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[209.132.180.131]) by mx.google.com with ESMTPS id u62si10482246pgc.587.2018.01.10.04.50.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jan 2018 04:50:13 -0800 (PST) Received-SPF: pass (google.com: domain of libc-alpha-return-89008-patch=linaro.org@sourceware.org designates 209.132.180.131 as permitted sender) client-ip=209.132.180.131; Authentication-Results: mx.google.com; dkim=pass header.i=@sourceware.org header.s=default header.b=X1VJOEgD; spf=pass (google.com: domain of libc-alpha-return-89008-patch=linaro.org@sourceware.org designates 209.132.180.131 as permitted sender) smtp.mailfrom=libc-alpha-return-89008-patch=linaro.org@sourceware.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id:in-reply-to :references; q=dns; s=default; b=c+yZ5mPXTxo8mkiX8A/gBoZbp4iZ6mF UraPWmGV5hmc9V1s+GqggIP4fswTVXyp47Zb5vM3R//RpSyMCYidr6SosByMpG2+ 9tb2BvkIuXUmgvj8nYL9JpwIzz/4es3ZhW58niBylT+A9G/gn6+TIw/DWE95r775 2ABJVzw0MF4o= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:date:message-id:in-reply-to :references; s=default; bh=9jcN/NRWWQezIwR0eMkoFT5QMXQ=; b=X1VJO EgDMWO0BszHD+sS0XsJd8CP1WVQvXznNGEx+yvpL54vlBG3c48s93InbqTah2Tqu 0rF55O007p70Zf0LwInuzswuQBkN0B5Y4ji4PD1ojF1BWr1rKvVV3A36Vcgp1xLi To1sAuzan3BVDTtb1mGwZJcl8x8ZwxaEDlJQVw= Received: (qmail 130280 invoked by alias); 10 Jan 2018 12:48:43 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 124477 invoked by uid 89); 10 Jan 2018 12:48:33 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-25.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mail-qk0-f193.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=wDf7DV7rAZpVhMS7uk2xqzkBRsQMwonSdgneY4Dhoq4=; b=b2RNuOYzodzObK7rZ5Xu3IOm+6C+0jArUZMAfp5Ad8UN0NrLgbS4qTUNtuIpUUQQr1 2bz+g9tDcsiDP2USzbl51Zc0NEKHBOMioPyye/N3AxuUG6RfltsJott7eWvcNBL2ZaOB fhI5sJz7zuVjeqACYeejsNp/Mg0ptA4zKWNTHi779GQ+KyFrAfwi5iPWnkXo5B6nkJCa A8gZsNO+2kkc1krgezN3ezV3Q4WXzTlF7I1YpQMVVqvdGbDIKx7A75HOLIjhqQIY6rRX Z8avzjvld2d0dpM3mdppkyahnmwLOIE6CcqyXMW4flnCcgW5vDiR/R/rkiGUIXwEC5za 3s3g== X-Gm-Message-State: AKwxytf0IJz2keISi67ojn2qtRYSH5XkzGrO5l6Gu/3ACnbZH/ekyL0n ub//Iu1fLq6nIYOv8ikHMBlrRhG1aTA= X-Received: by 10.55.53.205 with SMTP id c196mr14918336qka.311.1515588500021; Wed, 10 Jan 2018 04:48:20 -0800 (PST) From: Adhemerval Zanella To: libc-alpha@sourceware.org Cc: Richard Henderson Subject: [PATCH v3 07/18] string: Improve generic memrchr Date: Wed, 10 Jan 2018 10:47:51 -0200 Message-Id: <1515588482-15744-8-git-send-email-adhemerval.zanella@linaro.org> In-Reply-To: <1515588482-15744-1-git-send-email-adhemerval.zanella@linaro.org> References: <1515588482-15744-1-git-send-email-adhemerval.zanella@linaro.org> From: Richard Henderson New algorithm have the following key differences: - Use string-fz{b,i} functions. It also cleanups the multiple inclusion by leaving the ifunc implementation to undef the weak_alias. Checked on x86_64-linux-gnu, i686-linux-gnu, sparc64-linux-gnu, and sparcv9-linux-gnu by removing the arch-specific assembly implementation and disabling multi-arch (it covers both LE and BE for 64 and 32 bits). Richard Henderson Adhemerval Zanella [BZ #5806] * string/memrchr.c: Use string-fzb.h, string-fzi.h. * sysdeps/i386/i686/multiarch/memrchr-c.c: Redefined weak_alias. * sysdeps/s390/multiarch/memrchr-c.c: Likewise. --- string/memrchr.c | 193 +++++++------------------------- sysdeps/i386/i686/multiarch/memrchr-c.c | 2 + sysdeps/s390/multiarch/memrchr-c.c | 2 + 3 files changed, 44 insertions(+), 153 deletions(-) -- 2.7.4 diff --git a/string/memrchr.c b/string/memrchr.c index 191b89a..5ae9c81 100644 --- a/string/memrchr.c +++ b/string/memrchr.c @@ -21,177 +21,64 @@ License along with the GNU C Library; if not, see . */ -#include - -#ifdef HAVE_CONFIG_H -# include -#endif - -#if defined _LIBC -# include -# include -#endif - -#if defined HAVE_LIMITS_H || defined _LIBC -# include -#endif - -#define LONG_MAX_32_BITS 2147483647 - -#ifndef LONG_MAX -# define LONG_MAX LONG_MAX_32_BITS -#endif - -#include +#include +#include +#include +#include +#include +#include +#include #undef __memrchr #undef memrchr -#ifndef