Arm backend: Enable int16 rsqrt on Ethos-U55/U85

[3l1]

Summary:
Fix Rsqrt op for int16
Add unit tests

Differential Revision: D83802158

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 18 New Failures, 3 Unrelated Failures

As of commit e4569d6 with merge base 331d771 ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
  >>> Lint for backends/arm/test/ops/test_rsqrt.py:
• pull / unittest-arm-backend-with-no-fvp (test_pytest_ops) / linux-job (gh)
  RuntimeError: Command docker exec -t 9829e722ac980daaa78926d56924c091bb855e6b66e1fe872995b6b9e1d6f01b /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 1b7d698643fdcb93039c25c8e14db7ff6a1ccff8e8c1a7d73b8825809bd3267e /exec failed with exit code 1
• trunk / test-arm-backend (test_pytest_ops_ethosu_fvp) / linux-job (gh)
  RuntimeError: Command docker exec -t 181be06505f71d2fcebc6c01e0e3cb32bf970b4f6a7a2b664f2a72777d8f974b /exec failed with exit code 1
• trunk / test-huggingface-transformers-macos (bert|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-macos (distilbert|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-macos (llama3.2-1b|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-macos (olmo-1b|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-macos (qwen3-0.6b|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-macos (smollm2-135m|coreml_fp32_gpu|--quantize) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (gemma3-1b|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t a18757b827b3a844da9424e842b6dd79139fe106d74c01b5e997fd358e4ee5e9 /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (llama3.2-1b|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t fcaad72674b00fe919c6d36d604dc0da8a4c1bd0980c85525bbeb1d94923f8bd /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (phi4-mini|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t 9b6e07e65db9e2d82a7e33b25b754cbd325e9065bfc35259a1ee45dccbcbacef /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (qwen3-0.6b|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t e5d84aea67c729c1a2901051b42476b706531b928ef69ba22287ef8f548ea952 /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (qwen3-1.7b|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t 8777f7fad75f7cd151ab3c57209726cd998ee666980c010291dcab755e433b18 /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (smollm2-135m|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t af5b67c92ca35be4451805cdb3b7b554c3d9aa773daddba71bd0a045f3e8b55f /exec failed with exit code 127
• trunk / test-huggingface-transformers-xnnpack (smollm3-3b|xnnpack|--quantize) / linux-job (gh)
  RuntimeError: Command docker exec -t 1888d4949691ad04b93f68317f8ba8f2f21c951a26d38bca4ca7ef6d8e71b7b7 /exec failed with exit code 127
• trunk / test-multimodal-macos (gemma3-4b) / macos-job (gh)
  RuntimeError: Command bash /Users/runner/work/_temp/exec_script failed with exit code 127

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)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
• trunk / unittest-release / linux / linux-job (gh) (trunk failure)

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[facebook-github-bot]

@3l1 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D83802158.

[3l1]

@pytorchbot label "release notes: none"

[digantdesai]

Enable just the tests?

[meta-codesync]

@3l1 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D83802158.

[zingo]

I see this errors
pull / unittest-arm-backend-with-no-fvp (test_pytest_ops) / linux-job (pull_request)

FAILED backends/arm/test/ops/test_rsqrt.py::test_rsqrt_int16_tosa_INT[rand_4d_1]
FAILED backends/arm/test/ops/test_rsqrt.py::test_rsqrt_int16_tosa_INT[rand_4d_2]

@3l1 could they be caused by the PR?
As they will break the CI they need to be addressed before merging.

[zingo]

Replaced by #15631