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string.c (mrb_utf8_strlen): use SWAR technique for performance

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This commit is contained in:
Yukihiro "Matz" Matsumoto
2024-03-30 22:50:12 +09:00
parent 61b1a4db8e
commit cbb31e6a7c
1 changed files with 43 additions and 4 deletions
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src/string.c
+43 -4
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@@ -272,6 +272,14 @@ mrb_gc_free_str(mrb_state *mrb, struct RString *str)
# define ALIGNED_WORD_ACCESS 1
#endif
#ifdef MRB_64BIT
#define bitint uint64_t
#define MASK1 0x0101010101010101ull
#else
#define bitint uint32_t
#define MASK1 0x01010101ul
#endif
#ifdef MRB_UTF8_STRING
#define NOASCII(c) ((c) & 0x80)
@@ -421,15 +429,46 @@ mrb_utf8len(const char* p, const char* e)
return len;
}
#if defined(__GNUC__) || __has_builtin(__builtin_popcount)
# ifdef MRB_64BIT
# define popcount(x) __builtin_popcountll(x)
# else
# define popcount(x) __builtin_popcountl(x)
# endif
#else
static inline uint32_t popcount(bitint x)
{
x = (x & (MASK1*0x55)) + ((x >> 1) & (MASK1*0x55));
x = (x & (MASK1*0x33)) + ((x >> 2) & (MASK1*0x33));
x = (x & (MASK1*0x0F)) + ((x >> 4) & (MASK1*0x0F));
return (x * MASK1) >> 56;
}
#endif
mrb_int
mrb_utf8_strlen(const char *str, mrb_int byte_len)
{
mrb_int len = 0;
const char *p = str;
const char *e = p + byte_len;
while (p < e) {
if (utf8_islead(*p)) len++;
p++;
const char *be = p + sizeof(bitint) * (byte_len / sizeof(bitint));
for (; p < be; p+=sizeof(bitint)) {
bitint t0;
memcpy(&t0, p, sizeof(bitint));
const bitint t1 = t0 & (MASK1*0xc0);
const bitint t2 = t1 + (MASK1*0x40);
const bitint t3 = t1 & t2;
len += popcount(t3);
}
len = sizeof(bitint) * (byte_len / sizeof(bitint)) - len;
if (byte_len % sizeof(bitint)) {
const char *e = str + byte_len;
while (p < e) {
if (utf8_islead(*p)) len++;
p++;
}
}
return len;
}