weak_alias -# define __memrchr memrchr +#ifndef MEMRCHR +# define MEMRCHR __memrchr #endif -/* Search no more than N bytes of S for C. */ void * -#ifndef MEMRCHR -__memrchr -#else -MEMRCHR -#endif - (const void *s, int c_in, size_t n) +MEMRCHR (const void *s, int c_in, size_t n) { - 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; + uintptr_t s_int = (uintptr_t) s; + uintptr_t lbyte_int = s_int + n; /* Handle the last 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 + n; - n > 0 && ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; - --n) - if (*--char_ptr == c) + Do this until CHAR_PTR is aligned on a word boundary, or + the entirety of small inputs. */ + const unsigned char *char_ptr = (const unsigned char *) lbyte_int; + size_t align = lbyte_int % sizeof (op_t); + if (n < OP_T_THRES || align > n) + align = n; + for (size_t i = 0; i < align; ++i) + if (*--char_ptr == c_in) 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 = (const 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; + const op_t *word_ptr = (const op_t *) char_ptr; + n -= align; + if (__glibc_unlikely (n == 0)) + return NULL; - /* Set up a longword, each of whose bytes is C. */ - charmask = c | (c << 8); - charmask |= charmask << 16; -#if LONG_MAX > LONG_MAX_32_BITS - charmask |= charmask << 32; -#endif - - /* 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. */ - while (n >= sizeof (longword)) - { - /* 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. - - 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. - - 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! - - So it ignores everything except 128's, when they're aligned - properly. - - 3) But wait! Aren't we looking for C, not 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 ^ charmask; + /* Compute the address of the word containing the initial byte. */ + const op_t *lword = (const op_t *) (s_int & -sizeof (op_t)); - /* Add MAGIC_BITS to LONGWORD. */ - if ((((longword + magic_bits) + /* Set up a word, each of whose bytes is C. */ + op_t repeated_c = repeat_bytes (c_in); - /* Set those bits that were unchanged by the addition. */ - ^ ~longword) + char *ret; + op_t word; - /* 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) - { - /* Which of the bytes was C? If none of them were, it was - a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) longword_ptr; - -#if LONG_MAX > 2147483647 - if (cp[7] == c) - return (void *) &cp[7]; - if (cp[6] == c) - return (void *) &cp[6]; - if (cp[5] == c) - return (void *) &cp[5]; - if (cp[4] == c) - return (void *) &cp[4]; -#endif - if (cp[3] == c) - return (void *) &cp[3]; - if (cp[2] == c) - return (void *) &cp[2]; - if (cp[1] == c) - return (void *) &cp[1]; - if (cp[0] == c) - return (void *) cp; - } - - n -= sizeof (longword); - } - - char_ptr = (const unsigned char *) longword_ptr; - - while (n-- > 0) + while (word_ptr != lword) { - if (*--char_ptr == c) - return (void *) char_ptr; + word = *--word_ptr; + if (has_eq (word, repeated_c)) + goto found; } + return NULL; - return 0; +found: + /* We found a match, but it might be in a byte past the start + of the array. */ + ret = (char *) word_ptr + index_last_eq (word, repeated_c); + return (ret >= (char*) s) ? ret : NULL; } -#ifndef MEMRCHR -# ifdef weak_alias weak_alias (__memrchr, memrchr) -# endif -#endif diff --git a/sysdeps/i386/i686/multiarch/memrchr-c.c b/sysdeps/i386/i686/multiarch/memrchr-c.c index ef7bbbe..23c937b 100644 --- a/sysdeps/i386/i686/multiarch/memrchr-c.c +++ b/sysdeps/i386/i686/multiarch/memrchr-c.c @@ -1,5 +1,7 @@ #if IS_IN (libc) # define MEMRCHR __memrchr_ia32 +# undef weak_alias +# define weak_alias(a,b) # include extern void *__memrchr_ia32 (const void *, int, size_t); #endif diff --git a/sysdeps/s390/multiarch/memrchr-c.c b/sysdeps/s390/multiarch/memrchr-c.c index 1e3c914..d7e59a4 100644 --- a/sysdeps/s390/multiarch/memrchr-c.c +++ b/sysdeps/s390/multiarch/memrchr-c.c @@ -18,6 +18,8 @@ #if defined HAVE_S390_VX_ASM_SUPPORT && IS_IN (libc) # define MEMRCHR __memrchr_c +# undef weak_alias +# define weak_alias(a,b) # include extern __typeof (__memrchr) __memrchr_c;