Reorder slice before binary broadcast ops (#19346)

[DrJessop]

Summary:

As titled. Drops unecessary computation. Helps DPEv26 by halving batch dim on a binary broadcast mul.

Reviewed By: ethansfng, mcremon-meta

Differential Revision: D103563327

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19346

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❌ 1 New Failure, 1 Unrelated Failure

As of commit 694d0a2 with merge base 76d941e ():

NEW FAILURE - The following job has failed:

• Docathon Labels Sync / check-labels (gh)
  Process completed with exit code 2.

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

• pull / test-quantized-aot-lib-linux / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

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[meta-codesync]

@DrJessop has exported this pull request. If you are a Meta employee, you can view the originating Diff in D103563327.

[github-actions]

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