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SF patch #980695: efficient string concatenation

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(Original patch by Armin Rigo).
This commit is contained in:
Raymond Hettinger 2004-08-06 18:43:09 +00:00
parent d09d9664e6
commit 52a21b8e65
3 changed files with 107 additions and 3 deletions
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93
Python/ceval.c
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@ -85,6 +85,8 @@ static int exec_statement(PyFrameObject *,
static void set_exc_info(PyThreadState *, PyObject *, PyObject *, PyObject *);
static void reset_exc_info(PyThreadState *);
static void format_exc_check_arg(PyObject *, char *, PyObject *);
static PyObject *string_concatenate(PyObject *, PyObject *,
PyFrameObject *, unsigned char *);
#define NAME_ERROR_MSG \
"name '%.200s' is not defined"
@ -550,6 +552,7 @@ PyEval_EvalFrame(PyFrameObject *f)
#define INSTR_OFFSET() (next_instr - first_instr)
#define NEXTOP() (*next_instr++)
#define NEXTARG() (next_instr += 2, (next_instr[-1]<<8) + next_instr[-2])
#define PEEKARG() ((next_instr[2]<<8) + next_instr[1])
#define JUMPTO(x) (next_instr = first_instr + (x))
#define JUMPBY(x) (next_instr += (x))
@ -580,8 +583,7 @@ PyEval_EvalFrame(PyFrameObject *f)
#endif
#define PREDICTED(op) PRED_##op: next_instr++
#define PREDICTED_WITH_ARG(op) PRED_##op: oparg = (next_instr[2]<<8) + \
next_instr[1]; next_instr += 3
#define PREDICTED_WITH_ARG(op) PRED_##op: oparg = PEEKARG(); next_instr += 3
/* Stack manipulation macros */
@ -1066,11 +1068,18 @@ PyEval_EvalFrame(PyFrameObject *f)
goto slow_add;
x = PyInt_FromLong(i);
}
else if (PyString_CheckExact(v) &&
PyString_CheckExact(w)) {
x = string_concatenate(v, w, f, next_instr);
/* string_concatenate consumed the ref to v */
goto skip_decref_vx;
}
else {
slow_add:
x = PyNumber_Add(v, w);
}
Py_DECREF(v);
skip_decref_vx:
Py_DECREF(w);
SET_TOP(x);
if (x != NULL) continue;
@ -1261,11 +1270,18 @@ PyEval_EvalFrame(PyFrameObject *f)
goto slow_iadd;
x = PyInt_FromLong(i);
}
else if (PyString_CheckExact(v) &&
PyString_CheckExact(w)) {
x = string_concatenate(v, w, f, next_instr);
/* string_concatenate consumed the ref to v */
goto skip_decref_v;
}
else {
slow_iadd:
x = PyNumber_InPlaceAdd(v, w);
}
Py_DECREF(v);
skip_decref_v:
Py_DECREF(w);
SET_TOP(x);
if (x != NULL) continue;
@ -4191,6 +4207,79 @@ format_exc_check_arg(PyObject *exc, char *format_str, PyObject *obj)
PyErr_Format(exc, format_str, obj_str);
}
static PyObject *
string_concatenate(PyObject *v, PyObject *w,
PyFrameObject *f, unsigned char *next_instr)
{
/* This function implements 'variable += expr' when both arguments
are strings. */
if (v->ob_refcnt == 2) {
/* In the common case, there are 2 references to the value
* stored in 'variable' when the += is performed: one on the
* value stack (in 'v') and one still stored in the 'variable'.
* We try to delete the variable now to reduce the refcnt to 1.
*/
switch (*next_instr) {
case STORE_FAST:
{
int oparg = PEEKARG();
PyObject **fastlocals = f->f_localsplus;
if (GETLOCAL(oparg) == v)
SETLOCAL(oparg, NULL);
break;
}
case STORE_DEREF:
{
PyObject **freevars = f->f_localsplus + f->f_nlocals;
PyObject *c = freevars[PEEKARG()];
if (PyCell_GET(c) == v)
PyCell_Set(c, NULL);
break;
}
case STORE_NAME:
{
PyObject *names = f->f_code->co_names;
PyObject *name = GETITEM(names, PEEKARG());
PyObject *locals = f->f_locals;
if (PyDict_CheckExact(locals) &&
PyDict_GetItem(locals, name) == v) {
if (PyDict_DelItem(locals, name) != 0) {
PyErr_Clear();
}
}
break;
}
}
}
if (v->ob_refcnt == 1) {
/* Now we own the last reference to 'v', so we can resize it
* in-place.
*/
int v_len = PyString_GET_SIZE(v);
int w_len = PyString_GET_SIZE(w);
if (_PyString_Resize(&v, v_len + w_len) != 0) {
/* XXX if _PyString_Resize() fails, 'v' has been
* deallocated so it cannot be put back into 'variable'.
* The MemoryError is raised when there is no value in
* 'variable', which might (very remotely) be a cause
* of incompatibilities.
*/
return NULL;
}
/* copy 'w' into the newly allocated area of 'v' */
memcpy(PyString_AS_STRING(v) + v_len,
PyString_AS_STRING(w), w_len);
return v;
}
else {
/* When in-place resizing is not an option. */
PyString_Concat(&v, w);
return v;
}
}
#ifdef DYNAMIC_EXECUTION_PROFILE
static PyObject *