[Python-checkins] bpo-37587: optimize json.loads (GH-15134)
Inada Naoki
webhook-mailer at python.org
Thu Aug 8 04:57:14 EDT 2019
https://github.com/python/cpython/commit/2a570af12ac5e4ac5575a68f8739b31c24d01367
commit: 2a570af12ac5e4ac5575a68f8739b31c24d01367
branch: master
author: Inada Naoki <songofacandy at gmail.com>
committer: GitHub <noreply at github.com>
date: 2019-08-08T17:57:10+09:00
summary:
bpo-37587: optimize json.loads (GH-15134)
Use a tighter scope temporary variable to help register allocation.
1% speedup for large string.
Use PyDict_SetItemDefault() for memoizing keys.
At most 4% speedup when the cache hit ratio is low.
files:
M Modules/_json.c
diff --git a/Modules/_json.c b/Modules/_json.c
index 76da1d345e9d..112903ea577a 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -433,16 +433,21 @@ scanstring_unicode(PyObject *pystr, Py_ssize_t end, int strict, Py_ssize_t *next
}
while (1) {
/* Find the end of the string or the next escape */
- Py_UCS4 c = 0;
- for (next = end; next < len; next++) {
- c = PyUnicode_READ(kind, buf, next);
- if (c == '"' || c == '\\') {
- break;
- }
- else if (c <= 0x1f && strict) {
- raise_errmsg("Invalid control character at", pystr, next);
- goto bail;
+ Py_UCS4 c;
+ {
+ // Use tight scope variable to help register allocation.
+ Py_UCS4 d = 0;
+ for (next = end; next < len; next++) {
+ d = PyUnicode_READ(kind, buf, next);
+ if (d == '"' || d == '\\') {
+ break;
+ }
+ if (d <= 0x1f && strict) {
+ raise_errmsg("Invalid control character at", pystr, next);
+ goto bail;
+ }
}
+ c = d;
}
if (!(c == '"' || c == '\\')) {
raise_errmsg("Unterminated string starting at", pystr, begin);
@@ -749,19 +754,13 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
key = scanstring_unicode(pystr, idx + 1, s->strict, &next_idx);
if (key == NULL)
goto bail;
- memokey = PyDict_GetItemWithError(s->memo, key);
- if (memokey != NULL) {
- Py_INCREF(memokey);
- Py_DECREF(key);
- key = memokey;
- }
- else if (PyErr_Occurred()) {
+ memokey = PyDict_SetDefault(s->memo, key, key);
+ if (memokey == NULL) {
goto bail;
}
- else {
- if (PyDict_SetItem(s->memo, key, key) < 0)
- goto bail;
- }
+ Py_INCREF(memokey);
+ Py_DECREF(key);
+ key = memokey;
idx = next_idx;
/* skip whitespace between key and : delimiter, read :, skip whitespace */
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