From patchwork Wed Feb 1 17:03:41 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: 64093 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 77BC538493CD for ; Wed, 1 Feb 2023 17:05:38 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 77BC538493CD DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1675271138; bh=v0Sm1CAMqISIDo3nZ3nOiwklWvA5gNWemviyMGtw4kE=; 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=laeoKvNMAjtfyZn4hlG44exCbyVnQ47ypl1k4BvzPhT+0a8Bp6c9mKtwjGX1wLJnj lW/a1y+ZRvTu67F/Xk+mrZyeKpPgQcG+wXFSYPAw9cQmca2TCw6T2cx/pklC+bcSWh QUTwNw0ln3lU2ugqOvUcM92saieQc+m4ecamTNbs= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-oi1-x232.google.com (mail-oi1-x232.google.com [IPv6:2607:f8b0:4864:20::232]) by sourceware.org (Postfix) with ESMTPS id 7067C38582BE for ; Wed, 1 Feb 2023 17:04:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 7067C38582BE Received: by mail-oi1-x232.google.com with SMTP id bg12so9637973oib.5 for ; Wed, 01 Feb 2023 09:04:25 -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=v0Sm1CAMqISIDo3nZ3nOiwklWvA5gNWemviyMGtw4kE=; b=rFqQDFJXcADuGUViOxah5+W3hpyiwLvrVEu4N8VvSHeaqMDsuhsbcWOrUXRkj/1lAH au/3kZD3CBTOv0VOv4Kf5nnikDPHZAoHxPFIZQrTsPwslDAPjNtz1EpGr3gAEhu+qlev 4zH4nHeAH1ANam8fP9ixikNhOcW28UzTxG5oCi5La9L04qi6t84Wlp6OT8Rg/fE7p0si /WTD1oCZWYFs+qKOznktUCUnJ5kyNTf44cnuM2LRgGhy8WWRFpBH8EYmuya3HQfstdlR ECGo56RwnNDZ8dxML5Z9OdAFECGMph3H1EhxPPeIXMAaSYkI4xOqCUzQ7nnSbu+O7uGc J3Sg== X-Gm-Message-State: AO0yUKV15qBnzq6u2bceB60F/rxo4KJTc++W4bf0kkCNXzBhuUKp0743 JzX4Nq7b62e4KwgqQfQwua4k9hXgeHoVe9xVA5Y= X-Google-Smtp-Source: AK7set92P1Mlc/8jrolv4CusOmvimcIrFM20VI6AL3e0nthrpPnw1h4MSW90/sPEdEPMV7P+67mhLg== X-Received: by 2002:a05:6808:1521:b0:378:7986:d8d with SMTP id u33-20020a056808152100b0037879860d8dmr1614051oiw.15.1675271063725; Wed, 01 Feb 2023 09:04:23 -0800 (PST) Received: from mandiga.. ([2804:1b3:a7c2:1887:d2ed:98c2:d2cc:bf06]) by smtp.gmail.com with ESMTPSA id b17-20020a056830311100b006863ccbf067sm8077090ots.74.2023.02.01.09.04.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Feb 2023 09:04:23 -0800 (PST) To: libc-alpha@sourceware.org, Richard Henderson , Noah Goldstein , Jeff Law , Xi Ruoyao Subject: [PATCH v11 04/29] string: Improve generic strlen Date: Wed, 1 Feb 2023 14:03:41 -0300 Message-Id: <20230201170406.303978-5-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230201170406.303978-1-adhemerval.zanella@linaro.org> References: <20230201170406.303978-1-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 macro. Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu, and powercp64-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 --- string/strlen.c | 92 ++++++++++------------------------------- sysdeps/s390/strlen-c.c | 10 +++-- 2 files changed, 28 insertions(+), 74 deletions(-) diff --git a/string/strlen.c b/string/strlen.c index ee1aae0fff..5a4424f9a5 100644 --- a/string/strlen.c +++ b/string/strlen.c @@ -15,86 +15,38 @@ License along with the GNU C Library; if not, see . */ +#include +#include +#include +#include +#include #include -#include -#undef strlen - -#ifndef STRLEN -# define STRLEN strlen +#ifdef STRLEN +# define __strlen STRLEN #endif /* Return the length of the null-terminated string STR. Scan for the null terminator quickly by testing four bytes at a time. */ size_t -STRLEN (const char *str) +__strlen (const char *str) { - const char *char_ptr; - const unsigned long int *longword_ptr; - unsigned long int longword, himagic, lomagic; - - /* 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 = str; ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; - ++char_ptr) - if (*char_ptr == '\0') - return char_ptr - str; - - /* 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; + /* Align pointer to sizeof op_t. */ + const uintptr_t s_int = (uintptr_t) str; + const op_t *word_ptr = (const op_t*) PTR_ALIGN_DOWN (str, sizeof (op_t)); - /* Computing (longword - lomagic) sets the high bit of any corresponding - byte that is either zero or greater than 0x80. The latter case can be - filtered out by computing (~longword & himagic). The final result - will always be non-zero if one of the bytes of longword is zero. */ - himagic = 0x80808080L; - lomagic = 0x01010101L; - if (sizeof (longword) > 4) - { - /* 64-bit version of the magic. */ - /* Do the shift in two steps to avoid a warning if long has 32 bits. */ - himagic = ((himagic << 16) << 16) | himagic; - lomagic = ((lomagic << 16) << 16) | lomagic; - } - if (sizeof (longword) > 8) - abort (); + op_t word = *word_ptr; + find_t mask = shift_find (find_zero_all (word), s_int); + if (mask != 0) + return index_first (mask); - /* 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 (;;) - { - longword = *longword_ptr++; + do + word = *++word_ptr; + while (! has_zero (word)); - if (((longword - lomagic) & ~longword & himagic) != 0) - { - /* Which of the bytes was the zero? */ - - const char *cp = (const char *) (longword_ptr - 1); - - if (cp[0] == 0) - return cp - str; - if (cp[1] == 0) - return cp - str + 1; - if (cp[2] == 0) - return cp - str + 2; - if (cp[3] == 0) - return cp - str + 3; - if (sizeof (longword) > 4) - { - if (cp[4] == 0) - return cp - str + 4; - if (cp[5] == 0) - return cp - str + 5; - if (cp[6] == 0) - return cp - str + 6; - if (cp[7] == 0) - return cp - str + 7; - } - } - } + return ((const char *) word_ptr) + index_first_zero (word) - str; } +#ifndef STRLEN +weak_alias (__strlen, strlen) libc_hidden_builtin_def (strlen) +#endif diff --git a/sysdeps/s390/strlen-c.c b/sysdeps/s390/strlen-c.c index b829ef2452..0a33a6f8e5 100644 --- a/sysdeps/s390/strlen-c.c +++ b/sysdeps/s390/strlen-c.c @@ -21,12 +21,14 @@ #if HAVE_STRLEN_C # if HAVE_STRLEN_IFUNC # define STRLEN STRLEN_C +# endif + +# include + +# if HAVE_STRLEN_IFUNC # if defined SHARED && IS_IN (libc) -# undef libc_hidden_builtin_def -# define libc_hidden_builtin_def(name) \ - __hidden_ver1 (__strlen_c, __GI_strlen, __strlen_c); +__hidden_ver1 (__strlen_c, __GI_strlen, __strlen_c); # endif # endif -# include #endif