move extensive node building code for range step calculation into a separate method

Cython/Compiler/Optimize.py

@@ -743,13 +743,44 @@ class IterationTransform(Visitor.EnvTransform):
                 else:
                     # evaluate the same expression as above at runtime
                     bound2_ref_node = UtilNodes.LetRefNode(bound2)
-                    spanning_type = PyrexTypes.spanning_type(bound1.type, bound2.type)
+                    bound1 = self._build_range_step_calculation(
+                        bound1, bound2_ref_node, step, step_value)
+
+        if step_value < 0:
+            step_value = -step_value
+        step.value = str(step_value)
+        step.constant_result = step_value
+        step = step.coerce_to_integer(self.current_env())
+
+        if not bound2.is_literal:
+            # stop bound must be immutable => keep it in a temp var
+            bound2_is_temp = True
+            bound2 = bound2_ref_node or UtilNodes.LetRefNode(bound2)
+        else:
+            bound2_is_temp = False
+
+        for_node = Nodes.ForFromStatNode(
+            node.pos,
+            target=node.target,
+            bound1=bound1, relation1=relation1,
+            relation2=relation2, bound2=bound2,
+            step=step, body=node.body,
+            else_clause=node.else_clause,
+            from_range=True)
+
+        if bound2_is_temp:
+            for_node = UtilNodes.LetNode(bound2, for_node)
+
+        return for_node
+
+    def _build_range_step_calculation(self, bound1, bound2_ref_node, step, step_value):
+        abs_step = abs(step_value)
+        spanning_type = PyrexTypes.spanning_type(bound1.type, bound2_ref_node.type)
         if step.type.is_int and abs_step < 0x7FFF:
             # Avoid loss of integer precision warnings.
             spanning_step_type = PyrexTypes.spanning_type(spanning_type, PyrexTypes.c_int_type)
         else:
             spanning_step_type = PyrexTypes.spanning_type(spanning_type, step.type)
-
         if step_value < 0:
             begin_value = bound2_ref_node
             end_value = bound1
@@ -759,7 +790,7 @@ class IterationTransform(Visitor.EnvTransform):
             end_value = bound2_ref_node
             final_op = '+'
 
-                    bound1 = ExprNodes.binop_node(
+        step_calculation_node = ExprNodes.binop_node(
             bound1.pos,
             operand1=ExprNodes.binop_node(
                 bound1.pos,
@@ -804,33 +835,7 @@ class IterationTransform(Visitor.EnvTransform):
                 value='1',
                 constant_result=1),
             type=spanning_type)
-
-        if step_value < 0:
-            step_value = -step_value
-        step.value = str(step_value)
-        step.constant_result = step_value
-        step = step.coerce_to_integer(self.current_env())
-
-        if not bound2.is_literal:
-            # stop bound must be immutable => keep it in a temp var
-            bound2_is_temp = True
-            bound2 = bound2_ref_node or UtilNodes.LetRefNode(bound2)
-        else:
-            bound2_is_temp = False
-
-        for_node = Nodes.ForFromStatNode(
-            node.pos,
-            target=node.target,
-            bound1=bound1, relation1=relation1,
-            relation2=relation2, bound2=bound2,
-            step=step, body=node.body,
-            else_clause=node.else_clause,
-            from_range=True)
-
-        if bound2_is_temp:
-            for_node = UtilNodes.LetNode(bound2, for_node)
-
-        return for_node
+        return step_calculation_node
 
     def _transform_dict_iteration(self, node, dict_obj, method, keys, values):
         temps = []