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coopvec-transpose-without-feature-check ​

Status: stub. The full-length analysis is queued for a v1.0.x patch release per ADR 0018, section 5, criterion #6. The companion rule page at docs/rules/coopvec-transpose-without-feature-check.md contains the canonical detection logic + GPU reasoning.

TL;DR ​

The transpose path lets the application swap the matrix's effective row/column orientation at the matmul site without re-uploading the data. On NVIDIA Ada Lovelace, the tensor cores expose hardware transpose as a free-rate option in the inference path; on AMD RDNA 3/4 WMMA, transpose support is gated behind a driver feature flag because the WMMA hardware lacks the on-the-fly swizzle and the driver emulates it via a software path; on Intel Xe-HPG XMX engines, transpose is supported but the cost varies by component type. The runtime exposes all of this through a single tier value: if the device is tier 0 or below the per-IHV transpose tier threshold, the transpose call fails.

What the rule fires on ​

A cooperative-vector matrix-multiply call whose transposed flag is true (MATRIX_FLAG_TRANSPOSED set) without a corresponding application-side feature check on D3D12_FEATURE_DATA_D3D12_OPTIONS18.CooperativeVectorTier. The SM 6.9 cooperative-vector spec marks the transpose path as conditionally supported: tier 1 implementations may not honour it, and a runtime call with transpose set on an unsupporting device fails. The rule surfaces every transpose use so the developer can confirm the tier check is in place.

See the What it detects section of the rule page for the full pattern definition.

Why it matters ​

The full GPU-mechanism analysis lives in the Why it matters on a GPU section of the companion rule page.

Examples ​

The bad / good code snippets are kept canonical on the rule page; see coopvec-transpose-without-feature-check.md -> Examples.

See also ​

This is a v1.0-ship stub. Full analysis pending; track issue link TBD.

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