From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28144 invoked by alias); 27 Feb 2013 03:17:32 -0000 Received: (qmail 28039 invoked by uid 22791); 27 Feb 2013 03:17:28 -0000 X-SWARE-Spam-Status: No, hits=-5.1 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,KHOP_RCVD_TRUST,KHOP_SPAMHAUS_DROP,KHOP_THREADED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE,TW_CL,TW_DR,TW_MV,TW_OV,TW_XF X-Spam-Check-By: sourceware.org Received: from mail-pa0-f51.google.com (HELO mail-pa0-f51.google.com) (209.85.220.51) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 27 Feb 2013 03:17:07 +0000 Received: by mail-pa0-f51.google.com with SMTP id hz1so135605pad.10 for ; Tue, 26 Feb 2013 19:17:07 -0800 (PST) X-Received: by 10.66.240.136 with SMTP id wa8mr5050202pac.143.1361935027082; Tue, 26 Feb 2013 19:17:07 -0800 (PST) Received: from pebble.twiddle.net (50-194-63-110-static.hfc.comcastbusiness.net. [50.194.63.110]) by mx.google.com with ESMTPS id pp1sm265271pac.7.2013.02.26.19.17.05 (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Tue, 26 Feb 2013 19:17:06 -0800 (PST) From: Richard Henderson To: libc-ports@sourceware.org Cc: Joseph Myers Subject: [PATCH 20/26] arm: Implement armv6t2 optimized strlen Date: Wed, 27 Feb 2013 03:17:00 -0000 Message-Id: <1361934986-17018-21-git-send-email-rth@twiddle.net> In-Reply-To: <1361934986-17018-1-git-send-email-rth@twiddle.net> References: <1361934986-17018-1-git-send-email-rth@twiddle.net> X-IsSubscribed: yes Mailing-List: contact libc-ports-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: libc-ports-owner@sourceware.org X-SW-Source: 2013-02/txt/msg00083.txt.bz2 Twice as fast for long strings and 50% faster for short strings over the armv4 version on A15. --- * sysdeps/arm/armv6t2/strlen.S: New file. --- ports/sysdeps/arm/armv6t2/strlen.S | 93 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 ports/sysdeps/arm/armv6t2/strlen.S diff --git a/ports/sysdeps/arm/armv6t2/strlen.S b/ports/sysdeps/arm/armv6t2/strlen.S new file mode 100644 index 0000000..d7d6e1f --- /dev/null +++ b/ports/sysdeps/arm/armv6t2/strlen.S @@ -0,0 +1,93 @@ +/* Copyright (C) 2013 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library. If not, see + . */ + +#include + + .syntax unified + .text + +ENTRY(strlen) + @ r0 = start of string + pld [r0] + + @ To cater to long strings, we want to search through a few + @ characters until we reach an aligned pointer. To cater to + @ small strings, we don't want to start doing word operations + @ immediately. The compromise is a maximum of 16 bytes less + @ whatever is required to end with an aligned pointer. + @ r3 = number of characters to search in alignment loop + and r3, r0, #7 + s(mov) r1, r0 @ Save the input pointer + rsb r3, r3, #16 + + @ Loop until we find ... +1: ldrb r2, [r0], #1 + subs r3, r3, #1 @ ... the aligment point + it ne + cmpne r2, #0 @ ... or EOS + bne 1b + + @ Disambiguate the exit possibilites above + cmp r2, #0 @ Found EOS + ittt eq + subeq r0, r0, #1 @ Undo post-inc above + subeq r0, r0, r1 @ Subtract input to compute length + bxeq lr + + @ So now we're aligned. + ldrd r2, r3, [r0], #8 + movw ip, #0xfefe + pld [r0, #64] + movt ip, #0xfefe + pld [r0, #128] + pld [r0, #192] + + @ Loop searching for EOS or C, 8 bytes at a time. + @ Adding (unsigned saturating) 0xfe means result of 0xfe for any byte + @ that was originally zero and 0xff otherwise. Therefore we consider + @ the lsb of each byte the "found" bit, with 0 for a match. + .balign 16 +2: uqadd8 r2, r2, ip @ Find EOS + uqadd8 r3, r3, ip + pld [r0, #256] @ Prefetch 4 lines ahead + s(and) r3, r3, r2 @ Combine the two words + mvns r3, r3 @ Test for any found bit true + it eq + ldrdeq r2, r3, [r0], #8 + beq 2b + + @ Found something. Disambiguate between first and second words. + @ Adjust r0 to point to the word containing the match. + @ Adjust r2 to the found bits for the word containing the match. + mvns r2, r2 + itee ne + subne r0, r0, #8 + moveq r2, r3 + subeq r0, r0, #4 + + @ Find the bit-offset of the match within the word. +#ifdef __ARMEL__ + rbit r2, r2 @ For LE we need count-trailing-zeros +#endif + clz r2, r2 + add r0, r0, r2, lsr #3 @ Adjust the pointer to the found byte + s(sub) r0, r0, r1 @ Subtract input to compute length + bx lr + +END(strlen) + +libc_hidden_builtin_def (strlen) -- 1.8.1.2