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Close #14249: Use an union instead of a long to short pointer to avoid aliasing 

issue. Speed up UTF-16 by 20%.
This commit is contained in:
Victor Stinner 2012-04-05 13:44:34 +02:00
parent 20bbf54f5e
commit e7eee01f36
1 changed files with 25 additions and 19 deletions
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44
Objects/unicodeobject.c
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@ -5496,33 +5496,39 @@ PyUnicode_DecodeUTF16Stateful(const char *s,
int kind = PyUnicode_KIND(unicode);
void *data = PyUnicode_DATA(unicode);
while (_q < aligned_end) {
unsigned long block = * (unsigned long *) _q;
unsigned short *pblock = (unsigned short*)&block;
union {
unsigned long as_long;
unsigned short units[sizeof(long) / sizeof(short)];
unsigned char bytes[sizeof(long)];
} block, block_copy;
Py_UCS4 maxch;
block.as_long = *(unsigned long *) _q;
if (native_ordering) {
/* Can use buffer directly */
if (block & FAST_CHAR_MASK)
if (block.as_long & FAST_CHAR_MASK)
break;
}
else {
/* Need to byte-swap */
unsigned char *_p = (unsigned char*)pblock;
if (block & SWAPPED_FAST_CHAR_MASK)
block_copy = block;
if (block.as_long & SWAPPED_FAST_CHAR_MASK)
break;
_p[0] = _q[1];
_p[1] = _q[0];
_p[2] = _q[3];
_p[3] = _q[2];
block.bytes[0] = block_copy.bytes[1];
block.bytes[1] = block_copy.bytes[0];
block.bytes[2] = block_copy.bytes[3];
block.bytes[3] = block_copy.bytes[2];
#if (SIZEOF_LONG == 8)
_p[4] = _q[5];
_p[5] = _q[4];
_p[6] = _q[7];
_p[7] = _q[6];
block.bytes[4] = block_copy.bytes[5];
block.bytes[5] = block_copy.bytes[4];
block.bytes[6] = block_copy.bytes[7];
block.bytes[7] = block_copy.bytes[6];
#endif
}
maxch = Py_MAX(pblock[0], pblock[1]);
maxch = Py_MAX(block.units[0], block.units[1]);
#if SIZEOF_LONG == 8
maxch = Py_MAX(maxch, Py_MAX(pblock[2], pblock[3]));
maxch = Py_MAX(maxch, Py_MAX(block.units[2], block.units[3]));
#endif
if (maxch > PyUnicode_MAX_CHAR_VALUE(unicode)) {
if (unicode_widen(&unicode, maxch) < 0)
@ -5530,11 +5536,11 @@ PyUnicode_DecodeUTF16Stateful(const char *s,
kind = PyUnicode_KIND(unicode);
data = PyUnicode_DATA(unicode);
}
PyUnicode_WRITE(kind, data, outpos++, pblock[0]);
PyUnicode_WRITE(kind, data, outpos++, pblock[1]);
PyUnicode_WRITE(kind, data, outpos++, block.units[0]);
PyUnicode_WRITE(kind, data, outpos++, block.units[1]);
#if SIZEOF_LONG == 8
PyUnicode_WRITE(kind, data, outpos++, pblock[2]);
PyUnicode_WRITE(kind, data, outpos++, pblock[3]);
PyUnicode_WRITE(kind, data, outpos++, block.units[2]);
PyUnicode_WRITE(kind, data, outpos++, block.units[3]);
#endif
_q += SIZEOF_LONG;
}