From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19A4EC4320A for ; Thu, 19 Aug 2021 13:54:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EF8BD608FE for ; Thu, 19 Aug 2021 13:54:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240237AbhHSNzZ (ORCPT ); Thu, 19 Aug 2021 09:55:25 -0400 Received: from smtp-relay-canonical-0.canonical.com ([185.125.188.120]:43728 "EHLO smtp-relay-canonical-0.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238564AbhHSNzX (ORCPT ); Thu, 19 Aug 2021 09:55:23 -0400 Received: from [10.172.193.212] (1.general.cking.uk.vpn [10.172.193.212]) (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 smtp-relay-canonical-0.canonical.com (Postfix) with ESMTPSA id 887473F047; Thu, 19 Aug 2021 13:54:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical.com; s=20210705; t=1629381280; bh=qyVfAD70OnSmTL6T7q8M2kzukbFXgV7pw1ZsTuvCXvs=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=wWEiWs+2aX1SyglCKtylm23g+9P2rxsF9XgIkRI3Ourd3b0qQKSrkO4ltWyqoEdRe 1JnX7dXu6j+Ctid2QwajdijkHBDok0orq+B+vTx99m6KEjxlQko8WdJPbyTZBLEmp2 DUTEuOrLaxRKltOPW+IHwqzXu00bwBcPtABBn/Ou5j5cnvQ6x+B5G/+r8kVde9KRrG AEurGqItIBuoNkK/CSSO1XyflExM+iS/FeCwnmuGRgvj6tbNtnA1ZPF/qZ5ONKumnA MXx9auJcSe/E2UR7j2tPHUfXmbdx8XowwBy2UYMAJ1jT/TI0j7Xtqape/pNr6gF+xb NRIv4pQMEEV3Q== Subject: Re: [PATCH] drm/bridge/tc358767: make the array ext_div static const, makes object smaller To: Joe Perches , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210819133839.10745-1-colin.king@canonical.com> <0a2ea4e54d7bfd61b45cc070eee6b62e8da82190.camel@perches.com> From: Colin Ian King Message-ID: <913b96bc-f5c4-1a26-c5f7-70a9d0ab3f53@canonical.com> Date: Thu, 19 Aug 2021 14:54:40 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <0a2ea4e54d7bfd61b45cc070eee6b62e8da82190.camel@perches.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/08/2021 14:51, Joe Perches wrote: > On Thu, 2021-08-19 at 14:38 +0100, Colin King wrote: >> From: Colin Ian King >> >> Don't populate the array ext_div on the stack but instead it >> static const. Makes the object code smaller by 118 bytes: >> >> Before: >>    text data bss dec hex filename >>   39449 17500 128 57077 def5 ./drivers/gpu/drm/bridge/tc358767.o >> >> After: >>    text data bss dec hex filename >>   39235 17596 128 56959 de7f ./drivers/gpu/drm/bridge/tc358767.o > > Why is text smaller and data larger with this change? There are less instructions being used with the change since it's not shoving the array data onto the stack at run time. Instead the array is being stored in the data section and there is less object code required to access the data. Colin > >> >> (gcc version 10.3.0) >> >> Signed-off-by: Colin Ian King >> --- >>  drivers/gpu/drm/bridge/tc358767.c | 2 +- >>  1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c >> index 23a6f90b694b..599c23759400 100644 >> --- a/drivers/gpu/drm/bridge/tc358767.c >> +++ b/drivers/gpu/drm/bridge/tc358767.c >> @@ -468,7 +468,7 @@ static int tc_pxl_pll_en(struct tc_data *tc, u32 refclk, u32 pixelclock) >>   int div, best_div = 1; >>   int mul, best_mul = 1; >>   int delta, best_delta; >> - int ext_div[] = {1, 2, 3, 5, 7}; >> + static const int ext_div[] = {1, 2, 3, 5, 7}; >>   int best_pixelclock = 0; >>   int vco_hi = 0; >>   u32 pxl_pllparam; > >