From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12795 invoked by alias); 6 Mar 2013 23:54:12 -0000 Received: (qmail 12779 invoked by uid 22791); 6 Mar 2013 23:54:11 -0000 X-SWARE-Spam-Status: No, hits=-5.0 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,FREEMAIL_ENVFROM_END_DIGIT,FREEMAIL_FROM,KHOP_RCVD_TRUST,KHOP_THREADED,RCVD_IN_DNSWL_LOW,RCVD_IN_HOSTKARMA_YE,SARE_SUB_6CONS_WORD,TW_CL,TW_DR,TW_OV,TW_QS X-Spam-Check-By: sourceware.org Received: from mail-pb0-f43.google.com (HELO mail-pb0-f43.google.com) (209.85.160.43) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 06 Mar 2013 23:54:04 +0000 Received: by mail-pb0-f43.google.com with SMTP id md12so6770171pbc.2 for ; Wed, 06 Mar 2013 15:54:03 -0800 (PST) X-Received: by 10.68.8.69 with SMTP id p5mr50113111pba.212.1362614043174; Wed, 06 Mar 2013 15:54:03 -0800 (PST) Received: from fremont.twiddle.net (50-194-63-110-static.hfc.comcastbusiness.net. [50.194.63.110]) by mx.google.com with ESMTPS id wm3sm33323746pbc.4.2013.03.06.15.54.01 (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Wed, 06 Mar 2013 15:54:02 -0800 (PST) From: Richard Henderson To: libc-ports@sourceware.org Cc: joseph@codesourcery.com Subject: [PATCH 3/5] arm: Implement armv6 optimized strchr Date: Wed, 06 Mar 2013 23:54:00 -0000 Message-Id: <1362614027-25800-4-git-send-email-rth@twiddle.net> In-Reply-To: <1362614027-25800-1-git-send-email-rth@twiddle.net> References: <1362614027-25800-1-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: 2013-03/txt/msg00059.txt.bz2 --- ports/sysdeps/arm/armv6/strchr.S | 143 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 143 insertions(+) create mode 100644 ports/sysdeps/arm/armv6/strchr.S diff --git a/ports/sysdeps/arm/armv6/strchr.S b/ports/sysdeps/arm/armv6/strchr.S new file mode 100644 index 0000000..c856283 --- /dev/null +++ b/ports/sysdeps/arm/armv6/strchr.S @@ -0,0 +1,143 @@ +/* strchr -- find the first instance of C in a nul-terminated string. + 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 (strchr) + @ r0 = start of string + @ r1 = character to match + @ returns NULL for no match, or a pointer to the match + ldrb r2, [r0] @ load the first byte asap + uxtb r1, r1 + + @ 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 + rsb r3, r3, #15 @ 16 - 1 peeled loop iteration + cmp r2, r1 @ Found C? + it ne + cmpne r2, #0 @ Found EOS? + beq 99f + + @ Loop until we find ... +1: ldrb r2, [r0, #1]! + subs r3, r3, #1 @ ... the aligment point + it ne + cmpne r2, r1 @ ... or the character + it ne + cmpne r2, #0 @ ... or EOS + bne 1b + + @ Disambiguate the exit possibilites above + cmp r2, r1 @ Found the character + it ne + cmpne r2, #0 @ Found EOS + beq 99f + add r0, r0, #1 + + @ So now we're aligned. Now we actually need a stack frame. + push { r4, r5, r6, r7 } + cfi_adjust_cfa_offset (16) + cfi_rel_offset (r4, 0) + cfi_rel_offset (r5, 4) + cfi_rel_offset (r6, 8) + cfi_rel_offset (r7, 12) + + ldrd r2, r3, [r0], #8 + orr r1, r1, r1, lsl #8 @ Replicate C to all bytes +#ifdef ARCH_HAS_T2 + movw ip, #0x0101 + pld [r0, #64] + movt ip, #0x0101 +#else + ldr ip, =0x01010101 + pld [r0, #64] +#endif + orr r1, r1, r1, lsl #16 + + @ Loop searching for EOS or C, 8 bytes at a time. +2: + @ Subtracting (unsigned saturating) from 1 means result of 1 for + @ any byte that was originally zero and 0 otherwise. Therefore + @ we consider the lsb of each byte the "found" bit. + uqsub8 r4, ip, r2 @ Find EOS + eor r6, r2, r1 @ Convert C bytes to 0 + uqsub8 r5, ip, r3 + eor r7, r3, r1 + uqsub8 r6, ip, r6 @ Find C + pld [r0, #128] @ Prefetch 2 lines ahead + uqsub8 r7, ip, r7 + orr r4, r4, r6 @ Combine found for EOS and C + orr r5, r5, r7 + orrs r6, r4, r5 @ Combine the two words + 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 contents of the word containing the match. + @ Adjust r4 to the found bits for the word containing the match. + cmp r4, #0 + sub r0, r0, #4 + itte eq + moveq r4, r5 + moveq r2, r3 + subne r0, r0, #4 + + @ Find the bit-offset of the match within the word. +#if defined(__ARMEL__) + @ For LE, swap the found word so clz searches from the little end. + rev r4, r4 +#else + @ For BE, byte swap the word to make it easier to extract the byte. + rev r2, r2 +#endif + @ We're counting 0x01 (not 0x80), so the bit offset is 7 too high. + clz r3, r4 + sub r3, r3, #7 + lsr r2, r2, r3 @ Shift down found byte + uxtb r1, r1 @ Undo replication of C + uxtb r2, r2 @ Extract found byte + add r0, r0, r3, lsr #3 @ Adjust the pointer to the found byte + + pop { r4, r5, r6, r7 } + cfi_adjust_cfa_offset (-16) + cfi_restore (r4) + cfi_restore (r5) + cfi_restore (r6) + cfi_restore (r7) + + @ Disambiguate between EOS and C. +99: + cmp r2, r1 + it ne + movne r0, #0 @ Found EOS, return NULL + bx lr + +END (strchr) + +weak_alias (strchr, index) +libc_hidden_builtin_def (strchr) -- 1.8.1.2