block anything with free variables

Author: Fidget-Spinner

Lib/test/test_capi/test_opt.py

@@ -3115,7 +3115,7 @@ def testfunc(n):
         self.assertIn("_POP_TOP_NOP", uops)
 
     def test_strength_reduce_constant_load_fast(self):
-        # If we detect a _LOAD_FAST is actually loading an immortal constant,
+        # If we detect a _LOAD_FAST is actually loading a constant,
         # reduce that to a _LOAD_CONST_INLINE_BORROW which saves
         # the read from locals.
         def testfunc(n):

Python/optimizer_bytecodes.c

@@ -88,17 +88,23 @@ dummy_func(void) {
     op(_LOAD_FAST, (-- value)) {
         value = GETLOCAL(oparg);
         PyObject *const_val = sym_get_const(ctx, value);
-        if (const_val != NULL && _Py_IsImmortal(const_val)) {
-            // Note: non-immortal is not safe to replace
-            // to _LOAD_CONST_INLINE, as it might not be held in co_const.
+        PyCodeObject *co = get_current_code_object(ctx);
+        // We don't reason about free variables yet, so we need to forbid
+        // anything with those.
+        if (const_val != NULL && co->co_nfreevars == 0) {
+            // It's safe to always borrow here, for
+            // the same reason as _LOAD_CONST.
             REPLACE_OP(this_instr, _LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)const_val);
         }
     }
 
     op(_LOAD_FAST_BORROW, (-- value)) {
         value = PyJitRef_Borrow(GETLOCAL(oparg));
         PyObject *const_val = sym_get_const(ctx, value);
-        if (const_val != NULL) {
+        PyCodeObject *co = get_current_code_object(ctx);
+        // We don't reason about free variables yet, so we need to forbid
+        // anything with those.
+        if (const_val != NULL && co->co_nfreevars == 0) {
             // It's safe to always borrow here, because
             // _LOAD_FAST_BORROW guarantees it.
             REPLACE_OP(this_instr, _LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)const_val);