From patchwork Fri Feb 11 10:24:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 12743134 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 167B5C433F5 for ; Fri, 11 Feb 2022 10:25:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241413AbiBKKZH (ORCPT ); Fri, 11 Feb 2022 05:25:07 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:52032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232557AbiBKKZG (ORCPT ); Fri, 11 Feb 2022 05:25:06 -0500 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B198BE5A; Fri, 11 Feb 2022 02:25:05 -0800 (PST) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4Jw8rJ0vXkz9sSQ; Fri, 11 Feb 2022 11:25:04 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xBMWOrU8Izvi; Fri, 11 Feb 2022 11:25:04 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4Jw8rJ07xLz9sSL; Fri, 11 Feb 2022 11:25:04 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id E78998B780; Fri, 11 Feb 2022 11:25:03 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 1ZAD8N-JTl7t; Fri, 11 Feb 2022 11:25:03 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.6.91]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A3A568B77D; Fri, 11 Feb 2022 11:25:03 +0100 (CET) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 21BAOtqD946512 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 11 Feb 2022 11:24:55 +0100 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 21BAOtsG946511; Fri, 11 Feb 2022 11:24:55 +0100 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "David S. Miller" , Jakub Kicinski Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org Subject: [PATCH 2/2] powerpc/32: Implement csum_sub Date: Fri, 11 Feb 2022 11:24:49 +0100 Message-Id: X-Mailer: git-send-email 2.34.1 In-Reply-To: <0c8eaab8f0685d2a70d125cf876238c70afd4fb6.1644574987.git.christophe.leroy@csgroup.eu> References: <0c8eaab8f0685d2a70d125cf876238c70afd4fb6.1644574987.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1644575088; l=1588; s=20211009; h=from:subject:message-id; bh=pXcr+Jwxdt7vu5J4mP6ZswUtbWBzwIEJ1PdZV31QSE0=; b=HSZVvXJkPmCF8TxbXSiWKLDoI7psAxRjgWG87bMYX2pCsi30PB7LXU1q5qLFV51bzViRqYFS/GZw ZhVN0EtRBTO0QIYTyu3aBjMk6XMUkzaYl4DbtnndhKhdeIBqjSD8 X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When building kernel with CONFIG_CC_OPTIMISE_FOR_SIZE, several copies of csum_sub() are generated, with the following code: 00000170 : 170: 7c 84 20 f8 not r4,r4 174: 7c 63 20 14 addc r3,r3,r4 178: 7c 63 01 94 addze r3,r3 17c: 4e 80 00 20 blr Let's define a PPC32 version with subc/addme, and for it's inlining. It will return 0 instead of 0xffffffff when subtracting 0x80000000 to itself, this is not an issue as 0 and ~0 are equivalent, refer to RFC 1624. Signed-off-by: Christophe Leroy --- arch/powerpc/include/asm/checksum.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/powerpc/include/asm/checksum.h b/arch/powerpc/include/asm/checksum.h index 350de8f90250..3288a1bf5e8d 100644 --- a/arch/powerpc/include/asm/checksum.h +++ b/arch/powerpc/include/asm/checksum.h @@ -112,6 +112,22 @@ static __always_inline __wsum csum_add(__wsum csum, __wsum addend) #endif } +#ifdef CONFIG_PPC32 +#define HAVE_ARCH_CSUM_SUB +static __always_inline __wsum csum_sub(__wsum csum, __wsum addend) +{ + if (__builtin_constant_p(csum) && (csum == 0 || csum == ~0)) + return ~addend; + if (__builtin_constant_p(addend) && (addend == 0 || addend == ~0)) + return csum; + + asm("subc %0,%0,%1;" + "addme %0,%0;" + : "+r" (csum) : "r" (addend) : "xer"); + return csum; +} +#endif + /* * This is a version of ip_compute_csum() optimized for IP headers, * which always checksum on 4 octet boundaries. ihl is the number