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

[via llvm-commits]

xgxanq wrote:

> Hi! This comment was generated using [fuzz-fill](https://github.com/ROCm/fuzz-fill), a new tool we're building to help improve LLVM test coverage by spotting lines introduced in a PR that don't yet appear to be exercised by the full test suite, including any tests added in this PR.
> 
> Looking at PR head `fba26829efe9`, we found 1 line added or modified here that we couldn't find a test for:
> 
> https://github.com/llvm/llvm-project/blob/fba26829efe9c6d900cd6f7f54bd78bd0a0b6972/llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp#L2830
> 
> It looks like the body of that `if` statement may not be covered by any test. If this makes sense, adding a regression test that validates this line would be great. And if it's already tested and we missed it, we'd love to hear so we can improve the tool. Feel free to give us some feedback on whether this review was useful from your perspective. Thanks!

I have added a  test

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