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AVX2 implementation for find either of two

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Kovid Goyal
2023-11-10 20:18:58 +05:30
parent e4c48a5f17
commit a0e1eb4985
1 changed files with 35 additions and 5 deletions
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40
kitty/simd-string.c
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@@ -124,6 +124,35 @@ find_either_of_two_bytes_sse4_2(uint8_t *haystack, const size_t sz, const uint8_
return ans;
}
static uint8_t*
find_either_of_two_bytes_avx2(uint8_t *haystack, size_t sz, const uint8_t a, const uint8_t b) {
const size_t extra = (uintptr_t)haystack % sizeof(__m256i);
if (extra) { // need aligned loads for performance so search first few bytes by hand
size_t es = MIN(sz, sizeof(__m256i) - extra);
uint8_t *ans = (has_sse4_2 && es > 15) ? find_either_of_two_bytes_sse4_2(haystack, es, a, b) : find_either_of_two_bytes_simple(haystack, es, a, b);
if (ans) return ans;
sz -= es;
haystack += es;
if (!sz) return NULL;
}
__m256i x = _mm256_set1_epi8(a);
__m256i y = _mm256_set1_epi8(b);
for (const uint8_t* limit = haystack + sz; haystack < limit; haystack += sizeof(__m256i)) {
__m256i chunk = _mm256_load_si256((__m256i*)(haystack));
__m256i x_cmp = _mm256_cmpeq_epi8(chunk, x);
__m256i y_cmp = _mm256_cmpeq_epi8(chunk, y);
__m256i matches = _mm256_or_si256(x_cmp, y_cmp);
const int mask = _mm256_movemask_epi8(matches);
if (mask != 0) {
// The trailing zeroes in mask give us the position of the first match
size_t pos = __builtin_ctz(mask);
if (haystack + pos < limit) return haystack + pos;
}
}
return NULL;
}
static uint8_t* (*find_either_of_two_bytes_impl)(uint8_t*, const size_t, const uint8_t, const uint8_t) = find_either_of_two_bytes_simple;
uint8_t*
@@ -195,10 +224,10 @@ find_byte_not_in_range_avx2(uint8_t *haystack, size_t sz, const uint8_t a, const
__m256i above_lower = _mm256_cmpgt_epi8(chunk, lower_bound);
__m256i below_upper = _mm256_cmpgt_epi8(upper_bound, chunk);
__m256i in_range = _mm256_and_si256(above_lower, below_upper);
int mask = _mm256_movemask_epi8(in_range);
if (mask != (int)0xFFFFFFFF) {
// The trailing zeroes in ~mask give us the position
const size_t pos = __builtin_ctz(~mask);
const int mask = ~_mm256_movemask_epi8(in_range); // ~ as we want not in range
if (mask != 0) {
// The trailing zeroes in mask give us the position of the first match on little endian
const int pos = __builtin_ctz(mask);
if (haystack + pos < limit) return haystack + pos;
}
}
@@ -221,13 +250,14 @@ init_simd(void *x) {
if (has_avx2) {
A(has_avx2, True);
find_byte_not_in_range_impl = find_byte_not_in_range_avx2;
find_either_of_two_bytes_impl = find_either_of_two_bytes_avx2;
} else {
A(has_avx2, False);
}
if (has_sse4_2) {
A(has_sse4_2, True);
if (find_byte_not_in_range == find_byte_not_in_range_simple) find_byte_not_in_range_impl = find_byte_not_in_range_sse4_2;
find_either_of_two_bytes_impl = find_either_of_two_bytes_sse4_2;
if (find_either_of_two_bytes_impl == find_either_of_two_bytes_simple) find_either_of_two_bytes_impl = find_either_of_two_bytes_sse4_2;
} else {
A(has_sse4_2, False);
}