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avx512f-strstr.cpp
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avx512f-strstr.cpp
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/*
string - pointer to the string
n - string length in bytes
needle - pointer to another string
n - needle length in bytes
*/
size_t avx512f_strstr_long(const char* string, size_t n, const char* needle, size_t k) {
assert(n > 0);
assert(k > 4);
__m512i curr;
__m512i next;
__m512i v0, v1, v2, v3;
char* haystack = const_cast<char*>(string);
char* last = haystack + n;
const uint32_t prf = *(uint32_t*)needle; // the first 4 bytes of needle
const __m512i prefix = _mm512_set1_epi32(prf);
next = _mm512_loadu_si512(haystack);
for (/**/; haystack < last; haystack += 64) {
curr = next;
next = _mm512_loadu_si512(haystack + 64);
const __m512i shft = _mm512_alignr_epi32(next, curr, 1);
v0 = curr;
{
const __m512i t1 = _mm512_srli_epi32(curr, 8);
const __m512i t2 = _mm512_slli_epi32(shft, 24);
v1 = _mm512_or_si512(t1, t2);
}
{
const __m512i t1 = _mm512_srli_epi32(curr, 16);
const __m512i t2 = _mm512_slli_epi32(shft, 16);
v2 = _mm512_or_si512(t1, t2);
}
{
const __m512i t1 = _mm512_srli_epi32(curr, 24);
const __m512i t2 = _mm512_slli_epi32(shft, 8);
v3 = _mm512_or_si512(t1, t2);
}
uint16_t m0 = _mm512_cmpeq_epi32_mask(v0, prefix);
uint16_t m1 = _mm512_cmpeq_epi32_mask(v1, prefix);
uint16_t m2 = _mm512_cmpeq_epi32_mask(v2, prefix);
uint16_t m3 = _mm512_cmpeq_epi32_mask(v3, prefix);
int index = 64;
while (m0 | m1 | m2 | m3) {
if (m0) {
int pos = __builtin_ctz(m0) * 4 + 0;
m0 = m0 & (m0 - 1);
if (pos < index && memcmp(haystack + pos + 4, needle + 4, k - 4) == 0) {
index = pos;
}
}
if (m1) {
int pos = __builtin_ctz(m1) * 4 + 1;
m1 = m1 & (m1 - 1);
if (pos < index && memcmp(haystack + pos + 4, needle + 4, k - 4) == 0) {
index = pos;
}
}
if (m2) {
int pos = __builtin_ctz(m2) * 4 + 2;
m2 = m2 & (m2 - 1);
if (pos < index && memcmp(haystack + pos + 4, needle + 4, k - 4) == 0) {
index = pos;
}
}
if (m3) {
int pos = __builtin_ctz(m3) * 4 + 3;
m3 = m3 & (m3 - 1);
if (pos < index && memcmp(haystack + pos + 4, needle + 4, k - 4) == 0) {
index = pos;
}
}
}
if (index < 64) {
return (haystack - string) + index;
}
}
return size_t(-1);
}
// ------------------------------------------------------------------------
size_t avx512f_strstr_eq4(const char* string, size_t n, const char* needle) {
assert(n > 0);
__m512i curr;
__m512i next;
__m512i v0, v1, v2, v3;
char* haystack = const_cast<char*>(string);
char* last = haystack + n;
const uint32_t prf = *(uint32_t*)needle; // the first 4 bytes of needle
const __m512i prefix = _mm512_set1_epi32(prf);
next = _mm512_loadu_si512(haystack);
for (/**/; haystack < last; haystack += 64) {
curr = next;
next = _mm512_loadu_si512(haystack + 64);
const __m512i shft = _mm512_alignr_epi32(next, curr, 1);
v0 = curr;
{
const __m512i t1 = _mm512_srli_epi32(curr, 8);
const __m512i t2 = _mm512_slli_epi32(shft, 24);
v1 = _mm512_or_si512(t1, t2);
}
{
const __m512i t1 = _mm512_srli_epi32(curr, 16);
const __m512i t2 = _mm512_slli_epi32(shft, 16);
v2 = _mm512_or_si512(t1, t2);
}
{
const __m512i t1 = _mm512_srli_epi32(curr, 24);
const __m512i t2 = _mm512_slli_epi32(shft, 8);
v3 = _mm512_or_si512(t1, t2);
}
uint16_t m0 = _mm512_cmpeq_epi32_mask(v0, prefix);
uint16_t m1 = _mm512_cmpeq_epi32_mask(v1, prefix);
uint16_t m2 = _mm512_cmpeq_epi32_mask(v2, prefix);
uint16_t m3 = _mm512_cmpeq_epi32_mask(v3, prefix);
int index = 64;
if (m0) {
int pos = __builtin_ctz(m0) * 4 + 0;
if (pos < index) {
index = pos;
}
}
if (m1) {
int pos = __builtin_ctz(m1) * 4 + 1;
if (pos < index) {
index = pos;
}
}
if (m2) {
int pos = __builtin_ctz(m2) * 4 + 2;
if (pos < index) {
index = pos;
}
}
if (m3) {
int pos = __builtin_ctz(m3) * 4 + 3;
if (pos < index) {
index = pos;
}
}
if (index < 64) {
return (haystack - string) + index;
}
assert(m0 == 0 && m1 == 0 && m2 == 0 && m3 == 0);
}
return size_t(-1);
}
// ------------------------------------------------------------------------
size_t avx512f_strstr(const char* s, size_t n, const char* needle, size_t needle_size) {
size_t result = std::string::npos;
if (n < needle_size) {
return result;
}
switch (needle_size) {
case 0:
return 0;
case 1: {
const char* res = reinterpret_cast<const char*>(strchr(s, needle[0]));
return (res != nullptr) ? res - s : std::string::npos;
}
case 2:
case 3: {
const char* res = reinterpret_cast<const char*>(strstr(s, needle));
return (res != nullptr) ? res - s : std::string::npos;
}
case 4:
result = avx512f_strstr_eq4(s, n, needle);
break;
default:
result = avx512f_strstr_long(s, n, needle, needle_size);
break;
}
if (result <= n - needle_size) {
return result;
} else {
return std::string::npos;
}
}
// --------------------------------------------------
size_t avx512f_strstr(const std::string& s, const std::string& needle) {
return avx512f_strstr(s.data(), s.size(), needle.data(), needle.size());
}