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gh-127417: fix UTF-8 decoder optimization on AIX (#127433)

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Inada Naoki 2024-11-30 21:52:37 +09:00 • committed by GitHub
parent 49f15d8667
commit 7043bbd1ca
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1 changed files with 14 additions and 10 deletions
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24
Objects/unicodeobject.c
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@ -5014,21 +5014,26 @@ ctz(size_t v)
#endif /* SIZEOF_SIZE_T */
return pos;
}
#else
#define HAVE_CTZ 0
#endif
#if HAVE_CTZ
// load p[0]..p[size-1] as a little-endian size_t
// without unaligned access nor read ahead.
#if HAVE_CTZ && PY_LITTLE_ENDIAN
// load p[0]..p[size-1] as a size_t without unaligned access nor read ahead.
static size_t
load_unaligned(const unsigned char *p, size_t size)
{
assert(size <= SIZEOF_SIZE_T);
union {
size_t s;
unsigned char b[SIZEOF_SIZE_T];
} u;
u.s = 0;
// This switch statement assumes little endian because:
// * union is faster than bitwise or and shift.
// * big endian machine is rare and hard to maintain.
switch (size) {
default:
#if SIZEOF_SIZE_T == 8
case 8:
u.b[7] = p[7];
_Py_FALLTHROUGH;
@ -5041,6 +5046,7 @@ load_unaligned(const unsigned char *p, size_t size)
case 5:
u.b[4] = p[4];
_Py_FALLTHROUGH;
#endif
case 4:
u.b[3] = p[3];
_Py_FALLTHROUGH;
@ -5055,8 +5061,6 @@ load_unaligned(const unsigned char *p, size_t size)
break;
case 0:
break;
default:
Py_UNREACHABLE();
}
return u.s;
}
@ -5077,8 +5081,8 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)
if (end - start >= SIZEOF_SIZE_T) {
const unsigned char *p2 = _Py_ALIGN_UP(p, SIZEOF_SIZE_T);
#if PY_LITTLE_ENDIAN && HAVE_CTZ
if (p < p2) {
#if HAVE_CTZ
#if defined(_M_AMD64) || defined(_M_IX86) || defined(__x86_64__) || defined(__i386__)
// x86 and amd64 are little endian and can load unaligned memory.
size_t u = *(const size_t*)p & ASCII_CHAR_MASK;
@ -5086,11 +5090,11 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)
size_t u = load_unaligned(p, p2 - p) & ASCII_CHAR_MASK;
#endif
if (u) {
return p - start + (ctz(u) - 7) / 8;
return (ctz(u) - 7) / 8;
}
p = p2;
}
#else
#else /* PY_LITTLE_ENDIAN && HAVE_CTZ */
while (p < p2) {
if (*p & 0x80) {
return p - start;
@ -5113,7 +5117,7 @@ find_first_nonascii(const unsigned char *start, const unsigned char *end)
p += SIZEOF_SIZE_T;
}
}
#if HAVE_CTZ
#if PY_LITTLE_ENDIAN && HAVE_CTZ
// we can not use *(const size_t*)p to avoid buffer overrun.
size_t u = load_unaligned(p, end - p) & ASCII_CHAR_MASK;
if (u) {