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zingozingo
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Arm backend: Fix cycle timestamp conversion in ETDump Chrome traces (pytorch#24792)
### Summary Require a positive finite clock frequency for cycle timestamps. Convert start times and duration from cycles to microseconds when generating Chrome traces. ### Test plan Add Buck dependencies and visibility for the conversion test. Signed-off-by: Zingo Andersen <Zingo.Andersen@arm.com>
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5 files changed

Lines changed: 156 additions & 7 deletions

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‎backends/arm/scripts/BUCK‎

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# Copyright 2026 Arm Limited and/or its affiliates.
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#
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# This source code is licensed under the BSD-style license found in the
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# LICENSE file in the root directory of this source tree.
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load("@fbcode_macros//build_defs:build_file_migration.bzl", "fbcode_target")
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load("@fbsource//xplat/executorch/build:runtime_wrapper.bzl", "runtime")
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oncall("executorch")
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fbcode_target(
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_kind = runtime.python_library,
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name = "etdump_to_chrome_trace",
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srcs = ["etdump_to_chrome_trace.py"],
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deps = ["//executorch/devtools:lib"],
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)

‎backends/arm/scripts/etdump_to_chrome_trace.py‎

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@@ -21,6 +21,7 @@
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import argparse
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import json
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import math
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from executorch.devtools import Inspector
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from executorch.devtools.inspector import TimeScale
@@ -36,13 +37,26 @@ def main() -> None:
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default="ns",
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choices=[ts.value for ts in TimeScale],
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)
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parser.add_argument(
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"--clock_frequency_hz",
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type=float,
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help="Clock frequency used for timestamps when --source_time_scale=cycles.",
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)
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args = parser.parse_args()
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cycle_timestamps = args.source_time_scale == "cycles"
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if cycle_timestamps and (
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args.clock_frequency_hz is None
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or not math.isfinite(args.clock_frequency_hz)
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or args.clock_frequency_hz <= 0
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):
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parser.error("Cycle timestamps require a positive finite --clock_frequency_hz")
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inspector = Inspector(
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etdump_path=args.etdump_path,
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etrecord=args.etrecord_path,
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source_time_scale=TimeScale(args.source_time_scale),
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target_time_scale=TimeScale.US,
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target_time_scale=TimeScale.CYCLES if cycle_timestamps else TimeScale.US,
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)
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trace_events = []
@@ -53,9 +67,11 @@ def main() -> None:
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"us": 1.0,
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"ms": 1000.0,
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"s": 1000_000.0,
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"cycles": 1.0,
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"cycles": 1_000_000.0 / args.clock_frequency_hz if cycle_timestamps else 1.0,
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}[args.source_time_scale]
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duration_to_us = source_to_us if cycle_timestamps else 1.0
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for block_idx, event_block in enumerate(inspector.event_blocks):
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tid_name = event_block.name
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@@ -73,19 +89,19 @@ def main() -> None:
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if event.perf_data is None or event.start_time is None:
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continue
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76-
durations_us = event.perf_data.raw
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durations = event.perf_data.raw
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start_times = event.start_time
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79-
for iter_idx, (start_time, duration_us) in enumerate(
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zip(start_times, durations_us)
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for iter_idx, (start_time, duration) in enumerate(
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zip(start_times, durations)
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):
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trace_events.append(
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{
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"name": event.name,
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"cat": event_block.name,
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"ph": "X",
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"ts": float(start_time) * source_to_us,
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"dur": float(duration_us),
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"dur": float(duration) * duration_to_us,
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"pid": 1,
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"tid": block_idx,
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"args": {

