From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752946AbeEGVjm (ORCPT ); Mon, 7 May 2018 17:39:42 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:38789 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752524AbeEGVjl (ORCPT ); Mon, 7 May 2018 17:39:41 -0400 X-Google-Smtp-Source: AB8JxZrtp/OFEJ6P1OYDnVr0VvNMtW5vB7bB8QRYGS3wkUpN5KhofQF1qGaLHrkOO8+038YqXDzUag== Date: Tue, 8 May 2018 00:39:37 +0300 From: Alexey Dobriyan To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Cc: linux-kernel@vger.kernel.org, x86@kernel.org Subject: [PATCH] x86_64: use immediate constants in __clear_user() Message-ID: <20180507213937.GB32406@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Save 2 registers. Adding constants should be just as fast as adding registers. Signed-off-by: Alexey Dobriyan --- arch/x86/lib/usercopy_64.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -23,13 +23,13 @@ unsigned long __clear_user(void __user *addr, unsigned long size) asm volatile( " testq %[size8],%[size8]\n" " jz 4f\n" - "0: movq %[zero],(%[dst])\n" - " addq %[eight],%[dst]\n" + "0: movq $0,(%[dst])\n" + " addq $8,%[dst]\n" " decl %%ecx ; jnz 0b\n" "4: movq %[size1],%%rcx\n" " testl %%ecx,%%ecx\n" " jz 2f\n" - "1: movb %b[zero],(%[dst])\n" + "1: movb $0,(%[dst])\n" " incq %[dst]\n" " decl %%ecx ; jnz 1b\n" "2:\n" @@ -40,8 +40,7 @@ unsigned long __clear_user(void __user *addr, unsigned long size) _ASM_EXTABLE(0b,3b) _ASM_EXTABLE(1b,2b) : [size8] "=&c"(size), [dst] "=&D" (__d0) - : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr), - [zero] "r" (0UL), [eight] "r" (8UL)); + : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr)); clac(); return size; }