xhs-note-crawling/python/py/Lib/site-packages/torch/_dynamo/codegen.py

"""
This module provides utilities for generating Python bytecode in PyTorch's Dynamo system.
It includes functionality for:
- Constructing bytecode sequences for Python operations
- Managing stack operations and variable tracking
- Handling graph outputs and their conversions
- Supporting different Python versions (3.11+, 3.12+, 3.13+)
- Converting high-level operations to low-level bytecode instructions
- Managing constant loading and attribute access
- Supporting function creation and closure handling
"""

import collections
import dataclasses
import re
import sys
import types
from collections import Counter, deque
from collections.abc import Callable, Iterable
from typing import Any, Optional, TYPE_CHECKING, Union

import torch.nn
from torch.utils._ordered_set import OrderedSet

from . import config, graph_break_hints, utils
from .bytecode_transformation import (
    add_push_null,
    add_push_null_call_function_ex,
    create_binary_subscr,
    create_build_tuple,
    create_call_function,
    create_call_function_ex,
    create_call_method,
    create_dup_top,
    create_instruction,
    create_load_const,
    create_load_method,
    create_rot_n,
    Instruction,
)
from .exc import unimplemented
from .source import AttrSource, ChainedSource, DictGetItemSource, Source
from .utils import is_safe_constant, rot_n_helper
from .variables.base import ValueMutationExisting, VariableTracker
from .variables.functions import (
    ContextlibContextManagerLocalGeneratorObjectVariable,
    LocalGeneratorObjectVariable,
)
from .variables.nn_module import NNModuleVariable
from .variables.tensor import (
    NumpyNdarrayVariable,
    SymNodeVariable,
    TensorVariable,
    UnspecializedPythonVariable,
)
from .variables.torch_function import TensorWithTFOverrideVariable


if TYPE_CHECKING:
    from torch._dynamo.variables.builder import GraphArg

    from .symbolic_convert import InstructionTranslatorBase


@dataclasses.dataclass
class GraphOutputEntry:
    index: int
    variable: VariableTracker


class PyCodegen:
    """
    Helper class uses for constructing Python bytecode
    """

    def __init__(
        self,
        tx: "InstructionTranslatorBase",
        root: Optional[torch.nn.Module] = None,
        graph_output_var: Optional[str] = None,
        tempvars: Optional[dict[Union[VariableTracker, Source], Any]] = None,
        overridden_sources: Optional[dict[Source, Source]] = None,
    ) -> None:
        self.root = root
        self.top_of_stack: Optional[Union[VariableTracker, Source]] = None
        self.uses: Counter[Union[VariableTracker, Source]] = collections.Counter()
        self.graph_outputs: dict[int, GraphOutputEntry] = {}
        self._output: list[Instruction] = []
        # This determines which VariableTracker/Source should be stored as
        # locals, and maps the VariableTracker/Source to the local variable
        # name. Note that it could map to None initially, in which case we'll
        # overwrite it to map to real temporary names via `add_cache`.
        self.tempvars: dict[Union[VariableTracker, Source], Any] = tempvars or {}
        self.tx = tx
        self.graph_output_var = graph_output_var
        self.code_options = self.tx.output.code_options
        self.cell_and_freevars = self.tx.cell_and_freevars
        self.new_var = self.tx.output.new_var
        self.value_from_source: bool = True
        # This serves as a way for codegen to use a different source; we need
        # this because sometimes we can't easily modify the original source
        # without affecting other components, e.g., guards.
        self.overridden_sources: dict[Source, Source] = overridden_sources or {}

    def restore_stack(
        self, stack_values: list[Any], *, value_from_source: bool = True
    ) -> None:
        prev = self.value_from_source
        self.value_from_source &= value_from_source
        try:
            self.foreach(stack_values)
        finally:
            self.value_from_source = prev

    def graph_output_vars(self) -> list[VariableTracker]:
        return [x.variable for x in self.graph_outputs.values()]

    def call_reconstruct(
        self, value: Union[VariableTracker, Source, "GraphArg"]
    ) -> None:
        res = value.reconstruct(self)
        assert res is None, f"reconstruct!=None {value}"

    def add_push_null(
        self, gen_fn: Callable[[], None], call_function_ex: bool = False
    ) -> None:
        """
        `gen_fn` generates instructions via PyCodegen methods
        that push a single callable to the stack.

