GH-93911: Specialize LOAD_ATTR for custom __getattribute__ (GH-93988)

Author: Fidget-Spinner

Include/internal/pycore_code.h

@@ -118,6 +118,7 @@ struct callable_cache {
     PyObject *isinstance;
     PyObject *len;
     PyObject *list_append;
+    PyObject *object__getattribute__;
 };
 
 /* "Locals plus" for a code object is the set of locals + cell vars +

Include/internal/pycore_opcode.h

@@ -75,6 +75,9 @@ extern void _PyStaticType_ClearWeakRefs(PyTypeObject *type);
 extern void _PyStaticType_Dealloc(PyTypeObject *type);
 
 
+PyObject *_Py_slot_tp_getattro(PyObject *self, PyObject *name);
+PyObject *_Py_slot_tp_getattr_hook(PyObject *self, PyObject *name);
+
 #ifdef __cplusplus
 }
 #endif

Include/internal/pycore_typeobject.h

@@ -338,6 +338,7 @@ def pseudo_op(name, op, real_ops):
         "LOAD_ATTR_ADAPTIVE",
         # These potentially push [NULL, bound method] onto the stack.
         "LOAD_ATTR_CLASS",
+        "LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN",
         "LOAD_ATTR_INSTANCE_VALUE",
         "LOAD_ATTR_MODULE",
         "LOAD_ATTR_PROPERTY",

Include/opcode.h

@@ -0,0 +1 @@
+Specialize ``LOAD_ATTR`` for objects with custom ``__getattr__`` and ``__getattribute__``.

Lib/opcode.py

@@ -8102,17 +8102,17 @@ slot_tp_call(PyObject *self, PyObject *args, PyObject *kwds)
 
 /* There are two slot dispatch functions for tp_getattro.
 
-   - slot_tp_getattro() is used when __getattribute__ is overridden
+   - _Py_slot_tp_getattro() is used when __getattribute__ is overridden
      but no __getattr__ hook is present;
 
-   - slot_tp_getattr_hook() is used when a __getattr__ hook is present.
+   - _Py_slot_tp_getattr_hook() is used when a __getattr__ hook is present.
 
-   The code in update_one_slot() always installs slot_tp_getattr_hook(); this
-   detects the absence of __getattr__ and then installs the simpler slot if
-   necessary. */
+   The code in update_one_slot() always installs _Py_slot_tp_getattr_hook();
+   this detects the absence of __getattr__ and then installs the simpler
+   slot if necessary. */
 
-static PyObject *
-slot_tp_getattro(PyObject *self, PyObject *name)
+PyObject *
+_Py_slot_tp_getattro(PyObject *self, PyObject *name)
 {
     PyObject *stack[2] = {self, name};
     return vectorcall_method(&_Py_ID(__getattribute__), stack, 2);
@@ -8143,8 +8143,8 @@ call_attribute(PyObject *self, PyObject *attr, PyObject *name)
     return res;
 }
 
-static PyObject *
-slot_tp_getattr_hook(PyObject *self, PyObject *name)
+PyObject *
+_Py_slot_tp_getattr_hook(PyObject *self, PyObject *name)
 {
     PyTypeObject *tp = Py_TYPE(self);
     PyObject *getattr, *getattribute, *res;
@@ -8157,8 +8157,8 @@ slot_tp_getattr_hook(PyObject *self, PyObject *name)
     getattr = _PyType_Lookup(tp, &_Py_ID(__getattr__));
     if (getattr == NULL) {
         /* No __getattr__ hook: use a simpler dispatcher */
-        tp->tp_getattro = slot_tp_getattro;
-        return slot_tp_getattro(self, name);
+        tp->tp_getattro = _Py_slot_tp_getattro;
+        return _Py_slot_tp_getattro(self, name);
     }
     Py_INCREF(getattr);
     /* speed hack: we could use lookup_maybe, but that would resolve the
@@ -8519,10 +8519,10 @@ static slotdef slotdefs[] = {
            PyWrapperFlag_KEYWORDS),
     TPSLOT("__str__", tp_str, slot_tp_str, wrap_unaryfunc,
            "__str__($self, /)\n--\n\nReturn str(self)."),
-    TPSLOT("__getattribute__", tp_getattro, slot_tp_getattr_hook,
+    TPSLOT("__getattribute__", tp_getattro, _Py_slot_tp_getattr_hook,
            wrap_binaryfunc,
            "__getattribute__($self, name, /)\n--\n\nReturn getattr(self, name)."),
-    TPSLOT("__getattr__", tp_getattro, slot_tp_getattr_hook, NULL, ""),
+    TPSLOT("__getattr__", tp_getattro, _Py_slot_tp_getattr_hook, NULL, ""),
     TPSLOT("__setattr__", tp_setattro, slot_tp_setattro, wrap_setattr,
            "__setattr__($self, name, value, /)\n--\n\nImplement setattr(self, name, value)."),
     TPSLOT("__delattr__", tp_setattro, slot_tp_setattro, wrap_delattr,

