[mypyc] feat: ForFilter generator helper for builtins.filter

mypyc/doc/native_operations.rst

@@ -54,3 +54,4 @@ These variants of statements have custom implementations:
 * ``for ... in seq:`` (for loop over a sequence)
 * ``for ... in enumerate(...):``
 * ``for ... in zip(...):``
+* ``for ... in filter(...):``

mypyc/irbuild/for_helpers.py

@@ -499,6 +499,16 @@ def make_for_loop_generator(
             for_list = ForSequence(builder, index, body_block, loop_exit, line, nested)
             for_list.init(expr_reg, target_type, reverse=True)
             return for_list
+
+        elif (
+            expr.callee.fullname == "builtins.filter"
+            and len(expr.args) == 2
+            and all(k == ARG_POS for k in expr.arg_kinds)
+        ):
+            for_filter = ForFilter(builder, index, body_block, loop_exit, line, nested)
+            for_filter.init(index, expr.args[0], expr.args[1])
+            return for_filter
+
     if isinstance(expr, CallExpr) and isinstance(expr.callee, MemberExpr) and not expr.args:
         # Special cases for dictionary iterator methods, like dict.items().
         rtype = builder.node_type(expr.callee.expr)
@@ -1180,6 +1190,76 @@ def gen_cleanup(self) -> None:
             gen.gen_cleanup()
 
 
+class ForFilter(ForGenerator):
+    """Generate optimized IR for a for loop over filter(f, iterable)."""
+
+    def need_cleanup(self) -> bool:
+        # The wrapped for loops might need cleanup. We might generate a
+        # redundant cleanup block, but that's okay.
+        return True
+
+    def init(self, index: Lvalue, func: Expression, iterable: Expression) -> None:
+        self.filter_func_def = func
+        if (
+            isinstance(func, NameExpr)
+            and isinstance(func.node, Var)
+            and func.node.fullname == "builtins.None"
+        ):
+            self.filter_func_val = None
+        else:
+            self.filter_func_val = self.builder.accept(func)
+        self.iterable = iterable
+        self.index = index
+
+        self.gen = make_for_loop_generator(
+            self.builder,
+            self.index,
+            self.iterable,
+            self.body_block,
+            self.loop_exit,
+            self.line,
+            is_async=False,
+            nested=True,
+        )
+
+    def gen_condition(self) -> None:
+        self.gen.gen_condition()
+
+    def begin_body(self) -> None:
+        # 1. Assign the next item to the loop variable
+        self.gen.begin_body()
+
+        # 2. Call the filter function
+        builder = self.builder
+        line = self.line
+        item = builder.read(builder.get_assignment_target(self.index), line)
+
+        if self.filter_func_val is None:
+            result = item
+        else:
+            fake_call_expr = CallExpr(self.filter_func_def, [self.index], [ARG_POS], [None])
+
+            # I put this here to prevent a circular import
+            # from mypyc.irbuild.expression import transform_call_expr
+
+            # result = transform_call_expr(builder, fake_call_expr)
+            result = builder.accept(fake_call_expr)
+
+        # Now, filter: only enter the body if func(item) is truthy
+        cont_block, rest_block = BasicBlock(), BasicBlock()
+        builder.add_bool_branch(result, rest_block, cont_block)
+        builder.activate_block(cont_block)
+        builder.nonlocal_control[-1].gen_continue(builder, line)
+        builder.goto_and_activate(rest_block)
+        # At this point, the rest of the loop body (user code) will be emitted
+
+    def gen_step(self) -> None:
+        self.gen.gen_step()
+
+    def gen_cleanup(self) -> None:
+        self.gen.gen_cleanup()
+
+
 def get_expr_length(expr: Expression) -> int | None:
     if isinstance(expr, (StrExpr, BytesExpr)):
         return len(expr.value)

mypyc/test-data/fixtures/ir.py

@@ -410,3 +410,11 @@ class classmethod: pass
 class staticmethod: pass
 
 NotImplemented: Any = ...
+
+class filter(Generic[_T]):
+    @overload
+    def __new__(cls, function: None, iterable: Iterable[_T | None], /) -> Self: ...
+    @overload
+    def __new__(cls, function: Callable[[_T], Any], iterable: Iterable[_T], /) -> Self: ...
+    def __iter__(self) -> Self: ...
+    def __next__(self) -> _T: ...

