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protobuf/third_party/utf8_range/range-avx2.c

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#ifdef __AVX2__
#include <stdio.h>
#include <stdint.h>
#include <x86intrin.h>
int utf8_naive(const unsigned char *data, int len);
#if 0
static void print256(const char *s, const __m256i v256)
{
const unsigned char *v8 = (const unsigned char *)&v256;
if (s)
printf("%s:\t", s);
for (int i = 0; i < 32; i++)
printf("%02x ", v8[i]);
printf("\n");
}
#endif
/*
* Map high nibble of "First Byte" to legal character length minus 1
* 0x00 ~ 0xBF --> 0
* 0xC0 ~ 0xDF --> 1
* 0xE0 ~ 0xEF --> 2
* 0xF0 ~ 0xFF --> 3
*/
static const int8_t _first_len_tbl[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 3,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 3,
};
/* Map "First Byte" to 8-th item of range table (0xC2 ~ 0xF4) */
static const int8_t _first_range_tbl[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, 8,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 8, 8, 8,
};
/*
* Range table, map range index to min and max values
* Index 0 : 00 ~ 7F (First Byte, ascii)
* Index 1,2,3: 80 ~ BF (Second, Third, Fourth Byte)
* Index 4 : A0 ~ BF (Second Byte after E0)
* Index 5 : 80 ~ 9F (Second Byte after ED)
* Index 6 : 90 ~ BF (Second Byte after F0)
* Index 7 : 80 ~ 8F (Second Byte after F4)
* Index 8 : C2 ~ F4 (First Byte, non ascii)
* Index 9~15 : illegal: i >= 127 && i <= -128
*/
static const int8_t _range_min_tbl[] = {
0x00, 0x80, 0x80, 0x80, 0xA0, 0x80, 0x90, 0x80,
0xC2, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F,
0x00, 0x80, 0x80, 0x80, 0xA0, 0x80, 0x90, 0x80,
0xC2, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F, 0x7F,
};
static const int8_t _range_max_tbl[] = {
0x7F, 0xBF, 0xBF, 0xBF, 0xBF, 0x9F, 0xBF, 0x8F,
0xF4, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
0x7F, 0xBF, 0xBF, 0xBF, 0xBF, 0x9F, 0xBF, 0x8F,
0xF4, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
};
/*
* Tables for fast handling of four special First Bytes(E0,ED,F0,F4), after
* which the Second Byte are not 80~BF. It contains "range index adjustment".
* +------------+---------------+------------------+----------------+
* | First Byte | original range| range adjustment | adjusted range |
* +------------+---------------+------------------+----------------+
* | E0 | 2 | 2 | 4 |
* +------------+---------------+------------------+----------------+
* | ED | 2 | 3 | 5 |
* +------------+---------------+------------------+----------------+
* | F0 | 3 | 3 | 6 |
* +------------+---------------+------------------+----------------+
* | F4 | 4 | 4 | 8 |
* +------------+---------------+------------------+----------------+
*/
/* index1 -> E0, index14 -> ED */
static const int8_t _df_ee_tbl[] = {
0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0,
0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0,
};
/* index1 -> F0, index5 -> F4 */
static const int8_t _ef_fe_tbl[] = {
0, 3, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 3, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
#define RET_ERR_IDX 0 /* Define 1 to return index of first error char */
static inline __m256i push_last_byte_of_a_to_b(__m256i a, __m256i b) {
return _mm256_alignr_epi8(b, _mm256_permute2x128_si256(a, b, 0x21), 15);
}
static inline __m256i push_last_2bytes_of_a_to_b(__m256i a, __m256i b) {
return _mm256_alignr_epi8(b, _mm256_permute2x128_si256(a, b, 0x21), 14);
}
static inline __m256i push_last_3bytes_of_a_to_b(__m256i a, __m256i b) {
return _mm256_alignr_epi8(b, _mm256_permute2x128_si256(a, b, 0x21), 13);
}
/* 5x faster than naive method */
/* Return 0 - success, -1 - error, >0 - first error char(if RET_ERR_IDX = 1) */
int utf8_range_avx2(const unsigned char *data, int len)
{
#if RET_ERR_IDX
int err_pos = 1;
#endif
if (len >= 32) {
__m256i prev_input = _mm256_set1_epi8(0);
__m256i prev_first_len = _mm256_set1_epi8(0);
/* Cached tables */
const __m256i first_len_tbl =
_mm256_loadu_si256((const __m256i *)_first_len_tbl);
const __m256i first_range_tbl =
_mm256_loadu_si256((const __m256i *)_first_range_tbl);
const __m256i range_min_tbl =
_mm256_loadu_si256((const __m256i *)_range_min_tbl);
const __m256i range_max_tbl =
_mm256_loadu_si256((const __m256i *)_range_max_tbl);
const __m256i df_ee_tbl =
_mm256_loadu_si256((const __m256i *)_df_ee_tbl);
const __m256i ef_fe_tbl =
_mm256_loadu_si256((const __m256i *)_ef_fe_tbl);