Misc/NEWS.d/next/Core and Builtins/2022-06-18-17-00-33.gh-issue-93911.y286of.rst

@@ -3698,6 +3698,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
             DEOPT_IF(cls->tp_version_tag != type_version, LOAD_ATTR);
             assert(type_version != 0);
             PyObject *fget = read_obj(cache->descr);
+            assert(Py_IS_TYPE(fget, &PyFunction_Type));
             PyFunctionObject *f = (PyFunctionObject *)fget;
             uint32_t func_version = read_u32(cache->keys_version);
             assert(func_version != 0);
@@ -3709,8 +3710,8 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
             Py_INCREF(fget);
             _PyInterpreterFrame *new_frame = _PyFrame_PushUnchecked(tstate, f);
             SET_TOP(NULL);
-            int push_null = !(oparg & 1);
-            STACK_SHRINK(push_null);
+            int shrink_stack = !(oparg & 1);
+            STACK_SHRINK(shrink_stack);
             new_frame->localsplus[0] = owner;
             for (int i = 1; i < code->co_nlocalsplus; i++) {
                 new_frame->localsplus[i] = NULL;
@@ -3724,6 +3725,44 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int
             goto start_frame;
         }
 
+        TARGET(LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN) {
+            assert(cframe.use_tracing == 0);
+            DEOPT_IF(tstate->interp->eval_frame, LOAD_ATTR);
+            _PyLoadMethodCache *cache = (_PyLoadMethodCache *)next_instr;
+            PyObject *owner = TOP();
+            PyTypeObject *cls = Py_TYPE(owner);
+            uint32_t type_version = read_u32(cache->type_version);
+            DEOPT_IF(cls->tp_version_tag != type_version, LOAD_ATTR);
+            assert(type_version != 0);
+            PyObject *getattribute = read_obj(cache->descr);
+            assert(Py_IS_TYPE(getattribute, &PyFunction_Type));
+            PyFunctionObject *f = (PyFunctionObject *)getattribute;
+            PyCodeObject *code = (PyCodeObject *)f->func_code;
+            DEOPT_IF(((PyCodeObject *)f->func_code)->co_argcount != 2, LOAD_ATTR);
+            DEOPT_IF(!_PyThreadState_HasStackSpace(tstate, code->co_framesize), CALL);
+            STAT_INC(LOAD_ATTR, hit);
+
+            PyObject *name = GETITEM(names, oparg >> 1);
+            Py_INCREF(f);
+            _PyInterpreterFrame *new_frame = _PyFrame_PushUnchecked(tstate, f);
+            SET_TOP(NULL);
+            int shrink_stack = !(oparg & 1);
+            STACK_SHRINK(shrink_stack);
+            Py_INCREF(name);
+            new_frame->localsplus[0] = owner;
+            new_frame->localsplus[1] = name;
+            for (int i = 2; i < code->co_nlocalsplus; i++) {
+                new_frame->localsplus[i] = NULL;
+            }
+            _PyFrame_SetStackPointer(frame, stack_pointer);
+            JUMPBY(INLINE_CACHE_ENTRIES_LOAD_ATTR);
+            frame->prev_instr = next_instr - 1;
+            new_frame->previous = frame;
+            frame = cframe.current_frame = new_frame;
+            CALL_STAT_INC(inlined_py_calls);
+            goto start_frame;
+        }
+
         TARGET(STORE_ATTR_ADAPTIVE) {
             assert(cframe.use_tracing == 0);
             _PyAttrCache *cache = (_PyAttrCache *)next_instr;

Objects/typeobject.c

@@ -787,6 +787,9 @@ pycore_init_builtins(PyThreadState *tstate)
     PyObject *list_append = _PyType_Lookup(&PyList_Type, &_Py_ID(append));
     assert(list_append);
     interp->callable_cache.list_append = list_append;
+    PyObject *object__getattribute__ = _PyType_Lookup(&PyBaseObject_Type, &_Py_ID(__getattribute__));
+    assert(object__getattribute__);
+    interp->callable_cache.object__getattribute__ = object__getattribute__;
 
     if (_PyBuiltins_AddExceptions(bimod) < 0) {
         return _PyStatus_ERR("failed to add exceptions to builtins");

Python/ceval.c

@@ -362,6 +362,8 @@ miss_counter_start(void) {
 #define SPEC_FAIL_OUT_OF_RANGE 4
 #define SPEC_FAIL_EXPECTED_ERROR 5
 #define SPEC_FAIL_WRONG_NUMBER_ARGUMENTS 6
+#define SPEC_FAIL_NOT_PY_FUNCTION 7
+
 
