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[63.157.97.90]) by smtp.gmail.com with ESMTPSA id z15-20020a170903018f00b00189f2fdc178sm8806061plg.177.2023.01.10.18.45.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jan 2023 18:45:22 -0800 (PST) Message-ID: Date: Tue, 10 Jan 2023 18:45:20 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v6 14/17] alpha: Add string-fzb.h and string-fzi.h Content-Language: en-US To: Adhemerval Zanella , libc-alpha@sourceware.org, Noah Goldstein References: <20230110210106.1457686-1-adhemerval.zanella@linaro.org> <20230110210106.1457686-15-adhemerval.zanella@linaro.org> From: Richard Henderson In-Reply-To: <20230110210106.1457686-15-adhemerval.zanella@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-10.3 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_SBL_CSS,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 List-Id: On 1/10/23 13:01, Adhemerval Zanella wrote: > From: Richard Henderson > > While alpha has the more important string functions in assembly, > there are still a few for find the generic routines are used. > > Use the CMPBGE insn, via the builtin, for testing of zeros. Use a > simplified expansion of __builtin_ctz when the insn isn't available. > > Checked on alpha-linux-gnu. > --- > sysdeps/alpha/string-fzb.h | 52 +++++++++++++++++ > sysdeps/alpha/string-fzi.h | 113 +++++++++++++++++++++++++++++++++++++ > 2 files changed, 165 insertions(+) > create mode 100644 sysdeps/alpha/string-fzb.h > create mode 100644 sysdeps/alpha/string-fzi.h > > diff --git a/sysdeps/alpha/string-fzb.h b/sysdeps/alpha/string-fzb.h > new file mode 100644 > index 0000000000..e3934ba413 > --- /dev/null > +++ b/sysdeps/alpha/string-fzb.h > @@ -0,0 +1,52 @@ > +/* Zero byte detection; boolean. Alpha version. > + Copyright (C) 2023 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 > + . */ > + > +#ifndef _STRING_FZB_H > +#define _STRING_FZB_H 1 > + > +#include > +#include > + > +/* Note that since CMPBGE creates a bit mask rather than a byte mask, > + we cannot simply provide a target-specific string-fza.h. */ > + > +/* Determine if any byte within X is zero. This is a pure boolean test. */ > + > +static __always_inline _Bool > +has_zero (op_t x) > +{ > + return __builtin_alpha_cmpbge (0, x) != 0; > +} > + > +/* Likewise, but for byte equality between X1 and X2. */ > + > +static __always_inline _Bool > +has_eq (op_t x1, op_t x2) > +{ > + return has_zero (x1 ^ x2); > +} > + > +/* Likewise, but for zeros in X1 and equal bytes between X1 and X2. */ > + > +static __always_inline _Bool > +has_zero_eq (op_t x1, op_t x2) > +{ > + return has_zero (x1) | has_eq (x1, x2); > +} > + > +#endif /* _STRING_FZB_H */ > diff --git a/sysdeps/alpha/string-fzi.h b/sysdeps/alpha/string-fzi.h > new file mode 100644 > index 0000000000..bc2f0bdc91 > --- /dev/null > +++ b/sysdeps/alpha/string-fzi.h > @@ -0,0 +1,113 @@ > +/* string-fzi.h -- zero byte detection; indices. Alpha version. > + Copyright (C) 2022 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 > + . */ > + > +#ifndef _STRING_FZI_H > +#define _STRING_FZI_H > + > +#include > +#include > + > +/* Note that since CMPBGE creates a bit mask rather than a byte mask, > + we cannot simply provide a target-specific string-fza.h. */ > + > +/* A subroutine for the index_zero functions. Given a bitmask C, > + return the index of the first bit set in memory order. */ > + > +static __always_inline unsigned int > +index_first (unsigned long int c) > +{ > +#ifdef __alpha_cix__ > + return __builtin_ctzl (c); > +#else > + c = c & -c; > + return (c & 0xf0 ? 4 : 0) + (c & 0xcc ? 2 : 0) + (c & 0xaa ? 1 : 0); > +#endif > +} > + > +/* Similarly, but return the (memory order) index of the last bit > + that is non-zero. Note that only the least 8 bits may be nonzero. */ > + > +static __always_inline unsigned int > +index_last (unsigned long int x) > +{ > +#ifdef __alpha_cix__ > + return __builtin_clzl (x) ^ 63; > +#else > + unsigned r = 0; > + if (x & 0xf0) > + r += 4; > + if (x & (0xc << r)) > + r += 2; > + if (x & (0x2 << r)) > + r += 1; > + return r; > +#endif > +} > + > +/* Given a word X that is known to contain a zero byte, return the > + index of the first such within the word in memory order. */ > + > +static __always_inline unsigned int > +index_first_zero (op_t x) > +{ > + return index_first (__builtin_alpha_cmpbge (0, x)); The header split has drifted somewhat since the original: string-fza.h is missing and check_mask() seems misplaced. In particular, from strchrnul, + op_t mask = check_mask (find_zero_eq_all (word, repeated_c), s_int); + if (mask != 0) + return (char *) str + index_first (mask); We're using the generic find_zero_eq_all, then (correctly, for the moment) the generic check_mask, and then incorrectly the alpha-specific index_first. We want to use an alpha-specific find_zero_eq_all (using cmpbge), an alpha-specific check_mask (shifting by bits, not bytes), and an alpha-specific index_first (searching only 8 low bits, not a full ctz). I wonder if it makes sense to introduce a target-specific find_t, making it clear that it's not the same type as op_t (for alpha, int instead of unsigned long (uint8_t having it's own issues on ancient alpha ev5)). I think check_mask (possibly renamed shift_find?) should belong in string-fza.h to match the implementation therein, or within a new header (possibly along with find_t?). Anyway, even the current set of headers would work, so long as Alpha implements all of them. r~