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gh-93033: Use wmemchr in stringlib (GH-93034)

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Generally comparable perf for the "good" case where memchr doesn't
return any collisions (false matches on lower byte) but clearly faster
with collisions.
This commit is contained in:
goldsteinn 2022-05-23 20:45:31 -05:00 • committed by GitHub
parent f7fabae75c
commit 7108bdf27c
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GPG key ID: 4AEE18F83AFDEB23
11 changed files with 39 additions and 14 deletions
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34
Objects/stringlib/fastsearch.h
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@ -39,7 +39,7 @@
#define STRINGLIB_BLOOM(mask, ch) \
((mask & (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1)))))
#if STRINGLIB_SIZEOF_CHAR == 1
#ifdef STRINGLIB_FAST_MEMCHR
# define MEMCHR_CUT_OFF 15
#else
# define MEMCHR_CUT_OFF 40
@ -53,8 +53,8 @@ STRINGLIB(find_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
p = s;
e = s + n;
if (n > MEMCHR_CUT_OFF) {
#if STRINGLIB_SIZEOF_CHAR == 1
p = memchr(s, ch, n);
#ifdef STRINGLIB_FAST_MEMCHR
p = STRINGLIB_FAST_MEMCHR(s, ch, n);
if (p != NULL)
return (p - s);
return -1;
@ -102,16 +102,26 @@ STRINGLIB(find_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
return -1;
}
#undef MEMCHR_CUT_OFF
#if STRINGLIB_SIZEOF_CHAR == 1
# define MEMRCHR_CUT_OFF 15
#else
# define MEMRCHR_CUT_OFF 40
#endif
Py_LOCAL_INLINE(Py_ssize_t)
STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
{
const STRINGLIB_CHAR *p;
#ifdef HAVE_MEMRCHR
/* memrchr() is a GNU extension, available since glibc 2.1.91.
it doesn't seem as optimized as memchr(), but is still quite
faster than our hand-written loop below */
/* memrchr() is a GNU extension, available since glibc 2.1.91. it
doesn't seem as optimized as memchr(), but is still quite
faster than our hand-written loop below. There is no wmemrchr
for 4-byte chars. */
if (n > MEMCHR_CUT_OFF) {
if (n > MEMRCHR_CUT_OFF) {
#if STRINGLIB_SIZEOF_CHAR == 1
p = memrchr(s, ch, n);
if (p != NULL)
@ -139,11 +149,11 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
if (*p == ch)
return n;
/* False positive */
if (n1 - n > MEMCHR_CUT_OFF)
if (n1 - n > MEMRCHR_CUT_OFF)
continue;
if (n <= MEMCHR_CUT_OFF)
if (n <= MEMRCHR_CUT_OFF)
break;
s1 = p - MEMCHR_CUT_OFF;
s1 = p - MEMRCHR_CUT_OFF;
while (p > s1) {
p--;
if (*p == ch)
@ -151,7 +161,7 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
}
n = p - s;
}
while (n > MEMCHR_CUT_OFF);
while (n > MEMRCHR_CUT_OFF);
}
#endif
}
@ -165,7 +175,7 @@ STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
return -1;
}
#undef MEMCHR_CUT_OFF
#undef MEMRCHR_CUT_OFF
/* Change to a 1 to see logging comments walk through the algorithm. */
#if 0 && STRINGLIB_SIZEOF_CHAR == 1