Cortex_M backend: Add conv op

[AdrianLundell]

Currently only support for NHWC memory format.
Adds weights-per-tensor quantization as default quantization.

Generalizes the CortexMPassManager to work with any pass with exported_program as init arg to support using both XNNPackPasses and ArmPasses.

Refactors the QuantizedLinearFusionPass to become a more general CovertToCortexMPass for replacing Aten ops with corresponding Cortex-M ops.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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✅ You can merge normally! (2 Unrelated Failures)

As of commit 5e56eb0 with merge base 3374ff8 ():

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / linux / linux-job (gh) (trunk failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module

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[zingo]

Nice, just make sure all Arm tests pass before merge I see some fail but might just be flakey and a retest or rebase might help (I have not checked).

Edit: Seem to have failed in initial setup, re-trigger a test run now.

[AdrianLundell]

Unrelated failures

FAILED exir/backend/test/test_debug_handle_map.py::TestBackendDebugHandle::test_lowered_the_whole_model - UnboundLocalError: local variable 'qnn_compile_spec_buffer' referenced before assignment
Falsifying example: test_lowered_the_whole_model(
    self=<test_debug_handle_map.TestBackendDebugHandle testMethod=test_lowered_the_whole_model>,
    unlift=False,
)

You can reproduce this example by temporarily adding @reproduce_failure('6.84.2', b'AAA=') as a decorator on your test case
FAILED exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_lowered_backend_module - UnboundLocalError: local variable 'qnn_compile_spec_buffer' referenced before assignment
FAILED exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module - UnboundLocalError: local variable 'qnn_compile_spec_buffer' referenced before assignment

[zingo]

This might have caused some problems
I spot this in in the merged test suite in the hud on this commit:
https://hud.pytorch.org/hud/pytorch/executorch/main/1?per_page=50&name_filter=arm-backend
test: [failure] trunk / test-arm-backend (test_model_smollm2-135M) / linux-job

2025-11-20T12:16:32.2533021Z CALL: python3 -m examples.arm.aot_arm_compiler --delegate --model_name=smollm2 --target=ethos-u85-128 --output=arm_test/test_model/smollm2_arm_delegate_ethos-u85-128 --bundleio --system_config=Ethos_U85_SYS_DRAM_Mid --memory_mode=Dedicated_Sram_384KB --quantize --intermediate=arm_test/test_model/smollm2_arm_delegate_ethos-u85-128
2025-11-20T12:16:32.2534668Z Traceback (most recent call last):
2025-11-20T12:16:32.2535212Z   File "/opt/conda/envs/py_3.10/lib/python3.10/runpy.py", line 196, in _run_module_as_main
2025-11-20T12:16:32.2535809Z     return _run_code(code, main_globals, None,
2025-11-20T12:16:32.2536323Z   File "/opt/conda/envs/py_3.10/lib/python3.10/runpy.py", line 86, in _run_code
2025-11-20T12:16:32.2537110Z     exec(code, run_globals)
2025-11-20T12:16:32.2538043Z   File "/pytorch/executorch/examples/arm/aot_arm_compiler.py", line 38, in <module>
2025-11-20T12:16:32.2538808Z     from executorch.backends.cortex_m.passes.quantized_linear_fusion_pass import (
2025-11-20T12:16:32.2540048Z ModuleNotFoundError: No module named 'executorch.backends.cortex_m.passes.quantized_linear_fusion_pass'
2025-11-20T12:16:32.2542347Z ERROR called:  python3 -m examples.arm.aot_arm_compiler --delegate --model_name=smollm2 --target=ethos-u85-128 --output=arm_test/test_model/smollm2_arm_delegate_ethos-u85-128 --bundleio --system_config=Ethos_U85_SYS_DRAM_Mid --memory_mode=Dedicated_Sram_384KB --quantize --intermediate=arm_test/test_model/smollm2_arm_delegate_ethos-u85-128
2025-11-20T12:16:32.2543984Z Failed with: 1
2025-11-20T12:16:32.2556122Z ##[error]Process completed with exit code 1

[AdrianLundell]

This should be fixed with #15916