        `add_push_null` pushes a NULL to the stack before or after the
        instructions generated by `gen_fn`, depending on Python version.

        Will attempt to use the NULL push bit for instructions
        with such bits (LOAD_GLOBAL 3.11+, LOAD_ATTR 3.12+, LOAD_SUPER_ATTR).
        """
        old_len = len(self._output)
        if sys.version_info < (3, 13):
            # gen_fn may DUP_TOP instead if TOS is not cleared.
            # Will cause problems since NULL will be pushed right
            # before the generated instructions in <= 3.12
            self.clear_tos()
        gen_fn()
        # inplace modify self._output
        added_insts = self._output[old_len:]
        del self._output[old_len:]
        if call_function_ex:
            self._output.extend(add_push_null_call_function_ex(added_insts))
        else:
            self._output.extend(add_push_null(added_insts))
        if sys.version_info >= (3, 13):
            # NULL will be at top of stack
            self.clear_tos()

    def __call__(
        self, value: Union[VariableTracker, Source, None], allow_cache: bool = True
    ) -> None:
        """
        Generate code such that top-of-stack (TOS) is set to value.

        `allow_cache` controls the behavior in the following manner. `value` can
        either be a VariableTracker or a Source.

        If `value` is a `Source`, `allow_cache` must be True (invariant asserted
        below). If the source was reconstructed earlier, we will reuse the
        generated code by loading from top of stack or tempvars.

        If `value` is a `VariableTracker`, we have the following cases:

        1) `allow_cache=True`
            a) If the value.source is not None, we will emit the code based on
            `value.source` to handle aliasing.
            b) If value.source is None (example reconstructing a local list
            returned by the compiled function), we will reconstruct the variable
            tracker (w/o any source) to emit bytecode that generates a new
            python object.

            In both cases of value.source being None or not, if the value was
            reconstructed earlier, we will reuse the generated code by loading from
            top of stack or tempvars.

        2) `allow_cache=False` - This is a special case (allow_cache defaults to
        True).
            a) If the value.source is not None, we reconstruct the variable
            tracker and emit a new python object. You might wonder what about
            aliasing? The place where we use this config also has the followup
            code where the original python object is assigned to this new python
            value to handle aliasing (check side_effects.py and search for
            allow_cache=False).

            b) If value.source is None, this is not allowed

        Notable effects:
        1. `self.top_of_stack` will be set to `value`, if we don't codegen
           `value` based on source.
        2. `self.uses[value]` will increment, unless (a). we codegen via
            `top_of_stack` or cached `tempvars`, or (b). `value` has special VT
            types like `NNModuleVariable`, etc.
        """
        assert value is not None
        if isinstance(value, Source):
            # If the source needs to be overridden, use the new one.
            source = self.overridden_sources.get(value, value)
            assert allow_cache is True, "allow_cache must be True for Source"
            if self.top_of_stack is value:
                self._output.append(create_dup_top())
                return

            if self.tempvars.get(source) is not None:
                self._output.append(self.create_load(self.tempvars[source]))
                self.top_of_stack = source
                return

            self.uses[source] += 1
            try:
                self.call_reconstruct(source)
            except NotImplementedError:
                unimplemented(
                    gb_type="Reconstruction failure: source.reconstruct not implemented",
                    context=str(source),
                    explanation=f"Dynamo has no bytecode reconstruction implemented for {type(source)} variable {source}.",
                    hints=[*graph_break_hints.DYNAMO_BUG],
                )
            if source in self.tempvars:
                self._output.append(create_dup_top())
                self.add_cache(source)
            self.top_of_stack = source

            return

        assert isinstance(value, VariableTracker)
        output = self._output
        graph_outputs = self.graph_outputs

        if allow_cache:
            if self.top_of_stack is value:
                output.append(create_dup_top())
                return

            if self.tempvars.get(value) is not None:
                output.append(self.create_load(self.tempvars[value]))
                self.top_of_stack = value
                return

        if value.is_realized() and isinstance(
            value, ContextlibContextManagerLocalGeneratorObjectVariable
        ):
            unimplemented(
                gb_type="reconstructing @contextmanager object",
                context=f"object: {value}",
                explanation="Returning a @contextmanager object from a compiled function is not supported.",
                hints=[
                    *graph_break_hints.SUPPORTABLE,
                ],
            )

