"""Generate classes representing function environments (+ related operations). If we have a nested function that has non-local (free) variables, access to the non-locals is via an instance of an environment class. Example: def f() -> int: x = 0 # Make 'x' an attribute of an environment class instance def g() -> int: # We have access to the environment class instance to # allow accessing 'x' return x + 2 x = x + 1 # Modify the attribute return g() """ from __future__ import annotations from mypy.nodes import Argument, FuncDef, SymbolNode, Var from mypyc.common import BITMAP_BITS, ENV_ATTR_NAME, SELF_NAME, bitmap_name from mypyc.ir.class_ir import ClassIR from mypyc.ir.ops import Call, GetAttr, SetAttr, Value from mypyc.ir.rtypes import RInstance, bitmap_rprimitive, object_rprimitive from mypyc.irbuild.builder import IRBuilder, SymbolTarget from mypyc.irbuild.context import FuncInfo, GeneratorClass, ImplicitClass from mypyc.irbuild.targets import AssignmentTargetAttr def setup_env_class(builder: IRBuilder) -> ClassIR: """Generate a class representing a function environment. Note that the variables in the function environment are not actually populated here. This is because when the environment class is generated, the function environment has not yet been visited. This behavior is allowed so that when the compiler visits nested functions, it can use the returned ClassIR instance to figure out free variables it needs to access. The remaining attributes of the environment class are populated when the environment registers are loaded. Return a ClassIR representing an environment for a function containing a nested function. """ env_class = ClassIR( f"{builder.fn_info.namespaced_name()}_env", builder.module_name, is_generated=True ) env_class.attributes[SELF_NAME] = RInstance(env_class) if builder.fn_info.is_nested: # If the function is nested, its environment class must contain an environment # attribute pointing to its encapsulating functions' environment class. env_class.attributes[ENV_ATTR_NAME] = RInstance(builder.fn_infos[-2].env_class) env_class.mro = [env_class] builder.fn_info.env_class = env_class builder.classes.append(env_class) return env_class def finalize_env_class(builder: IRBuilder) -> None: """Generate, instantiate, and set up the environment of an environment class.""" instantiate_env_class(builder) # Iterate through the function arguments and replace local definitions (using registers) # that were previously added to the environment with references to the function's # environment class. if builder.fn_info.is_nested: add_args_to_env(builder, local=False, base=builder.fn_info.callable_class) else: add_args_to_env(builder, local=False, base=builder.fn_info) def instantiate_env_class(builder: IRBuilder) -> Value: """Assign an environment class to a register named after the given function definition.""" curr_env_reg = builder.add( Call(builder.fn_info.env_class.ctor, [], builder.fn_info.fitem.line) ) if builder.fn_info.is_nested: builder.fn_info.callable_class._curr_env_reg = curr_env_reg builder.add( SetAttr( curr_env_reg, ENV_ATTR_NAME, builder.fn_info.callable_class.prev_env_reg, builder.fn_info.fitem.line, ) ) else: builder.fn_info._curr_env_reg = curr_env_reg return curr_env_reg def load_env_registers(builder: IRBuilder) -> None: """Load the registers for the current FuncItem being visited. Adds the arguments of the FuncItem to the environment. If the FuncItem is nested inside of another function, then this also loads all of the outer environments of the FuncItem into registers so that they can be used when accessing free variables. """ add_args_to_env(builder, local=True) fn_info = builder.fn_info fitem = fn_info.fitem if fn_info.is_nested: load_outer_envs(builder, fn_info.callable_class) # If this is a FuncDef, then make sure to load the FuncDef into its own environment # class so that the function can be called recursively. if isinstance(fitem, FuncDef) and fn_info.add_nested_funcs_to_env: setup_func_for_recursive_call(builder, fitem, fn_info.callable_class) def load_outer_env( builder: IRBuilder, base: Value, outer_env: dict[SymbolNode, SymbolTarget] ) -> Value: """Load the environment class for a given base into a register. Additionally, iterates through all of the SymbolNode and AssignmentTarget instances of the environment at the given index's symtable, and adds those instances to the environment of the current environment. This is done so that the current environment can access outer environment variables without having to reload all of the environment registers. Returns the register where the environment class was loaded. """ env = builder.add(GetAttr(base, ENV_ATTR_NAME, builder.fn_info.fitem.line)) assert isinstance(env.type, RInstance), f"{env} must be of type RInstance" for symbol, target in outer_env.items(): env.type.class_ir.attributes[symbol.name] = target.type