From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id A2EBE3858C56 for ; Thu, 21 Dec 2023 19:05:44 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org A2EBE3858C56 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com ARC-Filter: OpenARC Filter v1.0.0 sourceware.org A2EBE3858C56 Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1703185547; cv=none; b=OfJaLb1HNkz7mvAtGSLqZUv5x0v4L2HV3JH8yvDd165u6FxvFx1R0ORKS1PzkLlu2WX5IPu8FVkf2DqNspGZBTbMexKk+vn+IZmoQzxYEeXicv9DjVMDTMvG4OIzvjIbOcDVw9RHIJf7ddtRnShDyHuG48wAIHfn0I8aS94n0fc= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1703185547; c=relaxed/simple; bh=V458qOnfl26txyaVZg+V0k45wSZRbwZ5A9AeF8jfKnY=; h=DKIM-Signature:MIME-Version:From:Date:Message-ID:Subject:To; b=x5QwmiJBhHH0Ur0FjX+DCYvWdr1jSGydrWH/aveauFfWJ8TPxz65OQdVEh9R+9sGcEqhR8ZGpPutc/HcRWxXqx8Mzc8H0F9bjzKpdwIvOmKkDHJ2hJTryQGaSZlvKVtq6ah/uS98+yK/Wcx4oUhFnHoKlRISzvNrviWpm+6/c+k= ARC-Authentication-Results: i=1; server2.sourceware.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703185544; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jZzQPPGaxHQ1h6vcahPqDQNDSysgDijMbytd102+34g=; b=Z9DcnJ3vpPvyl5ORVaFVpTniqS/8DJiXNXRL2GhLKW6osSWj/BE/GTvtLrhgpYQNzMgISM vnGllWcCdMtWLyU1bpJ0Vg77W7CG0gboyR7Hi0xYH81rDTpaBrMf2ZZjjzgYVFWTCTYULI moHhNtbesoBx88i17Qgv9NLuleukkQQ= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-495-mAvehWATNp2qtEGueH0CPg-1; Thu, 21 Dec 2023 14:05:42 -0500 X-MC-Unique: mAvehWATNp2qtEGueH0CPg-1 Received: by mail-ej1-f70.google.com with SMTP id a640c23a62f3a-a236b11a28dso12724966b.1 for ; Thu, 21 Dec 2023 11:05:42 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1703185541; x=1703790341; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=jZzQPPGaxHQ1h6vcahPqDQNDSysgDijMbytd102+34g=; b=lAkmN8EPOh2eB3pm8qVqGdmiXg7ev5U4yv2y/QMrbatlUB7o55p0S/qdp0pM/+VrDB OZPZKR5bmfPQ6Ndw8HE9+j9VkbZh84bzSSVkppr8l61Q4FJ5ex+ENsXCB2Pv/nppbwRM +ngpANp0e1qbuNHFpzYPbdR0CinzWz6ffSCtUR0Wn2WBc7xcRkLdSKtwD6JNy6YODh4s A9fjwIXhDGkIGD00gP3helKeaw38eaXPvvqWDGoFtct5HjQr+81PuYqII5tpiHTnDsKw vHuyf5SIq3oNJk6Zc+bEelatVEaO8VpD9i311PTm8OSjDV2KC3ou5eQ3kUtizF82ezPE +REg== X-Gm-Message-State: AOJu0Yx7gPNUrUVytYg+ZLAOUuKGMIWAw+B4RIdIBzaGT4ifGr4szaHt SsUK87dWXFgivs36Isvf+inJ08yNrwEMZyfdyzb3j9758Q4ztPAm/2NDtehdxG9qeCah3TSkIqe Jb4PgJwQAaz95O8u65PM2OTK7zrplBHqgONeIoBE= X-Received: by 2002:a17:906:abda:b0:a23:9a1d:334d with SMTP id kq26-20020a170906abda00b00a239a1d334dmr311650ejb.7.1703185541387; Thu, 21 Dec 2023 11:05:41 -0800 (PST) X-Google-Smtp-Source: AGHT+IGziB8urcAC7+FVEK4QkhcyRw96kZU8uMtFikW68QDmmzzoBVAXxeVT1J09z0oBzn1IC8IvQ1Bhu1fXP0HNNgQ= X-Received: by 2002:a17:906:abda:b0:a23:9a1d:334d with SMTP id kq26-20020a170906abda00b00a239a1d334dmr311637ejb.7.1703185541108; Thu, 21 Dec 2023 11:05:41 -0800 (PST) MIME-Version: 1.0 References: <20231220061054.35685-1-zengxiao@eswincomputing.com> <202312210916074865474@eswincomputing.com> In-Reply-To: <202312210916074865474@eswincomputing.com> From: Jeff Johnston Date: Thu, 21 Dec 2023 14:05:29 -0500 Message-ID: Subject: Re: Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization To: Xiao Zeng Cc: "newlib@sourceware.org" , "palmer@rivosinc.com" , jeffreyalaw , Torbjorn SVENSSON X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/alternative; boundary="0000000000002a2378060d09c937" X-Spam-Status: No, score=-10.