https://github.com/python/cpython/commit/5dd775bed086909722ec7014a7c4f77a35f74a80
commit: 5dd775bed086909722ec7014a7c4f77a35f74a80
branch: main
author: Inada Naoki <[email protected]>
committer: encukou <[email protected]>
date: 2024-12-13T17:21:46+01:00
summary:
gh-126024: unicodeobject: optimize find_first_nonascii (GH-127790)
Remove 1 branch.
files:
M Objects/unicodeobject.c
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 33c4747bbef488..b7aeb06d32bcec 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5077,21 +5077,24 @@ load_unaligned(const unsigned char *p, size_t size)
static Py_ssize_t
find_first_nonascii(const unsigned char *start, const unsigned char *end)
{
+ // The search is done in `size_t` chunks.
+ // The start and end might not be aligned at `size_t` boundaries,
+ // so they're handled specially.
+
const unsigned char *p = start;
if (end - start >= SIZEOF_SIZE_T) {
- const unsigned char *p2 = _Py_ALIGN_UP(p, SIZEOF_SIZE_T);
+ // Avoid unaligned read.
#if PY_LITTLE_ENDIAN && HAVE_CTZ
- if (p < p2) {
- size_t u;
- memcpy(&u, p, sizeof(size_t));
- u &= ASCII_CHAR_MASK;
- if (u) {
- return (ctz(u) - 7) / 8;
- }
- p = p2;
+ size_t u;
+ memcpy(&u, p, sizeof(size_t));
+ u &= ASCII_CHAR_MASK;
+ if (u) {
+ return (ctz(u) - 7) / 8;
}
+ p = _Py_ALIGN_DOWN(p + SIZEOF_SIZE_T, SIZEOF_SIZE_T);
#else /* PY_LITTLE_ENDIAN && HAVE_CTZ */
+ const unsigned char *p2 = _Py_ALIGN_UP(p, SIZEOF_SIZE_T);
while (p < p2) {
if (*p & 0x80) {
return p - start;
@@ -5099,6 +5102,7 @@ find_first_nonascii(const unsigned char *start, const
unsigned char *end)
p++;
}
#endif
+
const unsigned char *e = end - SIZEOF_SIZE_T;
while (p <= e) {
size_t u = (*(const size_t *)p) & ASCII_CHAR_MASK;
@@ -5115,6 +5119,7 @@ find_first_nonascii(const unsigned char *start, const
unsigned char *end)
}
}
#if PY_LITTLE_ENDIAN && HAVE_CTZ
+ assert((end - p) < SIZEOF_SIZE_T);
// 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) {
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