[HLSL] Add LinAlg OuterProduct and VectorAccumulate coverage

[JoeCitizen]

Summary

• add capability-gated non-uniform Thread OuterProduct coverage for F16 8x16 and F32 4x8, while retaining and activating the existing F16 16x16 case
• accumulate in DXIL OuterProductOptimal layout and use the preview D3D12 matrix-conversion API for tight RowMajor host readback, with exact checked CPU expectations
• migrate the existing F16 length-four VectorAccumulate case to the shared harness and add F16/F32 length-eight cases with non-zero destinations and checked host multiplication/addition oracles
• replace the released-SDK OuterProduct skip with SDK-neutral preview ABI mirrors, validated against the preview headers

The shader and host APIs intentionally use their respective enum values for OuterProductOptimal: DXIL layout value 4 and D3D12 conversion layout value 3.

Validation

• built the Release ExecHLSLTests target
• compiled both changed implementation units against the preview D3D12 headers, activating ABI size, offset and enum assertions
• ran all 3 OuterProduct methods on public preview WARP with the temporary DIRECT-list compatibility workaround: 3 passed
• ran all 3 VectorAccumulate methods on a disposable WARP build corrected for the current DXIL operand order: 3 passed
• ran the complete 60-case LinAlg selection with the compatible local runtime: 57 passed, the unchanged FP8 and ColumnMajor capability cases skipped, and only the already-documented mandatory native-F32/SInt8 MatVec WARP defect failed
• inspected emitted DXIL for Thread scope, Accumulator use, non-uniform shapes, layout value 4 and handle-first VectorAccumulate operands
• clang-format 17.0.1, git diff --check and a focused correctness review pass

Runtime compatibility notes

Public preview WARP currently decodes VectorAccumulate using the obsolete vector-first operand order, while current DXC emits the specified handle-first order. Agility SDK 1.721 also rejects ConvertLinearAlgebraMatrix on a compute command list; the local OuterProduct run used the documented DIRECT-list compatibility workaround. Neither disposable runtime change is included here, and the tests retain the current compiler/runtime contract rather than hiding either defect.

• after the MatVec review correction was propagated through this stack, the complete 66-method suite on the compatible local runtime reported 61 passed, 0 failed, and 5 capability-backed skips

No physical GPU or packaged-HLK qualification is claimed.

Stack

This draft is stacked on PR #8674, which is stacked on PR #8673, PR #8672, PR #8671, PR #8670, PR #8669, PR #8668, PR #8667, PR #8666, PR #8665 and PR #8662. Until those ancestors land, this diff contains their commits as well. The OuterProduct and VectorAccumulate change itself is commit cb9e552fc.

This remains a draft for named human review. The reviewer should verify the preview ABI mirrors, distinct DXIL/host layout values, capability tuples, OuterProduct conversion/readback path, VectorAccumulate operand contract and independent exact oracles before requesting maintainer review.

Refs #7841
Refs #8563
Refs #8565

Assisted-by: GitHub Copilot