From nobody Fri Dec 19 04:02:18 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 76385C83F1C for ; Wed, 30 Aug 2023 18:53:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245270AbjH3SwH (ORCPT ); Wed, 30 Aug 2023 14:52:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244769AbjH3N5p (ORCPT ); Wed, 30 Aug 2023 09:57:45 -0400 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF400C2 for ; Wed, 30 Aug 2023 06:57:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1693403862; bh=BxyzFCZWmrBfXUbxKI5hpgIUfXerIGQlN4Xd8JmlKXY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WNYAvS3/NWcw6XUmXtRSU3QIarGWY0PURwgpv+hGiaYnJr1hkqSTwbbXoTOWnkj7h bo707kQwh1NlGqN7PNU8WKliDb+EAZxMZgbqB3jt6GU3BGUEdgRXn86vwyhoJXz8T1 la4LCpSlcUgv/uJWriTLTRXvQoBwVEa8FIDs+JhjXxb4YD38dbBTZ/dJfYf7lsPJuX Yn5sffu6chAOkZyQfgw6/oJIqefiRrCTBVkhctiOYMTQXHaD0B5H7vojKcwH/ziAVS hIqj1x7sFJgltOO8ZMxezwQNMyB63iracCKFcQgn5Kipz0hh+bpW8ywo9dP4IgVVFo I1D0dVDJH9vpg== Received: from localhost.localdomain (unknown [182.253.126.208]) by gnuweeb.org (Postfix) with ESMTPSA id 1D13624B2B0; Wed, 30 Aug 2023 20:57:38 +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 1/5] tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()` Date: Wed, 30 Aug 2023 20:57:22 +0700 Message-Id: <20230830135726.1939997-2-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 memcpy() and memmove() on the x86-64 arch. The x86-64 arch has a 'rep movsb' instruction, which can perform memcpy() using only a single instruction, given: %rdi =3D destination %rsi =3D source %rcx =3D length Additionally, it can also handle the overlapping case by setting DF=3D1 (backward copy), which can be used as the memmove() implementation. Before this patch: ``` 00000000000010ab : 10ab: 48 89 f8 mov %rdi,%rax 10ae: 31 c9 xor %ecx,%ecx 10b0: 48 39 f7 cmp %rsi,%rdi 10b3: 48 83 d1 ff adc $0xffffffffffffffff,%rcx 10b7: 48 85 d2 test %rdx,%rdx 10ba: 74 25 je 10e1 10bc: 48 83 c9 01 or $0x1,%rcx 10c0: 48 39 f0 cmp %rsi,%rax 10c3: 48 c7 c7 ff ff ff ff mov $0xffffffffffffffff,%rdi 10ca: 48 0f 43 fa cmovae %rdx,%rdi 10ce: 48 01 cf add %rcx,%rdi 10d1: 44 8a 04 3e mov (%rsi,%rdi,1),%r8b 10d5: 44 88 04 38 mov %r8b,(%rax,%rdi,1) 10d9: 48 01 cf add %rcx,%rdi 10dc: 48 ff ca dec %rdx 10df: 75 f0 jne 10d1 10e1: c3 ret 00000000000010e2 : 10e2: 48 89 f8 mov %rdi,%rax 10e5: 48 85 d2 test %rdx,%rdx 10e8: 74 12 je 10fc 10ea: 31 c9 xor %ecx,%ecx 10ec: 40 8a 3c 0e mov (%rsi,%rcx,1),%dil 10f0: 40 88 3c 08 mov %dil,(%rax,%rcx,1) 10f4: 48 ff c1 inc %rcx 10f7: 48 39 ca cmp %rcx,%rdx 10fa: 75 f0 jne 10ec 10fc: c3 ret ``` After this patch: ``` 0000000000001093 : 1093: 48 89 f8 mov %rdi,%rax 1096: 48 89 d1 mov %rdx,%rcx 1099: 48 8d 7c 0f ff lea -0x1(%rdi,%rcx,1),%rdi 109e: 48 8d 74 0e ff lea -0x1(%rsi,%rcx,1),%rsi 10a3: fd std 10a4: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) 10a6: fc cld 10a7: c3 ret 00000000000010a8 : 10a8: 48 89 f8 mov %rdi,%rax 10ab: 48 89 d1 mov %rdx,%rcx 10ae: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) 10b0: c3 ret ``` Signed-off-by: Ammar Faizi --- tools/include/nolibc/arch-x86_64.h | 28 ++++++++++++++++++++++++++++ tools/include/nolibc/string.h | 4 ++++ 2 files changed, 32 insertions(+) diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch= -x86_64.h index e5ccb926c90306b6..c5162170a2ccdff1 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -173,4 +173,32 @@ void __attribute__((weak, noreturn, optimize("Os", "om= it-frame-pointer"))) __no_ __builtin_unreachable(); } =20 +#define NOLIBC_ARCH_HAS_MEMMOVE +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); + +__asm__ ( +".section .text.nolibc_memmove\n" +".weak memmove\n" +"memmove:\n" + "movq %rdi, %rax\n" + "movq %rdx, %rcx\n" + "leaq -1(%rdi, %rcx), %rdi\n" + "leaq -1(%rsi, %rcx), %rsi\n" + "std\n" + "rep movsb\n" + "cld\n" + "retq\n" + +".section .text.nolibc_memcpy\n" +".weak memcpy\n" +"memcpy:\n" + "movq %rdi, %rax\n" + "movq %rdx, %rcx\n" + "rep movsb\n" + "retq\n" +); + #endif /* _NOLIBC_ARCH_X86_64_H */ diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h index 0c2e06c7c4772bc6..6eca267ec6fa7177 100644 --- a/tools/include/nolibc/string.h +++ b/tools/include/nolibc/string.h @@ -49,6 +49,7 @@ void *_nolibc_memcpy_down(void *dst, const void *src, siz= e_t len) return dst; } =20 +#ifndef NOLIBC_ARCH_HAS_MEMMOVE /* might be ignored by the compiler without -ffreestanding, then found as * missing. */ @@ -72,13 +73,16 @@ void *memmove(void *dst, const void *src, size_t len) } return dst; } +#endif /* #ifndef NOLIBC_ARCH_HAS_MEMMOVE */ =20 +#ifndef NOLIBC_ARCH_HAS_MEMCPY /* must be exported, as it's used by libgcc on ARM */ __attribute__((weak,unused,section(".text.nolibc_memcpy"))) void *memcpy(void *dst, const void *src, size_t len) { return _nolibc_memcpy_up(dst, src, len); } +#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */ =20 /* might be ignored by the compiler without -ffreestanding, then found as * missing. --=20 Ammar Faizi