mypyc/test-data/irbuild-basic.test

@@ -3552,6 +3552,278 @@ L0:
     r3 = box(None, 1)
     return r3
 
+[case testForFilterBool]
+def f(x: int) -> bool:
+    return bool(x % 2)
+def g(a: list[int]) -> int:
+    s = 0
+    for x in filter(f, a):
+        s += x
+    return s
+[out]
+def f(x):
+    x, r0 :: int
+    r1 :: bit
+L0:
+    r0 = CPyTagged_Remainder(x, 4)
+    r1 = r0 != 0
+    return r1
+def g(a):
+    a :: list
+    s :: int
+    r0 :: dict
+    r1 :: str
+    r2 :: object
+    r3, r4 :: native_int
+    r5 :: bit
+    r6 :: object
+    r7, x :: int
+    r8 :: bool
+    r9 :: int
+    r10 :: native_int
+L0:
+    s = 0
+    r0 = __main__.globals :: static
+    r1 = 'f'
+    r2 = CPyDict_GetItem(r0, r1)
+    r3 = 0
+L1:
+    r4 = var_object_size a
+    r5 = r3 < r4 :: signed
+    if r5 goto L2 else goto L6 :: bool
+L2:
+    r6 = list_get_item_unsafe a, r3
+    r7 = unbox(int, r6)
+    x = r7
+    r8 = f(x)
+    if r8 goto L4 else goto L3 :: bool
+L3:
+    goto L5
+L4:
+    r9 = CPyTagged_Add(s, x)
+    s = r9
+L5:
+    r10 = r3 + 1
+    r3 = r10
+    goto L1
+L6:
+L7:
+    return s
+
+[case testForFilterInt]
+def f(x: int) -> int:
+    return x % 2
+def g(a: list[int]) -> int:
+    s = 0
+    for x in filter(f, a):
+        s += x
+    return s
+[out]
+def f(x):
+    x, r0 :: int
+L0:
+    r0 = CPyTagged_Remainder(x, 4)
+    return r0
+def g(a):
+    a :: list
+    s :: int
+    r0 :: dict
+    r1 :: str
+    r2 :: object
+    r3, r4 :: native_int
+    r5 :: bit
+    r6 :: object
+    r7, x, r8 :: int
+    r9 :: bit
+    r10 :: int
+    r11 :: native_int
+L0:
+    s = 0
+    r0 = __main__.globals :: static
+    r1 = 'f'
+    r2 = CPyDict_GetItem(r0, r1)
+    r3 = 0
+L1:
+    r4 = var_object_size a
+    r5 = r3 < r4 :: signed
+    if r5 goto L2 else goto L6 :: bool
+L2:
+    r6 = list_get_item_unsafe a, r3
+    r7 = unbox(int, r6)
+    x = r7
+    r8 = f(x)
+    r9 = r8 != 0
+    if r9 goto L4 else goto L3 :: bool
+L3:
+    goto L5
+L4:
+    r10 = CPyTagged_Add(s, x)
+    s = r10
+L5:
+    r11 = r3 + 1
+    r3 = r11
+    goto L1
+L6:
+L7:
+    return s
+
+[case testForFilterStr]
+def f(x: int) -> str:
+    return str(x % 2)
+def g(a: list[int]) -> int:
+    s = 0
+    for x in filter(f, a):
+        s += x
+    return s
+[out]
+def f(x):
+    x, r0 :: int
+    r1 :: str
+L0:
+    r0 = CPyTagged_Remainder(x, 4)
+    r1 = CPyTagged_Str(r0)
+    return r1
+def g(a):
+    a :: list
+    s :: int
+    r0 :: dict
+    r1 :: str
