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885306b2f6
While arm has the more important string functions in assembly, there are still a few generic routines used. Use the UQSUB8 insn for testing of zeros. Checked on armv7-linux-gnueabihf Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
67 lines
2.1 KiB
C
67 lines
2.1 KiB
C
/* Zero byte detection; basics. ARM version.
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Copyright (C) 2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _STRING_FZA_H
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#define _STRING_FZA_H 1
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#include <string-misc.h>
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#include <string-optype.h>
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/* The functions return a byte mask. */
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typedef op_t find_t;
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/* This function returns at least one bit set within every byte
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of X that is zero. */
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static __always_inline find_t
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find_zero_all (op_t x)
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{
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/* Use unsigned saturated subtraction from 1 in each byte.
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That leaves 1 for every byte that was zero. */
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op_t ones = repeat_bytes (0x01);
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return __builtin_arm_uqsub8 (ones, x);
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}
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/* Identify bytes that are equal between X1 and X2. */
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static __always_inline find_t
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find_eq_all (op_t x1, op_t x2)
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{
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return find_zero_all (x1 ^ x2);
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}
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/* Identify zero bytes in X1 or equality between X1 and X2. */
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static __always_inline find_t
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find_zero_eq_all (op_t x1, op_t x2)
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{
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return find_zero_all (x1) | find_zero_all (x1 ^ x2);
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}
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/* Identify zero bytes in X1 or inequality between X1 and X2. */
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static __always_inline find_t
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find_zero_ne_all (op_t x1, op_t x2)
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{
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/* Make use of the fact that we'll already have ONES in a register. */
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op_t ones = repeat_bytes (0x01);
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return find_zero_all (x1) | (find_zero_all (x1 ^ x2) ^ ones);
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}
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/* Define the "inexact" versions in terms of the exact versions. */
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#define find_zero_low find_zero_all
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#define find_eq_low find_eq_all
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#define find_zero_eq_low find_zero_eq_all
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#endif /* _STRING_FZA_H */
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