[SS-JIA]

Summary:

Ulterior Motive

Restore the "Test WebGPU Native (Dawn)" workflow on main, which has failed on every commit since "[Vulkan] Keep unrepresentable and symbolic scalars out of the delegate (#23247)".

Rationale

What: The Vulkan partitioner no longer applies its SymBool/SymFloat rejection to assert ops (_assert_scalar, sym_constrain_range_for_size) or to nodes whose only users are assert ops.

Why: #23247 rejects every node that produces or consumes a SymBool. Models that guard an .item() value with torch._check produce u <= N / u >= 0 comparisons feeding _assert_scalar. Rejecting them cascades through the new "symbolic scalar has an unsupported consumer" check to the _local_scalar_dense producer, splitting the graph into multiple delegates. test_rope_hf.py then fails with AssertionError: expected one delegate, got 2. Asserts are stripped by RemoveAssertsTransform during preprocessing, so these SymBool values never need a runtime representation.

Details

• Assert-only SymBool chains
  • Before: Comparisons and asserts rejected; .item() producer rejected as a consequence; graph split into multiple delegates.
  • After: Delegated, then removed during preprocessing; graph stays in one delegate.
• SymBool/SymFloat values feeding non-assert ops
  • Before: Rejected.
  • After: Unchanged (still rejected).

Test Plan:

Observed Results

Validation	Device	Result
Vulkan partition count for DynamicHfRope (test_rope_hf.py), parent commit	macOS (Apple Silicon) host, partitioner only	2 partitions; skip logs match the CI failure
Vulkan partition count for DynamicHfRope, this commit	macOS (Apple Silicon) host, partitioner only	1 partition, no skipped nodes
test_rope_hf.py end-to-end ("Test WebGPU Native (Dawn)")	—	Not run: needs the Dawn/SwiftShader runtime; relying on CI
backends/vulkan/test/test_vulkan_dynamic.py	—	Not run: needs the Vulkan runtime; relying on CI
Lint	—	Not run: lint tooling not installed locally; relying on CI

Reproduction Guide

Setup

git clone https://github.com/pytorch/executorch.git
cd executorch
./install_executorch.sh

Count Vulkan partitions for the dynamic HF RoPE model

cat > /tmp/count_partitions.py <<'PY'
import torch
from executorch.exir import to_edge
from executorch.backends.vulkan.partitioner.vulkan_partitioner import VulkanPartitioner
from executorch.backends.webgpu.test.ops import test_rope_hf as t

inputs = t._dynamic_inputs()
with torch._dynamo.config.patch(capture_scalar_outputs=True):
    ep = torch.export.export(t.DynamicHfRope().eval(), inputs)
res = VulkanPartitioner().partition(to_edge(ep).exported_program())
tags = {
    n.meta["delegation_tag"]
    for n in res.tagged_exported_program.graph.nodes
    if n.meta.get("delegation_tag")
}
print("partitions:", len(tags))
PY
python /tmp/count_partitions.py 2>&1 | grep -E "Vulkan Partitioner|partitions:"

Run once on this commit (expect partitions: 1) and once on its parent (git checkout HEAD~1, expect partitions: 2 plus "symbolic float or bool values are not supported" skip logs).

Reviewers:

This PR was authored with Claude Code.

cc @manuelcandales @digantdesai @cbilgin

[pytorch-bot]

🔗 Helpful Links

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❌ 1 New Failure

As of commit 115aac7 with merge base 9cced90 ():

NEW FAILURE - The following job has failed:

• pull / unittest-editable / windows / windows-job (gh)
  [ FAILED ] OpRandnTest.Rank

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