[llvm] [BOLT][AArch64] Add minimal support for liveness analysis. (PR #183298)

[Paschalis Mpeis via llvm-commits]

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paschalis-mpeis wrote:

Here, if there's any doubt (ie no callgraph or ind.calls), we have to be conservative.

I may be missing something, but the code below makes `CLOBBERS_NONE` and `CLOBBERS_ALL` behave equivalently.

https://github.com/llvm/llvm-project/pull/183298