Marco Paolini <markopaol...@gmail.com> added the comment:
I am also working on a different patch that uses the "pcmpestri" SSE4 processor
instruction, it looks like this for now.
While at it I realized there is (maybe) another potential speedup: avoiding the
ucs4lib_find_max_char we do for each chunk of the string ( that entails
scanning the string in memory one more time)... anyways that's another (much
longer) story, probably for another issue?
```
diff --git a/Modules/_json.c b/Modules/_json.c
index 38beb6f50d..25b1cf4a99 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -400,6 +400,38 @@ _build_rval_index_tuple(PyObject *rval, Py_ssize_t idx) {
Py_CLEAR(chunk); \
}
+
+inline unsigned int
+_fast_search(const void *needle, unsigned int needle_len, const void
*haystack, unsigned int haystack_len)
+{
+ unsigned int pos;
+ __asm__ __volatile__("movq (%1), %%xmm1;\n"
+ "mov %2, %%eax;\n"
+ "movq %3, %%r8;\n"
+ "mov %4, %%edx;\n"
+ ".intel_syntax noprefix;\n"
+ "loop: pcmpestri xmm1, [r8], 0;\n" /* 0 = equal any */
+ /* "pcmpestri %%mm1, (%%r8), $0;\n" /\* 0 = equal any
*\/ */
+ ".att_syntax prefix;\n"
+ "cmp $15, %%ecx;\n"
+ "jbe found;\n"
+ "sub $16, %%edx;\n"
+ "jnge notfound;\n"
+ "add $16, %%r8;\n"
+ "jmp loop;\n"
+ "notfound: movl %4, %%ecx;\n"
+ "jmp exit;\n"
+ "found: mov %4, %%eax;\n"
+ "sub %%edx, %%eax;\n"
+ "add %%eax, %%ecx;\n"
+ "exit: mov %%ecx, %0;\n"
+ :"=m"(pos)
+ :"r"(needle), "r"(needle_len), "r"(haystack),
"r"(haystack_len)
+ :"%eax", "%edx", "%ecx", "%r8", "%xmm1");
+ return pos;
+}
+
+
static PyObject *
scanstring_unicode(PyObject *pystr, Py_ssize_t end, int strict, Py_ssize_t
*next_end_ptr)
{
@@ -431,17 +463,26 @@ scanstring_unicode(PyObject *pystr, Py_ssize_t end, int
strict, Py_ssize_t *next
PyErr_SetString(PyExc_ValueError, "end is out of bounds");
goto bail;
}
+ char needle[2];
+ needle[0] = '"';
+ needle[1] = '\\';
while (1) {
/* Find the end of the string or the next escape */
Py_UCS4 c = 0;
- for (next = end; next < len; next++) {
+ if (kind == PyUnicode_1BYTE_KIND) {
+ next = _fast_search(needle, 2, buf+end, len-end) + end;
+ if (next < len)
c = PyUnicode_READ(kind, buf, next);
- if (c == '"' || c == '\\') {
- break;
- }
- else if (strict && c <= 0x1f) {
- raise_errmsg("Invalid control character at", pystr, next);
- goto bail;
+ } else {
+ for (next = end; next < len; next++) {
+ c = PyUnicode_READ(kind, buf, next);
+ if (c == '"' || c == '\\') {
+ break;
+ }
+ else if (strict && c <= 0x1f) {
+ raise_errmsg("Invalid control character at", pystr, next);
+ goto bail;
+ }
}
}
if (!(c == '"' || c == '\\')) {
```
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue37587>
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