        # Dynamo normally prefers codegen from source to account for aliasing.
        if (
            value.source is not None
            and allow_cache
            and not (
                value.is_realized() and isinstance(value, LocalGeneratorObjectVariable)
            )
        ):
            # There's a corner case for export: for instance, if the computation
            # graph is just identity on an input tensor, Dynamo would just emit
            # a `LOAD_FAST` from the input source, rather than generating an
            # identity FX graph.
            #
            # However, export wants to maximize graph capture; in the case
            # above, export _wants to_ obtain an identity FX graph (despite it
            # appears unnecessarily expensive for `torch.compile`), so we have
            # the following option to override Dynamo's preference for codegen
            # from source. Moreover, this option applies recursively, for cases
            # like input tensor being returned in a new dictionary.
            #
            # And why the `ValueMutationExisting` check? Not sure, so leaving it
            # to keep the old behavior, as when `value_from_source` was
            # introduced. TODO sort out the invariants among side effect,
            # codegen and export.
            if (
                isinstance(value.mutation_type, ValueMutationExisting)
                or self.value_from_source
            ):
                return self(value.source)

        if value.is_python_constant() and is_safe_constant(value.as_python_constant()):
            output.append(self.create_load_const(value.as_python_constant()))
        elif isinstance(value, TensorWithTFOverrideVariable):
            graph_outputs_key = self.add_graph_output(value)

            self.add_push_null(
                lambda: self.load_import_from(utils.__name__, "to_subclass")
            )
            self.load_graph_output(graph_outputs[graph_outputs_key].index)
            output.append(
                self.create_load_global(
                    value.global_mangled_class_name(self.tx),  # type: ignore[arg-type]
                    add=True,
                )
            )
            output.extend(create_call_function(2, False))
        elif (
            isinstance(value, SymNodeVariable)
            and value.python_type() is float
            and not self.tx.export
        ):
            # This is a little unusual; force the output convention to be a
            # Tensor here.  Don't do this for export because this is
            # apparently load bearing for export tests (but I am a bit
            # doubtful it actually works in the real world)
            # NB: It works to add_graph_output on a computed expression
            # as_tensor here, because we memoize as_tensor calls on
            # SymNodeVariable!
            graph_outputs_key = self.add_graph_output(
                value.as_tensor(self.tx, torch.float64)
            )

            def gen_fn() -> None:
                self.load_graph_output(graph_outputs[graph_outputs_key].index)
                output.append(self.create_load_attr("item"))

            self.add_push_null(gen_fn)
            output.extend(create_call_function(0, False))
        elif isinstance(
            value,
            (
                TensorVariable,
                SymNodeVariable,
                UnspecializedPythonVariable,
                NumpyNdarrayVariable,
            ),
        ):
            graph_outputs_key = self.add_graph_output(value)

            if isinstance(value, NumpyNdarrayVariable):
                self.add_push_null(
                    lambda: self.load_import_from(utils.__name__, "to_numpy_helper")
                )
                self.load_graph_output(graph_outputs[graph_outputs_key].index)
                output.extend(create_call_function(1, False))
            elif isinstance(value, UnspecializedPythonVariable) and value.need_unwrap:

                def gen_fn() -> None:
                    self.load_graph_output(graph_outputs[graph_outputs_key].index)
                    output.append(self.create_load_attr("item"))

                self.add_push_null(gen_fn)
                output.extend(create_call_function(0, False))
            else:
                self.load_graph_output(graph_outputs[graph_outputs_key].index)
        elif isinstance(value, NNModuleVariable):
            parts = value.module_key.split(".")
            if parts[0] in self.code_options["co_varnames"]:
                output.append(self.create_load(parts[0]))
                parts = parts[1:]
            else:
                assert self.root is not None
                output.append(self.create_load_const_unchecked(self.root))
            for part in parts:
                output.append(self.create_load_attr(part))
        else:
            self.uses[value] += 1
            try:
                self.call_reconstruct(value)
            except NotImplementedError as e:
                unimplemented(
                    gb_type="Reconstruction failure",
                    context=str(value),
                    explanation=f"Dynamo has no bytecode reconstruction implemented for sourceless variable {value}.",
                    hints=[
                        "If Dynamo is attempting to trace a return statement and your code is attempting to return a variable "
                        "that Dynamo cannot reconstruct, then remove it from the return statement.",
                        *graph_break_hints.CAUSED_BY_EARLIER_GRAPH_BREAK,
                        "Report an issue to PyTorch if you need reconstrtuction support. Note that objects that don't have "
                        "reconstruction rules may be fundamentally unreconstructable.",
                    ],
                    from_exc=e,
                )
            if allow_cache and value in self.tempvars:
                self._output.append(create_dup_top())
                self.add_cache(value)

