Avoid an abs()

Author: stefanor

Lib/test/test_call.py

@@ -1050,10 +1050,12 @@ def get_sp():
         lower_sp = _testcapi.pyobject_vectorcall(get_sp, (), ())
         if _testcapi._Py_STACK_GROWS_DOWN:
             self.assertLess(lower_sp, this_sp)
+            safe_margin = this_sp - lower_sp
         else:
             self.assertGreater(lower_sp, this_sp)
+            safe_margin = lower_sp - this_sp
         # Add an (arbitrary) extra 25% for safety
-        safe_margin = abs(this_sp - lower_sp) * 5 / 4
+        safe_margin = safe_margin * 5 / 4
         self.assertLess(safe_margin, _testinternalcapi.get_stack_margin())
 
     @skip_on_s390x