Reorder slice before permute

[DrJessop]

Summary:
Move slice_copy ops before permute_copy to reduce permute data volume when profitable. Only transforms single-user permutes.

Cost model: dim-0 slices are nop-eligible after MakeSliceAndCatDimOutermostPass. Moving such a slice loses the nop, so we only move it when the slice removes more than half the data (permute savings outweigh the nop loss). Non-dim-0 slices have no nop opportunity, so any permute savings is pure win.

Not added to CadenceReorderOpsInGraph to avoid interaction with MakeSliceAndCatDimOutermostPass in the default pipeline.

Differential Revision: D102426699

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19129

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• Rolling out OSDC (ARC) runners on pull & trunk workflows in PyTorch main

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

As of commit 2d228fc with merge base 0a43e2f ():

NEW FAILURE - The following job has failed:

• pull / unittest-editable / macos / macos-job (gh)
  extension/pybindings/test/test_pybindings.py::PybindingsTest::test_program_data_separation

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

• periodic (gh)
• pull / unittest / macos / macos-job (gh)
  ##[error]The operation was canceled.

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 / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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

[meta-codesync]

@DrJessop has exported this pull request. If you are a Meta employee, you can view the originating Diff in D102426699.

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.