        self.top_of_stack = value

    def add_graph_output(self, value: VariableTracker) -> int:
        graph_outputs_key = id(value.as_proxy())
        if graph_outputs_key not in self.graph_outputs:
            self.graph_outputs[graph_outputs_key] = GraphOutputEntry(
                len(self.graph_outputs), value
            )
        return graph_outputs_key

    def load_graph_output(self, index: int) -> None:
        output = self._output
        assert self.graph_output_var is not None
        output.append(self.create_load(self.graph_output_var))
        output.append(self.create_load_const(index))
        output.append(self.create_binary_subscr())

    def add_cache(self, value: Union[VariableTracker, Source]) -> None:
        var = self.new_var()
        self.tempvars[value] = var
        self._output.append(self.create_store(var))

    def foreach(self, items: Iterable[Union[VariableTracker, Source]]) -> None:
        for i in items:
            self(i)

    def create_binary_subscr(self) -> Instruction:
        return create_binary_subscr()

    def setup_globally_cached(self, name: str, value: Any) -> list[Instruction]:
        """Store value in a new global"""
        name = re.sub(r"[^a-zA-Z0-9_]+", "_", name)
        f_globals = self.tx.f_globals
        if name in f_globals:
            assert id(f_globals[name]) == id(value)
        else:
            f_globals[name] = value
        return [self.create_load_global(name, add=True)]

    def clear_tos(self) -> None:
        self.top_of_stack = None

    def append_output(self, inst: Instruction) -> None:
        assert isinstance(inst, Instruction)
        self._output.append(inst)
        self.clear_tos()

    def extend_output(self, insts: list[Instruction]) -> None:
        assert all(isinstance(x, Instruction) for x in insts)
        self._output.extend(insts)
        self.clear_tos()

    def get_instructions(self) -> list[Instruction]:
        return self._output

    def create_load(self, name: str) -> Instruction:
        assert name in self.code_options["co_varnames"], f"{name} missing"
        return create_instruction("LOAD_FAST", argval=name)

    def create_load_closure(self, name: str) -> Instruction:
        assert name in self.cell_and_freevars()
        inst_name = "LOAD_FAST" if sys.version_info >= (3, 13) else "LOAD_CLOSURE"
        return create_instruction(inst_name, argval=name)

    def create_load_deref(self, name: str) -> Instruction:
        assert name in self.cell_and_freevars()
        return create_instruction("LOAD_DEREF", argval=name)

    def create_store(self, name: str) -> Instruction:
        assert name in self.code_options["co_varnames"], f"{name} missing"
        return create_instruction("STORE_FAST", argval=name)

    def create_store_deref(self, name: str) -> Instruction:
        assert name in self.cell_and_freevars()
        return create_instruction("STORE_DEREF", argval=name)

    def create_load_global(self, name: str, add: bool = False) -> Instruction:
        if add:
            self.tx.output.update_co_names(name)
        assert name in self.code_options["co_names"], f"{name} not in co_names"
        return create_instruction("LOAD_GLOBAL", argval=name)

    def create_load_const(self, value: Any) -> Instruction:
        return create_load_const(value)

    def create_load_const_unchecked(self, value: Any) -> Instruction:
        return create_load_const(value, checked=False)

    def load_method(self, name: str) -> None:
        self.tx.output.update_co_names(name)
        self.append_output(create_load_method(name))

    def call_method(self, nargs: int) -> None:
        self.extend_output(create_call_method(nargs))

    def create_load_attr(self, name: str) -> Instruction:
        if name not in self.code_options["co_names"]:
            self.code_options["co_names"] += (name,)
        return create_instruction("LOAD_ATTR", argval=name)

    def load_attr(self, name: str) -> None:
        self.append_output(self.create_load_attr(name))

    def create_load_attrs(self, names: str) -> list[Instruction]:
        return [self.create_load_attr(name) for name in names.split(".")]

