Use torch.Tag.pointwise to auto-discover permutable elementwise ops (#19457)

[mcremon-meta]

Summary:

Instead of manually listing each elementwise op in RemovePermutesAroundElementwiseOps.permutable_ops, use the torch.Tag.pointwise tag to automatically accept any ATen op tagged as pointwise. This makes the pass forward-compatible with new elementwise ops added to PyTorch without requiring manual updates.

A new static method _is_pointwise(target) inspects the op's tags at runtime and is used as a fallback in both is_node_permutable and the main subgraph-discovery loop.

The explicit permutable_ops set is retained for:

• Non-pointwise ops that need special dimension-argument handling (cat, mean, sum, slice_copy)
• quantize_per_tensor/dequantize_per_tensor ops (not part of ATen)

Differential Revision: D104612850

[pytorch-bot]

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❌ 3 New Failures, 1 Pending, 4 Unrelated Failures

As of commit 24dc09f with merge base f1062a7 ():

NEW FAILURES - The following jobs have failed:

• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t eceaffbb37311b2b8259d8018692f217a8b6b6fb02475350a060f33054d46c4c /exec failed with exit code 139
• pull / unittest / macos / macos-job (gh)
  exir/emit/test/test_emit.py::TestEmit::test_delegate_deduplicate
• pull / unittest-editable / macos / macos-job (gh)
  exir/tests/test_memory_planning.py::TestMisc::test_multiple_pools_1

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)
  exir/tests/test_joint_graph.py::TestJointGraph::test_joint_graph
• pull / unittest / windows / windows-job (gh) (trunk failure)
  exir/tests/test_joint_graph.py::TestJointGraph::test_joint_graph
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
  exir/tests/test_joint_graph.py::TestJointGraph::test_joint_graph
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  exir/tests/test_joint_graph.py::TestJointGraph::test_joint_graph

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[meta-codesync]

@mcremon-meta has exported this pull request. If you are a Meta employee, you can view the originating Diff in D104612850.

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[mcremon-meta]

cc @AdrianLundell, I don't anticipate any required changes for Arm's flow, the pass should just be able to catch more cases!

[AdrianLundell]

Great work! This could probably be used in the view-fusing pass as well if you feel like adding that at the same time.