From nobody Fri Dec 19 04:02:16 2025 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 A2F66C83F1D for ; Wed, 30 Aug 2023 19:14:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241968AbjH3TK7 (ORCPT ); Wed, 30 Aug 2023 15:10:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244770AbjH3N5t (ORCPT ); Wed, 30 Aug 2023 09:57:49 -0400 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB892C2 for ; Wed, 30 Aug 2023 06:57:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1693403866; bh=nVJMnv3VCXXs9TgaAACyjEPEMdvWPuaWCwde2DJ1HJ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=V9BTof8lCIK92dwQ2+z8QNcmYNiZGc9JvEryL2GwrA9Mnrg38AHNtUSdKoZDVI27O IFpMfYG4ijMEFBdHYCaf7KeBQRvYSlDGsMXk47lZMGfY7jM9hEzQoI1yjUOiX3gfw0 xaWHDW3wWAekUKcKOg2x0NT55pIsNL9ATbDnQGpXu2Yz3hts1BgyQ9aGCm/U+Ng6JK yiYnatLh6DdcgbHr+ulXbY4JNgcmqQzqtRsHTAhqXWNHh+VZ06t53adm30upnsqlr4 XI1SKifiy5fzhD+lxK6zc2r1CrI3o5Ko0GXkbMD0pXP+1LKpJpNdFeZ6UmE99m0k5q bsJJNgymS9X2w== Received: from localhost.localdomain (unknown [182.253.126.208]) by gnuweeb.org (Postfix) with ESMTPSA id 2C4A124B327; Wed, 30 Aug 2023 20:57:42 +0700 (WIB) From: Ammar Faizi To: Willy Tarreau , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Cc: Ammar Faizi , Nicholas Rosenberg , Alviro Iskandar Setiawan , Michael William Jonathan , GNU/Weeb Mailing List , Linux Kernel Mailing List Subject: [RFC PATCH v1 2/5] tools/nolibc: x86-64: Use `rep stosb` for `memset()` Date: Wed, 30 Aug 2023 20:57:23 +0700 Message-Id: <20230830135726.1939997-3-ammarfaizi2@gnuweeb.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230830135726.1939997-1-ammarfaizi2@gnuweeb.org> References: <20230830135726.1939997-1-ammarfaizi2@gnuweeb.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Simplify memset() on the x86-64 arch. The x86-64 arch has a 'rep stosb' instruction, which can perform memset() using only a single instruction, given: %al =3D value (just like the second argument of memset()) %rdi =3D destination %rcx =3D length Before this patch: ``` 00000000000010c9 : 10c9: 48 89 f8 mov %rdi,%rax 10cc: 48 85 d2 test %rdx,%rdx 10cf: 74 0e je 10df 10d1: 31 c9 xor %ecx,%ecx 10d3: 40 88 34 08 mov %sil,(%rax,%rcx,1) 10d7: 48 ff c1 inc %rcx 10da: 48 39 ca cmp %rcx,%rdx 10dd: 75 f4 jne 10d3 10df: c3 ret ``` After this patch: ``` 00000000000010b1 : 10b1: 48 89 f0 mov %rsi,%rax 10b4: 48 89 d1 mov %rdx,%rcx 10b7: 48 89 fa mov %rdi,%rdx 10ba: f3 aa rep stos %al,%es:(%rdi) 10bc: 48 89 d0 mov %rdx,%rax 10bf: c3 ret ``` Signed-off-by: Ammar Faizi --- tools/include/nolibc/arch-x86_64.h | 13 +++++++++++++ tools/include/nolibc/string.h | 2 ++ 2 files changed, 15 insertions(+) diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch= -x86_64.h index c5162170a2ccdff1..42f2674ad1ecdd64 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -179,6 +179,9 @@ void *memmove(void *dst, const void *src, size_t len); #define NOLIBC_ARCH_HAS_MEMCPY void *memcpy(void *dst, const void *src, size_t len); =20 +#define NOLIBC_ARCH_HAS_MEMSET +void *memset(void *dst, int c, size_t len); + __asm__ ( ".section .text.nolibc_memmove\n" ".weak memmove\n" @@ -199,6 +202,16 @@ __asm__ ( "movq %rdx, %rcx\n" "rep movsb\n" "retq\n" + +".section .text.nolibc_memset\n" +".weak memset\n" +"memset:\n" + "movq %rsi, %rax\n" + "movq %rdx, %rcx\n" + "movq %rdi, %rdx\n" + "rep stosb\n" + "movq %rdx, %rax\n" + "retq\n" ); =20 #endif /* _NOLIBC_ARCH_X86_64_H */ diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h index 6eca267ec6fa7177..1bad6121ef8c4ab5 100644 --- a/tools/include/nolibc/string.h +++ b/tools/include/nolibc/string.h @@ -84,6 +84,7 @@ void *memcpy(void *dst, const void *src, size_t len) } #endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */ =20 +#ifndef NOLIBC_ARCH_HAS_MEMSET /* might be ignored by the compiler without -ffreestanding, then found as * missing. */ @@ -99,6 +100,7 @@ void *memset(void *dst, int b, size_t len) } return dst; } +#endif /* #ifndef NOLIBC_ARCH_HAS_MEMSET */ =20 static __attribute__((unused)) char *strchr(const char *s, int c) --=20 Ammar Faizi