    def create_store_attr(self, name: str) -> Instruction:
        if name not in self.code_options["co_names"]:
            self.code_options["co_names"] += (name,)
        return create_instruction("STORE_ATTR", argval=name)

    def store_attr(self, name: str) -> None:
        self.append_output(self.create_store_attr(name))

    def load_function_name(
        self, fn_name: str, push_null: bool, num_on_stack: int = 0
    ) -> list[Instruction]:
        """Load the global fn_name on the stack num_on_stack down"""
        output = []
        if push_null and sys.version_info >= (3, 11):
            output.extend(add_push_null(self.create_load_global(fn_name, add=True)))
            if num_on_stack > 0:
                output.extend(
                    [
                        *self.rot_n(num_on_stack + 2),
                        *self.rot_n(num_on_stack + 2),
                    ]
                )
        else:
            output.extend(
                [
                    self.create_load_global(fn_name, add=True),
                    *self.rot_n(num_on_stack + 1),
                ]
            )
        return output

    def rot_n(self, n: int) -> list[Instruction]:
        try:
            return create_rot_n(n)
        except AttributeError:
            # desired rotate bytecode doesn't exist, generate equivalent bytecode
            return [
                create_build_tuple(n),
                self.create_load_const_unchecked(rot_n_helper(n)),
                *create_rot_n(2),
                *create_call_function_ex(False, False),
                create_instruction("UNPACK_SEQUENCE", arg=n),
            ]

    def pop_null(self) -> list[Instruction]:
        # POP_TOP doesn't work for null, so we pop nulls by pushing in a
        # nop function, calling it (which consumes the null), and popping the result.
        assert sys.version_info >= (3, 11)
        return [
            self.create_load_const_unchecked(lambda: None),
            # 3.13 swapped NULL and callable
            *(
                (create_instruction("SWAP", arg=2),)
                if sys.version_info >= (3, 13)
                else ()
            ),
            *create_call_function(0, False),
            create_instruction("POP_TOP"),
        ]

    def pop_top(self) -> None:
        self.append_output(create_instruction("POP_TOP"))

    def call_function(self, nargs: int, push_null: bool) -> None:
        self.extend_output(create_call_function(nargs, push_null=push_null))

    def dup_top(self) -> None:
        self.append_output(create_dup_top())

    def store(self, varname: str) -> None:
        self.append_output(self.create_store(varname))

    def load_deref(self, varname: str) -> None:
        self.append_output(self.create_load_deref(varname))

    def make_function_with_closure(
        self,
        fn_name: str,
        code: types.CodeType,
    ) -> None:
        """Creates a closure with code object `code`.

        Expects the TOS to be the tuple of cells to use for this closure.
        TOS will be popped to create the closure.
        Args:
            - fn_name: name of the function
            - code: code object of the function
                (does not include the tuple of cells on the TOS)
        """
        output = self._output

        output.append(self.create_load_const(code))
        if sys.version_info < (3, 11):
            output.append(self.create_load_const(fn_name))
        if sys.version_info >= (3, 13):
            output.extend(
                [
                    create_instruction("MAKE_FUNCTION"),
                    create_instruction("SET_FUNCTION_ATTRIBUTE", arg=0x08),
                ]
            )
        else:
            output.append(create_instruction("MAKE_FUNCTION", arg=0x08))

        self.clear_tos()

    def create_load_python_module(self, mod: types.ModuleType) -> Instruction:
        """
        Generate a LOAD_GLOBAL instruction to fetch a given python module.
        """
        output = self.tx.output
        global_scope = output.global_scope
        name = re.sub(r"^.*[.]", "", mod.__name__)
        if global_scope.get(name, None) is mod:
            return self.create_load_global(name, add=True)
        prefix = f"___module_{name}"
        global_name = self.tx.output.install_global_by_id(prefix, mod)
        return self.create_load_global(global_name, add=True)

