[llvm] [AArch64][NFC] Switch to LiveRegUnits (PR #87313)

[via llvm-commits]

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@@ -197,6 +197,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/LivePhysRegs.h"
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AtariDreams wrote:

> Can you explain why? I don't see any other uses of `LivePhysRegs` in this file. What is it relying on?

computeLiveIns method.

https://github.com/llvm/llvm-project/pull/87313