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Make strcasestr() faster

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Justine Tunney 2024-12-12 22:50:20 -08:00
parent 22094ae9ca
commit c22b413ac4
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2 changed files with 133 additions and 0 deletions
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106
libc/str/strcasestr.c
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@ -17,9 +17,16 @@
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/str/str.h"
#include "libc/ctype.h"
#include "libc/mem/alloca.h"
#include "libc/runtime/stack.h"
#include "libc/str/tab.h"
#include "third_party/aarch64/arm_neon.internal.h"
#include "third_party/intel/immintrin.internal.h"
static int ToUpper(int c) {
return 'a' <= c && c <= 'z' ? c - ('a' - 'A') : c;
}
static void computeLPS(const char *pattern, long M, long *lps) {
long len = 0;
@ -84,5 +91,104 @@ static char *kmp(const char *s, size_t n, const char *ss, size_t m) {
* @see strstr()
*/
char *strcasestr(const char *haystack, const char *needle) {
if (haystack == needle || !*needle)
return (char *)haystack;
#if defined(__x86_64__) && !defined(__chibicc__)
size_t i;
unsigned k, m;
const __m128i *p;
long progress = 0;
__m128i v, nl, nu, z = _mm_setzero_si128();
const char *hay = haystack;
char first_lower = kToLower[*needle & 255];
char first_upper = ToUpper(*needle);
nl = _mm_set1_epi8(first_lower);
nu = _mm_set1_epi8(first_upper);
for (;;) {
k = (uintptr_t)hay & 15;
p = (const __m128i *)((uintptr_t)hay & -16);
v = _mm_load_si128(p);
m = _mm_movemask_epi8(_mm_or_si128(
_mm_or_si128(_mm_cmpeq_epi8(v, z), // Check for null terminator
_mm_cmpeq_epi8(v, nl)), // Check lowercase
_mm_cmpeq_epi8(v, nu))); // Check uppercase
m >>= k;
m <<= k;
while (!m) {
progress += 16;
v = _mm_load_si128(++p);
m = _mm_movemask_epi8(_mm_or_si128(
_mm_or_si128(_mm_cmpeq_epi8(v, z), _mm_cmpeq_epi8(v, nl)),
_mm_cmpeq_epi8(v, nu)));
}
int offset = __builtin_ctzl(m);
progress += offset;
hay = (const char *)p + offset;
for (i = 0;; ++i) {
if (--progress <= -512)
goto OfferPathologicalAssurances;
if (!needle[i])
return (char *)hay;
if (!hay[i])
break;
if (kToLower[needle[i] & 255] != kToLower[hay[i] & 255])
break;
}
if (!*hay++)
break;
}
return 0;
#elif defined(__aarch64__) && defined(__ARM_NEON)
size_t i;
const char *hay = haystack;
uint8_t first_lower = kToLower[*needle & 255];
uint8_t first_upper = ToUpper(*needle);
uint8x16_t nl = vdupq_n_u8(first_lower);
uint8x16_t nu = vdupq_n_u8(first_upper);
uint8x16_t z = vdupq_n_u8(0);
long progress = 0;
for (;;) {
int k = (uintptr_t)hay & 15;
hay = (const char *)((uintptr_t)hay & -16);
uint8x16_t v = vld1q_u8((const uint8_t *)hay);
uint8x16_t cmp_lower = vceqq_u8(v, nl);
uint8x16_t cmp_upper = vceqq_u8(v, nu);
uint8x16_t cmp_null = vceqq_u8(v, z);
uint8x16_t cmp = vorrq_u8(vorrq_u8(cmp_lower, cmp_upper), cmp_null);
uint8x8_t mask = vshrn_n_u16(vreinterpretq_u16_u8(cmp), 4);
uint64_t m;
vst1_u8((uint8_t *)&m, mask);
m >>= k * 4;
m <<= k * 4;
while (!m) {
hay += 16;
progress += 16;
v = vld1q_u8((const uint8_t *)hay);
cmp_lower = vceqq_u8(v, nl);
cmp_upper = vceqq_u8(v, nu);
cmp_null = vceqq_u8(v, z);
cmp = vorrq_u8(vorrq_u8(cmp_lower, cmp_upper), cmp_null);
mask = vshrn_n_u16(vreinterpretq_u16_u8(cmp), 4);
vst1_u8((uint8_t *)&m, mask);
}
int offset = __builtin_ctzll(m) >> 2;
progress += offset;
hay += offset;
for (i = 0;; ++i) {
if (--progress <= -512)
goto OfferPathologicalAssurances;
if (!needle[i])
return (char *)hay;
if (!hay[i])
break;
if (kToLower[needle[i] & 255] != kToLower[hay[i] & 255])
break;
}
if (!*hay++)
break;
}
return 0;
#endif
OfferPathologicalAssurances:
return kmp(haystack, strlen(haystack), needle, strlen(needle));
}