#if !RET_ERR_IDX
__m256i error1 = _mm256_set1_epi8(0);
__m256i error2 = _mm256_set1_epi8(0);
#endif
while (len >= 32) {
const __m256i input = _mm256_loadu_si256((const __m256i *)data);
/* high_nibbles = input >> 4 */
const __m256i high_nibbles =
_mm256_and_si256(_mm256_srli_epi16(input, 4), _mm256_set1_epi8(0x0F));
/* first_len = legal character length minus 1 */
/* 0 for 00~7F, 1 for C0~DF, 2 for E0~EF, 3 for F0~FF */
/* first_len = first_len_tbl[high_nibbles] */
__m256i first_len = _mm256_shuffle_epi8(first_len_tbl, high_nibbles);
/* First Byte: set range index to 8 for bytes within 0xC0 ~ 0xFF */
/* range = first_range_tbl[high_nibbles] */
__m256i range = _mm256_shuffle_epi8(first_range_tbl, high_nibbles);
/* Second Byte: set range index to first_len */
/* 0 for 00~7F, 1 for C0~DF, 2 for E0~EF, 3 for F0~FF */
/* range |= (first_len, prev_first_len) << 1 byte */
range = _mm256_or_si256(
range, push_last_byte_of_a_to_b(prev_first_len, first_len));
/* Third Byte: set range index to saturate_sub(first_len, 1) */
/* 0 for 00~7F, 0 for C0~DF, 1 for E0~EF, 2 for F0~FF */
__m256i tmp1, tmp2;
/* tmp1 = (first_len, prev_first_len) << 2 bytes */
tmp1 = push_last_2bytes_of_a_to_b(prev_first_len, first_len);
/* tmp2 = saturate_sub(tmp1, 1) */
tmp2 = _mm256_subs_epu8(tmp1, _mm256_set1_epi8(1));
/* range |= tmp2 */
range = _mm256_or_si256(range, tmp2);
/* Fourth Byte: set range index to saturate_sub(first_len, 2) */
/* 0 for 00~7F, 0 for C0~DF, 0 for E0~EF, 1 for F0~FF */
/* tmp1 = (first_len, prev_first_len) << 3 bytes */
tmp1 = push_last_3bytes_of_a_to_b(prev_first_len, first_len);
/* tmp2 = saturate_sub(tmp1, 2) */
tmp2 = _mm256_subs_epu8(tmp1, _mm256_set1_epi8(2));
/* range |= tmp2 */
range = _mm256_or_si256(range, tmp2);
/*
* Now we have below range indices calculated
* Correct cases:
* - 8 for C0~FF
* - 3 for 1st byte after F0~FF
* - 2 for 1st byte after E0~EF or 2nd byte after F0~FF
* - 1 for 1st byte after C0~DF or 2nd byte after E0~EF or
* 3rd byte after F0~FF
* - 0 for others
* Error cases:
* 9,10,11 if non ascii First Byte overlaps
* E.g., F1 80 C2 90 --> 8 3 10 2, where 10 indicates error
*/
/* Adjust Second Byte range for special First Bytes(E0,ED,F0,F4) */
/* Overlaps lead to index 9~15, which are illegal in range table */
__m256i shift1, pos, range2;
/* shift1 = (input, prev_input) << 1 byte */
shift1 = push_last_byte_of_a_to_b(prev_input, input);
pos = _mm256_sub_epi8(shift1, _mm256_set1_epi8(0xEF));
/*
* shift1: | EF F0 ... FE | FF 00 ... ... DE | DF E0 ... EE |
* pos: | 0 1 15 | 16 17 239| 240 241 255|
* pos-240: | 0 0 0 | 0 0 0 | 0 1 15 |
* pos+112: | 112 113 127| >= 128 | >= 128 |
*/
tmp1 = _mm256_subs_epu8(pos, _mm256_set1_epi8(240));
range2 = _mm256_shuffle_epi8(df_ee_tbl, tmp1);
tmp2 = _mm256_adds_epu8(pos, _mm256_set1_epi8(112));
range2 = _mm256_add_epi8(range2, _mm256_shuffle_epi8(ef_fe_tbl, tmp2));
range = _mm256_add_epi8(range, range2);
/* Load min and max values per calculated range index */
__m256i minv = _mm256_shuffle_epi8(range_min_tbl, range);
__m256i maxv = _mm256_shuffle_epi8(range_max_tbl, range);
/* Check value range */
#if RET_ERR_IDX
__m256i error = _mm256_cmpgt_epi8(minv, input);
error = _mm256_or_si256(error, _mm256_cmpgt_epi8(input, maxv));
/* 5% performance drop from this conditional branch */
if (!_mm256_testz_si256(error, error))
break;
#else
error1 = _mm256_or_si256(error1, _mm256_cmpgt_epi8(minv, input));
error2 = _mm256_or_si256(error2, _mm256_cmpgt_epi8(input, maxv));
#endif
prev_input = input;
prev_first_len = first_len;
data += 32;
len -= 32;
#if RET_ERR_IDX
err_pos += 32;
#endif
}
#if RET_ERR_IDX
/* Error in first 16 bytes */
if (err_pos == 1)
goto do_naive;
#else
__m256i error = _mm256_or_si256(error1, error2);
if (!_mm256_testz_si256(error, error))
return -1;
#endif
/* Find previous token (not 80~BF) */
int32_t token4 = _mm256_extract_epi32(prev_input, 7);
const int8_t *token = (const int8_t *)&token4;
int lookahead = 0;
if (token[3] > (int8_t)0xBF)
lookahead = 1;
else if (token[2] > (int8_t)0xBF)
lookahead = 2;
else if (token[1] > (int8_t)0xBF)
lookahead = 3;
data -= lookahead;
len += lookahead;
#if RET_ERR_IDX
err_pos -= lookahead;
#endif
}
/* Check remaining bytes with naive method */
#if RET_ERR_IDX
int err_pos2;
do_naive:
err_pos2 = utf8_naive(data, len);
if (err_pos2)
return err_pos + err_pos2 - 1;
return 0;
#else
return utf8_naive(data, len);
#endif
}
#endif