Don't declare unused variables and update test

Author: markshannon

Lib/test/test_generated_cases.py

@@ -68,13 +68,15 @@ def test_effect_sizes(self):
             StackItem("b", None, "oparg*4"),
             StackItem("c", None, "1"),
         ]
-        stack.pop(z)
-        stack.pop(y)
-        stack.pop(x)
+        null = CWriter.null()
+        stack.pop(z, null)
+        stack.pop(y, null)
+        stack.pop(x, null)
         for out in outputs:
             stack.push(Local.undefined(out))
         self.assertEqual(stack.base_offset.to_c(), "-1 - oparg - oparg*2")
-        self.assertEqual(stack.top_offset.to_c(), "1 - oparg - oparg*2 + oparg*4")
+        self.assertEqual(stack.physical_sp.to_c(), "0")
+        self.assertEqual(stack.logical_sp.to_c(), "1 - oparg - oparg*2 + oparg*4")
 
 
 class TestGeneratedCases(unittest.TestCase):

Python/generated_cases.c.h

@@ -53,11 +53,11 @@ def declare_variables(inst: Instruction, out: CWriter) -> None:
         if not isinstance(part, Uop):
             continue
         for var in part.stack.inputs:
-            if var.name not in seen:
+            if var.used and var.name not in seen:
                 seen.add(var.name)
                 declare_variable(var, out)
         for var in part.stack.outputs:
-            if var.name not in seen:
+            if var.used and var.name not in seen:
                 seen.add(var.name)
                 declare_variable(var, out)