 #define SPEC_FAIL_LOAD_GLOBAL_NON_STRING_OR_SPLIT 18
 
@@ -387,6 +389,7 @@ miss_counter_start(void) {
 #define SPEC_FAIL_ATTR_HAS_MANAGED_DICT 25
 #define SPEC_FAIL_ATTR_INSTANCE_ATTRIBUTE 26
 #define SPEC_FAIL_ATTR_METACLASS_ATTRIBUTE 27
+#define SPEC_FAIL_ATTR_PROPERTY_NOT_PY_FUNCTION 28
 
 /* Binary subscr and store subscr */
 
@@ -498,6 +501,9 @@ miss_counter_start(void) {
 #define SPEC_FAIL_UNPACK_SEQUENCE_ITERATOR 8
 #define SPEC_FAIL_UNPACK_SEQUENCE_SEQUENCE 9
 
+static int function_kind(PyCodeObject *code);
+static bool function_check_args(PyObject *o, int expected_argcount, int opcode);
+static uint32_t function_get_version(PyObject *o, int opcode);
 
 static int
 specialize_module_load_attr(PyObject *owner, _Py_CODEUNIT *instr,
@@ -557,21 +563,58 @@ typedef enum {
     MUTABLE,   /* Instance of a mutable class; might, or might not, be a descriptor */
     ABSENT, /* Attribute is not present on the class */
     DUNDER_CLASS, /* __class__ attribute */
-    GETSET_OVERRIDDEN /* __getattribute__ or __setattr__ has been overridden */
+    GETSET_OVERRIDDEN, /* __getattribute__ or __setattr__ has been overridden */
+    GETATTRIBUTE_IS_PYTHON_FUNCTION  /* Descriptor requires calling a Python __getattribute__ */
 } DescriptorClassification;
 
 
 static DescriptorClassification
 analyze_descriptor(PyTypeObject *type, PyObject *name, PyObject **descr, int store)
 {
+    bool has_getattr = false;
     if (store) {
         if (type->tp_setattro != PyObject_GenericSetAttr) {
             *descr = NULL;
             return GETSET_OVERRIDDEN;
         }
     }
     else {
-        if (type->tp_getattro != PyObject_GenericGetAttr) {
+        getattrofunc getattro_slot = type->tp_getattro;
+        if (getattro_slot == PyObject_GenericGetAttr) {
+            /* Normal attribute lookup; */
+            has_getattr = false;
+        }
+        else if (getattro_slot == _Py_slot_tp_getattr_hook ||
+            getattro_slot == _Py_slot_tp_getattro) {
+            /* One or both of __getattribute__ or __getattr__ may have been
+             overridden See typeobject.c for why these functions are special. */
+            PyObject *getattribute = _PyType_Lookup(type,
+                &_Py_ID(__getattribute__));
+            PyInterpreterState *interp = _PyInterpreterState_GET();
+            bool has_custom_getattribute = getattribute != NULL &&
+                getattribute != interp->callable_cache.object__getattribute__;
+            has_getattr = _PyType_Lookup(type, &_Py_ID(__getattr__)) != NULL;
+            if (has_custom_getattribute) {
+                if (getattro_slot == _Py_slot_tp_getattro &&
+                    !has_getattr &&
+                    Py_IS_TYPE(getattribute, &PyFunction_Type)) {
+                    *descr = getattribute;
+                    return GETATTRIBUTE_IS_PYTHON_FUNCTION;
+                }
+                /* Potentially both __getattr__ and __getattribute__ are set.
+                   Too complicated */
+                *descr = NULL;
+                return GETSET_OVERRIDDEN;
+            }
+            /* Potentially has __getattr__ but no custom __getattribute__.
+               Fall through to usual descriptor analysis.
+               Usual attribute lookup should only be allowed at runtime
+               if we can guarantee that there is no way an exception can be
+               raised. This means some specializations, e.g. specializing
+               for property() isn't safe.
+            */
+        }
+        else {
             *descr = NULL;
             return GETSET_OVERRIDDEN;
         }
@@ -595,7 +638,10 @@ analyze_descriptor(PyTypeObject *type, PyObject *name, PyObject **descr, int sto
             return OTHER_SLOT;
         }
         if (desc_cls == &PyProperty_Type) {
-            return PROPERTY;
+            /* We can't detect at runtime whether an attribute exists
+               with property. So that means we may have to call
+               __getattr__. */
+            return has_getattr ? GETSET_OVERRIDDEN : PROPERTY;
         }
         if (PyUnicode_CompareWithASCIIString(name, "__class__") == 0) {
             if (descriptor == _PyType_Lookup(&PyBaseObject_Type, name)) {
@@ -674,7 +720,6 @@ specialize_dict_access(
 static int specialize_attr_loadmethod(PyObject* owner, _Py_CODEUNIT* instr, PyObject* name,
     PyObject* descr, DescriptorClassification kind);
 static int specialize_class_load_attr(PyObject* owner, _Py_CODEUNIT* instr, PyObject* name);
-static int function_kind(PyCodeObject *code);
 
