Qualcomm AI Engine Direct - Adding QNN backend support for reflection_pad1/2d core ATen ops

[qti-horodnic]

Summary

Added support for the aten ops reflection_pad1d and reflection_pad2d. Both ops use the QNN pad op using mode=reflect with a decomposition during to_edge and extra padding in the 2d case. The op_pad builder was extended to handle these ops.

Note that we cannot currently support reflection_pad3d easily, because the input rank for MIRROR_REFLECT is constrained to <5 for the QNN op. We can support it by decomposing the op into 2d slices, but that seems complicated and bug-prone, so I just added implementation for the 1d and 2d reflection_pad ops for now.

Test plan

python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNQuantizedOperator.test_qnn_backend_reflection_pad1d --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNFloatingPointOperator.test_qnn_backend_reflection_pad1d --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNQuantizedOperator.test_qnn_backend_reflection_pad2d --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNFloatingPointOperator.test_qnn_backend_reflection_pad2d --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android

Also ran the existing tests for the pad op to make sure nothing was broken with the existing implementation:

python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNQuantizedOperator.test_qnn_backend_pad --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNFloatingPointOperator.test_qnn_backend_pad --model SM8750 --host aisw-vm19-labsd --device abf5cb1 --build_folder build-android

[pytorch-bot]

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⏳ 33 Pending, 1 Unrelated Failure

As of commit 8b7a7bd with merge base 401ea8e ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-models-linux (resnet18, portable, linux.2xlarge) / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

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[qti-horodnic]

@pytorchbot label "release notes: qualcomm"

[abhinaykukkadapu]

Thanks for adding support.