From patchwork Thu Feb 2 18:11:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella Netto X-Patchwork-Id: 64162 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 5ABEF38708F5 for ; Thu, 2 Feb 2023 18:12:43 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5ABEF38708F5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1675361563; bh=oXs45FA6nyUHujHuSEtxBV5sVi+ayKwCFcFW4lFwlSY=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=YNH5GsFjd2e3HA4jROtlbqvo48OJh5cnrJ5pEVctCm7UhhDYc0PqjyRuGz8tZGW+T N8inBVaf/cZz7lEYq9/xYLEPodeWb6On7mTKTZRgwJNvQxanynF4ynmG4u/93UWKc8 w7Ze2Gr1HsjaJ5CiylQSAOt55MsSvcxaUkTqI5JI= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-ot1-x330.google.com (mail-ot1-x330.google.com [IPv6:2607:f8b0:4864:20::330]) by sourceware.org (Postfix) with ESMTPS id 2BB0B3858416 for ; Thu, 2 Feb 2023 18:12:11 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2BB0B3858416 Received: by mail-ot1-x330.google.com with SMTP id d21-20020a056830005500b0068bd2e0b25bso698753otp.1 for ; Thu, 02 Feb 2023 10:12:11 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=oXs45FA6nyUHujHuSEtxBV5sVi+ayKwCFcFW4lFwlSY=; b=gQ63FJke8XT/5Nlk3HaRljzEBk6ZxndGmqePLfeB9iC+SCGSBba/5nHYGDbllCmsUL eH/B74VM1/1BXDH1PSfDbO1IE0PnOpKflVWXqhmf3IRssyoY2/U6GGBHURMxi0xEjA4+ VpX2DER8tPrFRZULO9jzU6IXx4Xmqtf/ArLh7ZsfuTAZWbpduXydzZSKy2M2178aqlfB iq6MnPg/V4oZUtf0/PiEv49pnSYGdS7TkD3pLRdbwLLpFFYMq8cEkB/oQh4uJNljz5YO YxyT1ti1tWc19jtOsq7DX3uVpXZalwmMED+OKnVgdxsJEDMWcDlYSKwY0vL6PPLsxTBs pFsQ== X-Gm-Message-State: AO0yUKUdtTiI/rxfzwHE3ZAKl3CAimXmIzsiZCVolC925EJUfB18NxOl E++3zkML3K8OuoRTbW1iMr+0sMycpyP6IM1rb80= X-Google-Smtp-Source: AK7set+PidC4e2LNUtwXbajv7cfNlPC/6G2n0kTU7OP4+y+rx+hmcPXaJhz1qygysCDr7YozJqENmA== X-Received: by 2002:a05:6830:2b1f:b0:68b:ba12:424d with SMTP id l31-20020a0568302b1f00b0068bba12424dmr5442741otv.29.1675361529504; Thu, 02 Feb 2023 10:12:09 -0800 (PST) Received: from mandiga.. ([2804:1b3:a7c2:1887:da12:b9d3:2162:a28c]) by smtp.gmail.com with ESMTPSA id ci10-20020a05683063ca00b00684a10970adsm126689otb.16.2023.02.02.10.12.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Feb 2023 10:12:08 -0800 (PST) To: libc-alpha@sourceware.org, Richard Henderson , Jeff Law , Xi Ruoyao , Noah Goldstein Subject: [PATCH v12 05/31] string: Improve generic strchrnul Date: Thu, 2 Feb 2023 15:11:23 -0300 Message-Id: <20230202181149.2181553-6-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230202181149.2181553-1-adhemerval.zanella@linaro.org> References: <20230202181149.2181553-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Adhemerval Zanella via Libc-alpha From: Adhemerval Zanella Netto Reply-To: Adhemerval Zanella Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" New algorithm read the first aligned address and mask off the unwanted bytes (this strategy is similar to arch-specific implementations used on powerpc, sparc, and sh). The loop now read word-aligned address and check using the has_zero_eq function. Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64-linux-gnu, and powerpc-linux-gnu by removing the arch-specific assembly implementation and disabling multi-arch (it covers both LE and BE for 64 and 32 bits). Co-authored-by: Richard Henderson Reviewed-by: Noah Goldstein Reviewed-by: Noah Goldstein --- string/strchrnul.c | 155 +++--------------- .../power4/multiarch/strchrnul-ppc32.c | 4 - sysdeps/s390/strchrnul-c.c | 2 - 3 files changed, 22 insertions(+), 139 deletions(-) diff --git a/string/strchrnul.c b/string/strchrnul.c index fa2db4b417..e7887fa285 100644 --- a/string/strchrnul.c +++ b/string/strchrnul.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2023 Free Software Foundation, Inc. This file is part of the GNU C Library. - Based on strlen implementation by Torbjorn Granlund (tege@sics.se), - with help from Dan Sahlin (dan@sics.se) and - bug fix and commentary by Jim Blandy (jimb@ai.mit.edu); - adaptation to strchr suggested by Dick Karpinski (dick@cca.ucsf.edu), - and implemented by Roland McGrath (roland@ai.mit.edu). The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public @@ -20,147 +15,41 @@ License along with the GNU C Library; if not, see . */ +#include +#include +#include +#include +#include #include -#include -#include #undef __strchrnul #undef strchrnul -#ifndef STRCHRNUL -# define STRCHRNUL __strchrnul +#ifdef STRCHRNUL +# define __strchrnul STRCHRNUL #endif /* Find the first occurrence