[llvm] [AMDGPU] Guard RewriteMFMAFormStage recolor against unsafe def/use (PR #217396)

[Lucas Ramirez via llvm-commits]

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lucas-rami wrote:

Ah ok, sounds good.

> The test case we are looking at presently meets the cost criteria, and the failure‑reproducing scenario remains intact.

By "remains intact" do you mean that no promotion to AGPR happens and therefore the code doesn't trigger a machine verifier error?

https://github.com/llvm/llvm-project/pull/217396