[llvm] [LiveRegUnits] Enhanced the register liveness check (PR #66061)

[Matt Arsenault via llvm-commits]

================
@@ -112,13 +112,13 @@ class LiveRegUnits {
   /// The regmask has the same format as the one in the RegMask machine operand.
   void addRegsInMask(const uint32_t *RegMask);
 
-  /// Returns true if no part of physical register \p Reg is live.
-  bool available(MCPhysReg Reg) const {
----------------
arsenm wrote:

Just keep the available implementation in the header, it's trivia

https://github.com/llvm/llvm-project/pull/66061