glibc/sysdeps/generic/string-shift.h

/* Shift unaligned word read  Generic C 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
   <http://www.gnu.org/licenses/>.  */

#ifndef _STRING_SHIFT_H
#define _STRING_SHIFT_H 1

#include <endian.h>
#include <limits.h>
#include <stdint.h>
#include <string-fza.h>

/* Return the mask WORD shifted based on S_INT address value, to ignore
   values not presented in the aligned word read.  */
static __always_inline find_t
shift_find (find_t word, uintptr_t s)
{
  if (__BYTE_ORDER == __LITTLE_ENDIAN)
    return word >> (CHAR_BIT * (s % sizeof (op_t)));
  else
    return word << (CHAR_BIT * (s % sizeof (op_t)));
}

/* Mask off the bits defined for the S alignment value, or return WORD if
   S is 0.  */
static __always_inline find_t
shift_find_last (find_t word, uintptr_t s)
{
  s = s % sizeof (op_t);
  if (s == 0)
    return word;
  if (__BYTE_ORDER == __LITTLE_ENDIAN)
    return word & ~(((op_t)-1) << (s * CHAR_BIT));
  else
    return word & ~(((op_t)-1) >> (s * CHAR_BIT));
}

#endif /* _STRING_SHIFT_H */
Add string vectorized find and detection functions This patch adds generic string find and detection meant to be used in generic vectorized string implementation. The idea is to decompose the basic string operation so each architecture can reimplement if it provides any specialized hardware instruction. The 'string-misc.h' provides miscellaneous functions: - extractbyte: extracts the byte from an specific index. - repeat_bytes: setup an word by replicate the argument on each byte. The 'string-fza.h' provides zero byte detection functions: - find_zero_low, find_zero_all, find_eq_low, find_eq_all, find_zero_eq_low, find_zero_eq_all, and find_zero_ne_all The 'string-fzb.h' provides boolean zero byte detection functions: - has_zero: determine if any byte within a word is zero. - has_eq: determine byte equality between two words. - has_zero_eq: determine if any byte within a word is zero along with byte equality between two words. The 'string-fzi.h' provides positions for string-fza.h results: - index_first: return index of first zero byte within a word. - index_last: return index of first byte different between two words. The 'string-fzc.h' provides a combined version of fza and fzi: - index_first_zero_eq: return index of first zero byte within a word or first byte different between two words. - index_first_zero_ne: return index of first zero byte within a word or first byte equal between two words. - index_last_zero: return index of last zero byte within a word. - index_last_eq: return index of last byte different between two words. The 'string-shift.h' provides a way to mask off parts of a work based on some alignmnet (to handle unaligned arguments): - shift_find, shift_find_last. Co-authored-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com> 2023-01-10 21:00:53 +00:00			`/* Shift unaligned word read Generic C 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`
			`<http://www.gnu.org/licenses/>. */`

			`#ifndef _STRING_SHIFT_H`
			`#define _STRING_SHIFT_H 1`

			`#include <endian.h>`
			`#include <limits.h>`
			`#include <stdint.h>`
			`#include <string-fza.h>`

			`/* Return the mask WORD shifted based on S_INT address value, to ignore`
			`values not presented in the aligned word read. */`
			`static __always_inline find_t`
			`shift_find (find_t word, uintptr_t s)`
			`{`
			`if (__BYTE_ORDER == __LITTLE_ENDIAN)`
			`return word >> (CHAR_BIT * (s % sizeof (op_t)));`
			`else`
			`return word << (CHAR_BIT * (s % sizeof (op_t)));`
			`}`

			`/* Mask off the bits defined for the S alignment value, or return WORD if`
			`S is 0. */`
			`static __always_inline find_t`
			`shift_find_last (find_t word, uintptr_t s)`
			`{`
			`s = s % sizeof (op_t);`
			`if (s == 0)`
			`return word;`
			`if (__BYTE_ORDER == __LITTLE_ENDIAN)`
			`return word & ~(((op_t)-1) << (s * CHAR_BIT));`
			`else`
			`return word & ~(((op_t)-1) >> (s * CHAR_BIT));`
			`}`

			`#endif /* _STRING_SHIFT_H */`