gh-98831: Support conditional effects; use for LOAD_ATTR (#101333)

1 files changed, 13 insertions, 25 deletions

diff --git a/Python/bytecodes.c b/Python/bytecodes.c
index e5769f61..fb00b88 100644
--- a/Python/bytecodes.c
+++ b/Python/bytecodes.c
@@ -51,7 +51,7 @@
 
 // Dummy variables for stack effects.
 static PyObject *value, *value1, *value2, *left, *right, *res, *sum, *prod, *sub;
-static PyObject *container, *start, *stop, *v, *lhs, *rhs;
+static PyObject *container, *start, *stop, *v, *lhs, *rhs, *res2;
 static PyObject *list, *tuple, *dict, *owner, *set, *str, *tup, *map, *keys;
 static PyObject *exit_func, *lasti, *val, *retval, *obj, *iter;
 static PyObject *aiter, *awaitable, *iterable, *w, *exc_value, *bc;
@@ -1438,13 +1438,11 @@ dummy_func(
             PREDICT(JUMP_BACKWARD);
         }
 
-        // error: LOAD_ATTR has irregular stack effect
-        inst(LOAD_ATTR) {
+        inst(LOAD_ATTR, (unused/9, owner -- res2 if (oparg & 1), res)) {
             #if ENABLE_SPECIALIZATION
             _PyAttrCache *cache = (_PyAttrCache *)next_instr;
             if (ADAPTIVE_COUNTER_IS_ZERO(cache->counter)) {
                 assert(cframe.use_tracing == 0);
-                PyObject *owner = TOP();
                 PyObject *name = GETITEM(names, oparg>>1);
                 next_instr--;
                 _Py_Specialize_LoadAttr(owner, next_instr, name);
@@ -1454,26 +1452,18 @@ dummy_func(
             DECREMENT_ADAPTIVE_COUNTER(cache->counter);
             #endif  /* ENABLE_SPECIALIZATION */
             PyObject *name = GETITEM(names, oparg >> 1);
-            PyObject *owner = TOP();
             if (oparg & 1) {
-                /* Designed to work in tandem with CALL. */
+                /* Designed to work in tandem with CALL, pushes two values. */
                 PyObject* meth = NULL;
-
-                int meth_found = _PyObject_GetMethod(owner, name, &meth);
-
-                if (meth == NULL) {
-                    /* Most likely attribute wasn't found. */
-                    goto error;
-                }
-
-                if (meth_found) {
+                if (_PyObject_GetMethod(owner, name, &meth)) {
                     /* We can bypass temporary bound method object.
                        meth is unbound method and obj is self.
 
                        meth | self | arg1 | ... | argN
                      */
-                    SET_TOP(meth);
-                    PUSH(owner);  // self
+                    assert(meth != NULL);  // No errors on this branch
+                    res2 = meth;
+                    res = owner;  // Transfer ownership
                 }
                 else {
                     /* meth is not an unbound method (but a regular attr, or
@@ -1483,20 +1473,18 @@ dummy_func(
 
                        NULL | meth | arg1 | ... | argN
                     */
-                    SET_TOP(NULL);
                     Py_DECREF(owner);
-                    PUSH(meth);
+                    ERROR_IF(meth == NULL, error);
+                    res2 = NULL;
+                    res = meth;
                 }
             }
             else {
-                PyObject *res = PyObject_GetAttr(owner, name);
-                if (res == NULL) {
-                    goto error;
-                }
+                /* Classic, pushes one value. */
+                res = PyObject_GetAttr(owner, name);
                 Py_DECREF(owner);
-                SET_TOP(res);
+                ERROR_IF(res == NULL, error);
             }
-            JUMPBY(INLINE_CACHE_ENTRIES_LOAD_ATTR);
         }
 
         // error: LOAD_ATTR has irregular stack effect