    def mark_source_temp(self, source: Source) -> None:
        """
        Mark a source as a temp variable, so that it can be reused.
        """
        if source not in self.tempvars:
            self.tempvars[source] = None

    def make_call_generated_code(self, fn_name: str) -> None:
        """Call the generated code function stored in fn_name"""
        self.extend_output(self.load_function_name(fn_name, True))

        graphargs = self.tx.output.graphargs

        def extract_nested_sources(source: Source) -> list[Source]:
            nested_sources: list[Source] = []
            if isinstance(source, ChainedSource):
                nested_sources.append(source.base)
            if isinstance(source, DictGetItemSource) and isinstance(
                source.index, Source
            ):
                nested_sources.append(source.index)
            return nested_sources

        def collect_temp_sources(sources: deque[Source], codegen: PyCodegen) -> None:
            seen_sources: OrderedSet[Source] = OrderedSet()
            while sources:
                current_source = sources.popleft()
                if current_source in seen_sources:
                    # This source is used at least twice, so it can be reused
                    codegen.mark_source_temp(current_source)
                    # Dont trace source further. This prevents us from marking too
                    # many nodes as temp sources.
                    continue
                seen_sources.add(current_source)
                sources.extend(extract_nested_sources(current_source))

        # Collect all the sources that are used more than once, so that we can
        # generate tmp variables in the generated pre-graph bytecode. This
        # essentially implements CSE.
        collect_temp_sources(
            deque([arg.source for arg in graphargs if arg.source is not None]), self
        )

        cm_var = None
        if config.record_runtime_overhead:
            # Record the pregraph bytecode start
            self.add_push_null(
                lambda: self.load_import_from(
                    utils.__name__, "record_pregraph_bytecode_enter"
                )
            )
            self.extend_output(create_call_function(0, False))
            cm_var = self.new_var()
            self.store(cm_var)

        for arg in graphargs:
            if arg.pass_arg_as_tensor:
                self.add_push_null(
                    lambda: self.extend_output(
                        [
                            self.create_load_python_module(torch),
                            self.create_load_attr("_as_tensor_fullprec"),
                        ]
                    )
                )
                self.call_reconstruct(arg)
                self.extend_output(create_call_function(1, False))
            else:
                self.call_reconstruct(arg)

        if config.record_runtime_overhead:
            # Record the pregraph bytecode end
            self.add_push_null(
                lambda: self.load_import_from(
                    utils.__name__, "record_pregraph_bytecode_exit"
                )
            )
            assert cm_var is not None
            self.extend_output([self.create_load(cm_var)])
            self.extend_output(create_call_function(1, False))
            self.pop_top()

        self.extend_output(create_call_function(len(graphargs), False))

    def create_import_name(self, module_name: str) -> Instruction:
        return create_instruction("IMPORT_NAME", argval=module_name)

    def load_import_from(self, module_name: str, object_name: str) -> None:
        source = AttrSource(self.tx.import_source(module_name), object_name)
        # Note: This approach is somewhat aggressive because typically, a source is marked
        # as a tempvar only when it is used more than once. In this case, we're marking it
        # as a tempvar without performing that analysis. However, this is a simple solution,
        # and in many cases, load imports are reused multiple times.
        self.mark_source_temp(source)
        self(source)

    def create_call_function_kw(
        self, nargs: int, kw_names: Iterable[str], push_null: bool
    ) -> list[Instruction]:
        if sys.version_info >= (3, 13):
            output = create_call_function(nargs, push_null)
            assert output[-1].opname == "CALL"
            output.insert(-1, self.create_load_const(kw_names))
            output[-1] = create_instruction("CALL_KW", arg=nargs)
            return output
        elif sys.version_info >= (3, 11):
            output = create_call_function(nargs, push_null)
            if sys.version_info >= (3, 12):
                idx = -1
                expected_inst = "CALL"
            else:
                idx = -2
                expected_inst = "PRECALL"
            assert output[idx].opname == expected_inst
            kw_names_inst = create_instruction("KW_NAMES", argval=kw_names)
            output.insert(idx, kw_names_inst)
            return output
        return [
            self.create_load_const(kw_names),
            create_instruction("CALL_FUNCTION_KW", arg=nargs),
        ]

    def create_delete(self, value: object) -> Instruction:
        return create_instruction("DELETE_FAST", argval=value)