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bpo-38252: Use 8-byte step to detect ASCII sequence in 64bit Windows build (GH-16334)

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Ma Lin 2020-10-18 22:48:38 +08:00 • committed by GitHub
parent 3635388f52
commit a0c603cb9d
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5 changed files with 53 additions and 52 deletions
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30
Objects/stringlib/codecs.h
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@ -6,14 +6,14 @@
#include "pycore_bitutils.h" // _Py_bswap32()
/* Mask to quickly check whether a C 'long' contains a
/* Mask to quickly check whether a C 'size_t' contains a
non-ASCII, UTF8-encoded char. */
#if (SIZEOF_LONG == 8)
# define ASCII_CHAR_MASK 0x8080808080808080UL
#elif (SIZEOF_LONG == 4)
# define ASCII_CHAR_MASK 0x80808080UL
#if (SIZEOF_SIZE_T == 8)
# define ASCII_CHAR_MASK 0x8080808080808080ULL
#elif (SIZEOF_SIZE_T == 4)
# define ASCII_CHAR_MASK 0x80808080U
#else
# error C 'long' size should be either 4 or 8!
# error C 'size_t' size should be either 4 or 8!
#endif
/* 10xxxxxx */
@ -26,7 +26,7 @@ STRINGLIB(utf8_decode)(const char **inptr, const char *end,
{
Py_UCS4 ch;
const char *s = *inptr;
const char *aligned_end = (const char *) _Py_ALIGN_DOWN(end, SIZEOF_LONG);
const char *aligned_end = (const char *) _Py_ALIGN_DOWN(end, SIZEOF_SIZE_T);
STRINGLIB_CHAR *p = dest + *outpos;
while (s < end) {
@ -36,19 +36,19 @@ STRINGLIB(utf8_decode)(const char **inptr, const char *end,
/* Fast path for runs of ASCII characters. Given that common UTF-8
input will consist of an overwhelming majority of ASCII
characters, we try to optimize for this case by checking
as many characters as a C 'long' can contain.
as many characters as a C 'size_t' can contain.
First, check if we can do an aligned read, as most CPUs have
a penalty for unaligned reads.
*/
if (_Py_IS_ALIGNED(s, SIZEOF_LONG)) {
if (_Py_IS_ALIGNED(s, SIZEOF_SIZE_T)) {
/* Help register allocation */
const char *_s = s;
STRINGLIB_CHAR *_p = p;
while (_s < aligned_end) {
/* Read a whole long at a time (either 4 or 8 bytes),
/* Read a whole size_t at a time (either 4 or 8 bytes),
and do a fast unrolled copy if it only contains ASCII
characters. */
unsigned long value = *(const unsigned long *) _s;
size_t value = *(const size_t *) _s;
if (value & ASCII_CHAR_MASK)
break;
#if PY_LITTLE_ENDIAN
@ -56,14 +56,14 @@ STRINGLIB(utf8_decode)(const char **inptr, const char *end,
_p[1] = (STRINGLIB_CHAR)((value >> 8) & 0xFFu);
_p[2] = (STRINGLIB_CHAR)((value >> 16) & 0xFFu);
_p[3] = (STRINGLIB_CHAR)((value >> 24) & 0xFFu);
# if SIZEOF_LONG == 8
# if SIZEOF_SIZE_T == 8
_p[4] = (STRINGLIB_CHAR)((value >> 32) & 0xFFu);
_p[5] = (STRINGLIB_CHAR)((value >> 40) & 0xFFu);
_p[6] = (STRINGLIB_CHAR)((value >> 48) & 0xFFu);
_p[7] = (STRINGLIB_CHAR)((value >> 56) & 0xFFu);
# endif
#else
# if SIZEOF_LONG == 8
# if SIZEOF_SIZE_T == 8
_p[0] = (STRINGLIB_CHAR)((value >> 56) & 0xFFu);
_p[1] = (STRINGLIB_CHAR)((value >> 48) & 0xFFu);
_p[2] = (STRINGLIB_CHAR)((value >> 40) & 0xFFu);
@ -79,8 +79,8 @@ STRINGLIB(utf8_decode)(const char **inptr, const char *end,
_p[3] = (STRINGLIB_CHAR)(value & 0xFFu);
# endif
#endif
_s += SIZEOF_LONG;
_p += SIZEOF_LONG;
_s += SIZEOF_SIZE_T;
_p += SIZEOF_SIZE_T;
}
s = _s;
p = _p;