[ExecuTorch][WebGPU] permute_copy op test suite (cases.py op-test framework)

Pull Request resolved: #20397

Registers `aten.permute_copy.default` in the `cases.py` op-test framework: a `_permute_suite` of 4 configs (3D rotation, 4D middle-dim transpose, 2D transpose, full 4D shuffle) that `generate_op_tests` exports via `VulkanPartitioner` and compares to a torch golden on Dawn. Also adds `test/ops/permute/test_permute.py` (`PermuteModule` + `CONFIGS` + `_op_delegated` smoke test) and the `aten.permute_copy.default` partitioner-allowlist entry in `tester.py`.
ghstack-source-id: 397026550
@exported-using-ghexport

Differential Revision: [D108793156](https://our.internmc.facebook.com/intern/diff/D108793156/)

Author: JCNTH

backends/webgpu/test/op_tests/cases.py

@@ -40,6 +40,10 @@
     CONFIGS as _MUL_CONFIGS,
     MulModule,
 )
+from executorch.backends.webgpu.test.ops.test_permute import (
+    CONFIGS as _PERMUTE_CONFIGS,
+    PermuteModule,
+)
 from executorch.backends.webgpu.test.ops.test_select import (
     CONFIGS as _SELECT_CONFIGS,
     SelectModule,
@@ -230,3 +234,16 @@ def _unsqueeze_suite() -> WebGPUTestSuite:
 @register_op_test("slice")
 def _slice_suite() -> WebGPUTestSuite:
     return _fn_config_suite(SliceModule, _SLICE_CONFIGS)
+
+
+@register_op_test("permute")
+def _permute_suite() -> WebGPUTestSuite:
+    # CONFIGS: name -> (shape, perm-tuple).
+    return WebGPUTestSuite(
+        module_factory=lambda perm: PermuteModule(perm),
+        cases=[
+            Case(name=n, construct={"perm": perm}, inputs=(shape,))
+            for n, (shape, perm) in _PERMUTE_CONFIGS.items()
+        ],
+        golden_dtype="float32",  # permutation reorders values; fp64 bit-identical
+    )

backends/webgpu/test/ops/test_permute.py

@@ -0,0 +1,76 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+"""`aten.permute_copy.default` module + configs for the WebGPU op-test framework.
+
+`PermuteModule` + `CONFIGS` are imported by `cases.py` to drive the declarative
+op-test suite. `PermuteTest` is the export-delegation smoke
+test.
+"""
+
+import unittest
+
+import torch
+
+from executorch.backends.vulkan.partitioner.vulkan_partitioner import VulkanPartitioner
+from executorch.exir import to_edge_transform_and_lower
+
+# name -> (input_shape, perm)
+CONFIGS = {
+    "rot3d": ((2, 3, 4), (2, 0, 1)),
+    "mid4d": ((1, 8, 4, 16), (0, 2, 1, 3)),
+    "t2d": ((3, 5), (1, 0)),
+    "shuffle4d": ((2, 3, 4, 5), (3, 1, 0, 2)),
+}
+
+
+class PermuteModule(torch.nn.Module):
+    def __init__(self, perm):
+        super().__init__()
+        self.perm = perm
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        return torch.permute(x, self.perm).contiguous()
+
+
+def _det_input(shape):
+    g = torch.Generator().manual_seed(0)
+    return torch.randn(*shape, generator=g, dtype=torch.float32)
+
+
+def _lower(perm, x: torch.Tensor):
+    ep = torch.export.export(PermuteModule(perm).eval(), (x,))
+    return to_edge_transform_and_lower(ep, partitioner=[VulkanPartitioner()])
+
+
+def _delegated(et) -> bool:
+    return any(
+        d.id == "VulkanBackend"
+        for plan in et.executorch_program.execution_plan
+        for d in plan.delegates
+    )
+
+
+def _op_delegated(edge, op_substr: str) -> bool:
+    # op must be absorbed into the delegate, not left as a top-level CPU-fallback node.
+    gm = edge.exported_program().graph_module
+    return all(op_substr not in str(getattr(n, "target", "")) for n in gm.graph.nodes)
+
+
+class PermuteTest(unittest.TestCase):
+    def test_export_delegates(self) -> None:
+        for name, (shape, perm) in CONFIGS.items():
+            with self.subTest(name=name):
+                edge = _lower(perm, _det_input(shape))
+                et = edge.to_executorch()
+                self.assertTrue(
+                    _delegated(et),
+                    f"Expected a VulkanBackend delegate (permute {name})",
+                )
+                self.assertTrue(
+                    _op_delegated(edge, "permute"),
+                    f"permute not delegated (fell back to CPU) for {name}",
+                )

backends/webgpu/test/tester.py

@@ -28,6 +28,7 @@
     exir_ops.edge.aten.squeeze_copy.dims,
     exir_ops.edge.aten.unsqueeze_copy.default,
     exir_ops.edge.aten.slice_copy.Tensor,
+    exir_ops.edge.aten.permute_copy.default,
 ]