Backport 7fdf608 to release/18.x

[mbrkusanin]

/cherry-pick 7fdf608

This feature took a bit longer then expected in review, so it was not merged in time.
Would it be possible to include it in llvm 18? It is one of the last pieces of AMDGPU GFX12 subtarget.

PR: #77795

[mbrkusanin]

In order to avoid conflict with 149ed9d it might be easier to port both, but we do not strictly need it.

[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Mirko Brkušanin (mbrkusanin)

/cherry-pick 7fdf608

This feature took a bit longer then expected in review, so it was not merged in time.
Would it be possible to include it in llvm 18? It is one of the last pieces of AMDGPU GFX12 subtarget.

PR: #77795

[jayfoad]

/cherry-pick 7fdf608

[github-actions]

Failed to cherry-pick: 7fdf608

https://github.com/llvm/llvm-project/actions/runs/7655681158

Please manually backport the fix and push it to your github fork. Once this is done, please add a comment like this:

/branch <user>/<repo>/<branch>

[mbrkusanin]

/branch users/mbrkusanin/gfx12-wmma-swmmac-backport

[github-actions]

Failed to create pull request for gfx12-wmma-swmmac-backport https://github.com/llvm/llvm-project/actions/runs/7656154191

[mbrkusanin]

/branch mbrkusanin/llvm-project/gfx12-wmma-swmmac-port