of C in S or the final NUL byte. */ char * -STRCHRNUL (const char *s, int c_in) +__strchrnul (const char *str, int c_in) { - const unsigned char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, magic_bits, charmask; - unsigned char c; - - c = (unsigned char) c_in; - - /* Handle the first few characters by reading one character at a time. - Do this until CHAR_PTR is aligned on a longword boundary. */ - for (char_ptr = (const unsigned char *) s; - ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == c || *char_ptr == '\0') - return (void *) char_ptr; - - /* All these elucidatory comments refer to 4-byte longwords, - but the theory applies equally well to 8-byte longwords. */ - - longword_ptr = (unsigned long int *) char_ptr; - - /* Bits 31, 24, 16, and 8 of this number are zero. Call these bits - the "holes." Note that there is a hole just to the left of - each byte, with an extra at the end: - - bits: 01111110 11111110 11111110 11111111 - bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD - - The 1-bits make sure that carries propagate to the next 0-bit. - The 0-bits provide holes for carries to fall into. */ - magic_bits = -1; - magic_bits = magic_bits / 0xff * 0xfe << 1 >> 1 | 1; - - /* Set up a longword, each of whose bytes is C. */ - charmask = c | (c << 8); - charmask |= charmask << 16; - if (sizeof (longword) > 4) - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - charmask |= (charmask << 16) << 16; - if (sizeof (longword) > 8) - abort (); - - /* Instead of the traditional loop which tests each character, - we will test a longword at a time. The tricky part is testing - if *any of the four* bytes in the longword in question are zero. */ - for (;;) - { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. + /* Align pointer to sizeof op_t. */ + uintptr_t s_int = (uintptr_t) str; + const op_t *word_ptr = (const op_t *) PTR_ALIGN_DOWN (str, sizeof (op_t)); - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. + op_t repeated_c = repeat_bytes (c_in); - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! + op_t word = *word_ptr; + find_t mask = shift_find (find_zero_eq_all (word, repeated_c), s_int); + if (mask != 0) + return (char *) str + index_first (mask); - So it ignores everything except 128's, when they're aligned - properly. + do + word = *++word_ptr; + while (! has_zero_eq (word, repeated_c)); - 3) But wait! Aren't we looking for C as well as zero? - Good point. So what we do is XOR LONGWORD with a longword, - each of whose bytes is C. This turns each byte that is C - into a zero. */ - - longword = *longword_ptr++; - - /* Add MAGIC_BITS to LONGWORD. */ - if ((((longword + magic_bits) - - /* Set those bits that were unchanged by the addition. */ - ^ ~longword) - - /* Look at only the hole bits. If any of the hole bits - are unchanged, most likely one of the bytes was a - zero. */ - & ~magic_bits) != 0 - - /* That caught zeroes. Now test for C. */ - || ((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask)) - & ~magic_bits) != 0) - { - /* Which of the bytes was C or zero? - If none of them were, it was a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) (longword_ptr - 1); - - if (*cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (sizeof (longword) > 4) - { - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - if (*++cp == c || *cp == '\0') - return (char *) cp; - } - } - } - - /* This should never happen. */ - return NULL; + return (char *) word_ptr + index_first_zero_eq (word, repeated_c); } - +#ifndef STRCHRNUL weak_alias (__strchrnul, strchrnul) +#endif diff --git a/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c b/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c index 88ce5dfffa..da03ac7c04 100644 --- a/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c +++ b/sysdeps/powerpc/powerpc32/power4/multiarch/strchrnul-ppc32.c @@ -19,10 +19,6 @@ #include #define STRCHRNUL __strchrnul_ppc - -#undef weak_alias -#define weak_alias(a,b ) - extern __typeof (strchrnul) __strchrnul_ppc attribute_hidden; #include diff --git a/sysdeps/s390/strchrnul-c.c b/sysdeps/s390/strchrnul-c.c index e1248d1dbf..ff6aa38d4f 100644 --- a/sysdeps/s390/strchrnul-c.c +++ b/sysdeps/s390/strchrnul-c.c @@ -22,8 +22,6 @@ # if HAVE_STRCHRNUL_IFUNC # define STRCHRNUL STRCHRNUL_C # define __strchrnul STRCHRNUL -# undef weak_alias -# define weak_alias(name, alias) # endif # include