symbol_target = AssignmentTargetAttr(env, symbol.name) builder.add_target(symbol, symbol_target) return env def load_outer_envs(builder: IRBuilder, base: ImplicitClass) -> None: index = len(builder.builders) - 2 # Load the first outer environment. This one is special because it gets saved in the # FuncInfo instance's prev_env_reg field. if index > 1: # outer_env = builder.fn_infos[index].environment outer_env = builder.symtables[index] if isinstance(base, GeneratorClass): base.prev_env_reg = load_outer_env(builder, base.curr_env_reg, outer_env) else: base.prev_env_reg = load_outer_env(builder, base.self_reg, outer_env) env_reg = base.prev_env_reg index -= 1 # Load the remaining outer environments into registers. while index > 1: # outer_env = builder.fn_infos[index].environment outer_env = builder.symtables[index] env_reg = load_outer_env(builder, env_reg, outer_env) index -= 1 def num_bitmap_args(builder: IRBuilder, args: list[Argument]) -> int: n = 0 for arg in args: t = builder.type_to_rtype(arg.variable.type) if t.error_overlap and arg.kind.is_optional(): n += 1 return (n + (BITMAP_BITS - 1)) // BITMAP_BITS def add_args_to_env( builder: IRBuilder, local: bool = True, base: FuncInfo | ImplicitClass | None = None, reassign: bool = True, ) -> None: fn_info = builder.fn_info args = fn_info.fitem.arguments nb = num_bitmap_args(builder, args) if local: for arg in args: rtype = builder.type_to_rtype(arg.variable.type) builder.add_local_reg(arg.variable, rtype, is_arg=True) for i in reversed(range(nb)): builder.add_local_reg(Var(bitmap_name(i)), bitmap_rprimitive, is_arg=True) else: for arg in args: if is_free_variable(builder, arg.variable) or fn_info.is_generator: rtype = builder.type_to_rtype(arg.variable.type) assert base is not None, "base cannot be None for adding nonlocal args" builder.add_var_to_env_class(arg.variable, rtype, base, reassign=reassign) def add_vars_to_env(builder: IRBuilder) -> None: """Add relevant local variables and nested functions to the environment class. Add all variables and functions that are declared/defined within current function and are referenced in functions nested within this one to this function's environment class so the nested functions can reference them even if they are declared after the nested function's definition. Note that this is done before visiting the body of the function. """ env_for_func: FuncInfo | ImplicitClass = builder.fn_info if builder.fn_info.is_generator: env_for_func = builder.fn_info.generator_class elif builder.fn_info.is_nested or builder.fn_info.in_non_ext: env_for_func = builder.fn_info.callable_class if builder.fn_info.fitem in builder.free_variables: # Sort the variables to keep things deterministic for var in sorted(builder.free_variables[builder.fn_info.fitem], key=lambda x: x.name): if isinstance(var, Var): rtype = builder.type_to_rtype(var.type) builder.add_var_to_env_class(var, rtype, env_for_func, reassign=False) if builder.fn_info.fitem in builder.encapsulating_funcs: for nested_fn in builder.encapsulating_funcs[builder.fn_info.fitem]: if isinstance(nested_fn, FuncDef): # The return type is 'object' instead of an RInstance of the # callable class because differently defined functions with # the same name and signature across conditional blocks # will generate different callable classes, so the callable # class that gets instantiated must be generic. builder.add_var_to_env_class( nested_fn, object_rprimitive, env_for_func, reassign=False ) def setup_func_for_recursive_call(builder: IRBuilder, fdef: FuncDef, base: ImplicitClass) -> None: """Enable calling a nested function (with a callable class) recursively. Adds the instance of the callable class representing the given FuncDef to a register in the environment so that the function can be called recursively. Note that this needs to be done only for nested functions. """ # First, set the attribute of the environment class so that GetAttr can be called on it. prev_env = builder.fn_infos[-2].env_class prev_env.attributes[fdef.name] = builder.type_to_rtype(fdef.type) if isinstance(base, GeneratorClass): # If we are dealing with a generator class, then we need to first get the register # holding the current environment class, and load the previous environment class from # there. prev_env_reg = builder.add(GetAttr(base.curr_env_reg, ENV_ATTR_NAME, -1)) else: prev_env_reg = base.prev_env_reg # Obtain the instance of the callable class representing the FuncDef, and add it to the # current environment. val = builder.add(GetAttr(prev_env_reg, fdef.name, -1)) target = builder.add_local_reg(fdef, object_rprimitive) builder.assign(target, val, -1) def is_free_variable(builder: IRBuilder, symbol: SymbolNode) -> bool: fitem = builder.fn_info.fitem return fitem in builder.free_variables and symbol in builder.free_variables[fitem]