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,HTML_MESSAGE,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: --0000000000002a2378060d09c937 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Patch merged. Thanks. -- Jeff J. On Wed, Dec 20, 2023 at 8:16=E2=80=AFPM Xiao Zeng wrote: > 2023-12-21 06:48 Jeff Johnston wrote: > > > > >Unless I am missing something, I think the code could be made even simpl= er > >to return the pointer when found and return NULL otherwise. > Yes, you have found a more efficient method. > After my testing, fewer assembly instructions were generated. This is > really exciting. > > Xiao's patch: > --------------------------------------------------------- > libc_a-strpbrk.o: file format elf64-littleriscv > > > Disassembly of section .text: > > 0000000000000000 : > 0: 00054683 lbu a3,0(a0) > > 0000000000000004 <.LVL1>: > 4: 04068063 beqz a3,44 <.L10> > 8: 0005c603 lbu a2,0(a1) > c: 04060063 beqz a2,4c <.L14> > > 0000000000000010 <.L5>: > 10: 00058793 mv a5,a1 > 14: 00060713 mv a4,a2 > 18: 00c0006f j 24 <.L4> > > 000000000000001c <.L17>: > 1c: 0007c703 lbu a4,0(a5) > 20: 00070863 beqz a4,30 <.L16> > > 0000000000000024 <.L4>: > 24: 00178793 addi a5,a5,1 > > 0000000000000028 <.LVL5>: > 28: fee69ae3 bne a3,a4,1c <.L17> > > 000000000000002c <.L1>: > 2c: 00008067 ret > > 0000000000000030 <.L16>: > 30: 00154683 lbu a3,1(a0) > 34: 00150513 addi a0,a0,1 > > 0000000000000038 <.LVL8>: > 38: fc069ce3 bnez a3,10 <.L5> > > 000000000000003c <.L6>: > 3c: 0007c783 lbu a5,0(a5) > > 0000000000000040 <.LVL9>: > 40: fe0796e3 bnez a5,2c <.L1> > > 0000000000000044 <.L10>: > 44: 00000513 li a0,0 > > 0000000000000048 <.LVL11>: > 48: 00008067 ret > > 000000000000004c <.L14>: > 4c: 00154683 lbu a3,1(a0) > 50: 00150513 addi a0,a0,1 > 54: fe069ce3 bnez a3,4c <.L14> > 58: 00058793 mv a5,a1 > 5c: fe1ff06f j 3c <.L6> > --------------------------------------------------------- > > Jeff's patch > --------------------------------------------------------- > libc_a-strpbrk.o: file format elf64-littleriscv > > > Disassembly of section .text: > > 0000000000000000 : > 0: 00054683 lbu a3,0(a0) > 4: 02068c63 beqz a3,3c <.L8> > 8: 0005c603 lbu a2,0(a1) > c: 02060c63 beqz a2,44 <.L12> > > 0000000000000010 <.L5>: > 10: 00058793 mv a5,a1 > 14: 00060713 mv a4,a2 > 18: 00c0006f j 24 <.L4> > > 000000000000001c <.L15>: > 1c: 0007c703 lbu a4,0(a5) > 20: 00070863 beqz a4,30 <.L14> > > 0000000000000024 <.L4>: > 24: 00178793 addi a5,a5,1 > > 0000000000000028 <.LVL4>: > 28: fed71ae3 bne a4,a3,1c <.L15> > 2c: 00008067 ret > > 0000000000000030 <.L14>: > 30: 00154683 lbu a3,1(a0) > 34: 00150513 addi a0,a0,1 > > 0000000000000038 <.LVL6>: > 38: fc069ce3 bnez a3,10 <.L5> > > 000000000000003c <.L8>: > 3c: 00000513 li a0,0 > > 0000000000000040 <.LVL7>: > 40: 00008067 ret > > 0000000000000044 <.L12>: > 44: 00154683 lbu a3,1(a0) > 48: 00150513 addi a0,a0,1 > 4c: fe069ce3 bnez a3,44 <.L12> > 50: fedff06f j 3c <.L8> > --------------------------------------------------------- > After careful comparison, it was found that there are fewer assembly > instructions after the Jeff's patch. > > > > >index 774db1e..d984745 100644 > >--- a/newlib/libc/string/strpbrk.c > >+++ b/newlib/libc/string/strpbrk.c > >@@ -29,23 +29,16 @@ strpbrk (const char *s1, > > const char *s2) > > { > > const char *c =3D s2; > >- if (!*s1) > >- return (char *) NULL; > > > > while (*s1) > > { > > for (c =3D s2; *c; c++) > > { > > if (*s1 =3D=3D *c) > >- break; > >+ return (char *) s1; > > } > >- if (*c) > >- break; > > s1++; > > } > > > >- if (*c =3D=3D '\0') > >- s1 =3D NULL; > >- > >- return (char *) s1; > >+ return (char *) NULL; > > } > > > >On Wed, Dec 20, 2023 at 1:12=E2=80=AFAM Xiao Zeng > >wrote: > > > >> Signed-off-by: Xiao Zeng > >> --- > >> newlib/libc/string/strpbrk.c | 5 ++--- > >> 1 file changed, 2 insertions(+), 3 deletions(-) > >> > >> diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk= .c > >> index 774db1e6d..95e89c20c 100644 > >> --- a/newlib/libc/string/strpbrk.c > >> +++ b/newlib/libc/string/strpbrk.c > >> @@ -37,15 +37,14 @@ strpbrk (const char *s1, > >> for (c =3D s2; *c; c++) > >> { > >> if (*s1 =3D=3D *c) > >> - break; > >> + goto end; > >> } > >> - if (*c) > >> - break; > >> s1++; > >> } > >> > >> if (*c =3D=3D '\0') > >> s1 =3D NULL; > >> > >> +end: > >> return (char *) s1; > >> } > >> -- > >> 2.17.1 > >> > >> > > Thanks > Xiao Zeng > > --0000000000002a2378060d09c937--