Inline fast special cases for "abs(PyLong)" when the argument is non-negative or small.

CHANGES.rst

@@ -5,6 +5,11 @@ Cython Changelog
 0.28.2 (2018-??-??)
 ===================
 
+Features added
+--------------
+
+* ``abs()`` is faster for Python long objects.
+
 Bugs fixed
 ----------
 

Cython/Compiler/Builtin.py

@@ -124,7 +124,8 @@ builtin_function_table = [
                                   PyrexTypes.c_double_complex_type,
                                   PyrexTypes.c_longdouble_complex_type)
                         ) + [
-    BuiltinFunction('abs',        "O",    "O",     "PyNumber_Absolute"),
+    BuiltinFunction('abs',        "O",    "O",     "__Pyx_PyNumber_Absolute",
+                    utility_code=UtilityCode.load("py_abs", "Builtins.c")),
     #('all',       "",     "",      ""),
     #('any',       "",     "",      ""),
     #('ascii',     "",     "",      ""),

Cython/Utility/Builtins.c

@@ -253,6 +253,33 @@ static CYTHON_INLINE PY_LONG_LONG __Pyx_abs_longlong(PY_LONG_LONG x) {
 }
 
 
+//////////////////// py_abs.proto ////////////////////
+
+#if CYTHON_USE_PYLONG_INTERNALS
+static PyObject *__Pyx_PyLong_AbsNeg(PyObject *num);/*proto*/
+
+#define __Pyx_PyNumber_Absolute(x) \
+    ((likely(PyLong_CheckExact(x))) ? \
+         (likely(Py_SIZE(x) >= 0) ? (Py_INCREF(x), (x)) : __Pyx_PyLong_AbsNeg(x)) : \
+         PyNumber_Absolute(x))
+
+#else
+#define __Pyx_PyNumber_Absolute(x)  PyNumber_Absolute(x)
+#endif
+
+//////////////////// py_abs ////////////////////
+
+#if CYTHON_USE_PYLONG_INTERNALS
+static PyObject *__Pyx_PyLong_AbsNeg(PyObject *n) {
+    if (likely(Py_SIZE(n) == -1)) {
+        // digits are unsigned
+        return PyLong_FromLong(((PyLongObject*)n)->ob_digit[0]);
+    }
+    return ((PyTypeObject*)Py_TYPE(n))->tp_as_number->nb_negative(n);
+}
+#endif
+
+
 //////////////////// pow2.proto ////////////////////
 
 #define __Pyx_PyNumber_Power2(a, b) PyNumber_Power(a, b, Py_None)