Delegate even-kernel 'same'-padding convs via a quantized static pad (#20553)

[JakeStevens]

Summary:

When using padding="same" for a conv with even kernels, torch.export creates an explicit pad node, leading to a dq -> pad -> conv chain, which is not recognized, so conv ends up undelegated. The ReLU ends up in its own partition with a quantize. XNNPACK does not support this, resulting in xnn_status_unsupported_parameter.

This PR fixes this, allowing for full delegation to XNNPACK in this case, by pulling the zero-valued spatial pad into the conv's partition (ConvConfig._get_act_deps) so both delegate together: for fp32 the pad lowers directly as an XNNStaticConstantPad. For quantized graphs the pad is created by to_edge decomposition after the quantizer runs, so it arrives as dq -> pad -> conv with no quantize on its output and would serialize as fp32 (the conv would then reject its unquantized activation). InsertPadQDQPass inserts an implicit quantize -> dequantize after the pad, reusing the feeding dequant's params (a zero pad preserves quantization), so it lowers as a quantized static pad and the conv sees a proper dequantized activation.

Note: This results in full delegation, an improvement over the existing runtime error (or portable fallback as naive fix), but the pad is executed as a separate op and results in overhead.

Differential Revision: D109871964

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/20553

• 📄 Preview Python docs built from this PR

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

❌ 2 New Failures, 2 Unrelated Failures

As of commit 0d1649d with merge base b1ef9a5 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 1887e4279ae60bf62a978c436dd17a5795ad7d0255b762a5060942dc93261efb /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 5b9682c208ecc7acd450ea6e8659113b95c50a92ca0328b72746259ef6c8c613 /exec failed with exit code 1

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-models-linux-basic (vit, portable, cmake, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

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

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

[meta-codesync]

@JakeStevens has exported this pull request. If you are a Meta employee, you can view the originating Diff in D109871964.

[digantdesai]

can we fuse it inside the preprocess for xnnpack or we have to run pad + conv in the XNNPACK graph? I am asking because if we can fuse it we might as well write that pass instead.

[JakeStevens]

We can fuse, I have some work in that direction, was going to publish as a quick follow up since there is an external contributor with the 1d work and the change is slightly larger so preferred to do it once these both land.