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/* strspn with SSE4.2 intrinsics
Copyright (C) 2009-2025 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
<https://www.gnu.org/licenses/>. */
#include <nmmintrin.h>
#include <string.h>
#include "varshift.h"
/* We use 0x12:
_SIDD_SBYTE_OPS
| _SIDD_CMP_EQUAL_ANY
| _SIDD_NEGATIVE_POLARITY
| _SIDD_LEAST_SIGNIFICANT
on pcmpistri to compare xmm/mem128
0 1 2 3 4 5 6 7 8 9 A B C D E F
X X X X X X X X X X X X X X X X
against xmm
0 1 2 3 4 5 6 7 8 9 A B C D E F
A A A A A A A A A A A A A A A A
to find out if the first 16byte data element has any non-A byte and
the offset of the first byte. There are 2 cases:
1. The first 16byte data element has the non-A byte, including
EOS, at the offset X.
2. The first 16byte data element is valid and doesn't have the non-A
byte.
Here is the table of ECX, CFlag, ZFlag and SFlag for 2 cases:
case ECX CFlag ZFlag SFlag
1 X 1 0/1 0
2 16 0 0 0
We exit from the loop for case 1. */
extern size_t __strspn_generic (const char *, const char *) attribute_hidden;
#ifndef STRSPN
# define STRSPN __strspn_sse42
#endif
size_t
__attribute__ ((section (".text.sse4.2")))
STRSPN (const char *s, const char *a)
{
if (*a == 0)
return 0;
const char *aligned;
__m128i mask, maskz, zero;
unsigned int maskz_bits;
unsigned int offset = (int) ((size_t) a & 15);
zero = _mm_set1_epi8 (0);
if (offset != 0)
{
/* Load masks. */
aligned = (const char *) ((size_t) a & -16L);
__m128i mask0 = _mm_load_si128 ((__m128i *) aligned);
maskz = _mm_cmpeq_epi8 (mask0, zero);
/* Find where the NULL terminator is. */
maskz_bits = _mm_movemask_epi8 (maskz) >> offset;
if (maskz_bits != 0)
{
mask = __m128i_shift_right (mask0, offset);
offset = (unsigned int) ((size_t) s & 15);
if (offset)
goto start_unaligned;
aligned = s;
goto start_loop;
}
}
/* A is aligned. */
mask = _mm_loadu_si128 ((__m128i *) a);
/* Find where the NULL terminator is. */
maskz = _mm_cmpeq_epi8 (mask, zero);
maskz_bits = _mm_movemask_epi8 (maskz);
if (maskz_bits == 0)
{
/* There is no NULL terminator. Don't use SSE4.2 if the length
of A > 16. */
if (a[16] != 0)
return __strspn_generic (s, a);
}
aligned = s;
offset = (unsigned int) ((size_t) s & 15);
if (offset != 0)
{
start_unaligned:
/* Check partial string. */
aligned = (const char *) ((size_t) s & -16L);
__m128i value = _mm_load_si128 ((__m128i *) aligned);
__m128i adj_value = __m128i_shift_right (value, offset);
unsigned int length = _mm_cmpistri (mask, adj_value, 0x12);
/* No need to check CFlag since it is always 1. */
if (length < 16 - offset)
return length;
/* Find where the NULL terminator is. */
maskz = _mm_cmpeq_epi8 (value, zero);
maskz_bits = _mm_movemask_epi8 (maskz) >> offset;
if (maskz_bits != 0)
return length;
aligned += 16;
}
start_loop:
while (1)
{
__m128i value = _mm_load_si128 ((__m128i *) aligned);
unsigned int index = _mm_cmpistri (mask, value, 0x12);
unsigned int cflag = _mm_cmpistrc (mask, value, 0x12);
if (cflag)
return (size_t) (aligned + index - s);
aligned += 16;
}
}
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