[llvm] [AMDGPU] Ensure all WMMA instructions are marked as convergent (PR #178314)

[Frederik Harwath via llvm-commits]

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frederik-h wrote:

@arsenm just remarked (see https://github.com/llvm/llvm-project/pull/178627#discussion_r2741623829) in a review of my PR #178627 which contains a test based on this one that "-stats" probably won't work in a build without assertions and that it's better to just use autogenerated test checks instead.

https://github.com/llvm/llvm-project/pull/178314