[llvm] [Thumb] Resolve FIXME: We can trust live-in information from successor blocks now (PR #84111)

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AtariDreams wrote:

Here is the file I tested:
[oggenc.txt](https://github.com/llvm/llvm-project/files/14894270/oggenc.txt)


https://github.com/llvm/llvm-project/pull/84111