‎backends/arm/test/misc/test_etdump_to_chrome_trace.py‎

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# Copyright 2026 Arm Limited and/or its affiliates.
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#
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# This source code is licensed under the BSD-style license found in the
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# LICENSE file in the root directory of this source tree.
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import json
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import struct
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import sys
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import pytest
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from executorch.backends.arm.scripts import etdump_to_chrome_trace
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from executorch.devtools.etdump import schema_flatcc as flatcc
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from executorch.devtools.etdump.serialize import serialize_to_etdump_flatcc
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@pytest.fixture
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def etdump_path(tmp_path):
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event = flatcc.ProfileEvent(
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name="op",
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chain_index=0,
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instruction_id=0,
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delegate_debug_id_int=-1,
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delegate_debug_id_str="",
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delegate_debug_metadata=b"",
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start_time=1000,
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end_time=1500,
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)
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dump = flatcc.ETDumpFlatCC(
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version=0,
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run_data=[
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flatcc.RunData(
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name="Execute",
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bundled_input_index=-1,
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allocators=[],
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events=[
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flatcc.Event(
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profile_event=event, allocation_event=None, debug_event=None
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)
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],
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)
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],
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)
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path = tmp_path / "etdump.bin"
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data = serialize_to_etdump_flatcc(dump)
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path.write_bytes(struct.pack("<I", len(data)) + data)
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return path
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@pytest.mark.parametrize(
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"scale,frequency,timestamp,duration",
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[
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("cycles", "500000000", 2.0, 1.0),
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("cycles", "1000000000", 1.0, 0.5),
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("ns", None, 1.0, 0.5),
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("us", None, 1000.0, 500.0),
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("ms", None, 1000000.0, 500000.0),
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("s", None, 1000000000.0, 500000000.0),
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],
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)
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def test_trace_uses_microseconds(
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monkeypatch, tmp_path, etdump_path, scale, frequency, timestamp, duration
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):
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output = tmp_path / "trace.json"
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command = [
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"etdump_to_chrome_trace",
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"--etdump_path",
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str(etdump_path),
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"--output",
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str(output),
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"--source_time_scale",
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scale,
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]
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if frequency is not None:
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command += ["--clock_frequency_hz", frequency]
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monkeypatch.setattr(sys, "argv", command)
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etdump_to_chrome_trace.main()
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events = json.loads(output.read_text())["traceEvents"]
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event = next(event for event in events if event["ph"] == "X")
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assert event["ts"] == pytest.approx(timestamp)
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assert event["dur"] == pytest.approx(duration)
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@pytest.mark.parametrize("frequency", [None, "0", "-1", "nan", "inf"])
87+
def test_cycle_trace_requires_valid_frequency(monkeypatch, tmp_path, frequency, capsys):
88+
command = [
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"etdump_to_chrome_trace",
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"--etdump_path",
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str(tmp_path / "missing.bin"),
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"--output",
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str(tmp_path / "trace.json"),
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"--source_time_scale",
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"cycles",
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]
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if frequency is not None:
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command += ["--clock_frequency_hz", frequency]
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monkeypatch.setattr(sys, "argv", command)
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101+
with pytest.raises(SystemExit) as error:
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etdump_to_chrome_trace.main()
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assert error.value.code == 2
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assert "positive finite --clock_frequency_hz" in capsys.readouterr().err

‎backends/arm/test/targets.bzl‎

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@@ -128,6 +128,7 @@ def define_arm_tests():
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if runtime.is_oss:
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test_files += [
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"misc/test_docgen_op_support.py",
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"misc/test_etdump_to_chrome_trace.py",
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"misc/test_public_api_manifest.py",
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"misc/test_validate_public_api_manifest.py",
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]
@@ -168,7 +169,11 @@ def define_arm_tests():
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]),
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deps = ([] if runtime.is_oss or not _ENABLE_VGF else [
170171
"//executorch/backends/arm/test:model_converter_resource",
171-
]) + [
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]) + ([
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"//executorch/backends/arm/scripts:etdump_to_chrome_trace",
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"//executorch/devtools/etdump:schema_flatcc",
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"//executorch/devtools/etdump:serialize",
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] if test_name == "etdump_to_chrome_trace" else []) + [
172177
"//executorch/backends/arm/test:arm_tester" if runtime.is_oss else "//executorch/backends/arm/test/tester/fb:arm_tester_fb",
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"//executorch/backends/arm/test:conftest",
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"//executorch/backends/arm/test:mxfp_test_common",

‎devtools/etdump/BUCK‎

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# Copyright 2026 Arm Limited and/or its affiliates.
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#
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# This source code is licensed under the BSD-style license found in the
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# LICENSE file in the root directory of this source tree.
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load("@fbcode_macros//build_defs:build_file_migration.bzl", "fbcode_target", "non_fbcode_target")
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load(":targets.bzl", "define_common_targets")
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@@ -19,6 +24,7 @@ fbcode_target(_kind = runtime.python_library,
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"schema_flatcc.py",
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],
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visibility = [
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"//executorch/backends/arm/test:etdump_to_chrome_trace",
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"//executorch/devtools/...",
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],
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deps = [
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"//executorch/schema:scalar_type.fbs": "scalar_type.fbs",
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},
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visibility = [
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"//executorch/backends/arm/test:etdump_to_chrome_trace",
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"//executorch/devtools/...",
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"//executorch/runtime/test/...",
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],

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