replace inline function `is_small_int` with a macro version (GH-15710)

Misc/NEWS.d/next/Core and Builtins/2019-08-23-22-46-25.bpo-37812.vsWZwS.rst

 The ``CHECK_SMALL_INT`` macro used inside :file:`Object/longobject.c` has
-been replaced with an explicit ``return`` at each call site, conditioned on
-a ``static inline`` function ``is_small_int``.
+been replaced with an explicit ``return`` at each call site.

Objects/longobject.c

@@ -42,11 +42,7 @@ PyObject *_PyLong_One = NULL;
 */
 static PyLongObject small_ints[NSMALLNEGINTS + NSMALLPOSINTS];
 
-static inline int
-is_small_int(long long ival)
-{
-    return -NSMALLNEGINTS <= ival && ival < NSMALLPOSINTS;
-}
+#define IS_SMALL_INT(ival) (-NSMALLNEGINTS <= (ival) && (ival) < NSMALLPOSINTS)
 
 #ifdef COUNT_ALLOCS
 Py_ssize_t _Py_quick_int_allocs, _Py_quick_neg_int_allocs;
@@ -56,7 +52,7 @@ static PyObject *
 get_small_int(sdigit ival)
 {
     PyObject *v;
-    assert(is_small_int(ival));
+    assert(IS_SMALL_INT(ival));
     v = (PyObject *)&small_ints[ival + NSMALLNEGINTS];
     Py_INCREF(v);
 #ifdef COUNT_ALLOCS
@@ -73,7 +69,7 @@ maybe_small_long(PyLongObject *v)
 {
     if (v && Py_ABS(Py_SIZE(v)) <= 1) {
         sdigit ival = MEDIUM_VALUE(v);
-        if (is_small_int(ival)) {
+        if (IS_SMALL_INT(ival)) {
             Py_DECREF(v);
             return (PyLongObject *)get_small_int(ival);
         }
@@ -81,8 +77,8 @@ maybe_small_long(PyLongObject *v)
     return v;
 }
 #else
-#define is_small_int(ival) 0
-#define get_small_int(ival) (assert(0), NULL)
+#define IS_SMALL_INT(ival) 0
+#define get_small_int(ival) (Py_UNREACHABLE(), NULL)
 #define maybe_small_long(val) (val)
 #endif
 
@@ -297,7 +293,7 @@ _PyLong_Copy(PyLongObject *src)
         i = -(i);
     if (i < 2) {
         sdigit ival = MEDIUM_VALUE(src);
-        if (is_small_int(ival)) {
+        if (IS_SMALL_INT(ival)) {
             return get_small_int(ival);
         }
     }
@@ -321,7 +317,7 @@ PyLong_FromLong(long ival)
     int ndigits = 0;
     int sign;
 
-    if (is_small_int(ival)) {
+    if (IS_SMALL_INT(ival)) {
         return get_small_int((sdigit)ival);
     }
 
@@ -1154,7 +1150,7 @@ PyLong_FromLongLong(long long ival)
     int ndigits = 0;
     int negative = 0;
 
-    if (is_small_int(ival)) {
+    if (IS_SMALL_INT(ival)) {
         return get_small_int((sdigit)ival);
     }
 
@@ -1229,7 +1225,7 @@ PyLong_FromSsize_t(Py_ssize_t ival)
     int ndigits = 0;
     int negative = 0;
 
-    if (is_small_int(ival)) {
+    if (IS_SMALL_INT(ival)) {
         return get_small_int((sdigit)ival);
     }