From patchwork Fri Feb 11 08:48:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christophe Leroy X-Patchwork-Id: 1591524 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4Jw6jH4kwdz9s0r for ; Fri, 11 Feb 2022 19:48:50 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4Jw6jD4fFPz3cPk for ; Fri, 11 Feb 2022 19:48:48 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.235.10; helo=pegase2.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) (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 lists.ozlabs.org (Postfix) with ESMTPS id 4Jw6j35m1rz3bTP for ; Fri, 11 Feb 2022 19:48:36 +1100 (AEDT) Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4Jw6hx4vY8z9sSM; Fri, 11 Feb 2022 09:48:33 +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 klDIzGqmxZ6I; Fri, 11 Feb 2022 09:48:33 +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 4Jw6hx4Bhzz9sSL; Fri, 11 Feb 2022 09:48:33 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7ED5A8B77D; Fri, 11 Feb 2022 09:48:33 +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 rtRKHQ_BcwTx; Fri, 11 Feb 2022 09:48:33 +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 36EBB8B764; Fri, 11 Feb 2022 09:48:33 +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 21B8mNGc936763 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 11 Feb 2022 09:48:23 +0100 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 21B8mMRd936762; Fri, 11 Feb 2022 09:48:22 +0100 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: "David S. Miller" , Jakub Kicinski Subject: [PATCH] net: Remove branch in csum_shift() Date: Fri, 11 Feb 2022 09:48:16 +0100 Message-Id: X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1644569294; l=1792; s=20211009; h=from:subject:message-id; bh=bn4qVlTEECkFmk/D3ReBpu/1ueTQNT/DDGPwdR54bMw=; b=YfWOLv3f7QPdV7JOLEvppeShwBCfk+aGgbZur22GW+m9WX6XeuSeUHvizGFhnuzg3csBcc4Zfcbu MOrUk6ZGDv8PKhpkllz2TJosNNk2sqMNIrrXLeIPI0EXjv6RY/gs X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Today's implementation of csum_shift() leads to branching based on parity of 'offset' 000002f8 : 2f8: 70 a5 00 01 andi. r5,r5,1 2fc: 41 a2 00 08 beq 304 300: 54 84 c0 3e rotlwi r4,r4,24 304: 7c 63 20 14 addc r3,r3,r4 308: 7c 63 01 94 addze r3,r3 30c: 4e 80 00 20 blr Use first bit of 'offset' directly as input of the rotation instead of branching. 000002f8 : 2f8: 54 a5 1f 38 rlwinm r5,r5,3,28,28 2fc: 20 a5 00 20 subfic r5,r5,32 300: 5c 84 28 3e rotlw r4,r4,r5 304: 7c 63 20 14 addc r3,r3,r4 308: 7c 63 01 94 addze r3,r3 30c: 4e 80 00 20 blr And change to left shift instead of right shift to skip one more instruction. This has no impact on the final sum. 000002f8 : 2f8: 54 a5 1f 38 rlwinm r5,r5,3,28,28 2fc: 5c 84 28 3e rotlw r4,r4,r5 300: 7c 63 20 14 addc r3,r3,r4 304: 7c 63 01 94 addze r3,r3 308: 4e 80 00 20 blr Signed-off-by: Christophe Leroy --- include/net/checksum.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/include/net/checksum.h b/include/net/checksum.h index 5218041e5c8f..9badcd5532ef 100644 --- a/include/net/checksum.h +++ b/include/net/checksum.h @@ -83,9 +83,7 @@ static inline __sum16 csum16_sub(__sum16 csum, __be16 addend) static inline __wsum csum_shift(__wsum sum, int offset) { /* rotate sum to align it with a 16b boundary */ - if (offset & 1) - return (__force __wsum)ror32((__force u32)sum, 8); - return sum; + return (__force __wsum)rol32((__force u32)sum, (offset & 1) << 3); } static inline __wsum