glibc/sysdeps/riscv/string-fza.h

/* Zero byte detection; basics.  RISCV version.
   Copyright (C) 2023-2024 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 _RISCV_STRING_FZA_H
#define _RISCV_STRING_FZA_H 1

#if defined __riscv_zbb || defined __riscv_xtheadbb
/* With bitmap extension we can use orc.b to find all zero bytes.  */
# include <string-misc.h>
# include <string-optype.h>

/* The functions return a byte mask.  */
typedef op_t find_t;

/* This function returns 0xff for each byte that is zero in X.  */
static __always_inline find_t
find_zero_all (op_t x)
{
  find_t r;
#ifdef __riscv_xtheadbb
  asm ("th.tstnbz %0, %1" : "=r" (r) : "r" (x));
  return r;
#else
  asm ("orc.b %0, %1" : "=r" (r) : "r" (x));
  return ~r;
#endif
}

/* This function returns 0xff for each byte that is equal between X1 and
   X2.  */
static __always_inline find_t
find_eq_all (op_t x1, op_t x2)
{
  return find_zero_all (x1 ^ x2);
}

/* Identify zero bytes in X1 or equality between X1 and X2.  */
static __always_inline find_t
find_zero_eq_all (op_t x1, op_t x2)
{
  return find_zero_all (x1) | find_eq_all (x1, x2);
}

/* Identify zero bytes in X1 or inequality between X1 and X2.  */
static __always_inline find_t
find_zero_ne_all (op_t x1, op_t x2)
{
  return find_zero_all (x1) | ~find_eq_all (x1, x2);
}

/* Define the "inexact" versions in terms of the exact versions.  */
# define find_zero_low		find_zero_all
# define find_eq_low		find_eq_all
# define find_zero_eq_low	find_zero_eq_all
#else
#include <sysdeps/generic/string-fza.h>
#endif

#endif /* _RISCV_STRING_FZA_H  */