Transforms: share the permute/view propagation driver

[rascani]

Move the propagation algorithm itself to backends/transforms, leaving the TOSA
configuration behind in the Arm backend. The Arm file is now 107 lines: the
overrides mixin, and two subclasses that combine it with ArmPass and the shared
Up and Down passes.

The split is possible because the extension points landed first. The algorithm
asks whether a node is transparent, whether an elementwise op carries extra
non-layout inputs, whether a user blocks crossing, whether to propagate at all,
which region-cancellation engine to fuse with, and which duplicate users must
not be collapsed. Arm answers all six; the shared defaults are neutral, so a
backend that answers none still gets a working mover.

Class names are unchanged on the Arm side, so arm_pass_manager and the existing
tests are untouched. Method resolution puts the TOSA overrides ahead of the
shared implementation and ArmPass last, which is what the previous single-file
arrangement did implicitly.

Cortex-M can now use this instead of growing its own fixed-point loop, which is
the point of the exercise: on the shared 36-case matrix this driver reaches 82
permutes where that loop stalls at 156.

No behaviour change: the Arm pass suite produces a failure set identical to
merge base, name for name.

Authored with Claude Code.

[rascani]

Stack from ghstack (oldest at bottom):

• Transforms: let a backend declare what counts as a permute #22125
• Transforms: stop fork splitting from stranding a permute #22124
• -> Transforms: share the permute/view propagation driver #22123
• Transforms: share the horizontal fusion passes #22122
• Transforms: share the view/permute canonicalizer #22121
• Arm backend: give the propagation pass backend extension points #22120
• Transforms: share the view/permute algebra with all backends #22119

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/22123

• 📄 Preview Python docs built from this PR

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

❌ 9 New Failures

As of commit 8596697 with merge base e831b3e ():

NEW FAILURES - The following jobs have failed:

• pull / test-arm-backend-no-driver (test_pytest_models_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 71beb37448c9b4adbb93f19fafbe98b2ebc6ea00f81485e2fa4dd5639e538034 /exec failed with exit code 1
• pull / test-arm-backend-no-driver (test_pytest_ops_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 06e35b919e0918ab04550eeb05f81abd4d3197a7b400aefec049ee277a496f30 /exec failed with exit code 1
• pull / unittest-buck / linux / linux-job (gh)
  RuntimeError: Command docker exec -t bddfc7c93d46349ab355cfe4da951b3688ec3da908dcb2c60c1f8af6bf3b5b9e /exec failed with exit code 3
• pull / unittest-buck / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 3
• trunk / test-arm-backend-ethos-u (test_model_smollm2_135M_ethos_u85) / linux-job (gh)
  RuntimeError: Command docker exec -t 451cdb7a01da8834d7f1ba5dc4eec7c8f98dd591f17e2b0ddb2ba580705e4eea /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 50e8c06e2438afd93de0837aa1b42f6769cc9c0b143397860297e3d6e5582f9a /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 2ab3b227719c6956b86c37d50f8342f44a38d46e53946be5fce8da9b29c04c59 /exec failed with exit code 1
• trunk / test-arm-backend-vkml (test_pytest_models_vkml) / linux-job (gh)
  RuntimeError: Command docker exec -t 615d138af044bc2e8dbf05bc194d68c7e270703a24106d0a24601f9829dba1e0 /exec failed with exit code 1
• trunk / test-arm-backend-vkml (test_pytest_ops_vkml) / linux-job (gh)
  RuntimeError: Command docker exec -t 16a2b284c34259fb9e4fa286759eaf1df266f9abeba842349145f35bbade7663 /exec failed with exit code 1

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