Use a pass-through for gemm

[kshyatt]

This will help us use the new support for generic GPUArray strided views in a way that bypasses some really awful ambiguity warnings.

[github-actions]

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[lkdvos]

This doesn't fully fix the issue I think, that code path shouldn't ever be reached by the GPU arrays since it is guarded by an isblasmatrix call that checks pointer(A) isa Ptr.

I think this really needs a more proper rewrite that dispatches to a gemm function that then indeed can determine the proper driver.
Note also that the current fallback is using the Strided machinery to manually write out the kernel, which is actually equivalent to what the generic_matmatmul! function does anyways

[kshyatt]

pointer(A) isa Ptr is true for ROCArrays, so this code path is definitely reached by GPUArrays because it was erroring

[kshyatt]

This doesn't fully fix the issue I think

It seems to have unblocked the v1 AMD stuff on TO 🤷 . But if someone wants to make a higher performance version, go ahead. The rocBLAS gemm doesn't work well if the stride in the first dimension isn't 1, I think.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ext/StridedGPUArraysExt.jl	0.00%	2 Missing ⚠️
src/linalg.jl	0.00%	2 Missing ⚠️

Files with missing lines	Coverage Δ
ext/StridedGPUArraysExt.jl	44.44% <0.00%> (-1.46%)	⬇️
src/linalg.jl	21.87% <0.00%> (-0.24%)	⬇️

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[lkdvos]

Would it then not make more sense to fix the isblasmatrix implementation? That at least treats CUDA and AMD equally then.

[kshyatt]

So I think the CUDA one doesn't ever touch this because the result of pointer(A) there is a CuPtr, NOT a Ptr 🙃 . Not sure about Metal?

[lkdvos]

Yes, exactly, I think my argument is to either:
A. Make AMD also not touch this so it is treated the same as the other backends
B. Make every single one either dispatch to gemm if possible, and if not use the Strided implementation, similar to how the current CPU version works.