 int
 _Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name)
@@ -729,24 +774,13 @@ _Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name)
                 SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_EXPECTED_ERROR);
                 goto fail;
             }
-            if (Py_TYPE(fget) != &PyFunction_Type) {
-                SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_PROPERTY);
+            if (!Py_IS_TYPE(fget, &PyFunction_Type)) {
+                SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_PROPERTY_NOT_PY_FUNCTION);
                 goto fail;
             }
-            PyFunctionObject *func = (PyFunctionObject *)fget;
-            PyCodeObject *fcode = (PyCodeObject *)func->func_code;
-            int kind = function_kind(fcode);
-            if (kind != SIMPLE_FUNCTION) {
-                SPECIALIZATION_FAIL(LOAD_ATTR, kind);
-                goto fail;
-            }
-            if (fcode->co_argcount != 1) {
-                SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_WRONG_NUMBER_ARGUMENTS);
-                goto fail;
-            }
-            int version = _PyFunction_GetVersionForCurrentState(func);
+            uint32_t version = function_check_args(fget, 1, LOAD_ATTR) &&
+                function_get_version(fget, LOAD_ATTR);
             if (version == 0) {
-                SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OUT_OF_VERSIONS);
                 goto fail;
             }
             write_u32(lm_cache->keys_version, version);
@@ -795,6 +829,22 @@ _Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name)
         case GETSET_OVERRIDDEN:
             SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OVERRIDDEN);
             goto fail;
+        case GETATTRIBUTE_IS_PYTHON_FUNCTION:
+        {
+            assert(type->tp_getattro == _Py_slot_tp_getattro);
+            assert(Py_IS_TYPE(descr, &PyFunction_Type));
+            _PyLoadMethodCache *lm_cache = (_PyLoadMethodCache *)(instr + 1);
+            uint32_t func_version = function_check_args(descr, 2, LOAD_ATTR) &&
+                function_get_version(descr, LOAD_ATTR);
+            if (func_version == 0) {
+                goto fail;
+            }
+            /* borrowed */
+            write_obj(lm_cache->descr, descr);
+            write_u32(lm_cache->type_version, type->tp_version_tag);
+            _Py_SET_OPCODE(*instr, LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN);
+            goto success;
+        }
         case BUILTIN_CLASSMETHOD:
         case PYTHON_CLASSMETHOD:
         case NON_OVERRIDING:
@@ -873,6 +923,7 @@ _Py_Specialize_StoreAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name)
         case MUTABLE:
             SPECIALIZATION_FAIL(STORE_ATTR, SPEC_FAIL_ATTR_MUTABLE_CLASS);
             goto fail;
+        case GETATTRIBUTE_IS_PYTHON_FUNCTION:
         case GETSET_OVERRIDDEN:
             SPECIALIZATION_FAIL(STORE_ATTR, SPEC_FAIL_OVERRIDDEN);
             goto fail;
@@ -1215,6 +1266,39 @@ function_kind(PyCodeObject *code) {
     return SIMPLE_FUNCTION;
 }
 
+/* Returning false indicates a failure. */
+static bool
+function_check_args(PyObject *o, int expected_argcount, int opcode)
+{
+    assert(Py_IS_TYPE(o, &PyFunction_Type));
+    PyFunctionObject *func = (PyFunctionObject *)o;
+    PyCodeObject *fcode = (PyCodeObject *)func->func_code;
+    int kind = function_kind(fcode);
+    if (kind != SIMPLE_FUNCTION) {
+        SPECIALIZATION_FAIL(opcode, kind);
+        return false;
+    }
+    if (fcode->co_argcount != expected_argcount) {
+        SPECIALIZATION_FAIL(opcode, SPEC_FAIL_WRONG_NUMBER_ARGUMENTS);
+        return false;
+    }
+    return true;
+}
+
+/* Returning 0 indicates a failure. */
+static uint32_t
+function_get_version(PyObject *o, int opcode)
+{
+    assert(Py_IS_TYPE(o, &PyFunction_Type));
+    PyFunctionObject *func = (PyFunctionObject *)o;
+    uint32_t version = _PyFunction_GetVersionForCurrentState(func);
+    if (version == 0) {
+        SPECIALIZATION_FAIL(opcode, SPEC_FAIL_OUT_OF_VERSIONS);
+        return 0;
+    }
+    return version;
+}
+
 int
 _Py_Specialize_BinarySubscr(
      PyObject *container, PyObject *sub, _Py_CODEUNIT *instr)