From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa1-x2e.google.com (mail-oa1-x2e.google.com [IPv6:2001:4860:4864:20::2e]) by sourceware.org (Postfix) with ESMTPS id C17063858C53 for ; Fri, 2 Sep 2022 20:39:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org C17063858C53 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=linaro.org Received: by mail-oa1-x2e.google.com with SMTP id 586e51a60fabf-12243fcaa67so7572830fac.8 for ; Fri, 02 Sep 2022 13:39:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date; bh=T8fEHJK0oiH9zUpYJTZEKapkeQ48DNaYa/de4VBmzZ8=; b=FH3Sc75XRfE0JXiiCav8svinfOeoR5R5nCk0ZNgbLmkswgpkHcYH3WGvQJ4Zz1YAc8 ft68JZPKK6eM8OooRQqSR8YOarZnEcbGuVs8lv9BLM7XzbqBRVU7qGsqz8R7yWDF/Del wuG7ififumX7lAKJXzVLpO2EwPv6BVQhcajUlLQF2768Y4Sxw0Y9/94eVhI+b0TEGw/Y UijSDH2ykpdlL4c66EqpVL3Pmzv74ZTukrgTtZPNbT9HtV4HE63qowVLAQY0ZbrfbuzC 553npL7gGkHt5YnbB4/n5bE8U8X3fX8L6+JscBjWcYh200wDemaiOXw2Jb9Dw4U38bLQ dYLg== 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:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=T8fEHJK0oiH9zUpYJTZEKapkeQ48DNaYa/de4VBmzZ8=; b=fmdnSddSw1mNHsp1b75nNZvMgCzHNXvwj0IdNcpIw3D5xYRyS7Bn1HU8SznzOr3nd3 owpyLjc5ScDGltHtzmT8yFKUSjKnLFiZKrNrXj52O/SuUqawbulmjiPwFNZJriRf4w5O v/UHeOc0S5CAPhQpJXxbKaDW5ubWjgfrg1ma8mzw9EI0eJj3Iy+qdZfNaRZBu0BoqxiM IRZMWZcEfBdr/YXz6OoZdXw83nFCf2ei8tKXPnOzx0Tzebi/gMhlBlzx/F8ZiJO4Ncl7 /4NWlJuRHVyyFaFV0kglb77heirFwduKZf0BZcwlXCIQnSD6iWqYiNPb09mN3XweL5PH bMAg== X-Gm-Message-State: ACgBeo0ZHjZWiyXQLx9vUynIffRK5S4Qt1+Yv4n2P909ErACa4tvbUGJ 0EN6mYv8UuGEQdpH61Gm58bks5azJvFLzw== X-Google-Smtp-Source: AA6agR7jM/Kd29DXr+S6kXRvBTOB0jLP2Vl6WiNW4H+cArbpO6/1XuO9sGj75/aUNC6OhcLQ345FbA== X-Received: by 2002:a05:6870:15d3:b0:122:5c72:f21f with SMTP id k19-20020a05687015d300b001225c72f21fmr3202931oad.178.1662151199271; Fri, 02 Sep 2022 13:39:59 -0700 (PDT) Received: from mandiga.. ([2804:1b3:a7c0:dfed:72d1:946c:4eb1:ce5f]) by smtp.gmail.com with ESMTPSA id i27-20020a4a6f5b000000b00425678b9c4bsm1107902oof.0.2022.09.02.13.39.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Sep 2022 13:39:59 -0700 (PDT) From: Adhemerval Zanella To: libc-alpha@sourceware.org Cc: Joseph Myers , caiyinyu , Richard Henderson Subject: [PATCH 08/17] string: Improve generic strchrnul Date: Fri, 2 Sep 2022 17:39:31 -0300 Message-Id: <20220902203940.2385967-9-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220902203940.2385967-1-adhemerval.zanella@linaro.org> References: <20220902203940.2385967-1-adhemerval.zanella@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.7 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,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: New algorithm have the following key differences: - Reads first word unaligned and use string-maskoff function to remove unwanted data. This strategy follow arch-specific optimization used on aarch64 and powerpc. - Use string-fz{b,i} functions. 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 --- string/strchrnul.c | 156 +++--------------- .../power4/multiarch/strchrnul-ppc32.c | 4 - sysdeps/s390/strchrnul-c.c | 2 - 3 files changed, 24 insertions(+), 138 deletions(-) diff --git a/string/strchrnul.c b/string/strchrnul.c index 0cc1fc6bb0..67defa3dab 100644 --- a/string/strchrnul.c +++ b/string/strchrnul.c @@ -1,10 +1,5 @@ /* Copyright (C) 1991-2022 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 @@ -21,146 +16,43 @@ . */ #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. + /* Set up a word, each of whose bytes is C. */ + op_t repeated_c = repeat_bytes (c_in); - 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. + /* Align the input address to op_t. */ + uintptr_t s_int = (uintptr_t) str; + const op_t *word_ptr = word_containing (str); - 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! + /* Read the first aligned word, but force bytes before the string to + match neither zero nor goal (we make sure the high bit of each byte + is 1, and the low 7 bits are all the opposite of the goal byte). */ + op_t bmask = create_mask (s_int); + op_t word = (*word_ptr | bmask) ^ (repeated_c & highbit_mask (bmask)); - So it ignores everything except 128's, when they're aligned - properly. + while (! has_zero_eq (word, repeated_c)) + word = *++word_ptr; - 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; + op_t found = index_first_zero_eq (word, repeated_c); + return (char *) (word_ptr) + found; } - +#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 ed86b5e671..9c85e269f7 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 4ffac54edd..2ebbcc62f7 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 -- 2.34.1