python · eendebakpt · Jan 3, 2023 · Jan 3, 2023 · Jan 3, 2023 · Jan 3, 2023
diff --git a/Include/internal/pycore_long.h b/Include/internal/pycore_long.h
@@ -129,6 +129,9 @@ _PyLong_IsPositiveSingleDigit(PyObject* sub) {
     return ((size_t)signed_size) <= 1;
 }
 
+long _PyLong_AsLongAndOverflow(const PyLongObject *v, int *overflow);
+
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-01-03-20-59-20.gh-issue-100726.W9huFl.rst b/Misc/NEWS.d/next/Core and Builtins/2023-01-03-20-59-20.gh-issue-100726.W9huFl.rst
@@ -0,0 +1 @@
+Optimize construction of ``range`` object for medium size integers.
diff --git a/Objects/longobject.c b/Objects/longobject.c
@@ -474,45 +474,21 @@ PyLong_FromDouble(double dval)
 #define PY_ABS_LONG_MIN         (0-(unsigned long)LONG_MIN)
 #define PY_ABS_SSIZE_T_MIN      (0-(size_t)PY_SSIZE_T_MIN)
 
-/* Get a C long int from an int object or any object that has an __index__
-   method.
+/* Get a C long int from a PyLong object
 
    On overflow, return -1 and set *overflow to 1 or -1 depending on the sign of
-   the result.  Otherwise *overflow is 0.
+   the result.  Otherwise *overflow is unchanged.
 
-   For other errors (e.g., TypeError), return -1 and set an error condition.
-   In this case *overflow will be 0.
+   Internal version, does not perform error checking
 */
-
-long
-PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
+inline long
+_PyLong_AsLongAndOverflow(const PyLongObject *v, int *overflow)
 {
-    /* This version by Tim Peters */
-    PyLongObject *v;
-    unsigned long x, prev;
-    long res;
-    Py_ssize_t i;
-    int sign;
-    int do_decref = 0; /* if PyNumber_Index was called */
-
-    *overflow = 0;
-    if (vv == NULL) {
-        PyErr_BadInternalCall();
-        return -1;
-    }
-
-    if (PyLong_Check(vv)) {
-        v = (PyLongObject *)vv;
-    }
-    else {
-        v = (PyLongObject *)_PyNumber_Index(vv);
-        if (v == NULL)
-            return -1;
-        do_decref = 1;
-    }
+    assert(v != NULL);
+    assert( PyLong_Check(v) );
 
-    res = -1;
-    i = Py_SIZE(v);
+    long res = -1;
+    Py_ssize_t i = Py_SIZE(v);
 
     switch (i) {
     case -1:
@@ -525,14 +501,15 @@ PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
         res = v->ob_digit[0];
         break;
     default:
-        sign = 1;
-        x = 0;
+    {
+        int sign = 1;
+        unsigned long x = 0;
         if (i < 0) {
             sign = -1;
             i = -(i);
         }
         while (--i >= 0) {
-            prev = x;
+            unsigned long prev = x;
             x = (x << PyLong_SHIFT) | v->ob_digit[i];
             if ((x >> PyLong_SHIFT) != prev) {
                 *overflow = sign;
@@ -553,7 +530,46 @@ PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
             /* res is already set to -1 */
         }
     }
+    }
   exit:
+    return res;
+}
+
+
+/* Get a C long int from an int object or any object that has an __index__
+   method.
+
+   On overflow, return -1 and set *overflow to 1 or -1 depending on the sign of
+   the result.  Otherwise *overflow is 0.
+
+   For other errors (e.g., TypeError), return -1 and set an error condition.
+   In this case *overflow will be 0.
+*/
+long
+PyLong_AsLongAndOverflow(PyObject *vv, int *overflow)
+{
+    /* This version by Tim Peters */
+    PyLongObject *v;
+    int do_decref = 0; /* if PyNumber_Index was called */
+    *overflow = 0;
+
+    if (vv == NULL) {
+        PyErr_BadInternalCall();
+        return -1;
+    }
+
+    if (PyLong_Check(vv)) {
+        v = (PyLongObject *)vv;
+    }
+    else {
+        v = (PyLongObject *)_PyNumber_Index(vv);
+        if (v == NULL)
+            return -1;
+        do_decref = 1;
+    }
+
+    long res = _PyLong_AsLongAndOverflow(v, overflow);
+
     if (do_decref) {
         Py_DECREF(v);
     }

diff --git a/Objects/rangeobject.c b/Objects/rangeobject.c
@@ -171,6 +171,28 @@ range_dealloc(rangeobject *r)
     PyObject_Free(r);
 }
 
+static unsigned long
+get_len_of_range(long lo, long hi, long step);
+
+/// Return the length as a long, or -1 on error
+static inline long compute_range_length_long(PyLongObject *start, PyLongObject *stop, PyLongObject *step) {
+    int overflow = 0;
+
+    long long_start = _PyLong_AsLongAndOverflow(start, &overflow);
+    if (overflow) {
+            return -1;
+    }
+    long long_stop = _PyLong_AsLongAndOverflow(stop, &overflow);
+    if (overflow) {
+            return -1;
+    }
+    long long_step = _PyLong_AsLongAndOverflow(step, &overflow);
+    if (overflow) {
+            return -1;
+    }
+    return get_len_of_range(long_start, long_stop, long_step);
+}
+
 /* Return number of items in range (lo, hi, step) as a PyLong object,
  * when arguments are PyLong objects.  Arguments MUST return 1 with
  * PyLong_Check().  Return NULL when there is an error.
@@ -182,6 +204,12 @@ compute_range_length(PyObject *start, PyObject *stop, PyObject *step)
     Algorithm is equal to that of get_len_of_range(), but it operates
     on PyObjects (which are assumed to be PyLong objects).
     ---------------------------------------------------------------*/
+
+    // fast path when all arguments fit into a long integer
+    long len = compute_range_length_long((PyLongObject*)start, (PyLongObject*)stop, (PyLongObject*)step);
+    if (len>=0) {
+        return PyLong_FromLong(len);
+    }
     int cmp_result;
     PyObject *lo, *hi;
     PyObject *diff = NULL;
-Original file line number
+Diff line change
@@ Expand Up / @@ -129,6 +129,9 @@ _PyLong_IsPositiveSingleDigit(PyObject* sub) { @@
         return ((size_t)signed_size) <= 1;
     }
+    long _PyLong_AsLongAndOverflow(const PyLongObject *v, int *overflow);
     #ifdef __cplusplus
     }
     #endif
@@ Expand Down @@
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Optimize construction of ``range`` object for medium size integers.