From patchwork Thu May 20 09:23:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 445348 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 F2709C433ED for ; Thu, 20 May 2021 11:05:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA4716135B for ; Thu, 20 May 2021 11:05:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240105AbhETLG7 (ORCPT ); Thu, 20 May 2021 07:06:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:37054 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240075AbhETLE6 (ORCPT ); Thu, 20 May 2021 07:04:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9E68861D1F; Thu, 20 May 2021 10:05:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621505104; bh=7oYuLHNwzc9jy8+tx7Q4sSHTjfKDMdJFbkcaYmc36R8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=exwl6lFiQ2/5PYp/VU+Y1bMov5cHC2ONY1ULwlOumSPgSVsCJHmfz7QBrZLJclXTq G6bud5qjooTbLoBmb/8w+34B6EQBdJeRzkdHZF/yf5WP5Um3aotDphkipct7zVX0HB 9UOMv/p7EOo/DYF7+Gu3K4OcwMDnVqdE7uvHkWiA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Maciej W. Rozycki" , Thomas Bogendoerfer Subject: [PATCH 4.9 217/240] MIPS: Avoid DIVU in `__div64_32 is result would be zero Date: Thu, 20 May 2021 11:23:29 +0200 Message-Id: <20210520092115.976737043@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092108.587553970@linuxfoundation.org> References: <20210520092108.587553970@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Maciej W. Rozycki commit c1d337d45ec0a802299688e17d568c4e3a585895 upstream. We already check the high part of the divident against zero to avoid the costly DIVU instruction in that case, needed to reduce the high part of the divident, so we may well check against the divisor instead and set the high part of the quotient to zero right away. We need to treat the high part the divident in that case though as the remainder that would be calculated by the DIVU instruction we avoided. This has passed correctness verification with test_div64 and reduced the module's average execution time down to 1.0445s and 0.2619s from 1.0668s and 0.2629s respectively for an R3400 CPU @40MHz and a 5Kc CPU @160MHz. Signed-off-by: Maciej W. Rozycki Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman --- arch/mips/include/asm/div64.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/mips/include/asm/div64.h +++ b/arch/mips/include/asm/div64.h @@ -68,9 +68,11 @@ \ __high = __div >> 32; \ __low = __div; \ - __upper = __high; \ \ - if (__high) { \ + if (__high < __radix) { \ + __upper = __high; \ + __high = 0; \ + } else { \ __asm__("divu $0, %z1, %z2" \ : "=x" (__modquot) \ : "Jr" (__high), "Jr" (__radix)); \