Decompose sigmoid to exp+reciprocal to fix U85 TABLE bug (#19618)

[christine-long-meta]

Summary:

Add DecomposeSigmoidPass that decomposes sigmoid(x) into reciprocal(add(exp(neg(x)), 1)).
This bypasses the broken Vela U85 sigmoid TABLE op by decomposing into
primitive ops whose individual TABLE implementations work correctly on U85.

The pass runs in both the TFA pipeline (before quantization, so exp/reciprocal get
individually annotated for a16w8) and the TOSA pipeline (for FP path).

Differential Revision: D105021646

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19618

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❌ 5 New Failures, 2 Cancelled Jobs, 1 Unrelated Failure

As of commit b5c3f62 with merge base dbcf6ac ():

NEW FAILURES - The following jobs have failed:

• Cadence Build & Test / cpu-test / test-ops / test-ops (gh)
  RuntimeError: Command docker exec -t 586916c99f50b5665c36a0c2a8bc3b9d566dac4cde1ef90f5a819f4d05b6694b /exec failed with exit code 1
• pull / test-arm-backend-no-driver (test_pytest_ops_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t d5d326e418a3aae06545675b8faa3ced9e6b9726fa95ccd81058e0a9b4a6ff5f /exec failed with exit code 1
• trunk / test-arm-backend-ethos-u (test_pytest_ops_ethos_u55) / linux-job (gh)
  RuntimeError: Command docker exec -t b9a249f5e27d5dc2f31294f79d3fdba6f5cd75235646b4243ff09a201c1e2ef8 /exec failed with exit code 1
• trunk / test-arm-backend-ethos-u (test_pytest_ops_ethos_u85) / linux-job (gh)
  RuntimeError: Command docker exec -t 83c494db0ec28c02964b9fd000de32087a965f34bfaee71fb0ce884710d6a6fd /exec failed with exit code 1
• trunk / test-arm-backend-vkml (test_pytest_ops_vkml) / linux-job (gh)
  RuntimeError: Command docker exec -t f5895ce1da69766a1d1dfc55dcabe77d7a8d93fed65af685ba58422eda3ad676 /exec failed with exit code 1

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• pull / unittest / macos / macos-job (gh)
• pull / unittest-editable / macos / macos-job (gh)

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

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

• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[meta-codesync]

@christine-long-meta has exported this pull request. If you are a Meta employee, you can view the originating Diff in D105021646.

[github-actions]

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[oscarandersson8218]

Thanks for your contribution @christine-long-meta! This PR seems a bit incomplete as it only modifies tests while the description suggest that there should be changes to passes. Does the PR currently include all the changes you want to make?

[christine-long-meta]

Thanks for your contribution @christine-long-meta! This PR seems a bit incomplete as it only modifies tests while the description suggest that there should be changes to passes. Does the PR currently include all the changes you want to make?

@oscarandersson8218 thanks for catching that. I guess the export function went wrong and only exported half. Let me try to fix that