python
diff --git a/‎Objects/longobject.c
Lines changed: 27 additions & 16 deletions b/‎Objects/longobject.c
Lines changed: 27 additions & 16 deletions
@@ -262,6 +262,24 @@ _PyLong_FromMedium(sdigit x)
     return (PyObject*)v;
 }
 
+static twodigits THREE_DIGIT_CUTOFF = (twodigits)1 << PyLong_SHIFT << PyLong_SHIFT;  // two shifts to avoud undefined behavior
+
+static inline Py_ssize_t _fast_digit_count_ssize_t(Py_ssize_t abs_ival)
+{
+    assert(abs_ival >> PyLong_SHIFT != 0);
+    Py_ssize_t ndigits = abs_ival <= THREE_DIGIT_CUTOFF ? 2 : 3;
+    return ndigits;
+}
+
+
+
+static inline Py_ssize_t _fast_digit_count(twodigits abs_ival)
+{
+    assert(abs_ival >> PyLong_SHIFT != 0);
+    Py_ssize_t ndigits = abs_ival <= THREE_DIGIT_CUTOFF ? 2 : 3;
+    return ndigits;
+}
+
 static PyObject *
 _PyLong_FromLarge(stwodigits ival)
 {
@@ -279,6 +297,11 @@ _PyLong_FromLarge(stwodigits ival)
         abs_ival = (twodigits)ival;
         sign = 1;
     }
+#if PYLONG_BITS_IN_DIGIT == 31
+    /* Must be at least two digits, at most 3 */
+    twodigits t;
+    Py_ssize_t ndigits = _fast_digit_count(abs_ival);
+#else
     /* Must be at least two digits */
     assert(abs_ival >> PyLong_SHIFT != 0);
     twodigits t = abs_ival >> (PyLong_SHIFT * 2);
@@ -287,6 +310,7 @@ _PyLong_FromLarge(stwodigits ival)
         ++ndigits;
         t >>= PyLong_SHIFT;
     }
+#endif
     PyLongObject *v = long_alloc(ndigits);
     if (v != NULL) {
         digit *p = v->long_value.ob_digit;
@@ -353,11 +377,7 @@ PyLong_FromLong(long ival)
     abs_ival = ival < 0 ? 0U-(unsigned long)ival : (unsigned long)ival;
     /* Do shift in two steps to avoid possible undefined behavior. */
     t = abs_ival >> PyLong_SHIFT >> PyLong_SHIFT;
-    ndigits = 2;
-    while (t) {
-        ++ndigits;
-        t >>= PyLong_SHIFT;
-    }
+    ndigits = _fast_digit_count_ssize_t(abs_ival);
 
     /* Construct output value. */
     v = long_alloc(ndigits);
@@ -384,11 +404,7 @@ PyLong_FromLong(long ival)
         /* Do shift in two steps to avoid possible undefined behavior. */ \
         INT_TYPE t = (ival) >> PyLong_SHIFT >> PyLong_SHIFT; \
         /* Count the number of Python digits. */ \
-        Py_ssize_t ndigits = 2; \
-        while (t) { \
-            ++ndigits; \
-            t >>= PyLong_SHIFT; \
-        } \
+        Py_ssize_t ndigits = _fast_digit_count_ssize_t(ival); \
         PyLongObject *v = long_alloc(ndigits); \
         if (v == NULL) { \
             return NULL; \
@@ -1526,7 +1542,6 @@ PyLong_FromSsize_t(Py_ssize_t ival)
     PyLongObject *v;
     size_t abs_ival;
     size_t t;  /* unsigned so >> doesn't propagate sign bit */
-    int ndigits = 0;
     int negative = 0;
 
     if (IS_SMALL_INT(ival)) {
@@ -1543,11 +1558,7 @@ PyLong_FromSsize_t(Py_ssize_t ival)
     }
 
     /* Count the number of Python digits. */
-    t = abs_ival;
-    while (t) {
-        ++ndigits;
-        t >>= PyLong_SHIFT;
-    }
+    Py_ssize_t ndigits = _fast_digit_count_ssize_t(abs_ival);
     v = long_alloc(ndigits);
     if (v != NULL) {
         digit *p = v->long_value.ob_digit;