id 99F78385841A for ; Wed, 7 Sep 2022 15:49:15 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 99F78385841A Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pl1-x629.google.com with SMTP id s14so5408894plr.4 for ; Wed, 07 Sep 2022 08:49:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date; bh=SnUlz9yIEqFxSCFrd2Xo5J9HZ9Kuz6i783Ax7x0K2NA=; b=IiL4bTTsCJXAvz2d+68HDaZYKy4bcBpLeoGmNFKRctr94KmZFjIfMLdkOxCS9W9R7t cVJc0wdnJe7XY9QXfOfudS8WNT33LrDz0CJsEYA1bUOymgRxpB+dGe/efaEQ/ou//iDB fXh53LbuRFKOjSk81G0cagbnRH2fwYlpA40p6Tn9+evjfLhMyr/yWx7R/9b2LSol/t0j 6Vb5d6B+cC7vGWjy50KzxpROsbItrCmB/zSj9dXjlozsYSjpeJnRptypO17VGff+sc+/ lv8ksg2U0d5FoTgZfAblDttm7M1/z9e00KBkdJc4EpXWVcIP52TOh9ccbY90vbZLAEZH 8Msw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date; bh=SnUlz9yIEqFxSCFrd2Xo5J9HZ9Kuz6i783Ax7x0K2NA=; b=JB6+uB6MSeOLFWKESc/N71ouiLPn46uUpnMtIvN8CRy7Je7nJ4jKl28vB/qdQarLPf tZ6uGON//UICO87RJH/HI1329T6dHWuagD4NtGK7zolL6zQ7UeI0xg13D15kMhedGeHi cSaGCB3F/MayXECmwRSFxVmXyc3uS7z5VE3oiPKoGS8k0RKP1Foh8f+rGTquc4somICY 0PedkYur5fHRAZ73AfZU+gaFhvndzGObJEWVl8b+1NkrFLngnXfY8dSyIlkGsMXdrnP7 Rr8DFAxUsAg7nHkmQCgguFG4MmeHQPmxou/QBQhuOnbxru8r21eyvYXhbDNTYu2+xouB D2tg== X-Gm-Message-State: ACgBeo0M3iEore0jTt2gpW2yXVtrkE3aOPgqQrH2tCbuA58GPH3CCu/I vAac1FCBG2nK2iGfHjj5RrnKIjbXr53zVQ== X-Google-Smtp-Source: AA6agR7l5PJ9LSwBm69N3ErXy+LzlklHxbM11FFOGcDfUm7cX6St3b93w3eyXffLvVQM5vUMEO6LAQ== X-Received: by 2002:a17:903:32d2:b0:172:66e4:ba68 with SMTP id i18-20020a17090332d200b0017266e4ba68mr4734757plr.116.1662565754444; Wed, 07 Sep 2022 08:49:14 -0700 (PDT) Received: from [172.31.0.204] (c-73-98-188-51.hsd1.ut.comcast.net. [73.98.188.51]) by smtp.gmail.com with ESMTPSA id f6-20020a170902ce8600b001714e7608fdsm7096934plg.256.2022.09.07.08.49.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Sep 2022 08:49:13 -0700 (PDT) Message-ID: <5b687817-126e-d463-9d88-b3d7d2dad861@gmail.com> Date: Wed, 7 Sep 2022 09:49:12 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.13.0 Subject: Re: [RFC] postreload cse'ing vector constants Content-Language: en-US To: Robin Dapp , gcc-patches@gcc.gnu.org References: <3b0984ef-c532-c29c-732a-1c9b569e134c@linux.ibm.com> <7ecca009-32ac-3b2f-e552-55414300113e@gmail.com> <70a54b9a-30ea-5673-3a41-9585b3abf627@linux.ibm.com> From: Jeff Law In-Reply-To: <70a54b9a-30ea-5673-3a41-9585b3abf627@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,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 9/7/2022 9:33 AM, Robin Dapp wrote: >> Did you did any archeology into this code to see if there was any >> history that might shed light on why it doesn't just using the costing >> models? > This one was buried under some dust :) > > commit 0254c56158b0533600ba9036258c11d377d46adf > Author: John Carr > Date: Wed Jun 10 06:00:50 1998 +0000 > > reload1.c (reload_cse_simplify_operands): Do not call gen_rtx_REG > for each alternative. > > Wed Jun 10 08:56:27 1998 John Carr > * reload1.c (reload_cse_simplify_operands): Do not call > gen_rtx_REG > for each alternative. Do not replace a CONST_INT with a REG > unless > the reg is cheaper. > > From-SVN: r20402 > > Back then we didn't have vectors I suppose but apart from that I don't > see a compelling reason not to unconditionally check costs from this. > It seems like we did even more unconditional replacing before it, > including CONST_INTs. Which is this from the mail archives: https://gcc.gnu.org/pipermail/gcc-patches/1998-June/000308.html I would tend to agree that for equal cost that the constant would be preferred since that should be better from a scheduling/dependency standpoint.   So it seems to me we can drive this purely from a costing standpoint. jef