[mypyc] Use PyList_Check for isinstance(obj, list) (#19416)

Added a primitive to translate `isinstance(obj, list)` to
`PyList_Check(obj)` instead of `PyObject_IsInstance(obj, type)`, as the
former is faster. Similar primitives can be added for other built-in
types, which I plan to do in next PRs.

```
def f(x) -> bool:
    return isinstance(x, list)

def bench(n: int) -> None:
    for x in range(n):
        if x % 2 == 0:
            f(x)
        else:
            f([x])

from time import time
bench(1000)
t0 = time()
bench(50 * 1000 * 1000)
print(time() - t0)
```

Using the above benchmark, execution time goes from ~1.4s to ~0.97s on
my machine.

Author: p-sawicki

mypyc/irbuild/specialize.py

@@ -14,7 +14,7 @@
 
 from __future__ import annotations
 
-from typing import Callable, Optional
+from typing import Callable, Final, Optional
 
 from mypy.nodes import (
     ARG_NAMED,
@@ -89,7 +89,7 @@
     dict_setdefault_spec_init_op,
     dict_values_op,
 )
-from mypyc.primitives.list_ops import new_list_set_item_op
+from mypyc.primitives.list_ops import isinstance_list, new_list_set_item_op
 from mypyc.primitives.str_ops import (
     str_encode_ascii_strict,
     str_encode_latin1_strict,
@@ -546,6 +546,9 @@ def gen_inner_stmts() -> None:
     return retval
 
 
+isinstance_primitives: Final = {"builtins.list": isinstance_list}
+
+
 @specialize_function("builtins.isinstance")
 def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Value | None:
     """Special case for builtins.isinstance.
@@ -554,11 +557,10 @@ def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) ->
     there is no need to coerce something to a new type before checking
     what type it is, and the coercion could lead to bugs.
     """
-    if (
-        len(expr.args) == 2
-        and expr.arg_kinds == [ARG_POS, ARG_POS]
-        and isinstance(expr.args[1], (RefExpr, TupleExpr))
-    ):
+    if not (len(expr.args) == 2 and expr.arg_kinds == [ARG_POS, ARG_POS]):
+        return None
+
+    if isinstance(expr.args[1], (RefExpr, TupleExpr)):
         builder.types[expr.args[0]] = AnyType(TypeOfAny.from_error)
 
         irs = builder.flatten_classes(expr.args[1])
@@ -569,6 +571,15 @@ def translate_isinstance(builder: IRBuilder, expr: CallExpr, callee: RefExpr) ->
             )
             obj = builder.accept(expr.args[0], can_borrow=can_borrow)
             return builder.builder.isinstance_helper(obj, irs, expr.line)
+
+    if isinstance(expr.args[1], RefExpr):
+        node = expr.args[1].node
+        if node:
+            desc = isinstance_primitives.get(node.fullname)
+            if desc:
+                obj = builder.accept(expr.args[0])
+                return builder.primitive_op(desc, [obj], expr.line)
+
     return None
 
 

mypyc/primitives/list_ops.py

@@ -55,6 +55,15 @@
     extra_int_constants=[(0, int_rprimitive)],
 )
 
+# isinstance(obj, list)
+isinstance_list = function_op(
+    name="builtins.isinstance",
+    arg_types=[object_rprimitive],
+    return_type=bit_rprimitive,
+    c_function_name="PyList_Check",
+    error_kind=ERR_NEVER,
+)
+
 new_list_op = custom_op(
     arg_types=[c_pyssize_t_rprimitive],
     return_type=list_rprimitive,

mypyc/test-data/irbuild-lists.test

@@ -498,29 +498,23 @@ def nested_union(a: Union[List[str], List[Optional[str]]]) -> None:
 [out]
 def narrow(a):
     a :: union[list, int]
-    r0 :: object
-    r1 :: i32
-    r2 :: bit
-    r3 :: bool
-    r4 :: list
-    r5 :: native_int
-    r6 :: short_int
-    r7 :: int
+    r0 :: bit
+    r1 :: list
+    r2 :: native_int
+    r3 :: short_int
+    r4 :: int
 L0:
-    r0 = load_address PyList_Type
-    r1 = PyObject_IsInstance(a, r0)
-    r2 = r1 >= 0 :: signed
-    r3 = truncate r1: i32 to builtins.bool
-    if r3 goto L1 else goto L2 :: bool
+    r0 = PyList_Check(a)
+    if r0 goto L1 else goto L2 :: bool
 L1:
-    r4 = borrow cast(list, a)
-    r5 = var_object_size r4
-    r6 = r5 << 1
+    r1 = borrow cast(list, a)
+    r2 = var_object_size r1
+    r3 = r2 << 1
     keep_alive a
-    return r6
+    return r3
 L2:
-    r7 = unbox(int, a)
-    return r7
+    r4 = unbox(int, a)
+    return r4
 def loop(a):
     a :: list
     r0 :: short_int

mypyc/test-data/run-lists.test

@@ -466,7 +466,7 @@ assert not list_in_mixed(object)
 assert list_in_mixed(type)
 
 [case testListBuiltFromGenerator]
-def test() -> None:
+def test_from_gen() -> None:
     source_a = ["a", "b", "c"]
     a = list(x + "f2" for x in source_a)
     assert a == ["af2", "bf2", "cf2"]
@@ -486,12 +486,6 @@ def test() -> None:
     f = list("str:" + x for x in source_str)
     assert f == ["str:a", "str:b", "str:c", "str:d"]
 
-[case testNextBug]
-from typing import List, Optional
-
-def test(x: List[int]) -> None:
-    res = next((i for i in x), None)
-
 [case testListGetItemWithBorrow]
 from typing import List
 
@@ -537,3 +531,35 @@ def test_sorted() -> None:
     assert sorted((2, 1, 3)) == res
     assert sorted({2, 1, 3}) == res
     assert sorted({2: "", 1: "", 3: ""}) == res
+
+[case testIsInstance]
+from copysubclass import subc
+def test_built_in() -> None:
+    assert isinstance([], list)
+    assert isinstance([1,2,3], list)
+    assert isinstance(['a','b'], list)
+    assert isinstance(subc(), list)
+    assert isinstance(subc([1,2,3]), list)
+    assert isinstance(subc(['a','b']), list)
+
+    assert not isinstance({}, list)
+    assert not isinstance((), list)
+    assert not isinstance((1,2,3), list)
+    assert not isinstance(('a','b'), list)
+    assert not isinstance(1, list)
+    assert not isinstance('a', list)
+
+def test_user_defined() -> None:
+    from userdefinedlist import list
+
+    assert isinstance(list(), list)
+    assert not isinstance([list()], list)
+
+[file copysubclass.py]
+from typing import Any
+class subc(list[Any]):
+    pass
+
+[file userdefinedlist.py]
+class list:
+    pass