torch-mlir/python/npcomp/compiler/pytorch/backend/frontend_lowering.py

113 lines
4.4 KiB
Python

# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
import os
import torch
from mlir.ir import *
from mlir.passmanager import *
from npcomp.compiler.utils import logging
__all__ = [
"lower_object_graph",
"lower_module",
]
# The set of passes that lowers from a TorchScript object graph representation
# to a module semantics where symbols correspond to dotted paths into the
# module.
OBJECT_GRAPH_LOWERING_PASSES = (
# Globalize the program. The rest of the compiler assumes a globalized
# program, which makes all analyses and transforms significantly easier
# to write.
"torch-globalize-pipeline",
# symbol-dce is currently needed for correctness, as we don't have a lowering
# in the backend for torch.global_slot's.
# Torch usually inserts a few unused global slots that are otherwise
# bothersome because we don't currently have a lowering for them.
# TODO: Support global slots in backends.
"symbol-dce",
# Incorporate user annotations and remove signature Python-isms.
"torch-adjust-calling-conventions",
)
TORCH_TO_TCP_PASSES = (
# Recognize ATen kernels.
"func(aten-recognize-kernels)",
# Convert the bulk of the program to ranked tensors with known dtype.
# This is the input to the backend layer that we are aiming for.
# First, unilaterally convert public functions to tensor.
# The way this pass is currently written, this implies that
# as pipeline authors, we are restricting our users to not be able to see
# updates to "out params" on their public functions.
# This is deemed ok for now.
"numpy-public-functions-to-tensor",
# Convert the bulk of non-ABI-visible arrays to tensors.
"func(numpy-array-to-tensor)",
# Do shape and dtype refinement.
# We could do it sooner, but the pass currently doesn't have transfer
# functions for array ops.
"func(torch-refine-types)",
# Propagate to ABI return types the shape/dtype information discovered by
# the previous pass. Doing this is ABI-compatible for our backends.
"numpy-refine-public-return",
# Clean up a few stray array/tensor conversion remnants.
"func(numpy-array-to-tensor)",
# Lower to TCP (+ guards) which is the input to codegen backends.
# Most of this should be subsumed by aten->linalg+guards conversions.
# (the guard generation will be automated from the linalg Op DSL)
"func(convert-aten-to-linalg)",
"func(convert-aten-to-tcf)",
"func(convert-tcf-to-std)",
"func(convert-elementwise-to-linalg)",
)
def lower_module(imported_module: Module):
"""Compiles an imported module, with a flat list of functions.
Args:
imported_module: The MLIR module consisting of funcs and globals in
the torch dialect. It is lowered in place.
Returns:
The imported_module, for convenience chaining methods.
"""
with imported_module.context as context:
if logging.debug_enabled():
logging.debug("Initial PyTorch IR:\n{}", imported_module)
# Frontend.
pipeline_str = ",".join(TORCH_TO_TCP_PASSES)
if logging.debug_enabled():
logging.debug("Running Torch->TCP pipeline '{}'", pipeline_str)
pm = PassManager.parse(pipeline_str)
pm.run(imported_module)
if logging.debug_enabled():
logging.debug("TCP IR:\n{}", imported_module)
return imported_module
def lower_object_graph(imported_module: Module):
"""Lowers an imported module that has TorchScript object graph semantics.
Args:
imported_module: The MLIR module consisting of IR as imported by the
torch_mlir.import_module. It is lowered in place.
Returns:
The imported_module, for convenience chaining methods.
"""
with imported_module.context as context:
if logging.debug_enabled():
logging.debug("Initial PyTorch object graph IR:\n{}", imported_module)
# Object graph lowering.
pipeline_str = ",".join(OBJECT_GRAPH_LOWERING_PASSES)
if logging.debug_enabled():
logging.debug(
"Running Torch object graph lowering pipeline '{}'", pipeline_str)
pm = PassManager.parse(pipeline_str)
pm.run(imported_module)
return lower_module(imported_module)