bpo-44511: Improve the bytecode for class and mapping patterns (GH-26922)

* Refactor mapping patterns and speed up class patterns.

* Simplify MATCH_KEYS and MATCH_CLASS.

* Add COPY opcode.

1 files changed, 24 insertions, 44 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index adc7b53624..a0f4c801e8 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -4143,25 +4143,30 @@ check_eval_breaker:
         }
 
         TARGET(MATCH_CLASS) {
-            // Pop TOS. On success, set TOS to True and TOS1 to a tuple of
-            // attributes. On failure, set TOS to False.
+            // Pop TOS and TOS1. Set TOS to a tuple of attributes on success, or
+            // None on failure.
             PyObject *names = POP();
-            PyObject *type = TOP();
-            PyObject *subject = SECOND();
+            PyObject *type = POP();
+            PyObject *subject = TOP();
             assert(PyTuple_CheckExact(names));
             PyObject *attrs = match_class(tstate, subject, type, oparg, names);
             Py_DECREF(names);
+            Py_DECREF(type);
             if (attrs) {
                 // Success!
                 assert(PyTuple_CheckExact(attrs));
-                Py_DECREF(subject);
-                SET_SECOND(attrs);
+                SET_TOP(attrs);
             }
             else if (_PyErr_Occurred(tstate)) {
+                // Error!
                 goto error;
             }
-            Py_DECREF(type);
-            SET_TOP(PyBool_FromLong(!!attrs));
+            else {
+                // Failure!
+                Py_INCREF(Py_None);
+                SET_TOP(Py_None);
+            }
+            Py_DECREF(subject);
             DISPATCH();
         }
 
@@ -4171,6 +4176,7 @@ check_eval_breaker:
             PyObject *res = match ? Py_True : Py_False;
             Py_INCREF(res);
             PUSH(res);
+            PREDICT(POP_JUMP_IF_FALSE);
             DISPATCH();
         }
 
@@ -4180,12 +4186,12 @@ check_eval_breaker:
             PyObject *res = match ? Py_True : Py_False;
             Py_INCREF(res);
             PUSH(res);
+            PREDICT(POP_JUMP_IF_FALSE);
             DISPATCH();
         }
 
         TARGET(MATCH_KEYS) {
-            // On successful match for all keys, PUSH(values) and PUSH(True).
-            // Otherwise, PUSH(None) and PUSH(False).
+            // On successful match, PUSH(values). Otherwise, PUSH(None).
             PyObject *keys = TOP();
             PyObject *subject = SECOND();
             PyObject *values_or_none = match_keys(tstate, subject, keys);
@@ -4193,40 +4199,6 @@ check_eval_breaker:
                 goto error;
             }
             PUSH(values_or_none);
-            if (Py_IsNone(values_or_none)) {
-                Py_INCREF(Py_False);
-                PUSH(Py_False);
-                DISPATCH();
-            }
-            assert(PyTuple_CheckExact(values_or_none));
-            Py_INCREF(Py_True);
-            PUSH(Py_True);
-            DISPATCH();
-        }
-
-        TARGET(COPY_DICT_WITHOUT_KEYS) {
-            // rest = dict(TOS1)
-            // for key in TOS:
-            //     del rest[key]
-            // SET_TOP(rest)
-            PyObject *keys = TOP();
-            PyObject *subject = SECOND();
-            PyObject *rest = PyDict_New();
-            if (rest == NULL || PyDict_Update(rest, subject)) {
-                Py_XDECREF(rest);
-                goto error;
-            }
-            // This may seem a bit inefficient, but keys is rarely big enough to
-            // actually impact runtime.
-            assert(PyTuple_CheckExact(keys));
-            for (Py_ssize_t i = 0; i < PyTuple_GET_SIZE(keys); i++) {
-                if (PyDict_DelItem(rest, PyTuple_GET_ITEM(keys, i))) {
-                    Py_DECREF(rest);
-                    goto error;
-                }
-            }
-            Py_DECREF(keys);
-            SET_TOP(rest);
             DISPATCH();
         }
 
@@ -5027,6 +4999,14 @@ check_eval_breaker:
             DISPATCH();
         }
 
+        TARGET(COPY) {
+            assert(oparg != 0);
+            PyObject *peek = PEEK(oparg);
+            Py_INCREF(peek);
+            PUSH(peek);
+            DISPATCH();
+        }
+
         TARGET(EXTENDED_ARG) {
             int oldoparg = oparg;
             NEXTOPARG();