rocm_jax/jaxlib/mhlo_helpers.py
Peter Hawkins 22cd50535b Reapply: Use input-output aliasing for jaxlib GPU custom calls.
Previously we had no way to tell XLA that inputs and outputs of GPU custom calls must alias. This now works in XLA:GPU so we can just ask XLA to enforce the aliasing we need.

It turns out some users are relying on the API contract of the custom calls within serialized HLO remaining stable. For the moment, we reapply only the Python changes. The C++ code is already tolerant of both aliased and unaliased outputs, and this gets us all the benefit of saving a copy. We can break backwards compatibility on the serialized HLO after users upgrade their saved HLO to the aliased version.

PiperOrigin-RevId: 480134780
2022-10-10 11:29:18 -07:00

79 lines
2.8 KiB
Python

# Copyright 2022 The JAX Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Helpers for building MHLO operators
from typing import Dict, Optional, Sequence, Union
import jaxlib.mlir.ir as ir
import jaxlib.mlir.dialects.mhlo as mhlo
import numpy as np
def custom_call(
call_target_name: str,
out_types: Sequence[ir.Type],
operands: Sequence[ir.Value],
operand_layouts: Sequence[Sequence[int]],
result_layouts: Sequence[Sequence[int]],
backend_config: Optional[str] = None,
has_side_effect: bool = False,
api_version: int = 2,
operand_output_aliases: Dict[int, int] = {},
) -> Union[ir.Value, Sequence[ir.Value]]:
"""Less-verbose helper for building an MHLO custom call op.
Once https://github.com/llvm/llvm-project/issues/54932 is fixed, this helper
may be able to go away.
Args:
...
operand_output_alias: a dictionary mapping input numbers -> output numbers
that must alias.
"""
i32_type = ir.IntegerType.get_signless(32)
out = mhlo.CustomCallOp(
(out_types
if len(out_types) == 1 else [ir.TupleType.get_tuple(out_types)]),
operands,
call_target_name=ir.StringAttr.get(call_target_name),
has_side_effect=ir.BoolAttr.get(has_side_effect),
backend_config=ir.StringAttr.get(
"" if backend_config is None else backend_config),
api_version=ir.IntegerAttr.get(i32_type, api_version),
called_computations=ir.ArrayAttr.get([]),
operand_layouts=ir.ArrayAttr.get([
ir.DenseIntElementsAttr.get(
np.atleast_1d(np.asarray(l, dtype=np.int64)),
type=ir.IndexType.get()) for l in operand_layouts
]),
result_layouts=ir.ArrayAttr.get([
ir.DenseIntElementsAttr.get(
np.atleast_1d(np.asarray(l, dtype=np.int64)),
type=ir.IndexType.get()) for l in result_layouts
]),
output_operand_aliases=ir.ArrayAttr.get([
mhlo.OutputOperandAlias.get(
output_tuple_indices=[] if len(out_types) == 1 else [output],
operand_index=input,
operand_tuple_indices=[])
for input, output in operand_output_aliases.items()
]))
if len(out_types) == 1:
return out.result
else:
return [
mhlo.GetTupleElementOp(out, ir.IntegerAttr.get(i32_type, i)).result
for i in range(len(out_types))
]