reduced overhead for CPython in __Pyx_IterFinish() utility function

--HG--
extra : transplant_source : %E3%97%5E9%1A%97%9BR%EC%01%FD%A0%B7-%81%C5G%AD%DA%DC

Cython/Utility/ObjectHandling.c

@@ -165,6 +165,27 @@ static CYTHON_INLINE int __Pyx_IterFinish(); /*proto*/
 // detects an error that occurred in the iterator, it returns -1.
 
 static CYTHON_INLINE int __Pyx_IterFinish() {
+#if CYTHON_COMPILING_IN_CPYTHON
+    PyThreadState *tstate = PyThreadState_GET();
+    PyObject* exc_type = tstate->curexc_type;
+    if (unlikely(exc_type)) {
+        if (likely(exc_type == PyExc_StopIteration) || PyErr_GivenExceptionMatches(exc_type, PyExc_StopIteration)) {
+            PyObject *exc_value, *exc_tb;
+            exc_value = tstate->curexc_value;
+            exc_tb = tstate->curexc_traceback;
+            tstate->curexc_type = 0;
+            tstate->curexc_value = 0;
+            tstate->curexc_traceback = 0;
+            Py_DECREF(exc_type);
+            Py_XDECREF(exc_value);
+            Py_XDECREF(exc_tb);
+            return 0;
+        } else {
+            return -1;
+        }
+    }
+    return 0;
+#else
     if (unlikely(PyErr_Occurred())) {
         if (likely(PyErr_ExceptionMatches(PyExc_StopIteration))) {
             PyErr_Clear();
@@ -174,4 +195,5 @@ static CYTHON_INLINE int __Pyx_IterFinish() {
         }
     }
     return 0;
+#endif
 }