Fix handling of LOAD_SPECIAL

Load special may leave `self` on TOS. Treat it conservatively and
assume it always does.

Author: mpage

Lib/test/test_dis.py

@@ -606,7 +606,7 @@ async def _asyncwith(c):
                 POP_TOP
         L1:     RESUME                   0
 
-%4d            LOAD_FAST_BORROW         0 (c)
+%4d            LOAD_FAST                0 (c)
                 COPY                     1
                 LOAD_SPECIAL             3 (__aexit__)
                 SWAP                     2

Lib/test/test_peepholer.py

@@ -2688,6 +2688,16 @@ def test_push_exc_info(self):
         ]
         self.check(insts, insts)
 
+    def test_load_special(self):
+        # LOAD_SPECIAL may leave self on the stack
+        insts = [
+            ("LOAD_FAST", 0, 1),
+            ("LOAD_SPECIAL", 0, 2),
+            ("STORE_FAST", 1, 3),
+        ]
+        self.check(insts, insts)
+
+
     def test_del_in_finally(self):
         # This loads `obj` onto the stack, executes `del obj`, then returns the
         # `obj` from the stack. See gh-133371 for more details.

Python/flowgraph.c

@@ -2948,6 +2948,7 @@ optimize_load_fast(cfg_builder *g)
                     break;
                 }
 
+                case LOAD_SPECIAL:
                 case PUSH_EXC_INFO: {
                     ref tos = ref_stack_pop(&refs);
                     PUSH_REF(i, NOT_LOCAL);