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string.c (mrb_memsearch_ss): faster integer-wise substring search

Browse Source 
The function is based on @WojciechMula's code from the repository
https://github.com/WojciechMula/sse4-strstr.git Since it's licensed
under 2 clause BSD, we updated LEGAL file too.
This commit is contained in:
Yukihiro "Matz" Matsumoto
2024-01-26 23:57:25 +09:00
parent 08cd281200
commit 2943ca2685
2 changed files with 107 additions and 9 deletions
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src/string.c
+76 -9
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@@ -263,6 +263,15 @@ mrb_gc_free_str(mrb_state *mrb, struct RString *str)
mrb_free(mrb, str->as.heap.ptr);
}
#if defined(__i386) || defined(__i386__) || defined(_M_IX86) || \
defined(__x86_64) || defined(__x86_64__) || defined(_M_AMD64) || \
defined(__powerpc64__) || defined(__POWERPC__) || defined(__aarch64__) || \
defined(__mc68020__)
# define ALIGNED_WORD_ACCESS 0
#else
# define ALIGNED_WORD_ACCESS 1
#endif
#ifdef MRB_UTF8_STRING
#define NOASCII(c) ((c) & 0x80)
@@ -327,15 +336,6 @@ search_nonascii(const char *p, const char *e)
# define NONASCII_MASK 0x80808080UL
#endif
#if defined(__i386) || defined(__i386__) || defined(_M_IX86) || \
defined(__x86_64) || defined(__x86_64__) || defined(_M_AMD64) || \
defined(__powerpc64__) || defined(__POWERPC__) || defined(__aarch64__) || \
defined(__mc68020__)
# define ALIGNED_WORD_ACCESS 0
#else
# define ALIGNED_WORD_ACCESS 1
#endif
static const char*
search_nonascii(const char *p, const char *e)
{
@@ -564,6 +564,70 @@ str_index_str_by_char(mrb_state *mrb, mrb_value str, mrb_value sub, mrb_int pos)
#define str_index_str_by_char(mrb, str, sub, pos) str_index_str((mrb), (str), (sub), (pos))
#endif
/* The function is taken from https://github.com/WojciechMula/sse4-strstr.git */
/* The original source code is under 2 clause BSD license; see LEGAL file. */
/* The modifications:
* port from C++ to C
* takes unsigned char*
* returns mrb_int
* alignment adjustment added
*/
static inline mrb_int
mrb_memsearch_ss(const unsigned char *xs, long m, const unsigned char *ys, long n)
{
/* maximum pattern length */
#define MAX_PATLEN 100
#ifdef MRB_64BIT
#define bitint uint64_t
#define MASK1 0x0101010101010101llu
#define MASK2 0x7f7f7f7f7f7f7f7fllu
#define MASK3 0x8080808080808080llu
#else
#define bitint uint32_t
#define MASK1 0x01010101lu
#define MASK2 0x7f7f7f7flu
#define MASK3 0x80808080lu
#endif
#if ALIGNED_WORD_ACCESS
if ((uintptr_t)ys % sizeof(bitint)) {
int l = sizeof(bitint) - (bitint)ys % sizeof(bitint);
const unsigned char *p = (unsigned char*)memchr(ys, *xs, l);
if (p && (p - ys) < m) {
if (memcmp(p, xs, m) == 0) return (mrb_int)(p - ys);
ys = p;
}
}
#endif
const bitint first = MASK1 * (uint8_t)xs[0];
const bitint last = MASK1 * (uint8_t)xs[m-1];
bitint *s0 = (bitint*)(ys);
bitint *s1 = (bitint*)(ys+m-1);
for (mrb_int i=0; i < n; i+=sizeof(bitint), s0++, s1++) {
const bitint eq = (*s0 ^ first) | (*s1 ^ last);
bitint zeros = ((~eq & MASK2) + MASK1) & (~eq & MASK3);
size_t j = 0;
while (zeros) {
if (zeros & 0x80) {
const char* substr = (char*)s0 + j + 1;
if (memcmp(substr, xs + 1, m - 2) == 0) {
return i + j;
}
}
zeros >>= 8;
j += 1;
}
}
return -1;
}
static inline mrb_int
mrb_memsearch_qs(const unsigned char *xs, mrb_int m, const unsigned char *ys, mrb_int n)
{
@@ -625,6 +689,9 @@ mrb_memsearch(const char *x0, mrb_int m, const char *y0, mrb_int n)
}
return -1;
}
if (m <= MAX_PATLEN) {
return mrb_memsearch_ss((const unsigned char*)x0, m, (const unsigned char*)y0, n);
}
return mrb_memsearch_qs((const unsigned char*)x0, m, (const unsigned char*)y0, n);
}