+    r2 :: object
+    r3, r4 :: native_int
+    r5 :: bit
+    r6 :: object
+    r7, x :: int
+    r8 :: str
+    r9 :: bit
+    r10 :: int
+    r11 :: native_int
+L0:
+    s = 0
+    r0 = __main__.globals :: static
+    r1 = 'f'
+    r2 = CPyDict_GetItem(r0, r1)
+    r3 = 0
+L1:
+    r4 = var_object_size a
+    r5 = r3 < r4 :: signed
+    if r5 goto L2 else goto L6 :: bool
+L2:
+    r6 = list_get_item_unsafe a, r3
+    r7 = unbox(int, r6)
+    x = r7
+    r8 = f(x)
+    r9 = CPyStr_IsTrue(r8)
+    if r9 goto L4 else goto L3 :: bool
+L3:
+    goto L5
+L4:
+    r10 = CPyTagged_Add(s, x)
+    s = r10
+L5:
+    r11 = r3 + 1
+    r3 = r11
+    goto L1
+L6:
+L7:
+    return s
+
+[case testForFilterPrimitiveOp]
+def f(a: list[list[int]]) -> int:
+    s = 0
+    for x in filter(len, a):
+        s += 1
+    return s
+[out]
+def f(a):
+    a :: list
+    s :: int
+    r0 :: object
+    r1 :: str
+    r2 :: object
+    r3, r4 :: native_int
+    r5 :: bit
+    r6 :: object
+    r7, x :: list
+    r8 :: native_int
+    r9 :: short_int
+    r10 :: bit
+    r11 :: int
+    r12 :: native_int
+L0:
+    s = 0
+    r0 = builtins :: module
+    r1 = 'len'
+    r2 = CPyObject_GetAttr(r0, r1)
+    r3 = 0
+L1:
+    r4 = var_object_size a
+    r5 = r3 < r4 :: signed
+    if r5 goto L2 else goto L6 :: bool
+L2:
+    r6 = list_get_item_unsafe a, r3
+    r7 = cast(list, r6)
+    x = r7
+    r8 = var_object_size x
+    r9 = r8 << 1
+    r10 = r9 != 0
+    if r10 goto L4 else goto L3 :: bool
+L3:
+    goto L5
+L4:
+    r11 = CPyTagged_Add(s, 2)
+    s = r11
+L5:
+    r12 = r3 + 1
+    r3 = r12
+    goto L1
+L6:
+L7:
+    return s
+
+[case testForFilterNone]
+def f(a: list[int]) -> int:
+    c = 0
+    for x in filter(None, a):
+        c += 1
+    return 0
+
+[out]
+def f(a):
+    a :: list
+    c :: int
+    r0, r1 :: native_int
+    r2 :: bit
+    r3 :: object
+    r4, x :: int
+    r5 :: bit
+    r6 :: int
+    r7 :: native_int
+L0:
+    c = 0
+    r0 = 0
+L1:
+    r1 = var_object_size a
+    r2 = r0 < r1 :: signed
+    if r2 goto L2 else goto L6 :: bool
+L2:
+    r3 = list_get_item_unsafe a, r0
+    r4 = unbox(int, r3)
+    x = r4
+    r5 = x != 0
+    if r5 goto L4 else goto L3 :: bool
+L3:
+    goto L5
+L4:
+    r6 = CPyTagged_Add(c, 2)
+    c = r6
+L5:
+    r7 = r0 + 1
+    r0 = r7
+    goto L1
+L6:
+L7:
+    return 0
+
 [case testStarArgFastPathTuple]
 from typing import Any, Callable
 def deco(fn: Callable[..., Any]) -> Callable[..., Any]: